Abstract: Integrated Sequence Stratigraphic Concepts and Carbonate Depositional Models as a Predictive Tool for Reservoir Heterogeneity: Alabama Ferry Field (Albian), Texas

Julie A. Kupecz, Peter R. Thompson

Alabama Ferry Field, Leon County, Texas, produces oil and gas from carbonate grainstones of the Albian Glen Rose "D" interval. The field extends over approximately 40,000 acres, and has estimated reserves of 100 million barrels of oil and 250 bcf of gas. It is notable for its shelf-interior position, approximately 40 km (25 miles) NW of the Glen Rose shelf edge. The field is representative of those producing from thin, areally restricted grainstones which accumulated on a low-relief carbonate shelf. The reservoir is interpreted to represent highstand systems tract deposits, which consist of a series of stacked grainstones bounded by deeper marine shales. The productive grainstones are directly beneath a regional, seismic-scale sequence boundary.

Reservoir compartmentalization is the result of internal, facies- and diagenetically-controlled heterogeneity within the grain stones, as well as from shales and carbonate mudstones that act as inter-shoal permeability barriers. Facies within the grainstones are variably affected by marine and meteoric diagenesis. Controls on diagenesis include mineralogy of allochems, energy of depositional setting, grain packing, presence/absence of off-shoal algal coating, and degree of early cementation. Micropaleontological analysis of shales and carbonate mudstones reveal two depositional styles within the field. The first represents lateral facies change coeval to grainstone buildups, which suggest permeability barriers with limited lateral extent. In contrast, the second style represents depos tion during marine flooding; these barriers are interpreted to have laterally extensive distribution. Therefore, the integration of carbonate depositional systems, micropaleontology, diagenesis, and sequence stratigraphy has implications for the ultimate development of this and similar fields.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France