The Delaware and Val Verde basins are structural basins which lie between the structurally positive Delaware and Davis mountains and the Marathon thrust belt on the west and south, and the structurally positive Central Basin platform, Ozona arch, and southern end of the eastern shelf on the east. The northern boundary of the Delaware basin is the northwestern shelf of southeastern New Mexico. Because of very meager subsurface control the southern limit is not definitely known but it could include the Kerr basin. The widest part is across the Delaware basin which extends 100 miles east and west. The two basins have a combined length of about 275 miles.

The seaway in which the lower Paleozoic sediments of this area were deposited was elongated east and west. Therefore, the depositional strike of the lower Paleozoic formations was approximately at right angles to the late Paleozoic structural trend. Although there were several periods of tectonic readjustment during early Paleozoic time which varied the sedimentary sequence, it was not until the post-Mississippian orogeny that the Delaware and Val Verde basins began to assume their present form.

During Pennsylvanian time this area, due to compressive forces from the south, began to assume the northwest-southeast structural trend, and by early Permian time intensified pressure resulted in a very deep structural trough. The extremely thick section of Wolfcamp sediments was deposited in this trough which included both the Val Verde and Delaware basins. No evidence of a separation of this basin is found until late Paleozoic time when the Capitan reef grew along a barrier which had formed between the west flank of the Central Basin platform, west of Fort Stockton, to the Glass Mountains. This Capitan reef formed the south line of the Delaware basin and the north line of the Val Verde basin.

In the Delaware basin the first commercial oil field was found in the Wheat field of south western Loving County, Texas, in 1924. Production in this field was encountered in the upper sands of the Delaware Mountain group. Since then approximately 20 important oil or gas areas have been found in the upper Delaware Mountain sands. The few deep tests drilled show extremely thick sections of probable hydrocarbon source beds and many reservoir beds. Many deep oil or gas accumulations are anticipated from reservoirs in the Ellenburger, Simpson, Hunton, Morrow, and Leonard.

In the Val Verde basin intensive oil or gas prospecting started with the discovery of the Puckett gas field in 1952. This field is 8 miles long and 4 miles wide and has a closure of approximately 2,000 feet. It produces gas from both Devonian and Ellenburger and according to tests it contains some of the largest gas wells in the world. Southeast of the Puckett field the Brown-Basset gas field was discovered in 1958. Although the limits of

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the field are not yet known, it now appears it will exceed the Puckett field in size and equal it in caliber of gas reserves.

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