The Lower Woodbine (Maness Shale) of Burleson and Brazos Counties, Texas: Anatomy of a New "Old" Play
Richard Adams¹, John Carr¹, and John Ward²
The Cenomanian Lower Woodbine "Maness" Shale, of current usage, in the southwest portion of the East Texas Basin is a very organic-rich shale with high resistivity, a "hot" Gamma Ray response and very good mud log shows.
This zone owes its high organic content and the resultant well-established oil production to deposition in a silled basin Within this silled basin the zone produces 32 gravity oil in northern Brazos County and contains dry gas in southern Grimes County.
In 2008, Apache began a program recompleting from the underlying Buda and the overlying Austin Chalk into the Giddings (Eagleford) zone. The early recompletions were vertical completions with very small cumulative oil production. Later they drilled several short horizontal completions.
The data from the Apache wells such as oil gravity and Gas-Oil ratios, when combined with the completed lengths of the few horizontal completions and the regional geologic stress-strain field were used in an economic evaluation to predict where "sweet spots" should exist in this newly re-developing play. Data sets from other plays indicate that the "sweet spots" are most often located in the high oil gravity portion of the oil window where the oil-generating shale is the thickest. The play covers portions of several counties, but the best "sweet spots" will be much smaller.
The Woodbine and Eagle Ford were first defined in the Dallas, Texas area in the late 1800s. Correlations to those outcrops confirm that this productive interval as well as the so-called Lower Eagleford of South Texas is neither Eagle Ford nor the true Maness Shale. Follow-ing correct North American Commission on Stratigraphic Nomenclature practices, these organic-rich shales should be called the Lower Woodbine Formation and not the Eagle Ford Shale. The Maness Shale is only a portion of the interval below the high resistive oil-generating shale and above the Buda Limestone.
AAPG Search and Discovery Article #90202 © AAPG/STGS Geoscience Technology Workshop, Eagle Ford plus Adjacent Plays and Extensions Workshop, February 24-26, 2014, San Antonio, Texas