What are the Anti-Corrosion Processes of Oil Casings?

The corrosion of the oil casing is related to the partial pressure of 

the corrosive gas, the ambient temperature, the water content, the 
salinity, the flow rate, and the pH value. So what are the anti- 
corrosion processes for oil casings? 

Let's take a brief look at:

1. Cement sealing and anti-corrosion technology

In the early stage, the main reason for the damage of the casing was 
that the cement was not able to return high, and the external water 
layer was not completely sealed, and corrosive gas in the water layer 
was formed to corrode the surface of the casing to form corrosion. 
Therefore, in the 1980s, the strategy of increasing the cement height 
was proposed to increase the corrosion resistance of the casing. After 
this technique, the corrosion level of the casing is reduced, but the 
casing corrosion is not completely prevented, so the corrosion 
resistance of the casing is not raised from the spring source.

2. Use corrosion-resistant alloy pipe

Since 2000, the anti-corrosion plan for offshore oil casings has begun 
to seek treatment plans from materials to improve the corrosion 
protection of the oil casings, thus completely dealing with the 
corrosion problems of the oil casings. In the frequency test, through 
the indoor test, under the conditions of affirmative temperature and 
pressure conditions and corrosive gas, the Cr-containing pipes such as 
1Cr, 3Cr, 9Cr and 13Cr were evaluated, and an anti-corrosion plate 
suitable for the oil casing of the offshore oil and gas field was 
developed.

3. Inject corrosion inhibitor

From the completion of the completion process, if the formation 
contains oily corrosive gases, chemical antiseptic agents will be 
added to the well fluid for anti-scaling, anti-wax and anti-corrosion. 
Therefore, the use of chemical methods for the corrosion protection of 
oil casings is also a common means outside China. Depending on the 
difference in the oil and gas field, it may be possible to use a batch 
or continuous injection of corrosion inhibitor for corrosion 
protection. The amount of injection varies depending on 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. Apply anti-corrosion coating tube

Regarding oil casings, it is also a useful anti-corrosion method to 
use anti-corrosion coatings in China to block their infiltration in 
corrosive gases. Some oilfields use nitriding technology for internal 
and external corrosion protection of oil pipes, and their wear 
resistance is good. However, the anti-corrosion method of the inner 
and outer walls will accelerate the corrosion of the inner wall of the 
casing at a certain level, and the nitriding pipe will be rough, which 
will make the oil pipe The knot is tighter than the other types of 
tubes. In addition, some oil and gas fields use epoxy powder coating, 
titanium nano coating, epoxy ester phenolic coating to prevent 
corrosion.