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| Flow corrosion of casing steel for oil and gas field in two-phase flow |
| ZHOU Hao1,2,JI Qingfeng1*,LIU Wen2,MA Hongyan3, WANG Lei4 |
| 1. Colloge of Hydraulic Science and Engineering, Yangzhou University, Yangzhou, Jiangsu 225127, China; 2. School of Petroleum Engineering, Changzhou University, Changzhou, Jiangsu 213016, China; 3. Jiandong College, Changzhou, Jiangsu 213032, China; 4. Gas Transportation Management Department, Petrochina Southwest Oil and Gas Field Company, Chengdu, Sichuan 610000, China |
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Abstract The influence of different silica sand mass fractions and flow corrosion time on the mass loss rate and corrosion electrochemical behavior of N80 casing steel in liquid-solid two-phase flow fluid containing silica sand and chloride ion was investigated with a rotating cylindrical electrode device and an electrochemical workstation. The surface of specimens after flow corrosion was characterized and analyzed by three-dimensional digital microscope Smartzoom 5. The results show that the flow corrosion morphology of N80 steel in liquid-solid two-phase flow containing silica sand and chloride ion is typical particle cutting trace with a few corrosion pits, and the mechanism of flow corrosion is synergistic inte-raction between erosion and corrosion processes. In the range of sand mass fraction from 1% to 3%, the flow corrosion rate increases with the increase of sand mass fraction. However, when the sand mass fraction increases to more than 4%, larger sand content forms a ″shielding effect″, which reduces the flow corrosion rate. With the variation of two factors, the polarization rate of the cathode polarization curve is much higher than that of the anode polarization curve for N80 steel flow corrosion process. The corrosion reaction is controlled by oxygen depolarization reaction of cathode. With the increase of time, the mass loss of N80 steel in liquid-solid two-phase flow fluid increases linearly, and the corrosion rate gradually decreases which reaches the lowest at 9 h and then increases.
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Received: 28 May 2018
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