油气井密封结构的变形与失效行为研究进展

在今后相当长一个时期,石油和天然气依然是人类的主要能源.油气井密封是油气开采中最重要的作业之一,在水平钻井、水力压裂等最新的油气开采技术中发挥着重要的作用,促进了页岩气等非常规油气开采的发展.密封质量会直接影响油气井的安全和生产效率,密封元件的失效可造成严重的环境污染和生命财产损失.因此,深入理解密封元件的失效行为,对于油气井安全评估具有重要意义.水泥和可溶胀高弹体密封是两种最主要的密封方式.水泥密封已有百余年历史,溶胀式高弹体密封则是一种相对较新的密封技术.本文介绍这两种油气井密封结构变形与失效行为的国内外最新研究进展.首先,介绍固井水泥环固化过程中的应力演化、生产作业导致的应力、水泥环的失效模式和失效判据方面的研究进展;然后,介绍溶胀式高弹体封隔器的基本原理、力学理论、测试方法、失效模式及失稳等方面的研究进展. 

A REVIEW ON THE DEFORMATION AND FAILURE OF SEALS IN OILFIELD1)

Oil and gas will still be the major energy resource of human in a long period. Sealing is one of the most important operations in oil and gas exploitation, which plays an essential role in horizontal drilling and hydraulic fracturing, booming the exploitation of unconventional oil and gas like shell gas. The quality of sealing is critical to the performance and safety of wells. The deformation and failure of seals may lead to severe environmental pollution, losses of life and property. Therefore, it is important to study the mechanical behavior of seals in oilfields systematically and deeply for safety assessment as well as better sealing of wells. Cement and swellable elastomers are the most widely used sealing materials in oilfield. Well cementing has been developed for more than 100 years. While swellable elastomeric packer is relatively new. In this review, we present the recent advances in the studies of the deformation and failure of cement sheath and swellable packers. The first part focuses on the cement sheath, including stress evolution during the solidification process and production stage, failure modes, and failure criteria. In the second part, emphasis is placed on the work principle, basic theory, test method, failure modes and instability of swellable packers.