Geopressured Geothermal Fairway Evaluation and Test-Well Site Location, Frio Formation, Texas Gulf Coast

摘要

Tertiary strata of the Texas Gulf Coast comprise a number of terrigenous depositional wedges, some of which thicken abruptly at their downdip ends as a result of contemporaneous movement of growth faults and underlying salt. The Frio Formation, one of these wedges, has been studied regionally by means of a grid of correlation cross sections aided by micropaleontological control. By means of these sections, the Frio was subdivided into six map units; maps of sandstone distribution within these units delineate principal elongate sandstone trends parallel to the Gulf Coast composed of deltaic, barrier-bar, and strandplain sandstones. These broad regional studies, followed by detailed local investigations, were pursued in order to delineate prospective areas for production of geopressured geothermal energy. A prospective area must meet the following minimum requirements; reservoir volume of 3 cubic miles, minimum permeability of 20 millidarcys (md), and fluid temperatures of 300 exp 0 F. Several geothermal fairways were identified as a result of this Frio study. In summary, detailed geological, geophysical, and engineering studies conducted on the Frio Formation have delineated a geothermal test well site in the Austin Bayou Prospect which extends over an area of 60 square miles. A total of 800 to 900 feet of sandstone will occur between the depths of 13,500 and 16,500 feet. At least 30% of the sand will have core permeabilities of 20 to 60 millidarcys. Temperature at the top of the sandstone section will be 300 exp 0 F. Water, produced at a rate of 20,000 to 40,000 barrels per day, will probably have to be disposed of by injection into shallower sandstone reservoirs. More than 10 billion barrels of water are in place in these sandstone reservoirs of the Austin Bayou Prospect; there should be approximately 400 billion cubic feed of methane in solution in this water. (ERA citation 04:002983)