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NextGen Product Overview NextGen is the world’s most advanced pipeline simulation application, and incorporates steady state and transient predictive, online, and look ahead hydraulic simulation into a single application. NextGen can be run stand-alone on a single user’s machine with connectivity to Excel for easy data imports, exports, and automation, or with its client server architecture can also be installed as an interconnected enterprise wide solution that integrates hydraulic simulation with Graphical Information Systems (GIS), SCADA systems, Nominations systems, and enterprise databases. NextGen is actually GEI’s fourth generation simulation software and was built with the knowledge accumulated over 30 years of simulation development and input from pipeline engineers, operators, and simulation users throughout the industry.

NextGen Pipeline Simulation Suite CONFIDENTIAL Gregg Engineering, Inc. of 36 2017

All-In-One Simulation Interface All simulation sections available in a particular model in NextGen are synchronized so that any pipeline configuration change such as adding a lateral or a new compressor station, process plant or valve, is au-tomatically propagated to all sections (so users don’t have to update a steady state model, and then update a separate transient predictive model, online model and look ahead model). These simulation sections however also operate independently, and if needed will make use of multiple run engines for the same pipeline model. For example, a user can launch a transient predictive run, and while it is running, switch to the steady state tab of that model, and edit data, make runs and view results in steady state, before going back to the model’s transient predictive simulation.

When a model is created or opened, NextGen supports five different types of hydraulic simulation for that model within the same interface, and users can simply switch tabs to go from one simulation type to another. The following simulation types are supported:

• Steady State (Gas and Liquid) • Sequential Steady State (Gas and Liquid) • Transient Predictive (Gas) • Transient Online (Gas) • Transient Look Ahead (Gas)


Gas and Liquid Pipelines

When a user creates a model, and assuming the Liquids Module is enabled, the user can select whether the pipeline should be gas or liquid, and NextGen will automatically switch between gas and liquids mode as needed depending on the model type.

Large and complex gas models for gathering, transmission, and distribution pipeline systems can be modeled in NextGen. Users can specify and track differing compositions of gas within the model where natural gas is the default composition, and there are many equations and algorithms specific to natural gas that are available as options within NextGen, but any compressible gas can be modeled.

Two phase flow can also be modeled within Gas models. Steady State, Sequential Steady State, Transient Predictive, Transient Online, and Transient Look Ahead modeling is supported for gas pipelines. For a Liquid model, users can specify the type of pipeline being modeled and different categories of equations will be activated depending on the type (Crude Oil, Water, Processed Water, Other). Steady State and Sequential Steady State modeling is supported for liquids pipelines.

Pipeline Types that can be modeled in NextGen:

• Natural Gas Pipelines (or any other gas) o Nodes, Meters (unlimited number of meters per node), Gas Wells as nodes/meters (ARPS, PLE),

Pipes, Detailed Compressor Stations (6 Centrifugal Unit types, 4 Reciprocating Unit types), Regulators, Valves, Check Valves, Storage Fields, Process Plants, Chillers, Flow Meters, Gas Wells as Legs (Back Pressure, IPR), Ruptures/Leaks.

o 18 Friction Factor equations, 6 Z Factor equations, 9 Equation of State Correlations o Temperature Tracking, Specific Gravity Tracking, Heating Value Tracking, Liquid Tracking, Gas

composition Tracking (18 core components + custom components), Source Tracking, Revenue Tracking, Dew Point Pressure and Temperature Calculations


o Supports systems sizes of 1,000,000+ nodes for Steady State and Sequential Steady State, and up to 50,000 nodes for Transient (Transient can support 250,000 nodes if Tracking accuracy is degraded).

• Crude Oil Pipelines o Nodes, Meters (unlimited number of meters per node), Oil Wells as nodes/meters (ARPS, PLE),

Pipes, Detailed Pump Stations (3 Unit types), Regulators, Valves, Check Valves, Storage Tanks, Process Plants, Warmers, Flow Meters, Wells as Legs, Leaks

o Oil well modeling, production decline analysis o DRA Tracking, K Factor (~grade of crude oil) Tracking, Temperature Tracking, Specific Gravity

Tracking, Composition Tracking (custom components), Source Tracking, Revenue Tracking o Built in equations for viscosity and other parameters o Supports systems sizes of 1,000,000+ nodes for Steady State and Sequential Steady State.

• Water Distribution Systems o Complex residential network modeling o Nodes, Meters (unlimited number of meters per node), Water Wells as nodes/meters (ARPS,

PLE), Pipes, Detailed Pump Stations (3 Unit types), Regulators, Valves, Check Valves, Storage Tanks, Process Plants, Warmers/Chillers, Flow Meters, Wells as Legs, Leaks

o Oddly Shaped Water towers (nonlinear pressure/volume relationships) o Water well modeling o Temperature Tracking, Source Tracking, Revenue Tracking o Built in equations for viscosity and other parameters o Supports systems sizes of 1,000,000+ nodes for Steady State and Sequential Steady State.

• Processed Water (Salt water, Brine water) Pipelines o Nodes, Meters (unlimited number of meters per node), Wells as nodes/meters (ARPS, PLE),

Pipes, Detailed Pump Stations (3 Unit types), Regulators, Valves, Check Valves, Storage Tanks, Process Plants, Warmers, Flow Meters, Wells as Legs, Leaks

o Brine Concentration Tracking, Temperature Tracking, Source Tracking, Revenue Tracking o Built in equations for specific gravity, viscosity and other parameters o Supports systems sizes of 1,000,000+ nodes for Steady State and Sequential Steady State.

• Other o Any liquids products pipeline, NGL, ...

Modularized Architecture and Licensing NextGen is modularized so that customers only need to license and pay for those modules and features which are actually needed.

Some clients may only need basic steady state capabilities for a single user on a single machine, whereas others might need a full blown enterprise wide transient online system for multiple users spread out throughout the company or even at different company locations. The licensed protection key determines what sections and modules are enabled and activated, and upgrades to new features and modules typically do not require a new NextGen installation, but simply a new protection key.


Client Server Architecture NextGen can be run as a single user application on a single machine or as an interconnected client server solution for multiple users. Every installed copy of NextGen can act as a single user application, but also contains all of the modules needed to support a powerful server connected to multiple clients and multiple run engines.

Every installed copy of NextGen can act as a Simulation Server, an Interface Client, a Run Engine Client, or all three, or even act as a run engines only installation in which multiple NextGen run engines are launched and stay connected to a NextGen server on another machine. What is allowed to run on any particular installation depends on the protection key license and what the user wants to run. When run as a single user application on a single machine, NextGen will boot up a Simulation Office interface client application, but in the background NextGen will also boot up a local Simulation Server application and one or more Simulation Engine applications on the same machine, and all three applications will communicate locally (all of this is transparent to the user). Simulation Office is the primary interface client application that is used to edit and view model information, and acts as a thin client. The Simulation Server application stores all model information on disk and in memory as needed, performs all model management tasks, and acts as a message broker between clients, sending model data back and forth between clients as needed. Finally, the Simulation Engine client application is a thick client that performs all calculations for both steady state and transient simulation runs.


Multiple Simulation Office clients on multiple machines can connect to the same Simulation Server to access different models or even the same model, in which case one user is always the Controller and any other users are Viewers. Users can switch controller mode amongst each other as needed. Single users on a machine with their own Simulation Server can also temporarily disconnect from their local Server and connect to any other visible Simulation Servers on the network. This feature can be used to remotely control unattended servers, but is also used to transfer models between users or between users and a master server that may contain master copies of the models. With Online installations, this feature also lets users reinitialize their local models using the latest calibrated and current state of the pipeline from the Online Server. Once a model is downloaded or updated from the remote server, the user can switch back to the local server to make local simulation runs. Other NextGen applications that may connect to the Simulation Server application as clients are the Scada Integrator, Data Integrator, Loads Forecaster, and Well Analysis Module.

