The objective of this paper is to share insights on mitigating sucker rod corrosion damage in vertical, horizontal, and deviated wells with aggressive corrosive conditions such as H2S and CO2, particularly those with histories of corrosion-related rod and tubing failures.

Corrosion is a common problem in production operations, accounting for two-thirds of all rod string failures and costing hundreds of millions annually to remediate downhole tubing damage alone, according to NACE International. This paper presents the development and initial field application results of a continuously applied metallic coating that actively participates in the electrochemical aspects of corrosion in carbon and low-alloy steels. Moreover, the solution protects uncoated segments of rod and other steel components in the wellbore while reducing abrasion by enhancing friction properties compared to bare steel.

The authors outline the key properties and characteristics of this coating, including evaluating its performance relative to traditional corrosion protection measures such as barrier coatings. Rather than acting as a barrier layer, the metallic coating actively protects against corrosion and has inherent physical properties that self-heal surface scratches and abrasions. This is particularly valuable in horizontal and directional wells with high dog leg severities and sideloading forces that contribute to rod/tubing abrasion.

Results are presented from laboratory testing as well as initial trial applications in wells with histories of rod failures due to corrosion, typically requiring interventions with workover rigs. In one such trial, the metallic coating was applied to a coiled rod string installed in a high-CO2 content well on progressing cavity pump. The coated coiled rod string was installed in January 2019. After five months of service, the coated string was pulled to inspect its condition. The examination revealed that the rod was unaffected by corrosion. A second inspection after nine months found evidence of rod string wear but no corrosion damage. The well has been in operation for 140 weeks (and counting), achieving a ten-fold improvement in the average run time before installing coated coiled rod.

The novelty of this approach is the application of an advanced materials science-based coating to extend rod string service life in corrosive environments through active protection. In addition, it requires no special handling or installation equipment, and the metallic material allows rod strings to be recycled (eliminating potential environmental and downstream damage risks associated with barrier coatings).

As supported by lab and field case study data, the results of deploying this method include increased production uptime, reduced workover frequencies and associated remediation costs, and lower overall LOE and lifting cost per barrel of oil produced.

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