陕北某天然气处理厂回注水处理系统腐蚀影响因素研究

Factors Influencing Corrosion Resistance of Reinjection Water Treatment System in a Gas Processing Plant in Northern Shaanxi

目的考察陕北某天然气处理厂回注系统的腐蚀情况,保证系统安全生产。方法在水质分析的基础上,用现场材质20#钢和计划替换钢材L316研究回注水处理系统的腐蚀现状,随后选择腐蚀最严重环节的水样为介质,采用静态失重法考察温度、pH值、溶解氧、细菌对20#钢材腐蚀速率的影响。结果陕北某气田气井产出水的总矿化度较高(30 000 mg/L左右),其中Ca^(2+)、Mg^(2+)等金属阳离子的含量较高,腐蚀速率随水介质中溶解氧含量的增加均呈上升趋势,在80℃、溶解氧为5.07 mg/L时,腐蚀速率最大,达到0.4001mm/a。随着细菌含量的增大,腐蚀速率上升,腐蚀速率由0.1065 mm/a(TGB 60个/m L,SRB 6个/m L)增加到0.2155 mm/a(TGB 6×10~4个/m L,SRB 6×10~3个/m L)。pH值为5.9时,腐蚀速率为0.3039 mm/a;当pH值为8.5时,腐蚀速率降至0.0710 mm/a。结论通过做好回注水处理系统pH调节、杀菌和隔氧等工作,可以减轻系统的腐蚀。

The work aims to investigate corrosion situation of reinjection water treatment system in gas processing plant in northern Shaanxi, and guarantee safe production of the system. The 20# and L316 steel on the site were used to study the corro- sion situation of the system on the basis of water quality analysis. Water sample in the cycle subject to worst corrosion was se- lected as the medium. Effects of temperature, pH, dissolved oxygen and bacteria on corrosion rate of 20# steel were investigated in static weight-loss method. Total salinity of water produced from a gas field in northern Shaanxi was high （about 30 000 rag/L）, so was content of metal cations including Ca2＋ and Mg2＋. The corrosion rate increased as dissolved oxygen content in- creased, and the corrosion rate was up to 0.4001 mm/a at 80 ℃ provided with 5.07 mg/L DO. The corrosion rate increased from 0.1065 mm/a to 0.2155 mm/a while the TGB increased from 60 cfu/mL to 6 × 104 cfu/mL, and SRB from 6 cfu/mL to 6 ~ 103 cfu/mL as bacteria content and corrosion rate increased. The corrosion rate decreased from 0.3039 mm/a to 0.0710 mm/a as pH value increased from 5.9 to 8.50. Corrosion of the system can be reduced by taking appropriate anticorrosion measurements including pH adjustment, sterilization and oxygen isolation.