Some of the advantages of the NextGen architecture include:

• Model data is kept on the server. • Multiple users can connect to the same model simultaneously for collaborative projects. • Experienced users with proper permissions can work directly with and update master models on servers

for others to use. • Users can make their own working copies of master models to run simulations on their own separate

Simulation Servers. • Projects (which contain Models) can be defined as either Public or Private. Public projects are visible to

other clients on the network, whereas Private projects are only visible to a Simulation Office client app on the same machine as the Simulation Server app.

• Models can be protected with passwords so only users with the proper permissions can access or change models.

• Model Configurations can be locked (operating set points can be changed, but piping and station configurations cannot) and the locked state can be password protected.

• Calculation tasks can be distributed among multiple machines and multiple threads per machine for running faster simulations.

• Simulation Engines can reside on local user machines, servers, or dedicated Simulation Engine machines. The Simulation Server can locate available Simulation Engines on your network/cloud and makes use of them as needed.

• User commands to control simulation runs are sent from user interface(s) to a Simulation Server, which then forwards those commands to the appropriate Simulation Engine. The Simulation Server maintains all connections between interface(s) and Simulation Engines.


Data Security For both security and performance reasons NextGen does not use standard databases for on disc data storage of models or archived historical data, and instead uses its own proprietary, unpublished, binary storage mechanism, and model files can additionally be password protected by users.

NextGen network communications also do not rely on commonly used protocols that are easily hacked, and uses low level TCP/IP and GEI’s own proprietary, unpublished, and encrypted binary protocol for messaging and data transfers over a network. In both cases, it would extremely difficult for hackers to extract useful information or data from model files obtained illegitimately, or from network traffic that was intercepted. In addition, NextGen contains a User Account Manager that can be used by IT to set security and

access privileges of NextGen users on the company network, so only authorized users can access NextGen, and among authorized users, only those with the proper permissions are able to access certain modules or features. Selected projects and models can also be made Private so that they can only be accessed from the machine they are on.

Managing and Creating Models When a NextGen Simulation Office interface is booted up, displayed on the Home tab are a list of NextGen Simulation Servers detected on the network, including the local one on the same machine, and users can easily switch from one server to another. Below that are a list of NextGen Projects that are accessible on that server, where each project can hold any number of NextGen Models. Then on the upper are a list of NextGen Models under the currently selected project. This Home tab is where users can manage and organize models, as well as archive and restore models. The archive/restore feature onto a USB flash drive is the easiest way to transfer models between users if they are not connected to the same network.


To create a new model, a user can start from scratch and use the interactive Pipeline Builder to manually build the model, or use the Import feature to import the model from an external file or source. Models can be imported or automatically built from the following sources:

• WinFlow Models • FlowDesk Models • GIS Shapefiles • Gregg Data Standard (database) • Excel Spreadsheets • Access Database (any data source including other vendors)

When a model is first created, the Steady State section is automatically activated. The Steady State section contains a map of the system and a variety of editors, graphs, and reports. A ribbon at the top contains buttons used to control most actions such as making runs or launching additional features or analysis tools. To activate additional simulation sections such as Sequential Steady State or Transient Predictive, the user can go back to the Home tab and use the Section Manager to activate or deactivate them.

Steady State Simulation (Gas and Liquids) In steady state simulation, a virtual pipeline is created and hydraulically solved to calculate systemwide pressures, flows, temperatures and other unknowns, where operating conditions do not change over time, so for example a steady state simulation might typically represent a daily average operation on a particular day. Steady State simulations in NextGen are time stamped so that they can be more easily integrated with time dependent external data sources. The steady state section in NextGen is also where models are created, and once created, additional sections such as Transient Predictive or Online can be activated. Steady State simulation is typically used to:

• Design new pipelines and pipeline expansions • Determine Optimum pipe sizes • Estimate horsepower requirements at compressor stations


• Calculate system and zone capacities • Determine viability of nominations and estimate allocations • Gauge impact of facility and system outages

Model Building Tools There are a variety of tools available to help build models in NextGen, with the most basic being the Pipeline Builder which lets users manually build models from scratch or edit the configuration of existing models. Each simulation section in NextGen (Steady State, Transient Predictive, …) contains one or more independent snapshots of the model, but all of the snapshots are synchronized so that they all have the same pipeline configurations. They all have the same pipes, node, valves, and so on, but the operating set points and calculated pressures and flows and other parameters may vary.

When a user enters into Pipeline Builder Mode, all sections are frozen while configuration changes such as adding new pipe sections or deleting some facilities are being made. When the user exits Pipeline Builder Mode, the changes that were made are propagated to all other

sections. Pipeline Builder Mode for a model can be password protected so that only authorized users are allowed to make changes to the configuration of the pipeline, but all users are allowed to edit operating set points, make runs, view results and so on. To facilitate the building of models, background imagery can be brought in first and the pipeline simply built on top of the imagery. NextGen supports online connections to Google Maps so that current satellite imagery can be displayed, but users can also import image files or shapefiles to be displayed in the background.


While building models from scratch is sometime necessary, NextGen provides a number of integration tools and modules that can be used to automate much of this process by bringing in the data from external sources such as geodatabases or GIS, and easy to use features to create and maintain the model data are also available:

• GIS Module • Elevations Module • Facility Library • Detailed Station Editor • Ariel Library Import Module • Excel Import/Export • Data Integrator Module • GDS Module • Load Forecaster Module • Load Generator Module • SCADA Integrator

Map Component The NextGen interface contains easy to use components to help create and edit models. The primary interface component is the Map which displays a schematic of the pipeline system, and it is the primary means of navigating through the model, adding or removing facilities from the model, and selecting objects for editing. There are a multitude of options and features to edit data directly from the map, display text on the map, color code objects on the map, create secondary map Views, add background imagery, and manipulate the model. The Map component is synchronized with the other components in the interface, so clicking on an object in the map will immediately display that object’s data in the Record Editor and auto-tab and auto-scroll to it in the Reports. Components in NextGen are synchronized so as to let the user immediately view the maximum amount of data possible for an object of interest, with no need to scroll or tab over to relevant data.

In addition to building and navigating through the models, the map is also a primary means of displaying model information. Hovering over any object in the map will display information on that object, right clicking will pop up an editor for editing its data. The Map can also be used to trace flow through the system. For example, click on a node in Flow From mode and find all paths where the flow from that node is going, or find all paths where gas came from that is arriving at the node in Flow To mode. Regions can also be defined either manually by lassoing, or by auto creating all pressure or flow isolated regions.

An individual region, once defined, can be turned into submodel. A submodel is a portion of the model that is basically split off from the main model and treated as its own smaller model. The flows and pressure set points


at the submodel boundaries are automatically reset to maintain current flowing conditions, and when runs are made, the run engine only solves the smaller submodel. When the submodel is deactivated, the boundary conditions are reset and it is merged back into the main system, but changes the user made while it was a submodel will be retained in the main system. Submodels are a good tool for debugging models and also let users make faster runs since they only need to run the portion of the main model they are interested in. Submodels can also be split off permanently and a new NextGen model created from the submodel.

Record Editor Another core interface component is a fully customizable Record Editor which displays detailed information about the currently selected object such as a node, meter, valve, section of pipe, etc. There is a default “View” that displays the most commonly used data, organized by Configuration, Set Point, and Results tabs, but users can define their own views and add additional tabs, and select what to display in each tab. Thus, novice users might be set up with a very limited “View” with minimal data such as flows and pressures, whereas experienced users might have much more data visible such as curve fit coefficients, components, or revenue data.

