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Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 3–7, 2021

Paper Number: PSIG-2110

... impact on transportation

**efficiency**in terms of energy consumption as well as the impact on the transport capacity of a pipeline where the equipment was sized originally for natural gas transport, are assessed. Introduction and Background The increased use of renewable energy will require the...
Abstract

Abstract Both in Europe and in North America, the goal to use increasing amounts of renewable energy has created the need for electricity storage. One concept which aims to address this need is to produce hydrogen from surplus electricity, and to use the existing natural gas pipeline system to transport and store said hydrogen. Generally, the hydrogen content in the pipeline flow would be below 20%, thus avoiding the problems of transporting and burning pure hydrogen. The thermodynamic properties of hydrogen-natural gas mixtures, as well as their impact on the combustion process are briefly addressed. To assess the impact of hydrogen addition in various concentrations to a natural gas pipeline, a realistic pipeline system is simulated. The pipeline hydraulic simulation provides the necessary operating conditions for the gas compressors and the gas turbines that drive these compressors. The impact on transportation efficiency in terms of energy consumption as well as the impact on the transport capacity of a pipeline where the equipment was sized originally for natural gas transport, are assessed. Introduction and Background The increased use of renewable energy will require the capability to store energy to balance the large fluctuations in the availability of renewable energy, thus balancing supply and demand. Generating green Hydrogen from surplus electricity using electrolysis and transporting this hydrogen together with natural gas in gas pipelines is a method to provide storage and transportation for hydrogen [1,2,3]. Mixing hydrogen into natural gas pipelines requires a number of considerations regarding the compression of this mixture, the use of the mixture as a fuel for the gas turbines that drive the pipeline compressors, and the impact of pipeline capacity and transport efficiency. There are a number of other concerns, including safety concerns for gas compressor packages, and material issues related to hydrogen embrittlement on rotating parts like impellers, pressure containing vessels (like compressor bodies), and high-pressure pipes. [4].

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 14–17, 2019

Paper Number: PSIG-1906

..., but two poorly measured parameters. When DRA are used, there are two different approaches to identify DRA

**efficiency**distribution over a pipeline. For both of them first we need to identify how hydraulic resistance change over distance traveled by DRA in a pipeline. This is done similarly to the...
Abstract

ABSTRACT Presently one of the methods of increasing pipeline capacity is using the drag reducing agents (DRA). DRA are typically high molecular mass polymers that are added at very low concentrations to reduce the pressure drop necessary to generate a given flow rate in a turbulent flow. They can be used in case if building of extra loops or pumping stations is impossible or the need to increase pipeline capacity is seasonal. Scheduling pumping regimes and calculating the amount of drag reducing additive necessary to achieve the specified pumping parameters, requires a mathematical model. This paper proposes a method that allows to integrate DRA into a mathematical model of viscous fluid motion in a pipeline. The model takes into account the degradation of DRA as the agents travel forward the pipeline. This article focuses on the question of theoretical model adjustment to the characteristics of a certain pipeline. Using the nominal information about DRA (provided by manufacturers) generally leads to a strong error and some information needed for the modeling might not be provided at all. Thus, the model needs to be tuned to the real DRA characteristics and the main source of data are real measurements of flow parameters (pressures, flow rates, etc.). Methods of using operational pipeline data for identifying DRA characteristics are considered. The issues of data collection and further data processing are discussed. The results of comparing modeling computations with real data from operating pipelines are presented. The characteristics of these pipelines are very diverse: internal diameters vary from 0.4 m to 1 m, different DRAs are used, and different types of liquid (oils, oil products and gas-condensates) are pumped.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 14–17, 2019

Paper Number: PSIG-1911

... Factors influencing the available power at the power turbine output shaft include: Ambient Temperature Ambient Pressure Power Turbine Speed Inlet / Exhaust Pressure Losses Fuel Accessory Loads Relative Humidity Factors influencing the heat rate or

**efficiency**of the engine include: Load...
Abstract

ABSTRACT Many gas compressor stations use multiple gas turbine driven centrifugal compressors. In many instances, the units are not identical. The challenge is to control the units such, that certain operational parameters, for example fuel consumption, pipeline capacity or maintenance requirements, are optimized. The discussion includes the use and sizing of multiple units, the arrangement of units, the arrangement as push or pull compression, as well as examples of optimization strategies at various levels of sophistication, up to and including the integration of hydraulic and turbomachinery optimization. The benefits of methods that control compressors for the same turndown, or to control all gas turbines for the same load. This methodology can be derived and discussed for the case of identical machines, and will be expanded for the case where the compressors and their drivers are not identical. The control system has to rely on measurable parameters, but the system has to be reliable even if parameters that are not directly measured change during operation. The paper describes a variety of optimization methods, starting with a simple algorithm, then comparing equalization methods, and finally illustrating the capability of methods that combine turbomachinery optimization and the optimization of pipeline hydraulics. An example demonstrating the potential fuel savings of such an optimization is given.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 15–18, 2018

