Common problem of production failure of electric submersible pump outer cylinder anti-corrosion technology

Electric submersible pump is one of the important means of long-term stable production in oilfield, but the problem of failure of electric submersible pump in oilfield production is very common. The survey found that the failure rate of ESP due to corrosion of the electric submersible pump outer cylinder varies from 4% to 83% of the total electric submersible pump well with the different oilfield conditions.
Submersible pump downhole depth is generally 1000-2500 meters, directly immersed in oil, natural gas, water and a certain amount of mixed sand medium. Mixed media pressure of 12-25MPa, the temperature is generally 50 ℃, 90 ℃, 120 ℃, 150 ℃ several levels. In this environment, electric submersible pump outer cylinder not only produce chemical corrosion, electrochemical corrosion, but also wear phenomenon. The specific causes of corrosion and wear are as follows: 1. The existence of Cl, H2S and CO2 in the mixed media makes the oil layer have special corrosion properties, directly threatening the service life of the outer cylinder of the electric submersible pump. H2S corrosion may be the most detrimental to the electric submersible pump outer cylinder. The corrosion product and the electric submersible pump outer cylinder form a corrosive battery when they are in direct contact. The electric submersible pump outer cylinder that is the anode is rapidly corroded; corrosion products and salt if long term Deposition of the pump barrel will not be cleared, will lead to corrosion of the outer cylinder intensified; when the crude oil moisture content of more than 80% -90%, the corrosive nature of the reservoir liquid also increased sharply. 2. The hydraulic impact on the outer cylinder surface of the submersible pump further aggravates the formation and collapse of the crude oil bubbles on the surface of the submersible submersible cylinder which becomes hot and increases the degree of corrosion and wear of the outer cylinder of the submersible pump. In addition, Vibrations can cause fretting wear between the pump barrel and the casing. Practice has proved that in corrosive media, even the tiny vibration of the pump outer cylinder will cause severe wear of the pump outer cylinder.

There are two ways to solve the above problems: First, the use of special materials to adapt to various well conditions, the replacement of the original outer tube material, this method is feasible but costly, not easy to promote. Second, select the appropriate surface treatment technology and surface coating materials to cover the surface of the electric submersible pump outer cylinder to prevent corrosion and wear. This method is low cost and works well, and with the development of materials and surface engineering techniques, more and more materials and surface treatment processes are put into use to better meet the increasingly demanding use of surface coatings.

From the material design point of view, the new material branch of Beijing Anton Bull Engineering & Technology Co., Ltd. has developed a new anti-erosion technology for the outer cylinder of the electric submersible pump taking AOC-240 alloy material as its core. The technology is the use of thermal spraying method AOC-240 material sprayed on the outer surface of the electric submersible pump to obtain a layer of about 0.2 mm thick, that is corrosion-resistant and has good wear resistance of high-alloy coating. The coating has the following characteristics: The coating has excellent corrosion resistance under various well conditions; Strong bonding strength between the coating and the substrate; Good anti-fretting wear resistance; Good coating Oil and water resistance and anti-scaling performance; coating has excellent heat resistance and thermal conductivity.

The use of this technology to deal with the submersible pump greatly enhances the outer tube of electric submersible pump corrosion resistance and wear resistance, so that the service life of electric submersible pumps increased by 10 times. At present, electric submersible pumps with AOC-240 coating are widely used in oil fields such as Daqing, Bohai, Liaohe and are well received by users.