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Submersible pump outer cylinder anti-corrosion technology to solve the problem
Electric submersible pumps play a crucial role in ensuring long-term stable production in oil fields. However, pump failures are a common and costly issue. Studies have shown that the failure rate of electric submersible pumps (ESPs) due to corrosion of the outer cylinder can range from 4% to as high as 83%, depending on the specific conditions of each oil field.
These pumps are typically installed at depths between 1,000 and 2,500 meters, where they are directly exposed to a complex mixture of crude oil, natural gas, water, and sand under high pressure—typically between 12 and 25 MPa. The temperature can vary significantly, ranging from 50°C up to 150°C. In such harsh environments, the outer cylinder of the ESP is subjected to both chemical and electrochemical corrosion, as well as mechanical wear. The main causes of this damage include:
1. **Corrosive Components**: The presence of chloride ions (Clâ»), hydrogen sulfide (Hâ‚‚S), and carbon dioxide (COâ‚‚) in the produced fluids creates highly corrosive conditions. Hâ‚‚S is particularly damaging, as it can form a corrosive battery when in contact with the pump’s surface, leading to rapid degradation. Additionally, prolonged accumulation of corrosion products and salts on the pump barrel can further accelerate the corrosion process. When the moisture content in the crude oil exceeds 80–90%, the corrosive nature of the fluid increases dramatically.
2. **Hydraulic and Mechanical Stress**: Hydraulic impacts and the formation and collapse of crude oil bubbles on the pump surface can intensify corrosion and wear. Moreover, vibrations caused by the operation of the pump can lead to fretting wear between the pump casing and the tubing, even under minor movement. This type of wear is especially severe in corrosive environments.
To address these challenges, two primary approaches are commonly used. The first involves using advanced materials to replace the original outer cylinder material. While effective, this method is expensive and not always practical for widespread implementation. The second approach focuses on applying surface treatments or coatings to protect the pump's exterior. This is more cost-effective and has become increasingly popular as advancements in materials science and surface engineering continue to provide better solutions.
From a material design perspective, Beijing Anton Bull Engineering and Technology Co., Ltd. has developed an innovative anti-erosion technology using AOC-240 alloy. This technology involves thermal spraying of AOC-240 material onto the outer surface of the pump, creating a thin but highly durable coating of approximately 0.2 mm. The resulting layer offers excellent resistance to both corrosion and wear, with the following key properties:
- Outstanding corrosion resistance across various well conditions
- Strong adhesion to the base material
- Excellent resistance to fretting wear
- Good oil and water repellency, along with anti-scaling performance
- Superior heat resistance and thermal conductivity
By applying this coating, the service life of electric submersible pumps can be increased by up to ten times. These coated pumps are now widely used in major oil fields such as Daqing, Bohai, and Liaohe, and have received positive feedback from operators due to their enhanced durability and reliability.