The state of stress regimes in highly stressed deep rocks and the stress release process, crucial for improving ROP in deep geothermal drilling, remain largely unexplored. Recent progress has advanced several aspects related to this challenge. In rock destruction using HPWJ, innovative numerical modeling techniques have extended adaptive mesh Computational Fluid Dynamics (CFD) to address concentrated impinging pressure at extremely high Reynolds numbers in rotating jet scenarios. These models, validated against laboratory jetting tests under high confining and back pressures, generate detailed surface pressure inputs for solid deformation models, revealing the depths and rock types where stress-relieving grooves of desired depth can be achieved.
For percussive rock destruction, the ORCHYD project introduced a multiscale modeling framework to optimize bottomhole configurations (bit shape, insert position, groove depth, WOB, impact energy, etc.). Discrete and continuum approaches complement each other to model the bit-rock interface, linking the HPWJ system dynamics with rock fracturing models. An extended mechanical behavior database supports calibration and validation, while studies on enhanced drilling fluids indicate potential for environmentally friendly additives to improve tool life and particle transport. Future studies will assess the environmental impact of ORCHYD technology on global energy security.
Initial results demonstrated a 100% improvement in ROP under moderate rock confining conditions, and further optimization in the second period of the project, the ORCHYD prototype increased drilling rates fourfold in hard crystalline granites like Sidobre compared to conventional rotary systems. Anticipated operational savings could reduce hard rock section drilling costs by up to 65%, significantly impacting investments in deep geothermal projects. The combined HPWJ and DTH hammer process shows promise for applications in mining, energy storage, CO2 storage, environmental monitoring, and remediation, with numerical tools and experimental devices enabling tailored optimization for specific systems.
