微小井眼水力喷射钻进软管的力学行为及控制机制

The development of unconventional oil and gas resources have been importantly listed in the twelfth five-year plan of state. The radial lateral microhole drilling with water jet has been proved an effective technique in conventional and unconventional reservoirs development, and has a broader application potential in shale gas, coalbed methane. Since the mechanical behavior characteristics and control mechanisms of flexible drilling hose including buckling, deformation ,extension capacity and so on have not been known fully due to its small diameter and easy deformation, which become basic problems as to restrict the further applications and development of the technology. This project aim for the technological problems of trajectory , extension ability prediction and controlling of water jet drilling hose during radial microhole drilling, circling on the key scientific issue of mechanical behavior characteristics and control mechanism of flexible water jet drilling hose. Using theoretical analysis, numerical simulation, and experimental combination means, the project proposes to establish mechanics analytic models of water jet drilling flexible hose in a microhole, to calculate and measure traction and recoil forces of self-advanced jet drill bit, to test drilling ability of hydraulic hose under sliding and rotating conditions, and to set up a set of method for predicting and controlling extension capacity of flexible hose to drill microholes with water jet. Above of all, the project intends to establish a set of method for analyzing and controlling the mechanical behaviors and extension capacity of jet drilling hose, and will provide foundations of implementation and parameters optimization of radial lateral drilling.

非常规油气资源开发已列入国家"十二五"重要发展规划，径向水力喷射侧钻微小井眼已被实践证明为一种行之有效的油气井改造和非常规油气增产技术,尤其是在页岩气、煤层气开采中具有更广阔的应用潜力。由于水力喷射软管直径小，易弯曲，对其在微小井眼钻井中的屈曲变形、延伸能力等力学行为特征与控制机制认识不充分，成为制约该技术进一步发展和应用的基础问题。本课题拟围绕水力喷射径向侧钻微小井眼过程中柔性软管的力学行为与控制机制这一科学问题，采用理论分析、数值模拟与实验相结合手段，通过水力钻进柔性软管力学分析模型的建立、自进式射流钻头牵引力与反冲力计算与测试、滑动与旋转条件下水力软管的钻进能力地面试验、软管延伸能力预测与控制等内容的研究，形成一套分析与控制微小井眼水力喷射软管力学行为和延伸能力的方法，为径向侧钻微小井眼技术应用与参数优化提供基础。

近年来，通过径向水平井研究和实践发现现有射流钻头破岩能力不足，且钻孔孔眼不圆整，水平孔眼平直度差导致高压软管摩阻增大，限制了射流钻头的钻进能力。射流钻头自进力不足，使水平井延伸能力受限。由于水力喷射软管直径小，易弯曲，对其在微小井眼钻井中的屈曲变形、延伸能力等力学行为特征与控制机制认识不充分，成为制约该技术进一步发展和应用的基础问题。项目围绕水力喷射微小井眼钻进过程中柔性软管的力学行为与控制机制这一科学问题开展研究。首先，以钢丝编织网软管为研究对象，建立了软管本构分析模型和井筒-转向器-侧钻井眼内柔性软管力学分析模型，可分析内压力、弯曲等条件下软管的强度、变形、应力分布等，形成软管临界屈曲与自锁判别条件、滑动阻力和推进力等力学参数计算方法。其次，设计了反喷自牵引直旋混合射流钻头和多孔射流钻头等，理论分析并实验研究了不同类型反喷射流钻头的自进特性和含高压喷射软管和射流钻头微小井眼内的流场特性，得出喷距、压力、井眼直径等参数对射流钻头自进力的影响规律。再次，通过地面模拟试验，研究滑动和旋转条件下水力软管喷射系统的水力钻进能力，发现旋转条件下钻头的钻井能力高于滑动条件。最后，结合理论分析与地面实验，综合研究了地面额定泵压、岩石强度、井眼稳定性、软管类型、钻进方式等对径向微小井眼延伸能力的影响，得到各因素对径向微小井眼延伸长度的影响规律以及软管达到预定深度的控制方法，可为水力喷射侧钻微小井眼技术工程设计与应用提供依据。项目组与油田企业开展了广泛的交流与技术合作，为企业做技术咨询，解决工程实际中遇到的问题，课题组公开发表的研究成果也为企业现场施工设计与作业提供有力理论支持与技术支撑。