New Corrosion Inhibitor Evaluation Approach for Highly Sour Service Conditions

Sour gas production in highly sour conditions has the potential to exhibit severe corrosion in wells and flowlines within gathering systems.   Often, this type of production occurs in high risk, high consequence geographical locations.  Consequently, integrity management programs for these gathering systems have to be thorough and well implemented in their scope.  Inhibitor qualification, as part of an integrity management program and the inhibitor development process has to include a severe enough test to adequately differentiate inhibitors.  For highly sour conditions, the test needs to evaluate localized corrosion whether it is due to pitting or underdeposit conditions.  This paper discusses the new sour gas test method development and its use in evaluation of localized corrosion under highly sour conditions using a HTHP autoclave set up to simulate low shear stress conditions.  Inhibitors were evaluated in terms of maximum and average pit depth penetration via statistical analysis of pits depth/size distribution using automated, high resolution Vertical Scanning Interferometer (VSI) in conjunction with the Localized Corrosion Monitoring (LCM^TM).  An example of an inhibitor evaluation using the new test methodology was presented.