高温高压气井连续管在CO2环境中的电化学腐蚀数值模拟

Numerical Simulation of CO2 Electrochemical Corrosion of Coiled Tubing in High-Temperature and High-Pressure Gas Wells

针对高温高压气井中连续管在含CO2地层极易腐蚀、开裂等问题,调研了腐蚀失效情况,分析其腐蚀失效机理。应用COMSOL多物理场耦合分析方法,建立连续管在CO2环境中的电化学腐蚀数值模型,分析环境因素对腐蚀速率的影响规律。结果表明:实验腐蚀速率和数值模拟腐蚀速率的最小误差为1.3%;CO2分压分别为0.1、0.5和1.0 MPa时,连续管腐蚀速率达到峰值时的温度分别为120、90和60℃;当CO2分压为0.1 MPa、电解质溶液电导率为2.86、pH值较小时,连续管的腐蚀速率最大。该研究为CO2腐蚀环境下连续管的安全使用提供了建议。

In view of the problems of local corrosion,uniform corrosion and pipe body cracking of coiled tubing(CT)in formation containing CO2 and high-temperature and high-pressure gas well,the CT corrosion failure was investigated firstly,and the corrosion failure mechanism was analyzed.The numerical model of CO2 electrochemical corrosion of CT was established by COMSOL multifield coupling analysis method,and the influence of environmental factors on the corrosion rate was researched.The experimental result was compared with the numerical result.The result shows that the minimum error between the experimental corrosion rate and that of the numerical simulation is 1.3%.When the partial pressure of CO2 is 0.1,0.5 and 1.0 MPa,the corrosion rate of CT reached its peak at 120,90 and 60℃,respectively.When the partial pressure of CO2 is 0.1 MPa,and the electrolyte solution conductivity is 2.86,the corrosion rate of CT is higher at smaller pH value.This study is expected to provide suggestions for the safe use of CT in CO2 corrosion environment.