Reports The Reports component is another NextGen core Interface feature. At a high level, the Reports are used to view user selected simulation parameters. Reports are fully customizable and users can select what data fields should appear in the Reports.

Many features of the Reports component make it easier than ever to find and use your data. For example, quick column Sorting where a simple click of any column header in Reports will sort the report by that column with values ascending. Clicking the header again will reverse the sort to sort by descending values. Utilizing standard spreadsheet selection options, users can Multi-Highlight/Select more than one item in the Reports to view in the Map or globally edit in the Record Editor.


Users can also create logic and data Filters to only display records that adhere to user created logic rules. For example, only show nodes with a pressure greater than 500 psig. Reports can also be filtered by Region or Zone, so only those records that lie within the selected Region will appear in the Report. Data values that are alarmed or exceed operational limits are highlighted in the Report. As with most components within NextGen's interface, Reports are synchronized with the other components, so clicking on any node or leg in a report will automatically focus that object in the Map and the Record Editor, or clicking on an object in the Map will highlight it in its respective Report.

Individual Reports can also be exported to Excel or data in an Excel spreadsheet can be imported into a report table.

Custom Reports Using the Custom Reports Designer, users can create custom report templates that can include graphics, grids, and other custom report display fields that can be tied to the model data. When the report is generated, it is populated with the latest model data.

Gauges The Gauges component includes both gauges and simplified graphs and is designed to visually monitor key points of interest within the system. They are fully customizable so the user can choose what values are being gauged and what values are being graphed. The Gauges are provided for monitoring region-level variables, such as total supplies, deliveries, power in compressor stations, and line pack. The Graphs are provided for monitoring groups of variables, such as the greatest magnitude nodes of supplies, deliveries, or individual compressor stations. Both Gauges and Graphs have the option of defining high and low user-defined color bar ranges, to alert the user when certain limits or alarm levels are reached.

Profile Graphs Profiles Graphs display user selected values over distance, for example a pressure gradient chart showing how pressure drops over distance, steps up through compressors, and steps down across regulators. Multiple graphs can be defined and each graph will have its own tab.

3D Graphs NextGen 3D graphs can be displayed as either smooth terrain style graphs, or as stick figure 3D graphs, are useful to display values such as pressures or elevations.

GIS Module In many companies, pipeline models are created, in a sense, by hand, which due to most models’ complexity can be an extremely time consuming task. The GIS Import Module can automate this task by importing a model configuration that has been exported from the GIS system in the form of shapefiles and their associated dbf files.


GEI’s NextGen GIS Module is the industry leader in model creation from GIS technology, and has features that let a user control what data is used and how it is used, as well as features that will auto create connectivity if needed. Once this import process has been defined, it can be saved and reused for future model builds or for building other models. It can also be used to maintain, expand, and/or update models. The better the data presented into the GIS Import module, the more accurate and complete the model created is. Even if a company has minimal GIS data, maybe just a path of pipes, or even just a drawing of their system, the GIS Import Module is still a tremendous benefit. For example, it allows for the automatic creation of the majority of the model connectivity, including the correct length for each pipe segment since it

uses the scale within the GIS map to calculate this parameter. Creating the connectivity for a model is the most time consuming part of the model building process, and the GIS Module permits the user to do it in a fraction of the time. Using this feature, a company has the opportunity to gain back up to 99% of the work they would have previously done before by hand, as well as define a static and repeatable process for model building and maintenance. The GIS module not only has Import capabilities for building or updating NextGen models from GIS, it also has Export capabilities for updating the GIS from changes that were made in NextGen. For example, a user can bring in an incomplete set of shapefiles that have missing facilities, use NextGen’s model building features to add the facilities to the model, then export out a new set of updated shapefiles which contain the pipeline facilities that can be used to update the GIS.

Elevations Module Building a model with the GIS Import and correctly orienting it with the Google Maps Module will provide a solid foundation for an extremely accurate model. NextGen can then help complete the whole picture with the Elevations Module. Because NextGen models are geo-aware, NextGen has the ability to query a NASA generated database that comes with the Elevations Module and assign an elevation profile to each and every node in the model with the click of a button. Elevation profiles can be easily visualized in NextGen with either a 3D graph or a contour graph, both of which can also be exported out and included in reports. For pipelines with two-phase flow where both gas and liquid are potentially present throughout the line, it is essential to account for elevations. For these cases, NextGen offers both the Flanagan and Beggs and Brill two-

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phase flow equations to accurately correlate the model to the real world system. The Elevations Module also works hand-in-hand with NextGen’s AutoTune feature which helps identify areas of low efficiency, and thus suspected areas of liquid hold up.

Facility Library The Facility Library lets users predefine common elements that make up a pipeline, define common sizes and configuration parameters, and preset many of their set points to default values.

For example, different valve sizes and valve types can be preconfigured, different pipes sizes, and so on. When building or expanding a system that may have multiple copies of the same facility elements, for example a 6” globe valve, the user simply needs to select one of the preconfigured elements from the Facility Library, in this case the 6” globe valve, and

add it to the system where needed instead of having to renter the data over and over for each instance. Facility data can not only contain physical parameters, it can also contain set point data, and even cost information for Revenue Tracking such as the cost of the valve. Facility Libraries can be easily exported and imported, so one user can be responsible for creating and maintaining a master Facility Library, and all other users can simply import the master library as needed. The Facility Library also provides an easy method of automatically updating multiple elements in a model. For example, if the roughness of a 6” steel pipe was originally defined as 0.0005” in the Facility Library but the user wanted to change it to 0.001”, it would only need to be changed in the Facility Library and from the Library itself, the user has the option of updating all pipes in the model that were 6” steel pipes, or leaving them intact at the old value.

Detailed Station Calculations Module The Detailed Station Calculation (DSC) Module, used in both steady state and transient, is the most sophisticated and dependable station calculation module in the industry for modeling complex compressor stations. Compressor Stations are built using the Detailed Station Editor and can be set to Block Horsepower Mode to treat the entire station as a simple block horsepower (no detailed unit need to be created, but if they exist, they are not modeled), or set to DSC Mode in which case the individual units

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within the station are modeled. Several centrifugal and reciprocating unit types are supported from very simple to very complex, and they can be configured in simple parallel or series arrangements, or much more complex combinations of series and parallel. NextGen’s Detailed Station modeling simulates the actual detailed performance and operational limits of real physical compressor units within the pipeline network. The Station logic will perform both individual compressor unit selection and control of selected compression within a compressor station to maintain a desired “set point” value such as a discharge pressure, flow and certain other parameters.

The Station logic will choose the most fuel-efficient combination of compressors to operate for a given condition or to start compressors in a user-defined sequence, and calculates for each station the lowest cost combination of power, unloading condition and torque to maintain the desired pipeline pressure and loading configuration, while maintaining the operating limitations for each compressor unit.

Ariel Library Import Module Companies who have Ariel reciprocating compressor units frequently make use of the Ariel Performance Program from Ariel Corporation to both store the detailed unit information and perform detailed individual unit calculations.

NextGen can perform the same detailed unit calculations as the Ariel Performance Program within its station calculations, including modeling all the way down to the individual cylinder ends, considering bore, stroke, rod diameter, clearances, volumetric efficiencies, valves losses, pocket volumes, unloader steps, and so on for each cylinder.

