Electric Submersible Pumps (ESP's) are a widely used artificial lift technology. Conventional ESP systems provide power with a cable banded to the outside of the tubing. These systems have drawbacks in terms of installation speed and efficiency. To overcome these obstacles, a novel cable-deployed ESP system developed for use in a high H2S production environment is a future solution. This paper focuses on the material selection process and validation of the nontraditional National Association of Corrosion Engineers (NACE) selected materials.
An evaluation process was developed and used early on to narrow down several potential alternatives. A metal-jacketed power cable was selected as the most viable solution since it provided the best protection to H2S attack and provided a smooth outside diameter that could be gripped on and sealed. The cable is required to withstand H2S levels up to 15% and chloride levels in excess of 150,000 ppm for a minimum of 5 years. A major challenge was developing a method to construct the system that supported the weight of the cable inside the metal jacket. The cable was qualified through extensive physical and chemical testing.
Interlocking of the metal jacket (tubing) with the inner core (cable) was qualified through extensive mechanical testing of the power cable. Testing included pull resistance, bend, thermal growth, and mechanical splice connections. Electric testing included insulation resistance. Chemical compatibility testing was performed on a number of metallurgies using a modified NACE H2S Sulfide Stress Cracking test based upon ANSI/NACE Standard TM0177. H2S test coupons of the various metallurgies were welded and formed, for testing of the tubing. The test coupons were bent to stress levels in excess of the final design stresses.
The high chloride levels caused several metallurgies to fail even at low H2S levels. A single metallurgy successfully passed all the physical, electrical, and chemical testing and will be used for field trials of the technology.
A rigorous evaluation and test program resulted in development of a novel high-H2S-rated cable-deployed ESP (CD ESP) system that can improve the speed, efficiency, and ease of ESP deployment.