热水钻快速取芯孔内流场研究

Since the Antarctic subglacial sediment core is one of the most important sample to explore the history and the climate of world, still no country in the world successfully drilled subglacial sediment samples The approaches to Rapid Access Ice Drill (RAID) systems can be subdivided into the three following groups: conventional drilling technology, hot-water drill systems and unconventional drilling systems. Hot-water drilling system reflects the huge potential due to its special medium, polluting the environment etc. However, the research for subglacial sediment coring is in the slow progress. In this project, new design is proposed to combine hot-water drilling system with mechanical coring drill. Hot-water drilling system is used for ice drilling, and mechanical coring drill for subglacial sediment core. It just need to change part drill of hot-water drilling system. Mechanical coring drill includes antitorque unit, chip chamber, PDM, core barrel and drill bit. When hot-water passes through the PDM, PDM will convert hydraulic pressure of hot-water flow into rotation and torque in order to drive the core barrel rotating with the drill bit. Then drill bit begins to cut the bedrock from at the bottom, and bedrock chips will be collected by the hot-water flow into the chip chamber which is installed on the upper side of PDM. Flow field and temperature field down the hole will be analysis combining with theoretical analysis and numerical simulation, then experiments will be done to verify the rules, in order to provide theoretical basis and technical support for hot-water drilling of RAID of our country.

南极大陆冰下沉积物岩芯是探索地球历史与气候的重要样品，但是世界上尚且没有任何一个国家成功钻获冰下沉积物样品。而目前的快速钻探技术发展成大致三类：传统钻探技术，热水钻探技术以及非常规钻探技术。其中热水钻由于其特殊的介质，不污染环境等特点，体现出了巨大的潜力。但是对于冰下沉积物岩芯的研究进展缓慢。本项目提出采用热水钻进系统与机械取芯钻具配套使用，在冰层利用热水钻进技术快速钻进，钻达沉积物层时，仅更换所设计的机械取芯钻具即可完成取芯。机械取芯钻具包含反扭装置、岩屑管、螺杆马达、岩芯管以及钻头等部分。当热水流经螺杆马达时，其将热水流的液体压力转化为螺杆旋转的扭矩，从而驱动岩芯管及钻头一起旋转。热水流体的流速将所产生的岩屑携带并收集到设置在螺杆马达上方的岩屑室中。结合理论分析与数值模拟分析流速对孔内流场及温度场的影响，并通过试验对规律进行验证，从而为我国热水钻快速钻进取芯技术提供理论基础和技术支撑。

热水钻探技术由于其特殊介质，不污染环境，钻进速度快等特点，在各种极地钻探技术中尤为突出，但其缺点是不能通过该技术直接获取冰芯，岩芯。本项目主要基于极地钻探快速取芯的需要，开展新型钻具的设计、理论，数值模拟以及试验研究，用于配套热水钻探系统使用。该技术省去了额外的配套设备，直接利用螺杆马达+底部钻具替换底部喷嘴就可以通过热水流量直接驱动钻具旋转钻进，且可根据地层的种类，更换钻头的类型，获取冰芯/岩心。本项目通过对热水从地表到孔底的温差，压力损失等进行了计算，完成了螺杆马达的选型；对比了单壁钻杆与双壁钻杆孔内流场分布规律，得出后者能提供更高的压力，对双壁钻杆孔内流场分析得出出水口流量应控制在90L/min以内才不至于影响冰芯的质量，对双壁钻杆孔内温度场分析得出在流量15L/min条件下即可满足孔内温度基本不变的要求，孔内的温度场将基本维持在进水口的温度10℃，只考虑流速的因素即可。对该套钻具进行了实验室的试验，在不同流量，不同温度条件下进行了钻进试验，钻进速度随着温度的升高、流量的增大而增大，最大钻进速度可达7.02m/h，同时所得冰芯长度与钻进速度的比值也在80%以上，冰芯直径与钻头内径的比值也在80%以上，证明了其满足配合热水钻进系统的要求，同时能完成取芯工作，并提出了相应的钻进参数作为参考。