Falling wellhead pressures drastically reduce the productivity and economics of a well. If there is a supply nearby of high pressure gas, the well productivity can be increased by using the high pressure energy in an ejector.
An extensive programme of laboratory tests and offshore trials has been carried out to prove and optimise ejector design for offshore application. This has included the use of "flexible" multiple nozzles to allow continued effective operation as well pressures reduce. Existing design methods have been significantly improved and embedded into user-friendly software, which has been validated against the results.
Ejectors were installed on two platforms in the Phillips operated Hewett Gas Field in the Southern sector of North Sea. Trials have proven very successful, with increases in gas production ranging from 15 to 25 MMSCF/D. In both cases a payback on investment of only a few weeks was achieved. Further opportunities for ejector installation are now being actively sought. Investigations for the use of ejectors for multiphase boosting are continuing.