A novel upscaling method for steam-assisted gravity drainage simulations based on a viscosity–temperature model

Thermal-compositional flow simulations are crucial for understanding the intricate interactions of subsurface heat and mass transfer for geoenergy development. A case in point is the steam-assisted gravity drainage (SAGD) process, where accurate numerical simulation is essential to evaluate its efficiency and ensure environmentally sustainable oil development. However, representing the complex heat and mass transfer in SAGD requires fine-scale grids, leading to exceptionally high computational costs. To address this challenge, this study introduces a novel upscaling technique that enables efficient SAGD modelling with larger grid sizes while maintaining simulation accuracy. The proposed upscaling method employs scale factors, defined as the ratio of the coarse-scale grid sizes to the fine-scale grid sizes, to adjust the oil viscosity–temperature relationships in coarse-scale models. This method saves the need to modify the underlying source code of simulators, and thus favours the users of closed-source commercial modelling software, enabling more efficient and cost-effective field-scale SAGD simulations. The method is validated on the SAGD models of different dimensions, grid-block and overall model sizes, and oil viscosity–temperature relationships. The results show that the upscaling method speeds up the fine-scale simulations to 3.6 and 7887 times faster for 1D and 2D SAGD models, respectively, while preserving reasonable accuracy compared to fine-scale results. The method's robust performance suggests a strong potential for the practical application to large-scale SAGD operations.