Simulating Fenton Hill HDR Test Results Using the GEOTH3D Code

Abstract

At the Fenton Hill hot dry rock (HDR) Test Site, the Long-Term Flow Test (LTFT) of the deeper reservoir was conducted h April 1992 through April 1993, following a multi-year period of reservoir pressurization at 15.6 MPa . At an injection pressure of 27.3 MPa, the steady-state fluid recovery at the
production well (not including the additional production flow up the annulus at the injection well) was 80% at a backpressure of 12.4 MPa and 73% at a
backpressure of 15.2 MPa.

The reservoir simulation code GEOTH3D, a model based on an assumed relationship between the distribution of permeability and the corresponding distribution of acoustic emissions (AE) throughout the pressure-stimulated reservoir region, was applied to the LTFT data to determine the applicability of this code to a second HDR reservoir. The principal model output, the percent recovery of fluid at the production well under two different steady-state operating conditions, was obtained by specifying the surface injection pressure and backpressure as boundary conditions. At an injection pressure of 27.3 MPa, the computed fluid recoveries were 81% and 75%, respectively, at the two different backpressure levels of 12.4 MPa and 15.2 MPa, in good agreement with the measured LTFT results. Therefore, the proposed three-dimensional reservoir modeling method, coupling the permeability values to the AE data, appears to be very effective in simulating the Fenton Hill HDR reservoir.