Solar-Generated Steam for Heavy-Oil Recovery: A Coupled Geomechanical and Reservoir Modeling Analysis

Abstract

Abstract The use of solar thermal steam generation for heavy-oil recovery has the advantage of reducing carbon dioxide emissions, as well as offsets the cost variability of steam generation due to fluctuations in natural gas prices. Daily cyclic fluctuations in steam injection rate associated with sunlight hours, along with hydrocarbon production and heating/cooling of rock cause changes to reservoir stress. This paper focuses on the dilation and compaction behaviors associated with continuous but variable-rate solar generated steam injection. Our approach integrates geomechanical models with the reservoir simulation model. The challenge with integrating geomechanics with reservoir models is to find accurate and sufficient data for stress field and orientation, dilation and compaction pressures, and the fracture pressure for the formation. We evaluate the viability of a solar thermal steam generation system with natural gas back-up for thermal enhanced oil recovery (TEOR) in heavy-oil sands that includes geomechanical coupling with the reservoir. Coupled reservoir-geomechanical simulation runs with continuous variable steam injection were compared with the base-case uncoupled Tulare Sand steamflood project. Sensitivity analyses for dilation parameters were studied to understand their effects on the overall oil recovery and breakthrough times. Significant pore pressure variation to trigger compaction was not observed for reasonable day-time injection rates of up to 1000 BBL cold-water equivalent (CWE)/d in high permeability formations. The injection pressures were maintained much below the fracture pressure of the formation in all cases. To summarize, a solar thermal steam generation approach for thermal enhanced oil recovery is a promising technique for supplementing steam generation in areas with large solar insolation.