Upscaling of Hydraulic Properties of Fractured Porous Media: Full Permeability Tensorand Continuum Scale Simulations

摘要

The simulation of flow and transport phenomena in fracturedmedia is a challenging problem. Despite existing advances incomputer capabilities, the fact that fractures can occur over awide range of scales within porous media compromises thedevelopment of detailed flow simulations. Current discreteapproaches are limited to systems that contain a small numberof fractures. Alternatively, continuum approaches require theinput of effective parameters that must be obtained asaccurately as possible, based on the actual fracture network orits statistical description.In this work, a novel method based on the utilization of theDelta-Y transformation is introduced for obtaining theeffective permeability tensor of a 2D fracture network. Thisapproach entails a detailed description of the fracture network,where each fracture is represented as a segment with a givenlength, orientation and permeability value. A fine rectangulargrid is then superimposed on the network, and the fractures arediscretized so that each one of them is represented as aconnected sequence of bonds on the grid with a hydraulicconductivity proportional to the ratio of effective permeabilityover fracture discretization length. The next step consists ofthe selection of a coarser rectangular grid on which thecontinuum simulation is performed. In order to obtain thepermeability tensor for each one of the resulting blocks, theDelta-Y method is used.Finally, the resulting continuum permeability tensor is used tosimulate the steady-state flow problem, and the results arecompared with the actual flow pattern yielded by the fracturenetwork simulation. The results obtained with both methodsfollow a similar flux pattern across the reservoir system. Thisshows that the proposed approach allows for efficient performupscaling of hydraulic properties by honoring both the underlying physics and details of fracture networkconnectivity.