Paper Number: PSIG-1801

... acknowledgment of where and by whom the paper was presented. Write Librarian, Pipeline Simulation Interest Group, 945 McKinney, Suite #106, Houston, TX 77002, USA info@psig.org. ABSTRACT Predicting the

**efficiency**of a DRA is still dependent on the use of models developed through field tests. Two forms of the...
Abstract

ABSTRACT Predicting the efficiency of a DRA is still dependent on the use of models developed through field tests. Two forms of the model are widely used for liquid pipelines, one correlates Drag Reduction (DR) as a function of DRA concentration only, and the other correlates DR as a function of DRA concentration and Reynolds number. Both are pipeline and fluid specific, that is, have limitations to pipelines similar to the tested in pipe size and fluid property, and the former also has limitations in flow rates. This paper presents a comprehensive model in which three more variables are introduced - type of DRA, pipe diameter and fluid viscosity - in addition to DRA concentration and Reynolds number so the model applies to a variety of pipelines and a wider range of fluid properties. Field tests show that DRA degrades, or the effective concentration of a DRA decreases as it flows through pipelines. So, a DRA degradation coefficient was also introduced in the model as a supplement to the variable of DRA concentration. The type of DRA used for crude oils is usually different from that for refined products and, most of all, the difference in fluid viscosity, therefore in Reynolds number, is so great that it is hard to develop a model suitable for both crude oils and refined products, so a separate model is developed for the products. INTRODUCTION AND BACKGROUND Drag reducing agents or DRA have been used in the pipeline industry for decades to improve fluid flow in pipelines. They are any material that reduces frictional pressure loss during fluid flow in a conduit or pipeline. Pressure loss reduction is achieved by reducing the level of turbulent motion in the flow. Using DRA allows increased flow using the same amount of energy or decreased pressure drop for the same flow rate of fluid in pipelines. [1]

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 9–12, 2017

Paper Number: PSIG-1704

.... LZfGT ZT PhhGC PP eD P T CQ a a aUD DU b b 2 222 5.2 1 where: Q = Flow rate C1 = Units conversion constant Tb = Base temperature Pb = Base pressure D = Pipe diameter e = Pipe

**efficiency**PU = Upstream pressure PD = Downstream pressure C2 = Units conversion constant G = Specific...
Abstract

ABSTRACT Model calibration is the act (some might say "art") of adjusting model parameters in such a way that the model's behavior matches as closely as possible the behavior of the real-world system that it represents. In order to successfully calibrate a hydraulic model, certain hydraulic conditions must be known in order to have a defined calibration solution. Pipes that run parallel to each other (i.e. from the same upstream location to the same downstream location in roughly the same right-of-way) can pose serious difficulties to this requirement, especially when no inline flow measurement on any of the parallel lines exist, as the lack of knowing the exact flow distribution between the parallel lines means that the calibration problem either has no finite solution, or the finite solution is exceedingly difficult to determine. A potential solution to this problem involves utilizing multiple data sets. Each data set will have a particular range of possible solutions, and by comparing the solution ranges of multiple data sets, a single solution can easily be found. This paper will describe this method and provide examples with the intent of enabling the reader to apply the methodology to his or her own hydraulic calibration challenges. INTRODUCTION AND BACKGROUND Most engineers involved with hydraulic simulation are probably quite familiar (too familiar?) with the Darcy-Weisbach flow equation that describes head loss in terms of flow, pipe length, and pipe diameter. A form of the equation is shown below, as understanding the equation will be crucial to understanding the fundamental difficulty of calibrating parallel pipes.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 9–12, 2017

Paper Number: PSIG-1707

... basic hydraulic pump equations. Actual system

**efficiency**was used. Both maximum surge pressure and pressure rise rate are calculated each model time step. This same method can be used for other energy recovery systems hydraulic analysis. In this study, a high-pressure feed pump with a discharge...
Abstract

