A multi-fracture balanced extension control method for horizontal wells in anisotropic shale

Abstract

Shale has anisotropy in elastic parameters and permeability coefficient in parallel and perpendicular directions to the bedding plane. In the study of fracture propagation during hydraulic fracturing, it is necessary to consider the influence of shale anisotropy. Through the development of fluid pipe element, fluid pipe connector element, cohesive damage element, and rock matrix element with pore pressure, a fluid–structure coupling numerical model with comprehensive consideration of dynamic flow distribution, dynamic fracture propagation and extension, and stress interference are established. The anisotropic characteristic parameters of shale reservoirs are given to study the balanced propagation control method of multi-fracture in horizontal shale Wells. The results show that under anisotropic conditions, hydraulic fractures are easy to expand in the direction parallel to the bedding plane but not in the direction perpendicular to the bedding plane. Finally, It forms a long extension in the length direction and a short extension in the height direction. The stress interference along the direction of the minimum horizontal principal stress is gradually intense with the increase of the degree of anisotropy. During multi-fracture propagation in horizontal shale wells, the stress interference generated in the direction of minimum horizontal principal stress can be balanced by effectively controlling the perforation friction so as to promote the balanced extension of multiple fractures. At the same time, with the increase of injection flow and the decrease of the distance between clusters, the stress interference degree gradually becomes serious. Therefore, it is necessary to strictly design how to control the perforation friction in the multi-fracture fracturing process of shale horizontal Wells with large flow rates and small cluster distances. The research conclusions provide a theoretical reference for the efficient development of shale petroleum resources.