救援钻孔用双钻头扭矩自平衡钻进系统理论与实验

快速安全构建应急救援通道是在矿山事故发生后解救井下被困人员的有效方法，常规救援井钻进技术主要有潜孔锤冲击钻进技术和复合钻进技术，存在钻机结构庞大、钻进工艺复杂、对地层扰动大和中靶率低等不足，尤其在破碎地层易产生二次事故，很难有效满足救援要求。为确保救援钻孔的地层适应性和孔壁稳定性，提出了双钻头扭矩自平衡钻进方法，建立了双钻头逆向驱动数学模型，通过独立逆向驱动内外2个钻头实现双钻头的同步逆向回转碎岩，上部钻具主要受简单的轴向拉压力作用，对井壁产生的扰动微弱。同时，双钻头交替给进互相扶正，可有效防止孔斜，实现精确中靶。双钻头扭矩自平衡钻进系统主要包括近钻头驱动局部扭力闭式自平衡、内外钻头钻压调节和钻具传压隔扭3大部分。依据该系统的功能需求，设计了钻具整体结构系统，并利用有限元分析软件对内钻头传扭轴、调压丝杆和传压隔扭轴承座等关键部件进行强度校核与优化，研制了一套双钻头扭矩自平衡钻进系统功能样机。对整套系统双钻头同步回转、交替给进、系统密封和自动控制等进行一系列测试和调控检测，并开展针对软、中硬和硬3种不同岩性岩石的室内钻进试验，结果表明:该系统对孔壁和岩心的扰动小、中靶率高，在不同岩性地层均具有较高的钻进速度，验证了双钻头在近钻头驱动下扭矩自平衡的可行性，为矿山灾害生命保障救援通道的快速安全构建提供了一种安全高效的方法。 

Theory and experiment of the dual-bit torque self-balancing drilling system for rescue drilling

The rapid and safe construction of rescue channel is an effective method to save the trapped person underground after mine accidents. The conventional rescue hole drilling technologies mainly include the downhole hammer percussion drilling technology and the composite drilling technology, which have the disadvantages of large rig structure, complex drilling process, great disturbance to the formation and low target hit rate. In particular, it is easy to have secondary accidents in the fractured strata, and the rescue requirements could not be effectively met. In order to ensure the formation adaptability and wall stability of rescue boreholes, the dual-bit torque self-balancing drilling method was proposed and the dual-bit reverse drive mathematical model was established. Specifically, the rock was broken by synchronous reverse rotation of the dual bits through the independent driving of the inner and outer drill bits in reverse. The upper drilling tool was mainly subjected to the simple axial tensile pressure, with weak disturbance to the well wall. Meanwhile, the dual bits were fed alternately to support each other, which could effectively prevent the drilling deflection and achieve the precise target hitting. The dual-bit torque self-balancing drilling system mainly consists of three major parts, namely, the local torque closed self-balancing for near-bit drive, the drilling pressure adjustment of inner and outer bits, and the torque isolation for drilling tool transmission. The overall structure of the drilling tool system was designed based on the functional requirements of the drilling system, and the strength of the key components was calibrated and optimized with the finite element analysis software, including the torque transmission shaft of inner bit, the pressure regulating screw rod and the pressure transmission spacer bearing seat. Besides, the functional prototype of torque self-balancing drilling system was developed. In addition, a series of tests, regulation and detection were performed on the synchronous rotation of the dual bits, alternate feed, system sealing and automatic control of the complete system, and on this basis, laboratory indoor drilling tests were carried out for the soft, medium-hard and hard rocks of three different lithologies. The test results show that the system has little disturbance to the borehole wall and core, high target hit rate, and favorable drilling speed in different lithological strata, which verifies the feasibility of the dual-bit torque self-balancing drilling under the near-bit drive, thus providing a new method for the rapid and safe construction of life-supporting and rescue channels for mine disasters.