二氧化碳地质存储过程中注入井完整性分析

Well integrity analysis of injection wells during CO2 sequestration

柏明星 谯志

BAI Mingxing QIAO Zhi

东北石油大学石油工程学院，黑龙江大庆　163318 Clausthal University of Technology, Clausthal-Zellerfeld, Germany　38678

Department of Petroleum Engineering, Northeast Petroleum University,Daqing 163318, China Institute of Petroleum Engineering,Clausthal University of Technology Clausthal-Zellerfeld 38678, Germany

二氧化碳沿井筒渗漏是二氧化碳地质埋存过程中所面临的重要风险之一，因此在注入二氧化碳前须对套管、水泥环及岩石组合体进行完整性评价。利用数值模拟的方法对二氧化碳注入井注气过程中温降及盐岩蠕变对井筒完整性的影响进行了分析，并得出井筒温降的极限值。模拟方法包括 3个主要步骤：钻井过程的模拟、盐岩蠕变的模拟及注气过程中温降的模拟。研究对象为套管及水泥环在温降条件下应力场的分布及位移的变化。结果显示，在一定条件下套管与水泥环之间的微环隙可以通过盐岩蠕变的方式进行弥补甚至愈合，同时应该选择适合二氧化碳注入过程中的低温环境的材料。该方法即将应用于德国某大型二氧化碳存储及提高天然气采收率项目中。

CO2 leakage along wellbore is one big risk during the process of CO2 sequestration, and therefore it is necessary to evalu-ate the well integrity prior to the injection of CO2. A numerical model is used to analyze the impact of temperature decrease and salt rock creep on injection well integrity in this process of CO2 injection and obtain a critical temperature drop value. The method consists of three main steps: simulation of drilling process, simulation of salt creep and simulation of temperature decrease. The outcome includes the variation of stress and displacement across the casing and cement sheath. The results show that under some circumstances the micro-annulus between casing and cement sheath can be compensated by salt creep or even self-healed. Besides, appropriate materials should be selected to suit the low temperature during the injection process.This method is going to be applied in one large-scale CO2 sequestra-tion and enhanced gas recovery project in Germany.