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XDIAG E xper t Diagnostic Analysis

of Rod Pumping Systems

Theta Oilfield Services, Inc.1901 E. Lambert Rd. Suite 108La Habra, CA 90631 USATelephone #: (562) 694-3297Fax #: (562) 694-8641www.gotheta.com or www.xspoc.com

Email Addresses:Terry Treiberg - Vice President: [email protected] Support: [email protected]: Christy Kukula - Off. Manager: [email protected]

mailto:terry%40gotheta.com?subject=

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© Theta Oilfield Services, Inc., 2010.All Rights Reserved. This manual may not be reproduced in whole or in part without the written per-mission of Theta Oilfield Services, Inc.

RODSTAR, RODSTAR-D, RODSTAR-V, RODDIAG, XDIAG, CBALANCE, and XTOOLS are trademarks of Theta Oilfield Services, Inc..

Printed in the United States of AmericaFirst Edition, November 2010

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ContentsCustomer Support . . . . . . . . . . . . . . . . . . . v

System Requirements . . . . . . . . . . . . . . . . . . v

introduction . . . . . . . . . . . . . . . . . . . . . . v

Program Features . . . . . . . . . . . . . . . . . . . . vi

1 Software installation 1

1.1 XDIAG Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Questions about Installation . . . . . . . . . . . . . . . . . . . . . . . 1

1.3 Installing the Software Sentinel . . . . . . . . . . . . . . . . . . . . . . 2

1.4 Starting and Setting Up XDIAG . . . . . . . . . . . . . . . . . . . . . . 2

1.4.1 Starting XDIAG . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.4.2 The XDIAG Window . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.4.3 Selecting a Printer . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.4.4 Setting up XDIAG . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.4.5 How the Automatic Batch Run Works . . . . . . . . . . . . . . . . . 17

2 Running XDiAG 19

2.1 XDIAG’s User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.1.1 Using the Keyboard. . . . . . . . . . . . . . . . . . . . . . . . . 20

2.1.2 XDIAG’s Help System . . . . . . . . . . . . . . . . . . . . . . . . 21

2.2 Entering Rod Pumping System Data . . . . . . . . . . . . . . . . . . . . 21

2.2.1 Entering Well Information Data . . . . . . . . . . . . . . . . . . . 23

2.2.2 Entering Production Information. . . . . . . . . . . . . . . . . . . 25

2.2.3 Entering Pump and Tubing Information . . . . . . . . . . . . . . . . 26

2.2.4 Entering Rod String Information . . . . . . . . . . . . . . . . . . . 28

2.2.5 Entering Pumping Unit Data . . . . . . . . . . . . . . . . . . . . . 29

2.2.6 Entering Motor Information . . . . . . . . . . . . . . . . . . . . . 32

2.3 Storing Cases/Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

2.4 Running XDIAG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

2.4.1 Dynamometer Animation . . . . . . . . . . . . . . . . . . . . . . 34

2.4.2 Setting Horizontal and Vertical Lines . . . . . . . . . . . . . . . . . 35

2.4.3 Exporting the Balanced Maximum Counterbalance Moment or Structural Unbalance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

2.5 Printing the Output Report . . . . . . . . . . . . . . . . . . . . . . . . 37

2.6 Loading Data from Disk . . . . . . . . . . . . . . . . . . . . . . . . . . 37

iv | Table of Contents

2.6.1 “Recent Files” Feature . . . . . . . . . . . . . . . . . . . . . . . . 39

3 Expert Diagnostic Analysis 41

3.1 Explanation of XDIAG’s Output . . . . . . . . . . . . . . . . . . . . . . 41

3.2 Diagnosis of System Problems. . . . . . . . . . . . . . . . . . . . . . . 54

3.2.1 Recording Dynamometer Card in the Field . . . . . . . . . . . . . . 54

3.2.2 Downhole Pump Dynamometer Card Interpretation . . . . . . . . . . 58

3.2.3 Avoiding Rod Compression . . . . . . . . . . . . . . . . . . . . . 60

3.2.4 Gearbox Torque and Unit Balancing . . . . . . . . . . . . . . . . . 60

3.2.5 Using XDIAG with RODSTAR-V or XROD . . . . . . . . . . . . . . . . 61

3.2.6 Setting Lines on Downhole Pump Cards . . . . . . . . . . . . . . . . 62

XDIAG | v

Customer Support

If you have any questions or problems using XDI-AG, please call Theta Oilfield Services at (562) 694-3297 or send an email to [email protected].

Before calling Theta Oilfield Services, be ready to explain the problem or what kind of information you need. If you get an error while running XDI-AG, try to reproduce it and make note of the steps you took and the data you entered that caused the error. Make sure you’re at your computer when you call.

System Requirements

Minimum Re-quirements

Recommend-ed

Computer Pro-cessor:

1 GHz 1.6 GHz or faster

Operating System:

Windows 2000 / XP / Vista / 7

Computer Memory:

256 MB 512 MB or more

Screen Resolu-tion:

800 x 600 pixels

1024 x 768 pixels or higher

Available Hard Disk Space:

30 MB

Introduction

XDIAG is a powerful yet easy-to-use rod pump-ing system expert diagnostic analysis tool. XDIAG uses advanced expert system and pattern recogni-tion techniques to detect problems with existing rod pumping systems such as:

♦ bad pumps ♦ overloaded rods ♦ overloaded gearboxes ♦ out of balance units ♦ the cause of low system efficiency ♦ tubing leaks ♦ excessive rod-tubing friction due to paraffin

or scale ♦ incorrect pump spacing that may cause the

pump to hit up or hit down ♦ etc.

XDIAG is the only program of its kind to detect and correct input data errors caused by:

♦ a load cell that is not calibrated properly which may cause a load shift or load span

♦ an incorrect fluid level measurement ♦ an incorrect stroke length ♦ a phase shift of the surface positions in the

dynamometer data ♦ non-kinematic surface positions in the dyna-

mometer data ♦ a dynamometer file with data that is out of

order

In general, XDIAG is a tool that can help you improve efficiency, reduce maintenance and lifting costs, and determine common problems with any part of the pumping system. Also, XDIAG can help you balance pumping units, check system en-ergy consumption, calculate additional production (if you have IPR data) and if your prime mover is correctly sized.

The XDIAG user interface is very easy to use, extremely flexible, and fast. With a single click of

vi | Introduction

the mouse you can access any input screen at any-time. You can change an input by simply clicking on it, and when you have a question, simply press F1 for context sensitive help for any input item. With XDIAG you can take advantage of standard Windows features such as being able to copy the dynamometer or torque plots to the clipboard and then paste then in any other Windows document.

XDIAG is a diagnostic tool for existing wells. It relies on input of actual dynamometer data for its calculations. Please keep in mind that you can only use XDIAG to find problems with existing rod pumping systems. XDIAG is not a design program and so, you should not use it to make predictive runs. To design rod pumping systems or to evaluate the effect of changes on system performance you must use RODSTAR-V/D or XROD computer programs developed by Theta Oilfield Services. RODSTAR-V/D and XROD accurately predict system performance, loading, efficiency, power consumption, and the expected surface dynamom-eter card for any rod pumping system. Also, since RODSTAR-V/D and XROD can read XDIAG files, it saves you time because you do not reen-ter well data into RODSTAR-V/D or XROD. RODSTAR-V/D and XROD can also overlay the measured dynamometer card for easier history matching and troubleshooting.

XDIAG uses the wave equation to model the behavior of the rod string and exact kinematic models to simulate pumping motion. With XDI-AG you can analyze the performance of any rod pumping system regardless of depth, rod material, or pumping unit geometry, including long stroke units like the Rotaflex.

XDIAG works with XBAL so you can enter the existing counterbalance for your unit. You can ei-ther use the toolbar function to “copy” and “paste” the calculated existing counterbalance (maximum counterbalance moment for crank balanced units and structural unbalance for beam balanced units)

or you can open the XBAL file from the pumping unit information window in XDIAG to import the value. After you run XDIAG, you can enter the maximum counterbalance moment or structural unbalance back into XBAL to find out where to move the counterweights in order to balance the pumping unit.

Program Features

XDIAG is a very powerful software program that combines expert system and pattern recognition technology with wave equation diagnostic model-ing. XDIAG uses exact pumping unit kinematics which allows it to analyze rod pumping systems with any pumping unit geometry. XDIAG deter-mines the condition of the pump and calculates fluid level, pump intake pressure, and net pump displacement from the downhole pump card shape.

XDIAG will recall information you entered for a new case if you exit the program in the middle of entering the data. When you open XDIAG again, it will prompt you if you would like to recall the last case you were entering before it closed. This works the same way if the program or the comput-er crashes. If you click “yes” at the prompt, you will be returned to the data entry window you were using before you exited XDIAG, with all the data you had already entered in place.

XDIAG contains data for all common rod-pump-ing equipment: pumping unit types and sizes, rod grades and sizes, tubing sizes etc. Also, XDIAG will warn you of possible problems you can run into in the field such as the need of slimhole couplings or a thin wall pump, what rods fit the tubing size you selected, etc.

XDIAG allows you to take maximum advantage of centralized pump off control systems. It can

XDIAG | vii

analyze hundreds of wells in a 24 hour period, and can create spreadsheet files that present results in an organized way. XDIAG has many capabilities including the following:

♦ Determines pump condition using built in expert knowledge and pattern recognition techniques.

♦ Detects and corrects input data errors such as a load cell that reads too low or too high or an incorrect fluid level.

♦ Lists recommendations for fixing downhole problems, for balancing the unit, etc.

♦ Scores the well based on full pump conditions. This allows you to evaluate the design when any problems with the well are corrected. This avoids the problem of fixing, for example, the rod string design if the pumping unit would be overloaded with a full/pumped off pump.

♦ Prints an expert analysis report that is similar to a report written by a human expert, and plots surface and downhole dynamometer cards and gearbox torque plots. Also, it can print single page output that includes all the quanti-ties calculated by the program, including the dynamometer and torque plots.

♦ Calculates gross pump stroke, pump volumet-ric efficiency, overall system efficiency, peak torque and gearbox loading for existing and balanced conditions, and the counterbalance you need to balance the unit. Also, it shows the difference between balancing the unit for minimum gearbox torque and minimum energy usage.

♦ From the downhole pump it automatically calculates fluid load, fluid level, pump intake pressure, net stroke, fluid production from net stroke, and pump fillage.

♦ When using XDIAG with a centralized pump off control system you can set it up to do the following:

♦ Automatically load an analyze cases with new

dynamometer files. ♦ Start analyzing wells with new dynamometer

data at any time with in a 24 hour period. ♦ Save a concise summary of all runs in an Excel

spreadsheet.

The best way to take advantage of XDIAG diag-nostic capabilities is to use Theta’s XSPOC soft-ware which uses XDIAG to automatically analyze all wells with rod pump controllers that communi-cate with radio. For more information on XSPOC, visit www.gotheta.com. XDIAG can model all common pumping unit geometries. Also, it allows you to enter your own pumping unit dimensions in case your pumping unit is not in the program’s database. Advanced er-ror trapping and warning messages prevent errors and make you aware of special requirements neces-sary for proper system operation.

Advanced Capabilities and Program Limitations

XDIAG has many advanced features that allow you to accurately calculate system performance for any well depth, production rate, or pump condi-tion. Also, you can analyze wells that produce heavy crude or other conditions with increased friction (for deviated wells use XDIAG-D). By cal-culating the minimum stress at the bottom of each rod section, XDIAG shows if the rods experience compression during operation. This is especially important for fiberglass rods that must never be in compression.

XDIAG accurately calculates electricity consump-tion and the monthly energy bill. The results are very accurate because it uses actual motor curves for these calculations. This provides you with data

viii | Introduction

you can use in economic calculations.

XDIAG assumes that the friction between the rods and tubing is equally distributed along the length of the rod string. It also assumes the tubing is full of fluid and the rods are made of homoge-neous material.

XDIAG does not consider the effect of pumping unit moments of inertia on net gearbox torque. This results in a conservative calculation for net gearbox torque and gearbox loading. If your system is equipped with an ultra high slip motor, this will affect the shape of the measured dynamometer card by lowering the peak polished rod load and raising the minimum polished rod load. Since XDIAG uses this actual dynamometer card for its calculations, the effect of the ultra high slip prime mover is partially accounted for. So, the results are close to actual results. Also, XDIAG uses the actual motor efficiency curves to calculate energy consumption and monthly energy bill very accu-rately.

When scoring your well, XDIAG only considers the worst case scenario which is a full pump with the fluid level at the pump. XDIAG cannot score the current condition of the well. The reason for this is the well could become pumped off in the fu-ture, if it isn’t already. If the design is not overload-ed and the fluid level is not at the pump, there is a risk that when the well is pumped off the rods or pumping unit will become overloaded and encoun-ter a failure. This works the same way for pump problems or tubing leaks. If the score was based on these conditions the equipment (pump, plunger, rod string design, etc.) could receive a good score. Then when the problems are fixed the system could run into problems because the conditions changed when the equipment was fixe

Artificial Lift Glossary and Help System

XDIAG takes full advantage of Microsoft Win-dows to bring you context sensitive help and even an electronic Artificial Lift Glossary. This glossary is full of definitions for many specialized terms. This is a very powerful help system that allows you to run the program without a manual. You can access the Artificial Lift Glossary at any time by clicking on the Help tab on the menu bar at the top of XDIAG’s main window. You may find faster concise help by hitting F1 in the input field you have a question with. This will open the help window to the topic on the input field in question and can help you with your problem with one push of a button.

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1 Software Installation

Before you install the program, make sure you have the hardware and software you need to run XDIAG for Windows.

1.1 XDIAG Installation

XDIAG is installed from the Theta Software Suite installation CD that you received. Load the CD into your PC and the installation program should load automatically. After the “Welcome” screen you will have options for whether you are using a Network or Standalone license. After selecting the proper choice, the next screen will prompt you for the programs to install. That screen also has a button that lets you display and print the detailed Installation Guide for your specific installation.

After installing the program, put your original CD away in a safe place. If the Software Installation Suite CD becomes damaged or lost, please call Theta Oilfield Services, Inc. at (562) 694-3297 for a replacement.

1.2 Questions about Installation

The following are some answers to questions you may have about installing XDIAG for Windows.

Do I need to delete earlier versions of XDIAG

before I install?

No. When updating versions of XDIAG, the pro-gram defaults to install to the “C:\Program Files\Theta\XDIAG” directory. If your previous copy of XDIAG is in another directory, you can specify to install over it. It will not replace any of you case files, just the previous version of the program.

The installation defaults to setting “C:\THETA” as the common folder for your case files. Using a common folder is a good idea since several of the Theta Oilfield Services applications that you might have can all share the same case files.

Although a new version of XDIAG can read files created with previous versions, a previous version may not be able to read files created with the latest version of the software.

What happens to files I have created with previ-ous versions of XDIAG?

Nothing. When you install or reinstall XDIAG, only program files are replaced. The latest ver-sion of XDIAG can open older XDIAG files. The saved output will not be available for viewing. This is because changes in the new version of XDIAG might change the output report of the older files. This is due to additions to the pattern recognition database that could improve the results of the older XDIAG files.

2 | Software Installation

If the latest version might get better results that the previous version, does that mean the calcula-tions from the previous version are incorrect?

No. This is simply the nature of advancement of technology. We do the best we can with what we have. If the pattern recognition database improves and changes the results, the changes will be slight changes. Do to the differences we require that you rerun cases to obtain output when updating to a new version of XDIAG.

1.3 Installing the Software Sentinel

Your XDIAG license is validated and protected by a security bitlock called a Sentinel. For stand-alone installations, this is either a USB key or a Parallel Port key that is attached to your PC. For Network Licenses, the key is attached only to the Network License Server. See the Detailed Instal-lation Guide that is available for printing from the Software Installation Suite CD for more informa-tion. XDIAG communicates with the sentinel and although the program can be copied, it will not operate without a sentinel supplied by Theta Oilfield Services, Inc..

If the sentinel is not installed correctly, the pro-gram will warn you that the sentinel does not ap-pear to be connected. If this occurs, make sure the sentinel is properly installed and the connection is not loose. If the sentinel is properly installed but is not working, it may have been damaged. Frequent plugging and unplugging, and static electricity can damage the sentinel. If you think your sentinel is damaged, contact Theta Oilfield Services Inc. to determine if you need a replacement. Do not dis-card the damaged sentinel. Even if it is damaged, you must return the sentinel to Theta Oilfield Services Inc. before a replacement sentinel can be

sent out to you. When XDIAG first starts, it reads and displays the serial number of your sentinel on the opening screen. You will also find the sentinel serial number in the “About XDIAG” window. To open the “About XDIAG” window simply click the “About” command on the “Help” tab of the menu bar.

