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ABSTRACT: Sequence Stratigraphy and Hydrocarbon Potential of Offshore Southeast Korea

YANG, SU Y., J. H. HAN, and S. H. KIM, Korea Petroleum Development Corporation, Seoul, Korea

The sedimentary basin of offshore southeast Korea is located on the southwestern flank of the Ulleung Basin, a back-arc basin formed as a result of the opening of the East Sea (Sea of Japan). Major extension and subsidence occurred in the Miocene and a large amount of clastic sediments, transported from a southwestern source, filled the basin during this time. Shelf margins of this area are characterized by stable progradational shelf margins where progradation is not accompanied by syndepositional faulting or diapirism.

Seismic sequence stratigraphic analysis defines several depositional sequences and corresponds systems tracts. Sequences boundaries recognized by identifying and correlating erosional truncations, were used as bounding surfaces for sequence stratigraphic analysis. Maximum flooding surfaces are not easily identifiable because of the lack of downlaps on the paleoshelves and poor control of paleo and well-log data. Incised valleys, which played a role as sedimentary fairways during sea level lowstands and might be filled with sand as sea level rose, exist on the paleoshelves. Thick lowstand prograding wedges were deposited basinward of the shelfbreaks, showing oblique progradational configurations. The slope and basin channel-fan complexes underlie the lowstand prograding wedges.

The existence of incised valleys and prominent lowstand deposits in shelf setting, no structural deformation, and gas accumulations in the adjacent Dolgorae Structures permit us to predict a high hydrocarbon potential of this area.

 

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)