To improve the economics and viability of accessing deep georesources, we propose a combined thermo–mechanical drilling (CTMD) method, employing a heat source to facilitate the mechanical removal of rock, with the aim of increasing drilling performance and thereby reducing the overall costs, especially for deep wells in hard rocks. In this work, we employ a novel experiment setup to investigate the main parameters of interest during the interaction of a cutter with the rock material, and we test untreated and thermally treated sandstone and granite, to understand the underlying rock removal mechanism and the resulting drilling performance improvements achievable with the new approach. We find that the rock removal process can be divided into three main regimes: first, a wear-dominated regime, followed by a compression-based progression of the tool at large penetrations, and a final tool fall-back regime for increasing scratch distances. We calculate the compressive rock strengths from our tests to validate the above regime hypothesis, and they are in good agreement with literature data, explaining the strength reduction after treatment of the material by extensive induced thermal cracking of the rock. We evaluate the new method’s drilling performance and confirm that thermal cracks in the rock can considerably enhance subsequent mechanical rock removal rates and related drilling performance by one order of magnitude in granite, while mainly reducing the wear rates of the cutting tools in sandstone.

中文翻译：

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热处理对岩石-钻头相互作用的影响：热-机械联合钻井（CTMD）概念的研究

为了提高获取深层地质资源的经济性和可行性，我们提出了一种热力机械钻探（CTMD）组合方法，该方法采用热源来促进岩石的机械清除，目的是提高钻探性能并从而降低总体成本，特别是对于硬岩石中的深井。在这项工作中，我们采用一种新颖的实验装置来研究刀具与岩石材料相互作用期间的主要参数，并测试未经处理和热处理的砂岩和花岗岩，以了解潜在的岩石去除机理和由此产生的钻探。新方法可实现性能改进。我们发现，岩石去除过程可以分为三个主要阶段：首先是磨损为主的阶段，随后是在大穿透力下基于压缩的工具前进，以及最终的工具回退机制以增加划痕距离。我们通过我们的测试计算了岩石的抗压强度，以验证上述状态假设，并且它们与文献数据非常吻合，解释了由于岩石的广泛诱发的热裂化处理材料后的强度降低。我们评估了新方法的钻探性能，并确认了岩石中的热裂纹可以大大提高花岗岩中后续机械岩石的去除率和相关钻探性能一个数量级，同时主要降低了砂岩中切削刀具的磨损率。我们从我们的测试中计算出岩石的抗压强度，以验证上述条件假设，并且它们与文献数据非常吻合，解释了由于岩石的广泛诱发的热裂纹对材料进行处理后强度降低的原因。我们评估了新方法的钻探性能，并确认了岩石中的热裂纹可以大大提高花岗岩的后续机械岩石去除率和相关钻探性能一个数量级，同时主要降低了砂岩中切削刀具的磨损率。我们从我们的测试中计算出岩石的抗压强度，以验证上述条件假设，并且它们与文献数据非常吻合，解释了由于岩石的广泛诱发的热裂纹对材料进行处理后强度降低的原因。我们评估了新方法的钻探性能，并确认了岩石中的热裂纹可以大大提高花岗岩中后续机械岩石的去除率和相关钻探性能一个数量级，同时主要降低了砂岩中切削刀具的磨损率。