A Numerical Study for Determining Lateral Thermal Gradient Based on Reservoir Properties

Abstract

Unlike other renewable energy, geothermal resources are located beneath the surface. As a result, geothermal subsurface interpretation has been known to possess uncertainties. Uncertainties in thermal gradient calculation can lead to large errors in the predicted top of reservoir depth, thus unduly influencing geothermal resource estimation's precision and accuracy. It may impact the drilling cost, production performance, and the well lifetime. The geothermal thermal gradient wells require numerical models rather than conventional analytical models due to high uncertainties of temperatures and reservoir complexity, especially in permeability distribution. This paper examines the permeability and up-flow temperature sensitivity analysis to reduce thermal gradient uncertainties. Two different permeability models have been studied: fault-hosted and distributed fracture network permeabilities. A further result of lateral thermal gradient is simulated using PetraSim. The numerical model result indicates that the distributed fracture model’s thermal gradient range values are 4.08-10.87°C / km for liquid layer and 0.46-0.53°C / km for two-phase layer. While for the fault-hosted models, the thermal gradient range values are 3.16-24.93°C / km for liquid layer and 0.74-2.19°C / km for two-phase layer.