Sandstone Distribution and Potential for Geopressured Geothermal Energy Production in the Vicksburg Formation along the Texas Gulf Coast

Potential geopressured geothermal reservoirs in the Vicksburg Formation are limited to Hidalgo County along the Lower Texas Gulf Coast. In Hidalgo County, an area of approximately 385 square miles (designated the Vicksburg Fairway) contains up to 1,300 feet of geopressured sandstones with fluid temperatures greater than 300°F. Inplace effective permeability, however, averages less than 1 millidarcy in the Vicksburg sandstones because of fine grain size and extensive late carbonate cementation. Also, areal extent of indivdiual reservoirs is limited in a dip direction by growth faults and in a strike direction by the lenticular geometry of the sandstone bodies. Under present criteria for geothermal fairways, the Vicksburg has minimal potential because of inferred low reservoir deliverability, which is constrained by low permeability and limited reservoir continuity. If future tests indicate that lower permeabilities are acceptable, the Vicksburg Fairway should be reconsidered because of the presence of extremely thick sandstone bodies.