Geothermal potential of the Raton Basin, New Mexico
S. A. Kelley
The geothermal potential of the southern Raton basin and the adjoining Las Vegas basin/Tucumcari basin, Cimarron arch, and Sierra Grande uplift in northeastern New Mexico was evaluated using equilibrium, bottom hole, and wireline temperature data. Equilibrium logs are generally from shallow wells (<600 m); interval geothermal gradients frequently correspond to lithology, which is indicative of conductive heat flow. Interval geothermal gradients in the Paleogene Raton and Poison Canyon Formations and in Cretaceous shales (Pierre, Carlile, Graneros) are on the order of 40–75°C/km. In contrast, interval gradients in the Cretaceous Trinidad Sandstone and in other sandy units are 20–30°C/km. Bottom-hole temperature (BHT) data constrain the deeper thermal structure of the basin. High BHTs were measured in the southern Raton basin near the Colorado state line (Stubblefield Canyon gas field); the maximum uncorrected BHT is 135°C at a depth of 2160 m and associated geothermal gradients are 50–68°C/km. BHTs in the Las Vegas basin/Tucumcari basin to the south are cooler (85°C at 3091 m) compared to those in the southern Raton basin at similar depths. Four wells with multiple BHTs in the Castle Rock Park gas field show a distinct decrease in temperature between measurements in the Trinidad Sandstone and measurements in the underlying Pierre Shale. This pattern implies lateral flow of warm (~45°C) water in the Trinidad Sandstone in this area. Wireline temperature logs can provide good thermal data if used with caution. Wireline logs are obtained by petroleum companies to look for zones of fluid flow or to gauge the quality of a cement job. Wireline temperature logs measured in air-drilled holes that are filled with formation water prior to measurement yield thermal data of a quality similar to equilibrium logs.
Temperatures of 150°C at depths of ~2 km are present in the Colorado part of the Raton basin just north of the state border. Equilibrium data from the Stubblefield Canyon area just south of the state line yield published heat flow values of 89–120 mW/ m2. If the elevated gradients derived from thermal data from Stubblefield Canyon are extrapolated to depth, then a temperature of 150°C is reached at 2.6–2.7 km: this depth range is greater than the depths to 150°C on the Colorado side of the border (1.6–2.5 km). The difference in temperature between the southern Raton basin and the Las Vegas basin/Tucumcari basin is attributed to erosion of low thermal conductivity Cretaceous shales from the Las Vegas basin.
- Kelley, S. A., 2015, Geothermal potential of the Raton Basin, New Mexico, in: Geology of the Las Vegas Region, , New Mexico Geological Society, Guidebook, 66th Field Conference, pp. 261-275.