超深井钻柱非线性动力学及动态安全性基础理论研究

As the exploration and development of oil and gas in deep formation has become a significant demand for China, the number of the ultra-deep wells is increased rapidly. However, due to the lack of the fundamental research on the drill string dynamics for ultra-deep wells, the study of basic theories for safe and efficient ultra-deep-drilling remains a challenging, which result in poor drilling efficiency and frequent failure of the drill string. This project will firstly investigate the dynamics model of the drilling string for ultra-deep wells and the quick solution method to get the dynamic characteristics, based on a comprehensive consideration of the super slenderness ratio and double nonlinear characteristics. Then comprehensively considering the dynamic stress and the collision effect of the drill string, the dynamic safety evaluation method of the drilling string for ultra-deep wells will be presented and the optimum design method for structure and operation parameters of the drill string will be formed. Secondly, considering the complexity of the loads for ultra-deep wells, the mechanical behavior of the viscous-micro slide-viscous between the thread mating surface of the tool joint under the complicated loads will be studied and the fatigue failure mechanism of the tool joint will be verified. Moreover, the prediction method of the limit work torque for the tool joint will be formed. Thirdly, the complex coupling mechanism between the drilling fluid, cuttings, drilling tools and wellbore in the eccentric annulus of the drill string for extended reach wells will be studied and the removing mechanism for cuttings bed will be investigated. What is more, the installation location of the EHCDP for cuttings bed will be optimized. The project will primarily deal with the critical and basic problems related to efficient and safe ultra-deep well drilling, and provide the scientific guidelines and basis for efficient drilling in deep hydrocarbon formation.

深层油气勘探开发已成为我国油气发展的重大需求，超深井钻井数量快速增加，但相应的超深井钻柱动力学和动态安全性评价等基础理论缺乏，导致钻柱失效、钻井时效差等问题突出。针对上述问题拟开展以下研究：综合考虑超长细比和双重非线性特征，建立超深井钻柱动力学模型，研究超深井钻柱动力学特性快速求解方法；综合考虑钻柱动态应力和碰撞效应，研究超深井钻柱动态安全性评价方法，形成钻柱结构参数和施工参数优化设计方法；充分考虑超深井载荷的复杂性，研究钻具接头螺纹牙啮合面之间存在的粘滞-微滑动-粘滞的力学行为，探明钻具接头疲劳失效机制，形成钻具接头极限工作扭矩的预测方法；研究大位移井钻柱偏心环空井筒内钻井液、岩屑、钻具、井筒的复杂耦合作用机制，探明岩屑床清除机理，优化高效率岩屑床清除钻杆(EHCDP)的安装位置。项目通过上述关键基础问题的研究并取得原创性突破，将为我国深层油气安全高效钻井提供关键理论基础和科学依据。

针对超深井控斜、提速和安全钻井卡脖子难题，项目组开展了大量研究，完成了预定任务，取得了预期成果。研究工作主要包括四个方面:（1）建立了超深井钻柱双重非线性动力学模型、提出了结合直梁和曲梁单元的节点迭代快速求解方法，实现了超8000m钻柱动力学特性分析；研究了PDC钻头扭矩的速度弱化效应模型和考虑轴向振动和粘滑特征的钻头综合激励模型，实现粘滑和涡动特征的统一模拟；测试了超深井钻柱振动特征，分析了钻压、地面转速对钻柱粘滑振动的影响，以及粘滑振动对涡动的影响。（2）研发了超深井钻柱动态安全性仿真平台，实现了钻柱结构参数和施工参数优化；结合加权余量法和有限元方法，提出了一种带井下特殊工具BHA横向振动响应的快速求解方法；研究了超深井预弯曲动力学控斜方法，在川深1、顺北蓬1井与顺北鹰1等8000m以上超深井以及页岩气水平井进行了应用，并解决了塔里木油田巨厚砾石层气体钻井井斜控制难题。（3）研究了钻具接头丝扣力学特性计算精度和计算效率的影响因素，形成快速求解方法；研究了复杂载荷作用下钻具接头材料微损伤演化规律和破坏机制，形成了考虑井眼曲率和轴向拉伸载荷影响的钻具接头极限工作扭矩预测方法和钻具接头力学特性数值仿真平台。同样基于有限元方法，研究了超深井钻柱对套管的碰磨特征，形成了套管磨损可视化表征方法；研究了偏磨油套管本体和接头强度的影响，提出了偏磨套管的破裂强度准则和套管特殊螺纹接头的密封机理。（4）研究了大位移井高效岩屑床清除钻杆工作机制，优化了岩屑床高效清除钻杆的螺旋槽结构特征，形成了高效率岩屑床清除钻具的合理安装位置设计和岩屑床清除效率评价方法。 .通过对以上关键问题开展系统深入的研究，形成了先进的超深井钻柱动力学理论成果，并在中石化超深井、四川页岩气，中石油塔里木油田开展了现场应用，取得了明显的控斜、提速和安全钻井效果。本研究成果可为深层和深海油气资源勘探开发中的安全提速钻井提供理论基础。