SUB-THRUST EXPLORATION PLAYS IN SOUTH SUMATRA BASIN, INDONESIA. CASE STUDY: SOUTHWEST JIRAK BLOCK

Jirak Field is a part of Gunung Kemala anticlinorium that has been producing oil for more than eight decades. Through borehole and new seismic data, this study will substantially evaluate the presence of sand reservoir distribution, hydrocarbon trap, and fluid content as integrated step out prospect analysis. Subsurface evaluation process in southwest Jirak is initially began through seismic interpretation based on regional tectonic and stratigraphic conceptual model of South Sumatra basin. Several representative borehole data from hundreds of existing wells in Jirak, Kruh, and Benakat Barat field are used to analyse Talang Akar sand distribution and reservoir characterisation. Amplitude Versus Offset (AVO) and seismic inversion are generated through seismic gather, s-wave, p-wave and density logs from well J-24 as main seismic attributes parameter input. Seismic image in Southwest Jirak sub-thrust block confirms a three-way dip structural trap geometry as different compartment from Jirak existing field. Talang Akar sand in sub-thrust Jirak block is laterally distributed as syn-rift deposits of fluvial deltaic-transitional depositional environment. According to seismic attributes, sand reservoirs in sub-thrust block have low impedance and class 3 Amplitude Versus Offset (AVO) anomaly. It represents relatively fair-good porosity reservoirs and also hydrocarbon fluid content in Southwest Jirak closure. © EAGE Conference and Exhibition 2021.All right reserved.