Evaluation of hydrocarbon potential of source rocks in the northern Jeju Basin based on lithology and organic matter characteristics

초록

Source rocks play a critical role in controlling both the quantity and type of hydrocarbons accumulated in reservoir rocks. Nevertheless, evaluations based on drill cuttings can introduce significant uncertainties in assessing hydrocarbon generation potential due to the admixture of lithic fragments. To minimize these limitations, this study analyzed the distribution of mudstone and coal fragments in drill cuttings from G well and independently evaluated the organic matter characteristics of each fragment to precisely assess the source rock properties in the northern Jeju Basin. The late Eocene mudstone-dominated source rocks (GM1, GM2, GM3) exhibit Fair-Good hydrocarbon generation potential and are capable of generating both oil and gas. The early Oligocene mudstone-dominated source rock (GM4) shows Good-Very good hydrocarbon generation potential, favorable for oil generation. The late Oligocene coal-bearing source rock (GC1), despite containing less than 20% coal fragments, exhibits higher hydrocarbon generation potential than the mudstone-dominated rocks, and considering the maximum HI (HImax) of coal fragments, it can generate both gas and oil. Compared to the late Eocene source rocks, the Oligocene source rocks are thinner but have higher hydrocarbon generation potential per unit area, potentially resulting in greater total hydrocarbon yield. However, due to relatively shallowburial depth, they may not reach sufficient generation temperatures, which could limit the actual hydrocarbon generation amount.

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