ABSTRACT The objective of this paper is to describe a method that simulates an energy recovery system (ERS), which exploits water hydraulic power to boost inlet flow pressure. The impact of pipeline pressure surge (water hammer) on water treatment units was investigated. Surge pressure and pressure rise rate were calculated. A novel methodology has been developed in this paper to simulate an energy recovery system and estimate pressure rise rate. This method integrated an energy recovery system into an existing pipeline simulation model. The energy recovery system model was developed using basic hydraulic pump equations. Actual system efficiency was used. Both maximum surge pressure and pressure rise rate are calculated each model time step. This same method can be used for other energy recovery systems hydraulic analysis. In this study, a high-pressure feed pump with a discharge pressure of 630 psig was analyzed. The model was used to calculate the maximum surge pressure downstream of the ERS. In this analysis, downstream of the ERS there is an RO (reverse osmosis) filtration system. The maximum pressure and rate of change of pressure must be controlled so as not to damage the filter membranes. Different surge scenarios were investigated. For the cases analyzed it was possible to keep the maximum surge pressure to 1117 psig that is below the maximum membrane design pressure. It was also possible to keep the maximum pressure rise rate for all cases simulated to below 5.2 psi/second. The membrane warranty for the cases analyzed limited the pressure rise rate to 10 psi/second and stipulated a maximum pressure or 1200 psig. The simulation results also provide design parameters for sizing surge relief devices and designing the required control system. Traditional surge analysis tools can properly estimate surge pressure within the pipeline system. However, energy recovery system behavior in a surge scenario was not simulated previously. The provided method can simulate energy recovery systems, calculate maximum surge pressure and pressure rise rate. The method sheds light on simulating energy recovery system and can be adopted for different simulation tools.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 9–12, 2017

Paper Number: PSIG-1708

... compressors. This requires an accurate, and computationally

**efficient**method to calculate the fuel consumption of a gas turbine driven centrifugal compressor system. This feature is available for any current pipeline modeling software. The issue, however, is in accuracy of the currently provided methods of...
Abstract

ABSTRACT One of the key goals of pipeline hydraulic optimization is the capability to minimize fuel consumption of gas turbine driven centrifugal compressors. This requires an accurate, and computationally efficient method to calculate the fuel consumption of a gas turbine driven centrifugal compressor system. This feature is available for any current pipeline modeling software. The issue, however, is in accuracy of the currently provided methods of calculations. Authors have found that errors in the leading software exceed 2-3%. More accurate computations would allow pipeline operator to increase system's throughput and also more accurately assess the station and pipeline fuel cost. A common requirement is to calculate the fuel flow of the gas turbine for a given compressor operating point. In this case, the compressor speed and power consumption (and therefore, the shaft power at the power turbine and the power turbine speed) are known. To accurately calculate the station fuel consumption the user requires the gas turbine performance data for each particular compressor station, considering the station's site conditions which include ambient temperature, humidity, and the site elevation. This information is often unavailable for the pipeline analyst, so one of the main objectives of this paper was to find universal set of data that would be able to provide most accurate fuel consumption for all compressor stations regardless their different site conditions. This paper presents the results of a study conducted for a compressor stations where two different methods were used to reduce the accuracy of compressor station fuel calculation down to around 0.25%. The first method relates to elevation correction and it uses engine data files that contain the fuel consumptions data for the sea level only. The basis for this method is that gas turbine efficiency doesn't change with the change of the site elevation assuming the same percentage of turbine's part load. The second method is a "Power Turbine Off-Optimum Speed" iteration process where the actual fuel consumption value is found using some iterations between power turbine optimum power and speed until the target value is found. As in the "Elevation Correction" method the only one set of turbine's sea level data is needed and can be used for any site elevation. The methods described avoid shortfalls of previous methods when dealing with Lean-Premix Low Emissions gas turbines, and are simple enough to provide a effective means to properly account for part load and off-optimum gas turbine performance at arbitrary operating conditions. Both methods can also be used to calculate the fuel consumption at any given ambient temperature by interpolating between two closest sets of ambient temperatures.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 12–15, 2015

Paper Number: PSIG-1510

... system volQ - adH . Exactly the same approach is basically used for the working space in

**efficiency**variables - volQ . and, parameterized by the**efficiency**values, also projected (and displayed) in the same invariant coordinate system volQ - adH . However, there have been new developments in design and...
Abstract

Abstract One of the necessities of a simulation software is to model the behavior of compressor stations. The main device modeled in a compressor station is a compressor. The article presented concerns mathematical description of centrifugal and axial compressors, the most frequently used equipment in the gas transportation pipelines or pipeline networks. Traditionally, both in the machinery industry and in the gas industry, these are mainly modelled using complete biquadratic polynomial approximation of the working space. The characteristics parameterized by the rotation speed values are then represented as 2nd-order parabolas in the satisfactorily invariant (relative to inlet gas status) coordinate system Q vol - H ad . Exactly the same approach is basically used for the working space in efficiency variables ? - Q vol . and, parameterized by the efficiency values, also projected (and displayed) in the same invariant coordinate system Q vol - H ad . However, there have been new developments in design and production area, and also the community of the user wishes - namely we are talking about axial compressors that contain several compression stages integrated internally. The characteristics of such devices can no longer be described precisely enough in the traditional simple way represented by 2nd-order parabolas, so better methods of modelling needed to be found. After some testing of various methods, we propose to model these compressors using linear interpolation approach, when the boundaries of a revolution working area are described using cubic splines and the working point parameters are found using linear interpolation within a small enough quadrangle defined by these splines. There are some challenges using this approach, namely a need to harmonize mathematically precise solution and possibilities of computers. Finally, we realized that the new approach is a bit slower to traditional one, but on the other hand, when comparing the precision, the result is significantly better in favor of the new model. In conclusion, with the advancements of technology, new ways of modelling need to be constantly devised. Our new way of modelling compressors is fast and robust enough to be rolled out to our customers in order to improve the model quality specifically for the compressors that cannot be processed in a traditional way.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 12–15, 2015

