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The Jatibarang (JTB) Field is one of the mature fields in onshore West Java. In order to maximize the value of future production, JTB requires more energy for drive mechanism to move oil in place and produce remaining reserves. The new development plan will use secondary and tertiary recovery to increase remaining reserves based on immiscible CO2 water-alternating-gas (CWAG) Enhanced Oil Recovery (EOR). The CWAG method will enhance productivity and increase recovery in the JTB Field both by providing energy for drive mechanism via displacement, and by increasing the mobility of the remaining oil using CO2. An immiscible CWAG is utilized in this scenario because of the high injectivity of CO2 compared to water and the ability of CO2 to develop solubility with the reservoir oil. Supporting this strategy, the integrated subsurface geology, geophysics & reservoir engineering (GGR) study team conducted reservoir characterization and simulation studies to optimize well placement and injection design. Based on the GGR studies, the combination of peripheral and inverted 5-spot pattern CWAG is the optimal scenario to optimize the recovery. The scenario results will be used for further surface facility design and project economy calculations.

Carbonate reservoirs, including the Upper Cibulakan Formation produced at JTB, are heterogeneous carbonate reservoir rocks by nature. The scale variety is caused by formation processes and complex diagenesis history. The subsurface GGR team integrated all available data including well test data, production data, cores, petrophysical properties, seismic data and study references to construct the reservoir model. The model was simulated from early in the life of the field, and has shown a good historical match with the production data. Some surveillance programs were conducted to validate and give a good confidence level of the model.

Results showed that a waterflood combined with CO2 water-alternating-gas from inverted 5-spot and peripheral patterns gave the highest expected incremental recovery until block expiry in 2036 with 3.11 MMSTB additional oil compared to the do-nothing base case. For this case, the net CO2 left in the reservoir at block expiry was 6.28 Bscf out of a total injection of 21.98 Bscf. It is recommended to further optimize the planned flood before implementation.