Technology & Software Systems for Oil & Gas Production Systems

The design of oil and gas production systems, which includes a gas compression system, requires careful analysis to ensure that the effect of changing reservoir pressures, variable operating conditions and production rates are fully taken into account. This is because the declining pressures affect the capacity and performance of pipelines and processing facilities differently from that of a gas compression system. The design of pipelines and processing facilities (e.g. separators, coolers and TEG systems) are based on "peak flow rates" achieved during the "plateau period", when there is no spare capacity in the system. However, as the reservoir pressure declines and enters the "post plateau period", the production rate decreases when the processing facilities and pipelines have spare capacity. On the other hand, the gas compressors have spare capacity at the start and operate satisfactorily during the "plateau period", because the gas pressures and gas densities are higher - when compressors require less power, head and lower flow capacity. As the reservoir pressures decline during the "post plateau period", the compression power, the (volumetric) flow capacity and the head required increases sharply above the original design; the real production capacity of the system becomes "negative" and compressors become the bottleneck. Dr Akhtar, MSE's founder, recognised the mismatch between the design of processing facilities and the compression systems at the very start and has been involved in the re-design of compressors and processing facilities since its inception. MSE found that the commonly available technologies and software systems were good at designing the processing facilities and pipelines but failed to simulate the effect of varying pressures on gas compressor design and their operations. This shortcoming lead to too many compressor and engine failures, apparently caused by a range of problems such as pressure instabilities i.e. surging of compressors, high vibrations and high gas discharge temperatures etc. These failures could not be rectified by the conventional troubleshooting techniques or replacement of the parts and needed a completely different approach; a redesign of the compression system.

Development of Technologies

MSE has pioneered the development of new technologies and software systems which take into account the effect of changing reservoir conditions on the design of processing facilities and the design and operation of gas compression systems.

Compressor Design

The technology know-how for the design of compressors were proprietary and restricted to a handful of manufacturers. It was not possible to develop new compressor design or rectify the existing designs independently of OEM. With the support of an operating company, MSE developed a suite of compressor programs named "CENTRIF" for the design and optimisation of centrifugal compressors. The CENTRIF software system was extensively used and enabled the operating companies to carry out an independent design audit of installed compressors and optimisation of new compressors.

A Database of Compressor Design and Field Performance

Performance tests carried out in the field showed conclusively that the performance of compressors actually achievable in the field fell short of the original performance claimed by the OEM in the original design. Some of the shortfalls were attributable to changing reservoir conditions, whilst others could not be explained easily. Replacing the original compressor design with refurbished internals was tried time and time again, but did not always rectify the problem and the performance shortfall persisted.

MSE launched a Joint Industry Project (JIP) which looked into the details of compressor design and their field operation; a great deal of design and operating data was gathered into a large database. The project was supported by five Operating Companies and proved immensely helpful in establishing a baseline of the actual performance to expect from such machines in the field.

This information database is shared by the original operating companies and is applied by MSE Consultants when tackling problems experienced by operating companies on new and different projects.

GASMAN - Integrated Modelling of Gas Fields

The operating behaviour of the gas field with gas compressors could not be explained by the conventional process and pipeline simulation models. Changing reservoir conditions affect the compressor performance and processing facilities differently; this resulted in a mismatch between the reservoir forecasts and the actual production rates which could be delivered by field. The production was found to be limited by the compressor design and performance issues.

MSE's GASMAN software, a bespoke model of a gas field, which includes reservoir, pipelines, processing system and the gas compression system, proved highly effective in predicting accurate production rates, which matched with actual field performance over time.
GASMAN is a holistic model which simulates the impact of changing reservoir performance on the surface facilities, processing facilities and above all on the compressor performance and gas deliverability.

GASMAN has the unique ability to predict the performance of the gas field over a period of time. It simulates the effect of continual gas production over time by depleting the reservoir using rigorous material balance models and determines the "bottom hole" pressures and the flowing well head pressures against time. GASMAN's ability to produce flow and pressure profiles at every nodal point in the gas field system is extremely useful as it can be field tested and history matched.

GASMAN not only resolved many of the persistent machinery problems and failures encountered in gas fields, but also provided compressor re-design which optimised production rates and enhanced field deliverability.

Dynamic Simulation for the Transient Analysis

Compressors are dynamic machines and suffer from flow instabilities and surging which is very damaging to these machines and pipeline and systems that surround these machines. Frequenting surging must be avoided as it causes catastrophic failures resulting in prolonged shutdowns and high repair costs.

MSE has been involved in the resolution of many machinery problems and equipment failures caused by flow instabilities. MSE have developed rigorous bespoke models of the gas compression and processing facilities, which have been very effective in remedying the field operating problems. MSE models have since been extensively used on many new and older oil and gas production facilities which are now in successful operation.

Many of our customers rely on this proven technology and award us dynamic simulation studies time and time again as they have found them reliable and they would minimise risk inherent in the design and installation of new plant and compression machinery.

MSE Dynamic Simulation verifies the recycle valve sizes, opening times and interaction of processing and control systems of compression plants for a range of operating conditions and makes recommendations for risk mitigation.

GAS EXPLORER - Optimising Concept Design of new Gas Fields & Gas Storage Facilities

The Gas Explorer software system may also be used to develop a range of concept designs which can be tested using the software's capability to test the performance and production rates over an extended period of time. This software is aimed at developing a number of alternative design concepts in which all the key parameters can be varied to arrive at an optimised solution. The software, allows the user to vary the following:
 

	Number and location of wells
	Optimum time for installing compression
	Interconnecting pipelines and location of central processing facility
	Well performance and the effect of key variables such as K and H
	Compression power and compression system configuration
	Size and length of export pipeline

By varying all the above parameters it is possible to arrive at an optimised and cost effective solution for the development of a gas and gas condensate field and gas storage facilities.

Gas Explorer is extensively used during early project phases and in providing independent results for discussion and agreement between the shareholders of large projects.

MSE Software Systems

All of MSE technologies have been encapsulated into software systems. Our software systems have been continuously developed, maintained and field tested on hundreds of projects. MSE provides consultancy services which utilise our software systems and provide reliable, consistent and cost effective solutions.
A list of our main software systems is as follows:
 

	CENTRIF - Software system for the design and optimisation of Compressors
	GASMAN - Integrated model of the gas compressor, reservoir and processing facilities
	PMS - Testing the performance of gas compressors
	Dynamic Simulation - Transient analysis of processing and compression facilities
	Gas Explorer - Optimising Concept Design of new Gas Fields and their expansion
	Gas Turbine Test Bed - Testing gas turbine performance and emissions