Fretting behavior of hydrogenated nitrile rubber for sealing application of ultra-deep well

Abstract

With complex operating conditions and frequent pressure fluctuations in ultra-deep wells, the fretting wear caused by tubing string vibration inevitably affects the sealing performance of packer cartridge during well completion. In response to reveal the fretting damaged mechanism of cartridge rubber, an experimental and simulated investigation was carried out. Reciprocating fretting tests of hydrogenated nitrile rubber (HNBR) against casing steel (N-80) were conducted at 25 ℃, 65 ℃, 105 ℃, 145 ℃, and the displacement amplitude ranges from 0.25– 4 mm. The results indicate that the fretting state transfers from mixed fretting region (MFR) to partial slip region (PSR)/MFR with the increased temperature under lower displacement amplitude (0.25–1 mm), where the wear rate shows a decline with the increased temperature. It is mainly because that the increased sticky characteristics with temperature can decline the relative sliding. Under larger displacement amplitude (2–4 mm), the running condition transferred from slip region (SR) to MFR with the increased temperature eventually, where the interface is mainly dominated by sliding. The wear rate shows a dramatically increase with the increase in temperature due to the sharply decline of mechanical properties. The interfacial displacement variation obtained by finite element calculation are verified with the running condition of fretting map (RCFM). The established materials response fretting map for HNBR can gave an epoch-making reference on how to identifying the risk of sealing failure duo to tubing string vibration for a packer. This research also can highly enrich the fretting tribological theory in terms of high temperature.

Statement of originality

I write on behalf of myself and all co-authors to confirm that the results reported in the manuscript are original and neither the entire work, nor any of its parts have been previously published. The authors confirm that the article has not been submitted to peer review, nor has been accepted for publishing in another journal. The authors confirm that the research in their work is original, and that all the data given in the article are real and authentic. If necessary, the article can be recalled, and errors corrected.