The data required to model reciprocating units in this much detail can be daunting if it has to be manually entered, especially if there are hundreds of individual units. GEI created the Ariel Library Import Module to import all of the detailed data for all units directly from the Ariel Performance Program into the Unit Library in NextGen for use in NextGen models. The NextGen detailed Recip #3 unit type with its option flag set to “Ariel”, duplicates the calculations performed by the Ariel Performance Program so Ariel units running in NextGen will match up with unit performance in the Ariel Performance Program.


Making Steady State Runs in NextGen Once a model has been created, and the editors or data integration utilities used to properly set all set points, a user simply needs to press the Run button in the top ribbon toolbar to make a simulation run. For models that have trouble running, there are also Debug Run buttons that can be used to step through the steady state solution process. On each steady state iteration, the interface will display the results up to that point, and users can single step through each iteration and examine the results as they are being calculated.

There is even a View Differences button that will show the differences in calculated values between the last iteration and the current iteration, and let the user sort the data from highest to lowest deviations, which can be invaluable in identifying why the model might be failing or where it is blowing up due to bad boundary conditions. NextGen’s Simulation Engine client application contains all of the calculation algorithms for all simulation types, and any connected copy of the Simulation Engine can perform any of the steady state, sequential steady state, or transient simulation calculations that the Simulation Server might request. After a run has been completed, the Simulation Engine puts itself on standby for any subsequent run requests, and a Simulation Engine that has just been used by the server for one model, might then be used to solve another model. A core focus of NextGen is power, speed, and efficiency, and NextGen achieves this in the Simulation Engine by multithreading as many of the calculation processes as possible. This means that portions of the simulation calculations can be spread out among multiple cores. The Steady State and Sequential Steady State components of the run engine use a GEI developed Newton-Raphson solution methodology to set up equations that are then solved using sparse matrix LU decomposition. This proprietary methodology is custom built, and another piece of NextGen that allows GEI to stand out above others in the industry. Specifically, the equations and matrix construction have been built from the ground up to stabilize the solution and come much closer to a quadratic convergence, making use of certain characteristics unique to pipeline simulation equations and their behavior, as opposed to other vendors who typically just use generic Newton-Raphson network methodology that might be usable for pipeline simulation, but apply equally to electrical network simulation, or even stock market simulations. GEI’s solution typically converges in half the number of iterations found in other solutions, and difficult to solve models that are problematic for others easily converge with GEI’s methodology.

Advanced Features available in Steady State • Scenario Manager • Multi Scenario Runs • Automation Scripts


Advanced Modules available in Steady State • Component Tracking • Source Tracking • Revenue Tracking • Autotune for Pipeline Efficiency Tuning • Autotune for Loads Tuning • Portable Natural Gas (PNG) Module • Loads Planning Module • Well Decline Analysis and Forecasting Module

Transient Predictive Simulation (Gas)

Transient Predictive simulates a pipeline over time for shorter term periods such as 24 to 72 hours, but can be used for simulation periods up to a month or longer. Evaluates the time varying pressure-flow relationship for any piping network, simple and complex, either smooth or severe transients, using a finite difference solution methodology to solve conservation of mass and energy

equations. Transient Predictive simulation is typically used to:

• Model the true changing nature of compressible gas pipeline systems, and changes in available line pack over time.

• Design pipelines and facilities to handle peak hour demand and the variation of demand that occurs over a 24 hour period.

• Daily operational planning, perform operational studies to evaluate different operations over time. • Optimize and manage line pack build up and depletion over time to deal with intermittent large

industrial customer deliveries or peaking power plants. • Model changes in supplies or deliveries due to changing weather conditions or time of day fluctuations. • Model the impact of and plan operations for short term maintenance outages • Track pigs and develop pig operational plans for controlling pig velocities • Model blow downs and purges • Perform survival studies for large scale loss of supply or facility outages • Model leaks and ruptures, evaluate their impact, calculate gas lost, create operational response plans

All of the interface features described in the Steady State section are available in the Transient Predictive simulation including the synchronized Map, Record Editor, and Reports, but with some variations in functionality. These core component will display information on the current simulation time snapshot being viewed. In addition, two more core components are available for time based data entry and reporting: A Schedule Editor can be used to create more elaborate schedules (set point changes over time), and a Trends component displays time changing values in both graphical and grid formats.

Schedule Editor The Schedule Editor is used to create groups of time based set point changes, and each group of schedules can be enabled or disabled for a quick and easy way to select what groups of changes should be applied to the simulation.


Four different types of schedules can be created:

• Step Schedules • Ramp Schedules • Scheduled Events • Scheduled Profiles

Step Schedules approximate how a pipeline is actually operated, where a user might simply change the operating set point, and it is expected that pipeline model will try to achieve that set point as quickly as possible within the bounds of what is hydraulically possible, and within the operating limits of the facilities installed on the pipeline. For example, a user might reset the discharge pressure set point of a compressor station, but the horsepower limitations and other limits such as max rpm, as well as current pressures and line packs within the system will limit just quickly that set point can be reached. The NextGen transient model will closely mimic how the actual pipeline reacts to such set point changes.

Ramp schedules represent gradually changing values such as ground temperatures, ambient temperatures, or loads on the system. Events are local groupings of multiple changes that occur in a preset sequence, but the preset sequence is always the same. For example, one event might be the startup of a compressor station, where units are started up, a mainline valve is opened, another bypass valve is closed, and five minutes after that a recycle valve is closed, and maybe ten minutes later a nearby regulator is set to wide

open. Each of these changes can be stored as a single reusable named event, so if the user wants to start the station at 9:30am, he would create a single Scheduled Event to trigger that named event to start at 9:30am, as opposed to having to create multiple schedules every time the station needed to be started up. Events are created using the Event Editor and then scheduled in the schedule editor. Profiles are used to model predictable variations in certain values for modeling and forecasting purposes. For example, all residential loads typically follow a similar pattern, where the load is lower at night, higher during the day, with spikes in the morning when people are waking up and early evening when people get home from work, cook dinner, and so on. Industrial loads follow a different pattern, and commercial businesses also a different pattern. For forecasting loads, these standard profiles can be created in the Profile Editor and then applied globally to all loads that fit within the same category within the Schedule Editor. Profiles can also be used for daily variations in ambient air temperatures, or ground temperature variation during the year.

Interactive Schedule Changes When the user makes a change to a set point value in the Record Editor in Transient, in the background NextGen will create an Interactive Schedule to store that change so that it can be repeated if simulation is re-run. All


Interactive changes are stored in their own schedule group and can be viewed at any time in the schedule editor. Thus, as the simulation is progressing, the user may interactively change several set points, close or open valves, start up a station, or shut in or modify loads at different points in time, but all of these changes are being recorded as interactive schedules that can be viewed in the Schedule Editor, and will be repeated if the simulation is re-run.

Trends Component The Trends component is used to view time changing variables in both graphical and grid formats over time, and both graphs and grids are customizable so users can select what data to view.

Advanced Features available in Transient Predictive • Scenario Manager • Multi Scenario Runs • Automated Multi Scenario Runs • Automation Scripts

Advanced Modules available in Transient Predictive • Operator Trainer Module • Pig Tracking Module • Component Tracking • Source Tracking • Revenue Tracking • Leak Detection • Trainer Module • SCADA Based Trainer Module

Transient Online (Gas)

In Transient Online, also called Transient Real Time, a virtual model of the pipeline is connected to SCADA, and operates in tandem with the real pipeline, duplicating what is actually occurring on the pipeline in real time. The transient simulation input data is collected on a real time basis from SCADA and optionally from other additional sources. The online model calibrates itself

automatically to match up with the actual pipeline. Typically used to:


• View and analyze complete pipeline data over time: past, current, and future. • Fill in the data gaps, determine what is occurring at locations not monitored by or missing from SCADA. • Perform volume balancing to reduce unaccounted for gas. • Detect leaks or ruptures and warn operators of anomalies that might indicate a leak • Provide a well calibrated model and accurate current operating conditions as a starting point for

predictive studies performed by simulation users. Standalone Steady State, Sequential Steady State, and Transient Predictive simulations by multiple users on different machines throughout the enterprise network can be easily initialized from the Transient Online simulation so that the latest state of the pipeline is used in simulation studies.

