Abstract: Exploration Targets in a Lower Miocene Lowstand Deep-Water Sand Play, Matagorda Island/Mustang Island Areas, Offshore Texas

Dennis W. Cratsley, Thierry M. De Cort

The Minerals Management Service, United States Department of the Interior, in support of the 1995 National Assessment of energy resources, is identifying conceptual plays to help assess potential oil and gas resources on the Gulf of Mexico Outer Continental Shelf. Sequence stratigraphic analysis is used to synthesize a model to predict reservoir-quality sands in an undrilled deep-water sand play in the Lower Miocene Siphonina davisi section of the Matagorda Island and Mustang Island areas, offshore Texas.

Paleogeographic maps suggest that during Lower Miocene time the Texas Gulf Coast was fed by several small river systems forming a series of shifting deltas that prograded gulfward. With a relative drop in sea level, the focus of deposition was relocated to the outer continental shelf edge and the continental slope to form the lowstand systems tract (LST) components. Two locations where conditions favored the deposition of deep-water sands during Siphonina davisi time are investigated.

Several Lower Miocene sequence boundaries, maximum flooding surfaces, and other systems tract boundaries are correlated on a well-log/seismic grid. Sequence stratigraphic analysis, incorporating well-log, seismic, and biostratigraphy, is used to define and map lowstand systems tracts, depositional systems, and their associated lithofacies in the Siphonina davisi sequence. The Siphonina davisi sequence is defined on seismic records, and isochron thickness is mapped to define the paleobathymetry at the time of deposition. Sand-prone components of lowstand systems tracts are delineated by "seismic facies analysis."

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994