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Description
The Institute of Subsurface Energy Systems at Clausthal University of Technology is working on the project “Optimized Flush-Driven Hammer for Hard Rock in Geothermal Energy,” or OBH for short, which is funded by the Federal Ministry for Economic Affairs and Energy. The goal of this project is to develop a percussion drill that achieves greater drilling progress in hard rock formations than conventional drilling methods, thereby reducing drilling costs. Studies have shown that the percussion drilling method is significantly more effective in granite, gabbro, or gneiss than cutting or scraping methods.
Currently, there is no known downhole percussion drill that can be reliably operated under conditions similar to those of a purely rotary drilling tool, i.e., using drilling fluids, conventional filtration methods, and standard drill string components. To address this, the Institute of Subsurface Energy Systems is developing a 6 ¾-inch diameter fluid-driven rotary hammer designed to meet these requirements. The energy to operate the rotary hammer is derived directly from the kinetic energy of the drilling fluid; a secondary circuit or other form of energy conversion is not necessary.
A key objective of the project is to demonstrate the compatibility of the drill hammer with conventional drilling systems and components. Calculations and experiments on integrating a pulse system for transmitting data to the surface are planned, and concepts for implementing deviated drilling are being developed. Another objective is the design of a shock absorber to minimize mechanical recoil in the drill string. This protects sensitive drill string components downstream of the downhole hammer.
