钻井完井高温高压H_2S/CO_2共存条件下套管、油管腐蚀研究

STUDY ON CORROSION BEHAVIOR ON CASING AND TUBING DURING DRILLING AND COMPLETION OPERATIONS IN HTHP H2S/CO2 ENVIRONMENT

在油气开发中,伴生气中多含有一定量的H2S与CO2,对油管、套管的腐蚀给油气开发造成了巨大损失,极大地制约了CO2和H2S共存条件下的油气开发。因此,开展高温高压CO2/H2S共存条件下油管、套管钢材腐蚀的研究具有重要意义。为此,以实验手段模拟油气开发中高温高压H2S/CO2共存环境,用失重法、SEM和EDS研究了油管、套管L80钢材的腐蚀规律以及腐蚀产物膜。结果表明,在实验条件下,随着温度的升高,腐蚀速率呈先增加后下降的趋势,且温度越高,压力对腐蚀速率的影响越大;在腐蚀反应初期,腐蚀速率很高,但随着腐蚀时间的延长,腐蚀速率明显下降;腐蚀开始时腐蚀产物膜以FeS为主,随时间延长转为稳定的FeCO3。同时还发现显微组织、硬度以及组成成分对腐蚀产物膜的形成及抗腐蚀性能有较大的影响。

There often exists H2S and CO2 in associated gas,during oil/gas exploitation it will result in great damage and limit the oil and gas development due to the corrosion occurred on tubing and casing.Therefore to study the corrosion behavior occurred on tubing and casing in HTHP CO2/H2S environment is significant.This paper introduces that the HTHP CO2/H2S conditions were experimentally simulated,the corrosion behaviors and the produced corrosion films on L80 steel of tubing or casing were investigated by weight loss method,SEM and EDS methods.The results indicate the corrosion rate will increase first and then decrease when the temperature increased;the higher the temperature,the more effects the pressure will have on corrosion rate;at the early corrosion stage,the corrosion rate is very high,with the time on the rate will drop obviously;at the early stage,the produced corrosion film is predominated by FeS,while with the corrosion time extended the film is mostly FeCO3;and it is found that the microstructure,hardness and composition of the steel is largely related with the formation of the corrosion film and the corrosion resistance of the tubing and casing.