rod pump& pcp

Schlumberger Artificial Lift Design: Onshore

PIPESIM Artificial Lift Design and Optimization, Version 2011.1 11

Exercise 1 Analyzing Well Performance

You will run Nodal analysis that is part of well performance

analysis, based on the principle that the completion and

production system can be divided into two sub-systems: reservoir

inflow and wellbore outflow.

To analyze well performance:

1. Create the well model shown here using well schematics and

data listed in the table.

Reservoir Data

Static Pressure (Pws) 1,700 psia

Temperature 240 degF

Model type Vogel’s Equation

Vogel Coefficient 0.8

Test Flow rate 300 STB/day

Test BHP 1,400 psia

Wellbore Data (use detailed model)

Tubing ID 3.958 in

Tubing Depth 6,000 ft

Perforation Depth 6,000 ft

Wellhead ambient temp 60 degF

Artificial Lift Design: Onshore Schlumberger

12 PIPESIM Artificial Lift Design and Optimization, Version 2011.1

2. Select Operations > Nodal Analysis.

3. Click the Limits button.

4. Choose the option Limit the outflow curves to lie within the

pressure range of the inflow curves.

5. Set the outlet pressure to 200 psia and run the Nodal

Analysis operation.

6. Report the current behavior of the well.

7. Estimate the amount of pressure boost required from an

artificial lift solution.

• Is the well producing naturally?

• What is the absolute open flow potential (STB/d)?

• What is the DP required to achieve the production target

(psi)?

Fluid Data

Water Cut 24%

GOR 200 scf/STB

Oil gravity 28 API

Gas SG 0.87

Water SG 1.03

Bubble Point Calibration Sat. Gas 200 scf/STB

3,200 psia

240 degF



Exercise 2 Designing a Tapered String Rod

Pump

A tapered design is the most common configuration for a rod

string longer than about 3,500 feet. This design uses

combinations of rods with different diameters, installed with the

largest diameter rod at the top and the smallest rod at the bottom.

PIPESIM automatically selects and recommends rod size

distribution and respective length based on stress loading.

To design a tapered string rod pump:

1. In the PIPESIM window, launch the Rod Pump Design

interface by selecting Artificial Lift > Rod Pump > Rod

Pump Design.

2. View the Well Information tab for data pulled in from the

base PIPESIM model.



3. Choose surface and downhole equipment on the Equipment

Selection tab shown in the figure.



4. On the Design Control tab, specify these parameters:

• Target production rate

• Pump depth

• Operating conditions

• Downhole separator.

5. Click Run Design.

6. Analyze the design results and plots and then enter the data

in the table.

Selected pump

Pump intake pressure psia

Pump discharge pressure psia

DP across pump psi

Nominal flow rate at pump bbl/d

Required power hp

Number of rod strings

Net pump efficiency %



Exercise 3 Designing with a User-Specified

Rod String

Frequently, the pump design is based on available rod strings and

other equipment from inventory. For this exercise, assume a 1-2/8

rod string is available.

To design a pump with a user-specified rod string:

1. On the Equipment Selection tab, include a user-specified

single rod string of 1-2/8 inch.

2. Leave all other settings on the Equipment Selection tab

unchanged from Exercise 2.

Is the Pumping Unit (LC640D-256-144) good enough for new

rod string?

3. Choose a new pumping unit from the user inventory Lufkin

Conventional LC 640D-305-144.



4. Perform a redesign and report the following results:

5. Check the stress loading calculation for the rod string.

• Is the rod string suitable for the application?

• What is the stress loading? (%)

Selected pump

Pump intake pressure psia

Pump discharge pressure psia

DP across the pump (psi) psi

Nominal flow rate at the pump bbl/d

Required power hp

Number of rod strings

Net pump efficiency %



Exercise 4 PIPESIM Rod Pump Simulation

PIPESIM allows rod pumps to be defined in the Downhole

Equipment tab of the Tubing Editor (detailed tubing model only).

This allows you to simulate rod pumped wells for standard well

performance and perform network analysis in PIPESIM.

1. Open the PIPESIM Tubing Editor and convert the tubing

model to display in detailed mode.

2. Specify Rod Pump at a pump setting depth of 5,500 ft.



3. Configure properties in the Rod Pump dialog based on the

results obtained from Exercise 3.

4. Perform Nodal Analysis or a Pressure Temperature Profile.

5. Report the results.

• What is the production rate (STB/d)?

• Pump Power (hp)?

6. Save the model as rodpump.bps.

Questions

These questions are for discussion and review.

• Why use a tapered rod string?

• What are the factors affecting rod pump efficiency?

• How does rod size impact the pumping unit selection?



Lesson 2 Progressive Cavity Pump

Overview

Progressive cavity pumps (PCPs) are a special type of rotary

positive displacement pumps, sometimes referred to as single-

screw pumps. Unlike electric submersible pumps (ESPs), PCP

performance is based on the volume of fluid displaced and not on

the dynamically generated pressure increase through the pump.

PCPs are an increasingly common form of artificial lift for low- to

moderate-rate wells, especially onshore and for heavy (solid

laden) fluids.

