POROMECHANICAL RESPONSE OF FRACTURED-POROUS ROCK MASSES

An analytical model based on a poromechanical formulation for dual-porosity media is presented. In comparison with traditional conceptualizations such as by Barenblatt et al. (1960), the proposed model contains both additional terms in the governing flow equations to provide a physically more realistic description of the change in storage, and a natural accommodation of body displacements. Solution is developed for radial flow in a reservoir subject to the conditions of both constant bottom hole pressure and constant flow rate using Hankel transforms. The poromechanical effect, resulting from the coupling between fluid flow and solid deformation, is significant in the well vicinity where the modifications of initial pressure and stress state are substantial. Different from the conventional approach in which the impact of fluid properties is generally emphasized, the presented case studies highlight the critical influence of mechanical properties of the fractured rock mass on the change of fluid pressure in a producing reservoir. The study indicates that dual-porosity behavior is most obvious only when the poromechanical properties fall within a certain range.