A fully coupled hydro-mechanical phase-field framework for dynamic pulsed-power fracturing in fluid-saturated rocks

Pulsed power fracturing has been proposed as an alternative stimulation technology to increase fracture surfaces, avoid flow short-circuiting, and reduce water usage with a range of applications, including unconventional oil & gas, enhanced geothermal systems and critical mineral in-situ mining. However, the conversion efficiency of electrical energy into mechanical energy that drives rock fracture, especially in multiple-pulse scenarios, remains poorly understood due to the dynamic nature of the process in micro-seconds. Moreover, subsurface formations are usually fluid-infiltrated, the coupled interaction between fracture propagation and fluid flow under pulsed power fracturing has yet to be systematically analyzed and compared with pure solid description. To address these challenges, this study introduces a three-dimensional dynamic continuum modeling framework that fully couples dynamic fracture propagation and fluid flow with evolving hydro-mechanical properties. The phase-field method, enhanced with a damage-driving force that accounts for damage-induced poroelasticity evolution, is used to capture fracture propagation. The acceleration term is added to the momentum balance equation to account for stress wave propagation. Using empirical relationships derived from the existing literature, we model pulsed power as a time-dependent, depth-varying mechanical pressure applied to the boundary. These governing equations, constitutive laws, and boundary conditions are implemented in MOOSE using finite elements for spatial discretization, while advanced algorithms, including Newmark- β and Picard iteration, are used for temporal discretization and global solution. The implementation is qualitatively compared with laboratory experiments on both dry and fluid-saturated rock samples from fracture morphology and energy budget. We employ the computational tool to evaluate the governing factors controlling fracture-surface enhancement and energy-conversion efficiency. The key results show: (1) different crack initialization configurations yield a consistent crack pattern; (2) confinement and the presence of fluid inhibit dynamic fracture propagation; (3) increasing pulse duration can facilitate fracturing performance more than increasing the peak pulse pressure; (4) the borehole wall drainage condition affects crack front pressure and crack propagation. These findings provide insights into the fundamentals of pulsed power fracturing, reveal energy-partitioning mechanisms, and identify key factors to improve efficiency and scalability for field applications.