Natural Gas in West Texas and Southeast New Mexico
Large gas reserves have been proved in West Texas and southeast New Mexico. The three most important areas are: (1) the East Lea County “high,” in Lea County, New Mexico, where approximately 250 square miles have been shown to be productive by scattered wells; (2) the Big Lake field in Reagan County, Texas, where nine wells below 8,000 feet have a possible potential of 370 million cubic feet of gas per day; and (3) the Hobbs field in northern Lea County, New Mexico, where two gas “pays” above the main oil-producing horizon have shown large reserves of good quality gas, and where more than 30 million cubic feet of gas is produced daily from the lowest “pay” with the oil. Besides these three main areas, nine others of less importance are discussed. In spite of the large gas reserves, very little gas is being withdrawn for commercial purposes. This is because of the great distance of the fields from centers of large consumption. Recently a gas pipe line has been completed from the East Lea County “high” to Bisbee, Arizona, and to Cananea. Mexico, and gas supplied to smelters in those places.
As far as possible, the writers have tried to avoid repetition of information already published. Several of the West Texas and southeast New Mexico fields have been previously described in connection with their oil production. Reference is made in footnotes to these papers for detailed geologic description.
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Alberta is the only western Canadian province in which a production of natural gas and oil has been developed. Natural gas was discovered in 1885, and at present there are seven producing fields and 330 miles of main pipe lines.
Alberta is divided into eight structural provinces; four of these are gas-producing regions, one is prospective, and the others are of no interest as gas areas. The stratigraphic column has three persistent features, namely, the Palaeozoic limestone section, the profound unconformity superimposed on it, and the succeeding Mesozoic section of transgressive-regressive deposits.
The Turner Valley field is the only developed field producing from formations of Palaeozoic age, though there have been significant discoveries suggesting that other fields are present. A theory is advanced in this paper to explain a Palaeozoic origin for the heavy oil and bitumen in the basal sandstones of the Mesozoic. The gas accumulations in the basal sands were later derived from the bitumen and heavy oil. The reserves of gas in Palaeozoic rocks and the basal sands of Mesozoic age are large.
During Mesozoic time there were at least five marine transgressions of the seas, and there is a marked relation between the marine shales and the gas-bearing horizons in rocks of Mesozoic age. Gas is generally found in the sandstones immediately overlying, within, or immediately underlying the marine shales.
Gas is found in rocks of Jurassic age in the Southern Plains and the Southern Foothills. The reserves are estimated to be about 80 billion cubic feet. Only small amounts of gas are now produced from Jurassic horizons. Gas is found in marine formations of Comanche age in northern Alberta, but there are no developed fields, and the reserves are unknown. There are three gas-bearing horizons in the Colorado (Gulf series), with several fields, including the Foremost, Viking, and Medicine Hat fields. The possible reserves are large and are probably in excess of 600 billion cubic feet. The Lower Montana and Upper Montana rocks (Gulf series) produce gas over large areas, but the yields are small and the horizons are of minor importance. There are no marine rocks of post-Mesozoic age, and the only gas occurrences are small flows from lacustrine deposits.
The analyses of natural gases in Alberta when arranged according to geologic horizons and localities appear to show an increase in the proportion of higher hydrocarbons to methane in a westerly direction for a given gas-bearing horizon. This may be due to the effect on the source material of increasing metamorphism westward.