Paper Number: PSIG-1513

... thickness result simulation result exergetical analysis application reservoir surveillance

**efficiency**heat engine production logging midstream oil & gas transportation module exergy destruction piping simulation inlet temperature exergetical**efficiency**different insulation...
Abstract

Abstract The concept of exergy is defined and explained with the intention of its direct application toward pipeline simulation. Exergy is the actual useful work that can be obtained from any system, while irreversibility can be viewed as the lost opportunity to do work. All pipelines experience heat transfer and frictional pressure drop to varying degrees, resulting in entropy generation and a corresponding decrease in exergy, leading to less economical transport. An "exergetical" analysis can lead to design changes to improve overall efficiency, such as reducing pump or compressor power requirements while addressing environmental goals, such as avoidance of the melting of permafrost surrounding arctic pipelines, or lowering of carbon dioxide emissions. This paper intends in the first part, to provide the background of exergy and entropy generation and introduce the analysis of pipeline systems using the second law of thermodynamics. In the second part, an actual crude oil pipeline simulation is described where exergy destruction and carbon dioxide emissions are compared for cases of differing pipe insulation thickness. Introduction Current practice for pipeline design consists of conducting a thermal-hydraulic analysis (Menon & Menon, 2013) followed by an economic feasibility study. From a thermodynamic perspective the thermal-hydraulic calculations embody the conservation laws of mass, motion and energy, fluid properties and the transfer of heat. The conservation of exergy is the "first law". However for any process to actually occur the second law of thermodynamics dictates that this occurs in a certain direction. A process is said to be reversible if both the system and surroundings can be returned to their original conditions. The reality is that there exist irreversibilites during any real world process and the original conditions cannot be restored. These irreversibilities are typically friction and heat transfer and lead to the concept of entropy generation and the second law of thermodynamics which states that entropy generation is always positive for an irreversible process.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 12–15, 2015

Paper Number: PSIG-1517

... One of the primary purposes of computerized pipeline simulation is to assist midstream companies to troubleshoot existing systems and design modifications or new systems. The tools available to the industry today enable companies to analyze and make decisions quicker, more reliably and

**efficiently**...
Abstract

Abstract Midstream gathering systems present several unique pipeline simulation modeling challenges. The first, and most significant challenge, is that systems are not static. In fact, systems are constantly changing as new wells are added and depleted. One method of handling this constant change is to use geographic information systems (GIS) to build models. This requires the simulation software to be capable of importing and exporting GIS data, fix topology errors on the fly, convert 2D GIS data to 3D using digital elevation models, and display the models over geo-referenced aerial backgrounds. The second challenge is that gathering systems are often multiphase, enabling liquids and solids to collect in low spots or low velocity areas. In addition, gathering systems are often looped and interconnected. The combination of multiphase and multipath networks makes predicting flows and pressure drops difficult. In order to accurately portray how a system would react in the real world requires the simulation to be tuned often. Unfortunately, manually tuning a complex gathering system is practically unfeasible. Automatic tuning algorithms utilizing SCADA data to tune the model is likely the only reliable method to accomplish this task. This makes it possible to determine the location and severity of liquid holdup, hydrates, or salt buildup. In addition, simulation software can be used to debug new models by identifying incorrect geometry, equipment, or operational parameter model inputs. The third challenge is analyzing and understanding the simulation results. This requires the application to have both the ability to create 2D or 3D color simulation maps and graphs for visual interpretation, as well as, export the results into spreadsheets for further analysis. Introduction One of the primary purposes of computerized pipeline simulation is to assist midstream companies to troubleshoot existing systems and design modifications or new systems. The tools available to the industry today enable companies to analyze and make decisions quicker, more reliably and efficiently.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 12–15, 2015

Paper Number: PSIG-1523

... compressors engines and turbines power variation adrian alvarado specific gravity pressure ratio psig 1523 suction flow rate upstream oil & gas compressor pipeline system molecular weight operating point case 1 composition

