Cailiao Baohu (Feb 2022)
Study on Corrosion Law of Annular Casing of the Production Wells in Acid X Gas Field
Abstract
In the production process of acid X gas field, the phenomenon of H2S and sulfide in annular pressure samples and annulus gas/liquid sample appeared in several wells.The sulphur resistant production casing of 110SS was at serious risk of corrosion.In order to obtain the corrosion law of sulphur resistant casing in the real wellbore environment, the corrosion evaluation experiment of sulphur resistant casing 110SS in gas phase and polluted annular protective liquid and the galvanic corrosion evaluation experiment of the connection between sulphur resistant casing and nickel-base alloy casing in polluted annular protective liquid were carried out by adopting corrosion hanging sheet method in high temperature and high pressure reactor.The corrosion surface and corrosion products of the samples were observed and analyzed by metallographic microscope, SEM and EDS.Experimental result showed that the corrosion rate of sulfur resistant casing in liquid phase was very low, and temperature had no significant effect on the corrosion rate.When the temperature was higher than 100 ℃, the corrosion of sulfur resistant casing in the gas phase became very serious, and the corrosion rate was as high as 0.947 3 mm/a.Severe galvanic corrosion occurred in the liquid phase at the connection between sulfur resistant casing and nickel-base alloy casing.Large corrosion pits appeared on the surface of sulfur resistant casing samples, and the corrosion rate was greater than 0.076 mm/a allowed by the engineering design.The obtained corrosion law of sulfur resistance casing in the real wellbore environment would provide an accurate reference for the later formulation of corrosion control measures, prediction of casing residual strength and safety evaluation of wellbore.
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