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Abstract: Characteristics of Eastern Continental Margin of Korea and their Implication for the Hydrocarbon Accumulation

CHOI, BYEONGGOO, Korea Petroleum Development Cooperation

The detailed characteristics of the eastern continental margin of Korea are inferred from 2D and 3D seismic data and revealed the distinguished rifting features of the Ulleung (Tsushima) Basin in the East Sea (Sea of Japan). These features are including a break-up unconformity and syn-rift sediments which are well defined around the Basin margin area. The sedimentary fill of the Basin evolves from continental fluvial in the Paleogene through to marine in the Neogene. Fan delta is one of the dominant feature during syn-rift stage and prograding delta is in the post-rift stage. The NNE-SSW trending extensional faults which are associated with pre-rift sediments hare normal movement, and the faults which are developed during the post-rift stage have strike-slip movement Some of the initial rifting faults have been rejuvenated by the strike-slip movement in many case.

Hydrocarbon exploration of the Ulleung Basin has been mainly concentrated in the structures associated with the uplifting and wrenching. Eleven wells have been drilled related to the structures in the Basin. Of these eleven, five have contained encouraging indications of gas condensate accumulation and significant gas shows were recorded in one well. Hydrocarbon potential associated with pre-, syn- and post-rift sediment around basin margin are not tested by exploration wells but recently defined by 2D and 3D seismic data. Pre-rift sediments can be correlated with Cretaceous lacustrine elastic deposits which are well exposed on southeastern parts of Korean peninsula. Syn-rift sediments have high potential for the hydrocarbon exploration and have a distinguished feature, separated from post-rift sediments by a break-up unconformity. One of the syn-rift sediments has been interpreted by 2D and 3D seismic data and it reveals its magnitude as 30 sq. km in area and about 1000m in thickness. Post-rift sediments have various trapping types and pinch-out is one of the dominant around the Basin margin area.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah