长2储层开发过程中管道腐蚀机理及原因分析

Mechanism and Cause Analysis of Pipeline Corrosion in Chang 2 Reservoir Development

石油开发过程中管道腐蚀问题关系生产,十分重要。本文对长2储层的采出水和管道的腐蚀产物进行了分析。实验结果表明,14组水样的腐蚀速率均超过了0.076mm/a的标准,其中硫酸盐还原菌(SRB)为优势菌种,含量主要集中在2~102个/ml之间,会腐蚀管道;水样pH呈酸性且在5.3~6.3之间,Cl-含量普遍较高,含量在2668~22608mg/L之间,会引起点蚀;腐蚀产物以FeCO_(3)、FeS为主,伴生气中含有CO_(2),无H2S,说明CO_(2)和硫化物是腐蚀的主要原因,除此之外,腐蚀产物中还含有少量针铁矿(FeO(OH)),说明存在溶解O2引起的腐蚀,少量方解石(CaCO3)、文石(CaCO_(3)),说明存在垢下腐蚀。因此,在后期管道的防腐中应重点注意CO_(2)、硫化物和SRB引起的腐蚀,同时应注意含O_(2)、结垢和采出水高含Cl-的问题,做好杀菌、除氧、脱硫和防垢等措施,以保证油田的开采工作。

The problem of pipeline corrosion in the process of oil development is related to production and is very important. In this paper, the produced water and corrosion products of pipelines in Chang 2 reservoir were analyzed. The experimental results showed that the corrosion rate of 14 groups of water samples exceeded the standard of 0.076 mm/a, among which sulfate-reducing bacteria(SRB) was the dominant species, and the content was mainly concentrated between 2~10~2/ml, which would corrode the pipeline. The pH of the water sample is acidic and between 5.3~6.3, and the Cl-content is generally high, with a content between 2668~22608 mg/L, which will cause pitting corrosion;Corrosion products are mainly FeCO3,FeS, associated gas contains CO2, no H2S, indicating that CO2and sulfide are the main causes of corrosion, in addition, corrosion products also contain a small amount of goethite(FeO(OH)), indicating the presence of corrosion caused by dissolved O2, a small amount of calcite(CaCO3), aragonite(CaCO3), indicating the presence of corrosion under scale. Therefore, in the anti-corrosion of pipelines in the later stage, we should pay attention to the corrosion caused by CO2, sulfide and SRB, and at the same time, we should pay attention to the problems of O2, scaling and high Cl-content of the produced water, and do a good job in sterilization, deaeration, desulfurization and anti-scaling measures to ensure the exploitation of the oilfield.