On-Shelf Lower Miocene Oakville Sediment-Dispersal Patterns within a 3D Sequence Stratigraphic Architectural Framework and Implications for Deepwater Reservoirs in the Central Coastal Area of Texas

The sequence stratigraphic architecture of the lower Miocene Oakville Formation along the central part of the Texas Gulf Coast that is revealed in 3-D seismic data and wireline logs shows four third-order sequences—the lower two containing lowstand, transgressive, and highstand systems tracts and the upper two containing only transgressive and highstand systems tracts. The sequences average 1.2 m.y. in duration, and the lowstand incised-valley-fill sandstones are massive and as much as 420 thick. Seismic stratal slices demonstrate that the incised valleys are dip oriented and more than 20 mi wide. Strata within the incised valleys onlap sides of the channel. The incised-valley fills have been interpreted by past authors to have been deposited in a shoreface depositional system that produced strike-parallel sand bodies. The transgressive systems tract comprises backstepping fourth- and fifth-order sequences. Seismic stratal slices and wireline-log patterns within the transgressive systems tracts suggest deltaic sediment dispersal patterns that are generally reworked. Highstand systems tracts comprise aggradational to progradational fourth- and fifth-order sequences, and seismic stratal slices and wireline-log patterns indicate a variety of depositional environments, including deltaic, shoreface, coastal plain, and interdistributary. The highstand systems tract is significantly truncated by the overlying sequence boundary. Sandstone-rich, incised-valley fills suggest that large amounts of sediment may have been transported through these channels to the shelf edge 20 mi seaward and delivered to basin-floor-fan, slope-fan, and prograding-wedge lowstand systems.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California