Core (Oil and Gas) Ltd

Gas Compression Optimisation

Gas compression performance and throughput usually becomes more critical as an offshore asset matures.

Gas platforms in particular have increased compression duty requirements as depletion occurs.

Oil platforms that utilise gas lift become totally reliant on gas compression for good production figures. Gas compression uptime and throughput directly correlate with oil production volumes. Platforms without import gas systems are particularly prone to start up problems due to low compression throughput as wells are kicked off.

Oil platforms with declining gas profiles are challenged with the gas compression system having to operate continuously at low throughputs.

Therefore, efficient and stable compression systems are the cornerstone of good production and low flaring figures for all assets. Compression and gas turbine systems are usually the most complex systems on an offshore installation. Consequently, specialist assistance is usually required to support Operations personnel in ensuring optimum performance. Typical problems enountered include:-

• Instability between compression stages on the same train.
• Instability between parallel compression trains.
• Starting difficulties.
• Cascade trips - where a shutdown of one compression train causes a series or parallel unit to also trip.
• Instability due to slugging.
• Inefficient operation due to instability issues.
• Inefficient operation due to poor control system design/setup.
• Capacity restrictions due to sub optimal gas lift system operation.
• Surging of compressors during instability causing damage, downtime and flaring.
• Vibration of reciprocating compressors.

Careful design and setup of compression systems enhances production, stability, uptime and environmental performance. Opex reduction also occurs due to reduced unplanned failures.

Core personnel have extensive experience and expertise in solving compression related problems and gas compression optimisation. We perform a range of services from surge testing of new or modified compressor installations, throughput and stability enhancements to efficiency and operability improvements. We also have extensive experience of specialist vendor antisurge and loadsharing systems and are able to take an holistic approach to the entire compression system whereas equipment suppliers are constrained within their own supply boundaries.

Due to reduced produced gas volumes, a number of mature assets are now being provided with import gas systems. These systems present their own operability problems due to Joule Thompson effects and temperature control issues that occur during startup. Core can provide valuable design and optimisation assistance in these areas.