Westbrook Field, Mitchell County, Texas1
The Westbrook oil field is doubly worthy of description because it is the discovery field of western Texas and because oil was found in Permian strata, previously not seriously considered as oil-producing beds. Since the first producer in 1920, a 10-barrel well at 2,498 feet, 77 wells have been drilled, averaging 40 barrels each. Early in 1926, 8 were producing. The Triassic extends from the surface to 500 feet in depth; the remainder of the section is Permian. Several key beds in the Permian are used to map the subsurface structure which is that of a northeast-southwest anticline. The 2,400-foot “pay” and the 3,000-foot “Morrison sand” are themselves good markers, occurring along porous zones within definite vertical limits. The productive reservoir is dolomitic limestone. The oil has a gravity of 25.8° Be., and contains 4 per cent sulphur, and 32 per cent gasoline. Its source is probably the Permian limestones and shales. Two kinds of gas occur in the field: (1) non-inflammable gas at depths between 1,000 and 1,300 feet and (2) wet petroleum gas in both oil zones.
Figures & Tables
Modern petroleum geology in the United States had its beginning in the first decade of the 20th Century when the U.S. Geological Survey began mapping the structure of the rocks in and near old fields in order to discover the various types of structural conditions under which oil and gas are trapped. Structural geology has evolved as a branch of the broader science far more rapidly than have methods of mapping the attitude of rocks at the surface. This volume, published in the late 1920s, was designed to afford authoritative and modern descriptions of the structure of typical oil fields in the United States. Each of the 30 fields contained here is described by an author who is intimately familiar with the available data. The relationship of structure at the surface and at depth for different terranes is clearly set forth wherever the strata are not parallel. Fields include: McKittrick, California; Fairport, Kansas; Urania, Louisiana; Artesia, New Mexico; Burbank, Oklahoma; Cabin Creek, West Virginia; and Luling, Texas.