Numerical simulation study of the influencing factors of electric explosion shock waves on reservoir fracture initiation

Abstract:

The electric blast shock wave has great application potential in increasing permeability and removing plugs of oil and gas reservoirs. In this paper, ANSYS/LS[CD*2]DYNA software is used to investigate the influencing factors of electric blast shock wave induced cracks through variation of the in situ stress, elastic modulus and tensile strength. The simulation results show that the in situ stress has a strong inhibitory effect on crack propagation. Under action of the two way isobaric in situ stress, the shape of the crack zone is circular, and with increase of the in situ stress, the fracture degree and fracture radius of the rock mass decrease gradually. Under action of the bi directional unequal compressive in situ stresses, as the difference between the horizontal principal stresses increases, the direction of crack propagation gradually changes from circular to elliptical, exhibiting the characteristic of extending along the direction of the maximum horizontal principal stress. The elastic modulus has important effect on crack initiation: with increase of the elastic modulus, the fracture degree and fracture radius of the rock mass increase. As the tensile strength increases, the fracture degree and fracture radius of the rock mass decrease.