Semi-analytical simulation of transient flow behavior for complex fracture network with stress-sensitive conductivity

The main object of this paper is to establish a benchmark model to investigate the transient flow behavior for complex fracture network with stress-sensitive conductivity. An associated semi-analytical solution is proposed by coupling reservoir-fracture flow model and incorporating stress sensitivity of fracture conductivity into coupled model, with sufficient flexibility to account for complex fracture geometry and stress sensitivity. A dimension transformation with multiple source terms is fully developed and extended to the case of complex fracture network, which renders the resulting nonlinear equations fully amenable to the linear treatment. An accurate, closed form iterative algorithm is subsequently provided and verified against numerical reservoir simulator. A set of synthetic simulations is utilized to investigate the physics of transient flow behavior and capture the interaction between fracture-production interference and conductivity decay by performing pressure transient analysis. The results show that the pressure response transitions from the initial condition (constant initial-conductivity) to the limited condition (constant minimum-conductivity) because of the loss of stress-sensitive conductivity, displaying a gradual increasing in the pressure drop. The magnitude of extra pressure drop is dependent on the complexity nature and conductivity decay of fracture network. In the condition of high flow resistance (i.e. low initial conductivity, small area connected to the reservoir), it is of great significance to take the effect of stress sensitivity into account to obtain correct simulation of transient pressure response. The findings in this paper could improve the understanding of flow mechanisms and facilitate the analysis of transient pressure/rate data for complex fracture network with stress-sensitive conductivity.