Development of a Novel Dynamic Wellbore Fracturing Technology by Integrating Full-Scale Experimental Testing and FDEM Numerical Simulations

The goal of this paper is to provide an overview of the development of a novel pulsed combustion-based wellbore fracturing technology by reporting on 2D and 3D dynamic fracture modeling along with the associated full wellbore scale experimental demonstration fracturing of a high-strength concrete formation surrogate. With this technique a high pressure, gaseous mixture is rapidly combusted to produce repetitive, controllable wellbore strain rates that can induce complex fracture patterns around the wellbore. 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. As part of this study, full-scale experimental testing on a rock-like material was conducted together with advanced numerical simulations based on the finite-discrete element method (FDEM). FDEM is a numerical approach capable of explicit consideration of rock fracturing processes and dynamic phenomena. Experimental results indicate that the fracturing tool can successfully apply a circumferentially and axially uniform high pressurization rate pulse to the wellbore, ultimately producing a complex fracture network. These results were also used to validate 3D numerical simulations, which showed good overall qualitative agreement in terms of fracturing modes and extent, as well as fragment size and shape. A 2D numerical parametric study on the effect of borehole pressurization characteristics, including gas-in-fractures effects, 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 gain insights into borehole spacing and loading sequence effects.