高含H2S和CO2环境中L80钢的腐蚀规律

Corrosion of L80 Steel in Environment of High H_2S and CO_2 Content

采用失重腐蚀方法研究了在模拟气田井下腐蚀环境中腐蚀影响因素(总压力、温度、腐蚀时间、H2S、Cl-、溶液流速),对套管钢(L80)腐蚀的影响规律,并用扫描电镜分析了腐蚀产物膜形貌。结果表明:60℃为L80钢在H2S+CO2腐蚀环境中的腐蚀临界温度,此时,L80钢的腐蚀速率最小;当总压力大于等于9 MPa,温度为120℃,H2S、CO2达到各自的超临界点,L80钢的腐蚀速率比温度为90℃时小;随腐蚀时间延长,腐蚀速率明显下降;相对在单一的CO2环境下,引入H2S可降低腐蚀速率;Cl-可促进L80钢的腐蚀;溶液流速加快,腐蚀速率提高。

By simulating corrosion environment in Luojiazhai Gas Field （H2S 10.44 %, CO2 6.79%）, corrosion behavior of L80 casing tube steels was studied by weight-loss method, and corrosion products was analyzed by SEM. The results showed that 60 ℃ was critical temperature for corrosion of L80 steel in high H2S and CO2 content, environment and its corrosion rate is the least at tested temperatures. When the total pressure was less than 9 MPa, corrosion rate at the temperature less than 60 ℃ decreased with increasing temperature, and at above 60 ℃ it increased with increasing temperature. When the total pressure was 9 MPa or above it, gas of H2S and CO2 at 120 ℃ changed into supercritical fluid, and corrosion rate at 120 ℃ was less than that at 90 ℃, and the change of corrosion rate with temperature was the same as that at pressure less than 9 MPa and temperature less than 90 ℃. Corrosion rate was decreased with time lapse. Compared to corrosion rate in CO2, HE S decreased corrosion of L80 steel in H2S＋CO2. Cl^- promoted corrosion of steel. Corrosion rate increased with the acceleration of flow rate.