四川盆地五峰组—龙马溪组页岩岩相及储集空间特征

Characteristics of shale lithofacies and reservoir space of the Wufeng–Longmaxi Formation,Sichuan Basin

以四川盆地东南缘奥陶纪末至志留纪初的深水沉积五峰组—龙马溪组页岩为研究对象,在野外剖面考察和岩石薄片鉴定的基础上,通过电子显微镜观察、矿物含量分析等,剖析五峰组—龙马溪组页岩的矿物学特征、岩相特征和储集空间类型,并讨论页岩储集性能的控制因素。研究区页岩矿物成分以碎屑石英和黏土矿物为主,含有长石、方解石、白云石、黄铁矿等;存在炭质页岩、硅质页岩、粉砂质页岩、钙质页岩和普通页岩等5种岩相;发育构造张裂缝、构造剪裂缝、层间页理缝、黄铁矿孔隙、黏土矿物晶间微孔及微裂缝、石英颗粒边缘微裂缝和有机质孔隙等7种页岩气储集空间。储集空间发育主要受矿物成分、岩相类型、有机碳含量、有机质成熟度以及成岩作用的影响。

Based on observation of the outcrops and cores of the Late Ordovician to the Early Silurian Wufeng Longmaxi shale,developed in the deep water shelf environment,in the southeast of the Sichuan Basin,the mineralogical features,lithofacies characteristics and reservoir space types were studied and the factors affecting reservoir capacity were analyzed by observation through eletron microscope and analysis of mineral contant.The mineral composition is dominantly clastic quartz and clay minerals,with feldspar,calcite,dolomite,pyrite and so on.Five lithofacies,i.e.carbonaceous shale,siliceous shale,silty shale,calcareous shale and ordinary shale,were identified in the Wufeng–Longmaxi shale.Seven types of reservoir space,including structural tension fracture,structural shear fracture,interlayer lamellation fracture,pyrite pore,the inter-crystal micro-pore and micro-crack in clay mineral,the edge micro-crack around quartz grains and organic matter pore,were found in the Wufeng–Longmaxi shale.The development of reservoir space is strongly controlled by the mineral composition,lithofacies,organic carbon content,organic matter maturity and diagenesis.