| Abstract |
One of the requirements of a successful geothermal project is the ability to achieve sufficient flow rates for commercial production. In order to obtain adequate flow rates it is necessary to target areas with either high natural permeability or with potential to enhance the permeability. However, unlike temperature, the relationship between permeability and depth is complex, and difficult to predict from the surface. We present here models of random resistor networks to relate electrical resistivity to hydraulic permeability in the upper crust. In this approach, the upper crust is modelled as a network of resistors that are either electrically and hydraulically conductive, or resistive. Initial models have been run on a network with a single fault, with a constant aperture, and with a variable aperture. Considerable differences are evident between the two models with fluid and current channelling evident in the variable aperture model. In the variable aperture model, a percolation threshold can be defined. Below this threshold, permeability and electrical conductivity are very close to the matrix values. Above this threshold, they increase rapidly with permeability increasing much more rapidly than conductivity. Further modelling will be undertaken to investigate the impact of different parameters on the resistivity and permeability. Additional modelling will also incorporate embedded random resistor networks, in order to replicate the fractal distribution of fractures in the crust. |