Study on the Mechanism of Charge Jet Penetration and Damage Induced Cracking in Deep Shale Reservoirs
In order to study the influence of in-situ stress on the penetration of shaped jets into shale reservoirs,a quasi-two-dimensional model of shaped jets penetrating shale under different confining pressures was established,and the shale confi-ning pressures loaded by dynamic relaxation method were 0,10,20 and 30 MPa,respectively,and the fracture mechanism of shale damage caused by jet penetration was systematically analyzed from the aspects of perforation depth,shale pore fracture formation law characteristics and stress changes at monitoring points.The results show that the damage area of shaped jet after penetration into shale can be divided into complete failure zone,compression-shear failure zone and tensile failure zone,and the failure area decreases due to the increase of confining pressure.The penetration depth of shale without confining pressure is 600.3 mm,and the penetration depth of shale under 10,20 and 30 MPa confining pressure decreases to 524.3,454.3 and 446.1 mm,respectively,with a reduction range of 12.66%,24.32%and 25.69%,respectively.The peak pressure of shale perforation decreases rapidly with the increase of the distance from the center of aperture,and the attenuation rate gradually de-creases from fast to fast,and decreases gradually with the increase of the distance from the starting point of penetration,and the decreasing trend is approximately linear.
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