Finite element simulation of transient geothermal flow in extremely heterogeneous fractured porous media

• Transient geothermal flow in extremely heterogeneous fractured porous media addressed
• FEM analysis of transient non-Darcy geothermal flow in fractured permeable rocks
• An image-based adaptive unstructured meshing for heterogeneous rock structures
• Effects of rock heterogeneity on transient geothermal flow in each component analysed
• Fracture and interconnectivity dominate geothermal flow in fractured porous media.

Mineral deposits are strongly influenced by geothermal fluid behaviours, some of them are dominated by transient fluid flow and heat transfer in the extremely complicated fractured porous media. This paper will focus on the nonlinear finite element analysis of such transient geothermal flow behaviours in extremely heterogeneous fractured porous media. This includes the advanced unstructured mesh generation of extremely heterogeneous fractured porous media by using an image-based automatic meshing method for multi-materials and a nonlinear coupled finite element solver, which ensure an efficient numerical description and analysis of geothermal flow in each component of the extremely heterogeneous fractured porous media. The proposed approach has been implemented in our in-house finite element code and benchmarked with an analytical solution. Finally, a practical application example of a 3D fractured rock mass with multiple fractures and permeable components is analyzed to address how the heterogeneity of the fractured rock mass affects the transient fluid flow and heat transfer in the different rock components. Both the model verification and practical application are provided to demonstrate the capability and usefulness of the proposed approach for simulating transient geothermal flow in extremely heterogeneous fractured porous media.