Research On Under-deposit Corrosion Behavior And Protective Measures Of Zhongyuan Oilfield Three-phase Separators

With the Zhongyuan Oilfield entering high water cut production period，resulting in thethree-phase separators appear different levels of under-deposit corrosion，the body ofseparators tend to corrosion perforation，reducing the service life of separators greatly，evenlead to major safety accidents. Currently，the reasons of the under-deposit corrosion ofseparators are not yet clear，and relevant research is not systematic and comprehensive. Inorder to provide theoretical foundation for monitoring and controlling the under-depositcorrosion of separators，so the research on under-deposit corrosion behavior and protectivemeasures of separators has important academic value and engineering applicationsignificance.In this paper，the under-deposit corrosion mechanism of separators and protectivemeasures were obtained by field investigating the scaling parts of separators，scale sampleswere analyzed by XRD and SEM analysis，under-deposit corrosion factors and traits testingin laboratory，corrosion and scale inhibitors preferably evaluation testing and sacrificialanode materials preferably evaluation testing. The main contents and conclusions are asfollows:(1) It was found that separators scaling parts and under-deposit corrosion mainly in thestraight pipes， parts of pipe diameter changes， parts of pipes bend of the internalcomponents，the middle and lower part of the body through field survey of the51separatorswhich are being used in the Zhongyuan Oilfield. XRD analysis shows：scale samples ofseparators are mainly composed of CaCO3，SiO2，and a small amount of CaSO4，BaSO4，SrSO4，corrosion products are mainly composed of Fe2O3，FeCO3，FeS and so on.(2) It was identified that CO2electrochemical corrosion，Cl－leads to pitting corrosionand SRB bacteria corrosion are the main reasons of under-deposit corrosion of separators.Theinfluence traits of the temperature，the CO2partial pressure，the content of Cl－，the flow rate，SRB on the under-deposit corrosion rate were researched by simulating the separatorsworking environment via the high temperature and high pressure reator. Orthogonalexperiment results showed that，the order of the five factors that affect the under-depositcorrosion rate was like this： the content of SRB＞the CO2partial pressure＞theconcentration of Cl－＞the working medium temperature＞the working medium flow rate.(3) The two ZY-7，ZY-10were preferred from12kinds of corrosion and scale inhibitorsby atmospheric static primary election testing，high temperature and high pressure dynamic evaluation testing，simulating separator working conditions dynamic evaluation testing，theircorrosion and scale inhibition rates were over80%when dosed concentration of200mg/L，which can be applied to the Zhongyuan Oilfield separators under-deposit corrosion siteprotection；the Al-Zn-In three elements of aluminum alloy as a sacrificial anode protectionmaterial was preferred through the sacrificial anode material preferably evaluation testing，field application tests showed that the average level of protection reached94.76%，the fieldtest results better. The proposals of separators under-deposit corrosion protective measuresare proposed on the basis.