Advanced Modules available in Transient Online • Component Tracking • Source Tracking • Revenue Tracking • Autotune for Pipeline Efficiency Tuning • Leak Detection Module

Transient Look Ahead (Gas)

Similar to Transient Predictive, but Transient Look Ahead simulations are launched automatically at prescheduled intervals to predict what will happen in the near future. Input data into the look ahead simulations can come from external sources, and is also generated internally. For example, the last 24 profile of a delivery might be applied on a prorate basis to a new nomination to forecast

what the delivery will be for the next 24 hours, or a forecasted delivery schedule for a power plant might be imported from Excel. Multiple Look Aheads can be run in parallel and in different frequencies. For example, a single 24 hour nominal operation look ahead might be launched every hour, but at the beginning of each gas day, three 48 hour look aheads are launched simultaneously, one using nominations, another using Load Forecaster projections, another using max contract values imported from a database. Look Aheads are typically used to:

• Anticipate operating conditions and understand what might happen under different forecasts for the next 24 or 48 hours

• Dispatch proactively based on likely projected conditions rather than reacting in crisis mode after the fact.

• Better deal with over capacity conditions or short term emergency situations.

Advanced Features available in Transient Look Ahead • Scenario Manager • Multi Scenario Runs • Automated Multi Scenario Runs • Automation Scripts


Advanced Modules available in Transient Look Ahead • Component Tracking, Custom Components • Source Tracking • Revenue Tracking

Sequential Steady State Simulation (Gas and Liquids)

Sequential Steady State simulates a pipeline over time for long term periods such as 5 year or 10 year periods, and uses a series of steady state simulations to calculate time steps since transient simulation for time ranges this large is unnecessary. Sequential steady state is especially useful for planning annual storage injections and withdrawals, or planning new

construction for gathering systems that are constantly expanding to connect to new wells. Sequential Steady State simulation is typically used to:

• Design pipeline expansions and help schedule expansion construction over time • Compare facility costs with capacities and forecasted revenues over time • Plan and analyze scheduling of storage field or storage tank injections and withdrawals • Incorporate gas and oil well production into a systemwide pipeline model

o New wells coming online o Old wells being abandoned o New lines being built to connect to new wells o Well production decline over time for single wells or groups of wells.

All of the interface features described in the Steady State section are available in the Sequential Steady State section, however there are some additional time based editors and components. These are identical to those in the Transient sections and are described in more detail in the Transient Predictive section.

Advanced Features available in Sequential Steady State • Scenario Manager • Multi Scenario Runs • Automated Multi Scenario Runs • Automation Scripts

Advanced Modules available in Sequential Steady State • Component Tracking • Source Tracking • Revenue Tracking • Well Decline Analysis and Forecasting Module


Advanced Features and Modules

Scenario Manager To explain the concept of scenarios it might be easier to simply explain how a simulation program would act without them. Let’s say a user creates a model, loads in a set of nominations, and makes a run. The user wants to keep those results for later review, but in the meantime, he is tasked with performing another simulation with those same nominations, but this time with one of the compressor stations shut down, and then a third simulation with the nominations increased by 10%, and in both of these cases he also wants to keep the simulation results for further review, and possibly for additional simulation runs. Without scenarios, the user would have to create three individual copies of the model and store each one separately. Now let’s say the user finds out that he left out a valve and a section of pipe from the model, so he needs to repeat the runs, but first he will have to add the valve and the pipe section to all three models, and re-run each of them, and he will have to keep track of three separate models on disc. Not that big of a deal when dealing with only three copies of the model, but what if there were dozens of them. In NextGen, the user does not need to create three copies of the model. He just needs to create three scenarios within the same model. Each scenario is stored as a totally separate simulation and is actually a complete copy of the model but it is synchronized with the other scenarios in the model. So when the user needs to add the missing valve and pipe section, he just goes into Pipeline Builder mode, adds the valve and pipe section, then exits Pipeline Builder Mode. At this point the valve and pipe will be added to all three scenarios automatically.

Multi Scenario Runs As an added bonus, when the user needs to rerun all three scenarios he could go to each scenario individually and run each one, but a faster option is to just use the Multi Scenario Run feature and press one button and all three scenarios will be run automatically. NextGen will even launch additional run engines as needed, and run all three scenarios simultaneously using three processor cores.


Scenarios offer a huge advantage in functionality, where users can easily create scenarios as working copies of the same model, copy selected data from one scenario to another, or make a full a copy of any selected scenario to create another. The Scenario Manager lets the user manage scenarios, create and delete scenarios as needed, compare scenario results, and launch Multi Scenario Runs. Scenarios can even be automatically created from an Excel spreadsheet using the Import/Export/Multi Scenario Run feature, with the data in the spreadsheet used to create the scenarios and populate selected data in each scenario. The scenarios are then run in a Multi Scenario Run, and selected results data exported back out to the same spreadsheet, all with a single button click.

Multi Scenario is Available is All Simulation Sections The Scenario Manager and Multi Scenario Run features are not limited to just the Steady State section, they are also supported in the Sequential Steady State, Transient Predictive, and Transient Look Ahead sections. The Multi Scenario Run feature is particularly useful in transient, since each scenario might take several minutes to run, thus the ability to spread out the multiple transient simulation runs in parallel among multiple run engines, and even run engines on other machines, can speed up the process considerably.

Automation Scripts Automation Scripts are custom VB scripts that can be run on the Simulation Server or in Simulation Office. Simulation Server scripts are used to manipulate the input data going to the run engine and are typically used for Online implementations. For example, a typical script may detect that the data quality for a valve status went bad, but we still need to know whether the valve is open or closed. The script can infer what it is by examining nearby pressures on the upstream and downstream sides of the valve, and then set the valve status accordingly. Simulation Office scripts on the other hand are created for automating tasks and can be launched as a command line argument or selected from a drop menu of available user created scripts. For example, a user might create a script called Calculate Max Capacity, and the script would open a model, create a loop to globally increment all supplies and deliveries by 1% increments and make repeated runs until the model fails, then back up one increment, make another run, export the results out to Excel, and then close the model.

Component Tracking Component Tracking in NextGen can track gas compositions, including energy content and specific gravity, throughout the pipeline system. Component Tracking includes a mixing algorithm on a molar weighted basis to calculate product mixing as gas is injected into the existing gas stream. The gas composition of inlet gas can be measured by a chromatograph, and imported into the model using any of data integration modules, or can be entered manually using the built in component editors. The following core gas components are supported and are also used in EOS calculations to calculate heating values, specific gravities, Z Factors, specific heats, Joules Thomson, and dew points:

C1, C2, C3, IC4, NC4, IC5, NC5, C6, C7, C8, C9, C10, H2, He, O2, N2, CO2, H2S


There is also a Remainder component that can be used to make up for missing components, and the user can add additional Custom Components. Component Tracking provides the following enhanced features:

• Detailed Compositional Analysis, 18 Core components, Remainder, and Custom Components • Calculation based on selected Equations of State (EOS) such as AGA-8, BWRS, PengRobinson,… • Dew Point Pressure and Temperature Calculations

Source Tracking Source Tracking is similar to Component Tracking except that the percentages being tracked do not represent mole %. Instead the percentages are strictly for accounting purposes. Any number of Sources can be defined, so the user might define 5 sources for one model, or 50 sources for another. The user can then provide the percent of each Source for each supply node or meter either manually or via an import, and the tracking algorithms will track the gas source percentages as they travel down the system and mix with other streams of gas. This feature can be used to track individual sources of gas, for example supplier A could have 100% of Source#1, and 0% of Source#2, and supplier B could have 0% of Source#1, and 100% of Source#2. The Source Tracking calculations will then tell the user exactly how much gas from each supplier arrived at every delivery location. It can also be used to track contracts or rate schedules. For example, Source#1 might be Firm, Source #2 might be Interruptible (and additional sources defined for as many rates as needed), and how much of each defined at every supply location, so that the user can then track how much Firm and how much Interruptible gas is actually traveling through various portions of the system and arriving at downstream locations.

