Application of Oda's Permeability Tensor for Determining Transport Properties in Fractured Sedimentary Rocks: A Case Study of Pliocene-Pleistocene Formation in TCDP

The fluid flow characteristics are critical for fault dynamics. However, the influence of fracture networks on the permeability is difficult to be evaluated, especially near an active fault zone. In this study, the permeabilities of rock masses near the Taiwan Chelungpu-fault Drilling Project (TCDP) site are evaluated based on a pseudo-continuum model, Oda's model. The influence of the orientation, size, and aperture of fractures, as well as the fracture density are considered. Additionally, the influence of stress is considered with utilizing a stress dependent aperture. Accordingly, the inherent and stress induced anisotropy of permeability can be depicted. The permeabilities, between 2.67 x 10(-13) and 2.11 x 10(-14), tend to decrease with increasing depth. The orientation of maximum permeability k(1) approaches the preferred orientation of fractures, indicating the orientation of fractures dominantly control the permeability of rock masses. Results indicate the permeabilities of fractured sedimentary rock are obviously affected by crack preferred orientation and anisotropic in situ stress states.