Abstract

Additional gas reserves remain to be discovered in the western Delaware basin. Preliminary results of an integrated geophysical and geological study of a part of the Delaware basin–Diablo Platform margin document a number of potential gas plays within that basin. The study area straddles the Reeves–Jeff Davis county line along the Davis Mountain front in Trans-Pecos Texas, long an area of structural conjecture.

Modern interactive reprocessing of inexpensive, older 2D seismic data offers an economic reconnaissance tool to focus future exploration efforts. Such reprocessing techniques applied to early 1970’s-vintage group shoot data from the Delaware basin have dramatically improved the seismic image, aiding subsequent geological interpretation. Reprocessed “off-the-shelf” seismic data clearly delineate a regional, northwest-trending, high-angle reverse fault (approximately 2500 ft of throw) forming the boundary between the western flank of the Delaware basin and the eastern edge of the Diablo Platform. This fault, mapped for more than 40 mi, appears similar in style and magnitude of throw to faults penetrated in wells along both the northwestern margin (Huapache monocline) and the eastern margin (Central Basin Platform) of the Delaware basin. Seismic stratigraphic interpretation of the reprocessed profile suggests several possible structural and stratigraphic trapping mechanisms. Depositional patterns indicate that the hinge line of the Diablo Platform has been periodically active since Early Ordovician time. At least one fault may have been active prior to deposition of the Devonian Woodford Shale, although most displacement is post-Mississippian.

Possible gas plays along the western margin of the Delaware basin include:

1. sandstone “thicks” in the Delaware Mountain Group, comparable to Casey Draw (Bell Canyon) field;

2. Wolfcampian carbonate-debris flows similar to those producing in the Midland basin, developed over upthrown blocks;

3. Bone Spring, Wolfcampian, and Pennsylvanian biogenic (crinoidal) carbonate mounds developed on the crests of upthrown fault blocks;

4. Wolfcampian stratigraphic pinch-out traps developed in multiple tongues of clastic detritus shed from the hanging wall of the Diablo Platform margin fault;

5. Devonian Thirtyone Formation erosional truncation trap developed along the flanks of up-to-the-basin fault blocks;

6. lower Paleozoic structural traps in large anticlines (more than 500 ft of closure) developed in front of the platform boundary fault; and

7. lower Paleozoic structural–stratigraphic traps on counter-regional up-to-the-basin fault blocks.