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Two fairly recent estimates of natural gas recoverable from tight gas reservoirs in the U.S. have been made. One was prepared in 1978, by Lewin and Associates for DOE (U.S. Department of Energy) and the second was made by the NPC (National Petroleum Council) in 1980. Lewin estimated about 200 tcf is recoverable from the 14 most favorable regions in the U.S. The NPC estimated that about 500 tcf is recoverable from the entire onshore U.S.
These studies involved a careful analysis of available data; however, both studies excluded large areas and great thicknesses of rock strata from their resource data base. The reasons for these exclusions were mostly lack of good well control and not absence of gas potential. Therefore, both assessments were conservative and the potential recoverable resource is probably much larger than even the 500 tcf estimated by the NPC.
Unfortunately present-day technology is not able to consistently identify, stimulate, and produce large volumes of gas from lenticular and (or) deep tight reservoirs. The NPC recognized these problems and listed many research topics and programs, in their report, that should be undertaken to increase the amount of recoverable gas.
A few of the more important informational needs are: (1) better methods to predict geometry of reservoirs, (2) improvement of log interpretation, (3) better prediction of natural fracture systems, (4) control of, and prediction of, hydraulic fracture height, length, and orientation, (5) elimination of formation damage, and (6) development of innovative reservoir stimulation methods. DOE has supported a number of research efforts directed toward solving many of these problems.
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