Abstract: Finding New Reserves in "Old" Midcontinent Gas Fields Using Sequence Stratigraphy: Boonesville (Bend) Gas Field, Fort Worth Basin, Texas

David L. Carr, Mark J. Burn

Operators' attempts to optimize gas production from Pennsylvanian sandstones in the Midcontinent region have long been frustrated by complex surface-dominated stratigraphy, mixing of clastic and carbonate lithologies, discontinuous reservoir facies, and scarcity of cores and modern log data. As part of a GRI-DOE-sponsored research project to develop integrated technologies to combat these problems, we applied sequence stratigraphic concepts to delineate reservoir mapping units in the Bend "Conglomerate" (Pennsylvanian/Atokan) of the prolific Boonesville gas field (2.3 Tcf cumulative production), North-Central Texas.

Our efforts focused on the project's 3-D seismic survey area (about 25 sq mi; 161 sq km; or 16,000 acres) where over 200 wells penetrate the Bend section. Cores and modern logging suites were studied in detail to define the sequence stratigraphic framework. The larger but more difficult to interpret "old" electric-log data base was synthesized into this framework. Atokan strata (1,000-1,500 ft thick) contain alternating terrigenous clastic and volumetrically minor carbonate beds that record high-frequency base-level excursions. Conglomeratic sandstone reservoirs occur within complex valley-fill successions, in which fluvial and deltaic sediments aggraded above subtle unconformity surfaces during base-level rise and subsequent highstand phases.

The sequence stratigraphic approach resulted in a fundamentally different reservoir mapping framework from that described in previously published works or that is commonly used by Boonesville operators. We predict that use of this framework will result in significant positive revisions of calculated gas volumes, reserve estimates, and development strategies in Bend reservoirs.

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