Full-Scale Testing of Grooved Polymer Liners for Downhole Applications Available to Purchase

Corrosion control in downhole casing and tubing is a major concern for operators using carbon dioxide (CO₂) in enhanced oil recovery schemes. A potential life-cycle cost advantage can be realized by utilizing polymeric liners in these applications. Conventional liners, however, have been shown to be problematic due to their propensity to collapse when the bore is rapidly de-pressurized. A novel solution to this problem has been the development of a grooved liner system. Grooved liners facilitate the venting of gases which permeate through the liner wall, thereby reducing the chance of liner buckling and collapse during blowdown. The objective of the current study was to verify the performance of a grooved liner system subjected to a supercritical CO₂ environment. Full-scale tests were performed on liners made from three candidate thermoplastic polymers including high density polyethylene, cross-linked polyethylene and modified nylon. The test sequence consisted of a series of repeated pressurization cycles with extended hold times to allow for steady-state gas permeation. In general, the tests on all grooved liner specimens were successful in that no liners collapsed during rapid de­pressurization of the bore. However, the grooved cross-linked polyethylene liner was clearly the most suitable candidate for the supercritical CO₂ environment due to its ability to properly collect and vent the permeated gas products over the entire test period. In addition to the experimental results, a finite element model of the permeation behavior in the grooved liner system was developed. The predicted permeation rates of CO₂ were found to be similar to those measured in the experiments.