Key Technologies for Deep Geothermal Drilling: High-Temperature Rock Drilling and Fracture Activation

Key Technologies for Deep Geothermal Drilling: High-Temperature Rock Drilling and Fracture Activation

Developing deep geothermal energy requires drilling into high-temperature rock formations thousands of meters underground and artificially activating the natural fracture network within to form efficient heat exchange channels. This project faces severe challenges from extreme temperatures, hard rock formations, and complex geology. Its key technologies revolve around two core aspects: "drilling in" and "creating fractures."

The key to high-temperature rock drilling lies in heat-resistant equipment and cooling processes. When encountering formations exceeding 180°C or even 250°C, the metal materials of conventional drilling tools soften, and electronic instruments malfunction. Therefore, it is essential to use high-temperature resistant alloy drill pipes, special seals, and measurement-while-drilling (MSD) tools equipped with heat insulation and high-temperature chips. The drilling fluid (mud) system also requires specialized design, demanding not only stable performance at high temperatures but also excellent rock-carrying and cooling capabilities. High-flow-rate circulation is necessary to expel the massive heat generated by the drill bit from the wellbore, preventing equipment overheating and damage. Simultaneously, a high-temperature resistant blowout preventer must be installed at the wellhead to cope with potential high-pressure hot fluids.

Fracturation activation is the core process for creating geothermal reservoirs, typically achieved through hydraulic fracturing. In the target high-temperature rock formation, high-pressure fluid (usually cold water) is injected into the well. The immense pressure causes previously closed natural fractures in the rock to reopen and extend, while the rock undergoes rapid temperature alternation, creating micro-fractures and forming a crisscrossing network of artificial fractures. This network significantly increases the permeability and heat exchange area of the rock mass. Subsequently, through techniques such as tracer injection and microseismic monitoring, a three-dimensional map of fracture development can be created, assessing reservoir volume and connectivity. Finally, by injecting cold water into one well and producing steam or hot water heated by the rock mass in another, a complete geothermal extraction cycle is formed.

Deep geothermal drilling and activation engineering is a highly complex systems engineering project that integrates ultra-deep well drilling, high-temperature materials, high-pressure fluid mechanics, and sophisticated monitoring technologies. Successful practices can open the door for humanity to obtain stable and clean base-load geothermal energy, which is of great significance for the transformation of the energy structure.