Abstract

Kaji-Semoga fields in South Sumatra, Indonesia, are oil fields with a gas lift population of almost 50%. Since there is no gas source available in Kaji-Semoga fields, both the gas lift and fuel system are dependent on produced gas from oil producing wells. Based on an overall review of the gas lift system, the flare is inefficient. Pressure Control Valve (PCV), which controls the flare, is opened when the gas lift pressure reaches 815 psig, yet only 800 psig is needed for a normal operation. The gas lift pressure usually exceeds 815 psig, hence gas is flared. On the other hand, compressor suction often drops below the safety level. To overcome this problem, KS-X (Telisa gas cap) is produced around 1-2 MMSCFD. The production of Telisa gas cap has a very negative impact on this formation, causing a decrease in reservoir pressure of 60% in just 4 years.

Since Telisa reservoir pressure has depleted from 900 psig to 400 psig, it is easy to inject excess gas from the flaring system. PCV is added to the gas lift system and is set at 805 psig to open. The current gas lift line at KS-X has also been modified to be able to inject the excess gas to the well via the installed gas lift valve. Based on the daily record, the injection system is able to save flared gas and reduce produced gas from Telisa Kaji by up to 1 MMSCFD. Both gas lift system and compressor suction pressure are also relatively more stable after injection.

It is concluded that the recycle-injection system is a proven and practical method to use in mature fields where there is no gas reservoir available as a fuel source. The system is able to save up to 1 MMSCFD of flared gas worth $8,000 per day (based on the local market gas price).

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