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ABSTRACT: A Review of Current Well Testing and Environmental Monitoring at Geopressured-Geothermal Prospect Sites in South Louisiana

Chacko J. John, Donald A. Stevenson, Charles G. Groat, George F. Hart

Geopressured-geothermal sandstone reservoirs are present in several sedimentary basins worldwide. Those in the northern Gulf of Mexico basin contain gas-saturated brines at high temperature (215°F+) and have been estimated to contain up to 250 tcf of recoverable natural gas. The U. S. Department of Energy (DOE), beginning in 1975, has sponsored well testing and environmental programs aimed at the potential development of this resource. Currently three prospects are in various stages of developmental testing. The Gladys McCall #1 well (Cameron Parish, LA), presently shut in to observe pressure buildup, was tested almost continuously for four years. It produced 27.3 million bbl of brine and 676 million scf gas at an average production rate of 20,000 bbl/day from perfor tions between 15,158 and 15,490 ft. The Superior Hulin #1 well (Vermilion Parish, LA) has recently been recompleted and perforated between 20,670 and 20,690 ft for initial production testing, expected to commence early in 1990. The maximum recorded temperature in this well is 338°F and the sandstone is 570 ft thick. The Pleasant Bayou #2 well (Brazoria County, TX) is presently being tested at approximately 18,000 bbl/day from perforations between 14,544 and 14,704 ft, has a gas/brine ratio of about 23 scf/STB, and a temperature of 291°F. An experimental electrical energy conversion system has been set up at this site.

Brine is disposed by subsurface injection. The environmental concerns connected with production and disposal are land surface subsidence, fault activation, and fresh water aquifer contamination. Land subsidence and fault activity are being monitored using four to five continuous microseismic recording stations at each site and periodically surveyed first-order benchmark networks tied to National Geodetic Survey networks. Water supply contamination is being monitored by periodic sampling and chemical analyses of water from surface and ground water observation wells. No adverse environmental effects have been detected thus far.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990