Integrated Reservoir Management Strategy in Sisi Nubi Mature Gas Field to Unlock Reserves and Production Optimization

Sisi and Nubi are two gas fields located in the Mahakam Delta, 25 km offshore the modern Mahakam Delta to the east, in 60-80m of water depth. Sisi was discovered in 1986 and Nubi in 1992. The fields have been in production since November 2007 from 5 wellhead platforms. Peak production reached 450 MMscfd in 2010, and by the end of 2019 the average production is 150 MMscfd with cumulative production around 1.28 Tcf of gas and 31.3 MMstb of condensate. Having gravel pack and tubingless as well completion in Sisi Nubi leads to several limitations such as some reservoirs were not perforated due to Gravel Pack (GP) technical limitation or are not accessible due to some restrictions such as bridge plug and sediment. Building a simple yet vivid and properly integrated reservoir management strategy was done to tackle the aforementioned issue. The work was to map the remaining potential as well as production risk of both perforated and unperforated reservoirs and to develop the integrated production and development strategy for Sisi Nubi’s optimum’s production and recovery. The works involved multi entities; geoscientists, reservoir engineers, well intervention, and also the well performance team. Up to 2000 meters of unperforated reservoirs within 664 intervals, have been thoroughly studied, covering detailed geological correlation at reservoir scale, initial and current fluid status, driving mechanism, current pressure estimation, and reservoir-level volumetric calculation. Well obstacle classification based on the difficulty level to re-access perforation targets as a well strategy to produce reservoirs were performed in joint coordination with the well intervention team. The final deliverables are selected candidates that qualified both technical criteria and stakes were proposed for execution. An increase of Fifty-five (55) Bcf of stated reserves from existing wells have been booked thanks to this work. In addition, having the systematic strategy allows optimum offshore intervention barge planning.