Linking microearthquakes to fracture permeability evolution

This chapter evaluates aperture distributions and fluid flow characteristics for variously sized laboratory-scale granite fractures under confining stress. The contact area in fracture plane was found to be virtually independent of scale for the investigated samples. By combining this characteristic with the self-affine fractal nature of fracture surfaces, a novel method for predicting fracture aperture distributions beyond laboratory scale is developed. The chapter discusses fracture permeability enhancement by micro-earthquakes during hydraulic stimulation of a fractured reservoir. Researchers recently developed a novel 3D fracture network model simulator, in which fractures are characterized by 2D heterogeneous aperture distributions. The ability of this simulator to analyze 3D channeling flow in a fracture network has been demonstrated in a laboratory multiple-fracture flow experiment. The fracture aperture distribution and resulting fluid flow characteristics, such as permeability and flow paths, are known to be constrained by fracture-surface topography, shear displacement, and confining stress.