Theta Oilfield Services, Inc. uses Sentinel “Super-Pro” for software protection. If you use software sentinels from vendors, you may be able to cascade Sentinels as long as the LPT1 port has only one Sentinel “C” on it. If you have one or more Sen-tinel “PRO” and one Sentinel “C”, then plug the Sentinel “C” at the end of the Sentinel PROs or SuperPros. USB type Sentinels can be plugged into any available USB port or hub on the PC.

1.4 Starting and Setting Up XDIAG

1.4.1 Starting XDIAGYou can start XDIAG by double clicking the icon on your desktop. You may also click the XDIAG icon in the Start menu under All Programs/Theta Software/ XDIAG.

1.4.2 The XDIAG WindowThe following figure shows the main XDIAG window that appears when you start the program. XDIAG behaves like any other standard Windows program. You can use the mouse to move and size windows, select text, choose commands from menus and dialog boxes, and complete almost any other task in XDIAG aside from typing text.

The following is an explanation of each part of XDIAG’s main window.

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The control-menu box is in the upper-left corner of each window. The control menu is most use-ful if you use the keyboard. You can use the con-trol menu commands to resize, move, maximize, minimize, and close windows. Also, you can use it to switch to other applications. These are the same functions that are commonly performed with the mouse. Double clicking on the control menu box closes XDIAG.

The title bar shows the name of the application. If more than one window is open, the title bar for each active window is a different intensity the other title bars.

The menu bar lists the available menus. A menu contains a list of commands, or actions, you can carry out with XDIAG.

The toolbar gives you quick access to the menu commands using your mouse. When you first load XDIAG, only some of the toolbar buttons are active. When you enter data or read a file from disk, then the buttons will activate. This helps you move through each input window and enter the necessary data to run XDIAG. The following is an explanation of each toolbar button as they appear from left to right.

New file – Click on this button to refresh XDIAG to begin entering data for a new case. Any unsaved data will be lost.

Open file – Click on this button to read a Theta software file. This includes XDIAG, RODDIAG, RODSTAR-V, and RODSTAR-D. XROD files saved in the non-AI mode format are


similar to RODSTAR-V files and can be opened in XDIAG. RODSTAR-V and RODSTAR-D files will not contain dynamometer data. You must open the dynamometer file after loading one of these files types. Opening RODSTAR file types makes it easier for you to input all the data for an existing well without the need to enter the data for each input window manually.

Save data to disk – Click this button to save the current case to an XDG file. If you run the case the results will be saved in the file and the next time you open the file you can open the re-sults without running it.

Setup – Click here to open XDIAG’s Setup window. The details of the Setup feature will be explained in the next section.

Well information – Click this button to open the Well Information Window. In this window, enter general information about the well such as name, watercut, pressures, pump depth, etc.

Production information – Click this button to open the Production Information Window. In this window, enter the pumping speed and gross production. You can also choose to enter fluid level, pump intake pressure, no fluid level, or IPR information.

Pump and tubing information – Click this button to open the Pump and Tubing Information Window. In this window, enter specific informa-tion about the pump and tubing such as the pump plunger size, tubing size, anchor depth, etc.

Rod string – Click this button to open the Rod String Information Window. In this window, enter the rod string information which includes service factor, and the rod grade, rod diameter, and length of each taper in the rod string.

Pumping unit – Click this button to open

the Pumping Unit Information Window. In this window, select the pumping unit, stroke length, and direction of rotation. You can also enter the counterbalance information.

Motor – Click this button to open the Motor Information Window. In this window, select the type of motor, size of the motor and motor set-tings.

Previous window – Click this button to open the previous input window. The data entry win-dows go in order from left to right on the toolbar. If you are entering data for the pumping unit, clicking this button will change your focus to the Rod String Information Window (it will open the window if it isn’t already open).

Next window - Click this button to open the next input window. The data entry windows go in order from left to right on the toolbar. If you are entering data for the pumping unit, clicking this button will change your focus to the Motor Infor-mation Window (it will open the window if it isn’t already open).

Run – Click this button to run XDIAG’s expert diagnostic calculations.

View output – Click this button to view the output results. This button is only active if there are output results to display. Older files with saved output will not show output results when open-ing in a newer version of XDIAG. This is because improvements in the pattern recognition database may generate better results. You must re-run these cases for output results.

Email – Click this button to send an email to our technical support team. This function will allow you to address the problem and attach up to three files to the email without opening your email client.

XDIAG | 5

Print – Click this button to send the output results to your default printer. You can only print if there is an output report available.

Export counterbalance to XBAL – After running a case, click this button to export the balanced counterbalance moment (crank balanced units) to the Theta “clipboard”. This makes the value available to import into XBAL and balance your unit in just a few clicks. If XDIAG calculated a counterbalance moment to balance for minimum energy as well as minimum torque you will be prompted to chose one of the two to export. For beam balanced units, this function will export the structural unbalance required to balance the unit.

Start automatic analysis mode – Click this button to start XDIAG’s automatic analysis mode. XDIAG will run in the background and will start analyzing wells at the time of the day you specified in Setup.

Help – Click this button at anytime to get context sensitive help. You may also press the F1 key to get context sensitive help.

Visual input – Click this button to open the Visual Input Window. This window make it easy to change a parameter of the case by clicking on the part of the well you wish to change a parameter in. Click the rod string to change a value that pertains to the rod string.

Alphabetical list – Click this button to open the alphabetical list of input parameters. Click on an item in the list to open the input window where the input field for the parameter is located.

The Status Bar is located at the bottom of the main window. It shows useful messages during data entry or when running XDIAG.


The Getting Started window appears in the middle of the main XDIAG window when you open XDIAG. This window shows the most common toolbar icons you need to know to begin using XDIAG. This is especially useful for new users.

1.4.3 Selecting a PrinterXDIAG allows you to select any printer installed on your system. Simply click on File on the menu bar, and then click on Print Setup… to see a list of installed printers as the following figure shows. To select a printer, simply click on the printer name in the list.

1.4.4 Setting up XDIAGClick on the Setup button on the toolbar (fourth button from the left) to open XDIAG’s setup win-dow. You can also open the setup window by click-

ing Tools on the menu bar and clicking XDIAG Setup. This window allows you to specify informa-tion and choose options that usually do not change with each run. The following describes each Setup tab in the order they are presented in XDIAG.

GeneralClick on the “General” tab to specify measurement units and also to select whether to have XDIAG display the visual input window by default.

For measurement units you can select English, Canadian, or Metric/SI. English units are mainly used in the USA and South America. If you select this option XDIAG will ask for pump depth in feet, production rate in BFPD, plunger and rod diameters in inches, etc. The “Canadian” option provides you with the common mix of English and Metric units used in Canada. The “Metric/SI”

XDIAG | 7

option will change the input units to Metric units. In any measurement unit setting you can press the F2 key to convert from English to Metric and vice versa. This works for numeric input fields only. When you press F2 to convert units, the back-ground of the input field changes color (from cyan to green).

Batch ModeClick the Batch Mode tab to adjust the batch run capabilities. This affects the manual and automatic batch mode runs. The top portion of this window allows you to select whether you want XDIAG to print results of each case it runs in batch, to create a summary spreadsheet file, to run the cases using your setup options or the setup options saved on the file, or to rerun cases that contain saved output. The middle section of the window contains options for spreadsheet file formats. The bottom section contains options for the automatic batch mode.

General batch mode optionsIf you check the Make printouts check box, XDIAG will print the output report for each case in the batch.

If you check the Create spreadsheet file check box, XDIAG will summarize the results of all the files you run in batch in a, Excel spreadsheet (xls file format).

If you check the View spreadsheet file check box, XDIAG will open Excel and display the spread-sheet created in the batch run.

If you check the Don’t re-run cases with saved output checkbox, XDIAG will skip case files that have saved output from previous runs. When you run XDIAG in batch mode, XDIAG resaves the files, which saves the output results into the XDG files. This feature is useful if you would like

to create spreadsheet files using different spread-sheet formats. XDIAG will not rerun each case and this speeds up the process of creating multiple spreadsheets for a given batch run. For example, let us assume there are two users (John and Paul) who use XDIAG and they each have their pre-ferred spreadsheet formats. John can run 20 cases in batch mode and create a spreadsheet that sum-marizes the batch run as he prefers. Since John ran the cases, the 20 XDG files contain recent results saved to the files. When Paul runs the same cases in batch, he checks the Don’t re-run cases with saved output option to save time. XDIAG will compile the spreadsheet without re-running each case and this will execute quickly because XDIAG only has to extract the saved results to create the spreadsheet file.

If you check the Update file with Setup’s infor-mation, the batch mode runs will use the setup options in setup, not the setup information in the files. These setup options will replace the options in the files because batch mode runs resaves the files. If you check the Update the Setup with file’s information the setup will be updated with the information on the files that are in the batch mode run. We recommend saving a file with your preferred setup information in case you use this feature and change your settings and you wish to change them back. You can simply use that file to change setup to your preferred settings

Spreadsheet batch mode optionsThis section displays a list of the spreadsheet for-mats you created. If you have not created any for-mats then the only format available is the Default format. Click on the “+” button to create a new spreadsheet format. Select and existing format and click the “pencil” icon to modify the format. Select an existing format and click on the “X” button to delete the format from the list. The following im-age shows the window you will see when creating or modifying a spreadsheet format.


On the left side of this window is a list of variables in the order they will appear in the spreadsheet. On the right side you see an alphabetical list of all other variables that are available and can be added to the spreadsheet. You can drag and drop the variables from one list to the other or you can use the command buttons located between the two lists. To add a value to the spreadsheet you must highlight a variable from each list, and then click either Add Before or Add After. Clicking Add Before button will add the available variable to the spreadsheet list right above the highlighted vari-able on the left. Clicking the Add After button will add the available variable to the spreadsheet list right below the highlighted variable on the left. You can also change the order of the variable already in the spreadsheet list by using the Move Up and Move Down buttons. Highlight the vari-able on the left and click the Move Up or Move Down button to move it up or down in the list. To include the rod string design in the spreadsheet, simply check the Include rod string in spread-sheet checkbox. To name the spreadsheet format, enter the name in the input box on the bottom right of the window labeled “Name of Format”.

Automatic batch mode optionsIn this section of the batch mode options win-dow you can set the time at which you would like

XDIAG to make the batch run and specify the di-rectories of the files XDIAG will use in the batch run. The three directories you need to specify are for the XDIAG files, dynamometer files, and where to save the Excel files. Details about how the automatic batch mode works are in the next section (1.4.5).

DefaultsThe Defaults allows you to initialize inputs for new cases such as electricity cost, plunger size, ser-vice factor, run time, etc. This Setup page, shown in the following figure, shows a list box containing all the defaults you can set. As you select the de-faults item from the list the input field will change accordingly. The following is a list of the default items you can set using this feature:

1. Casing pressure2. Company name3. Electricity cost4. Folder for Open/Save files5. Folder for XBAL/CBALANCE files6. Folder for T1 Dynamometer files7. Folder for Lufkin Automation Dynamometer

files

XDIAG | 9

8. Folder for Import files9. Folder for PDF files10. Include buoyancy effects11. IPR correlation12. Most common pumping unit type13. Motor type14. Oil gravity15. Plunger size16. Pump type17. Pumping speed18. Rod-tubing friction19. Run time20. Second company name21. Second company telephone number22. Steel rod service factor23. Stuffing box friction24. Tubing pressure25. Tubing size26. User name27. Water cut

28. Water specific gravity

Output OptionsThis Setup option gives you more control over what appears on XDIAG’s output report. You can select exactly which parts of the output will be displayed and available to print. You can choose from the expert diagnostic report, scoring page, one-page calculations report, inflow performance (IPR) chart, and separate dynamometer and torque plots. You can also remove the dynamometer cards and torque plots from the one-page calculations report. To help you visualize exactly what will be displayed, XDIAG shows a miniature representa-tion of each page you have chosen. The preview changes dynamically as you select the pages you would like in the report.

Pumping Unit OptionsCustomize Pumping Unit ListThe Customize Pumping Unit List tab, under Pumping Unit Options, allows you to customize the list of pumping units that XDIAG displays on the Pumping Unit Information Window. This makes it easier to locate your pumping unit. For


example, if you only have 12 different sizes of Lufkin Conventional units, 10 different sizes of Mark II units, and 14 different sizes of Ameri-can Conventional units, you can set up XDIAG to show only these units when you are selecting a pumping unit. The following explains how to customize the pumping unit list.

1. From the Setup Window, click the Pumping Unit List tab under Pumping Unit Options tab.

2. Click the arrow on the Manufacturer drop-down and select the manufacturer list you would like to customize. All units that are not already in the custom list will appear in the list box on the right of the window.

3. Add units to the custom list by dragging them from the available list on the right to the cus-tom list on the left. You can also select the unit in the available list and click the Add button to add the unit to the custom list or select the unit in the custom list and click the Remove button to remove it from the custom list.

4. After you add your units to the custom unit list click OK to save your changes.

To make sure you select the correct unit to add to

your custom list, highlight it by clicking it in the list box and observe the Name/API and Other fields on the bottom of the screen. These fields may contain additional information about the pumping unit to correctly identify the pumping unit. This is especially useful for manufacturers (for example: American Conventional) who have more than one unit with the same designation but different crank types. In such a case, the Other field shows the crank type of other information that helps identify the pumping unit.

This is not the only way to customize the pumping unit database. As discussed in the next chapter, you can also select a unit you want to add to the customized pumping unit list by first selecting it from the full database and then checking the Use custom pumping unit list check box. When you check the check box XDIAG will ask if you would like to add the selected unit to your custom unit database. Click yes to add the unit to your custom database.

Measured Pumping Unit ListXDIAG allows you to enter data for pumping units that are not in XDIAG’s main database. If you have the dimensions you need for these units, you can enter them here to use them in XDIAG

XDIAG | 11

(once you entered them in XDIAG they can be transferred to other Theta programs such as ROD-STAR and XROD: when you save an XDIAG file with a measured pumping unit then open that file in another program, you will be asked if you would like to add that measured unit to the programs measured pumping unit list). The following ex-plains how to add a measured unit to XDIAG.

1. Click on the Setup icon on the toolbar, and click on the Pumping Unit Options tab then click on Measured Pumping Unit List tab.

2. To enter data for a new pumping unit click the “+” button.

3. Enter the pumping unit data for your pumping unit.

4. To save your pumping unit to the measured database, click OK.

The measured pumping unit will be under “Mea-sured Pumping Units” when selecting the manu-facturer on the Pumping Unit Information Win-

dow.

If you need help with the input window click the help button. To get help with a pumping unit dimension hit the F1 key while the cursor is in the input field. The help topic for that input field will open automatically.

To modify the data of a measured unit, select the pumping unit and click the “pencil” icon. To delete a unit from the measured unit database, select the unit and click the “X” button.

Measured Pumping Unit DimensionsThe data you must enter consists of geometric dimensions as defined in the API 11E publication. You can get these dimensions from the pump-ing unit manufacturer or measure them yourself. For old units without an API designation on their nameplate, you may be able to put together an equivalent API designation. Look at the gearbox nameplate for the gearbox rating. Measure the


stroke length, and try to decipher additional infor-mation from the unit’s nameplate for the structure rating and structural unbalance. If the nameplate is legible then write down the unit’s serial number or order number. If the unit’s manufacturer is still in business, you may be able to get the data you need from them using the serial number or order number. For help in locating dimensional data for pumping units not in the database call Theta Oil-field Services Inc.

