Zoning of the geothermal gradient in the Oriente Basin of Ecuador from Bottom Hole Temperatures

Abstract

The Oriente Basin (Late Cretaceous-Cenozoic) is one of the most complex and attractive foreland sedimentary basins of the northern Andes. It is made up of various tectonic and sedimentary cycles developed on a Precambrian basement. To evaluate the theoretical geothermal potential and the potential uses of heat in the basin, data on Bottom Hole Temperatures (BHT) of 1683 deep oil wells, distributed in 202 individual fields, have been plotted on a geo-referenced map, covering an area of 57.400 km2. The statistical treatment of the data for the calculation of the geothermal gradient included corrections of the BHT according to the method proposed by Willet and Chapman. From the plotted data, it becomes clear that the Sacha-Shushufindi Corridor shows low gradient values (7.38 to 26.1ºC/km). Instead, high gradient values (26.1 to 69.01ºC/km) are present in the Sub-Andean System and Capirón-Tiputini System. The distribution of temperature anomalies seems to be related to the NNE-SSO structural control of the basin, whose permeability pattern is well known. The extraction of heat for commercial uses is highly facilitated by the existence of deep wells that penetrate high-gradient zones, saving the generally prohibitive costs of deep drilling.