Gas Fields in Northeast Texas Embayment
Before 1909 most of the gas sold for domestic and industrial use in Texas was produced in Navarro County. Production of gas began in the Corsicana district about 1900. The supplies of gas discovered and utilized in Navarro County were to a great extent depleted when gas was discovered in the Mexia-Groesbeck district, Limestone County, in 1912. About 900 acres in Navarro County and about 2,600 acres in Limestone County produced gas from sandstone zones in the Navarro and Taylor formations of Gulf Cretaceous age. Three large areas, producing gas from the Woodbine formation (basal Gulf Cretaceous), were discovered in Anderson and Leon counties in 1933–34. Together; they should produce gas in commercial quantities from about 36,000 acres.
All gas, within the scope of this paper, has been produced, from sandstones of Gulf Cretaceous age. At Edens, Corsicana, and Chatfield the gas was found in the up-dip terminations of lenticular sandstone bodies. Gas-bearing areas (Nacatoch) in the Groesbeck-Mexia-Powell belt were located chiefly on the upthrown sides of faulted structures; gas in the Woodbine formation occurred only on the upthrown sides of faulted structures. Recent discoveries of natural gas at Buffalo, Camp Hill, Cayuga, and Long Lake, produce gas from the Woodbine formation on the crests of large domes and anticlines, some of which are known to be faulted. Many theories and opinions notwithstanding, there is as yet no explanation for the predominance of gas on some structures in the embayment of northeast Texas.
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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.