XDIAG allows you to enter data for Conventional, Mark II, Air-balanced, Enhanced Geometry, long stroke, Hydraulic, and Low Profile Belted units. When you enter your own pumping unit dimensions, XDIAG calculates and displays the stroke length based on the dimensions you enter. For all pumping unit types you must first enter the name of the manufacturer, the unit name or model number, the gearbox rating in thousands of inch pounds (excluding hydraulic units), the structure rating in hundreds of pounds, and the maximum stroke length in inches. From these numbers XDIAG puts together the API pumping unit designation. The API pumping unit designa-tion is a standard way of describing the size and capacity of the pumping units. The hydraulic units are given a unit designation because there is not gearbox rating. The following is an example of an API designation:

C-228-246-100

The “C” means this is a conventional unit. The “228” describes the gearbox rating (228,000 in-lbs). The “246” describes the structure rat-ing (24,600 lbs). This means to avoid overloading the unit the maximum polished rod load cannot exceed 24,600 lbs. The “100” describes the stroke length (100 inches). Other unit types have the fol-lowing designation:

♦ C = Conventional or Enhanced Geometry

♦ B = Beam balanced geometry ♦ M = Mark II geometry ♦ A = Air-balanced geometry ♦ R = Rotaflex or long stoke geometry ♦ LP = Low profile belted geometry ♦ H = Hydraulic geometry

Structural unbalanceStructural unbalance is a term used for pumping units with a walking beam. It is defined in the API 11E as the force needed at the polished rod (parallel to the polished rod) to hold the walking beam in the horizontal position while the pitman arms are disconnected from the crank pins. This force is positive when the force is acting down and negative when acting up. See the figure for a visual representation of structural unbalance.

Structural unbalance for conventional units can be either positive or negative. Mark II units always have a negative structural unbalance because their geometry places the saddle bearing on the back of the walking beam. This eliminates the possibility of balancing the walking beam on the saddle bear-ing. The walking beam will always want to rotate to that the horsehead rests on the ground. The structural unbalance will be filled in with the value that is in the database. You can manually change it if you would like. When you enter a custom unit in Setup, if you do not know the structural unbalance for the unit you are analyzing then enter zero. In most cases the structural unbalance will not affect the results significantly.

XDIAG | 13

Definition of crank offset angleThe crank offset angle (or crank phase angle) is the angle between the crank pin bearing and the coun-terweight arm. The figure shows the crank offset angle is defined.

XDIAG requires a positive crank offset angle for Mark II units and a negative one for enhanced ge-ometry units such as Torqmaster, Lufkin Reverse Mark, or American Producer II. For conventional units the crank offset angle is zero. For belted low profile units the crank offset is typically entered as zero. This is because XDIAG analyzes the units beginning at the bottom of the stroke. Belted low profile units are typically designed in such a way that at the bottom of the stroke the counterweight arm is directly vertical pointed upwards. With this orientation, entering a zero for crank offset angle will result in correct calculations.

The following explains the rest of the required unit geometry to add units to XDIAG for each unit type.

Conventional and enhanced pumping unit dataFor conventional and enhanced units you must en-ter unit dimensions R, A, C, I, P, and K in inches, the structural unbalance in pounds, and the crank offset angle in degrees. The crank offset angle is negative for enhanced geometry units. The follow-ing explains each dimension with respect to the pumping unit.

♦ R – Radius of the crank for each crank hole measured from the center of the slow-speed shaft to the center of the crank-pin in inches.

♦ A – Distance from the centerline of the saddle bearing to the centerline of the polished rod in


inches. ♦ C – Distance from the centerline of the saddle

bearing to the centerline of the equalizer bear-ing in inches.

♦ I – Horizontal distance from the centerline of the saddle bearing to the centerline of the crankshaft (slow-speed shaft) in inches.

♦ P – Effective length of the pitman arm (from the center of the equalizer bearing to the center of the crank-pin bearing) in inches.

♦ K – Distance from the center of the crankshaft to the center of the saddle bearing in inches. Some manufactures will supply G and H di-mensions instead of the K dimension.

♦ H – Height from the center of the saddle bear-ing to the bottom of the base beams in inches.

♦ G – Height from the center of the crankshaft to the bottom of the base beams in inches.

You can find the K dimension using the G, H, and I dimensions in the following equation:

Beam balanced pumping unit dataBeam balanced units require the same dimensions as conventional units. The major difference be-tween beam balanced units and conventional units is beam balanced units carry the counterweights on the walking beam instead of the cranks, hence

the name beam balanced. This requires the units to have elongated walking beams. The E dimen-sion is the distance from the back end of the beam to the center of the equalizer bearing. This di-mension is not required to enter a beam balanced unit to XDIAG. XDIAG does require the crank maximum counterbalance moment (in thousands of inch pounds). This allows XDIAG to accurately calculate the required counterbalance while taking into account the counterbalance obtained from the cranks.

Mark II pumping unit dataMark II unit entry also requires pumping unit dimensions R, A, C, I, P, and K in inches, the structural unbalance in pounds, and the crank offset angle in degrees. The crank offset angle for Mark II units is positive. The following explains each dimension with respect to the pumping unit.


♦ A – Distance from the center of the Sampson Post bearing to the centerline of the polished rod in inches.

♦ C – Distance from the centerline of the Samp-son Post bearing to the center of the equalizer bearing (or cross yoke) in inches.

♦ I – Horizontal distance between the centerline of the Sampson Post bearing and the centerline of the crankshaft (slow-speed shaft) in inches.

♦ P – Effective length of the pitman in inches (measured from the center of the equalizer bearing or cross yoke to the center of the crank-pin bearing).

♦ K – Distance from the center of the crankshaft to the center of the Sampson Post bearing in inches.

XDIAG | 15

Air-balanced pumping unit dataAir-balanced unit entry also requires pumping unit dimensions R, A, C, I, P, and K in inches. In addition, you must enter pumping unit dimensions M, S, and V0. The figure displays most of the data required for entering air-balanced units. The fol-lowing explains each dimension with respect to the pumping unit.


♦ A – Distance from the center of the Sampson Post bearing to the centerline of the polished rod in inches.

♦ C – Distance from the centerline of the Samp-son Post bearing to the center of the equalizer bearing in inches.

♦ I – Horizontal distance between the centerline of the Sampson Post bearing and the centerline of the crankshaft (slow-speed shaft) in inches.

♦ P – Effective length of the pitman in inches (measured from the center of the equalizer bearing to the center of the crank-pin bearing).

♦ K – Distance from the center of the crankshaft to the center of the Sampson Post bearing in

inches. ♦ M – Geometry constant in inches squared. M

is the distance from the Sampson Post bearing to the air tank bearing (distance X) multiplied by the area of the piston in the air cylinder divided by the A dimension.

Ap refers to the area of the air cylinder piston in square inches.

♦ S – Pressure in the air cylinder required to off-set the weight of the walking beam, horsehead, equalizer, pitman arms, etc. in psig.

♦ V0 – Minimum air volume in the air tank be-tween the plunger and cylinder at the bottom of the stroke in cubic inches.

Long stroke pumping unit dataLong stroke pumping unit entry requires the sprocket diameter (dimension D), the centerline distance between the top and bottom sprockets (dimension C), the pitman arm length (dimension P) if one exists, and the top drum diameter ratio (usually 1).


You can use this geometry to model other non-beam unit types with long slow strokes. You can do this by entering data that will produce the required stroke length. The stroke length can be calculated using the following equation:

Stroke = C + D

For example, to simulate a long stroke unit with a stroke length of 200 inches, you can enter a sprocket diameter (D) of 20 inches and a center-line distance of 180 inches. This technique can be used as long as the unit’s upstroke and downstroke velocities are approximately equal.

Hydraulic pumping unit dataHydraulic pumping unit entry only requires the structural rating and the maximum stroke length. All calculations pertaining to the gearbox are not performed on hydraulic units. Hydraulic unit types allow you to adjust the stroke length when you select the unit in the pumping unit information window. For example, if you select a unit with a maximum stroke length of 200 inches but the unit had been adjusted to a 165 inch stroke, you can enter 165 inches when running the case so that XDIAG will analyze the actual conditions.

The unit designation generated for hydraulic units is not an API standard. The unit designation is created the same way as other unit types but omit-ting the gearbox rating. For hydraulic unit with a maximum stroke length of 200 inches and a structural rating of 25,000 lbs the unit designation is H-250-200.

Belted low profile pumping unit dataBelted low profile unit entry requires pumping unit dimensions R, D, I, and K in inches. The follow-ing explains the dimensions with respect to the

pumping unit.


♦ D – Diameter of the drum in inches. ♦ I – Horizontal distance between the centerline

of the drum and the centerline of the crank-shaft (slow-speed shaft) in inches.

♦ K – Distance from the center of the crankshaft to the top of the drum in inches.

♦ H – Height from the center of the drum to the bottom of the base beams in inches.

♦ G – Height from the center of the crankshaft to the bottom of the base beams in inches.

You can find the K dimension using the D, G, H, and I dimensions in the following equation:

XDIAG analyzes units beginning with the pol-ished rod at the bottom of the stroke. This orienta-tion usually has the counterweight in the vertical position perpendicular to the base. If this is correct then the crank offset angle (Theta) is 0. If at the bottom of the stroke the counterweights are not in the vertical position then Theta is not equal to zero.

Customize Rod GradesYou can enter custom rod grades for steel rods only. To enter a rod grade that is not in XDIAG’s database do the following:

5. Click on the Custom Rod Grades tab on the Setup window.

XDIAG | 17

6. To add a new sucker rod or sinker bar click on the “+” button. This opens a new window where you enter the following information about the rod, rod grade or manufacturer name, minimum tensile strength in psi for English or kPa for Metric data entry, and stress analysis method. Also, there is a check box on the bottom of the window to identify the rod as a sinker bar. This changes the available rod diameters of the custom rod grade. XDIAG follows the API 11B for rod sizes.

7. When you are done entering the information for the rod, click on the OK button to save the custom rod.

After you enter one or more custom rod grades, you can modify or delete any of them by clicking on the rod name and them clicking on the appro-priate option. Once you enter a rod grade to your custom list, it will appear on the same list as the rest of the rod grades that are built into XDIAG.

Expert DiagnosisThis Setup option allows you to specify “expert” input data corrections to be performed by XDAIG. For example, to have XDIAG correct load shifts of 3% or larger, enter a 3 in the input field after you check the check box labeled Correct load shift of at least. This is a powerful option that allows XDIAG to correct bad data so that you can get an accurate analysis without having to re-measure the dynamometer card. Also, you can select to have XDIAG correct a load span shift, an entered fluid level, a measured stroke length that does not

match the calculated stroke length, and correct out of order dynamometer data. You can allow the friction to be entered for each case, allow XDIAG to calculate friction if there is a traveling or stand-ing valve leak detected and set a friction limit. You can also set a target pump intake pressure. If you enter IPR data, XDIAG can use your target pump intake pressure to calculate additional possible production capacity.

1.4.5 How the Automatic Batch Run WorksBefore XDIAG can run in automatic batch mode, you must specify the directories and the time you want to start analyzing the wells. XDIAG will first look at the XDIAG data directory for data files for each well (.xdg files). Then, it will look at the dynamometer file directory for dynamometer files that are newer than the XDIAG files. If a new dynamometer file exists in this directory with the same name as the XDIAG file, then XDIAG will analyze the well. For example, if you have an XDIAG file named “ABC101.xdg” in the XDIAG directory which was saved on December 5, 2009, and a dynamometer file named “ABC101.dyn” in the dynamometer file directory which was saved on December 9, 2009 then XDIAG will analyze the well.

The automatic batch mode option is primarily for use with a centralized pump off control system that can generate the dynamometer files needed. How-ever, as explained in the next chapter, this is not the only batch mode available in XDIAG. If you


do not use centralized pump off control systems or if you want to create new XDIAG files yourself, you can still run XDIAG in batch mode. Simply select to load more than one file from the file menu (you can select multiple files by highlighting all the files in the batch when opening a file). The next chapter will explain this method in more detail.

XDIAG | 19

2 Running XDIAG

To start XDIAG, double click the XDIAG icon on your desktop. After a few seconds you will first see XDIAG’s introductory window then XDIAG’s main window. When XDIAG first loads, only a few of the toolbar buttons are active. This feature helps guide you through the input windows to be sure all the required values are entered. The ac-tive icons include the following: new case, open file, setup, email, automatic batch mode, and help. If you have not set up XDIAG then do so before you begin entering data for a new case (see Chap-ter 1 section 1.4.4 for information on setting up XDIAG). To enter data for a new case, click the first icon on the toolbar (New) or click File on the menu bar and then click New.

2.1 XDIAG’s User Interface

XDIAG has a user friendly interface that simpli-fies and speeds up data entry. The program uses standard Windows features along with other unique features designed to make entering and changing data as easy as possible. Windows fea-tures utilized by XDIAG include the following: menu bar with drop down menus, control box at the top right of the main window, and the ability to resize and move windows.

When selecting an item from the menu, visual clues tell you what will happen next.

♦ An item followed by no markings starts an action. For example, click File and then click New.

♦ An item followed by an ellipsis (…) opens a dialog box or another window. For example, click File and then click Open.

The Visual Input Window and Other Ways to Change DataThe following figure shows XDIAG’s Visual Input

20 | Running XDIAG

Window that makes it easy to locate an input item you wish to change. When you have entered all the required data for a new case, or you have loaded a case from disk, the Visual Input Window will appear if you have it set to open by default. See the General tab in XDIAG’s Setup Window. The Visual Input Window shows an image of a conventional pumping unit system. As you move our mouse over the picture, tool tips appear nam-ing the various parts of the system. Whenever a tool tip is showing, right-click the mouse to see a popup list box of the input variables associated with that part of the system. Left-clicking opens the data entry window associated with the part of the system you clicked.

Another way to change data is to click the Alpha-betical List button at the bottom of the Visual Input Window or on the tool bar. This button will open a list of all input parameters in alphabetical order. Double-click an item in the list or select the item and clock the OK button to open the input window associated with that item.

2.1.1 Using the KeyboardMost of the functions you can access with the mouse, you can also access with the keyboard. For example, to open a file using the mouse, click the Open File button on the toolbar. Using the key-board, first open the File menu, and then select Open to open a file from disk. The quickest way to perform these steps is to use XDIAG’s accelerator keys or shortcuts.

Accelerator KeysTo use accelerator keys to access menus, first press ALT to activate the menu bar, the press the ap-propriate accelerator key. The accelerator key is underlined in the word on the menu. For example, if you press ALT then the F key, the File menu will open. You can also use the arrow keys to select a function after you activate the menu bar by

pressing ALT. For example, follow this sequence to open a file using accelerator keys and the arrow keys: ALT, F, down arrow, and Enter. To close an open menu drop down, press the ESC key. You can also move to other menu drop down while you have on open by pressing the left or right arrow. For example, if you pressed ALT then the F key, press the right arrow to move to and open the Edit menu drop down.

Shortcut KeysShortcut keys give you the fastest access to impor-tant functions. A shortcut can be a single keystroke or keystroke combination (usually two keys). For example, you can use the shortcut key combina-tions for such features as Cut, Copy, Paste, Open File, Save File, etc. There are also keystrokes for insertion point movement and moving from input box to input box in XDIAG’s input windows.

For example, to switch between XDIAG and the Program Manager, press ALT + TAB. This keystroke takes you to the Program Manager but does not quit XDIAG. XDIAG is still running and may be partially visible on the desktop. At this point, you could start another application or return to XDIAG by pressing ALT + TAB until you cycle back to XDIAG in the Program Manager.

Following is a list of the most common keystrokes for XDIAG.

♦ ALT – Activates the menu bar. Arrow keys or accelerator keys select menus and items. The down arrow will open the selected menu.

♦ ALT + F4 – Quits XDIAG and other applica-tions. Also, closes dialog boxes and specialized windows.

♦ CTRL + F4 – Closes the active window. ♦ ALT + Space bar – Opens the application

Control menu.

XDIAG | 21

♦ ALT + “-“ – Opens input window Control menu. Input windows include the Well In-formation Window, Production Information Window, Pump and Tubing Information Window, etc.

♦ Enter – Initiates the selected action. ♦ ESC – Cancels dialog boxes, menus, etc. ♦ ALT + ESC – Cycles through open applica-

tions and icons. ♦ ALT + TAB – Cycles through open applica-

tions. ♦ CTRL + F6 – Cycles through open input

windows. ♦ Home – Moves cursor to the beginning of the

input field or text box. ♦ End – Moves the cursor to the end of the input

field or text box. ♦ F2 – Switches the measurement system from

English to Metric and vice versa for the current input field.

♦ F1 – opens the context sensitive help. The help system will open to the topic related to the input field that the cursor currently occupies.

2.1.2 XDIAG’s Help SystemXDIAG has a powerful help system that provides context sensitive help for every single input item. Also, it allows you to easily locate help on any sub-ject relating to system simulation and diagnostics. It even includes a complete artificial lift glossary that provides instant access to definitions for hun-dreds of artificial lift terms.

Click on the help drop down on the menu bar to see the following options:

♦ Contents – Start page for navigating through the help system.

♦ Index – Allows you to search for topics by keyword.

♦ Search – Allows you to search topic content for specific words or phrases.

♦ About XDIAG – Displays information about your version of XDIAG.

