Geothermal Potential along the Balcones/Ouachita Trend, Central Texas--Ongoing Assessment and Selected Case Studies

Numerous wells produce warm groundwater from several Cretaceous aquifers located beneath the innermost part of the Texas Gulf Coastal Plain. The changes in landscape between the Coastal Plain and the uplands farther west result from a major geologic break. Texas is bisected along this trend by the Texas Craton, a hinge zone that separates the downwarping Gulf Coast Basin from the more stable continental interior. At depth, this hinge is defined by the subsided Ouachita Mountains; at the surface, the geologic break is expressed by the Balcones and Luling-Mexia-Talco Fault Zones.

The geologic hinge zone has clearly affected the physiography of the region. These effects include abrupt changes in terrain, climate, soils, vegetation, and availability of groundwater across the hinge. These changes have, in turn, influenced human settlement patterns (Bybee, 1952). The Balcones/Ouachita hinge is a geocultural break similar in cause and comparable in effect to the Fall Line of the Eastern United States (Woodruff, 1980). Both trends are the loci of cities. The towns and cities along the Balcones/Ouachita trend might use the thermal resources; at some localities, the warm water is already used although as drinking water and not generally for its energy content.

Studies at the Bureau of Economic Geology have documented geothermal waters in many places across Texas (Henry, 1979; Henry and Gluck, 1981; Woodruff and others, 1982). Locally, these waters may be hotter or more abundant than along the Balcones/Ouachita trend, but considering both geologic and socioeconomic aspects, Central Texas is probably the region with the greatest potential for developing a cost-effective energy resource from low-temperature geothermal waters. The cities along the Balcones/Ouachita trend constitute a market for the geothermal energy resource.