Carbon Isotopic Characteristics of Hydrocarbons and CO2 of H2S-rich Natural Gases and Their Origin in Northeastern Sichuan Basin
川东北地区富含H2S天然气烃类与CO2碳同位素特征及其成因

Extensive investigation on geochemical characteristics,origin and source of H2S-rich natural gas in the northeastern Sichuan basin was processed and abundant documentation was accumulated in resent years.But a great attention has been paid and controversy existed all along on the origin and source of the natural gas in the northeastern Sichuan basin because of the specific geological environment and the complicated condition of natural gas formation and evolvement of the area.The correlations between the content of hydrogen sulphide and the components of hydrocarbons,the carbon isotopic compositions of methane,ethane and carbon dioxide indicate that the H2S-rich natural gases reservoired in the Feixianguan and Changxing Formations of the northeastern Sichuan basin are the product of oil cracking under the catalysis of sulphate and possibly derived from the Silurian source rocks;and that the generation of 13C-riched CO2 in the H2S-rich natural gas is related to the reduce of H2S content in natural gas and is the result of H2S corrosion on reservoir carbonate.