Publications

The major reservoir within the North Madura Platform is the Oligo-Miocene Interval, which consists of oil and gas-bearing reservoirs, with multiple reservoir layers and multiple hydrocarbon contacts. The interval comprises of a stacked high frequency cycles of mixed carbonate-siliciclastic lithology component sitting in the paleo-high. It has become very important in the context of hydrocarbon accumulation since the components play very dissimilar roles and become reservoir-seal pairs, which resulted in the existence of intraformational seal. Based on the carbonate to siliciclastic ratio, from deeper to shallower interval, it can be divided into three cycles, namely first cycle with carbonate-dominated interval, second cycle with mixed carbonate-shale interval, and third cycleconsists of massive carbonate sequences. The vertical hydrocarbon migration, both oil and gas, occurred within the known trap in the study area, filled the reservoirs from deeper to shallower interval with subject to seal capacity of each intraformational seal and leak points in the trap. The first cycle consisted of oil indicated that the seal breached as reservoir become fully saturated and some of oil and most of the gas leak. The second cycle, which consisted of multiple reservoir-seal pairs with oil and gas being accumulated depending on the seal strength. The third cycle, which is massive carbonate reservoir, is capped by thick marine shale as a roof seal that has been proven for gas being trapped. Better understanding on intrafomational seal, both micro and macro characteristics, can be highly beneficial to identify potential overlooked zone as well as contributing to the proper judgment on the likelihood of hydrocarbon accumulation.