Click on the About XDIAG… option in the help menu dropdown to find XDIAG’s version number. To see information about your system click the System Info… button on the “About XDIAG” window. You can view information such as Win-dows version, operating mode, free system memo-ry, and free resources.

Click on Contents to see a list of items XDIAG can provide help with. For example, to get help with the toolbar, click on Toolbar Options. XDIAG displays a picture of the toolbar. Click on an item in the image for information on that item. To exit help, click on the control-menu box “X” or press ALT + F4. Help saves the window viewing position and size so that when you return it will remain in your preferred orientation.

Click on Help and then click on Glossary to see an alphabetical listing of artificial lift terms. To see the definition of any of the terms in the glossary, click on the term.

2.2 Entering Rod Pumping System Data

When entering data in XDIAG’s input windows, it helps to know the following:

♦ The insert mode is on by default. To toggle the insert mode on and off press the Insert button.

22 | Running XDIAG

♦ To replace the contents of an input box, double click the input field to select all of the content in it and enter the new data to overwrite the old information.

♦ If an input window contains information that is made up of more than one word, double click any word to select it. You can know type a new word to replace that word only.

To enter rod system data into XDIAG for the first time, click on the first toolbar icon or go to the menu bar and click File then click New. This opens the Well Information Window as the next figure shows. This window acts like a standard window and can be moved and resized.

XDIAG’s input windows use the following color scheme to help with data entry:

♦ Yellow – Denotes a required data input field. You must fill in the yellow input fields before you can move on to the next input window.

♦ Cyan – Denotes the active input field. If you press the F2 key to change the measurement units, this color changes to green.

You can move around an input window by clicking input fields with the mouse are using the TAB key. As you press the TAB key, the cursor will jump forward to the next input field. You can also move backward through the input fields by pressing Shift + TAB. Completed input fields will change from yellow to white.

You can get context sensitive help for any input field by pressing the F1 key. Use the context sensi-

XDIAG | 23

tive help as often as possible because the help sys-tem contains important information that will allow you to make better use of XDIAG (this includes assumptions and limitations built into XDIAG).

2.2.1 Entering Well Information DataCompany nameIf you entered a accompany name in Setup, it ap-pears in the Company name field. You eliminate the need to enter your company name each time you create a new case by utilizing the defaults fea-ture in Setup. See section 1.1.4 of this manual for information about the Setup feature of XDIAG.

Well nameThe well name is required because XDIAG uses it to create the default file name when you save the case to disk

DateThe date defaults to the current date on your com-puter. If you load a file and you would like to insert

the current date that is on your computer, click the Today button next to the date input field to over-write the old date. If the date on your computer is incorrect you can manually enter the date.

CommentYou can type up to 100 characters in the comment field. The comment field allows you to enter obser-vations or other useful information about the well.

Source of Dynamometer DataThe source of the dynamometer data drop down list allows you to select either a Theta dynamom-eter file (.DYN), a Lufkin Automation dyna-mometer file (.DAT), a Dynostar file to extract a dynamometer card from it (.DNS), or Automatic Batch Mode where it will locate the dynamometer files when it runs. To change the source of dyna-mometer data, select one of the options above. If you select a file type you will be asked if you would like read in a new file. If you click yes you will see a dialog box to find and open the dynamometer file. You can also read in a new file without chang-ing the source of the file by clicking the Read new

24 | Running XDIAG

file button. After you load a dynamometer file XDIAG will generate a miniature plot of the card shape. If you use an Echometer dynamometer sys-tem, select the “Theta dynamometer file” because the Echometer system files are saved in the Theta format. You can also read a card directly from a Dynostar file by selecting “Import from Dynostar File”. You don’t have to export the card to a .DYN file first. XDIAG has the ability to extract a spe-cific dynamometer card from a Dynostar file. You can open a Lufkin Automation Dynamometer file which has a .DAT extension by selecting “Lufkin Automation Dynamometer File”.

OptionsYou can manage the dynamometer input data using the Options button on the Well Informa-tion Window. These options include adjusting the load cell measurement, detecting and correcting non-kinematic surface positions, and detecting and correcting phase-shifted surface positions. You can set the options to use the configuration in Setup (Expert Diagnosis tab) or select one of the available options. You can have XDIAG us the calculated kinematic positions instead of the measured positions on the dynamometer card and you can manually adjust the position shift and top of stroke. A position phase shift refers to a problem with the position measurements in the dynamom-eter card. If the position recordings have a lag time then there is a shift as the card is generated. Ad-justing position phase adds or subtracts an amount of time which will correct the problem caused by the lag when recording the surface card. There can also be a shift in the card if the top of the stroke was incorrectly set when the card was recorded. Some dynamometer recording equipment requires the user to press a button when the unit is at the top of the stroke. If this is done incorrectly, the adjustment input field can correct the top of stroke shift by adding or subtracting a few inches from the points in the dynamometer card. You can also set XDIAG to not correct or detect such problems.

Run timeThe run time you enter allows XDIAG to ac-curately calculate the production rate and daily energy consumption. If the well is operating throughout the day then the default 24hrs/day ap-plies. Adjusting the run time is generally done for wells that use pump off controllers.

Pump depthPump depth is used to calculate fluid loads and check the rod string depth entered in the Rod String Information Window. If there is a discrep-ancy, you will be informed after you enter the rod string information.

Tubing and Casing PressureThe tubing and casing pressures are used in the IPR calculations. The rest of the required informa-tion for IPR calculations are found in the Produc-tion Information Window.

Stuffing box frictionThe default stuffing box friction is 100 pounds. This friction can be adjusted for tight stuffing box-es. The best way to estimate the stuffing box fric-tion of you well is by performing a history match using a predictive program such as RODSTAR.

Fluid PropertiesThe water cut percentage, along with the oil API gravity, is used to calculate a default specific gravity for the produced fluid. This affects the weight of the fluid on the plunger when running XDIAG’s diagnostic calculations. These values are also used to calculate lifting costs per barrel of oil and to calculate specific gravity of the fluid in the casing-tubing annulus. The fluid specific gravity can be entered manually or XDIAG can use the water cut percentage, water specific gravity, and

XDIAG | 25

the oil API gravity to calculate the fluid specific gravity. This fluid specific calculation is accurate when the produced fluid is liquid. If free gas occurs in the well then you should enter a fluid specific gravity that is less than the calculated fluid specific gravity. Performing a history match is the best way to adjust the fluid specific gravity.

XDIAG assumes that the tubing-casing annulus is full of oil. It calculates the specific gravity of the oil from the API gravity you enter. If you do not agree with this assumption then change the oil API gravity to correspond to the specific gravity you would like simulate in XDIAG. For example, if you want to simulate water in the casing-tubing annulus instead of oil, then enter an API gravity of 10.

2.2.2 Entering Production InformationFluid levelPlease not that when you enter a measured fluid level and you do not select to have XDIAG to correct the fluid level in Setup, XDIAG uses the entered fluid level in its calculations because it assumes that the entered value is accurate. If you want XDIAG to use the fluid level that it calcu-lates from the downhole pump card lines then do not enter a fluid level.

Pump intake pressureUse this production input if the pump intake

pressure has been measured for the well. XDIAG allows pump intake pressures that are 14.7 psi greater than the casing pressure. If the wellbore contains a packer, you must enter a low casing pressure to be able to enter a pump intake pressure lower than the measured casing pressure.

Pumping speed (SPM) and Gross productionXDIAG uses these two variables to detect prob-lems with the well. If the calculates production from the entered SPM does not match the entered production rate then XDIAG knows that some-thing may be wrong with the well. Along with the pattern recognition system, XDIAG can inform you of problems with the well that could reduce the production rate.

Inflow Performance DataThe Production Information Window gives you the capability to calculate additional production rates if you reduce the pump intake pressure. Click the IPR Data button to expand the window to enter inflow performance data.

Required data includes calculation method (cor-relation), depth from surface to middle of perfora-tions, static bottom-hole pressure, and bubble point pressure. You can also enter up to 10 test points. The pressure that corresponds to the production test points can either pump intake pressure or flowing bottom-hole pressure (in the middle of the perforations). If you do not know the value of the

26 | Running XDIAG

bubbling point pressure, but you know you are pro-ducing below the bubble point pressure, then leave the bubble point pressure field blank and check the Producing below bubble point check box. After you enter the last IPR input item, click on the Up-date prod button to allow XDIAG to calculate the maximum oil, water, and fluid production rates. You can also see the IPR plot by clicking the IPR Plot… button. When the IPR plot is displayed, you can move the horizontal line that you see on the plot with the mouse to see the calculated production rate for any bottom-hole pressure. You can print the IPR plot by clicking the Print button at the bottom of the IPR plot window. Click the Close button to return to the IPR input window.

2.2.3 Entering Pump and Tubing InformationTubing sizeSelect the tubing size of your well from the drop down list. The inner and outer diameters of the tubing size will be displayed to the right of the drop down. You can select other in the drop down to input custom tubing dimensions. The tubing in-ner and outer diameter fields become activated and you can enter these measurements for your custom tubing size.

Tubing anchorYou can check the tubing anchor checkbox to enter the tubing anchor depth. XDIAG used this input

XDIAG | 27

as part of the calculation to determine the stretch of free tubing.Include buoyancy effectsUse this checkbox to include the force of the fluid on the rods when calculating the rod string stress loading.

For steel rods we recommend always excluding buoyancy effects. If the bottom minimum stress of bottom sucker rod section is in compression (without buoyancy effects), you must add enough sinker bars to make this number positive to avoid buckling problems. For example, if you are using a three-tapered rod string with 1”, 7/8”, and ¾” on the bottom, check the bottom minimum stress on the ¾” rods. If this number is negative, add sinker bars or sinker rods to make this number positive.

The bottom of the sinker bar section will always be negative (due to the resistance on the plunger as it moves down on the downstroke). This is normal and is not a problem.

For fiberglass & steel rod strings, also do not include buoyancy effects when analyzing the steel section of the taper. Run the case again with buoy-ancy effects to check if the fiberglass rods are in compression.

Rod-tubing friction coefficientYou can enter your own rod-tubing friction fac-tor in this field. If you do not know what to enter have XDIAG calculate the rod-tubing friction coefficient for you. The rod-tubing friction number primarily affects the calculated downhole pump card shape and the gross pump stroke.

If you are analyzing a well with high friction, you may want to use a higher rod-tubing friction coefficient to get a more accurate downhole pump card and sucker rod stress analysis. However, it is better for most cases to allow XDIAG to calculate the friction coefficient for you; if you use a friction factor that is too large, you may get a distorted downhole pump card shape.

Even if the actual friction between rods and tubing is much larger than the calculated friction coef-ficient, the calculated downhole pump card shape will be easy to diagnose. You can remove frictional loads from the actual fluid load on the pump plunger by setting horizontal lines on the calcu-lated downhole pump card. This is explained later in this chapter (setting lines).

28 | Running XDIAG

Plunger size and pump typeXDIAG will use the pump type to inform you if the pump with the selected plunger size will not fit into the tubing of the well. Insert pumps fit inside the tubing, tubing pumps attach to the tubing and are connected with an on-off tool, and large bore pumps are thin walled to allow for even larger plungers. You can select the plunger size from the drop-down list or select other and enter a custom plunger size in the input field next to the drop-down.

2.2.4 Entering Rod String InformationXDIAG can analyze steel (including continuous rods) and fiberglass rods, by performing the appro-priate stress analysis calculations depending on the type of rods you specify.

Number of tapers or segmentsClick the button with the “pound” or “number” symbol to select the number of rod tapers in the string. Once you select the number of tapers, the

empty rows will be created so that you can add the required information for each taper. You can enter up to 10 rod tapers.Rod gradeThis field is populated with a drop –down which contains all rod data (including custom rod data entered in Setup). The rods are separated by type (steel, fiberglass, continuous, and sinker bars).

Rod sizeThe rod sizes follow production information (API and manufacturer information for available rod diameters). There is also a custom rod diameter feature. Select Other from the drop-down and you can enter the rod diameter in the Actual diameter field. After you select a rod diameter for the top taper, simply click the diameter fields for the rest of the tapers and XDIAG will automatically select the next size down to create a common string design. When proceeding to the next input screen, XDIAG will warn you if the selected rod sizes will not fit the selected tubing size or if they require slim-hole couplings.

XDIAG | 29

Actual diameterThis field shows the actual diameter of the rod taper as a decimal. The actual diameter may differ from the selected rod diameter depending on the manufactures specifications.

LengthEnter the length of the rod taper in this input field. Once you enter the length for each taper above the last, XDIAG will automatically enter a rod taper length for the last taper to match the rod string length to the pump depth. You can change this en-try if you wish. XDIAG will run if the rod string is no less than 50ft from the pump depth. XDIAG will not run if the rod string is longer than the pump depth. There are two displays on the bot-tom section of the window which show the pump depth and the rod string length. This makes it easy to enter the correct length and run XDIAG.

Steel rod service factorThe steel rod service factor is used to adjust the rod loading calculations. The service factor enables you to degrade the stress rating of your rods based on corrosive conditions or other reasons that lead to premature rod failures. A service factor between .8 and .9 is recommended in most cases. For wells that produce large amounts of H2S you may want to use a service factor of 0.75 or even 0.7. The smaller the service factor you enter, the stronger (larger diameter or higher stress rating) the rods must be to avoid becoming overloaded. The default service factor in the program is 0.9. If you enter this service factor it means that you do not want to exceed 90% of the calculated maximum allowable stress.

Adding and removing rod sectionsXDIAG allows you to add and remove rod sec-tions from anywhere in the rod string. For exam-ple, if you want to remove a rod section, first click

the rod section and then click the remove button. When you select a rod section, XDIAG outlines the section with a light blue rectangle.

To add a rod section, click a rod section and then click the add button. XDIAG automatically creates a new slot for the new section, moves the other sections below the new section, and increases the number of rod sections by one.

2.2.5 Entering Pumping Unit Data

This input screen handles all pumping unit data entry. You can select a pumping unit from the database that comes built into XDIAG by using the drop down or entering the pumping unit ID and you can select a pumping unit from the list of measured units that you entered into XDIAG yourself through Setup. Once you select a pump-ing unit, you can enter/select all other associated information.

ManufacturerThis drop-down contains all of the available pumping unit manufacturers. If you entered a measured unit using Setup, you can find your cus-tom pumping unit entry by selecting the “(Mea-sured pumping units)” option at the top of the drop-down. Once you select a manufacturer you can select the specific pumping unit from the list box that is populated directly below the manufac-turer drop-down. This list box shows the data that you entered: manufacturer name, API designation, Unit Name, and Other Info.

If your unit is not in the built in database and you do not have the measurements to add the unit in Setup, then use a unit that is close to it. As long as you use the same unit geometry and you select a unit with the same stroke length and gearbox rat-ing, the results should be very close to the results

30 | Running XDIAG

using the actual unit.

If after you enter a pumping unit ID XDIAG displays “The pumping unit ID you entered is not valid” this means that the ID you entered is not recognized. This can happen for two reasons:

♦ You entered the wrong ID such as CL901 instead of CL91.

♦ You have erased the pumping unit file by ac-cident or it has been changed, or the pumping unit files are not in the same directory as the XDIAG.EXE file.

Unit IDEach pumping unit in the built in database is

assigned a unit ID. This feature makes it easy to jump to common pumping units with a short ID entry. If you are maintaining lists of pumping units in your field for analysis, add the pumping unit ID to the lists. Using the pumping unit ID makes it easy to select the pumping unit without the need to first select the manufacturer then finding the exact unit.

Use custom pumping unit list checkboxCheck this checkbox to filter the pumping unit database. Only units that you assign to be in the custom pumping unit list will be displayed in the list box once this checkbox is checked. For in-formation on how to add pumping units to the custom pumping unit list see section 1.4.4 of this manual under Pumping Unit Options. To auto-matically add units to the custom pumping units,

XDIAG | 31

select a unit then check the custom pumping unit list checkbox. XDIAG will ask you if you would like to add the selected unit to the custom pump-ing unit database.

Crank rotationSelect the crank rotation using this drop-down. XDIAG will default to a recommended crank rotation that should give the least gearbox loading. If the unit is one-directional then this feature will be disabled.

