51312-01156-Embrittlement of MP35N (UNS R30035) Springs in Simulated Downhole Production and Acid Treatment Envi

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Product Number: 51312-01156-SG

ISBN: 01156 2012 CP

Author: Karthik Krishnan

Publication Date: 2012

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Testing of MP35N springs was carried out in various downhole production and acid treatment environments containing H2S to determine the susceptibility to environmental cracking. The aim was to simulate the functioning of torsion springs used in the flapper seat of a Sub-Surface Safety Valve (SSSV) as part of a completion string in various well conditions. The MP35N springs were held using an Alloy 825 fixture in a position equivalent to a flapper seat having a SSSV in the open condition. The torsion spring is under maximum stress during the SSSV open condition; hence corrosion testing was conducted simulating this condition. Distinct environments were designed for the corrosion tests to simulate different scenarios. These include corrosion tests simulating actual well conditions in production of hydrocarbons and acid flow back conditions during stimulation. Additionally testing was carried out to see the effect of galvanic coupling and a possible way to induce hydrogen embrittlement of MP35N spring. The results of testing in the various environments revealed that MP35N used as a torsion spring is very resistant to production environments containing H2S. MP35N used as a torsion spring also shows good corrosion resistance in typical acidizing conditions during stimulation but can be susceptible to cracking during acid treatment under very specific conditions.