安徽中南部大隆组沉积环境及油气潜力特征

Sedimentary environment and hydrocarbon potential of Dalong Formation in central and southern Anhui Province

晚二叠世下扬子地区沉积了一套以硅质岩、硅质页岩、碳质页岩为主的“黑色岩系”,其分布广泛,被认为具有良好的油气勘探开发前景。文章基于实测剖面和有机地化测试资料探究安徽中南部大隆组的沉积环境及油气潜力。结果表明:大隆组在巢南、安庆—铜陵、泾县、宁国等沉积凹陷周缘厚度可达40~70 m,并向南北两侧逐步减薄;大隆组表现为一套较为完整的海侵—海退沉积序列,早期形成深水盆地相沉积,晚期则转变为潜水陆棚相沉积,区域上自西北部至东南部依次为深水盆地相、浅水陆棚相和开阔碳酸盐岩台地相沉积组合。大隆组的总有机碳(total organic carbon,TOC)质量分数为1.46%~15.80%,R o值高于2.00%,属于优质烃源岩,热演化处于过成熟早期阶段,沉积凹陷边缘区是页岩气勘探需重点调查对象。

A set of“black rock series”mainly composed of siliceous rocks,siliceous shales and carbonaceous shales was deposited in the Lower Yangtze region of the Late Permian,which is widely distributed and is considered to have a good prospect of hydrocarbon exploration and development.Based on measured profiles and organic geochemical data,this paper explores the sedimentary environment and hydrocarbon potential of Dalong Formation in central and southern Anhui Province.The results show that the thickness of the Dalong Formation can reach 40-70 m at the periphery of the Chaonan,Anqing-Tongling,Jingxian and Ningguo sedimentary depressions,and it gradually decreases to the north and south.The Dalong Formation is a relatively complete transgressive-regressive sedimentary sequence,which formed deep basin facies in the early period,and then transformed into submersible shelf facies in the late period.The region is successively composed of deep basin facies,shallow shelf facies and open carbonate platform facies sedimentary assemblages from northwest to southeast.The mass fraction of total organic carbon(TOC)of Dalong Formation is 1.46%-15.80%,and the R o value is higher than 2.00%,which belongs to high-quality source rocks,and the thermal evolution is in the early stage of over-maturity.The marginal area of sedimentary depression is the key investigation object for shale gas exploration.