PCP systems have many advantages over other lift methods:

• Overall high energy efficiency (typically 55-75%)

• Ability to handle solids

• Ability to tolerate free gas

• No valves or reciprocating parts

• Good resistance to abrasion

• Low internal shear rates (limits fluid emulsification through

agitation)

• Relatively lower power costs (prime mover capacity fully

utilized)

• Relatively simple installation and operation (low

maintenance)

• Low profile surface equipment and noise levels.



Principle of Operation

A PCP (Figure 2) is comprised of two helical gears: a stationary

gear called the stator (external gear) and a rotating gear called the

rotor (internal gear). The stator is commonly made of an

elastomer but it also can be made of steel. The rotor is positioned

inside the stator and rotates along a longitudinal axis.

Figure 2 Composition of a progressive cavity pump (PCP)

The volume between the stator and rotor forms a sealed cavity

that traps the fluid. As the rotor turns, this cavity progresses the

fluid from the inlet to the outlet of the pump. The volume of the

cavity and the rotational speed (N) determine the flow rate

achieved by the pump.

The volume of the cavity is calculated based on geometric

parameters. The volume of the cavity is defined by the diameter of

the rotor (Dr) times the stator pitch length (Ls) times the

eccentricity (e). The eccentricity is defined as the distance

between the centerlines of the major and minor diameters of the

rotor.



Therefore, the flow rate through the pump can be expressed as:

Q = 4eDrLsN

In field units, Ps, e, and D are noted in feet, while N is specified as

revolutions per-minute to give a rate in ft3/min. Multiply by 256.46 to

convert to BPD. The geometric parameters required for this

calculation vary considerably among vendors and are generally

not published.

Hydraulic power can then be calculated by the equation:

Hhp = 1.7 X 10-5 DP Q

where DP is the pressure differential across the pump (psi) and Q

is the rate (BPD).

In practice, the clearance between the rotor and stator are not

perfect due, mainly, to deformation of the elastomeric stator as a

function of pressure, temperature, and wear. This causes some of

the fluid to slip back into preceding cavities. Slip increases with

increasing pressure and the number of stages.

TIP: Higher viscosity fluids exhibit less slip.

PCP performance curves are generally used for simulation

purposes. While the format of performance curves varies by

vendor, PIPESIM has adopted the format suggested by ISO

15136-1 (2009)1.

PIPESIM provides performance curves from several vendors

based on reference conditions (generally, water at standard

conditions). While catalog performance curves for rotodynamic-

type pumps (such as ESPs) are generally consistent with field

performance, PCP performance curves vary considerably as a

result of different operating conditions (pressure and temperature)

and fluid properties.

The catalog curves available from within PIPESIM should be used

only for preliminary analysis. It is common for PCPs to undergo

bench tests to generate performance curves for specific pumps at

intended operating conditions. It is recommended that these

bench test curves be used for more detailed simulation studies.

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doc.chm::/pipesim/td/refe rences.ht ml#ISO15136-1



Viscosity Effects

PIPESIM offers the option to apply a viscosity correction to reduce

slippage effects for higher viscosity fluids. The Karassik et al1

method is used.

Exercise 1 Running a PIPESIM PCP

Simulation

To simulate a PCP, PIPESIM maintains a database of

manufacturers and models from which you can select a pump that

is suitable for the target well. If the required PCP is not in the

database or does not have a bench test performance curve

available, you can enter the required data into the database.

To run a PCP simulation:

1. Save the previous model used for designing the rod pump as

PCP.bps.

2. On the Downhole Equipment tab in the tubing model,

change the Rod Pump to a PCP.

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doc.chm::/pipesim/td/refer ences.htm l#karassik2001



3. Choose the Manufacturer and Model based on Diameter and

Nominal rate to ensure the pump fits in the casing and is

suitable for the target production rate at design speed. Refer

to the figure.

NOTE: You must calculate a speed that can meet the target

production rate. This will be done in a later step.



4. Run a Pressure Temperature Profile operation to estimate

the speed required to achieve the production rate

(400 STB/d), as specified in Lesson 1, Exercise 2.



Exercise 2 Predicting Future Well Lift

Performance

1. Review and compare performance of the well at a future date

when reservoir pressure declines to 1200 psia.

2. Modify the Completion for both the Rod Pump and PCP

models to set the Reservoir Pressure to 1200 psia and

the AOFP to 800 BPD.

3. Rerun the Rod Pump Design using the same pumping unit.

4. Rerun the PCP simulation to determine the speed required to

achieve the same production rate.

• Is current Rod Pump Setup good for future operation?

• Is current PCP Unit Setup good for future operation?

Selected PCP Model

Required Speed for the PCP rpm

Pump Power? hp



5. Record comparative results in the table, if the data are

available.

What is the recommended artificial lift method?

Review Questions

• What are the factors affecting a PCP performance curve?

• Why do you need bench test data to accurately predict PCP

performance for a given well system?

Summary

In this module, you learned about:

• performing basic well performance analysis

• designing a rod pump installation

• evaluating well performance under progressive cavity pump

• assessing future well performance.

Comparison Summary

Result Current Future

Rod Pump Unit

Rod Pump Power

Rod Stress Loading

Rod Pump Efficiency

PCP Unit

PCP Operating Speed

PCP Power Required

PCP Efficiency

rod pump& pcp

Documents

degfartificial lift

design results

artificial lift solution

design control tab

rod pump designinterface

smallest rod

rod size distribution

largest diameter rod