Generation causes of black powder in the east line of the gas supply pipeline from the Liaohe oilfield: Analysis and discussion

Abstract

A black powder material was discovered in the Liaohe oilfield that combusted when exposed to air. The black powder's phase and elemental compositions were investigated. The elemental valence was then determined using X-ray photoelectron spectroscopy (XPS) techniques. Immersion and electrochemical experiments were conducted in the laboratory using a high-pressure reactor to simulate the actual environment. The results revealed that the black powder's main components were iron oxide (Fe3O4), ferric polysulfides (Fe9S8), and sulfur and that the corrosion products of the immersion experiments were similar to the black powder examined on site. Fe9S8 and sulfur are responsible for the spontaneous combustion of the black powder. The corrosion rate of the X52 pipeline steel rose with increasing H2S levels, peaking at 14.15 mg/ m3. H2S, which came from underground gas storage, accounted for Fe9S8 and sulfur. Finally, filters and H2S removal devices should be installed to prevent black powder from spontaneously combusting.