InnerArmor for Coating Crossover Subs

In most wells today, natural pressure is inadequate to lift oil to the surface of the well, and artificial lift is utilized to increase flows. The most common artificial lift method is beam pumping, which utilizes a sucker rod pump to lift oil from the well. The reciprocating motion of the sucker rod can create significant wear sliding against internal walls of the tubing and other supporting components. Depending on the environment, the lifting equipment may be subjected to very sour flows (i.e., high H₂S content), carbon dioxide, heavy sand, and salt water. To operate in these conditions, oil companies must constantly maintain and replace worn components. In most cases this maintenance requires halting production to replace the worn component(s).

Problem

An oil company implemented sand control technology and utilized a crossover sub to connect from traditional tubing to smaller diameter pipe near the bottom of the well. In these wells, CO₂ and sand were present which created corrosion and wear issues. Uncoated crossovers had a short life span and experienced corrosion from the CO₂ and wear from the reciprocating motion of the sucker rod. When the crossover corroded and failed, the well required a workover to replace the crossover and other elements in the production string. The customer incurred costs for pulling tubing to replace the failed crossover as well as the lost revenues from not producing oil.

Solution

InnerArmor® coatings were applied to the internal surfaces of the crossover to protect against sucker rod wear and corrosion. The coatings offer a protective layer for the application environment, which included sand, carbon dioxide, and water. Key features of InnerArmor coatings include:

• Greater hardness – Typically five times harder than carbon steel, InnerArmor significantly extends the surface life by reducing sucker rod wear and sand erosion on the crossover surface.
• Corrosion resistance – With an inert surface InnerArmor coatings protect the surface from chlorides, carbon dioxide, and other corrosive elements.
• Improved flow and fouling resistance – A thin, near frictionless surface ensures consistent flow and resistance to fouling buildup on the internal surface.

Benefits

InnerArmor coatings provide unique levels of protection to prevent corrosion and wear. Since the customer standardized on InnerArmor coatings, the crossover is no longer a source of well failures, and workovers due to crossover failures have been elimnated. Previously, the cost of downtime and lost production could typically exceed $30,000, significantly more for deeper wells. The InnerArmor coating easily justifies its small additional cost by eliminating a cause of many past failures. InnerArmor coatings are also in production on the internal surfaces of many other downhole parts that require a coating that protects against corrosion and wear.