四川类前陆盆地中西部须家河组储层特征

Reservoir Characteristics of the Xujiahe Formation in Central-west Sichuan Analogous Foreland Basin

四川类前陆盆地上三叠统须家河组储层在岩石学上具有低成分成熟度、低胶结物含量和结构成熟度中等特征,岩性在平面上具有一定的规律性,在川西北地区以岩屑砂岩为主,川西中部地区为岩屑砂岩与长石砂岩混合区,川西南地区以岩屑长石砂岩为主,川中前陆隆起为长石岩屑与岩屑石英砂岩混合区。储层总体物性较差,属低孔低渗和特低孔特低渗储层,局部发育有少量中孔低渗储层。由于盆地内逆冲推覆带、前渊坳陷带、前陆斜坡带和前陆隆起带的沉积、成岩以及构造作用的差异性。决定了储层孔隙类型的分带性,龙门山逆冲推覆带储层类型以裂缝型为主,另可见少量的溶蚀孔和原生粒间孔;前渊坳陷带储层类型为裂缝—次生溶孔型,以次生溶蚀孔隙为主,原生孔隙基本消失;前陆斜坡带储层类型以次生溶孔及原生粒间孔为主;前陆隆起带以溶蚀扩大孔和原生孔组成的混合孔为主,储层发育受沉积、成岩和构造破裂作用的控制。

Reservoirs of the upper Triassic Xujiahe Formation has characteristics of low compositional maturity,low cement content and medium maturity in Sichuan analogous foreland basin.Lithology is regularly distributed in plane,dominated by lithic sandstone in the northwest region.lithic sandstone and feldspathic sandstone mixed in central west region,lithic feldspathic sandstones in southwest region,feldspathic lithic and lithic quartz sandstone mixed in central-south region.Reservoir has poor physical properties in general,which are mainly low porosity and permeability reservoir.Only a few reservoirs with middle porosity and low permeability develop in some regions.Because of the sedimentation,diagenesis and tectonic difference in thrust belt,foredeep depression zone,foreland slope and foreland uplift,of the reservoir porosity has zoning characteristics.Reservoir space in Longmen Mountain thrust belt are mainly fracture with small amount of emposieu and original intergranular pore.The pore type in foredeep depression zone is fracture-secondary dissolved pore,dominated by secondary dissolved pore with little primary pore.In foreland slope,the pore type is mainly secondary dissolved pore and primary pore.While in foreland uplift,the pore is mainly dissolved pore and primary pore.The development of reservoirs is controlled by deposition,diagenesis and tectonic disruption.