Development of a novel dynamic formation stimulation technique: FDEM-based numerical modelling results

The goal of this paper is to provide an overview of numerical simulation results aiding the development of a novel pulsed combustion-based wellbore fracturing technology. The technology can be used as a pre-conditioning and stimulation tool for in-situ recovery and cave mining, enhanced geothermal systems, and unconventional hydrocarbon reservoirs. Numerical simulations were carried out using a finite-discrete element method (FDEM) code, capable of explicit consideration of rock fracturing processes and dynamic phenomena. A parametric study on the effect of borehole pressurization characteristics and geostatic confinement highlighted the influence of these factors on fracture complexity and radial extent. An in-depth analysis of the extent of the crushed zone and radial distributions of fracture specific surface area was carried out. Borehole pair configurations were simulated to investigate borehole spacing and loading sequence effects. The simulations provided the following key findings: (a) for a set of fracturing parameters there exists a maximum borehole spacing beyond which fracture networks no longer intersect; (b) simultaneous fracturing of borehole pairs produces a compounding effect that induces higher inter-borehole fracturing compared to sequential fracturing; (c) the incorporation of a coupled in-fracture gas pressure propagation logic has substantial positive effects on the radius of the induced fractured zone.