黄骅坳陷大港探区高含H_2S天然气地球化学特征及成因

渤海湾盆地继冀中坳陷晋县凹陷发现H_2S气藏后,在黄骅坳陷大港探区又发现了高含H_2S气藏,在煤成气气藏中发现如此高含量的H_2S和CO_2在国内还属首次,酸性气体的成因也引起国内学者的关注。通过气、岩有机地球化学参数的对比,认为该区高含量H_2S归因于TSR反应,揭示了煤成气区同样可以发生TSR,丰富了过去只在海相原油裂解气区发生TSR的地质认识;高含量有机或有机-无机混合的CO_2除了与碳酸盐岩的热变质、TSR有关外,与烃类气体属于煤成气有很大的关系。黄骅坳陷大港探区H_2S的富集受储层中的硫源丰富程度和地层温度的控制,高含H_2S天然气主要分布在石炭系—二叠系覆盖且埋深较大的中南部地区,如埕海、泊古—乌马营—王官屯等地区。研究成果对该区高含酸性天然气形成机制以及天然气下一步勘探部署工作都具有积极指导意义。

Geochemical characteristics and genesis of high-H2S natural gas in the Dagang exploration area,Huanghua depression

After the discovery of H₂S gas reservoir in Jinxian Depression, Jizhong Sag, Bohai Bay Basin, high-H₂S gas reservoir was discovered in the Dagang exploration area, Huanghua sag. Such high H₂S and CO₂ contents have been first found in coal-formed gas reservoir in China, and the genesis of acid gas has attracted attentions of domestic scholars. Through comparing the organic geochemistry parameters of gas and rock, it is believed that high content of H₂S in the area is the product of thermochemical sulphate reduction(TSR), which reveals that TSR can also occur in the coal-formed gas area and enriches the previous geological recognition that TSR only occurs in the marine crude oil cracking gas area; high content of organic-inorganic CO₂ is related to thermal metamorphism of carbonate rock and TSR, and is also strongly associated with coal-formed hydrocarbon gas. The enrichment of H₂S in the Dagang exploration area, Huanghua Sag is controlled by formation temperature and the enrichment degree of sulfur source in reservoir. High-H₂S natural gas is mainly distributed in the south central region covered by Carboniferous-Permian strata with a relatively great burial depth, such as Chenghai, Bogu-Wumaying-Wangguantun, and etc. The research results have a positive guiding significance to discover the formation mechanism of high acidic natural gas and carry out the next exploration deployment of natural gas.