The Lithostratigraphic — Sequence Stratigraphic Framework of the Woodbine and Eagle Ford Groups in Southwestern East Texas Basin

Abstract

The Cenomanian -Turonian Woodbine and Eagle Ford Groups in and around the East Texas Basin have been important reservoir objectives for over 90 years. Both groups are comprised of fluvial-deltaic sands and marine shales with the Eagle Ford shale considered the primary source rock for the giant East Texas field (5.5 Bbbls recoverable). The entire clastic section ranges from over 1,400′ thick in the central portion of the East Texas Basin to a few tens of feet on the San Marcos Arch to the southwest. The section was deposited on platform carbonates and is overlain by the Austin Chalk. Current exploration activity within the Woodbine and Eagle Ford Groups is focused on two separate but overlapping plays which are located in southwestern East Texas Basin: a tight sand play and an organic-rich shale play which are grouped together into the ‘Eaglebine’ Play. The purpose of this paper is to document a series of 4th order surfaces that appear to have chronostratigraphic significance, expand the sequence-stratigraphic correlations throughout the study area, establish a stratigraphic hierarchy to simplify confusing nomenclature, and clarify where the two currently active exploration plays fit within the overall stratigraphic framework. The study area covers 3500 mi2 in all or parts of 6 counties from Burleson County to Houston County. The area is bounded on the northeast by the Angelia-Caldwell Flexure and on the southwest by the San Marcos Arch. A dense network of cross-sections utilizing over 2000 wells was used to develop the stratigraphic interpretation. Detailed interpretations demonstrate several regionally correlatable stratigraphic sequences between the Lower Cretaceous Buda Limestone and the overlying Austin Chalk which can be used to clearly document the overall evolution of the Woodbine and Eagle Ford depositional systems. The stratigraphic framework from this investigation builds on recent published interpretations by others. Alternative interpretations of the stratigraphic relationships will be compared and contrasted where appropriate. In addition to establishing a sequence stratigraphic correlation framework that subdivides a shelfal, pro-delta shale interval in the southern part of the study area, it will be shown that the organic-rich shale play commonly identified as Lower Eagle Ford, is clearly Woodbine in age and the current tight sand horizontal play centered in western Madison County, commonly identified as Woodbine, is Eagle Ford in age.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016