Corrosion of oil casing is related to factors such as partial pressure of corrosive gas, ambient temperature, water content, salinity, flow rate, pH value and so on. So what are the anti-corrosion processes of the oil casing pipe? Let ’s take a brief look:
1. Cement sealing anticorrosion skills
In the earliest period, after analysis, it was thought that the key point of casing damage was due to the inability of the cement to return to high, the formation of the external water layer was not completely sealed, and the formation of corrosive gases in the water layer corroded the surface of the casing to form corrosion. Therefore, in the 1980s, it was proposed to increase the cement back to increase the corrosion resistance of the casing. After this technique, the casing corrosion level has been reduced, but the casing corrosion has not been completely prevented, so the casing anti-corrosion function has not been raised from the spring.
2. Using corrosion-resistant alloy pipes
Since 2000, the anti-corrosion plan for offshore oil casing began to seek a treatment plan from the material to improve the anti-corrosion function of the oil casing, so as to completely deal with the corrosion problem of the oil casing. Frequent years, after laboratory tests, under certain temperature and pressure conditions and corrosive gas conditions, 1Cr, 3Cr, 9Cr, 13Cr and other Cr-containing pipes were evaluated, and a set of corrosion-resistant plates suitable for offshore oil and gas field oil casings was drawn up.
3. Inject corrosion inhibitor
Starting from the completion process, if the formation contains oily corrosive gas, chemical anti-corrosion agents will be added to the well fluid to prevent scale, wax and corrosion. Therefore, the use of chemical methods to protect the oil casing is also a common practice outside China. According to the difference of the oil and gas field itself, it may be appropriate to use intermittent or continuous injection of corrosion inhibitor for corrosion protection, and the amount of injection also varies according to the corrosive environment of the oil and gas field. Since the demand for the addition of corrosion inhibitors has continued, on the one hand, the cost is higher, and it will also have a positive impact on the on-site production.
4. Using anti-corrosion coating tube
As for the oil casing, it is also a useful anti-corrosion method to prevent corrosion of corrosive gas by anti-corrosion coating. Some oilfields use a nitriding process for the internal and external corrosion protection of the tubing, which has good wear resistance, but this method of anticorrosion on both the internal and external walls will accelerate the corrosion of the casing inner wall at a certain level. Yusaka is more important than other types of tubes. In addition, some oil and gas fields use epoxy powder coating, titanium nano-coating, epoxy ester phenolic coating and other methods for corrosion protection.