Abstract: Based on the data of drilling,logging,core description,thin section identification and core experimental analysis,as well as the sedimentary characteristics of modern oceans,the paper investigates the mineral content distribution,lithofacies characteristics and sedimentary types of organic-rich shale in the Ordovician Wufeng Formation and Silurian Longmaxi Formation in Luzhou area,southern Sichuan Basin,divides the types of the sedimentary microfacies and microrelief of deep-water shelf,and then analyzes the influences of the both on reservoirs.The results are as follows.(1) The terrigenous clasts of organic-rich shale in Wufeng Formation and Longmaxi Formation in the study area are originated from the submerged highland in the north of the central Sichuan Basin,and their lithofacies are mainly shown as siliceous shale,clay-bearing siliceous shale and mixed shale.(2) The sedimentary types of target strata are dominated by hemipelagic sediment and turbidity sediment.(3) The sedimentary microfacies in deep-water shelf can be subdivided into 6 types,i.e.,calcareous shelf,calcareous-siliceous shelf,calcareous-siliceous-argillaceous mixed shelf,siliceous-argillaceous shelf,siliceous shelf and argillaceous-rich fan.Among them,siliceous shelf,siliceous-argillaceous shelf and calcareous-siliceous-argillaceous mixed shelf are mainly developed in the study area.Sedimentary microrelief can be subdivided into five types,i.e.,shelf highland,shelf slope,shelf gully,shelf mound and shelf plain.Among them,shelf plain and shelf slope are mainly developed in the study area.(4) Sedimentary microfacies in deep-water shelf control the reservoir quality of organic-rich shale by controlling the reservoir capacity.Calcareous-siliceous-argillaceous mixed shelf and siliceous shelf have the best reservoir quality.Sedimentary microrelief exerts influence on the quality of shale reservoir by controlling the thickness of organic-rich shale,and the reservoir in shelf plain is the thickest.(5) In the deep-water shelf environment,with the increase of sedimentary water depth,the sedimentary microrelief is evolved from shelf highland to shelf plain (or shelf mound) through shelf slope (or shelf gully or shelf mound),and the sedimentary microfacies are evolved from calcareous-siliceous shelf to silicon-argillaceous shelf (or argillaceous-rich fan) through calcareous-siliceous-argillaceous mixed shelf,and finally evolve into siliceous shelf.The sedimentary microfacies model of deep-water shelf can provide scientific support for reservoir evaluation and prediction of deep organic-rich shale.(6) The organic-rich shale in deep-water shelf is deposited at the edge of the shelf,and its sedimentary depth can exceed 200 m.

Key words: organic-rich shale, deep-water shelf, sedimentary microfacies, sedimentary microrelief, Wufeng Formation, Longmaxi Formation

摘要： 根据钻井、测井、岩心描述、岩石薄片鉴定和岩心实验分析资料,结合现代海洋的沉积特征,研究了四川盆地南部泸州地区奥陶系五峰组-志留系龙马溪组富有机质页岩中的矿物含量分布、岩相特征和沉积类型,划分了深水陆棚的沉积微相和微地貌,分析了深水陆棚沉积微相-微地貌对储层的影响。研究结果表明:①研究区五峰组-龙马溪组富有机质页岩的陆源碎屑来自北侧川中水下高地,其岩相主要包括硅质页岩、含黏土硅质页岩和混合页岩3种类型。②目的层的沉积类型以半远洋沉积和浊流沉积为主。③深水陆棚沉积微相可细分为钙质陆棚、钙-硅质陆棚、钙-硅-泥混合陆棚、硅-泥质陆棚、硅质陆棚和富泥扇6种类型,在研究区以发育硅质陆棚、硅-泥质陆棚和钙-硅-泥混合陆棚为主;沉积微地貌可细分为陆棚高地、陆棚斜坡、陆棚沟、陆棚丘和陆棚平原5种类型,在研究区以发育陆棚平原和陆棚斜坡为主。④深水陆棚沉积微相通过控制储集能力而控制富有机质页岩的储层质量,钙-硅-泥混合陆棚和硅质陆棚具有最好的储层品质;沉积微地貌通过控制富有机质页岩的厚度从而影响页岩储层质量,其中以陆棚平原中储层厚度最大。⑤在深水陆棚环境,随着沉积水体加深,沉积微地貌的演化由陆棚高地经陆棚斜坡(陆棚沟、陆棚丘)过渡到陆棚平原(陆棚丘),沉积微相的演化由钙-硅质陆棚经钙-硅-泥混合陆棚过渡到硅-泥质陆棚(富泥扇),并最终演化为硅质陆棚。深水陆棚沉积微相模式可为深层富有机质页岩的储层评价与预测提供科学支撑。⑥深水陆棚富有机质页岩沉积在陆棚边缘,其沉积水深可超过200 m。

关键词: 富有机质页岩, 深水陆棚, 沉积微相, 沉积微地貌, 五峰组, 龙马溪组