| Abstract |
A modeling method comprising four phases is proposed to evaluate an as-created EGS reservoir. The first step is to process the Micro-EarthQuake (MEQ) location data, obtained during reservoir creation, in the 3-D visual environment of AutoCAD. Each hydrofracturing event results in a specific set of MEQ locations forming a cloud of recognizable, 3-D ellipsoid shape. The second step is to visually match each 3-D ellipsoid MEQ cloud with a 2-D, planar ellipsis with strike and dip orientations and lateral, principal diameters in the fracture plane in AutoCAD. In the same step, a planar discretization mesh is added inside the ellipsis. The connecting intersections between neighbor fractures can be visually changed and/or adjusted according to either a hypothesis or field observation. Connections and intersections with the injection and production boreholes are also added to form a 3-D mesh system visually staying in the MEQ cloud system obtained for all hydrofracturing events for the reservoir. The third step is the creation of the circulation fluid flow network model by defining planar channels along the mesh edges as branch connections. The hydraulic aperture of each branch is defined as a function of the thermo-mechanical-chemical response of the rock strata around the hydraulic system of the fracture network. The fourth step is to solve the coupled T-H-M-C network model numerically and to match the model results with the measurement data from field tests. Particularly, fluid circulation experiments defined as the third steady-state flow test, Reservoir Verification Flow Test, as well as the thermal drawdown given by reservoir circulation measurements must be matched, minimizing deviation. During minimization, the T-H-M-C model parameters are varied for achieving a best fit. The method is demonstrated for the Fenton Hill, Phase II reservoir using published data for the microseismic active planes obtained from the Massive Hydraulic Fracturing Experiment #2032 and the fluid circulation experiments defined as Experiment #2067. A simple fracture aperture mode is demonstrated to be able to characterize the Phase II reservoir flow model against the measured flow data. |