Analyzing the failure reasons and the breakdown pattern of different components of production electrical submersible pumps demonstrated that it is the inside surface of diffuser casing, sealing rings, as well as suction and injection impeller covers that are getting most intensively destroyed and/or incrusted by scaling in the course of operation. There are two technologies that have been outlined recently among other methods of controlling the above problems: introducing inhibitors and applying polymer coating.
After a number of experiments, REAM-RTI chose the CHEMLON polymer engineering coating manufactured by Akzo Nobel N.V. as coating material. This coating was applied on diffusers and impellers. The coating quality has been tested at the central factory laboratory of NOVOMET-PERM, where:
1) the thickness and evenness of the polymer coating has been evaluated;
2) the coating resistance to the impact of various mediums has been researched;
3) the operating elements have been tested at a special plant imitating the ESP operation in the conditions of hydroabrasive deterioration of pumping stages.
Due to performed testing operations, the CHEMLON coating, applied as per the REAM-RTI technology, can be considered to be of high chemical resistance to the impact of the simulated medium, imitating heated reservoir fluid with high water cut, air atmosphere with the humidity of nearly 100 percent and heated synthetic oil. The coating adhesion and its cohesion with metal are considered to be of the highest mark.
Hydroabrasive testing has discovered the minimal value of the coating deterioration on the outer surfaces of the diffuser casing and impeller disks. The area with the increased surface deterioration is the inside surface of diffuser casing and inside surface of the upper disc of impeller covers. This suggests that the coating thickness in the said areas should be no less than 100 mcm. The coating formed on the surface of metalware is not wettable by saline solutions, highly resistant to aggressive chemical mediums, highly heat-resistant (long-term operation temperature of up to 260 C), extremely strong and tough.
The tests have demonstrated the promising character of the special polymer composites to be used for ESPs in scale-forming oil and gas deposits with high content of mechanical contaminants.
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