Revenue Tracking The revenue tracking module in NextGen lets you track Construction Costs, Operating Costs, and even Revenues for a pipeline system. When combined with hydraulic modeling, this feature can be invaluable in estimating the cost and profitability of new pipelines, proposed pipeline expansions, and proposed contracts. Construction Costs, Operating Costs, and Revenues are tracked separately and are supported in all simulation types: Steady State, Sequential Steady State, Transient Predictive, Transient Online, and Transient Look Ahead. The easiest way to introduce Revenue Tracking into a model is to enter in revenue data in the Facility Library. For example, the construction cost for a 6” Globe Valve might be $1,800 (purchase cost and installation), and the maintenance cost $50 per year, construction cost for a particular class of 24” pipe might be $875,000 per mile, and so on.


Once all of this data is entered into a Facility Library, all users can make use of it to build new pipelines, or expand existing pipelines, or just run operating scenarios on the current pipeline, and all construction costs, operating costs, and optionally revenues, will be automatically calculated when Revenue Tracking is enabled. For the time based simulations, cumulative costs and expenses are also kept track of so that overall construction costs, operating costs, and revenues over time can be estimated. A Distribution company might use Revenue Tracking in Steady State to estimate construction costs for expanding their system.

A Midstream company might be modeling a gathering system in Sequential Steady State over a 10 year period, where new wells are being drilled, new pipe segments put into service, old wells being abandoned, and gas well production declining over time. The Revenue Tracking Module can be used to track constructions costs for each year, ongoing operating costs, and revenues from transportation or production. A transmission company might track operating costs and revenues generated by different contracts and different capacities in a Transient Predictive simulation or even in real time with an Online system.

Questions that can be answered with Revenue Tracking:

• How much is this new pipeline or pipeline expansion going to cost? • What are the estimated operating or maintenance expenses going to be? • What is the projected revenue stream if the system operates at 100% capacity? • What is the projected revenue stream if the system operates at 80% capacity? • What is the projected revenue stream (perhaps revenue loss), if the system operates at 60% capacity? • Given projected costs of gas, how much money can be made (or lost) over time by expanding the system

next year instead of two years from now?

Construction and Operating Costs and Expenses can be viewed for individual locations, the entire system, or broken down by defined regions within the system, and the complete revenue and expense stream is modeled so you can even see revenue streams traveling down the pipeline, which is why hydraulic modeling combined with revenue tracking provides a unique way of analyzing the profitability of a pipeline.

Excel Import/Export Excel spreadsheets can be used to import data into NextGen, as well as create entire NextGen models from scratch. The standard Excel Import/Export feature can be accessed from the toolbar in the Reports. Each worksheet in Excel can be used to represent a Table type such as Nodes, Pipes, or Valves, and each row in the worksheet represents a record such as a node, a pipe, etc.


Column headers simply need to be named using the same terminology found in the NextGen interface, such as Pressure or InFlow, and the Excel import feature will be able to import the data seamlessly on demand. Data can be exported out to Excel in much the same manner, as a matter of fact the easiest way to create a spreadsheet for Import that has all of the correct column headers and naming conventions is to first perform an Excel Export, then use the created spreadsheet as a base to create the Import spreadsheet. Data can be either steady state or time based data for transient or sequential steady state runs.

Data Integrator The Data Integrator module is used to import input data into models and export results back out from and to databases. It can connect to external ODBC compliant databases such as an Oracle or SQL Server (Stored Procedures and SQL are supported), Excel spreadsheets, and even CSV/Text Files. After this connection has been established, the data can be used for any number of purposes, such as updating a model with current nominations, or exporting simulation results to external business processes for additional analysis. The Data Integrator lets the user associate or link specific data objects in a table in NextGen to fields in an external database table. The external database does not need to follow any kind of special naming convention or schema since the links are individually defined. If on the other hand, the external database can be designed to follow the NextGen terminology and schema, then the GDS Module may be more applicable.

GDS Module The idea behind the Gregg Data Standard (GDS) is to have a well-defined bridge between a pipeline company’s processes (GIS, SCADA, or Nominations and Contract Management Systems, etc.…) and Gregg Engineering’s NextGen simulation products.

The Gregg Data Standard is a published database standard defining how pipeline data can be stored and be 100% compatible with Gregg Engineering’s NextGen Pipeline Simulation Suite. The database can optionally contain 100% of the data needed to seamlessly create simulation models and support all simulation features and functionality. This database, or just portions of the

database that will be needed, can be created through standard database utilities, but a complete or partial GDS database can also be created by NextGen from existing NextGen models. Gregg Engineering has developed tools on its side of the bridge in the form of the GDS Module that fully integrate available simulation features into the GDS database. Pipeline companies and/or third party data


integrators can use Stored Procedures or SQL Queries to integrate processes such as Nominations Systems, SCADA systems, or Geographical Information Systems on their side of the bridge into the GDS database.

Load Forecaster Module The Load Forecaster module allows a user to quickly and efficiently request a set of accurate loads for any required time frame. The Load Forecaster module can directly connect to weather services to obtain data, perform training and forecasting automatically, and use a series of forecasting algorithms to perform both long term (daily, weekly, and monthly) and short term (hourly) forecasting.

Forecasts are performed using any of three available methodologies, neural nets, genetic algorithms, or regressions analysis, or all three in which case the Load Forecaster keeps track of which method is more accurately forecasting a load and returns that method’s forecast. In addition, it has a built-in Historian enabling it to provide past actual loads to simulation models. This means that any simulation model can request loads from any time in the past or future and can expect to receive a set of accurate loads in return.

Thus, it is applicable for all NextGen simulation sections, including Steady State, Sequential Steady State, Transient Predictive, and Transient Look Ahead to model past or future expected events. In fact, the Load Forecaster is powerful enough that it can even be used to fill in gaps for missing SCADA data in Transient Online modeling.

Loads Generator The Loads Generator allows the user to predict the loads of a system for a given degree day utilizing consumption history. The user can rapidly change their NextGen and WinFlow models from one loading scenario to another without having to manually enter the loads or generate them using an external application. It analyzes the user’s weather and consumption file and performs regression calculations on the dataset and produces regression coefficients. These coefficients are then used to calculate the load for all locations for a given degree day. The produced loads file is then imported into NextGen or WinFlow where the user can analyze how the loads will affect the system.


SCADA Integrator The SCADA Integrator module allows the user to have quick, easy access to their SCADA data. The user does not need to go through the trouble of locating their SCADA data and then exporting, formatting, and finally importing the data into NextGen. By utilizing the SCADA Integrator, the entire process is performed automatically. Before any data collection can begin, a cross reference file must first be created that cross references each needed SCADA Tag with a NextGen Tag. NextGen will monitor data quality flags and only import valid data into the model.

