With the rapid development of the petroleum industry, serious corrosion of buried pipelines,
oil well casings and storage tank floors inside oil fields, especially oil well casings, has had a serious impact on the production, development and environment of oil fields. There is corrosion on both the inner and outer walls of oil and gas well casings, among which internal corrosion is more serious. So, how to protect the corrosion of the inner and outer walls of oil casing? Let’s take a brief look at it with
PMC oil casing manufacturer:
1. Inner wall corrosion of oil and gas well casing
To solve the corrosion problem of the inner wall of oil well casing, we usually add bactericides, corrosion inhibitors, pH adjustment, airtight oxygen isolation technology in the oil well annular space, and use low-strength oil casing in sulfur-containing oil and gas fields.
2. Corrosion of outer wall of oil and gas well casing
To solve the corrosion problem of the outer wall of oil well casing, cathodic protection technology is generally adopted. Now, this has been recognized by the anti-corrosion industry at home and abroad. To avoid soil corrosion of underground steel structures, cathodic maintenance is an economical, reasonable and effective maintenance measure. Cathodic maintenance is a safe and mature anti-corrosion technology. It has the characteristics of strong maintenance ability, simple construction and low investment. This technology is increasingly used in petrochemical and oil and gas sectors. Cathodic protection technology can not only prevent corrosion of newly built oil well casings, but is also very effective for existing old oil well casings. It can extend the service life and reduce the number of replacements, and the economic benefits are very significant.
Since the oil and water well casings are thousands of meters deep into the underground strata, the application of sacrificial anodes is subject to certain restrictions, and only the impressed current method can be used for cathodic protection. The impressed current method of cathodic protection uses an external DC power source to cathodicly polarize the steel casing to reach the required protection potential value, thereby achieving cathodic protection. The impressed current cathodic protection system is composed of auxiliary anode, reference electrode, DC power supply and related connecting cables and protected objects.
There are generally two structural forms of the cathodic protection system for oil well casing: one is to provide protective current to the casing in separate wells and implement cathodic protection. Each well is equipped with insulation measures from other wells so that the current can be concentrated to protect the single well.This kind of system saves electricity, is easy to realize automatic control, and is easy to check faults and repair. The disadvantage is that it requires a large investment. The other is to connect the underground metal structures in the protection area together and perform regional cathodic protection in a unified manner. This system has the advantage of reducing the number of control systems and saving investment. The disadvantage is that the protection current is not easy to distribute evenly, the anode layout is strictly required, and it is difficult to detect faults.
The choice of these two structural forms should be based on the spacing of each oil well, the specific conditions of the oil field station and the owner's requirements.
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