Pressure performance of interlaced fracture networks in shale gas reservoirs with consideration of induced fractures

Abstract

Multi-stage fracturing in shale gas reservoirs may create complex fracture network around horizontal wellbore, due to the widely-distributed natural fractures. However, little work has been done to investigate the effects of secondary fractures on well testing models for shale gas reservoirs. In this paper, a more comprehensive model was developed for interlaced fracture networks in shale gas reservoirs with consideration of multiple transport mechanisms and different flow states. By employing the source function and Laplace transformation, the line sink solutions for four kinds of flow states were unified. Based on the discretization method and unified line sink solution, the pressure responses for interlaced fracture networks with infinite conductivity were obtained. Type curves were plotted and typical flow regimes of this model were identified. In order to have a further understanding of the effect of induced fractures, the slope curves of pseudo-pressure derivative were introduced to analyze the interference between fractures. The influences of the angel and the length of induced fractures on the well testing curves were simulated by the semi-analytical model for the first time. Then, the flux distributions of interlaced fracture networks were simulated and discussed for achieving significant advice. Finally, the proposed model was verified by a simplified case and a field case. The presented model will be helpful for understanding the transient performance of multi-stage fractured horizontal wells with consideration of induced fractures.