As the gas producing wells in North Sea decline, the available wellhead pressures drop. This mostly affects the operation of process equipment such as Amine coolers which need high gas pressure for efficient operation.
As a consequence, compressor modifications, generally utilizing a rerouted existing export compressor to become an LP compressor to boost the incoming gas pressure, are being implemented. This is an effective solution that has the potential to significantly extend the life of the asset.
With this modified configuration, it is vital to ensure that the LP compressor does not run ineffectively in full recycle, yet many assets were never designed to include metering of the discharge flows built in to the compressor discharge pipework.
Without this key metering facility it is difficult to determine the actual discharge flow from the LP compressor and the associated efficiency. Relying on pressure control valve positions and other unconventional flow techniques to infer flow is not acceptable.
On initial commissioning, the flow can be obtained using a control algorithm, based on the flow characteristics of the recycle valve but as the valve wears, this method of measurement becomes more unreliable with time. The solution is to use a non-intrusive gas meter that can be installed without piping modifications or loss of production. This greatly reduces the cost of implementation and eliminates any equipment integrity issues, resulting in no risk of loss of containment or hydrocarbon release issues.
ABLE Instruments has successfully provided a clamp on Ultrasonic gas meter solution for this application with proven excellent accuracy and reliability, which has greatly assisted with the smooth implementation of compressor reconfiguration projects.
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