World Geothermal Congress
May 21-26, 2021

ThermoDrill - Fast Track Innovative Drilling System for Deep Geothermal Challenges

Dimitra TEZA, Jörg BAUMGÄRTNER, Thomas STOXREITER, Karin REHATSCHEK, Stefan ESSL, Philipp MODER, Simone PALLESI, Alessandro BERTINI, Gary PORTWOOD, Alessio CECHI, Clément BAUJARD, Olivier SEIBEL, Alfredo RAMOS RODRIGUEZ, José Maria CASCAJO LÓPEZ, Alexander BUCHNER, Roland FASCHINGBAUER, Johann PLANK, Timon ECHT

[BESTEC GmbH, Germany]

Since 2015 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. Deep geothermal drilling operations often have to cope with high formation temperatures (200°C static) and hard and abrasive rock types (granite, gneiss, sandstone). This causes an overall slow drilling progress, not only because of low penetration rates but also because of more trips required due to an increased material wear. Based on technical and financial data from real deep geothermal hard rock drilling operations in Europe it was concluded that by 50% faster drilling in crystalline rock, a cost reduction of 30% can be achieved which should greatly provide a boost for the deep geothermal industry. Numerous high-pressure fluid jetting experiments with jet pressures of more than 2.500 bars in various ambient pressure regimes (up to 425 bars) were performed and demonstrated that hard rocks can sufficiently be cut, even under high backpressures, if the right jetting parameters (jet pressure, stand-off distance, hydraulic jet power) are chosen. Based on these findings, two unique drill bit prototypes (8 1/2 in size) were built. A high-pressure body was designed and integrated into the frame of an existing roller cone bit. The high-pressure fluid jet assisted rotary drilling system including the two bit prototypes and a novel geothermal drilling fluid was successfully tested in crystalline rock, in full scale drilling experiments performed in a drilling simulator. In these experiments, a maximum increase in penetration rate of more than 70% was achieved. A first experimental field trial of the complete ThermoDrill system in a 1.3 km deep well was performed in May 2019. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 641202.

        Topic: Drilling and Completion Technology Paper Number: 21072

         Session 11J: Drilling and Completion 6 -- Drilling Methods [Sunday 23rd May 2021, 01:00 pm]
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