川渝地区泥页岩层段井壁失稳机理及其诱发卡钻原因分析

The Mechanism of Wellbore Instability and Analysis of Its Induced Stuck Pipe Causes in Mud Shale Intervals of Sichuan-Chongqing Region

摘要: 川渝地区上奥陶统五峰组–下志留统龙马溪组泥页岩在钻井过程中，因层理弱面发育与黏土矿物水化膨胀的力学–化学耦合作用，常诱发井壁渐进失稳，进而衍生出坍塌掉块、砂桥、缩径及压差卡钻等复杂事故，严重制约钻井时效与安全。现场实践表明，单纯提高钻井液密度或采用单一防塌措施难以根除失稳的周期性复发。井壁稳定控制技术已从传统的被动提密与堵漏逐步转向力学–化学耦合建模与实时动态调控相结合的主动防控体系。本文围绕失稳的力学机制(层理控制的各向异性剪切滑移)与化学机制(水化膨胀引发的强度劣化)、四类卡钻的诱发条件与形成过程，以及主控因素(内在矿物组成与地应力状态、外在钻井液性能与井眼轨迹)进行系统梳理，并评述当前防塌钻井液体系及耦合模型的应用现状。综合分析认为，力学–化学耦合稳定模型为井壁失稳的量化分析提供理论基础，防塌钻井液体系则为现场防塌措施的具体实施提供工程载体，二者相辅相成，结合实时监测与动态调整，共同构成当前井壁稳定的技术核心；但耦合模型的工程转化、封堵能力的定量评价及超深层失稳预测仍存在瓶颈，未来需向智能化预警、高性能环保型防塌材料及区域针对性评价标准方向突破。

Abstract: During drilling of the Upper Ordovician Wufeng-Lower Silurian Longmaxi shales in the Sichuan-Chongqing area, chemo-mechanical coupling between bedding planes and clay-mineral hydration swelling frequently induces progressive wellbore instability, leading to complex accidents such as borehole collapse, sand bridging, hole shrinkage, and differential-pressure sticking, which seriously compromise drilling efficiency and safety. Field practices indicate that simply increasing mud weight or applying a single anti-sloughing measure cannot fundamentally eliminate recurrent instability. Wellbore stability control has shifted from the traditional passive strategy of mud-weight increase and lost-circulation plugging to an active prevention framework integrating chemo-mechanical coupled modeling with real-time dynamic adjustment. This paper systematically reviews the mechanical mechanism (anisotropic shear slip controlled by bedding planes) and chemical mechanism (strength degradation due to hydration swelling), the triggering conditions and formation processes of the four sticking types, and the dominant controlling factors (internal mineral composition and in-situ stress state; external drilling-fluid properties and wellbore trajectory). The current application status of anti-sloughing drilling-fluid systems and coupled stability models is also assessed. Comprehensive analysis indicates that the chemo-mechanical coupled stability model provides a theoretical basis for quantitative instability analysis, while the anti-sloughing drilling-fluid system serves as an engineering vehicle for implementing field measures; the two are complementary and, together with real-time monitoring and dynamic adjustment, constitute the technical core of current wellbore-stability practice. Nevertheless, bottlenecks remain in engineering translation of coupled models, quantitative evaluation of plugging performance, and ultra-deep instability prediction. Future efforts should target intelligent early warning, high-performance and environmentally friendly anti-sloughing materials, and region-specific evaluation criteria.