An improved modeling method using overlapping meshes for geothermal wellbore simulation

Abstract

Since temperature and pressure disturbances in geothermal reservoirs are mainly caused by production and injection activities through wellbores, establishing an accurate wellbore model is crucial. However, due to significant size discrepancies between wellbores and reservoirs, accurately resolving the wellbore geometry requires a large number of mesh cells, which seriously reduces computational efficiency. A commonly used method to reduce the mesh cell number is simplifying the wellbore geometry as a point (in 2D) or a line (in 3D). However, existing modeling methods for this simplified wellbore geometry introduce additional errors. To improve calculation accuracy without reducing computational efficiency, we propose an overlapping mesh modeling method, which incorporates one overlapping cell for each wellbore, enabling the wellbore geometry to be considered without impacting the reservoir mesh generation. The wellbore cell can exchange mass and energy with the reservoir cells it covers, ensuring that the temperature and pressure disturbances caused by wells can be simulated accurately. Four benchmark cases were used to verify the present method. The results show that, compared to existing simplified wellbore modeling methods, the present method reduces hydraulic head errors by 1 to 2 m and temperature errors by 1 to 2 ℃ in the vicinity of the wellbore, while the additional computational cost is negligible.