Low porosity and low permeability of shale gas reservoirs require hydraulic fracturing and other methods to achieve economic productivity. The shape and distribution of fractures are very important to the volume transformation. In order to study the simulation methods of hydraulic fracture, the common methods of reservoir hydraulic fracture simulation are systematically investigated and compared, and the extended finite element simulation is carried out. The results show that: (1) The physical experiment of hydraulic fracturing can visually observe the fracture morphology and distribution characteristics, but it is difficult to represent the actual fracturing situation of the reservoir due to the sample size and other problems. (2) The commonly used numerical simulation methods include boundary element method (BEM), unconventional fracture model (UFM), discrete fracture network (DFN) and extended finite element method (XFEM). These methods have their own advantages and disadvantages, which need to be improved to better simulate the real shale reservoir fracturing. (3) The extended finite element method is used to simulate the fracture extension of hydraulic fracturing and staged sequential fracturing. The influence of the angle between the perforation direction and the direction of the maximum horizontal principal stress and the induced stress on the fracturing pressure is obtained. The larger the angle is, the smaller the fracture deflection angle is, while the larger the fracture deflection distance is. The larger the angle is, the higher the initial fracturing pressure is, and the greater the pressure of stable fracture extension is. The induced stress will hinder the fracture extension. The simulation results have guiding significance for the selection of perforation direction and the design of perforation spacing in staged fracturing in actual engineering.
ZHANG Ying-kun, CHEN Shang-bin, LI Xue-yuan, WANG Hui-jun. Hydraulic fracturing simulation technology of shale gas reservoir and application of extended finite element method. Natural Gas Geoscience[J], 2021, 32(1): 109-118 doi:10.11764/j.issn.1672-1926.2020.11.006
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