The Story of Natural Gas

Abstract Natural gas and oil usually are found in sedimentary rocks. Source materials for both probably were similar and processes by which they formed were similar, though not necessarily identical. Natural gas and oil can be described as the “petroleum complex.” The greatest volumes of natural gas and oil are found in beds of relatively recent geologic age, i.e., reservoirs of Tertiary and Cretaceous ages, although important deposits of petroleum have been found in sedimentary rocks of all geologic ages, including those as old as Cambrian. A few deposits have been found in crystalline basement rocks of Precambrian age. Gas and oil fields commonly are found in areas which were at one time basins of deposition. There are numerous basins within the earth's crust, many of which yield gas and oil prolifically. Although there are thousands of small gas and oil fields, most supplies are obtained from a relatively few major fields. A study of the major gas fields with estimated total proved recoverable reserves of 1 trillion cu ft or more shows that there are less than 100 such fields in the United States. The average size of fields generally has diminished over the years, and exploration for natural gas in the United States is resulting in the discovery of many small but few major fields. The search for natural gas is becoming increasingly costly and decidedly less effective. Available statistics indicate that expenditure per unit of gas found in 1959 was more than four times that of 1946. It is estimated that 525 trillion cu ft of natural gas has been discovered in the United States, of which 244 trillion cu ft has been produced and 281 trillion cu ft remains in reserve as of December 31, 1964. Future discoveries on the order of 500 trillion cu ft reasonably may be expected. Most of this gas will be discovered in areas now known to be gas productive, primarily the Gulf Coast, Permian basin, and Rocky Mountain regions. Some important discoveries, however, are likely in other areas. Possibilities for major offshore discoveries are particularly good. It has required about 100 years to find approximately half of what is believed to be the total supply of natural gas. Most of the very prospective areas have been explored. In the future, deeper drilling will be required and the average discoveries will be smaller and found at greater depths. Because natural gas is becoming more difficult and more costly to find, expansion of transportation and distribution facilities is beset by uncertainties. Distributors believe that they are closely approaching ceiling prices in competition with other fuels in the market. In contrast, producers claim higher field prices are necessary if reserves and production are to be expanded to meet demand. Future gas discoveries will be made where the industry can afford to search for and develop natural gas deposits. Although the natural gas industry on the whole is in relatively sound condition, undue optimism is foolhardy. Continued vigorous growth of the natural gas industry will require close liaison between producers and distributors. The long-term and best interests of most will be served by encouragement of those who are willing to search for and develop deposits of natural gas.