| FAN Ya-ping,ZHOU Yi-nuo.Effects of H2S/CO2 Corrosion Scale on Corrosion Behavior of T95 Casing Steel at Different Temperature[J],45(10):180-186 |
| Effects of H2S/CO2 Corrosion Scale on Corrosion Behavior of T95 Casing Steel at Different Temperature |
| Received:May 11, 2016 Revised:October 20, 2016 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2016.10.028 |
| KeyWord:H2S/CO2 corrosion gaseous phase/liquid phase corrosion scale T95 casing steel corrosion behavior temperature |
| Author | Institution |
| FAN Ya-ping |
Weifang University of Science and Technology, Weifang , China |
| ZHOU Yi-nuo |
China Huanqiu Contracting & Engineering Co., Ltd, Beijing , China |
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| Abstract: |
| The work aims to explore the effects of H2S/CO2 corrosion scale on corrosion behavior of T95 casing steel at different temperature. T95 steel was cut into 15 mm×10 mm×3 mm specification, and its specific size was measured by using micrometer and weighed with AR2140 electronic balance after surface polishing. The test blocks were placed on the upper and lower brackets vertically, and the lower bracket was put on the bottom of the kettle steadily, then simulated formation water was filled. It was necessary to ensure that sample on the lower bracket was immersed by test medium without contacting with sample on the upper bracket. Provided with good air tightness, H2S, CO2 and N2 were supplied in turn after filling with N2 continuosly for 2 h for oxygen removal, and then temperature and pressure were improved to meet experimental requirements. The samples were taken out from gaseous and liquid phases after 72 h, the microscopic morphology of corrosion scale was observed under an electron microscope by sampling. Compositions of the corrosion scale were analyzed by X-ray energy spectrometer. Corrosion rate of samples in gaseous/liquid phases after removing corrosion products was calculated. The corrosion rate of T95 casing steel in liquid phase of H2S/CO2 was higher than that in gas phase, which might result from that the liquid corrosion scale was more porous than the gaseous corrosion scale. Temperature had great influence on formation of H2S/CO2 corrosion scale which became thicker as temperature increased while the film-forming effect became worse. The corrosion scale at high temperature had protective effect so that the increase of corrosion rate slowed down graduallly. The major components of corrosion scale on T95 steel was FexSy serial compounds and FeCO3. Meanwhile, Cr(OH)3 and Cr2O3 non-amorphous products were also generated to prevent anions from penetrating into the corrosion scale, reduce anion solution contacting with metal substrate interface, inhibit anodic reaction and further decrease the corrosion rate. Forming of corrosion scale resulted in significant increase of time constant and Rt value of interface reaction, which hindered further development of corrosion to a certain extent. Temperature has great influence on the formation of H2S/CO2 corrosion scale which becomes thicker as temperature increases while the film-forming effect becomes worse. When temperature exceeds 120 ℃, the corrosion scale has protective effect so that the increase of corrosion rate slows down graduallly. |
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