A theoretical approach for estimating the surface area of a rough-walled fracture from well logging

A theoretical approach is presented to estimate the surface area of a rough-walled fracture artificially induced in the hot dry rock. In this approach the concept of parallel-plate model, average fracture aperture obtained from the injection test and by the borehole televiewer, are used. This approach has the advantage of using the permeability value obtained from well injection test and the average aperture size of fracture at the borehole wall observed by the borehole televiewer. Flow, energy and mass equations which involve the effect of fracture surface area (A) are solved numerically by the finite difference method. The results show that as A increases the dissolution and precipitation rates of silica increase. The relative error for silica production rate due to round off the value of t^-2/12K is about 10%, 800 days after injecting water through the injection well.