Well test analysis for a well with stress-sensitive natural fracture permeability and stress-dependent hydraulic fracture conductivities

Abstract

The commonly used methods in dual-porosity systems assume constant reservoir permeability over an entire range of formation pressure and constant hydraulic fracture conductivity inside the fractures. In this paper, the hydraulic fracture conductivity and natural fracture permeability were considered as a function of pressure. Based on finite-conductivity vertical fracture bilinear flow model in stress sensitive dual-porosity reservoirs, the analytical solutions were solved by perturbation and Laplace transform method. The features of typical curves were studied. The pressure and pressure derivative curves with stress-sensitivity were compared with the curves without stress-sensitivity. The influences of inter-porosity coefficient, storativity ratio, wellbore storage coefficient, permeability modulus and the hydraulic fracture conductivity on the typical curves were analysed with different seepage regimes. The results show that both the pressure and pressure derivative curves move upward in pressure-sensitive formations, especially for the end of the curves. The upward trend behaves more obviously due to stress sensitivity of the fractures. Field examples were applied to verify the validity of the proposed model. The novel well test model improves the accuracy of well test interpretation results, which is essential to the design and evaluation of stimulation treatments in these reservoirs. [Received: August 21, 2017; Accepted: September 10, 2018]