相国寺储气库注采气井的安全风险及对策建议

Safety risk analysis of gas injection and recovery wells in the Xiangguosi Gas Storage and countermeasures

四川盆地相国寺地下储气库是我国西南地区第一个储气库，其安全平稳运行关系到整个西南地区的用气需求和经济发展。国内外地下储气库事故的统计分析结果表明，注采气井的安全风险相对较大。目前相国寺储气库地层运行压力为11．7～28．0MPa，CO2分压为O．53MPa，加之生产前期天然气中还含有钻井液、盐酸、凝析水以及少量H2S等物质，腐蚀环境也较为复杂。为此，根据相国寺注采气井油、套管的材质、固井水泥体系、井下安全阀和封隔器的类型，结合相关文献和实验资料，开展了注采气井的安全风险分析。结果表明：注采气井的油管和套管主要因腐蚀、冲蚀和应力变化的影响导致失效；水泥胶结质量和测井方法的影响将导致固井质量存在缺陷；井下安全阀主要因液压系统和控制线路故障、冲蚀和人为操作不当等原因导致失灵；封隔器主要因应力变化、腐蚀及密封元件变形等原因导致封隔失效。根据存在的这些安全风险，提出了相应的对策措施建议，可为相国寺及类似地下储气库的安全生产和管理提供参考。

The Xiangguosi Gas Storage is the first gas storage in the Sichuan Basin, Southwest China and its safe and steady running relates to gas demand and economic development in this area. Through the statistical analysis of underground gas storage accidents at home and abroad, it is concluded that there is a relatively high risk in the gas injection and recovery wells of the underground gas storage. In the present operation of the Xiangguosi Gas Storage, the formation pressure ranges from 11.7 to 28.0 MPa, the CO2 partial pressure is 0.53 MPa, additionally, at the early stage of production, natural gas contains drilling fluid, hydrochloric acid, con densate water, and a tiny amount of H2 S, which leads to a quite complicated corrosive environment. Therefore, this paper, according to the corrosive environment and engineering parameters of the Xiangguosi Gas Storage and in combination with the relevant documents and experimental data, conducted a safety analysis of the gas injection and recovery wells in the aspects of tubular goods of oil tubings and casings, cementing slurry system, and types of downhole safety valves and packers. The following findings were made. a. The malfunction of oil tubes and casing pipes mainly results from the influence of corrosion, erosion and stress fluctuation. b. The influence of the cement bond quality and the well logging method will lead to the defect in the well cementing quality, c. The failures of the downhole safety valves are mainly due to the faults of the hydraulic pressure system and the control line, as well as e rosion, improper human operation, and so on. d. The containment failure of the packers is caused by the stress fluctuation, corrosion, the distortion of the potted components and other reasons. On this basis, the corresponding countermeasures were finally put forward, providing reference on safety in the production and management for the Xiangguosi and other similar gas storage facilities.