A Summary of the Geothermal and Methane Production Potential of U.S. Gulf Coast Geopressured Zones From Test Well Data (includes associated papers 16455, 16460, 16480, and 16521 )
- R.K. Swanson (Southwest Research Inst.) | W.J. Bernard (Louisiana State U.) | J.S. Osoba (Texas A and M U.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- December 1986
- Document Type
- Journal Paper
- 1,365 - 1,370
- 1986. Society of Petroleum Engineers
- 4.2.3 Materials and Corrosion, 5.1.2 Faults and Fracture Characterisation, 5.5.8 History Matching, 2.4.5 Gravel pack design & evaluation, 5.6.4 Drillstem/Well Testing, 4.3.4 Scale, 1.6 Drilling Operations, 2.4.3 Sand/Solids Control, 2.2.2 Perforating, 5.9.2 Geothermal Resources, 4.6 Natural Gas, 3.2.5 Produced Sand / Solids Management and Control, 7.4.5 Future of energy/oil and gas
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Summary. Extensive testing in 12 wells in Texas and Louisiana has produced a significant body of production and test data from the U.S. gulf coast geopressured zones. Results indicate that these deep sediments contain some reservoir-quality sandstones capable of extended production of moderately hot brine saturated with dissolved natural gas. The best of the test wells to date, the U.S. DOE Pleasant Bayou Well 2 in Brazoria County, TX, flowed at a sustained rate of about 18,000 B/D [2860 m3/d] for about 7 months. The reservoir may cover an area as large as 58 sq miles [150 km 2]. None of the other 11 wells equaled the performance of the Pleasant Bayou test. From an economic standpoint, dissolved methane shows little promise of competitive performance in the foreseeable future. As a promise of competitive performance in the foreseeable future. As a geothermal energy source, the temperatures are disappointingly low. The resource overall appears to be large but diffuse.
Hottman's 1966 patent apparently represents the first formal recognition of the deep gulf coast sediments, known as geopressured zones, as an energy resource. The patent claims that under certain conditions, overpressured patent claims that under certain conditions, overpressured formations (i.e., geopressured formations) are capable of producing hot water and dissolved methane gas under producing hot water and dissolved methane gas under natural flow. The patent was assigned to Hottman's employer, Shell Oil Co., and no specific implementation steps were ever reported. In the years following, the resource received the attention of the U.S. Geological Survey (USGS). The USGS work was documented in a series of publications prepared by Jones, and his associates during 1968-74. After the OPEC oil embargo of 1973, geopressure, along with other alternative energy sources, began to receive relatively large research support from the U.S. DOE and its predecessors. That work culminated in a series of well flow tests, the results of which have removed much of the speculation surrounding the resource.
Description of Geopressured Sediments
In the gulf coast basin, as in many similar geological structures throughout the world, buried sediments are saturated with water, generally under hydrostatic pressure. Under certain conditions, however, the fluid may be trapped within the pore spaces, either by faulting or depositional conditions, and attain pressures approaching lithostatic. Such formations are said to be geopressured. Along the Texas and Louisiana gulf coast, geopressured conditions are general at depths below about 10,000 ft [3050 m]. Geological formations in these horizons consist of sandstone and shale; the latter accounts for about 90% the total volume. Where reservoir-quality sandstones exist in this sequence, production wells are potentially capable of flowing water at high rates. For reasons associated with the depositional history, formation temperatures are also higher than normal and constitute some geothermal potential, Perhaps most important is the dissolved methane with which the contained water is apparently saturated. Questions about the usefulness of the resource involve primarily production economics, including the producibility and production life of the potential reservoirs, the temperature of the produced water, and the quantity of producible methane contained in solution. While geopressured conditions are known to exist over an area covering at least 100,000 sq miles [259 000 km2], the magnitude of the technically and economically producible fraction of the resource is open to considerable doubt. Estimates of production costs have not been encouraging.
Requirements of a Geopressured Production Well Production Well On the basis of early study of the resource, pioneer researchers at Louisiana State U. (LSU) considered the production of geopressured aquifers. In a classic paper production of geopressured aquifers. In a classic paper on the subject, Parmigiano, using established principles of petroleum reservoir engineering, developed methods for predicting the performance of single wells or of wells in clusters under geopressured conditions.
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