超深地层是我国油气勘探开发的重要领域,但因超深地层复杂地质环境导致的井壁失稳已经成为制约超深地层油气资源动用的重大技术难题之一.为此,从地质和工程2个方面系统总结分析了超深地层井壁失稳机理,进而分析了超深地层岩石物理力学实验及本构方程、地应力测量与地层压力预测等地质力学参数评价技术,并探讨了超深地层井壁稳定性评价理论与控制技术的研究进展,最后提出了促进超深地层钻井理论技术发展的建议.研究结果表明:①加强还原超深地层环境的岩石物性、力学和物理模拟实验研究,耐高温高压地应力和井筒压力测量仪器研发,是认识超深地层极端环境下岩石与地质力学特性的关键;②高温高压条件下的多场耦合岩石力学理论是构建超深地层井壁稳定性评价技术体系的基础;③攻关融合超深地层钻井的大尺寸多开井身结构设计、抗高温高压钻井液体系、防漏堵漏工艺与材料、精细控压钻井理论与工具等井壁稳定控制技术是实现超深井钻井提质增效的前提.结论认为,超深地层井壁失稳理论与控制技术的发展不仅推动了我国油气钻探朝着超深地层进军,还有力推动了深地工程科学考察、超深层油气勘探开发理论与装备的迭代与升级.
Ultra-deep strata is an important field of oil and gas exploration and development in China.Wellbore instability caused by complex geological environment is one of the huge challenges restricting the exploitation of oil and gas resources in such strata.In this paper,the mechanism of wellbore instability in ultra-deep strata is analyzed from the geological and engineering perspectives.Then,the petrophysical-mechanical experiments and the geomechanical parameter evaluation technologies such as constitutive equation,in-situ stress measurement and formation pressure prediction for ultra-deep strata are investigated,and the wellbore stability evaluation theory and control technology for ultra-deep strata are discussed.Finally,some suggestions are put forward to promote the drilling theory and technology for ultra-deep strata.The results are obtained in three aspects.First,the petrophysical,mechanical and physical simulation experimental studies on the environment of ultra-deep strata and the research and development of in-situ stress and wellbore pressure measurement instruments for high-temperature and high-pressure conditions are crucial to understanding the rock and geomechanical properties of ultra-deep strata in extreme environment.Second,the multi-field coupled rock mechanics theory under high temperature and high pressure is the basis for establishing a technical system of wellbore stability evaluation on ultra-deep strata.Third,the integration of wellbore instability control technologies such as multi-section casing program design for large-sized boreholes,HTHP drilling fluid system,leakage prevention and plugging techniques and materials,and theory and tool for precisely managed pressure drilling is a prerequisite for safe and efficient drilling of ultra-deep wells.In conclusion,the development of the evaluation theory and control technology of wellbore instability in ultra-deep strata promotes the drilling of ultra-deep wells in China,and also drives the update and upgrade of theory and equipment for deep engineering survey and ultra-deep oil and gas exploration and development.