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| Study on Tubing and Casing Material Selected for Low H2S Gas Well in Middle-deep Layers of Bohai Oilfield |
| Received:April 10, 2020 Revised:October 06, 2020 |
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| DOI：10.7643/issn.1672-9242.2021.01.008 |
| KeyWord:middle-deep layer downhole string material selection HTHP corrosion rate stress corrosion |
| Author | Institution |
| XING Xue-song |
CNOOC Research Institute Co., Ltd., Beijing , China |
| XING Xi-jin |
CNOOC Research Institute Co., Ltd., Beijing , China |
| ZHANG Jun-ying |
China University of Petroleum Beijing, Beijing , China |
| FAN Bai-tao |
CNOOC Research Institute Co., Ltd., Beijing , China |
| GENG Ya-nan |
CNOOC Research Institute Co., Ltd., Beijing , China |
| CHEN Chang-feng |
China University of Petroleum Beijing, Beijing , China |
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| Abstract: |
| To achieve the safe material selection of tubing and casing in the downhole environment with low H2S content in the middle and deep layers of the Bohai Oilfield, this paper simulates the corrosion environment of gas wells through the autoclave, analyzes the corrosion rate and stress corrosion cracking behavior of alternative casing and tubing steels with different materials under simulated working conditions for different well depths, discusses and tests the corrosion morphology and chemical composition of corrosion products by SEM, EDS and XRD, as well as proposes the selection scheme of casing and tubing in this gas field with consideration of uniform corrosion and cracking. There was no stress corrosion cracking of carbon steel under gas field conditions, but the corrosion rate was 0.242 mm/a to 0.6003 mm/a. No stress corrosion cracking occurred in S13Cr under gas field conditions. The maximum corrosion rate of wells at middle layer is 0.0399 mm/a and that of wells at deep layer is 0.1633 mm/a. 2507 super duplex stainless steel and 2535 nickel-based alloy have low susceptibility to stress corrosion cracking in simulated environments, and the corrosion rates were 0.0122 mm/a and 0.0083 mm/a, respectively. According to experimental research results, S13Cr is suggested to be used in whole wells at middle layer with temperature lower than 180 ℃, and 2507 super duplex stainless steel and 2535 nickel-based alloy are suitable for wells at deep layer with temperature higher than 180 ℃. In order to save the investment of wells at deep layer, the anti-corrosion scheme of combined string can be considered. |
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