Hydro-Mechanical Feed-Back Coupling in a Fluid-Filled Fractured Rock: Stress-Dependent Macro-Scale Permeability and Porosity

International audienceWe address Hydro-Mechanical (H-M) feed-back coupling in a fluid-filled fractured rock, whereby the hydraulic conductivity of the fractured rock is modified by its deformation. We present an upscaled description of this coupling based on previous work on tensorial macro-permeability (Kij) of fractured rock. The H-M feed-back coupling effects are expressed for the 2D case with fractures as straight line cracks, and for the 3D case with fractures as planar disc cracks. We assume at first that the deformable rock matrix remains impervious: feed-back effects are then due solely to crack deformation, while the effect of matrix deformation on Kij is neglected. The resulting tensorial H-M sensitivity coefficients, (K′ijkl) and (δ′kl), are expressed explicitly. Extensions of this work are indicated in the conclusive section, e.g.: strain of the permeable porous matrix; thermal expansion; and combining all types of H-M couplings (stress/pressure/fluid production coupling, as well as feed-back coupling)