Petroleum system modeling of the Sora basin, offshore southern Korea

Petroleum system modeling was performed on the Sora Basin located in the northeastern tip of the Jeju Basin, offshore southern Korea to understand generation, migration, and accumulation of hydrocarbon. The Sora Basin has geologically essential elements of petroleum system, including source rock, reservoir rock, seal rock, and overburden rocks. 1-D modeling indicates that hydrocarbons are generated from the lowermost Eocene source rock, and expelled actively from the source rock that is situated within the depocenter of the basin. 3-D modeling shows that hydrocarbon migrates northwest and east toward the margin of the basin. 2-D modeling was carried out on a seismic section across the entire basin to clarify generation, migration, and accumulation of hydrocarbon in the Sora Basin. The result of 2-D modeling indicates that hydrocarbon begins to be expelled from the source rock and migrates actively upward at 28 Ma. The migration mainly occurred along the faults developed within the basin. In addition, the formation boundaries also act as lateral migration paths. A significant amount of hydrocarbon, which failed to be expelled, still remains in the deep source rock although hydrocarbon generation continued as burial depth increased. Additional 1-D model was also made on a pseudo-well drilled at a pod of the source strata. The result shows that timing of generation and expulsion of hydrocarbon is well coincident with the 2-D modeling result. All the modeling results in this study could be validated by the oil and gas shows observed during the drilling work. A huge amount of hydrocarbon, however, may not be possible to be generated from the source rock due to small size of basin and low degree of burial. Consequently, the hydrocarbon accumulations would be relatively the small-sized in the basin.