A Basin-Scale Geothermal Assessment of Co-Produced Waters in Oil and Gas Fields: Uinta Basin, Utah, USA

摘要

Co-produced waters from sedimentary basins may represent a significant geothermal resource. This study presents a regional assessment of the geothermal potential for co-produced waters from oil and gas fields of the Uinta Basin in northeastern Utah using bottom-hole temperature (BHT) and co-produced water data for 776 oil and gas wells along with available lithological information. For 136 of the wells, a BHT correction is applied using Horner and single-BHT correction methods to account for drilling-induced temperature field disturbances. From these wells, a conservative depth-dependent correction of+2.0°C/km was derived and applied to BHTs with insufficient data for other correction methods. Corrected temperatures and typical thermal conductivities are used to calculate thermal gradients and surface heat-flow values for each well. Calculations reveal an average geothermal gradient of about 27°C/km, implying wells producing from depths greater than 2 km in the basin will likely have temperatures greater than 65°C. The average heat-flow value from wells with corrected BHTs is 67 mW/m~2. These results are generally typical for gradient and heat-flow values in the Colorado Plateau. Thermal outputs are calculated using well production rates and fluid temperatures. The average thermal output is 88 kW per well with a maximum output as high as 10 MW-energy which is currently lost to waste water. The highest output wells are mostly a result of high volumetric production rates. Thermal models for the basin are created using a 3-dimensional, finite-element modeling program (COMSOL Multiphysics 4.4) and are calibrated to corrected well temperatures. Preliminary models reveal an area of approximately 16,000 km2 with temperatures above 75°C at 2 km depth, and an area of 5,500 km~2 with temperatures above 150°C at 5 km depth. Co-produced water temperatures in 740 wells are above 50°C 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 to achieve acceptable efficiency and 36 wells (～5%) across the basin meet or exceed such temperatures. The thermal regime and existing infrastructure make the Uinta Basin a candidate for extensive direct-use geothermal applications and possibly binary geothermal power generation.