CrankholeSelect the crank hole using this drop-down. The measured stroke length is displayed next to the crankhole number. When you select a crankhole, the calculated stroke length is displayed below the drop-down. The crankhole numbers are labeled by number beginning with the closest to the slow-speed shaft. This is because some pumping units have optional cranks that have extra crankholes (such as 4 instead of 3 or 5 instead of 4). This “extra” crankhole is always the farthest crankhole from the slow-speed shaft. If the crankhole on the end of the crank (farthest from the slow-speed shaft) is identified as crankhole number 1, the same pumping unit using crankhole number 1 can have a different stroke lengths depending on which crank is on the unit. By identifying the crankhole closest to the slow-speed shaft as crankhole num-ber 1 we can avoid this confusion.

Structural unbalanceStructural unbalance is a term used for pumping units with a walking beam. It is defined in the API 11E as the force needed at the polished rod (parallel to the polished rod) to hold the walking beam in the horizontal position while the pitman arms are disconnected from the crank pins. This force is positive when the force is acting down and negative when acting up. See the figure for a visual representation of structural unbalance. Structural

unbalance for conventional units can be either positive or negative. Mark II units always have a negative structural unbalance because their geom-etry places the saddle bearing on the back of the walking beam. This eliminates the possibility of balancing the walking beam on the saddle bearing. The walking beam will always want to rotate to that the horsehead rests on the ground. The struc-tural unbalance will be filled in with the value that is in the database. You can manually change it if you would like. When you enter a custom unit in Setup, if you do not know the structural unbalance for the unit you are analyzing then enter zero. In most cases the structural unbalance will not affect the results significantly.

Counterbalance optionsThere are several options available for entering the counterbalance information. Counterbalance infor-mation used in XDIAG changes depending on the type of unit you are analyzing. Conventional units are balanced using a counterbalance moment about the slow speed shaft. Air-balanced units are coun-terbalanced using tank pressure. Beam balanced units are balanced by the structural unbalance. Long-stroke units are balanced by counterbalance weight. If you do not know the existing counter-balance XDIAG will only run the gearbox calcula-tions using the balanced conditions.

For crank balanced units you can enter the existing maximum counterbalance moment, counterbalance effect (moment and angle), import the CBE from the dynamometer file (if it is in the file), or use XBAL to import the existing counterbalance.

For air-balanced units you can enter the existing tank pressure at the bottom of the stroke, counter-balance effect, or import the CBE from the dyna-mometer file (if it is in the file).

For long-stroke and hydraulic units you can enter

32 | Running XDIAG

the counterbalance weight, counterbalance effect, or import the CBE from the dynamometer file (if it is in the file).

2.2.6 Entering Motor Information

XDIAG contains the most common electric mo-tors which allow XDIAG to calculate the lifting cost and warn you of problems that might occur such as small motor size.

Electricity costXDIAG uses the electricity cost to calculated lift-ing cost. XDIAG uses the instantaneous efficiency at many different points throughout the stroke to find electricity consumption. These electricity con-sumption values are then used with the electricity cost to calculate the cost to lift the fluid.Power meter typeSelect detent if you are given no credit for generat-ed power. Select non-detent if you are given credit for generated power. This variable is used to adjust the lifting cost calculation. The generated power will lower the lifting cost if the power meter type is non-detent.

Motor typeSelect the motor type from the drop-down list. The most common electric motors are available. The available motor sizes are populated after a mo-tor size is selected.

Motor sizeOnce the motor type is selected, the available motor sizes are populated in this drop-down list. XDIAG will inform you if the motor size may be too small or too big for the well.

Motor settingMotors such as the Sargent Econo-PacII have different motor settings. If you select one of these motors then the motor setting drop-down will ap-pear. Select the appropriate motor setting from the drop-down list.

2.3 Storing Cases/Files

After you finish entering data, you can save the data to disk by clicking on the quicksave button on the toolbar (diskette icon), or by selecting File from the menu bar and then choosing Save As... This opens a standard Windows dialog box used for storing files. XDIAG will use the first non-blank characters from the Well Name input from the first input window as a default file name. The XDIAG file extension is “.XDG”. We suggest saving a new file if you change something in the case so that you can recover previous input data. If you wish to save over the previous file (use the same name) simply click the quicksave icon on the toolbar to save over the file.

XDIAG’s Permanent Memory FeatureLike all software developed by Theta Oilfield Services, XDIAG has a unique feature that saves

XDIAG | 33

the data you enter automatically as you fill in each input field. You will never lose data if XDIAG or your machine shuts off unintentionally due to a computer crash or loss of power. This works even if you exit the program without saving your data. If any of these scenarios occur, the next time you open XDIAG you will be prompted with the following message: “The previous XDIAG for Windows session ended while data was still being entered. Do you want to continue entering data?” Click Yes and XDIAG will start from where you left off from the last time you ran the program.

2.4 Running XDIAG

The run button on the toolbar will be activated after you enter all the required data to perform diagnostic calculations. Click on the run button to run XDIAG’s diagnostic calculations and receive a complete report. You can also click Run on the menu bar to run XDIAG. If XDIAG detects any problems with the input data you will be prompted after clicking the Run button.

XDIAG will automatically display the output re-port after the calculations are complete. The pages

34 | Running XDIAG

of the report that are displayed can be managed in Setup. See section 1.4.4 in this manual to set up XDIAG.

When the results window opens, you can jump to different plots by use of the buttons on the bottom of the window. You can open the dynamometer plot, torque plot, IPR plot (if IPR data was en-tered) and you can return to the output report by clicking the Report button.

2.4.1 Dynamometer Animation

When the dynamometer plots are displayed (af-ter clicking the Dynamometer button) you can animate the surface and downhole dynamometer

cards to see the stroke at the surface and the pump simultaneously. Click on the play button to see the actual pumping speed at the surface and at the pump. A dot on each card indicates the movement at the surface and at the pump. You can observe the delay between the surface and downhole cards as the stroke is translated through the rod string.

This animation helps you to understand the dy-namics of the pumping system with respect to stretch of the rods, the speed of the plunger versus the speed of the polished rod, and the load fluctua-tions of the pump plunger. This feature allows you to learn and understand more about how the rod pumping systems work. You will be able to “see” different operating characteristics such as under-travel, overtravel, compressive wave reflections of the sinker bars when you have fluid pound with

XDIAG | 35

fiberglass rods, plunger speed versus polished rod speed during fluid pound, effect of overtravel or undertravel on plunger speed, etc. This animation may reveal reasons for the surface card shape with respect to the downhole card shape. The controls at the bottom of the window allow you to “play”, “stop”, or move forward through each time step one frame at a time.

Exporting Dynamometer Card FilesYou may use XDIAG to export surface dynamom-eter card files. XDIAG saves these files in the “Theta dynamometer file” type. There must be data in memory before using this option. If you export a file before running XDIAG, the dynamometer file will be a copy of the imported dynamometer file. After running XDIAG, when you export a dyna-mometer file, you will be asked if you would like to export a modified dynamometer card if any correc-tions were made to the card by XDIAG. The files exported by XDIAG have a “DYN” file extension (for example, ABC#1.DYN).

2.4.2 Setting Horizontal and Vertical Lines

The purpose of setting horizontal lines on the calculated downhole pump dynamometer card is to calculate fluid load, pump intake pressure, and fluid level. The purpose of setting vertical lines on the downhole pump card is to calculate net stroke and production through the pump. Chapter 3 explains the theory behind line setting and the limitations of this method of calculating fluid level and pump intake pressure. This section discusses the mechanics of setting the lines once the down-hole pump card is calculated.

First, please note that you do not have to set lines yourself. XDIAG has the expertise necessary to “decide” when and where to set lines. In some cases XDIAG will not set lines because it is dif-ficult to determine where to set the lines. Although XDIAG sets these lines for you, you may still set

36 | Running XDIAG

the lines yourself if you wish.

To set lines manually, click on the Set Lines button at the bottom of the Output Report Win-dow. This will open a window which displays the downhole dynamometer card with horizontal and vertical lines.

To move a line, move the cursor over the line. The cursor will change shape. Click and hold the left mouse button then drag the line to the desired location. While the line is selected it changes from red to orange. When the line is at the desired location, release the left mouse button. When you release a line it will become red again. As you change the distance between the horizontal lines, you can see the fluid over the pump, fluid level, and pump intake pressure values dynamically change at the bottom of the window.

Follow the same procedure to move the vertical lines to calculate net pump stroke and production through the pump. As you change the distance between the vertical lines, you see the net pump stroke and production values dynamically change at the bottom of the window.

To go back to the line settings made by XDIAG just click the XDIAG settings button under the horizontal line header or vertical line header on the bottom right of the window. If you need help setting lines or if you have questions regarding how and why line setting works, press the F1 key for context sensitive help on the setting lines. After you finish setting lines on the downhole pump card, click on the OK button to go back the Out-put Report Window.

Please note that even though XDIAG allows you to change the line settings, the program does not necessarily use the numbers calculated from your line settings. If your line settings make sense then

XDIAG will use the values calculated from your line settings. However, on the calculated results page of the output report, in the section labeled “Tubing, pump and plunger calculations”, your line settings will be reflected in these calculates results regardless of whether or XDIAG uses them or not.

2.4.3 Exporting the Balanced Maximum Counterbalance Moment or Structural Unbalance

After XDIAG runs, it calculates the balanced maximum counterbalance moment to balance the unit with the existing conditions (structural unbal-ance for beam balanced units). Simple enter the counterbalance data into XBAL and XBAL will calculate where to move the counterweights or to add/remove counterweights to balance the unit. Please note that this will balance the unit for the current conditions. If there is a problem with the well, you should fix the problems before attempt-ing to balance the unit.

Crank balanced unitsAfter XDIAG runs, it calculates the max. CB mo-ment needed to balance the unit for either mini-mum torque or minimum energy consumption. For more information see the Torque Analysis section in Chapter 3.

XDIAG works with XBAL to make data ex-change very easy. To transfer a balanced max CB moment from XDIAG to XBAL, click on the “XBAL” button on the XDIAG toolbar. It shows an arrow and “XBAL” on it indicating that it sends information to XBAL. If XDIAG calculated a balanced max CB moment for minimum torque only, clicking the “XBAL” button will send that value to the “Theta Clipboard” with no other ac-tion required. If XDIAG calculated a balanced max CB moment for minimum energy along with one for minimum torque, you will be prompted

XDIAG | 37

as to which value you would like to send to the “Theta Clipboard”.

The “Theta Clipboard” is a separate file that stores the exported data to be retrieved by Theta soft-ware. It is a single file which means that every time you export a value, the previous value will be overwritten. These values will be saved in this file even after XDIAG is closed.

Beam balanced unitsThe same procedure for crank balanced units applies. XDIAG will use structural unbalance instead of maximum counterbalance moment to balance the unit. This allows XBAL to calculate the amount of counterweight and the position on the beam to balance the unit.

2.5 Printing the Output Report

To print XDIAG’s output, click on the printer icon located on the toolbar. To change what the pro-gram prints, open Setup from the toolbar and then click on the “Output Options” tab. Select the out-put pages you want generated then click OK. Now that you defined the pages in the report, when XDIAG prints the report you will have printed the desired pages.

Once you define the output pages you want in the report, XDIAG will continue to generate this re-port until you change the settings again.

When using the print button on the toolbar, XDIAG will automat-ically print to your default printer.

If you would like to send the report to a different printer, click the print button on the top right of the Output Results Window. This will open a standard Windows printing dialog box. You can then access the printer properties and select the printer like most Windows programs.

2.6 Loading Data from Disk

After you enter and store your input data, you can easily modify it by loading it back in memory. You may need to do this if you want to analyze a new dynamometer card or make an equipment change on the same well.

To load a previously saved file, click on the open file button on the toolbar. Or, you can click on File on the menu bar and then on Open. A standard Windows “open file” dialog box will open. Select the file you wish to load by double clicking on it or selecting the file and clicking the Open button. If there is data in memory from a current case you are building, XDIAG will warn you that loading a file will erase the current data in memory. This alert will help you to avoid accidental loss of input data so you will have a chance to save it.

XDIAG can read all Theta Oilfield Services Inc.

38 | Running XDIAG

file types (RODSTAR-V/D, RODDIAG, and XDIAG). By default, the “open file” dialog box shows the XDIAG files when it opens. To load a different file type, such as a RODDIAG file, click on the drop-down list labeled “Files of type” and select the file type (.rdg for RODDIAG files). This applies a filter to the list of files you see so only RODDIAG files are displayed. To load one of these files, double click the file or select the file and click the Open button. If the file you are look-ing for is not in the list you can change the direc-tory like other standard Windows programs.

When you open predictive program file types, the loaded data will not contain any dynamometer card data. You will have to load a dynamometer

card if you chose to use a RODSTAR file to run XDIAG. Being able to open RODSTAR file types is a quick way to enter the required well data that is shared between the programs. This eliminates the need to re-enter the well name, pump depth, run time, etc.

To locate a file, you can click on the scroll bar next to the file list, or you can press the Page Up or Page Down keys to quickly move through the list. To move to the beginning or the end of the list, press the Home key or End key respectively. If the current directory contains many files, it may be faster to press the first few characters of the file name to find the file you are looking for. For example, if you are looking for a well named

XDIAG | 39

“PR100.xdg” then enter “PR1” and the dialog box will jump to the file that begins with “PR1”. It may be equally beneficial to simply use the first letter of the file name.

2.6.1 “Recent Files” Feature

XDIAG has a feature that makes it easy to re-load a file you recently worked with. Instead of clicking on Open icon on the toolbar, click on the arrow next to it to open a list of recent files used in XDIAG. You can also click on the File menu and click Recent Files to open the recent files list. This list is made up of the last 20 files ran and or saved with XDIAG. Click on a file in the list to load the file.

XDIAG | 41

3 Expert Diagnostic Analysis

XDIAG is a sophisticated diagnostic tool that combines expert knowledge and pattern recogni-tion with state of the art wave equation and pump-ing unit kinematic models. You can use XDIAG to quickly analyze the performance of existing rod pumping systems. XDIAG can simulate any pumping unit geometry and gives accurate diag-nostic results regardless of pump depth, rod string type, or production rate. You must make sure that your input data is accurate to get accurate results from XDIAG. However, because of its sophisticat-ed input data error detection features, XDIAG can even detect and correct common input data errors such as incorrect load cell calibration, incorrectly measured fluid level, wrong stroke length, etc.

XDIAG automates the expert diagnostic analysis of large numbers of rod pumping systems whether they are connected to centralized pump off control systems or not. XDIAG has unique features that have been specifically designed to allow you to ef-fectively use the results of the program. The capa-bility of XDIAG to run in batch mode, creating summary spreadsheet files, makes it easy to man-age the information XDIAG provides to you about your wells.

XDIAG can help you detect almost all surface and downhole system problems which include the fol-lowing: incorrectly sized prime mover, overloaded gearbox, overloaded pumping unit or rod string, worn traveling or standing valve, incomplete pump fillage, low pump efficiency, undertravel, pump hitting up or down, etc. Also, because XDIAG can accurately calculate the prime mover energy consumption, you can use it to help you identify costly or unprofitable wells.

Also, XDIAG can calculate fluid level, pump intake pressure, net stroke, and fluid rate through the pump. For wells with packers, or foamy fluid in the annulus, XDIAG may be the only way to get a pump intake pressure. If you have IPR data, XDIAG can even calculate additional production potential based on your target pump intake pres-sure. Combining these calculations with XDIAG’s scoring capability and expert diagnostic analy-sis report and you can use XDIAG to optimize the well. The following sections explain how to use XDIAG as a diagnostic tool of common rod pumping problems. As you become more familiar with XDIAG you will discover many different ways of using the program to help you identify problems with your rod pumping wells.

3.1 Explanation of XDIAG’s Output

To maximize the benefit of using XDIAG, it is important to understand its output. After XDIAG runs, it displays the expert diagnostic report (including a scoring page to show the areas of the system that need improvement) along with the predicted surface and downhole dynamometer card plots, torque plots, and IPR plots. The expert report created by XDIAG simulates the report a human expert may write about the rod pumping system. In many cases, the expert report is the only part of the output you may want to read. How-ever, XDIAG provides you with a calculations page that summarizes all the important system

42 | Expert Diagnostic Analysis

parameters. Following is a detailed explanation of XDIAG’s output.

Dynamometer and permissible load plotsThese plots show the surface and downhole dy-namometer card plots, and the permissible load diagram. XDIAG uses a permissible load dia-gram that shows if the gearbox or structure of the pumping unit is overloaded or if the mini-mum polished rod load is negative. This is differ-ent than the traditional permissible load diagram which only shows whether the gearbox is overload-ed. This extended permissible load diagram can be made up of several curved lines only, a combina-tion of curved and straight lines, or straight lines only. If the upstroke part of the predicted surface dynamometer card cuts into the curved line of the permissible load diagram, this indicates that the gearbox torque is overloaded at that point. If the

dynamometer card cuts into the straight line sec-tion of the permissible load, this indicates that the structure of the pumping unit is overloaded be-cause the polished to load is larger than the struc-ture rating of the unit.

