The work reported in this study covers the modifications performed by PTTS in the three dimensional unsteady state model developed by the Morgantown Energy Technology Center by W. K. Sawyer and J. C. Mercer, "A Diffusivity Model for Fluid Flow and Heat Conduction in Porous Media" (Merc/SP-77/2), August 1978, United States Department of Energy, Morgantown Energy Technology Center (M.E.T.C.), Morgantown, West Virginia. The model is used in this contract to stimulate a liquid dominated geothermal reservoir system. A series of cases is cited showing the versatility of the model as a simulation tool