Geology and Occurrence of Natural Gas in Amarillo District, Texas
Natural gas is found throughout an almost continuous belt extending from central Beckham County, Oklahoma, northwestward to northern Moore County, Texas, and thence northward to and including Morton and Stevens counties, Kansas. This belt of productive gas territory is more than 200 miles in length and ranges from 5 miles to 40 miles in width and embraces an area of proved and semi-proved gas territory of more than 2 million acres, one of the largest and most important gas areas in the world. Gas is produced from beds of Permian and Pennsylvanian age. Accumulation of gas is closely associated with deposition and folding of these beds in relation to a buried mountain range known as the Amarillo Mountains. Natural gas has been known to exist in this area since 1918. From that time it has developed in economic importance until to-day it occupies first place in production of natural gasoline and carbon black and is rapidly becoming the largest producer of natural gas for domestic and industrial use. Natural gas is now being transported from this district by pipe lines to such distant points as Chicago, Indianapolis, Denver, and Fort Worth. The writers discuss the geologic occurrence of the gas and set forth production data in connection with its utilization.
Figures & Tables
Geology of Natural Gas
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.