For the exact numbers of peak net gearbox torque and gearbox loading, look at the torque analysis section of the output results page. The permissible load diagram corresponds to existing conditions if you entered a counterbalance moment. If you do not enter existing counterbalance information then the permissible load diagram corresponds to the balanced condition.

Note: The above discussion about XDIAG’s permissible load diagram refers to beam pumping units and low profile belted units. The permissible load diagram for long stroke units such as Rotaflex

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units will have straight line segments that cor-respond to the gearbox loading or the structural loading. Hydraulic units do not have gearboxes so the permissible load diagram corresponds to the structural loading. Please look at the structure loading and gearbox loading value and percentage for the exact percent unit loading.

In addition to showing whether the gearbox is overloaded, the permissible load diagram also shows how well the pumping unit matches the load requirements of your system. If the predicted polished rod dynamometer card fits nicely in the permissible load envelope, this indicates a good agreement between the pumping unit and the rest of the system. However, if the predicted surface dynamometer card shows a trend that is opposite that the permissible load diagram, this indicates that design changes are necessary to avoid over-loading the pumping unit and to better match it

to the of the system. If the permissible load has a trend that is opposite than the predicted dyna-mometer card, it may indicate that the pumping unit you selected is not the best geometry for this application.

Torque plotsWhen you click on the Torque button on the bottom of the output report window, XDIAG displays the net gearbox torque plots for existing and balanced conditions. If you entered an existing maximum counterbalance moment (crank balanced units) or structural unbalance (beam balanced unit), you may have a torque plot with as many as three curves: one for existing conditions, one for balanced conditions for minimum torque, and one for balanced conditions for minimum energy con-sumption. XDIAG will not display the balancing information for minimum energy if the lifting cost


is close to the lifting cost when balanced for mini-mum torque. If balancing the unit for minimum energy will reduce lifting costs by 1% or more the balancing calculations for minimum energy will be displayed.

The torque plot will also be displayed on bottom of the calculations page by default. You can change this as well as other displayed pages by going to Setup.

IPR plotsWhen you click on the IPR Plot button, XDIAG displays the IPR plot for the well as the figure

shows. Also, if you entered IPR data, the report shows a table of calculated production rates versus pressures.

Set linesClick this button to go to the line setting window where you can change the placement of the vertical and horizontal lines used to calculate fluid level, net pump stroke, and net pump displacement. More details about this feature can be found in section 2.4.2 of this manual.

ReportClick the Report button to go back to the default

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output report display. The first part of the out-put report is the Expert Diagnostic Report Page which has four sections. The Downhole Equip-ment Analysis section shows the condition of the pump and the fluid level determined by XDIAG. The Rod String Analysis section shows if any of the rod sections of the rod string are overloaded and by how much. The Surface Equipment Analy-sis section shows if the gearbox or pumping unit structure is overloaded. The balancing recommen-dations are also in this section. The Input Data Analysis section shoes possible input data errors that were detected by XDIAG and any input data corrections that are made (such as load cell drift correction).

The next page in the output report is the Scoring Page. XDIAG looks at six vital components of the

well to determine if it is a good design. Because XDIAG is a diagnostic tool, the data entered into XDIAG is rarely of an optimized well. The fluid level may be high or pump may be in poor condi-tion. Scoring a well with these conditions will yield incorrect scores. This is because the fluid load may be reduced due to the high fluid level. Imag-ine a well received a good score then the operator changed the speed of the unit to pump off the well. The structural loading will increase as the fluid level drops and there is a possibility of fail-ure due to the increased fluid load. If the operator based his decisions on the scoring of the well with a high fluid level, he may be unaware of this po-tential problem. For this reason XDIAG scores the well for the worst case scenario (full pump with the fluid level at the pump). The score given to the well is for the optimized condition, balanced and pumped off with a full pump in good condition.


The sections scored are as follows: ♦ Balanced Gearbox Loading ♦ Maximum Rod Loading ♦ Structural Loading ♦ System Efficiency ♦ Bottom Minimum Stress ♦ Minimum Polished Rod Loading

Each section will receive reduced scores if they are over loaded or under loaded except for System Efficiency. System Efficiency will only receive a reduced score if it is low. Reduced scores are given to sections that are under loaded because these areas can be optimized to reduce initial costs of the well. You may be able to use a smaller pump jack or rods which will save money when ordering these

components for the well. Each section will display an explanation of the score and how to improve it.

After the Scoring Page, XDIAG shows all the parameters it uses for the calculated results and the results. Following is a detailed explanation of the Input Data and Calculated Results Page.

Input DataAlong the left side of the Input Data and Calculat-ed Results Page you will see the input data for your well. The data is separated into sections to make it easy to read. The top section contains the generic information about the well (run time, SPM, sur-face stroke, fluid level, tubing and casing pressures, gross production, and stuffing box friction). As you move down the page you will see more detailed

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information. The following list shows the detailed sections and the input data in each section:

♦ Fluid Properties• Watercut• Water specific gravity• Oil API gravity• Fluid specific gravity

♦ Motor and power meter• Power meter type• Electricity cost• Motor type• Motor size

♦ Pumping unit• API designation• Crank hole number• Calculated stroke length• Crank rotation• Maximum CB moment (existing)• Structural unbalance• Crank offset angle• The dynamometer file information is in the

bottom part of this section ♦ Tubing and Pump information

• Tubing outer and inner diameter• Plunger size• Tubing anchor depth• Rod-tubing friction• Pump type• Pump depth

♦ Rod string (listed for each rod segment)• Rod diameter• API rod grade• Rod segment length

• Minimal tensile strength

Calculated ResultsAlong the right side of the page you will see the calculated results for your well. These values are separated into sections to make it easy to read. The top section contains generic information about the well (peak and minimum polished rod load, min/peak polished rod load ratio, system efficiency, buoyant rod weight, maximum rod loading, pol-ished rod HP, permissible load HP, polished rod/permissible load HP ratio, unit structure loading, and gearbox loading). As you move down the page you will see more detailed information.

The following list shows the detailed sections and the calculated data in each section:

♦ Required prime mover size for existing condi-tions• Nema D motor• Single/double cycle engine• Multicylinder engine

♦ Torque analysis and electricity consumption (listed for existing, minimum torque, and minimum energy balancing when applicable)• Peak gearbox torque• Gearbox loading• Maximum counterbalance moment (struc-

tural unbalance for beam balanced units)• Counterbalance effect• Daily electricity use• Monthly electric bill• Electricity cost per bbl of fluid• Electricity cost per bbl of oil

♦ Tubing, pump, and plunger calculations• Tubing movement• Gross pump stroke


• Top minimum stress• Bottom minimum stress• Stress calculation method

The following is a detailed explanation of calcu-lated results.

General calculationsPeak and minimum polished rod loadsThese values are single polished rod loads. The peak polished rod load is the maximum load ex-perienced by the polished rod while the minimum polished rod load is the least amount of load expe-rience by the polished rod. The ratio of these values is also displayed as MPRL/PPRL. This value is

• Gross pump displacement• Apparent net stroke• Effective net stroke• Net stroke displacement• Fluid load on the pump• Fluid level• Pump intake pressure• Pump volume efficiency• Pump fillage• Estimated pump friction

♦ Rod string stress analysis (listed for each rod segment)• Stress load %• Top maximum stress

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used to understand how aggressively the rods are oscillating. Some companies use this value as a fac-tor when determining if their design will run for an extended period of time without a problem.

Polished rod horsepowerThe polished rod horsepower is the power required at the polished rod to run the pump. This value is affected by parameters such as pump depth, fluid level, plunger size, pump condition, rod-tubing friction, etc. It is proportional to the area of the measured polished rod dynamometer card.

Permissible load horsepowerThe permissible load horsepower is the area bounded by the upper permissible load line, lim-ited by the structural rating of the pumping unit, and the lower permissible load line, limited by zero minimum load. It can be described as the capac-ity of the pumping unit as the area between these lines makes up the recommended operational range of the systems surface dynamometer card for the given conditions.

PRHP/PLHPThe ratio of the polished rod horsepower divided by the permissible load horsepower is another value used to evaluate the design. The ratio of the per-missible load horsepower divided by the polished rod horsepower should be as large as possible with-out overloading the pumping unit. If we were to use all of the available capacity of a pumping unit, the ratio would be equal to 1. This is not possible so it is our goal to maximize this value. For exam-ple, one case has a polished rod horsepower of 28.9 and a permissible load horsepower of 75.5. The ratio comes out to 0.38 which means the system is only using 38% of the pumping unit’s capacity. Another system has a polished rod horsepower of 26 and a permissible load horsepower of 44.5. This system is using 58% of the pumping unit’s capac-ity. This ratio gives you another way to compare

system designs.

System efficiencyThe system efficiency is calculated using instanta-neous efficiencies which are calculated throughout the stroke. These instantaneous efficiencies are used to calculate an overall efficiency which is the amount of energy supplied to the motor which is usable and lifts fluid.

Buoyant rod weightThe buoyant rod weight is the weight of the rods in fluid. The fluid creates a force on the rods which make them seem lighter than normal. When run-ning cases with fiberglass rods it is important to include buoyancy forces because fiberglass cannot be in compression. This will allow you to avoid this hazard. When running cases with steel it is important to run without buoyant forces because you need to design the rod string so that it will not buckle. It has been proven that buoyant forces to not cause buckling. Removing buoyant forces al-lows you to look at the linear forces that may cause buckling.

Unit structure loadingThis value is the percent loading on the structure of the pump jack. This number shows whether the measured peak polished rod load exceeds the structural rating of the unit. It must be less than 100% to avoid pumping unit structural damage or failure. If this number is too small (less than70%) then it shows that the unit structure may be too strong for this application.

Gearbox loadingThis shows how much the gearbox is loaded as a percent. It is recommended that the gearbox is loaded between 70% and 95%. For more detailed information on the gearbox loading and torque calculations, see the Torque Analysis and Gearbox


Torque Plots sections of this output report page.

Max. rod loadingThis value is the largest percent loading of all rod segments. This gives you an idea of how your rod string design is handling the well at a quick glance. More detailed information on the rod string can be found in the Rod String Analysis section of this output report page.

Required prime mover size for existing conditionsThis value calculated the required power needed to run the pump with the existing conditions. “Ex-isting conditions” refers to the way the pump is operating which includes leaks, high fluid levels, or other production problems. This does not include the balancing of the unit. This allows XDIAG to show you the required prime mover size required if the unit is balanced for minimum energy or mini-mum torque.

Torque analysisPeak gearbox torqueThis is the maximum required gearbox torque to operate the pump for the current downhole condi-tions. This value is reflected by the peaks in the Gearbox Torque Plots.

Gearbox loadingThis shows how much the gearbox is loaded as a percent. It is recommended that the gearbox is loaded between 70% and 95%. To see more de-tailed information about how the gearbox is oper-ating you can look at the Gearbox Torque Plots or the Permissible Load Diagram which is overlayed onto the dynamometer card plots.

Cyclic loading factorThe cyclic load factor shows how smooth the gearbox torque changes throughout the stroke. The smaller this value is, the less the gearbox torque fluctuates. The cyclic loading factor is also related to the thermal losses in the motor. A small cyclic loading factor will result in lower thermal losses in the motor and therefore higher system efficiency.

Counterbalance informationIf you enter a maximum counterbalance moment or counterbalance effect, the program calculates the above values for both existing and balanced conditions. If you did not enter an existing coun-terbalance moment XDIAG will calculate these values for balanced conditions only. The same applies for beam balanced units with a difference in the balancing method. XDIAG calculates the required structural unbalance to balance beam balanced units. This value will replace the maxi-mum counterbalance moment in the output report. Air-balanced units will show tank pressure in place of both the maximum counterbalance moment and counterbalance effect on the output report. Longstroke units (like the Rotaflex) will show counterbalance weight which will also replace both the maximum counterbalance moment and coun-terbalance effect.

Daily electricity useThe daily electricity use is calculated as Kilowatt-hours per day. Using the prime mover size and instantaneous system efficiency throughout the stroke, XDIAG can accurately calculate the amount of electricity required to operate the sys-tem over a 24 hour period.

Monthly electric billUsing the daily electricity use and the cost of electricity you enter, XDIAG calculates the cost of operating the well for one month.

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Electricity cost per barrel of fluid or oilThis value is calculated using the production rate and the cost of electricity to show you the cost of electricity to lift a barrel of fluid or oil. Other costs such as payroll and maintenance come into play when calculating the total cost to lift the fluid from the well. XDIAG can only calculate the lifting cost for electricity per barrel with the data entered in each case.

How to read additional columns for torque and energy consumption calculationsFor balanced conditions, XDIAG may show one or two different columns of all Torque analysis and Electricity Consumption calculations: one for balancing the unit to minimize torque and one for balancing the unit to minimize energy consump-tion. XDIAG will not run balancing calculations to minimize energy if the difference in lifting costs between balancing to minimize torque and energy is less than 1%. This is because balancing the unit for minimum energy will cause higher peak loads on the gearbox. The savings in lifting costs must justify the added wear on the gearbox.

You can use the XBAL program developed by Theta Oilfield Services to find out where to move the counterweights for crank balanced and beam balanced units. Clicking the XBAL button on the toolbar will record the balancing information to use in XBAL. If both balanced columns are dis-played (for minimum torque and minimum energy) you will be prompted as to which value you would like to use when you click the XBAL button on the XDIAG toolbar. You can also use the maxi-mum counterbalance moment or counterbalance effect in conjunction with manufacturer charts to figure out where to position counterweights to bal-ance the units. However, the easiest way to balance units is with the XBAL program.

Tubing, pump, and plunger calculationsTubing movementThe only calculation in this section which pertains to the tubing of the well is tubing movement. This will give you an idea of the effectiveness of the tubing anchor. If there is no tubing anchor on your well, this value might indicate the need for a tubing anchor. Tubing movement reduces the efficiency of the well because the pumping unit is lifting the tubing along with the plunger for a small distance. During the time the tubing is be-ing lifted the plunger is not producing fluid.

Gross pump strokeThe gross pump stroke is the total distance trav-eled by plunger from the bottom to the top of the stroke. This value shows the total travel of the plunger.

Gross pump displacementThis value is the maximum amount of produc-tion possible given the gross pump stroke calcu-lated. If the pump us full and the pump produces fluid throughout the stroke it would produce the amount of fluid shown here.

Apparent net strokeThe apparent net stroke is the stroke calculated where the fluid load is transferred from the travel-ing valve to the standing valve. Understanding the mechanics of the pump, some may assume that this stroke can be used when calculating the pro-duction of the well. This is incorrect because if the fluid load isn’t very large and the well is producing gas, the transfer of the fluid load from the traveling valve to the standing valve may occur while some of the fluid in the pump is gas. This is because the gas pressure may be able to open the traveling valve before it is compressed into liquid.


Effective net strokeThe effective net stroke is always equal to or small-er than the affective net stroke. This is because it is the stroke that produces fluid, which omits the part of the stroke that may have compressed gas. The following figure shows the relationship be-tween apparent net stroke and effective net stroke. The difference between the apparent and effective net strokes increases as the fluid load decrease. This is because the pressure of the compressed gas doesn’t need to be as large to open the traveling valve. A low pressure corresponds to a larger vol-ume of gas when gas is present which reduces the

amount of produced liquid.

Net stroke displacementThis value is calculated using the effective net stroke and should be in closer agreement with the actual production of the well. It is the amount of production that this well should be producing given the stroke at the pump and the strokes per minute.

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Fluid load on the pumpThis value is calculated using the specific gravity of the fluid, pump depth, and the fluid level. This value is the load on the plunger cause by the fluid. The horizontal lines set on the downhole card are used to calculate the fluid load on the pump.

Fluid levelThis value is displayed as fluid level from the sur-face or fluid level over the pump. Adding these two values together will equal the pump depth. This value is affected by the placement of the horizon-tal lines. The horizontal lines that are set on the downhole card are used to calculate the fluid load on the pump which is used to calculate the fluid level. As the fluid level get closer to the surface the fluid load on the pump decreases. This is because all the fluid in the casing annulus is pushing back on the fluid in the tubing so the plunger has to carry less of the load.

