Regional Assessment of Geothermal Potential along the Balcones and Luling-Mexia-Talco Fault Zones, Central Texas

The Balcones and Luling-Mexia-Talco Fault Zones delineate a belt that stretches across the central part of Texas from the Rio Grande to the Red River. The fault zones are marked by broken and displaced strata, and the juxtaposition of diverse bedrock types has had a noticeable effect on natural resources both at the earth's surface and below ground. There have also been demographic responses to the abrupt changes in natural features; many of the major Texas cities, including Austin, Dallas, Fort Worth, San Antonio, and Waco, occur along this trend.

Several Cretaceous aquifers along this belt provide ground water for municipal, industrial, and domestic users. In general, the waters obtained from these aquifers have low temperatures and low concentrations of dissolved solids. However, in some areas, the only available water supply occurs in the deepest, downdip parts of the aquifer. There, water temperature values are anomalously high—locally as much as 60 °C (140 °F). For many years, these warm and locally mineralized waters have supplied municipal and domestic needs, but the heat content was considered a nuisance or an oddity. Warm waters have supplied a few health spas and swimming pools, but in general, the heat content of these waters has been wasted.

This report presents a region-wide inventory and assessment of aquifers known to yield warm water (greater than 90°F; 32°C). We have conducted this study to ascertain the potential for obtaining geothermal energy for space heating and water heating needs. The aquifers investigated include the Hosston/Trinity Sands, the Hensel Sand, the Paluxy Sand, the Edwards Limestone, and the Woodbine Sand. We have examined each aquifer in terms of its stratigraphic and structural framework and its hydrogeological properties.