坍塌压力与井身结构设计和井壁稳定技术关系初探

遇水后强度急剧下降，打开井眼后力学失稳而崩散是硬脆性页岩坍塌的主要原因，解决的有效途径是采取合理的井身结构和合理的钻井液密度，以平衡地层压力。从化学上应采用封堵剂，如磺化沥青、超压细碳酸钙等封堵微裂缝，采用造壁性强的处理剂改善滤饼质量，粘糊微裂缝，降低失水量，防止水分的侵入。井身结构设计的基础是地层压力体系，在地层压力体系中受外界影响较大的是地层的坍塌压力，有效的控制地层的坍塌压力是对井身结构优化和保持井壁稳定的主要因素之一，其关键是控制钻井液安全密度窗口。

RELATION OF CAVING PRESSURE WITH CASING PROGRAM AND HOLE STABILITY TECHNIQUE

The main causes of hard brittle shale caving are strength degradation after water and mechanics destabilizing effect after drilling. The effective methods of solving the problem are that adopting rational casing program and drilling fluid window balance formation pressure, adopting blocking agent, such as sulfonated asphalt, overpressured fine calcium carbonate plug microfracture, using treating agent with strong walm-cake-building characteristics improve cake quality to reduce fluid loss and prevent water invasion. The base of casing program design is formation pressure system. The influence of caving pressure on formation pressure system is very great. Effectively controlling caving pressure is one of the important factors for optimizing casing program and keeping well stability. Its key is controlling drilling fluid density.