The Big Lake oil pool, located in the southwest corner of Reagan County, Texas, and opened by the discovery well in the Texon zone on May 28, 1923, was the first major oil field found in what is known as the "West Texas" district. The remarkable producing capabilities of its wells greatly stimulated geologic investigation and intense wildcat drilling throughout West Texas and southeast New Mexico. This has resulted in opening several prolific oil pools in a region formerly not considered seriously in estimates of our future petroleum reserves.

Four distinct oil zones have been developed in the field. Two, the Shallow and Texon, seem to belong in the Choza member of the Clear Fork formation, Permian in age. The Third and Fourth have been developed in the deep well (University 1-B) of the Texon Oil and Land Company at depths of 6,284-99 feet, and 8,520-25 feet, in probably the Strawn and the basal part of the Bend, respectively, both formations being Pennsylvanian in age, with the probability that the deeper zone is pre-Pennsylvanian. This well not only possesses an exceptional record for sustained rate of increase of daily oil production from the Fourth zone after drilling operations had ceased, but it is also the deepest oil-producing well in the world and the deepest boring ever drilled for any purpose. The well opened thi Fourth oil zone on December 1, after the manuscript for the original paper had been submitted, on November 11, 1928, for publication; but a description of the well's producing activity and character of the oil from this deep zone is given in an Appendix under date of January 31, 1929.

The pool is closely related to a low anticlinal dome in the surface beds (Comanche), that is a reflection of a much more pronounced dome in the Upper salt beds (Permian) and a dome of still greater amplitude in the Texon discovery oil zone (Permian).

The pools in both the Shallow and Texon zones are encircled by edge water, thus conforming to the applications of the "anticlinal theory" of oil and gas accumulation. It is believed that the pool in the Texon zone has been trapped while the oil was migrating laterally up the dip from the west and northwest, and that the character of the oil and gas in the Shallow sand suggests they may have migrated upward from the Texon zone pool along the plane of the fault immediately on the east side of the dome. Further, it suggests that the source material of the oil and gas in the Texon zone is indigenous to the dolomitic limes of the Permian.

Up to October 1, 1928, the total production of the field was 36,238,451 barrels of oil--35,210,344 from the Texon zone and 1,028,107 from the Shallow sand, or 97.16 per cent and 2.64 per cent, respectively, of the total from the field.

Many new wells remain to be drilled to develop fully the proved leases for the Texon, Third, and Fourth zones.