An integrated approach of measuring permeability of naturally fractured shale

During the past decade, despite the rapid development of shale resources, it is still facing a great challenge of determining reliable petrophysical properties of both nonfractured and fractured shales. In this study, we innovatively combine a discrete fracture network model and a single-porosity model to simulate the pulse-decay experiments using one fractured Barnett shale plug to obtain accurate properties for both matrix and fracture. The workflow consists of two stages: 1) estimate roughly porosity and permeability for the matrix and fracture by history-matching pressure curves in the single-porosity model and 2) simulate the fracture geometry more realistically considering fracture roughness based on the discrete fracture network model. The fracture geometry is depicted explicitly in two dimensions. The effect of fracture roughness on flow behavior is explored in terms of different values of Dykstra–Parsons coefficients (Vdp): 0, 0.06, 0.29, and 0.47. Our simulated results match the experimental data excellently, with a global average absolute relative deviation (AARD) being within the order of 1E-4. The fracture permeability estimated from the pulse-decay experiment will be underestimated if fracture roughness is ignored. Therefore, the fracture permeability should be adjusted to compensate for the effect of fracture roughness.