Inverse Modeling of Fractured Geothermal Reservoirs Using Pressure Interference Data

Numerically inverting simultaneous pressureinterference measurements from multiple observation wells can help to establish the large-scale spatial distributions of permeability and storage within a geothermal reservoir. For realistic results, it is important to incorporate double-porosity (MINC) descriptions into the modeling process to properly reproduce the short-term pressure-transient response to production or injection. A new finite-difference inversion program has been developed for this purpose. The reservoir is represented as a threedimensional network of grid blocks, and the description is restricted to single-phase (liquid) flow. The single-phase limitation permits the linearization of the pressure-diffusion equation in the sub-grid “matrix region”, so that MINC descriptions may be accommodated at little additional computing cost. The “simulated annealing” method is used as the optimizing technique.