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Application of high powered Laser Technology to alter hard rock properties towards lower strength materials for more efficient drilling, mining, and Geothermal Energy production

Jamali, S. and Wittig, V. and Börner, J. and Bracke, R. and Ostendorf, A.

GEOMECHANICS FOR ENERGY AND THE ENVIRONMENT
Volume: Pages:
DOI: 10.1016/j.gete.2019.01.001
Published: 2019

Abstract
Resources such as minerals, geothermal energy, and unconventional hydrocarbons need to be excavated from deeper and harder geologic formations than in the past 100 years. Although, oil & gas drilling technologies have been continuously enhanced to enable more efficient and economic drilling processes, yet their performance suffers significantly in deep and hard formations. Problems mainly include low rate of penetrations, very high drill-bit wear-rates, short drill bit service life, and ultimately result in a high overall drilling cost. Laser Jet Drilling could potentially be such next fundamental drilling process for delivering more and alternative energy to the bit and breaking the rock more efficiently and thus, substantially improve drilling of deep hard rock formations. The application of high-power laser for rock breaking and drilling processes has been demonstrated in this study via Laser (thermally) induced rock softening. A comprehensive experimental approach has been chosen to study the LaserJet drilling process and its rock interaction. Multiple rock types including sandstones, granites, and metamorphic quartzite rocks were characterized to offer a comprehensive overview of possible effects of rock parameters on laser–rock interaction. The initial research results proved that various rock types including very hard ones could be transformed into a drillable state using a high-power laser through thermally induced rock softening. The rock strength, drilling strength and fracture toughness of the studied samples were obtained by means of scratch testing. The overall analysis of the results suggests that thermal rock softening allows to efficiently facilitate a combined laser mechanical assisted drilling system with a possible increase in the rate of penetration of the cutting tool with reduced drilling torque and weight on bit requirements and therefore having a lower energy consumption. Additionally, the drilling costs could be noticeably lessened by improving the drill bit life and reducing the overall drilling time. © 2019

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