大斜度井段带螺旋槽井壁环空岩屑运移机理研究

Hole cleaning is one of key technologies in complex construction well drilling such as extended well drilling, the core of which is cuttings transport research. The Study on cuttings transport laws in helical flow are still not perfect. The existing studies are mainly focus on the effect of drilling pipe rotation and cuttings bed removal tools on cuttings transport, the spiral flow in annular is derived from inner face. In this study cuttings transport in annular with helical grooves borehole during drill highly-deviated well section will be researched. Its spiral flow in annular is derived from outer face or inner and outer face. The cuttings transport efficiency in annular of helical grooves borehole will be researched using methods of theoretical analysis, numerical simulation and physical experiment combined. Firstly A numerical model of cuttings transport will be established and the numerical experiment of cuttings transport in regular borehole and helical grooves borehole will be carried out. Secondly the effect of parameters of helical grooves on cuttings transport and the cuttings transport and laws in helical flow will be revealed deeply by analysis of mud and cuttings tangential velocity field and their coupling condition and cuttings Radial concentration field. Then a theoretical model of diffusion equation of cuttings and calculation of the effect of helical grooves parameters and drilling parameters on cuttings transport efficiency and pressure loss will be deduced and used to identified the optimal helical grooves parameters in the drilling operation range. At last physical experiments will be carried out to test and revise the above achievements. This study will provide theoretical support for the engineering application of helical grooves borehole drilling and design of other cuttings bed removal tools.

井眼清洁技术核心是环空岩屑运移机理研究，关于岩屑在环空螺旋流中运移机理的研究还不够完善。现有学者多是研究岩屑在钻杆旋转或岩屑床清除短节这种从“内”驱动的环空螺旋流中的运移机理。本研究拟改变思路，研究大斜度井段带螺旋槽井壁环空岩屑运移机理，其属于从“外”或“内外”结合驱动的环空复杂螺旋流。拟运用理论分析、数值模拟和物理实验相结合的方法开展研究。研究内容和预期成果包括：建立环空岩屑运移数值模型，开展带螺旋槽井壁环空岩屑运移数值模拟实验；分析不同螺旋流场中泥浆/岩屑切向速度场及其耦合分布、岩屑径向浓度分布等，揭示岩屑在环空复杂螺旋流中的扩散和运移机理；建立不同工况下岩屑径向扩散方程、环空泥浆携岩效率和压力损耗与螺旋槽参数的关联模型，分析螺旋槽参数对环空携岩效率的影响规律；开展物理实验验证以上研究成果。本研究将丰富环空螺旋流岩屑运移理论，为带螺旋槽井壁钻井工程应用及设计其它携岩工具提供理论依据。

研究和实践表明复杂结构井井眼不清洁时，环空会存在过高的岩屑浓度，从而产生一系列复杂情况。钻柱旋转会在环空形成螺旋流动，有助于岩屑运移，但在连续管钻井或井眼尺寸较大时无法使用。本研究提出利用螺旋井眼提高环空岩屑运移效率的新思路，并开展了螺旋井眼岩屑运移理论和实验研究。主要研究内容和取得成果如下：①通过大量试算并与实验数据进行对比，建立了岩屑运移最优数值模型和求解参数组合，提高了岩屑运移数值模拟的准确性，为后续岩屑运移研究提供了一种有效方法；②开展了常规井眼岩屑运移数值模拟实验，获得有效实验数据360组；开展了不同类型螺旋井眼单相流体数值模拟实验、岩屑运移数值模拟实验，获得有效实验数据356组；开展了常规井眼岩屑运移物理实验共计185次，获得有效实验数据120组，为后续岩屑运移研究积累了大量数据；③分析了钻杆旋转对岩屑径向扩散的影响规律，建立了常规井眼岩屑浓度计算模型、钻杆旋转对岩屑径向扩散系数的修正模型，能有效地提高现有大量不考虑钻杆旋转的岩屑运移模型的计算精度和应用范围；④分析了不同螺旋参数下，螺旋井眼环空单相流动规律、岩屑运移规律，建立了螺旋井眼单相流动环空压耗计算模型、岩屑浓度计算模型和环空压耗计算模型，为螺旋井眼的设计提供了理论依据；⑤发表学术论文3篇，其中SCI/EI收录2篇，申请专利4项，其中已授权3项；依据研究成果开发了复杂结构井水力学分析优化软件、井眼清洁监测软件等，能有效提高钻井设计效率、降低钻井风险、节约钻井成本，为企业和石油行业带来了巨大的经济效益和社会效益，获中国石油和化工自动化应用协会科学技术奖三等奖1项（排名第1）。