The Carbon Dioxide Corrosion Behavior And Evaluation Of Corrosion Inhibitor Of Gathering Pipe Used For Oil And Gas Fields

With the development of the oil industry rapidly, more and more CO2corrosions exist inoil fields so that more and more people study these issues. In order to reduce the occurrenceof CO2corrosion, researchers also tried a variety of methods. The most common, effective,easiest and cheapest way is to add inhibitor to suppress the corrosion. The performance ofInhibitor, toxicity, stability and appropriate concentration are the keys to solve the problem.So how to evaluate Inhibitors performance is particularly important.（1）In this paper, weight loss method in high temperature and pressure autoclave isused to test the corrosion rate of20#steel. Through the addition ratio of the inhibitor’sconcentration, the efficiency of different inhibitors can be measured to find out the optimalconcentration of inhibitor. Then to use an electrochemical method verify the effectiveness ofinhibitors.The performance of five inhibitors（JMH、MZLH、JAYH、SZH and LSZH）are addedin simulation of an oilfield water to evaluate20#steel by weight loss and electrochemicalmethod. The best effective inhibitor is JAYH, the concentration of inhibitor is150mg/L andthe efficiency of inhibitor reaches90.87%.（2）Weight loss method is used to test the corrosion rate of L415steel in the gas phaseand liquid phase. And then to observe the corrosion morphology with optical microscope（OM）and scanning electron microscopy (SEM). After finding out the corrosion rules bycomparing the gas and liquid phases and adding targeted Inhibitors, the effects of inhibitorsin the gas-liquid two phases can be tested and the performance of Inhibitors can be evaluated.The environment of oil and gas fields contains CO2.We obtain it in the corrosionbehavior of L415steel. Gas phase corrosion is more serious compared with liquid phasecorrosion. The performance of No.1inhibitor is better than No.2inhibitor.（3）Under high temperature and pressure, we obtain CO2corrosion product films of20#tubing steel by weight loss method. The corrosion product films are soaked in oil to test itsdissolution. By observing morphology of corrosion product films soaked at different times bySEM and obtaining in element content changes by EDS analysis, conclusions can be drawn.Under the conditions of high temperature and pressure,20#steel is etching in the etchingsolution.Corrosion product film soaked in oil temperature is60℃by reducing the measurement quality,scanning electron microscopy (SEM) to observe the surfacemorphology of corrosion product films and using EDS (EDS) measure to reduce the elementcontent. The conclusion is20#steel corrosion product film will be dissolved in the crude oil.（4）Using the weight loss method, scanning electron microscopy and X-ray spectroscopyto study the behavior of phytic acid on Q235steel corrosion in NaCl solution and its impactfactor. The weight loss experiment results show that Phytic acid accelerate the corrosion ofsteel Q235under acidic conditions.In neutral and alkaline conditions, phytic acid inhibitedcorrosion of steel Q235significantly. With the increasing concentration of phytic acid，Q235steel corrosion inhibition efficiency increases in NaCl solution. When phytic acidconcentration is more than0.5%, inhibition efficiency is more than90%. SEM results showthat，the film generated in alkaline conditions by Q235steel treated by phytic is significantlybetter than under acidic conditions.