RIASSUNTO
Abstract
The authors of this paper prepared a series of analyses of the supplemental supply sources or natural gas. This study was developed for the use of the Gas Supply Committee of the American Gas Association. The authors operating as a task force prepared a series of individual studies which were then integrated Into a single report which will be published as the proceedings of the Gas Supply committee workshop II. This SPE- DOE paper has been taken from the broader study. It emphasizes the unconventional or non-conventional sources of natural gas and provides sufficient summary data on other provides sufficient summary data on other supplies of natural gas to facilitate a review of the major findings of the task force with respect to the relative importance of unconventional sources of gas.
This paper provides a review of unconventional sources of gas from western tight sands, Devonian shale, gas from coal seams, SNG from peat, SNG from oil shale, gas from geopressured aquifers, gas from urban waste and animal residues and gas from biomass. The potential gas supplies from all sources are compared for four specific scenarios to Illustrate the variability of the gas supply because of different national energy policies.
WESTERN TIGHT SANDS
The so-called tight formation in the West occur in two types of formations, blanket and lenticular sands. At one extreme are single, relatively thin (10 to 100 feet) gas-bearing zones of generally uniform thickness blanket sands) which extend over a large area. At the other extreme are the lenticular formations composed of relatively thick sections (possibly 1,000 or feet) containing multiple lenses scattered throughout the section, 35 non-marine formations of the Rocky Mountain basins. There are 20 known geologic basins that have reservoir rocks with properties such as permeability and porosity or such value that they must be considered as unconventional (less than 0.03 millidarcies permeability and less than 10 percent porosity) permeability and less than 10 percent porosity) The Lewin 13-basin estimate of gas in place was 400 tcf. Although numbers are not place was 400 tcf. Although numbers are not available yet from the National Petroleum Council Task Force on tight sands, indications are that their estimates Bill be much higher than those in the Lewin report perhaps more closely approximating the National Gas Survey. The National Gas Survey and the National Petroleum Council study for the DOE is based Petroleum Council study for the DOE is based on a lesser number of basins but includes speculative and very tight rock not included in the Lewin survey. The National Gas Survey estimate of gas in place for Unita, Piceance, and Green River Basins is 600 Tcf. Piceance, and Green River Basins is 600 Tcf. When the National Gas Survey reviewed their 1973 estimates in heir 1978 report to the DOE, they added 193 Tcf for parts of the San Juan Basin and the Northern Great Plains Province with no change for the original Province with no change for the original 3-basin estimate. There are several incentive pricing packages under consideration. However, packages under consideration. However, considering one proposed definition for tight sands (.03 millidarcy), it is anticipated that no significant production Twill be available until 1984. The primary factors affecting these projections are: 1) Lee unknowns associated with Incentive packages and pricing consideration; 2) the lack of data in many basins; 3) the time and financial requirements for gathering and transmission systems. Production estimates for the existing technology case are based on 100 wells being drilled in 1984, 200 wells n 1985 and then 200 additional wells each year until 1988 where 300 new wells are projected to be drilled. estimates for the advanced technology case are based on 200 wells being drilled in 1984 and then an additional 200 wells each year to 1987 then 300 wells would be drilled.