Two leaks were discovered in a section of 4.0-inch diameter mild steel pipe used for disposal of produced water from coal-seam gas wells. These leaks were the result of pitting-type corrosion characterized by smooth walled, overlapping, cup-like, hemispherical depressions inside a main pit of which some pits contained nodules. An examination of one of these nodules revealed the mineral siderite (ferrous carbonate) along with significant amounts of sodium, manganese and iron but no sulfur, A scale surrounding these pits contained calcareous minerals in addition to magnetite. The pits were located in the proximity of circumferential welds but many were distal to the heat-affected-zone (HAZ). Significant concentrations...
Keywords: microbially influenced corrosion, coal seam, nodules, pitting, welds, siderite, metal-reducers, iron-oxidizers