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Objective The perforated corrosion sample of a natural gas gathering pipeline in Sichuan was studied to determine its failure reason. Methods The failure samples were tested by direct-reading spectrometer, optical microscope, X-ray diffractometer, scanning electron microscope and EDS, and the corrosion condition was analyzed. Results (1) A large number of corrosion pits can be seen on the inner surface of the pipeline. The matrix of the pipeline was ferrite plus pearlite, and the weld seam was acicular ferrite. Its metallurgical quality, chemical composition and mechanical properties meet the national standard requirements. (2) The corrosion products were FeS and FeCO3. (3) SRB existed in the gas field water. Conclusions The cause of pipeline perforation is the result of SRB, H2S, CO2 and other factors. [ABSTRACT FROM AUTHOR]

Objective Aiming at the special conditions in Sichuan tight gas field, the risk of microbiologically influenced corrosion (MIC) of gathering and transportation system during production was studied, and corrosion prevention measures were proposed on the basis of it. Methods The field produced water was used to monitor the concentration of bacteria. The impact of proportion of condensate oil and temperature on the growth of sulfate-reducing bacteria( SRB) and corrosion was investigated. Further, the application effect of corrosion inhibitor was evaluated and based on shale gas corrosion control experience, the detection measures of corrosion was re com mended according to experience about shale gas corrosion prevention. Results Bacteria extensively exists in the tight gas produced water. The growth of SRB and general corrosion of L245N steel were inhibited by condensate oil, but a great amount of bacteria were still adhered to the surface of coupons, which induced local corrosion. The pitting corrosion under high temperature of drainage period was more severe. Two types of corrosion inhibitors were evaluated which can inhibit pitting corrosion with sterilization rate above 99%. Conclusions There exists some microbial corrosion risk for tight gas gathering and transportation pipelines. It is necess,1ry to combine the corrosion inhibit0r injection and internal corrosion monitoring of weak parts of pipelines to prevent corrosion. [ABSTRACT FROM AUTHOR]