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| Crevice Corrosion at Screwed Joint with Tensile Stress |
| Received:September 28, 2020 Revised:October 10, 2020 |
| View Full Text View/Add Comment Download reader |
| DOI：10.7643/issn.1672-9242.2020.11.008 |
| KeyWord:crevice corrosion stress corrosion thread high temperature and pressure |
| Author | Institution |
| ZHONG Xian-kang |
Petroleum Engineering School, Southwest Petroleum University, Chengdu , China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu , China |
| ZHENG Zi-qi |
Petroleum Engineering School, Southwest Petroleum University, Chengdu , China |
| MO Lin |
Natural Gas Research Institute of Southwest Oil and Gas Field Company Chengdu , China |
| QING Yang |
Central Sichuan Oil and Gas Deposit of Southwest Oil and Gas Field Company, Suining , China |
| YU Si-yu |
Petroleum Engineering School, Southwest Petroleum University, Chengdu , China |
| HU Jun-ying |
Petroleum Engineering School, Southwest Petroleum University, Chengdu , China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu , China |
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| Abstract: |
| The work aims to study the corrosion behavior of N80 steel under the combined crevice and tensile stress in high temperature and high pressure environment, to provide reference for selection of oil well pipe and thread. With screwed joint of oil tube as the research object, the corrosion behaviors of N80 steel under single factor and crevice-stress coupling factor were studied by electrochemical techniques and surface analysis methods in stratum simulated by high temperature and high pressure autoclave. Under the single action of crevice for 24 h, a large number of corrosion products accumulated in the crevice, and almost no corrosion products accumulated outside the crevice. The groove depth at 40 ℃ was 17.2 μm, while the groove depth at 70 ℃ was 82.7 μm. Under the combined effect of crevice and stress for 24 h, corrosion products were found to accumulate at the crevice mouth, and the corrosion degree in the crevice was more serious than that outside the crevice. At 40 ℃, the groove depth at the crevice mouth with elastic deformation specimen was about 35.3 μm, and that at the crevice mouth with plastic deformation specimen was about 41.3 μm. However, at 70 ℃, the groove depth at the crevice mouth of the specimen with elastic deformation and plastic deformation was 143.7 μm and 243.9 μm respectively. Under the coupling effect of crevice and stress, the depth of groove at the crevice mouth is deepened, and with the increase of corrosion time and temperature, the depth of groove increases to the deepest when plastic deformation occurs. This shows that the application of stress will aggravate the crevice corrosion of N80 steel and lead to the formation of deeper corrosion grooves, which in turn will lead to the further concentration of stress, resulting in higher stress corrosion. Therefore, crevice and stress have synergistic effect on corrosion of N80 steel in high temperature and high pressure formation water environment. |
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