**efficiency**gas composition flow rate variation...
Abstract

Abstract New growth in shale gas production has changed the nation's energy point of view in recent years while creating new challenges in processing and transportation due to differences in specific gravities, Wobbe Index, and higher heating values. New fluid properties are affecting the design and operation of pipeline systems and compressor stations; therefore, a good quantification of their effect on the operating conditions of typical pipeline systems and compression equipment is needed. Many compressor stations are reversing flow direction and operating with a different gas composition than what the station was originally designed to process. Using a pipeline simulation method, this paper will review the effects on the efficiency and performance of compressors when exposed to varying natural gas compositions as well as the effect on the pipeline losses. This paper will also include the case study results of a pipeline system and its associated compressor stations. Background and Introduction In recent years there have been significant increases in natural gas production from shale deposits throughout the United States. In an effort to reduce the cost of compressing, processing and transporting this shale gas, many compressor stations in proximity to these deposits are reversing flow direction and operating under new conditions. Principally, these compressors are operating with a different gas composition than that which the stations were originally designed to process. With the expansion of extraction from shale formations, primarily throughout the United States, natural gas found at the numerous locations vary in composition. There are currently shale gas reservoirs spanning the north and south regions of the United States including New York, Pennsylvania, Wyoming, Colorado, Illinois, Texas, Oklahoma, and New Mexico. Individual components, such as nitrogen, methane and hydrocarbons, within these gas compositions can differ by over 10% mol subject to location. Furthermore, the component quantities in different wells at the same location can vary by similar magnitudes. The nitrogen content of the Barnett Shale formation in north-central Texas, for example, has been recorded to vary as much as 7% mol from well to well. Carbon dioxide and other heavy hydrocarbons have been measured at different wells at the same shale formation and been found to differ by over 10% mol. The composition variety of multiple United States shale gas locations is presented in Figure 1 and Table 1.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 6–9, 2014

Paper Number: PSIG-1402

... as it does not address the actual conditions of the pipe, to include eccentricities, contaminants, joint interruptions, etc. To address these real-world impacts to flow, it is preferable to introduce a pipe

**efficiency**term to the general flow equation, as shown below. 5.0 2 122 2 2 1 5.2...
Abstract

ABSTRACT Calibration is an often-overlooked aspect of hydraulic modeling, but the impact of ignoring this potentially crucial step can be immense. It is not uncommon for significant pressure losses to be incurred in relatively small facilities that can often be glossed over as mere minutia when constructing a model. This paper will provide insight into the challenges faced while calibrating Access Midstream's Barnett hydraulic model and some of the solutions that arose during that process. There are a number of areas that can cause a model's hydraulic behavior to differ from that of the system it is attempting to represent. These areas include the following: Model Structure Model Integrity Measurement Data Integrity Hydraulic Integrity Flow Loop Handling INTRODUCTION Access Midstream is a publicly-traded Master Limited Partnership (MLP) that was spun off from Chesapeake Energy's midstream division in 2013. It has operations in 7 regions spread across 9 states with an average throughput of 3.8 billion cubic feet per day (bcf/d) and more than 6,700 miles of natural gas gathering pipelines. Access's Barnett assets include approximately 860 miles of gathering pipeline with a throughput of over 1 bcf/d. The system includes 24 compression facilities using more than 154,000 horsepower. The Barnett hydraulic model includes 615 receipt points (including Chesapeake well pads and interconnects with third parties) and 59 delivery points. For calibration purposes, data from over 2,500 meter stations are used, with most stations providing flow, pressure, temperature, and composition data.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, April 16–19, 2013

Paper Number: PSIG-1315

... no complete theory that explains this phenomenon, known as the Toms effect. In the course of the DRA flow in a pipeline the

**efficiency**of the turbulence suppression decreases, most likely due to breakup of the long molecular chains into shorter ones. In this paper a mathematical model of viscous...
Abstract

ABSTRACT One of the methods currently used to increase pipeline transfer capacity, when the option of extra loops or pumping stations is unavailable, is the use of the drag-reducing agents (DRA). DRA are long-chain polymeric compounds that reduce turbulent frictional losses. Nowadays there is no complete theory that explains this phenomenon, known as the Toms effect. In the course of the DRA flow in a pipeline the efficiency of the turbulence suppression decreases, most likely due to breakup of the long molecular chains into shorter ones. In this paper a mathematical model of viscous liquid motion containing DRA is proposed. The model takes into account the gradual breakup of DRA in a pipeline flow. The influence of DRA is considered as a dependence of hydraulic resistance coefficient on the DRA concentration; the DRA concentration in turn depends on a travel distance in a pipeline.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, April 16–19, 2013

Paper Number: PSIG-1320

... offsets and pipeline

**efficiency**. upstream oil & gas inventory equation operator accuracy predictive simulation james munro online simulation software application benefit offshore pipeline modeling & simulation garry hanmer modelled peak eta simulation gassco piping...
Abstract

