Geothermal drilling technologies: A multidisciplinary review of thermo-mechanical limits, rock–fluid interactions, and next-generation solutions

Geothermal energy presents a vast and underutilized source of carbon-free baseload power, yet its development remains constrained by severe drilling challenges in high-pressure and high-temperature (HPHT) and chemically reactive environments. Unlike sedimentary oil and gas formations, geothermal reservoirs are often composed of hard crystalline rocks, fractured zones, and fluid systems with extreme salinity, acidity, and mineral scaling potential. These conditions induce rapid bit wear, frequent tool failure, fluid instability, and wellbore collapse, making conventional rotary systems technically and economically inadequate.This review critically examines the fundamental limits of geothermal drilling systems, focusing on the coupled thermo-mechanical, hydraulic, and geochemical processes that govern performance in extreme subsurface conditions. It synthesizes emerging innovations across five interrelated domains: (1) advanced bit and bottom-hole assembly (BHA) design, (2) high-temperature drilling fluids and lost circulation control, (3) non-mechanical penetration technologies such as laser, plasma, and electro-pulse systems, (4) high-temperature sensing and autonomous digital twin control architectures, and (5) future paradigms in subsurface materials, self-healing cements, and in situ additive manufacturing. Special emphasis is placed on supercritical and ultra-deep geothermal systems where traditional assumptions on tool reliability and well integrity no longer hold.By integrating insights from geothermal geomechanics, rock-fluid interactions, drilling thermodynamics, and intelligent control, this paper provides a strategic research roadmap and technology framework for overcoming the barriers to next-generation geothermal energy.