Abstract

The impressive extent of the thermal energy available to Texans lying beneath the ground became evident through the research for the 2004 publication of the Geothermal Map of North America. The high volumes of produced water during hydrocarbon production, combined with the high temperatures found in Texas provide an ideal mix of resources from which to produce electricity from geothermal energy. Although previous investigations into the geothermal resource potential along the Gulf Coast led to a successful demonstration project in 1989–1990, the business environment was not yet supportive of renewable energy and the geothermal energy potential remained untapped. South Texas has the highest measured temperatures (>300°F [>150°C]) at depths of 10,000 to 12,000 ft (3 to 3.65 km). The Gulf Coast geopressured areas have the most accessible energy potential, because of the large fluid volumes, entrained gas, and geopressure flow. East Texas, while dominated by shallower drilling (typically less than 10,000 ft [3 km]) and waterflood fields, possesses a crust with high natural radioactivity in the vicinity of the Sabine Uplift. Beneath the Barnett Shale in north-central Texas is the Ellenberger Limestone, which has temperatures of 200–250°F (95–120°C) and can produce water volumes in the 20,000 to 50,000 barrels per day (3.18 × 10⁶ to 7.95 × 10⁶ lpd) range, based on injection well capacity. The development of the geothermal resource requires an understanding of both the geology and renewable energy business; the first step to development is the focus on temperature to provide the economic starting point.