Meikuang Anquan (Nov 2020)
Research on Influence of Lateral Pressure Coefficient on Hydraulic Fracturing Propagation Law in Coal Body
Abstract
In order to study the crack initiation characteristics of coal body under different lateral pressure coefficients during hydraulic fracturing, a fluid-solid coupling model of coal body is established by using particle flow software PFC2D. The law of crack propagation and the influence of lateral pressure coefficient on fracture propagation and kinetic energy evolution were analyzed. The results show that: hydraulic fracturing failure form of coal body is tensile shear failure. The cracks near to the injection hole are mainly caused by tensile failure. And the cracks farther from the injection hole produce more shear failure. When lateral pressure coefficient is in the range of 1.6 to 3.4, the crack initiation pressure decreases as the lateral pressure coefficient increases. Tthe hydraulic crack extension distance increases with the increase of the lateral pressure coefficient in the same time. When λ≥2.8,the fracture extends along the diagonal of the coal sample after turning. Its expansion rate shows a change from fast to slow. When the lateral pressure coefficient is increased, it not only promotes the development of hydraulic fractures, but also increases the expansion rates. However, with the increase of the lateral pressure coefficient, its influence on the fracture propagation rate gradually decreases.
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