水下井口环空压力异常研究分析与技术实践

Research Analysis and Technical Practice of Underwater Wellhead Annular Pressure Anomaly

随着天然气需求量的日益增多及勘探开发工作的不断深入,井下地质条件及井身结构也越来越复杂,固井后环空带压或井口窜气问题也越来越突出。某海上气田采用水下井口进行开采,在生产过程中发现,该气田水下井口A3井的油套环空压力出现异常升高,存在严重安全隐患。针对水下井口修井费用高、难度大等特点,在深入研究水下生产系统流程及工艺原理的基础上,通过流程改造向环空注乙二醇防腐液的方法,成功将A3井油套环空压力由11 MPa降低至3.2 MPa。结果表明:利用水下井口甲醇注入管线向油套环空注乙二醇防腐液降低套压的方法切实可行,每年可节省费用80万元,操作安全易行,为水下井口环空压力异常控制技术的改进和推广提供了有力支持。

With the increasing demand for natural gas and the deepening of exploration and development work,the underground geo-logical conditions and well structure are becoming more and more complicated,and the problems of annular pressure or wellhead gas channeling after cementing are becoming more and more prominent.When an offshore gas field used underwater wellhead for exploi-tation,it was found in the production process that the oil sleeve annulus pressure of the underwater wellhead A3 well in the gas field was abnormally increased,which had serious safety risks.In view of the characteristics like the high cost and difficulty of subsea well-head workover,on the basis of in-depth study of the process and process principle of subsea production system,the process modifica tion and injection of ethylene glycol embalming fluid into the annulus successfully reduced the annular pressure of the oil sleeve in well A3 from 11 MPa to 3.2 MPa.The results show that it is feasible to reduce casing pressure by injecting ethylene glycol emplace-ment fluid into the casing annulus through the subsea wellhead methanol injection pipeline,and it can save 800,000 yuan per year.The operation is safe and easy,and provides a strong support for the improvement and popularization of the control technology of un-derwater wellhead annulus pressure anomaly.