A physicochemical model for accurate prediction of oil shale in-situ conversion

Underground in-situ conversion constitutes a crucial method for the efficient utilization of oil shale resources, efforts are underway to verify its technical feasibility and economic viability at the reservoir scale. However, the current physicochemical models do not consider the significant impact of asphaltenes. As a result, the inaccurate simulation prediction of reservoir-scale development severely hinders the optimization of in-situ oil shale conversion technologies and their industrial application. In this study, the research first revealed the rheological properties of oil shale pyrolysis oil with different components, followed by the establishment of a viscosity-temperature model accounts for the influence of asphaltene. By introducing a correction coefficient, a modified viscosity mixing model has been established that applicable to commercial simulation software. Additionally, a reaction equation for the secondary pyrolysis of asphaltenes was developed, leading to the formulation of a more comprehensive physicochemical model for oil shale in-situ conversion. Compared with current models, the revised model exhibits higher accuracy in reflecting the in-situ conversion process. For the first time, the occurrence of reservoir blockage in numerical simulation and its underlying mechanism have been identified. Meanwhile, the energy consumption during development had been underestimated. These conclusions can provide valuable support for the reservoir-scale oil shale in-situ conversion. • The viscosity-temperature model and modified viscosity mixing model considering asphaltene content were established. • An improved oil shale pyrolysis model was established considering the asphaltene behaviors. • Accurate prediction of oil shale in-situ conversion can be achieved based on the improved physicochemical model.