2014 Rocky Mountain Section AAPG Annual Meeting

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Geothermal Assessment and Modeling of the Uinta Basin, Utah


Produced waters from sedimentary basins may represent a significant geothermal resource. This study presents a regional assessment of geothermal potential for produced waters in the Uinta Basin of northeastern Utah. Bottom-hole temperatures (BHT) and co-produced water data for 730 oil and gas wells distributed across the entire basin are combined with existing lithological information. For 135 of the wells, a BHT correction is applied using Horner and single-BHT correction methods to account for drilling-induced temperature field disturbances. A conservative depth-dependant correction value of +2.0°C/km was calculated from 50 Uinta Basin wells with reliable Horner corrections and is applied to BHTs with insufficient data for other correction methods. Corrected temperatures and typical thermal conductivities are used in a 1-dimensional, bootstrapping method to calculate thermal gradients and surface heat-flow values for each well. Calculations reveal an average geothermal gradient of about 27.0°C/km. The average heat-flow value of wells with corrected BHTs is 67.1 mW/m2. These results are generally typical for gradient and heat-flow values in the Colorado Plateau. An average gradient of 27.0°C/km implies that wells producing fluids from depths > 2 km (6562 ft) will likely have temperatures of > 54°C (129°F). Thermal outputs are calculated using well production rates and fluid temperatures. The average thermal output is 110 kW per well and maximum output is as high as 12 MW—energy currently lost to waste water. The highest output wells are a direct result of high volumetric production rates and are located in the Ashley Valley Field. Thermal models for the basin are created using a 3-dimensional finite-element modeling program (COMSOL Multiphysics 4.4) and are calibrated to well temperatures. Co-produced water temperatures in 673 wells are above 50°C (122°F) and may be suitable for direct-use applications such as greenhouses, space heating, and aquaculture. Binary geothermal power plants generally require a minimum temperature of 140°C (248°F) to achieve acceptable efficiency and 26 wells across the basin meet or exceed such temperatures. The high volume of co-produced water at wells with > 50°C temperatures along with the benefit of existing infrastructure make the Uinta Basin a candidate for the development of direct-use geothermal applications with the potential to support binary geothermal power production.