Fracture Network Modelling of a Hot Dry Rock Geothermal Reservoir

Abstract

Fluid flow and tracer transport in a fractured Bot Dry Rock (HDR) geothermal reservoir are modeled using fracture network modeling techniques. The steady state pressure and flow fields are solved for a two-dimensional, interconnected network of fractures with no-flow outer boundaries and constant-pressure source and sink points to simulate wellbore-fracture intersections. The tracer response is simulated by particle tracking, which follows the progress of a representative sample of individual tracer molecules traveling through the network. Solute retardation due to matrix diffusion and sorption is handled easily with these particle tracking methods. Matrix diffusion is shown to have an important effect in many fractured geothermal reservoirs, including those in crystalline formations of relatively low matrix porosity. Pressure drop and tracer behavior are matched for a fractured HDR reservoir tested at Fenton Hill, NM.