The corrosion rate prediction models about CO2 corrosion and CO2/H2S coexistence system were summarized, and the modeling ideas, factors considered, limitations of various models were expounded. CO2 corrosion prediction models were improved constantly. Flow state, corrosion product film, material and other complex factors were gradually contained in the calculation models. Some relatively mature theoretical achievements were obtained based on the semiempirical models, empirical models and mechanism models. However, less factors were contained in prediction models of CO2/H2S coexistence system at present, and the modeling methods were mainly established by empirical or semiempirical methods. On the one hand, the prediction models were not combined tightly with production on site. On the other hand, corrosion mechanism needed to be applied further to the study of prediction models.

川渝某页岩气平台集气管线投产后短时间内发生穿孔失效,为找出集气管线腐蚀失效的原因,分析了失效管段所处的腐蚀环境,结合材料理化性能和腐蚀产物形貌成分测试结果,认为输送介质中的CO2和返排液中高含量的硫酸盐还原菌(SRB)是造成管道腐蚀穿孔的重要原因,两者同时参与了腐蚀反应,形成主要由代表性腐蚀产物FeCO3、FeS构成的产物层.在CO2和SRB代谢的共同作用下,集气管线快速腐蚀穿孔.

在页岩气开采过程中,页岩气田的油管及集输系统普遍存在细菌腐蚀问题.针对该问题,对细菌来源进行了溯源分析,提出了控制细菌措施,并进行了现场试验.推荐的杀菌剂CT10-4,杀菌效果良好,且兼具清洗作用.加注杀菌剂后,返排液明显变清澈,杀菌现场试验停止加药后,持续有效期达28天.

油田火驱尾气中存在CO2、H2S和O2 3种腐蚀性气体,且O2分压会在一定范围内变化.目前,鲜有关于O2分压对注气管常用钢316L钢腐蚀行为影响的报道.以316L钢为试材,利用高温高压模拟试验、失重法和扫描电镜等分析技术,研究在O2-H2S-CO2条件下O2分压对316L钢腐蚀行为的影响规律并分析其机理.结果 表明:O2-H2S-CO2条件下,316L钢的腐蚀速率和产物膜厚度随O2分压的升高呈先减小再增大的变化规律;钝化膜均由极细的颗粒构成,有Cr和Ni的化合物沉积,有利于提高316L钢的抗腐蚀能力;一定范围内,O2分压升高会促进316L钢发生钝化,提高钝化膜的稳定性;但随O2分压的继续升高,会促进O2与H2S生成S8,更多的S8局部沉积,与H2O反应引起局部酸化,导致钝化膜出现破损点,并形成腐蚀电偶,发生严重的点蚀.

针对输气管道中90°弯头冲蚀磨损失效的问题,依据现场实际工况,利用CFD仿真软件建立相应的模型,探究集输管道输送气固两相流介质时固体颗粒冲击弯头壁面的冲蚀磨损规律.采用RNG k-ε湍流模型、DPM模型和E/CRC冲蚀磨损模型研究集输压力、 不同重力方向、 集输流速、 集输管径以及颗粒大小对弯头冲蚀磨损的影响.结果表明:集输压力越大,弯头冲蚀磨损程度减轻,且磨损区域呈现由中部向出口、 由外侧向内侧凹曲面移动的现象;重力会影响弯头冲蚀磨损程度以及磨损区域,重力场和气相主流场趋势相同时会加剧磨损;当气流速度超过临界集输流速时,冲蚀磨损情况加剧且最大磨损率出现区域后移;集输管径越小、 颗粒直径越大时,冲蚀磨损越严重.

新疆油田的火驱尾气中含有O2、H2S和CO2三种腐蚀性气体.以35CrMo钢为实验材料,基于新疆油田火驱尾气的现场工况,设计正交实验条件;采用失重法测试35CrMo钢的腐蚀速率;结合SEM等手段对典型工况的腐蚀产物进行测试分析.结果 表明:35CrMo钢在实验条件下发生均匀腐蚀,气质组成对腐蚀速率的影响最大,其次是温度和总压;产物形态以粒状为主,在含氧条件下有片状产物,较高温度和含氧条件下产物膜厚度较大,产物中有Fe、C、O、S四种元素,并含有Cr元素,既有Fe的硫化物,也有Fe和Cr的氧化物;O2除了参与吸氧反应,还会氧化Fe2+等,也会与H2S发生交互作用生成单质S,与CO2交互作用抑制FeCO3生成.该研究结果为金属材料在O2、H2S和CO2混合体系中的腐蚀机理和防护研究提供了理论基础.

In order to study the optimum protective criteria to inhibit pipeline corrosion under alternating current (AC) interference,experiments were established to determine the protective potential under optimum protection conditions in this paper.Firstly,both the criteria of classic-0.85 V (vs CSE) cathodic protective potential and negative offset 100 mV cathodic protective potential were verified under AC interference.Then,the influence of the cathodic protective potential on protection effect was studied to determine the protective potential range under preferable effect.Based on this,combined with the overall analysis on the two evaluation indicators of protective degree and protective efficiency,the cathodic protective potential was obtained under the optimum protective conditions.Results showed that,when AC interference existed,the criteria of classic-0.85 V (vs CSE) cathodic protective potential and negative offset 100 mV cathodic protective potential both failed;within -1.20 V(vs CSE),the protective potential increased negatively and consequently the effect of corrosion inhibition would be enhanced under AC interference.Comprehensively considered the three factors of corrosion rate,protective degree and protective efficiency,the protective potential of-1.00 V(vs CSE) was suggested to adopt when the alternating current density was within 50 A/m2;whereas the protective potential of-1.10 V(vs CSE) was suggested to adopt when the alternating current density was above 50 A/m2.