The geomechanical response of naturally fractured carbonate reservoirs to operation of a geothermal doublet

摘要

The properties of faults and fractures under dynamic reservoir conditions are critical in determining flow and performance of geothermal doublets in fractured reservoirs. The complexity of faults obtained from geological and seismic characterization is usually not honored in flow models for fractured reservoirs. Fault zone architectures may affect flow as well as the geomechanical response of the fractured reservoir to doublet operation. In this study, an analytical model is developed that allows incorporation of fault zone architecture and multiple fault sets in the description of fractured reservoir permeability. The model is used with data from seismic fault characterization to describe bulk permeability for a potential geothermal target in fractured Dinantian carbonates in the Netherlands. The evolution of pressure and temperature during doublet operation is simulated using a 2D numerical flow simulator. The geomechanical response of the fractured carbonates to doublet operation was analyzed using a Mohr-Coulomb failure analysis. Large variations in the spatio-temporal evolution of pressure and temperature are found for different permeability constraints and doublet designs. Increased fracture permeability, reactivation of fractures, shear failure of the reservoir rock, and initiation of tensile fractures can affect flow and need to be taken into account to optimize doublet performance.