气液环境下注氮气井管道腐蚀因素和机理研究

塔河油田注氮气后油井井口及井下管道取样观察有冲刷及点蚀现象,地面单井管道也出现注气后腐蚀穿孔情况。为了研究注氮气井管道腐蚀影响因素及机理,在对注氮气工艺、介质及生产工况分析的基础上,对氧分压及含量、流型流态及酸性气体分压比参数计算分析,研究了氧、氯离子、流型流态、酸性气体因素对管道腐蚀的影响,结合腐蚀产物XRD衍射特征及腐蚀形貌VRD镜像特征分析,研究表明注氮气井不同生产过程不同部位的管道腐蚀机理存在明显差异性。在注气过程中,井口及井下管道腐蚀主要受氧和流态的影响;在注气后的生产过程中,地面单井管道腐蚀主要受氧和酸性气体的影响。氯离子是点蚀发生的催化剂;其中前者的腐蚀机理为相互促进的氧的电化学腐蚀与冲刷腐蚀,后者的腐蚀机理为氧的电化学腐蚀为主,并促进了酸性气体的电化学腐蚀进程。两者腐蚀机理差异性受溶解氧扩散过程控制。

Study on nitrogen gas pipeline and mechanism of corrosion factors on gas-liquid environment

Tahe oilfield after nitrogen injection wellhead and underground pipeline sampling observation of scour and pitting corrosion phenomenon, the ground also appear single well pipeline corrosion perforation after gas injection, in order to factors influencing the corrosion of gas pipeline and the mechanism of nitrogen injection, on the basis of nitrogen injection technology, media and production condition analysis, the partial pressure of oxygen and content, flow pattern and acidic gas partial pressure ratio parameter calculation and analysis, influence of oxygen, chlorine ion, flow pattern, acidic gas factors on pipeline corrosion, corrosion product analysis XRD diffraction characteristics and corrosion morphology of VRD image characteristics, research shows that the corrosion of pipes in different parts of the mechanism of the process of nitrogen injection wells in different production has obvious difference character: in the process of gas injection, wellhead and underground pipeline corrosion is mainly affected by the oxygen and flow; in the production process of gas injection after the influence of corrosion surface, single well pipeline is mainly affected by oxygen and acid gas, chlorine ion is the catalyst of pitting occurring. The corrosion mechanism of the former is mutual promotion of oxygen electrochemical corrosion and erosion corrosion, corrosion mechanism of the latter to electrochemical corrosion of oxygen, and promote the electrochemical corrosion process of acid gases. The corrosion mechanism of differences are affected by dissolved oxygen diffusion process control.