Mohammad Fatehi Marji - PhD of Rock Mechanics, Department of Mining and Metallurgy, Yazd University | Yazd, Iran
Meysam Lak - Professor, Department of Mining and Metallurgy, Yazd University | Yazd, Iran
Manouchehr Sanei - Assistant Professor, Department of Mining and Metallurgy, Yazd University | Yazd, Iran
Abolfazl Abdollahipour - Assistant Professor, School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran

Explosive fracturing can be used to increase the permeability and productivity of low permeable reservoirs. The mentioned fracturing process is the same as hydraulic fracturing but uses shock wave and gas pressure resulted from blasting to generate and propagate radial cracks around the wellbore in a particular reservoir. In this article, the dynamic cracking process of deep rock caused by explosive initiation is studied both analytically and numerically, the mechanical process of rock cracking under the action of explosion stress wave is theoretically analyzed and simulated with finite difference method. Then the coupling effect of explosion load in form of shock wave and gas pressure is established numerically based on the two-dimensional explicit finite difference and indirect boundary element methods, respectively. The analytical method involved the solution of the Lame-Navier equation in elasto-dynamics based on the Green’s function solution. The simulation procedure consists of coupling the explicit finite difference method with indirect boundary element method in form of higher order displacement discontinuities along the boundaries of the problem. The numerical results of this research show that shock waves are responsible for initiation of radial cracks around the wellbore which in turn filled with pressurized gas due to explosion. Then, these shock wave induced radial cracks are propagating in the reservoir rock because of the explosive gas pressure inside them. This rock fracturing mechanism can help to improve the permeability and productivity of the highly low permeable reservoirs in horizontal wells.

Explosive rock fracturing, Green’s function, Finite difference method, Boundary element method, Radial cracks, Unconventional reservoirs