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Abstract: Deep Woodbine Exploration Models and Concepts
and Status of Current Activity
Oracle Resources, LC
The Woodbine depositional model that Oracle Resources uses for exploration and development in Polk and Tyler Counties, Texas, has significantly changed from depositional models used in the 1970s through the late 1990s. As a result of this reevaluation, we have initiated a new round of Deep Woodbine drilling activity. Early results from this drilling activity suggest that tremendous reserves may be found with the application of 3-D seismic data.
The existing Woodbine fields of Polk and Tyler Counties are significant—they may ultimately produce 1 TCFG and 30 million barrels of condensate. Yet efforts to find new fields since the discovery of Double A Wells in 1985 have been largely unsuccessful. Intense drilling activity along strike to fields discovered in the 1970s and 1980s has yielded no discoveries of consequence. It is our opinion that the reason for this lack of success is that the reservoir sands are not distributed in a diffuse system but rather area highly focused in relatively few feeders, with most of the sands in Polk County within the bounds of a north-south axis of deposition.
Original work by Charles Seimers (University of Wyoming, 1978, 1981) and Deane C. Foss (Chevron, 1980) suggested that the Woodbine sands of Polk and Tyler Counties were turbidites deposited in deep water on the Outer Cretaceous Shelf. More recent data, primarily from newer cores, has cast doubts on this interpretation. Howard White (Oryx Energy Co., 1998) proposed that these fields were deposited in a shallow marine environment as shelf edge deltas. Subsequent paleo and well log data has support this newer interpretation, and the implications of the shelf edge model have encouraged exploration downdip to the Cretaceous Shelf Edge, particularly in the known sandy fairways.
As a result of these two ideas relating to the hunt for Deep Woodbine sands, a series of large 3-D seismic surveys are in progress. The first 3-D has been completed and appears to verify the proposed models, complete with the identification of several small minibasins that appear to contain thick aggradational packages of sediments that may contain reservoir-quality sands. Drilling activity by Comstock Oil & Gas and Anadarko has encountered high-quality sandstone reservoirs in these settings, reservoirs that may be superior to those of any Woodbine gas wells drilled to date.
In the coming years there will be continuation of drilling activity for Deep Woodbine sands at depths ranging from 15,000 feet to greater than 20,000 feet. These deep reservoirs are once again being targeted for drilling more than 20 years after the first wells attempted to find production from the Texas counterpart of the Deep Tuscaloosa. The excellent, highly overpressured reservoirs have the potential to make the Deep Woodbine one of the most exciting exploration plays in the onshore United States in the coming years.
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