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ABSTRACT: Seismic Facies of Mesozoic Marine and Nonmarine Sequences, Shiwandashan Basin, People's Republic of China

ARMENTROUT, JOHN M., LEI-KUANG LEU, and JORGE J. FAZ, Mobil Oil Corporation, Dallas, TX

Integration of outcrop and subsurface geologic data with seismic facies analysis led to the identification of three exploration plays in Shiwandashan basin, southeastern China.

(1) Triassic Submarine Fan: Thick, elongate-mounded packages of variable-amplitude, discontinuous, nonparallel reflections occur basinward of the slope and are downlapped by prograding slope clinoforms. The mounded seismic facies is correlated with outcrops of Triassic marine siliciclastic turbidites that grade laterally into basinal mudstone/limestone couplets. This facies is undrilled.

(2) Triassic Shelf Carbonates: Thin, localized, high-amplitude, parallel reflections occur in retrograde succession at the top of the Triassic prograding clinoforms. These high-amplitude seismic facies are interpreted as carbonate facies and are correlated both with drilled carbonates and outcropping Upper Triassic shelf and shelf-edge reefs. Two generations of migrated liquid hydrocarbons have been recovered from the Triassic carbonate outcrops.

(3) Jurassic Fan Deltas: Thick northeast-southwest, bi-directional, downlapping, hummocky reflections of variable amplitude, and intersecting, northwest-downlapping clinoforms define a hummocky clinoform facies. This facies grades laterally to and is onlapped by moderately continuous parallel reflections. The hummocky-clinoform facies has been drilled, and consists of poorly sorted conglomerate and sand that correlates with outcrops of a Jurassic syn-rift basin-fill succession, interpreted to be fan-deltas grading laterally to sandy fluvial and shaly lacustrine facies.

The geochemical data suggests the Triassic-Jurassic section is a potential gas-prone play for the Lower Triassic submarine fans, and a potential oil-prone play for the Upper Triassic shelf and shelf-edge reefs. The overlying Jurassic fan-delta play is considered noneconomic because drilling has found only tight sandstone and conglomerate with no hydrocarbon shows to date.

 

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