Acetate, DIC and delta C-13(DIC) evidence for acetoclastic methanogenesis in Songliao Basin, NE China

摘要

Extracted waters of thirty eight (38) shale samples from Songliao Basin, NE China have been determined their acetate and dissolved inorganic carbon (DIC) concentrations and carbon isotopic compositions of DIC. Wide range variations have been observed in the geochemical data, which seem not controlled by organic richness and burial depth. Systematically low acetate concentrations and low DIC content, coupled with relatively C-13 enriched DIC in Pu-Ao area and west slope than these from north and east areas of the basin suggest different degree of acetoclastic methanogenesis. Moderate methanogenesis in Pu-Ao and west slope is in consistent with biogenic gas discovery in these areas. Methanogenesis in north and east is inhibited due to the loss of pore space and undeveloped fracture system, which is also supported by none encountered biogenic gas. However, overall methanogenesis in these fine grained shales is very limited and current ongoing methanogenesis is doubtful. (C) 2015 Elsevier B.V. All rights reserved.