ABSTRACT This paper addresses the main benefit of the new integrated Pipeline Management System (PMS) for Gassco's subsea pipeline network. The online simulation software is applied to the subsea single phase pipeline network of 7,800 km (4,847 mile) length. With the successful implementation of the simulation software integrated with the SCADA system, Gassco control room operators are able to run the complex networks confidently, reliably and predictively. A few real life operating scenarios will be used to demonstrate the commercial and technical benefits of the online software: Blending quality peaks passing a subsea mixing point using peak tracking Blending peaks after pressure levelling two pipelines using look-ahead (LAH) simulations Increased capacity utilisation using look-ahead predictive simulations Increased short term sales using look-ahead predictive simulations Notification of off-specification deliveries A comparison of some of the characteristics and typical settings of the new PMS and the previous system are presented to add understanding of how these benefits arise. To illustrate how the required accuracy of the PMS can be achieved without any subsea measurements, key aspects of the tuning mechanisms will be investigated: Network Model Calibration through the tuning of heat transfer to improve accuracy of calculated inventory and secure accurate ETA's. The use of the Maximum Likelihood State Estimation. Tuning of flow meter offsets and pipeline efficiency.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 15–18, 2012

Paper Number: PSIG-1205

... (Figure 1). valve multiple compressor compressor application kurz discharge pressure upstream oil & gas characteristic compressors engines and turbines midstream oil & gas

**efficiency**control concept psig 1205 gas turbine pipeline requirement suction pressure ratio...
Abstract

ABSTRACT: This paper explains the impact of the interaction between system characteristics and compressor characteristics, both under steady state and transient conditions, and the concepts to optimize and control the units. Process requirements for compression systems require the adjustment of pressures and flows through these compressors. Control concepts need to consider both the characteristics of the individual compressor, as well as the characteristic of the compression system. Multiple unit installations, or installations with multiple compressors per train require specific process control considerations to match the compressors with the process system behavior and the objectives of the station or system operator. INTRODUCTION There are two objectives for compressor control: meeting the external process requirements and keeping the compressor within its operational boundaries. Typical control scenarios that have to be considered are process control, starting and stopping of units, and fast or emergency shutdowns. The interaction between a compressor and a compression system, in conjunction with control mechanisms and the compressor characteristic determine the operating point of the compressor in a given situation. For the single compressor the application of these control functions is fairly simple. For compressor applications with multiple compressors in series or parallel, multiple compressors driven by a single driver, multiple compressor trains operating together, or multiple suction or discharge headers the combinations of these control strategies can become very complex. External process objectives can be minimum suction pressure, maximum discharge pressure, or delivered flow. Compressor operational boundaries include surge, minimum speed, maximum speed, and in some instances minimum pressure rise (choke). The operating envelope of a centrifugal compressor is limited by the maximum allowable speed (or, for other control means, the maximum guide vane angle), the minimum flow (surge flow), and the maximum flow (choke or stonewall), and the minimum speed (Figure 1).

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 15–18, 2012

Paper Number: PSIG-1207

... ABSTRACT:

**Efficiency**of a gas compressor package can be defined in several ways and it involves both the characteristic curves of compressor and driver engine and their match in speed and power across all operating range under different external conditions. A method of analysis is proposed and...
Abstract

ABSTRACT: Efficiency of a gas compressor package can be defined in several ways and it involves both the characteristic curves of compressor and driver engine and their match in speed and power across all operating range under different external conditions. A method of analysis is proposed and exemplified on compressor installations experiencing variable operating conditions. The method was used later in the design of an application robust to variations in operating conditions, this providing predictable distribution for efficiency early in the design phase. In this way the customer was fully advised how the performance will evolve during long term operation. INTRODUCTION The nominal point of a gas compressor package is specified with the main operating parameters: suction pressure, suction temperature, discharge pressure, flow, gas composition and ambient conditions. This information is usually provided by the customer together with other required characteristics. In addition, a number of extreme conditions like min - max suction and discharge pressure and flow can be specified in order to verify the extended operation. Most of the time the compressor unit is accepted if it meets or exceeds industry standards at the nominal point while still being satisfactory at the off design points. The compressor efficiency is typically presented at the design point where it reaches its maximum. The driver engine efficiency is also presented and guaranteed at the nominal power knowing that it will change with load and speed. From the combined performances of the two machines, the overall efficiency of the turbo-compressor package varies significantly at off design conditions. The costs incurred in operation are strongly dependent on compressor performance at design point as well as at off design points. In this paper the overall efficiency of a gas compressor unit will be evaluated in terms of the fuel efficiency.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 11–14, 2010

Paper Number: PSIG-1008a

...); .0011493 (Metric units) D Pipe diameter (inches) (millimeters) e Pipe

**efficiency**(dimensionless) f Darcy-Weisbach friction factor (dimensionless) g Gas specific gravity (dimensionless) L Pipe length (miles) (kilometers) Pa Average Pressure (PSIA) (Kilopascals) Pb Pressure base (PSIA) (Kilopascals) P1 Inlet...
Abstract

