提高复杂油气井固井质量技术研究——保证水泥环长期密封性的技术措施

Improve Cementing Quality of Complicated Oil and Gas Wells-Ensure Long-Term Sealing Performance of Cement Sheath

随着勘探开发的持续深入发展,面临的井下地质条件越来越恶化,井身结构变得十分复杂,固井后水泥环密封失效问题越来越突出。从水泥环自身特性及外界条件导致水泥环密封失效的原因等方面,对复杂深井超深井固井、复杂天然气井固井、酸性气藏固井、页岩气及致密油气固井、储气库固井、海外复杂区块固井、海洋低温深水固井水泥环密封性面临的挑战进行了分析,提出了目前保证水泥环长期密封性的技术措施:提高顶替效率;切实做到"三压稳",采用平衡压力固井;设计满足封固要求的水泥浆体系;水泥石力学性能应能承受井下温度、压力、应力的变化。在此基础之上,提出了下一步需要开展的研究工作。

With the efforts for exploration and development continually strengthened, the downhole geological conditions become more and more difficult while the wellbore structure is also complicated. As a result, the failure of cement sheath after cementing job becomes a critical problem. This article focuses on the failure of cement sheath caused by the inner characteristics of cement sheath or external conditions. It also makes analysis of cement sheath sealing challenged by cementing of complicated deep wells and super-deep wells, cementing of complicated natural gas wells, cementing of complicated acidic gas wells, cementing of shale gas wells and tight oil and gas wells, cementing of gas storage depot, cementing of complicated wells on overseas blocks, and cementing of offshore low-temperature deepwater wells. The current technological measures for assurance of long-term cement sheath sealing are proposed to improve the replacement efficiency. Balanced pressure is adopted to cement the well while the slurry system is designed to meet the requirements for sealing and cementing. The mechanical functions of cement slurry should be able to meet the changes in downhole temperature, pressure and stress. The next stage of research work is also planned on the basis of the above-mentioned efforts.