Abstract

The Bima field with an original-oil-in-place (OOIP) of 700 million bbls and 50 billion scf gas cap is the largest productive carbonate field in offshore N.W. Java. Field startup was in 1987 with 7 platforms in the north on primary production. The southern 2/3rds of the field is undeveloped. Bottom water and edge water influx, high oil viscosity (21 cp) and an extensive gas cap have created several reservoir management challenges.

A multi-disciplinary reservoir study was performed on the Oligocene-Miocene upper Batu Raja limestone formation at Bima to evaluate waterflood, gas reinjection and development expansion. The study integrated numerous disciplines (gelogy, geophysics, log analysis and reservoir engineering) into construction of a 3D fullfield model. Reservoir performance for 54 wells (20 horizontal) was history matched over the 3-year field life. Special simulator treatments required for Bima included logic for horizontal wells and electrical submersible pumps.

Simulation results indicate water injection into the oil rim and gas cap to be an effective waterflood approach towards minimizing gas cap resaturation. However, waterflood reserves are sensitive to injection timing since the current depletion rate is significant.

The model also serves as a long-term reservoir management tool having the ability to evaluate future development expansion and gas sales. For these evaluations, the model can track fluid migration during the field life. An enhanced understanding of Batu Raja depositional and diagenetic processes on the Seribu platform was also gained which has future exploration applications.