| ZHANG Hai-shan.Experimental Research on the Anti-corrosion Design out of the Tube and Casing Material Selection Chart in the Offshore Oilfields[J],45(5):111-117 |
| Experimental Research on the Anti-corrosion Design out of the Tube and Casing Material Selection Chart in the Offshore Oilfields |
| Received:January 25, 2016 Revised:May 20, 2016 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2016.05.017 |
| KeyWord:corrosion tube and casing CO2 corrosion CO2 partial pressure anti-corrosion design corrosion rate 13Cr steel HTHP Autoclave |
| Author | Institution |
| ZHANG Hai-shan |
CNOOC China Limited-Shanghai, Shanghai , China |
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| Abstract: |
| Objective The content of CO2 partial pressure of the development reservoir fluid on the Gas Field A in the East China Sea is about 1.85 MPa, and the temperature is about 150 ℃. The parameters of downhole corrosion environment are out of the application scope of CNOOC tube and casing material selection chart, therefore, corrosive simulation experimental research should be carried out, which provides the foundation for optimization of tube and casing material. Methods In the experiment, weight loss method was used to dynamically test the corrosion rates of different tube and casing materials under the downhole condition by HTHP Auto Clave. The material samples were ordinary 13Cr, super 13Cr and 22-25Cr duplex stainless steel, high anticorrosive tubing and casing, which are commonly used in oil and gas field development. Results The results of experiment showed that localized pitting wasn’t found in 3 kinds of material samples under the condition of CO2 partial pressure at 2 MPa and 130 ℃; when the temperature rose to 150 ℃, uniform corrosion characteristic was present for super 13Cr and 22-25Cr duplex stainless steel, pitting was present on ordinary 13Cr, and the pitting rate was 0.6413 mm/a, which significantly exceeded the corrosion control line. When the temperature was below 150 ℃, with the increase of CO2 partial pressure, the corrosion rate increased, but after CO2 partial pressure exceeded 2.0 MPa, the increase of corrosion rate became slow, and the trend of decline occurred. From the bottom of a well-developed reservoir to the ground, the temperature was gradually reduced. Conclusion According to the experimental results, the development of the Gas Field A in the East China Sea designs the means of combination of tube and casing in ordor to protect corrosion, super 13Cr materials should be used in the deep location at temperature higher than 130 ℃, while ordinary 13Cr should be used in the upper location at temperature below 130 ℃, which could realize the cost saving of tube and casing. |
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