ABSTRACT The purpose of this paper is to describe the equations which govern the flow of compressible fluids through pipes. Particular emphasis is placed on those used within the natural gas industry in hopes that engineers within that industry can make knowledgeable decisions on how to model pipes. Its thesis is that all practical equations were created to solve intense numerical problems and have been made obsolete by advancing computing technology. It further discusses a new flow formula proposed by the GERG Research project 1.19 A NOTE CONCERNING UNITS These equations have generally been published in the English system of units. Where appropriate, alternate equations in metric units have been included, with the names of the metric units being shown in italic type. Since the Pole, Spitzglass, and Weymouth equations are included only for historical completeness, only their original published form is presented. 1. The Fundamental Equation During the almost two centuries that the natural gas industry has been in existence there has always been a need for workable equations to relate the flow of gas through a pipe to the properties of both the pipe and the gas and to the operating conditions such as pressure and temperature. The usefulness of such equations is obvious: systems must be designed and operated with full knowledge of what pressures will result from required flow rates. The purpose of this paper is to describe the ways that this has been accomplished and to provide some practical insight into what the current practice should be. Since nearly every text on fluid mechanics, and they are legion, contains some derivation of the fundamental equation governing one dimensional, compressible fluid flow, it is not necessary to repeat that derivation here. Excellent derivations are presented in the Hyman, Stoner, and Karnitz paper, the Gibson paper (the best), and the Finch and Ko paper referenced in the bibliography. Essentially one begins with the partial differential equations of motion along with the equation of state and then starts assuming and integrating. 2. The Equation of State A key component of the above flow equation is the equation of state that describes the volume that a given mass of a given gas will occupy at a given pressure and temperature. For an ideal gas the equation of state is well known, simple, and can be derived in a number of ways from first principles; for a real gas it becomes quite complex, depending on molecular size and shape, and inter-molecular forces. The deviation from ideality is usually expressed as the ratio between the real volume and the ideal volume; hence the intuitive term "supercompressibility", denoted by "z", implying that the real gas can be compressed more that its ideal counterpart.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 11–14, 2010

Paper Number: PSIG-1008

... ABSTRACT The use of an

**efficiency**factor to make pipe equations match physical reality is not a new concept - it's been around as long as there have been flow equations. It fell into some disrepute and was deemed unnecessary by some when sound theoretical equations for pipe flow began to...
Abstract

ABSTRACT The use of an efficiency factor to make pipe equations match physical reality is not a new concept - it's been around as long as there have been flow equations. It fell into some disrepute and was deemed unnecessary by some when sound theoretical equations for pipe flow began to replace the older empirical ones. Efficiency, however, is of more use that just fixing bad equations since it also is useful in adjusting specific pipes for problems and considering operational issues. A previous paper, A Tutorial on Pipe Flow Equations, presented at the 2001 PSIG meeting as a replacement paper in the wake of 9/11 but not published with the proceedings since it was too late, ended with the thought that pipeline efficiency was a valuable tool in calibrating gas models, more so than that of pipe roughness. Since then, I have received much verbal support from people within the industry but continue to hear comments that pipe roughness should be used as "the" tuning parameter. This paper builds on the original paper to explore the concept of pipe efficiency, its effect on flow equations, and its value as a calibration tool. Along the way some concepts regarding system design in the face of load variance within a day are also presented. Also some considerations with using the Panhandle equations that have been lost over time are mentioned. 1. Introduction and Problem Statement The flow of natural gas through pipes is well known in the literature and will not be re-derived here. For more details, please refer to the earlier papers referenced in the bibliography, particularly the excellent detailed derivation in the one by Susan Gibson from the 1981 PSIG conference. 2. Flow Equation Problems As stated above, all of the "practical" equations make some simplifying assumption about the variance of friction factor with flow ranging from constant values to explicit exponential functions. This gives rise to the fact that these equations are only valid within some range of conditions and must be corrected as conditions change. For example, my experience with the Weymouth equation has shown that at typical diameters around 20" and appropriate flows, efficiencies of 106% are often required to make the equation match observed data in a truly steady-state case. Since the forms based on the Moody Diagram surmount these problems, the remainder of this discussion, except for the following comments regarding the Panhandle equations, will deal only with the Colebrook-White equation, although its conclusions are equally valid for the GERG equation and its explicit forms. Therefore, this component of efficiency, e1, will be considered to be 100% or 1.00 since the equation should not need correcting. For those still using the Panhandle equations, either "A", "B", or some variant thereof, there is a further consideration that seems to have been lost in antiquity.

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 12–15, 2009

Paper Number: PSIG-0912

...

