Numerical simulation method for hydraulic fracture pressure of perforated surrounding rock under hydraulic coupling
ZHANG Yu1,2, WANG Peng-sheng1, LI Da-yong1, ZHANG Yu-kun2, WEI Kai3
1. College of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao 266580, China; 2. Key Laboratory of Civil Engineering Disaster Prevention and Mitigation, Shandong University of science and Technology, Qingdao 266590, China; 3. Petroleum Engineering College, Yangtze University, Wuhan 430100, China
Abstract：A numerical simulation method for hydraulic fracture pressure of perforated surrounding rock under hydraulic coupling is proposed using the FVM based on the coupling theory of fluid flow of porous media and stress of surrounding rock. Firstly, considering the influences of the initial geo-stress and fluid flow in the perforated surrounding rock, the stress distribution of the surrounding rock is obtained through the coordinate conversion and superposition principle. Secondly, considering the stress sensitivity of permeability and porosity of surrounding rock, the fluid pressure field of perforated surrounding rock is determined through the fluid flow analysis. Finally, on the basis of discussing the fracture criteria for the perforated surrounding rock during hydraulic fracturing, a mechanical model for hydraulic fracture perforated surrounding rock considering hydraulic coupling is established. The flow equation and the stress equation are discretized by the finite volume method, and a numerical simulation method for hydraulic fracture under hydraulic coupling is proposed. The method realizes the coupling of fluid flow and stress of surrounding rock, which can accurately calculate the breakdown pressure and time of hydraulic fracture of perforated surrounding rock under hydraulic coupling, and can also accurately describe the fluid pressure field and permeability evolution of surrounding rock. The results illustrate that the stress sensitivity of permeability and porosity induces the more uniform distribution of fluid pressure, the permeability and fluid pressure near the well area increase, the seepage influence range expands, and the fracture pressure and time of surrounding rock decrease. The relevant results enrich the researches on breakdown mechanism of hydraulic fracture and also provide important reference for practical engineering.
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