Poro-mechanical processes play an important role for fracture aperture changes and micro-seismic activities during water injection in enhanced geothermal systems (EGS). In order to study the poro-mechanics of EGS, a finite volume method based on discrete fracture manifolds embedded in a continuum matrix domain has been developed. For the coupling between stress and fluid pressure in the matrix domain, an unconditionally stable fixed stress scheme is employed, in which the geo-mechanical and flow problems are solved sequentially. In order to get accurate fracture slip solutions and displacements within the matrix, special basis functions were introduced. The degree of freedom associated with these basis functions are computed by requiring stress equilibrium and by honoring the Coulomb friction law. Finite sized fracture segments are used to estimate the shear failure criterion and the subsequent evolution of slip and aperture. Numerical investigations of micro-seismic activities show that the moment magnitude against frequency closely follows the Gutenberg-Richter law. While numerical convergence of slip and pressure solutions is achieved, the smallest size of micro-seismic events depends on the fracture resolution.

Press the Back button in your browser, or search again.

Copyright 2016, Stanford Geothermal Program: Readers who download papers from this site should honor the copyright of the original authors and may not copy or distribute the work further without the permission of the original publisher.