Abstract
How to improve drill bit working efficiency in deep drilling has been a wide concerned issue in petroleum industry. Utilizing ultra-high-pressure water jet to groove the bottom hole rock and reconfiguration the stress field is considered an effective method to improve the rock breaking efficiency and improve rate of penetration. However, there is currently no relevant report available on the effect of groove characteristics, which are important factors affecting rock break efficiency. Therefore, this study combines lab test with numerical simulations to analyze the effects of rock groove characteristics under the simultaneous action of confining pressure and hydrostatic pressure on cutting force, energy consumption of rock breaking, cutting size, cutting trajectory morphology, stress distribution characteristics, crack characteristics, and failure modes. The research results show that increasing groove depth and number significantly reduce cutting force, enhance rock fragmentation mass, and significantly improve rock breaking efficiency. There exists a threshold for specific energy consumption of rock breaking under different groove characteristics, with a 35.17% decrease in energy consumption of rock breaking at a cutting depth of 15 mm, and the lowest energy consumption of rock breaking when the number of grooves is 2. The reduced compressive effect of the confining pressure on the rock after grooving decreases the inhibitory effect on internal crack propagation and the increase in internal cracks and the higher percentage of tensile failure contribute to the increased rock breaking efficiency. This study provides theoretical and technical guidance for ultra-high-pressure water jet drilling technology.
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