Shi Xiangchao, Chen Shuai. Rock drillability index testing and grading method verification[J]. Acta petrolei sinica, 2025, 46(9): 1792-1804. DOI: 10.7623/syxb202509011.
Rock drillability index testing and grading method verification
Rock drillability evaluation is an important basis for opitimizing drilling acceleration tools and parameters. A scientific and reasonable assessment of rock drillability is vital to drilling engineering. Drillability testing and classification methods need continuous improvement to keep pace with the development of drilling technology
and their scientific validity requires repeated verification. Thus
experiments were conducted on various rock samples with different strengths and lithologies. The rationality
repeatability
and universality of the rock drillability index testing and classification methods were explored by comparing with the foreign SJ drillability testing and corresponding methods. The research results show that:(1)Under a drilling pressure of 1.0 kN
the improved PDC micro drill bit can effectively solve the slipping problem in hard formations. The improved roller cone micro drill bit
operating at a rotational speed of 90 r/min
has effectively addressed the issues of restricted cone-tooth rotation and excessive tooth wear. (2)For hard formation rocks
the drillability testing methods for PDC and roller cone micro drill bits demonstrate better repeatability compared to the SJ drillability testing method. (3)The improved PDC and roller cone drillability testing methods significantly reduce the proportion of invalid test results
better adapting to current advances in drilling technology. (4)The drillability classification method facilitates the differentiation of rock drilling difficulty
while also establishing an extensible framework for future evaluation of drillability in harder rocks under bottom-hole pressure conditions.
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