Pump intake pressureThe pump intake pressure is also calculated using the fluid load. If you change the horizontal lines on the downhole card you can see how the pump intake pressure is related to the fluid load.

Pump volume efficiencyThis value is calculated using the net stroke dis-placement and the entered production rate. This will tell you how well the pump is pumping fluid. If this value is over 100% then the input data has an error which implies that the pump is produc-ing more fluid than the volume of the pump can realistically pump given the stroke length. Pump volume efficiencies from 85% to 95% are excellent. High pump volume efficiencies suggest the pump is in good mechanical condition and it pump little to no free gas. Lower pump efficiencies indicate the pump is in poor mechanical condition, or there is incomplete pump fillage due to fluid pound or gas interference. XDIAG tells you what is wrong

with the pump by recognizing the calculated downhole dynamometer card shape.

A tubing leak can cause a low pump volumetric efficiency. Tubing leaks usually do not affect the shape of the downhole pump card. The only clue you may have that there is a tubing leak is a low pump volumetric efficiency. This also reduces the overall system efficiency. But to detect tubing leaks from pump volumetric efficiency you must have accurate production data. So, before you decide to pull tubing thinking that you have a tubing leak, pressure test the well to verify that leak exists.

Pump fillageThis value is calculated using the gross pump stroke and the net pump stroke. This will tell you if the pump is pumping free gas due to fluid pound or gas interference.

Estimated pump friction

Rod string stress analysisThis section shows all of the calculated rod data for each rod segment and displays the stress analysis method used for each rod segment. It also shows the maximum and minimum stresses at the top, and the minimum stress at the bottom of each rod section. For systems with fiberglass rods the calculated bottom minimum stress shows whether the fiberglass section is in compression. A negative bottom minimum stress can cause fiberglass rods to part prematurely. Also, to maximize rod life, stress loading must be less than 100%. If XDIAG shows a negative stress at the bottom of the fiber-glass section, or if rod loading for any rod sec-tion exceeds 100%, then the rod string should be redesigned. Then, if the rods part you can replace them with a new rod string design. This will help maximize rod string life. However, keep in mind that you must use a predictive computer program such as RODSTAR or XROD to redesign the rod string.


For sinker bars XDIAG calculates stresses and stress loading based on the elevator neck. XDIAG is programmed with the latest API standards and uses the appropriate elevator neck diameter for each sinker bar size.

3.2 Diagnosis of System Problems

Dynamometer and pump off control systems are commonly used with wave equation diagnostic programs, such as XDIAG, to help diagnose com-mon pumping system problems. Diagnostic tech-nology is based on a mathematical solution of the wave equation. The one-dimensional damped wave equation models the behavior of the rod string and allows calculation of downhole loads at any point in the rod string. The wave equation model in XDIAG calculates the downhole dynamometer card from the polished rod dynamometer card that you enter. Downhole dynamometer cards are much easier to interpret than surface cards because their shape depends only on the condition of the pump (for most wells).

Before running XDIAG you must record a quan-titative dynamometer card and you must complete an XDIAG data sheet. You can find copies of the XDIAG data sheet in the back of this manual.

3.2.1 Recording Dynamometer Card in the Field

You can find most pumping system problems from a dynamometer card analysis with XDIAG. This chapter describes practical, step by step procedures of how to use a dynamometer system to get the data you need to run XDIAG.

The dictionary defines the word “dynamometer” as an instrument for measuring force. It comes from two Greek words: “Dynamis” meaning “force” and “metron” meaning “a measuring device”. Therefore, “dynamo-meter” simply means “force-meter”. A dynamometer records polished rod load (force) as a function of polished rod position. This is com-monly called the “dynamometer card”. Early technology used equipment to draw an X-Y plot (dynamometer card shape) on a piece of paper. A common dynamometer system to date has a load cell, a position transducer, and a recorder box. Instead of plotting dynamometer cards on paper, as the early style dynamometers do, current systems store data on disk or in the computer’s memory. The latest technology will send this information wirelessly to a server where well information is stored. These systems can monitor and control wells. The recorded data can be analyzed automati-cally and if the data shows a problem the well can be shutoff automatically. XSPOC is automation software that can do this.

To record a dynamometer card you must insert the load cell between the polished rod clamp and car-rier bar. The position transducer has a string that clamps on the polished rod. The load cell contains strain gauges. Strain gauges are devices that use the change of electrical resistance of a wire to measure load. The strain gauges inside of the load cell contract when a load is applied to the load cell. This increases the cross sectional area of the thin wire. The change in area causes the change in re-sistance to the flow of electricity though the strain gauge. The electronic circuits in the dynamometer box translate changes in resistance into polished rod load. The position transducer box contains a potenti-ometer attached to a spring loaded pulley that has string wrapped around it. As the polished rod moves up and down, the string movement causes the potentiometer to turn. The electronics of the

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dynamometer system translate the number of times the shaft of the potentiometer turns into polished rod position.

Commonly Used Dynamometer Equip-ment:To record a dynamometer card you need a dyna-mometer system with a set of polished rod load and position transducers. In addition, you need the following tools:

♦ A set of two or three polished rod clamps for the polished rod sizes in your field.

♦ A wrench for the polished rod clamp bolts. ♦ A load transducer leveling plate. ♦ A “Knock-off” which is a piece of pipe one to

two feet long, cut in half lengthwise, with a safety latch.

♦ A stuffing box protector. ♦ Protective gloves. ♦ A strong chain that is 12-15 feet long. ♦ A piece of pipe to give you leverage when

tightening the polished rod clamp. ♦ An empty bucket.

Installing and Removing the Load and Position TransducersTo record a dynamometer card, you need to install the load and position transducers on the polished rod. You must insert the load cell between the permanent polished rod clamp and the carrier bar. Clamp the position transducer string to the pol-ished rod after you install the load cell. You must be very careful when recording data in the field, to avoid injury. The power switch must be off when installing the transducers or making measurements around the pumping unit. Also, dynamometer measurements are not recommended on units that do not have brakes in good working condition. A

good unit brake is vital to ensure operator safety especially when installing or removing the load cell from the polished rod. If possible, well analysts should work in teams of two for added safety.

Steps for Installing the Transducers1. Stop the pumping unit close to the bottom of

the downstroke. Engage the units brake and make sure that it holds.

2. If there is a polished rod liner, put the polished rod clamp about 6 inches above the stuffing box. Do not put the clamp on the polished sec-tion of the polished rod since it will be in the way when the unit starts to pump. Tighten the clamp to hold the polished rod load without slipping.

3. If you have a Hercules stuffing box (usually red with bolts), insert the stuffing box protec-tor (metal wedge) to support the load that may otherwise damage the stuffing box bolts.

4. Lay out all cables on the ground and zero the load and position transducers.

5. Turn the unit on and raise the polished rod close to the top of the stroke. Then turn the unit off and engage the brake.

6. Put the knock-off on top of the stuffing box and secure it by closing the safety latch.

7. Restart the unit and turn the power off just be-fore the polished rod clamp hits the top of the knock-off. You need to get the clamp to rest on the top of the knock-off as smoothly as possible while trying to throw slack between the per-manent polished rod clamp and the carrier bar. If the pumping speed is high, you may need to run the motor on and off every few mo-ments. This is so that you can transfer the load smoothly from the carrier bar to the knock-off. When you created enough room to insert the load transducer, turn the unit off and immedi-ately set the brake. Make sure the brake is on tightly enough to hold the polished rod load.

8. Load transducers are U-shaped and they usu-


ally have three buttons that must be pressed to record polished rod load. For accurate load measurement, at least two of these buttons must be pressed. If the carrier bar is so skinny that only one button will be pressed, then in-sert the load transducer with the buttons facing upwards. If you put the leveling plate between the carrier bar and the buttons you can be sure at least two of the buttons will be pressed. Otherwise, insert the load cell with the buttons down and insert the safety pin to hold it in place. Some load cells have this leveling plate as part of the load cell itself to avoid having to perform the above steps.

9. Narrow the distance between the carrier bar and the load cell using the brake. When they are about 2 inches apart, let off on the brake and let the carrier bar come up fast. If the unit cannot pick up the load, you need to turn the motor on momentarily until you pick up the polished rod load. Make sure there is some space between the carrier bar and the top of the knock-off. Apply the brake as soon as you pick up the polished rod.

10. Remove the knock-off, put the bucket as close to the well head as possible, and put the posi-tion transducer on top of the bucket to keep it clean. Attach the position transducer string to the polished rod. Make sure the cables are not tangled and then turn on the unit.

11. Wait for a few strokes until the well stabilizes (which is when the dynamometer card shape does not change from stroke to stroke). Then record the dynamometer card, counterbalance effect, and the traveling and standing valve checks.

Steps for Removing the Transducers1. To remove the load position transducer, stop

the unit at the beginning of the downstroke. Insert the stuffing box protector (if needed), place the knock-off on top of the stuffing box, and set the safety latch on the knock-off.

2. Turn the unit on and off to get the carrier bar to gently rest on the knock-off and to throw slack between the carrier bar and the perma-nent polished rod clamp. Then, turn the unit off and set the brake tightly.

3. Remove the load cell safety pin and then remove the load cell. Do this as quickly as pos-sible to avoid hand injury if the pumping unit brake does not hold.

4. Remove the position transducer clamp and slowly release the brake until the carrier bar picks up the polished rod load. Make sure there is enough space to allow removal of the knock-off. Then turn the power off and reset the brake.

5. Remove the knock-off and the polished rod clamp you installed, and restart the unit.

After you record the dynamometer card and while the load and position transducers are still on the polished rod, you can do traveling and standing valve checks. These checks help you find out if the pump barrel, plunger, or valves are worn.

Counterbalance Effect MeasurementTo have XDIAG do a torque analysis that shows the existing gearbox loading and unit balancing, XDIAG needs information about the existing counterbalance. One way to enter existing counter-balance data in XDIAG is by entering a measured counterbalance effect (CBE). XDIAG uses the measured CBE to calculate the maximum counter-balance moment and from this, the existing peak gearbox torque, etc. An easier and more accurate way is to use the XBAL computer program (please contact Theta Oilfield Services for more informa-tion).

The CBE is an indirect measurement of the unit counterbalance. To measure the counterbalance ef-fect you must stop the unit with the cranks as close as possible to 90° or 270°, then, with the brake off,

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record the polished rod load at that position. You must also record the corresponding counterweight crank angle or record the point on the dynamom-eter card plot when the counterbalance effect was recorded (with respect to position). When you re-cord the CBE as a point, you must record whether the unit was in the upstroke or downstroke where the CBE measurement was measured. You can then read in the counterbalance effect from the dy-namometer file. XDIAG uses the CBE measure-ment to calculate the maximum counterbalance moment.

If the unit is not perfectly balanced then the cranks will not stop close to the horizontal posi-tion. Instead, they tend to stop close to the 12 o’clock or 6 o’clock positions. In such cases, to record an accurate counterbalance effect you must chain off or prop up the polished rod.

If the unit is weight heavy then the unit has the tendency to stop with the horse head at the top of the stroke and the cranks at the 6 o’clock position. In this case you must chain off the unit using the following steps:

1. Stop the unit as close to 90° or 270° as possible, on the downstroke, and engage the brake. We stop the unit on the downstroke so that when we want to unchain the unit we simply turn it on for a moment and it will create slack in the chain.

2. With the pumping unit brake on, wrap a strong chain around the polished rod clamp and tie it down to the well head. Be sure to tie the chain to a strong part of the well head to avoid damaging it.

3. Release the brake and record the counterbal-ance effect (the polished rod load at that point).

4. Turn the unit on for a moment then off to re-lease tension in the chain. As you turn the unit off, engage the brake to hold the unit in place.

5. Remove the chain.

If the unit is rod heavy then the unit has the ten-dency to stop with the horse head at the bottom of the stroke and the cranks at the 12 o’clock posi-tion. In this case you must prop the polished rod up using the following steps:

1. Stop the unit as close to 90° or 270° as possible, on the upstroke, and engage the brake. We stop the unit on the upstroke so that when we want to remove the clamp we simply turn it on for a moment and it will pick up the polished rod load off of the clamp.

2. With the brake on, attach a clamp onto the polished rod just above the stuffing box.

3. Slowly release the brake. When the clamp rests on the stuffing box and the unit stop moving, record the counterbalance effect load.

4. Turn the unit on for a moment then off to pick up the polished rod load off of the clamp. As you turn the unit off, engage the brake to hold the unit in place.

5. Remove the clamp.

Stroke Length and Strokes per MinuteAccurate stroke length and strokes per minute measurements are very important when analyz-ing the performance of a pumping system. Still, when using XDIAG you do not need to measure the stroke length since the program calculates it from pumping unit dimensions. You only need to measure the stroke length for units that have been altered from their original design, when analyzing a hydraulic unit which has a variable stroke length, or checking the accuracy of the pumping unit dimensions that you measured.

To calculate stroke per minute (SPM) accurately, use a stop watch and record the time it takes for the pumping unit to cycle through several strokes


(for example 10 strokes). Divide the number of strokes by the time in minutes and you will calcu-late strokes per minute. In the following example, we timed a pumping unit which took 50 seconds to complete 10 strokes.

Tip: When measuring the time for calculating strokes per minute, use a point of reference in the stroke to start your stop watch. For example, if you start at the bottom of the stroke, then do the fol-lowing:

1. Wait for the polished rod clamp to approach the bottom of the stroke. Start the stop watch just as the clamp stops moving downward and reverses direction.

2. Wait for the clamp to move upward then downward to the bottom of the stroke. When the clamp is at the bottom of the stroke this is stroke number one. Continue to count the number of strokes in this way.

3. As you are completing the tenth stroke, stop the stop watch as the clamp reaches the bottom of the stroke and stops just before it reverses direction.

4. Record the time and calculate the strokes per minute as described above.

To run XDIAG you need a recorded dynamometer card and an XDIAG data sheet. You must carry XDIAG data sheets when collecting data in the field to make sure you have the data you need to run the program.

3.2.2 Downhole Pump Dynamometer Card Interpretation

XDIAG combines expert knowledge and pattern recognition with a wave equation sucker rod mod-el, accurate calculations of gearbox torque, unit balancing, power consumption, structure loading, etc. With XDIAG you can answer practically all questions about system performance quickly and accurately.

However, because all wells are not the same, you must be aware of the differences between different types of rod pumping systems. Rod pumped wells must be divided into two groups. The first group, that we will call “Group 1”, includes wells that are deeper than 4000 feet of are less than 4000 feet but have pump plungers that are 2.0 inches in diameter or less. The second group, that we will call “Group 2”, includes wells that are less than 4000 feet and have pump plungers larger than 2.0 inches. These two groups have unique character-istics that you must be aware of to diagnose prob-lems more accurately.

Characteristics of “Group 1” WellsSince this group includes all wells deeper than 4000 feet and all wells less than 4000 feet with pump plungers with a diameter of 2.0 inches or less, it represents the majority of rod pumped wells. For group 1 wells, dynamometer card shape depends on several factors including the follow-ing: pump depth, rod string material and design, pumping speed, pumping unit type, pump fillage, prime mover type, etc. This makes surface dyna-mometer card analysis very difficult. However, for these wells downhole dynamometer card shape depends only on the condition of the pump. For example, the pump dynamometer card shape cor-responding to fluid pound is the same regardless of depth, pumping unit type, rod string, pumping speed, etc. Verified downhole dynamometer card shapes for “Group 1” wells are available (see the

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appendix for shapes of “Group 1” downhole cards) and several papers have been published on diag-nostic techniques for these wells. XDIAG alone is sufficient to diagnose pump problems accurately for “Group 1” wells. You can do this by comparing the calculated downhole pump dynamometer card shapes to shapes that correspond to known condi-tions. The figures at the end of this manual show several downhole pump card shapes that you can use for this purpose.

Characteristics of “Group 2” WellsCompared to “Group 1” wells, “Group 2” wells ac-count for few of today’s rod pumped wells. “Group 2” wells include all wells of less than 4000 feet with pump plunger sizes larger than 2.0 inches. In this group there are many high volume wells that can cause large production losses when they are down. “Group 2” wells are separated from “Group 1” wells because they are affected by large fluid in-ertia forces. These forces are caused by large plung-ers, fast pumping speeds, and low fluid compress-ibility.

