Commercial production of natural gas in the Lima-Indiana district of Indiana and Ohio began in 1884–1886. Ten years later the largest area known to produce gas from rocks of Ordovician age was proved and outlined. The district extends in a curve for a distance of about 150 miles and covers an area of about 12,000 square miles. Only a few gas fields of small areal extent were found in Ohio; those in Indiana were numerous and large. All are now mostly exhausted. Most were coextensive with oil fields.
In Indiana the gas field areas lie across the crest of a broad structural arch, in Ohio mostly east of the axis of a northward pitching anticline, according to published subsurface structure maps. Descriptions of local structures have not been published. Subsurface anticlines with 125 feet of structural closure, beds dipping at the rate of 40–120 or more feet per mile, and north-south axes are known in Indiana. In Ohio a fault with 100–200 feet of displacement and a general north-south trend is known. In Indiana at least, it appears that the commonly published structural form and attitude of the Cincinnati arch are not correct.
The gas- and oil-bearing horizons occur in a dolomitic limestone zone of Ordovician age, mostly in the upper 50 feet of the “Trenton” formation. Porosity and percentage content of magnesium carbonate are considered to have been the controlling factors in trapping the occurrences. The writer believes that folding and genetic sites have been at least equally important as factors in determining the occurrences. Paleogeologic action, with earth movements of the arch active before Pennsylvanian time and possibly as early as Lowville (Middle Ordovician) time, is probably an important determinant.
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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.