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| Prediction of CO2 Corrosion Rate of Production Casing Considering Annulus Pressure |
| Received:September 13, 2020 Revised:September 30, 2020 |
| View Full Text View/Add Comment Download reader |
| DOI：10.7643/issn.1672-9242.2021.01.005 |
| KeyWord:offshore platform carbon steel production annulus pressure casing CO2 corrosion |
| Author | Institution |
| LIU He-xing |
Zhanjiang Branch, CNOOC Limited, Zhanjiang , China |
| LIU Jin-ming |
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu , China |
| MENG Wen-bo |
Zhanjiang Branch, CNOOC Limited, Zhanjiang , China |
| ZHANG Zhi |
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu , China |
| LI Yan-jun |
Zhanjiang Branch, CNOOC Limited, Zhanjiang , China |
| LIANG Ji-wen |
Zhanjiang Branch, CNOOC Limited, Zhanjiang , China |
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| Abstract: |
| To predict the corrosion rate of carbon steel casing with different productions and temperature changes in consideration of annulus pressure. The optimized classical semi-empirical model is used to predict the corrosion rate of carbon steel casing. The CO2 corrosion mechanism of carbon steel casing in marine environment is clarified, and the main influencing factors and corrosion mechanism of production casing in seawater arefound out. The corrosion rate prediction model is optimized by the CO2 solubility model, and the corrosion rate of production casing is predicted by considering the influence of temperature, annulus pressure, and production. The annulus pressure distribution after the production change is calculated. The higher the production is, the greater the annular pressure is, but the increase of the annular pressure will be no longer obvious when the production increases to a certain value. As the production can affect the annulus temperature distribution, the temperature change is related to the thermal expansion pressure and can affect the corrosion rate of casing. The reliability of the corrosion prediction model is verified by high temperature and high pressure indoor corrosion experiment. The experimental results show that the prediction error of the model is less than 10%, which meets the needs of corrosion prediction. Production, temperature, CO2 solubility, annulus pressure, and other factors have a great impact on corrosion. Considering the change of annulus pressure, the overall corrosion rate of production casing is far higher than the industry standard of 0.076 mm/A, so some corrosion inhibition measures should be taken. |
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