Compressors in Established Assets

Since operating conditions of oil and gas assets are rarely constant, system capacity is a dynamic value – its magnitude is affected by a variety of variable parameters. This complication is amplified greatly in systems reliant on centrifugal compression trains because these do not have a fixed performance, but instead operate within a performance envelope.

Quantifying the Issues – Life of Field (LOF) Analysis

Mirade not only understand in detail the design and performance of compression trains, but also how they interact with other elements in the production system and visa-versa. This makes Mirade particularly suited to developing, validating and operating system models involving compression plant. These provide the following deliverables:

With the output of their detailed analyses, Mirade develop full LOF (Life of Field) reports.

Identifying & Validating the Solutions

Through analysis of the modelling results along with the design attributes of machinery, plant and upstream elements, Mirade identify opportunities to:

Mirade develop action plans which may include short, medium and long-term actions. These may take the form of modifications to equipment as well as changes to set-points, control regimes and operating philosophies.

In all instances, by using the system model to compare post-change performances and capacities with the field-aligned baseline, Mirade are able to ensure that any CAPEX is justified by demonstrating increased revenue potentials.

LOF (Life of Field) reports based upon the current installation can then be expanded to include the timelines and rates associated with improved facilities. Mirade can complement these with CAPEX and change timetables to aid the asset owner’s planning processes.

Expansion Strategies

In the event that opportunities for increases in capacity are identified, Mirade are able to develop field expansion strategies – which may involve more than modifications to just the compression system. In some cases, a concept design study may be justified in order to determine the optimum solution which may involve a compression system revamp, reconfiguration or rewheel.

While centrifugal compression systems can accommodate a range of process conditions, when these have deviated too far from original design intent the compression system can:

• Become a critical bottleneck.
• Run in a regime that can compromise operability through:
  • Undue proximity to limiting control and alarm settings.
  • Excessive recycle.
  • Poor stage matching.

Through design investigations, production analysis, modelling and expertise in problem solving, Mirade identify whether operational and capacity problems are due to machinery / plant condition issues, or a limitation with the existing design. In the latter case, there are normally various opportunities to enhance plant operability and production rates through revamps, reconfigurations and rewheels.

Redesigns & Rewheels –Centrifugal Compressor Aerodynamic Design & Selection

Similar to the way in which Mirade enhance projects for the design of new compression facilities, their in-house centrifugal compression design capability also allows them to enhance projects involving compressor rewheels and revamps.

Since compression facility redesigns have to work within the confines of existing skids and casings, they can be challenging since the limitations imposed by their dimensions and other attributes must be accounted for. Mirade’s centrifugal compressor design expertise and their pragmatic approach greatly aids the navigation through the technical challenges presented by compression system redesigns.

For all machinery redesigns and rewheels, Mirade’s ability to derive application-specific and design-specific centrifugal compressor performances allows options to be rigorously analysed and proven prior to the selection of the preferred change option.

Mirade’s independence means that they are able to review and present all possibilities – as opposed to a machinery OEM who may be focussed on a new sale. Mirade can review changes to control, set-points and operating methodology that may yield benefits. These can be simulated and quantified alongside more substantial changes – from rewheels, speed changes or, in extreme examples where no alternatives are available, casing replacements. Mirade present a review of the technical, productivity, CAPEX and project risk issues associated with each option to allow a truly informed decision to be made.

Mirade’s knowledge of compression system design as well as the influence of process systems and upstream networks means that they are ideally suited to conducting availability and troubleshooting studies on such systems. Mirade are able to determine whether causes of problems are related to the condition of the machinery or if it is an issue with the design. This can prevent capital being spent on overhauls which will not fix the root cause, or on rewheels which may only deliver limited improvements.

Issues addressed by Mirade include:

• Poor availability.
• Recurrent failures.
• Operating instabilities.
• Start-up problems.

Mirade can execute their analyses based upon historian data or, where appropriate, may conduct a performance test on the machinery. Mirade’s performance tests are always preceded by a test plan which allows operating personnel to review and approve planned approaches.

Mirade’s system modelling capability allows them to perform analysis on associated plant. This holistic approach to compressor problem solving allows them to identify instances where root causes of poor availability or operability problems are actually as a result of influences of plant on compression machinery and visa-versa.