川西坳陷中段中侏罗统沙溪庙组储层砂岩物源分析

On Material Source of Sandstone Reservoir of the Middle Jurassic Shaximiao Formation in West Sichuan Depression

川西坳陷中段中侏罗统沙溪庙组是重要的含气层。沙溪庙组储层砂岩以岩屑长石砂岩、长石岩屑砂岩为主,具有明显的沉积相分异。龙门山前和川西坳陷内砂岩的碎屑组分存在明显的差异,前者具有"贫长石,高石英"的特征,后者则"富长石、低石英",前者成分成熟度高于后者。根据研究区地层斜层理对沙溪庙组岩层古水流综合分析表明,古水流方向以北西→南东向为主,次为西→东向、北东→南西向;根据重矿物组合特征对沙溪庙组进行分析,可划分出3种组合方式,并能确认出相应的母岩类型。据此,认为研究区沙溪庙组储层砂岩具有多物源的特征,既有来自西部龙门山的物源,也有来自北部米仓山—大巴山的物源。

The Middle Jurassic Shaximiao Formation is an important gas reservoir in the middle west Sichuan depression.The Shaximiao Formation is mainly composed of lithic arkose and feldspathic lithic sandstone.The study indicates that the paleocurrent was NW-SE,secondly,W-E and NE-SW trending.The heavy mineral association may be divided into 3 groups.Comprehensive study indicates that material of the Shaximiao Formation was derived from Longmen Mountains in west and Micang and Daba Mountains in north.