In the ThermoDrill project, an interdisciplinary team of experts from research and industry has set itself the ambitious goal of developing a fast and cost-efficient drilling system based on an innovative combination of conventional rotary drilling and water jetting. The new technology will afford at least a 100% increase in the rate of penetration in hard rock, and an associated cost reduction of more than 30%.
The ThermoDrill consortium addressed the following research and development topics in order to achieve these goals:
Revolutionary and breakthrough drilling technology
Geothermal wells often have to be drilled through very hard rock formations. This takes state-of the art drilling equipment to its limits, resulting in an urgent need for a faster and more durable technology. The combination of conventional rotary drilling with high pressure water jetting has the potential to be the required game-changing technology. The high pressure jet cuts the rock surface in front of the drill bit, reducing the stress in the rock and thus significantly increasing the rate of penetration. The pressure is generated downhole, meaning that no additional surface infrastructure is required and high safety standards can be upheld.
Novel drilling fluid
The main functions of a drilling fluid include removing the cuttings from the borehole bottom, ensuring wellbore stability and cooling the drill bit. The ThermoDrill project set out to find a fluid which acts not only as a drilling fluid but also supports the jetting process. The newly developed fluid combines these two functions and allows for increased drilling performance while meeting stringent environmental standards.
Unique drill bit prototype
The drill bit needs to withstand the enormous hydraulic pressure transferred through the bit to the jetting nozzles. For this reason a novel high pressure body was designed and integrated into the frame of a roller cone bit. The extended nozzles allow quick and easy maintenance and exchange of worn-out parts, while also keeping the distance between the borehole bottom and the nozzle to a minimum.
Simulations and experiments
Assessing successful novel drilling approaches requires detailed knowledge of the drilling process and the interaction between the high pressure water jet and the rock. Simulation activities were therefore a central analytical element in the project. In addition, a large number of experiments were carried out to continuously optimise the current approach, as well as to make the ThermoDrill technology fit for future industrial use.