Seismic Facies Interpretation of Mesozoic Sequences, Shiwandashan Basin, China

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

Integration of outcrop and subsurface geologic data with seismic facies analysis identified three exploration plays in Shiwandashan basin, southeastern China:Triassic Submarine Fan: Elongate-mounded packages of variable amplitude, discontinuous, nonparallel reflections occur basinward of the slope and are downlapped by prograding slope clinoforms. This facies is undrilled. Basin modeling suggests the mounded seismic facies correlates with outcrops of Triassic marine siliclastic turbidites which grade laterally into basinal mudstone/limestone couplets.

Triassic Shelf Carbonates: Localized, high amplitude parallel reflections occur in a retrograde succession at the top of the Triassic prograding clinoform. These high amplitude seismic facies are calibrated with drilled carbonate facies and are correlated with outcrops of upper Triassic shelf and shelf-edge reefs that contain two generations of migrated hydrocarbons.

Jurassic Fan Deltas: Thick northeast-southwest bidirectional downlapping hummocks of variable amplitude reflections and intersecting northwest downlapping clinoforms form large mounds and grade laterally to moderately continuous parallel reflections. The hummocky-clinoform mound facies is calibrated by drilled, poorly sorted conglomerates and correlates with outcrops of a Jurassic syn-rift basin-fill succession. These Jurassic rocks are interpreted as fan-deltas grading laterally to sandy fluvial and shaley lacustrine facies.

The geochemical data suggest a potential gas-prone play for the Triassic submarine fans and potential oil-prone play for the stratigraphically shallower Triassic shelf and shelf-edge reefs. The Jurassic fan delta play drilled tight with no hydrocarbons.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)