As one of gas field producers located in South Sumatra Indonesia, the S field produced 70 MMSCFD as its peak production. It is a high pressure and high temperature gas impurities of 30% CO2 and 100-ppm H2S. The field has been producing since April 2010, with current recovery more than 50% of initial gas in place. Utilizing initial estimated OGIP (Original Gas In Place), the gas deliverability was predicted to last only until 2022. There are high uncertainties in estimating accurate reserves value due to lack of reservoir data such as reservoir pressure and SCAL (Special Core Analysis). Therefore, additional information such as SBHP (Static Bottom Hole Pressure) survey data and well optimization are essential to be conducted to narrow the uncertainties in reserves estimation and gas deliverability.

Apparently, in 2018 and 2019 during CPP (Central Processing Plant) shut down for preventive maintenance activity, SBHP survey could be performed. Additional pressure data was utilized to update the OGIP analysis by combining several methods such as p/z analysis, flowing material balance, rate transient analysis and history matching of dynamic model analysis. The analysis shows conclusive result that there is significant increase in the OGIP and reserves, estimated 16% of additional gas reserves.

To support enhance gas deliverability, the production network model was then created to evaluate existing production method. This updated system analysis showed significant bottleneck at the existing production system that limiting the production rate from the wells. As part of debottlenecking endeavor, temperature survey on the production system was employed to overcome the limited availability of pressure survey points in the system. Furthermore, the successful debottlenecking activity combined with temperature drop analysis resulted in 20% additional gas deliverability.

This integrated evaluation and optimization also prolong the field lifetime until 2025. This paper describes some of the challenges and lessons learned during the evaluation and optimization in the high pressure and high temperature sour gas field.

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