Hydraulic DTH Fluid / Mud Hammers with Recirculation Capabilities to Improve ROP and Hole Cleaning For Deep, Hard Rock Geothermal Drilling

Geothermal resources tend to be found in deeper and harder geologic formations than typical hydrocarbon reservoirs. Therefore, drilling technologies and processes from the oil & gas field need to be improved constantly to make for more efficient and economic drilling. Drilling speeds or rate of penetration (ROP) of classic drilling technologies, e.g. tricone bits, suffers greatly in deep and hard formations. Thus, there is a great need for tools with higher ROP and low wear to reduce drilling, trip time and cost. Down-the-hole hammers (DTH) using compressed air have successfully been proven for decades in shallow drilling < 400 m depth. To reach greater depth, the working medium must rather be a liquid, due to the compressibility of air and the possible need of drill mud for borehole stability.

One of those improvements over the past ten plus years has been the development and application of hydraulic downhole hammer systems at GZB in Bochum and elsewhere worldwide for geothermal, hydrocarbon, and mining drilling applications. However, several disadvantages of these hydraulic, so far mainly clean water hammer systems, held back their widespread use so far. Main hindrances were e.g. water quality of almost clean tap water, missing recirculation systems and thus, no possibility of using drill mud additives for borehole control and improved hole flushing capabilities. With new hydraulic hammer systems being developed in Bochum, Germany and coming onto the market elsewhere, most of these problems have been addressed, if not solved up to now, also pushing their drilling capabilities further down to beyond 5.000 m depth. Work has been done and will be presented here on a summary on past and current hydraulic hammer technologies. Beginning with an introduction to main basic working principles, different hammer types are discussed. The results of recent field tests are being presented. Furthermore, recirculation units for hammer drilling, multiple phase or, respectively, fluid flows, and the potential product of DTD mud powered hammers are being shown and discussed.

These innovative, DTH hammer tools will greatly help the geothermal or other deep drilling industry to make their drilling efforts far more economic, especially but not exclusively, in deep, hard rock drilling situations. Furthermore, hard sedimentary rocks may be drilled much more economically with hydraulic mud hammers being able to be powered by (light) mud and thus, allowing for good borehole control.

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Zusätzliche Information

Advanced Drilling Technologies

GZB – International Geothermal Centre

Bochum University of Applied Sciences

Lennershofstrasse 140
44801 Bochum
Germany

Dipl.-Ing. Volker Wittig

Leiter der Abteilung Advanced Drilling Technologies

Raum: G1 1-003
Tel.: +49 (0)234 32-10768

Volker Wittig

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