Numerical Simulation Study on Influence of Multi-seam Propagation of Hydraulic FRACTURE in Coal Seam

Abstract

Multi-stage fracturing technology for horizontal Wells is one of the effective methods of coal seam volume reconstruction at present. This technology can effectively form a volumetric seam network, increase the volume of coal seam segment reconstruction, increase the area of gas seepage channel, and reduce the generation of coal powder. In order to study the mutual interference of multi-fracture extension in hydraulic fracturing of coal seam and to solve the problem of unclear effect of fracturing construction parameters in coal seam at present, this paper, based on the extended finite element method (XFEM), conducts fluid-solid coupling simulation using pore pressure element (C3D8P), and establishes a calculation model of multi-fracture extension in coal seam. This model is used to study the influence of perforating cluster number, cluster spacing and non-uniformity on hydraulic fracture propagation. The calculated results indicate that, with the increase of the number of perforating clusters, the surface stress field is disturbed more seriously by fractures, and the volume of formation reconstruction also increases correspondingly. After comprehensive comparison, it is believed that the optimal fracturing effect can be achieved when two clusters of perforating clusters are used. The larger the cluster spacing, the smaller the inter-fracture interference, and the higher the formation pore pressure during fracturing. The non-uniformity between clusters has a great influence on fracture propagation. When the displacement of the middle cluster is 1/4, the inhibition effect is severe and it is difficult to form effective fracturing fracture. Finally, the model is used to optimize the multi-stage fracturing construction parameters of horizontal well in coal seam, which provides reference and guidance for the design of hydraulic fracturing scheme.