An iterative procedure for the simulation of the steady-state fluid flow in rock fracture networks

Abstract Equivalent pipe network (EPN) modelling is widely accepted as an effective technique for modelling fluid flow through fracture networks in rock masses. The major advantages of this approach are its simplicity and computational efficiency, which make it capable of dealing with complex, reservoir-scale problems. The major disadvantage, however, is that the derived flow model depends primarily on the pipe network used and the construction of a representative pipe network model is still very challenging, particularly for large and complicated fracture networks. Existing approaches for constructing EPN are primarily geometrical and do not take account of flow kinematics within fracture networks. Consequently, the flow model obtained is less realistic due to the unavoidable subjective assumptions involved in pipe connections. This paper describes a recently proposed iterative process for deriving a more realistic flow model by taking into account the flow kinematics within the fracture network while constructing the EPN model. To do so, the connection pipes are based on the flow sources and sinks of fracture intersection traces on each individual fracture. However, the input in this case is also part of the solution output and therefore the process must be iterated until the model converges to a stable solution. A simple 3D fracture network is used to cross-validate the proposed approach against a COMSOL finite element model. Finally, as a case study, the method is applied to the reservoir-scale flow analysis of the Habanero geothermal field in the Cooper Basin of South Australia.