A hybrid simulation approach to evaluate stimulation micro-seismic events and production potential of fractured geothermal reservoirs

Abstract

This study presents an integrated approach to simulate fluid flow and to predict the micro seismic events during stimulation and circulation of cold water over a longer term in geothermal reservoirs. The integrated approach based on new three dimensional fully coupled thermo-poroelastic numerical model for evaluation of energy recoverable. In the presented approach, the fracture aperture due to fracture slippage is calculated by shear and dilation. The shear slippage is controlled by the concept of shear failure using linear Mohr-Coulomb criterion. The numerical model is validated against an analytical Oda’s model for permeability tensor calculation and against an analytical solution for thermo-poroelastic model. The heat transfer between the rock and fluid is modelled by using the conductive heat transfer within the reservoir rock and convective heat transfer in discrete fractures. The thermal stress changes are included in the model to be studied by using roughness induced shear displacement principle in a poro-thermo-elastic environment. The fracture aperture changes are estimated by using an analytical model based on the distributed dislocation technique. The roughness of fracture surfaces is used in the calculation of residual fracture aperture. The presented approach is used to study the potential of permeability enhancement for Habanero geothermal reservoir at a depth of 3600 m. The result show that the increasing in tensile effective stress tend to increase the fracture aperture within the zone of cooling. This increasing in fracture aperture led to significant changes in pressure distribution (decrease in impedance) and hence, increase in the flow rate.