Bentu and Korinci Baru Block: Geophysical Consideration to Assess Thin Shallow Gas Sands in Central Sumatra Basin

The Bentu PSC and the Korinci Baru PSC are located in the Central Sumatra Basin. Shallow gas-bearing sandstones in the Korinci & Binio formation are the main exploration and exploitation objective due to high local demand for gas. The thin sands are 600-2000 feet below sea level, and contain up to 350 bcf of gas reserves. The formations were deposited in transitional - coastal environtment that reflects the transgressive and onset of marine regression. The gas is trapped along a NW-SE anticlinal system related to reverse faulting. Many horizons exhibit strong amplitude anomalies or bright-spots in the Post Stack Seismic data. Logging and testing have confirmed that whilst these bright-spots can be associated with gas reservoirs, they can also be caused by coal and tuning thickness. Further geophysical analysis was performed in an effort to reliably identify the gas reservoirs. The analysis comprised Bright-spot anomaly extent, tuning thickness, Acoustic Impedance (AI) and Amplitude Versus offset (AVO). Of these methods, the bright-spot anomaly analysis and the AVO evaluation were best able to distinguish between coal and gas-bearing reservoirs. They will be used to reduce exploration risk in the area.