In deeper wells, rod loading is the main factor limiting production rates. Therefore, to reduce rod loading you must use a smaller pump plunger. Also, in deeper wells (deeper than 4000 feet) the rod string behaves more like a shock absorber, stretching when the pump plunger load increases. This effectively absorbs the “shock” of picking up the fluid load on the upstroke and no dynamic fluid forces appear on the downhole pump dyna-mometer card. However, in the shallow high rate “Group 2” wells, fluid inertia is significant and sometimes can more than double the load on the pump plunger. Because the plungers in these wells are large, they must pick up the fluid in the tub-ing and accelerate it upward at rates that are much higher than for deeper wells. Also, because of the shallow depths of “Group 2” wells, the rod string is practically rigid and does not provide any shock absorption. This results in significantly higher loads than would be predicted by considering the

dead fluid alone.

The fluid inertia effects on the pump depend on plunger size, pumping speed, and fluid compress-ibility. This makes diagnostic analysis of “Group 2” wells very difficult. For “Group 2” wells, both surface and downhole dynamometer card shapes depend on pump condition, pump depth, plunger size, pumping speed, and the fluid compressibil-ity. Therefore, unlike “Group 1” wells, you cannot identify the downhole pump condition by simply comparing the calculated pump card shape to known pump card shapes.

Up to now, the peculiar characteristics of “Group 2” wells had not been well documented. Since the downhole pump dynamometer card shape for any given pump condition depends on so many factors, conventional diagnostic techniques (such as those used on “Group 1” wells) are insufficient. Compar-ison of calculated downhole pump dynamometer cards for “Group 2” wells with known downhole card shapes developed for “Group 1” wells can result in incorrect conclusions. For example, the downhole pump dynamometer card shape corre-sponding to a full pump for a “Group 2” well may be similar to the shape for a severely worn pump for “Group 1” wells. This can cause unnecessary pulling jobs and frustration due to misdiagnosis of pump condition. To diagnose pump problems correctly for “Group 2” wells you need an ad-ditional tool known as predictive wave equation program. A predictive wave equation program can model not only the behavior of the rod string but also the fluid inertia effects. RODSTAR-V/D or XROD (developed by Theta Oilfield Services) is such a tool. Because RODSTAR-V/D and XROD can model fluid inertia effects, they can accurately simulate the behavior of “Group 2” wells and can predict the shape of both surface and downhole dynamometer cards for a full pump. If the predict-ed dynamometer card shape matches the measured one, then you know that the pump is in good mechanical condition.


Also, XDIAG understands “Group 2” wells and recognizes “strange” downhole dynamometer card shapes. Using its built-in “experience” with “Group 2” wells, XDIAG can accurately diagnose prob-lems with these wells.

Downhole Dynamometer Card Shape Analysis for “Group 1” WellsThe figures at the end of this manual show a col-lection of downhole dynamometer card shapes that correspond to most pump operating conditions or problems for “Group 1” wells. Although XDIAG interprets the downhole pump card shape for you, it is still useful to know what these shapes are so that you can figure out the pump condition. Keep in mind that these shapes are only valid for “Group 1” wells.

3.2.3 Avoiding Rod Compression

Because XDIAG calculates stresses at the bot-tom of each rod section in the rod string, you can use it to check for compression. This feature is especially useful for fiberglass rods that must never be in compression. Compression in fiberglass rods will surely cause the rods to part. If you use RODSTAR-V/D or XROD to design fiberglass rod strings then you can prevent this problem from ever occurring. Rod compression is also detri-mental to steel rods. Excessive rod compression can cause buckling related failures. According to research done by Norris Sucker Rods, you must maintain a minimum load of +2000 pounds at the top of the lowest sucker rod section to avoid buckling problems. This load corresponds to a minimum stress of 3300 psi doe 7/8 inch rods and 4530 psi for ¾ inch rods. We recommend design-ing a rod string with sinker bars so that the bottom minimum stress of the lowest sucker rod segment (just above the sinker bars) is between 300 and 600 psi.

If you detect rod compression, you can add more sinker bars, reduce the pumping speed, or use a pumping unit with a slower downstroke polished rod velocity. These changes will reduce rod com-pression. To find out how many sinker bars you need to eliminate rod compression, use ROD-STAR-V/D or XROD. With RODTAR-V/D or XROD you can design a rod string with minimum rod compression. You can even have the programs design a rod string for you using its expert system design capabilities. When you have RODSTAR-V/D design a fiberglass rod string, you must be sure to add enough sinker bars so that the fiber-glass rods are not in compression. XROD can do this for you automatically.

3.2.4 Gearbox Torque and Unit Balancing

Sometimes, using the largest available stroke length may not be the best way to maximize production since this can overload the gearbox. You may be able to use the next smaller stroke and speed up the unit to get the production rate you want without overloading the gearbox. Another way of reducing gearbox torque is by using a small-er pump plunger and faster pumping speed. You may use a lighter rod string by using high strength or fiberglass rods which may decrease the gearbox loading. Sometimes XDIAG will show that energy consumption will increase if you balance the unit for minimum torque. This is normal because mini-mizing torque doesn’t directly relate to minimizing energy consumption. Balancing the unit for mini-mum torque makes the peak torque on the up-stroke equal to the peak torque on the downstroke but also changes the torque throughout the cycle. The instantaneous efficiency calculated for each point throughout the cycle or stroke changes with the changes in the torque values. In some applica-tions the energy consumption can increase when you balance the unit for minimum torque because the prime mover now spends more time in the less efficient part of its performance curve.

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3.2.5 Using XDIAG with RODSTAR-V or XROD

XDIAG helps you find problems such as over-loaded rods, worn pump, overloaded gearbox, poor system efficiency, excessive fluid pound, etc. Once you find a problem that requires redesign-ing the system, you must predictive program such as RODSTAR-V or XROD to help you evaluate different changes to the system. For example, if you find that the second section on the rod string is overloaded you may want to redesign the rod string to eliminate this problem. Possible solutions include creating a “balanced” rod string design to minimize rod loading, using stronger rods such as Norris 97, Weatherford EL, or LTV HS, using a smaller plunger size, etc. RODSTAR-V and XROD can help you evaluate different solutions to this problem. They allow you to predict the effect of each change on system performance and load-ing. RODSTAR-V and XROD do not depend on input of a measured dynamometer card but instead simulates the pumping system you specify. RODSTAR-V and XROD predicts the surface dynamometer card along with other important parameters relating to system performance.

Although RODSTAR-V and XROD are primarily design tools, they can be very powerful diagnostic aids when used in conjunction with XDIAG. This is due to the powerful overlay feature that allows direct comparison of predicted versus measured cards.

Using RODSTAR-V’s and XROD’s Dynamometer Overlay FeatureThis feature can have many different uses. For example, it can help you to verify whether the load cell is out of calibration, if the fluid level you mea-sured is accurate, etc. RODSTAR-V and XROD can help you find these problems by comparing the

shape and load range of the measured dynamom-eter card versus the one predicted by the program. Also, the predictive programs can help verify downhole problems such as a worn pump, leaking traveling or standing valves, deep rod parts, stuck pump, etc. You can simulate a worn out pump or a deep rod part by entering a fluid level at the sur-face (zero feet from the surface). This will result in a zero fluid load on the pump plunger.

RODSTAR-V and XROD cannot simulate a traveling valve leak, a hole in the pump barrel, or a sticking pump. But it can predict what the dynamometer card should look like if there were no problems. You can use this comparison of the actual dynamometer card shape with the predicted card shape and have confidence in XDIAG’s diagnosis of system problems. For example, if you have a traveling of standing valve leak or a worn out pump, then the pump will be doing less work and the measured surface dynamometer card will contain less area than the predicted surface dyna-mometer card.

If the pump is sticking, or if there is more friction that normal between rods and tubing (which may be due to paraffin, scale, etc.) then the predicted surface dynamometer card from RODSTAR-V or XROD will be smaller than the measured dy-namometer card. This is especially true for steel rods. By entering a larger rod-tubing friction, you can obtain a better match between the measured and predicted dynamometer cards (cause this will increase the predicted surface dynamometer card’s area) which can aid in improving future designs.

Note: Rod-tubing friction is especially important for fiberglass rods. Higher friction than normal may actually reduce the area of the predicted sur-face dynamometer card because it causes the rods to stretch and give a small stroke at the pump.


3.2.6 Setting Lines on Downhole Pump Cards

XDIAG automatically sets the horizontal and vertical lines, unless the pump is not in good condition, to calculate pump intake pressure, fluid level, net pump stroke and production through the pump. Also, XDIAG allows you to modify the line settings after the run. To understand how to set these lines it is necessary to discuss some of the assumptions made when XDIAG does its calcula-tions.

Setting Horizontal Lines:

To calculate the downhole dynamometer card using the wave equation, XDIAG assumes an average friction between rods and tubing. If you were to enter the exact friction coefficient between rods and tubing, then XDIAG would calculate a downhole dynamometer card that shows exactly how much fluid load the pump plunger carries (assuming it is in good mechanical condition)/ For example, in a case with fluid pound, XDIAG would calculates a downhole dynamometer card similar to Figure 3.1. However, because rod-tubing friction is different in each well, it is impossible to know that friction coefficient to use. Fortunately, it is not necessary to know the exact friction to get useful results with XDIAG. When calculating a downhole dynamometer card, it is better to under-estimate rod-tubing friction than to over-estimate it. If you enter a friction coefficient that is too large, the wave equation model will remove more load than it should from the calculated downhole dynamometer card. This will distort the downhole dynamometer card shape. This is why it is better to use a friction coefficient that is lower than actual. The default friction coefficient of 0.5 in XDIAG is a safe number to use for most applications. The only “side effect” of using a lower than actual fric-tion coefficient is that the calculated downhole dynamometer cards are “fatter” than actual. This

occurs because the wave equation removes only a part of the frictional load. The remaining frictional forces appear as extra load on the calculated down-hole dynamometer card. For example, Figure 3.1 would look more like Figure 3.2 with the added frictional forces. You can see how XDIAG didn’t remove all fractional loads from the calculated downhole dynamometer card and it appears “fat-ter”. However, you can still use this downhole card to identify problems at the pump.

If all you want to do is to identify the pump condi-tion, then the friction coefficient makes little dif-ference. However, if you can separate the frictional loads from the actual fluid load on the plunger, you can calculate pump intake pressure and fluid level from a downhole dynamometer card. You can do this by setting two horizontal lines as shown in Figure 3.2. The area above the top line and below the bottom line represents frictional work at the pump. The distance between the two hori-zontal lines is the true fluid load on the plunger. Once you know the fluid load, you can calculate the pump intake pressure and the fluid level as explained in Figure 3.3. The fluid load on the pump plunger corresponds to the pressure differ-ence across the pump plunger. If we assume that the pressure in the pump barrel on the upstroke is about the same as the pump intake pressure, then you can use equation 1 in Figure 3.3 to calculate the fluid load on the plunger. You can calculate the pressure above the pump plunger using equation 2, and the plunger area using equation 3. Then, you can solve equation 1 for the pump intake pressure as shown in equation 4.

The fluid load, Fo, is the distance in pounds between the two horizontal lines you set on the downhole dynamometer card. Because the pump intake pressure is also a function of the fluid level in the tubing-casing annulus, it also can be calcu-lated using equation 5. Since we know the pump intake pressure from equation 4, we can solve equation 5 for fluid level over the pump as shown

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in equation 6. This is how XDIAG calculates the fluid level from horizontal line settings. XDIAG assumes that the casing fluid is oil and uses the oil API gravity to calculate the casing fluid specific gravity.

Using the above method you can calculate pump intake pressure and fluid level even in wells with packers or with foamy fluid over the pump. Shoot-ing a fluid level with a fluid level sounder (echo meter) will not give meaningful results in this case because you do not know the gradient of the fluid in the annulus. By setting horizontal lines on the downhole pump dynamometer card you can get more accurate results because pump intake pressure affects plunger load. If you have foamy fluid over the pump, XDIAG’s calculation of fluid level will not agree with the shot fluid level. This is because using the above method, XDIAG calculates an effective fluid level by assuming the annulus is full of oil and not mixed with gas. This works because when you have foam over the pump the fluid level is meaningless since it does not tell you if more production is possible. Fluid level is easier to visualize than pump intake pressure. But, if you have foam over the pump then pump intake pres-sure is the only meaningful quantity you should look at.

Setting Vertical Lines:

XDIAG separates the net stroke from gross pump stroke with a set of vertical lines that it sets on the calculated pump card. The gross pump stroke is the total distance the plunger moves. Figure 3.2 shows the gross pump stroke on a downhole card of a pumped off well. The net stroke is the portion of the gross pump stroke during which the plunger moves through fluid in the pump (on the down-stroke). In other word, net stroke is the part of the pump stroke that produces fluid. By setting vertical lines, XDIAG estimates the amount of fluid going through the pump. This also lets you estimate pos-

sible production gains if you can increase the net stroke. For example, if the pump card shows gas interference, you can move the second vertical line to the right to see how much more liquid produc-tion you could get by using a gas anchor or by lowering the pump intake below the perforations.

Tips for Setting Horizontal and Vertical Lines:

To accurately set horizontal and vertical lines you must have experience with dynamometer card shape interpretation. Otherwise, it will be bet-ter to let XDIAG set the lines for you. For hori-zontal lines you must have an idea of how much rod-tubing friction your well normally has. If we assume that friction is about equal on the upstroke and downstroke, then for a fluid pound case you can draw the lines as shown in Figure 3.2. The top horizontal line intersects the “nose” of the dynamometer card. This splits the friction equally between the upstroke and the downstroke. Then you can set the bottom line so that it removes about the same amount of friction as the top one does (equal to half the thickness of the nose). It is easier to set lines on the downhole pump cards with fluid pound or gas interference because of the nose in the card shape. Also, since the well pounds fluid, the fluid level (from the surface) is close to the pump intake.

Once you figure out where to place the lines when the well is pounding fluid then you can use the same horizontal line setting when the pump is full. If the well does not pump off then shoot a fluid level reading and record the dynamometer card at the same time. Then, after XDIAG calculates the downhole dynamometer card, set the horizontal line so that the calculated fluid level matches the fluid shot reading. Remove the same amount of friction on the upstroke as the downstroke. From now on, use the same horizontal line settings whenever you analyze the same well. You should


only set lines on a downhole pump dynamometer cards that show a good mechanical pump condi-tion. If the traveling valve or plunger is worn, it cannot pick up the entire fluid load which means setting horizontal lines will yield incorrect results. Figure 3.4 and Figure 3.5 show example line set-tings for many common pump card shapes. Use the examples along with measured fluid levels and see how XDIAG sets the lines to learn how to set horizontal and vertical lines yourself.

Vertical line placement is easier than horizontal line placement. When setting vertical lines you are estimating the net pump stroke. The gross pump stroke is the total plunger travel. The net stroke is the portion of the gross pump stroke that produces fluid. For fluid pound or full pump cases, you can place vertical lines as shown in Figure 3.4 and Figure 3.5. For gas interference cases the net pump stroke should account for both gas expansion on the upstroke and gas compression on the down-stroke. For downhole pump cards that show severe problems, XDIAG will not set the lines on the downhole pump dynamometer card.

If the downhole pump card calculated by XDIAG corresponds to a worn pump, stuck plunger, or any other condition for which line placement is not possible, do not set the lines yourself. Sometimes, it is possible to set either vertical or horizontal lines on these problematic wells but not both. XDIAG provides you the flexibility to set either pair of lines.

Effect of Plunger Size and Fluid Specific Gravity on Line Placement:

As Figure 3.3 shows, the fluid level calculation from horizontal lines depends on plunger diameter and fluid specific gravity. If you make a mistake when entering either the plunger diameter or fluid specific gravity, the calculations from the hori-

zontal lines will be in error. Often XDIAG may detect possible input data errors in plunger size or fluid specific gravity when setting horizontal lines. For example, if you enter the wrong plunger size, then the fluid level calculated from horizontal lines may be too low or too high depending on whether you entered a plunger that is larger or smaller than actual.

When setting horizontal lines, XDIAG does not let the calculated pump intake pressure go below casing pressure. If plunger size or fluid specific gravity is smaller than actual, you will not be able to move the horizontal lines as far apart as they should be. If you set the lines yourself and start with the top line first, you will not be able to move the bottom line close to the bottom of the dyna-mometer card.

If the pump plunger size or specific gravity of the produced fluid is larger than actual, you cannot get a low enough pump intake pressure even if you move the horizontal lines as far apart as they can go. If you set the top line first, you will see a higher than expected pump intake pressure even after you move the bottom line all the way to the bottom of the card.

Theta Oilfield Services, INC., 1901 E. Lambert Rd. Suite 108 La Habra, CA 90631 USA Telephone #: (562) 694-3297, Fax #: (562) 694-8641 www.gotheta.com

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