This paper presents briefly material which is closely related to the natural gas industry. It is not a comprehensive treatment of the topics included nor does it include discussions of underlying engineering principles. More complete knowledge of the topics treated may be acquired by consulting the references given in footnotes.
Natural gas, coal, and petroleum are the principal sources of primary mineral fuels. On them, next to fertility of the soil, rest the foundations of economic progress. The industry is most highly developed in the United States, and there most of the commercially utilized deposits of natural gas are located.
Natural gases are phenomena of nature found in rocks. Neither their origin nor the amount and extent of their supplies are known. There are several types and many varieties of natural gases, but in this paper the term “natural gas” is used in the trade sense to include all varieties in which the paraffine series of hydrocarbons predominate.
Natural gas of commerce is a hydrocarbon mixture generally containing other gaseous substances, some of which are inflammable, some non-inflammable, and others corrosive in their natural and combustion states. The average composition of pipe-line gas, as it is delivered to consumers, is as follows.
The gaseous hydrocarbon constituents of commercial natural gas, at ordinary temperatures and pressures as it issues from wells, are principally methane (CH4) and ethane (C2H4), but varying amounts of propane (C3H8) and butane (C4H10) may be present as gases. The higher members, pentane (C5H12), hexane (C6H14), heptane (C7H16),
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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.