贵州早石炭世岩相古地理演化及页岩气成藏特征

Lithofacies and paleogeography evolution and characteristics of shale gas accumulation in Lower Carboniferous,Guizhou,China

根据野外剖面层序地层研究和室内资料分析,结合最新钻井资料、区域地质调查资料等,并与国内外典型页岩气特征参数及聚集条件对比,综合研究贵州下石炭统页岩气富集条件、优选有利地区。贵州下石炭统发育4个层序,以台地相石灰岩为主,夹潮坪沼泽潟湖相白云岩和泥页岩,惠水、长顺以及六盘水等地区下石炭统旧司组(打屋坝组,第2层序)页岩、泥岩较发育。从页岩、泥岩的分布、厚度、有机质丰度、有机质类型、有机质热演化程度等特征,并与美国Barnett页岩等五大含气页岩主要评价参数以及涪陵焦石坝页岩气的分布、产出状态(游离气体积分数>50%)等对比,认为黔南、黔西南地区旧司组具有页岩气聚集发育的条件,具有很好的勘探前景。其中,黔南最有利的地区是紫云—惠水一带,黔西南最有利的地区位于威宁—水城一带。该区页岩气应重视保存条件的研究,同时应重视游离气、夹层气的贡献。

Study of shale gas accumulation conditions and selection of favorable area in Lower Carboniferous of Guizhou Province are carried out on the bases of research on field-profile sequence stratigraphy and analysis of laboratory data, combined with the latest drilling data and regional geological survey information. Lower Carboniferous Series in Guizhou can be divided into 4 sequences with dominate limestone interbedded with dolomite and shale. Shale and mudstone develop well in Jiusi Formation （Dawuba Formation, the second sequence） in Huishui, Changshun and Liupanshui areas. Comparison of five evaluation parameters of Barnett shale in United States with shale gas distribution and output status （volume fraction of free gas is ~50~） of Fuling shale gas in China, in terms of thickness and distribution of shale, organic carbon abundance, organic carbon type and thermal evolution analysis, it considers that the Jiusi Formation of Lower Carboniferous shale possesses good accumulation condition with very large exploration prospects in southern and southwestern Guizhou. The favorable areas in southern Guizhou mainly distribute in the Ziyun- Huishui area and the favorable areas in southwestern Guizhou mainly distribute in the Weining- Shuicheng area. Attention should be paid to the study of preservation conditions of shale gas and the contribution of free gas and intercalated bedding gas in shale formation.