Heat flow at the Platanares, Honduras, geothermal site

Abstract

Three boreholes, PLTG-1, PLTG-2 and PLTG-3, were drilled in the Platanares, Honduras geothermal system to evaluate the geothermal energy potential of the site. The maximum reservoir temperature was previously estimated at 225-240[deg]C using various types of chemical and isotopic geothermometry. Geothermal gradients of 139-239[deg]C/km, calculated from two segments of the temperature-depth profile for borehole PLTG-2, were used to project a minimum depth to the geothermal reservoir of 1.2-1.7 km. Borehole PLTG-1 exhibited an erratic temperature distribution attributed to fluid movement through a series of isolated horizontal and subhorizontal fractures. The maximum measured temperature in borehole PLTG-1 was 150.4[deg]C, and in PLTG-2 the maximum measured temperature was 104.3[deg]C. PLTG-3 was drilled after this study and the maximum recorded temperature of 165[deg]C is similar to the temperature encountered in PLTG-1.Heat flow values of 392 mWm-2 and 266 mWm-2 represent the first directly-measured heat flow values for Honduras and northen Central America. Radioactive heat generation, based on gamma-ray analyses of uranium, thorium and potassium in five core samples, is less than 2.0 [mu]Wm-3 and does not appear to be a major source of the high heat flow. Several authors have proposed a variety of extensional tectonic environments for western Honduras and these heat flow values, along with published estimates of heat flow, are supportive of this type of tectonic regime.