The casing damage has been a big problem in oilfield production. The current detection methods mostly are used after casing damage, which is not very effective. With the rapid development of China's offshore oil i...The casing damage has been a big problem in oilfield production. The current detection methods mostly are used after casing damage, which is not very effective. With the rapid development of China's offshore oil industry, the number of offshore oil wells is becoming larger and larger. Because the cost of offshore oil well is very high, the casing damage will cause huge economic losses. What's more, it can also bring serious pollution to marine environment. So the effective methods of detecting casing damage are required badly. The accumulation of stress is the main reason for the casing damage. Magnetic anisotropy technique based on counter magnetostriction effect can detect the stress of casing in real time and help us to find out the hidden dangers in time. It is essential for us to prevent the casing damage from occurring. However, such technique is still in the development stage. Previous studies mostly got the relationship between stress and magnetic signals by physical experiment, and the study of physical mechanism in relative magnetic permeability connecting the stress and magnetic signals is rarely reported. The present paper uses the ANSYS to do the three-dimensional finite element numerical simulation to study how the relative magnetic permeability works for the oil casing model. We find that the quantitative relationship between the stress' s variation and magnetic induction intensity's variation is: Δδ =K* ΔB, K = 8.04×109, which is proved correct by physical experiment.展开更多
The casing damage is a serious problem when the steam-injection method is applied in the oilfields. In this work, the commercial software ANSYS is used to predict the thermal expansion and the thermal stresses of casi...The casing damage is a serious problem when the steam-injection method is applied in the oilfields. In this work, the commercial software ANSYS is used to predict the thermal expansion and the thermal stresses of casings in steam-injection wells under different conditions, including steam channeling, well shut-in and cavitation in cement ring. The results indicate that nearly no temperature change occurs in oil-layer areas 4.0 m-6.0 m away from the casing center. When steam channeling appears, the maximum Mises stress of both the casing and the cement ring occurs on the interior wall. During the shut-in operation, while the maximum thermal expansion ocurs within the temperature-transition area, the maximum thermal stress will be on the interior wall of casing, exceeding the thermo-elastic yield ultimate stress of N80 steel. Besides, the thermal stress is much higher than the elastic strain limit if certain amounts of cavitations appear in the cement ring. Based on the results, some preventive measures against casing damage are proposed, which are verified through the successful application of TP120TH casings during well completion in Liao＇he oilfield.展开更多
基金supported by the National Natural Science Foundation of China(No.41174157)
文摘The casing damage has been a big problem in oilfield production. The current detection methods mostly are used after casing damage, which is not very effective. With the rapid development of China's offshore oil industry, the number of offshore oil wells is becoming larger and larger. Because the cost of offshore oil well is very high, the casing damage will cause huge economic losses. What's more, it can also bring serious pollution to marine environment. So the effective methods of detecting casing damage are required badly. The accumulation of stress is the main reason for the casing damage. Magnetic anisotropy technique based on counter magnetostriction effect can detect the stress of casing in real time and help us to find out the hidden dangers in time. It is essential for us to prevent the casing damage from occurring. However, such technique is still in the development stage. Previous studies mostly got the relationship between stress and magnetic signals by physical experiment, and the study of physical mechanism in relative magnetic permeability connecting the stress and magnetic signals is rarely reported. The present paper uses the ANSYS to do the three-dimensional finite element numerical simulation to study how the relative magnetic permeability works for the oil casing model. We find that the quantitative relationship between the stress' s variation and magnetic induction intensity's variation is: Δδ =K* ΔB, K = 8.04×109, which is proved correct by physical experiment.
文摘The casing damage is a serious problem when the steam-injection method is applied in the oilfields. In this work, the commercial software ANSYS is used to predict the thermal expansion and the thermal stresses of casings in steam-injection wells under different conditions, including steam channeling, well shut-in and cavitation in cement ring. The results indicate that nearly no temperature change occurs in oil-layer areas 4.0 m-6.0 m away from the casing center. When steam channeling appears, the maximum Mises stress of both the casing and the cement ring occurs on the interior wall. During the shut-in operation, while the maximum thermal expansion ocurs within the temperature-transition area, the maximum thermal stress will be on the interior wall of casing, exceeding the thermo-elastic yield ultimate stress of N80 steel. Besides, the thermal stress is much higher than the elastic strain limit if certain amounts of cavitations appear in the cement ring. Based on the results, some preventive measures against casing damage are proposed, which are verified through the successful application of TP120TH casings during well completion in Liao＇he oilfield.
