Gas lift, utilizing the injection of high-pressure gas via well production annuli and into the production bore through mandrels or valves, is a common artificial lift method in oil wells. Unexpected corrosion located in the annuli below the gas-lift valve was observed on several well completions and led to an investigation of its causes and deployment of alternative mitigation measures. The aggressiveness of the corrosion seen is not in line with industry experiences and prompted a need to better understand contributory factors. Unlike the often traditionally held belief that corrosion should be limited to the interface of the injected gas and packer fluid column; corrosion was seen to extend far beyond this area deep into the wells.

Investigations consisted of reviewing historical packer fluid treatments and well operating conditions, literature surveys, and metallurgical and scale analysis of the retrieved production tubing. In addition, microbiological analysis was undertaken to establish if a microbial influence was present. To substantiate findings a review of the Company's gas lifted well stock and reported corrosion cases was undertaken.

This paper will describe that CO2 + H2S corrosion was identified as the main degradation mechanism and that the presence of glycol in the packer fluids exerted a crucial detrimental factor. A microbial influence could not be ruled out.

Chemical treatment test methods developed to establish the longevity of protection to be expected, and initial results from them, are described.


Injection of hydrocarbon gas is a common practice to enhance production rates from multiphase wells in the Oil and Gas industry. The gas used is normally dehydrated by a combination of compression and chemical treatments to reach a given dew point specification. The dry non-corrosive gas is injected to the production annulus and enters the production bore via a gas lift valve (GLV) located on the production tubing above the production packer.

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