The SCADA Integrator module runs continuously and uses OPC to connect to a SCADA system and download SCADA data at regular intervals. Typically, this is performed in one to two minute intervals, however, the functionality is completely customizable. The data is then accessible by any Online model section. The SCADA Integrator also creates its own historical database of SCADA data directly usable by other simulation sections such as steady state, sequential steady state, and transient predictive, thus the SCADA Integrator

can not only be used to drive an Online simulation, it can also be used to get historical data for Steady State or Transient Predictive simulations. The SCADA Integrator can also be configured to export simulation results back out to the SCADA system, allowing companies to use their own SCADA screens as an HMI to drive NextGen simulations.

Autotune for Pipeline Efficiency Tuning It is absolutely essential that pipeline simulation models accurately reflect real pipeline conditions, and in order to accomplish this, simulation models must be properly tuned and calibrated as often as possible. This is typically done by modifying the pipeline efficiencies in the various pipe segments throughout the model, so that predicted pressures and flow rates more closely match up with those found in the real pipeline.

This is a fairly straightforward process for straight line single pipe shotgun systems, and an engineer can usually make a series of simulation runs and, by trial and error, globally modify pipeline efficiencies in various areas of the pipeline until predicted pressures and flow rates match up with actual data. This process becomes much more difficult for more complex transmissions systems with multiple line services, or highly branched gathering systems where telemetry can be sporadic. In addition, it can become almost impossible for very large, highly interconnected distribution systems.

This calibration process can also be very time consuming and take up to several days to complete and, in some cases, calibrating the model is so difficult that it is simply not done at all or only a halfhearted attempt is made to properly calibrate the model.


The challenge in designing a solution is to have the calibration process work quickly, with a minimum amount of set up, support very large complex models, and be able to accomplish all of this using either steady state or transient simulation. NextGen’s AutoTune Module does exactly that, and can tune pipeline efficiencies for all model sizes and types ranging from gathering to distribution. Three layers of highly sophisticated optimization algorithms are used to recalculate individual pipeline efficiencies on each and every pipe segment in the model so as to best match up the model with real world conditions. Unlike typical Online transient tuning methodologies that work slowly over time, the NextGen Autotune feature quickly converges to a solution in both steady state and transient, and in many cases, is easier to use in steady state. Even very large LDC models which are typically too big to run in transient can be easily tuned. The user simply needs to import a handful of field pressures so they can be compared against calculated pressure, make sure that the loads used in the model match up with the loads that existed when those filed pressures were collected, and then run NextGen’s AutoTune. AutoTune will first establish major routes between the defined control locations (those with field pressures) and start modifying the pipeline efficiencies along these major routes to get a better match between field and calculated pressure. It will also diffuse those modified efficiencies into surrounding connected pipes, which is why it works well with distribution systems.

Typically, it might take 5 to 10 iterations to get an 80% improvement in the pressure deviations, and 20 to 30 iterations to get a 99% improvement, and in a matter of minutes (seconds for smaller systems), NextGen will have modified the pipeline efficiencies throughout the system to get a better match, in many cases a perfect match, between calculated and field pressures in the system. Resulting pipeline efficiencies can help identify problem areas in the model, but for two phase systems where liquids might be present, can also help identify where liquid hold up might be occurring.

Autotune for Loads Tuning Autotuning for Loads is very similar to pipeline efficiency tuning, but instead of tuning efficiencies, loads in different parts of the system are adjusted upward or downward using their InFlow Factor in order to get a better match between calculated model pressures and field pressures. This is especially useful for LDC models where the loads that are in the model might be last month’s metered loads, or loads generated from a degree day forecaster. Since the loads are estimated, they may not exactly represent the true current loads on the system.


Using Loads Autotuning, LDC models that are supposed to represent current conditions and will be used for operational studies, can first be calibrated properly.

Portable Natural Gas (PNG) Module Most LDC systems are designed so that Portable Natural Gas (PNG) supply points at predetermined locations throughout the system can be activated during maintenance outages or emergency conditions. Typically tanks of compressed natural gas or LNG tanks can be transported to these locations, and tied into the system so that they can provide additional supplies to meet demand. A number of tanks can be brought in and stored beforehand in any one location to meet expected demand, and as the tanks empty out, additional tanks can be trucked in as needed. When a maintenance outage is planned, or an unplanned emergency outage occurs, operators must determine which PNG points in the system need to be activated, and estimate how much flow each PNG point needs to supply based on the location(s) and severity of the outage(s). In the case of planned maintenance outages, engineers and planners have plenty of time to design an operation with certain PNG locations activated, and schedule supply tanks to be available and replenished at those PNG supply points. In the case of unscheduled outages that occur unexpectedly however, operators have much less time to determine what PNG locations to activate, and typically only have a few minutes to come up with a plan to minimize the possibility of customers being shut in. There are a variety of methods available to model PNG locations in NextGen, including Transient, Sequential Steady State, or Steady State solutions, but in determining the best solution methodology, execution speed can be critical. To get the fastest possible answer, and one that we know has to deal with worst case conditions, NextGen’s Portable Natural Gas Module uses a steady state solution methodology along with PNG supply point modeling features and optimization techniques to automatically find what PNG supply locations need to be activated any time customers are in danger of being shut in due to outages or emergency conditions. Each PNG location, if activated, will try and operate at the configured pressure set point, but if the supply flow needed to maintain that pressure starts to exceed the max flow limit, it will switch to flow control at the max flow limit and let the pressure float. Loads Planning Module and the PNG Module: NextGen’s Loads Planning Module, which can be used to plan ahead for worst case operations and to minimize load shedding when we know some loads will be lost, is intended to work with the PNG Module, so NextGen will first trigger all potential sources of PNG supplies prior to doing any load shedding for isolation zones or interruptible customers, and by the time we get to Load Shedding conditions in the Loads Planning Module, all applicable PNG locations that can help alleviate the situation should have already been activated.


PNG runs and Loads Planning runs can be set up to run automatically using the automated Multi Scenario Run feature in NextGen to test out a variety of possible solutions, so a matrix of different combinations of Enabled PNG supplies and combinations of different tank pressures, tank flows, and PNG locations can be imported from Excel and quickly evaluated. The Multi Scenario Run feature takes advantage of multiple run engines that can crank through the scenarios in parallel at a very rapid pace, so different scenarios or emergency outage conditions can be analyzed in bulk, with multiple possible solutions presented for each emergency outage. If maintenance of a database of operational actions for many potential emergency situations for regulatory purposes is required, for example what operation is appropriate and what actions need to be taken for leaks in each and every isolation zone, or loss of the regulator for each regulator in the system, NextGen can help auto generate these operational reports in bulk.

Loads Planning Module The purpose of the Loads Planning Module is to help LDCs plan loads to ensure that all delivery locations stay above their respective Minimum Delivery Pressures, and predict load losses during cases of outages or other emergency situations such as line ruptures.

If supplies into a system are limited due to outages or other emergencies, or deliveries are projected to be much higher than planned, or there is a rupture in the system, the Load Loss Prediction feature in NextGen can be used to predict exactly which loads in the system will wind up being shut in due to low pressure if no action is taken. In Transient simulation, load loss prediction is pretty straight forward since this is in essence a transient occurrence. The problem with Transient simulation is that it may not be feasible due to large system sizes and excessive execution times. Load loss prediction in Steady State is not that easy because we are trying to solve what is in essence a transient problem with a steady

state solution. NextGen’s Loads Planning Module, which was designed to work in steady state, solves this problem by using a combination of smart logic algorithms to predict loads most likely to fail first, optimization


algorithms, and a series of steady state runs in which loads are taken out and put back in as it converges to a solution. NextGen’s load loss algorithms start with the areas of the most severe minimum delivery pressure violations and work their way outward over a series of iterations to approximate what will happen over time before the system stabilizes. The Loads Planning Module has four modes of operation:

• Predict what loads (nodes and meters) will be lost if no action is taken • Derive a list of interruptible loads, from low priority to high priority, that can be preemptively shut in to

alleviate the problem • Derive a list if isolation zones that can be preemptively shut in to alleviate the problem • Let the user manually select isolation zones to shut in or put back in service

In cases where there is a rupture in the system, obviously we will need to isolate the zone in which the rupture occurred, but further losses may be incurred if the zone being isolated was being used to feed gas into other zones in the system, and the Load Planning feature can be used to not only predict what will happen when one zone is isolated, but also suggest other remedial action that may be taken to minimize the total loads lost.

