| XU Gang,LIU Peng,ZHANG Qi-long,CHEN Yi,CHEN Bin.Analysis of Casing Damage on Typical Wells in Bohai Oilfield[J],46(7):168-172 |
| Analysis of Casing Damage on Typical Wells in Bohai Oilfield |
| Received:January 30, 2017 Revised:July 20, 2017 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2017.07.028 |
| KeyWord:Bohai Oilfield casing surface damage casing damage cause casing damage type cavitation effect corrosion prevention |
| Author | Institution |
| XU Gang |
Tianjin Branch of CNOOC Co., Ltd, Tianjin , China |
| LIU Peng |
Tianjin Branch of CNOOC Co., Ltd, Tianjin , China |
| ZHANG Qi-long |
Tianjin Branch of CNOOC Co., Ltd, Tianjin , China |
| CHEN Yi |
Tianjin Branch of CNOOC Co., Ltd, Tianjin , China |
| CHEN Bin |
Tianjin Branch of CNOOC Co., Ltd, Tianjin , China |
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| Abstract: |
| The work aims to lay a foundation for prevention and control of casing damage wells by finding out causes of well casing damage in Bohai Oilfield. According to the detected 32 casing damage wells and relevant data collection, statistics was analyzed in respect of block distribution, damage vertical distribution, production period and damage type. Corresponding rule was found out based upon the statistical results. Causes and mechanisms of casing damage accidents were explored in respect of stratum conditions, corrosion conditions and cavitation corrosion near casing damage points, and corresponding prevention measures were proposed to improve service life of the wells. It was concluded that casing damage wells were mainly present in some old oilfields, and casing damage points were mostly in well section within the depth of 2000 m. The damage points were located in bottom water layer of the Minghuazhen Formation and near inlet of annulus injection well. Corrosion was the main cause of casing damage in the Bohai Oilfield. Injection fluid and external formation water were main mediums of corrosion. Long-term high-speed fluid erosion, abrupt change of casing flow velocity and casing without cement ring would accelerate the degree of casing damage. In order to prevent casing damage of new wells, it is suggested that the wells at the bottom of the Minghuazhen Formation shall be completely sealed during well cementation to prevent direct contact between the casing and formation water from weakening corrosion effect. For new injection wells, it is suggested to improve quality standard of injection water, reduce injection volume and increase over-flow area of the inlet, avoid annulus injection mode and minimize long-term exposure of injection fluid to casing. |
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