**efficiency**are also considered when calculating operational costs; moreover, some clues can be obtained after a systematic analysis of the working method in order to improve the pipeline operation in term of monetary savings. The success of these procedures should not mask the principal difficulty that the...
Abstract

ABSTRACT This paper is the result of a test case that evaluated various options to obtain economical solutions for the daily operation planing for the Enagas pipeline network in Spain. The exercise involved the building of a set of spreadsheet-based models, the automation, and the evaluation of more advanced techniques in search for optimal solutions. INTRODUCTION The constant increase in energy demands has led to problems of saturation on pipeline capacities in the Spaniard market. Enagas has made significant reinforcements to their gas transmission system giving a complex dynamic to its network. In light of these infrastructural developments, it is felt that some decision making tools could be implemented to support Enagas planning team to get their objectives minimizing risks. Whereas the physical elements of any hydraulic system are largely automated, the planning and operational tasks are still essentially relying on human experience and expertise. At the same time, management science has been developing solutions to models not covered yet by classical solving algorithms. The present work is part of a study about the feasibility of implementing decision making tools to support the daily operational activities of the gas pipeline company. Enagas team has already made an effort building a model for their planning and management tasks. As a result, a set of spreadsheets is used to model the daily gas volumes for a period of thirty days. The model covers hydraulic system boundaries and contractual restrictions as well. The Enagas operation team has to solve the model on a daily basis in order to find the best feasible solution to the daily changing restrictions. This manual search has had some success over the years and has encouraged Enagas to look for some automation in this field. The present work analyzes some possible solving methods for the Enagas spreadsheet-based model. To explore possibilities some prototypes were built accordingly to the algorithms proposed. The original spreadsheet-based model is analyzed in a progressive way from its simplest form and adding more complex restrictions/boundaries to make it more realistic. The testing process in a simplified controlled environment had a very positive outcome as explained in this work. Additionally some other models were tested in order to attempt a more complete approach. This way, machinery performance and efficiency are also considered when calculating operational costs; moreover, some clues can be obtained after a systematic analysis of the working method in order to improve the pipeline operation in term of monetary savings. The success of these procedures should not mask the principal difficulty that the decision-making team will encounter in the presence of a concrete optimization problem: the choice of an "efficient" method capable of producing an acceptable "quality" solution at the cost of a "reasonable" computing time. PROCEDURE AND RESULTS Background Everyday, the decision makers are confronted with problems of growing complexity in many technical fields, e.g. in operations research, the planning activities behind the operation of pipeline companies, the location of the best

Proceedings Papers

Publisher: Pipeline Simulation Interest Group

Paper presented at the PSIG Annual Meeting, May 12–15, 2009

Paper Number: PSIG-09A4

... control, maximum speed, and power available have been satisfied, other information can be determined: – Compressor speed – Compressor

**efficiency**, can the operating point be moved to a higher**efficiency**? – Surge margin – Discharge temperature – Gas turbine fuel consumption MODELING...
Abstract

ABSTRACT This paper describes the fundamental performance of gas turbines and centrifugal compressors (known as "turbomachinery"), and how to model them for pipeline simulations. Previous P.S.I.G. papers have described very well how to model gas turbine driven centrifugal compressors, using somewhat laborious curve-fitting techniques and/or table lookups. However, since the advent of Excel, the process of curve-fitting has become much simpler. Presented in this paper is a straightforward, simple and accurate method of modeling turbomachinery performance, which is Not specific to any manufacturer's performance curve format Is easily input into your pipeline simulation model Includes factors for contamination and degradation to more realistically predict the performance And, this paper also presents a template model of a gas turbine driven centrifugal compressor, which will accept curve-fit coefficients of your turbomachinery to simulate it in your pipeline simulation software. This paper explains how to use gas turbine and centrifugal compressor performance curves for your specific unit(s) in a pipeline simulation model, to predict their performance under various pipeline conditions. The two questions that will be answered are: What is the flow and pressure ratio capability? What is the fuel consumption? The methodology in this paper has been successfully used by Gordon Muster of El Paso Corporation to model several two-shaft gas turbine engines. INTRODUCTION What a gas turbine driven compressor model should tell us: There are three basic questions to ask of a turbomachinery model (at specified suction pressure and throughput): Will the compressor operate satisfactorily (is the desired operating condition on the curve)? – Is it over maximum continuous speed? – Is it on surge control recycle? Does the gas turbine driver have enough power available at the prevailing environmental conditions? What discharge pressure and/or throughput can be achieved at full power? Once the above basic questions have been answered, and all the restraints of surge control, maximum speed, and power available have been satisfied, other information can be determined: – Compressor speed – Compressor efficiency, can the operating point be moved to a higher efficiency? – Surge margin – Discharge temperature – Gas turbine fuel consumption MODELING ACCURACY AND COMPUTING EFFICIENCY Just how accurate is the modeling process? There are several reasons why we must expect that the predictions of any turbomachinery model cannot be exact: The vendors' performance curves for both the gas turbine and the centrifugal compressor are predictions of the expected performance of an average unit, in new and clean condition, in the factory test. Generally, the actual performance of new-and-clean turbomachinery can be expected to deviate from their curves by as much as 4%. The actual performance of turbomachinery will deteriorate with time, so it will deviate even more from the prediction curves with accumulating operating hours. The process of measuring actual performance on site as less than exact, so some deviation due to testing and measurement uncertainty is to be expected.