致密气集输管道微生物腐蚀风险及控制措施研究

Study on risk and control measures of microbiologically influenced corrosion of tight gas gathering and transportation pipelines

关键词:  致密气  凝析油  微生物腐蚀  防腐药剂  内腐蚀监测

Key words:  tight gas  condensate oil  microbiologically influenced corrosion  corrosion inhibitor  internal corrosion monitoring

摘要:

目的 针对四川致密气特殊工况,研究并明确集输管道在生产中存在的微生物腐蚀风险,并基于此提出腐蚀控制措施。方法 取现场产出水监测细菌浓度,研究了凝析油比例和温度对含硫酸盐还原菌(SRB)生长及腐蚀程度的影响规律,并系统评价了防腐药剂的应用效果,基于页岩气腐蚀控制经验,推荐了腐蚀监测方法。结果 致密气产出水中存在大量细菌,虽然凝析油对SRB的生长和L245N钢的均匀腐蚀存在抑制作用,但仍有大量细菌附着在试片表面诱发局部腐蚀；排采期高温条件下的点蚀现象更严重。评价得到两类杀菌率高于99%、能有效抑制点蚀的防腐药剂。结论 致密气集输管道存在一定的微生物腐蚀风险,应结合加注高效防腐药剂和加强低洼段监测两方面进行腐蚀防治。 

Abstract:

Objective Aiming at the special conditions in Sichuan tight gas field, the risk of microbiologically influenced corrosion (MIC) of gathering and transportation system during production was studied, and corrosion prevention measures were proposed on the basis of it. Methods The field produced water was used to monitor the concentration of bacteria. The impact of proportion of condensate oil and temperature on the growth of sulfate-reducing bacteria(SRB) and corrosion was investigated. Further, the application effect of corrosion inhibitor was evaluated and based on shale gas corrosion control experience, the detection measures of corrosion was recommended according to experience about shale gas corrosion prevention. Results Bacteria extensively exists in the tight gas produced water. The growth of SRB and general corrosion of L245N steel were inhibited by condensate oil, but a great amount of bacteria were still adhered to the surface of coupons, which induced local corrosion. The pitting corrosion under high temperature of drainage period was more severe. Two types of corrosion inhibitors were evaluated which can inhibit pitting corrosion with sterilization rate above 99%. Conclusion sThere exists some microbial corrosion risk for tight gas gathering and transportation pipelines. It is necessary to combine the corrosion inhibitor injection and internal corrosion monitoring of weak parts of pipelines to prevent corrosion.