Abstract Borehole breathing observed while drilling naturally fractured formations was often mistakenly interpreted as the influx of formation fluid or the loss of drilling fluids. Amongst several mechanisms that were caused for borehole ballooning, the opening and closing of finite fractures played a major role in naturally fractured formations. In this study, a novel experimental setup was designed to simulate the borehole breathing under different conditions. In this experiment, the typical characteristics of borehole breathing event under different pressure conditions and rock types were studied. Additionally, the influence of three important parameters on the cumulative loss of mud caused by borehole breathing was also investigated in detail. The results show that mud circulation pressure, fracture opening pressure and rock type had important influences on the maximum loss of mud and the speed at which the borehole breathing event occurs of borehole breathing, and were the key parameters for predicting the cumulative loss of mud. Based on analysis of the results, a new parameter, breathing coefficient αb which can be used to evaluate the borehole breathing event, was proposed, and its magnitude was proportional to the severity of the borehole breathing. This study provides theoretical support for the study of borehole breathing.

中文翻译：

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不同压力和岩石类型条件下钻孔呼吸典型特征试验研究

摘要 在天然裂缝性地层钻井过程中观察到的钻孔呼吸常被错误地解释为地层流体的流入或钻井液的流失。在导致井眼膨胀的几种机制中，有限裂缝的打开和闭合在自然裂缝地层中起着重要作用。在这项研究中，设计了一种新颖的实验装置来模拟不同条件下的钻孔呼吸。本实验研究了不同压力条件和岩石类型下钻孔呼吸事件的典型特征。此外，还详细研究了三个重要参数对钻孔呼吸引起的泥浆累积损失的影响。结果表明，泥浆循环压力、裂缝张开压力和岩石类型对泥浆最大损失和钻孔呼吸发生的钻孔速度有重要影响，是预测泥浆累积损失的关键参数。在分析结果的基础上，提出了一个新的参数，呼吸系数αb，可用于评价钻孔呼吸事件，其大小与钻孔呼吸的严重程度成正比。该研究为钻孔呼吸的研究提供了理论支持。提出了可用于评价钻孔呼吸事件的呼吸系数αb，其大小与钻孔呼吸的严重程度成正比。该研究为钻孔呼吸的研究提供了理论支持。提出了可用于评价钻孔呼吸事件的呼吸系数αb，其大小与钻孔呼吸的严重程度成正比。该研究为钻孔呼吸的研究提供了理论支持。