National Geographic : 1981 Feb 28
STURAL S I cheap NATURAL GAS, flowing from an estimated 165,000 ells across the country, day supplies 26 percent of the ition's energy needs. Each ,arwe consume 20 trillion ibic feet (TCF)-and for ars production has itstripped discoveries of -wreserves, leading many perts to consider gas a wly dwindling resource. Since 1978, when gradual ,control of prices began, surge in oil and gas ploration has revealed ist new gas fields in e Rocky Mountain region id the Gulf coast of Louisiana, ough their potential still undetermined. estimates of proved reserves ow that production 1979 exceeded discoveries '39 percent. By these easurements, U. S. reserves clined to 195 TCF in 1979. But e Department of Energy says scoveries in 1980 may .ve reversed this trend. Meanwhile, policymakers Ivocate turning to new gas urces, including imports >m Canada and Mexico, ipments of liquefied natural s (LNG)from Arab states ,dIndonesia, the construction a gas pipeline from Alaska, d the costly process of coal sification. Researchers are also looking )re seriously at conventional gas resources, ig considered uneconomic to develop. Huge volumes lie locked in the Devonian shales ofAppalachia, in the nation's enormous coal beds, and in the deep, brine-filled aquifers of the Texas-Louisiana Gulf coast region. According to the National Petroleum Council, the most promising unconventional resource may be found in concrete-hard geologic formations called tight sands, which underlie many regions of the country. Today the industry produces almost one TCF annually from such sands, which must be fractured underground by injection of high-pressure fluids to allow larger quantities of gas to reach the well bore. Tight sands in the contiguous United States may yield between 192 and 574 TCF, the council says, although other estimates place total deposits, including Alaska, as high as 800 TCF. Behind the pronounce ments of the policymakers lie enormous uncertainties. Vast areas of the nation's prospective oil and gas sediments remain to be explored, despite the drilling of 2,600,000 wells since 1859. Although drilling reached an all-time high in 1980, only 25 percent of the effort was devoted to gas. And the petroleum industry complains that leasing and environmental restrictions on federal lands have prevented or slowed exploration in some of the nation's most promising regions. The result has been a fierce debate. Optimists, represented by the American Gas Association, claim that natural gas supplies could be increased to between 23 and 33 TCF a year through massive investments in alternate sources. But most analysts predict little change inU. S. gas supplies during the next decade. "We can't base our hopes on unconventional gas until we've invested the money to find out what can be produced," says Hans H. Landsberg, senior fellow at Resources for the Future (pages 70-71). "It could be a huge resource-but we must plan conservatively." When U. S. fossil-fuel reserves are compared in energy potential as expressed in quads (a quadrillion British thermal units), coal is by far the largest. But when annualproduction is compared, natural gas goes to the top of the list, coal to the bottom. The use of oil is greater than either, but only about three-fifths is produced domestically; the rest is imported. U. S. NATURAL GAS RESOURCES (in trillion cubic feet) RESERVES EVONIAN CONVENTIONAL SHALE POTENTIAL 600 1,019T The potentialfor unconventionalsources of naturalgas may be enormous, as will the costs of finding and drilling for them. Geopressuredzones - brine-filled formationspermeatedwith gas representa huge potential resource.