RESPONSE OF FRACTURED ROCK SUBJECT TO FLUID INJECTION .2. CHARACTERISTIC BEHAVIOR

Distinct element modelling has been used to investigate the mechanics of naturally fractured reservoirs subject to a constant rate of fluid injection. Constant stress boundary conditions were imposed, with magnitudes typical of those pertaining at approximately 3 km depth in some sedimentary environments. Fluid leak-off through fracture walls and fracture dilation during shear were modelled. The progressive nature of the changes of stress and displacement occurring within the coupled fluid-rock system were examined for four combinations of uniform fracture geometry and applied stress. The effects of a uniform change of pore pressure on the directional nature of hydraulic conductivity in a fractured medium were characterised. The influence of variation of injection rate, pore fluid compressibility and leak-off rate was examined. Effects associated with contrasts of shear stiffness between fractures and blocks, and with inelastic deformation, were interpreted. © 1990.