Well Decline Analysis and Forecasting Module NextGen’s Gas Well Decline Analysis application is a standalone NextGen application lets you import historical data for up to several tens of thousands of gas wells, and will use curve fitting routines to derive decline coefficients for each well, or groups of wells, that can then be used to forecast production rates for wells. Given a future calendar date, the Gas Well application itself can perform a forecast of the projected production volume on that date, as well the total production since the startup of the well up to that date, for each well or group of wells. Those forecasted volumes can then be exported out to NextGen models, Excel, or any other application or database. This information can be used by Producers to estimate and forecast gas well production, and by Midstream pipeline companies to forecast flow rates coming from nodes and meters connected to one or more gas wells. The decline coefficients that are derived can also be imported into the Facility Library of a NextGen model, so that the NextGen hydraulic model itself can perform the same forecasts based on the simulation time for all of the wells that are in the model. In Steady State simulations, the well forecasts use the simulation datetime to calculate current production and cumulative production, and well decline can also be modeled in transient. However Sequential Steady State is the most useful simulation type to use for well analysis since the time frame is more in line with well decline time periods. For example, a user might use a 10 year simulation to model the decline of the wells in a field over time. Well Decline is also supported in the Transient Predictive section for shorter time periods.


By easily importing an Excel spreadsheet containing the historical values for each of the gas well flows, the application will plot the curves associated with each of the wells as they had performed over that time. You may be looking for a simple Exponential decline, or more likely the Harmonic, Hyperbolic for ARPS equations or the PLE equation. The application will detect the most recent restart date of the well, or wells, based on the data, then fit the data using all three ARPS methods and the PLE method, suggesting which one is the best to use for each well or well group. The user can also auto generate all coefficients for all wells, as well as customize those

wells that are hard to fit, by examining the data and manually adjusting the restart date, weight factors, and data filters. NextGen’s Well Decline Analysis Application can:

• Produce ARPS and PLE regression curve fits. • Advanced regression calculations. • Automatic scanning for restart peaks. • Gas Wells are grouped into individual projects for ease of management. • The Weight scaling factor can control what parts of the data the regression will attempt to fit. • Auto-Select will use the lowest MAD/Mean value of the ARPS or PLE equations. • Number of Points per Average allows the program to use a rolling weighted average to smooth out the

field data. • Standard Deviation Limit controls the point envelope that the program will look for restart points.

Pig Tracking Module The Pig Tracking in NextGen is a Transient feature which lets users set up, launch, and monitor pigs or inline tool runs. It is important to be able to properly control the velocity of pigs and NextGen can help determine and optimize what set points need to be set and maintained. Users can set up any number of pig runs in a simulation, where multiple pigs can be running simultaneously through different lines and launched at different time. Starting and end points are defined as well as launch times. Pigs are displayed on the map and when launched will be shown traveling down the pipeline, and are color coded to indicate whether the pig is yet to be launched, is in transit, or has completed its run. Pig Reports can also be exported to Excel, and will show launch and arrival locations, launch time and predicted arrival time, distance traveled, and predicted min, max, and average velocities.


A detailed section also contains predicted arrival times and other information at intermediate locations between the launch location and final arrival location.

Leak Detection Module NextGen’s Transient Leak Detection Module is a simulation based leak detection system. It is not just volume balancing as is found in liquid pipeline leak detection, which would only account for all the gas in and out, plus line pack or inventory change, NextGen also monitors line pack variations, pressures, changes in pressure, and the speed of changes. A single sign of a potential leak can be due to an operational problem or can be simply instrumentation error. NextGen’s Leak Detection Module does a system-wide analysis. A potential Leak is triggered by a population of pressure anomalies and mutually confirming anomalies. If there is a leak, the SCADA pressures in and near the leak will all be lower than the model pressures. To avoid instrument False alarming, the NextGen Leak Detection algorithms monitor the history, and if a pressure is consistently off, then the 6 hour average and 24 hour average anomalies should be about the same. Also, instrument noise levels can be globally or individually set, to prevent false alarming. Obviously, each network system will perform differently than others. The performance is highly depending on the instrumentation available, the locations of instrumentation and accuracy of the instruments. It is to the best interest of the client to have some historical operational data for fine tuning the leak performance before activating the Leak Detection feature in the production environment.


There are 3 key data Items to monitor or detect potential leaks or ruptures:

• Known Scada Pressure Points – if a SCADA pressure is lower than model pressure, maybe we are losing pressure due to a leak somewhere

• Known Scada Flow Points – if the metered flow rate is higher than the model flow rate, maybe we are feeding a possible leak

• Known Inline Check meters – if a monitored throughput at a point in the pipeline, a check measurement, is higher than model, maybe we are feeding downstream leak.

These are potential signs of leak formation. However, these signs alone do not always define the existence of a potential leak, which is why it is important to also include data filters and instrumentation error detection.

Trainer Module The Trainer Module is a simulation based trainer in which a Trainee uses the NextGen interface to operate a virtual model of the pipeline as if he were operating the real pipeline. Since hydraulic simulation is being used in the background, the virtual model will react to his actions in the same way that the actual pipeline would.

The NextGen Trainer is simply an add on module that lets companies create Training Scenarios, typically as Transient Predictive scenarios, but training scenarios can also be set up in Steady State or Sequential Steady State. Each Training Scenario can have a preprogrammed set of events that will occur during the simulation and needs to have a grading configuration preconfigured so the trainee results can be evaluated. Some scenarios might involve standard day to day operations, or maybe a sudden change in supplies or deliveries, or even a major rupture on the pipeline.

If NextGen Online is installed, an easy way to create a Training scenario is simply copy a 24 simulation period from the RTM Online model which will duplicate that 24 hour period. The Trainee can then override how the pipeline was operated to see if he can improve the operation. Trainees can select from any of the available scenarios, then start the simulation run, and interactively take appropriate actions such as modifying set points, opening closing valves, shutting in supplies or deliveries and so on. At the end of the simulation, which is typically an accelerated 24 or 48 hours, the Training Module will run through the results and derive a “grade” based on the grading configuration. Trainee names, the scenarios they ran, and their grades are logged and can be displayed in a report.

SCADA Based NextGen Trainer The SCADA Based NextGen Trainer is a more elaborate operator trainer implementation in which a background virtual pipeline model in NextGen Transient is connected to a SCADA system for two-way communications. The Training scenarios are still set up on the NextGen side, but the Trainee uses the SCADA HMI to control the simulation and view simulation results.


The SCADA Based NextGen Trainer requires more set up than the simple NextGen Trainer since it requires the establishment of links between SCADA data and NextGen model data, and typically the SCADA system itself needs to have a reserved HMI section for virtual model data that is separate from actual pipeline data. There is however a significant benefit in allowing operators to be trained using the SCADA screens they will be using on a day to day basis, and in which they can try out various operations, learn what operations work best, as well as make mistakes, without impacting the real pipeline.

nextgen product overview - gregg engineering product... · • steady state (gas and liquid) ......

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