川西北地区须家河组三段致密砂砾岩沉积特征及模式

Sedimentological Characteristics and Sedimentary Model of Massive in Northwest Sichuan

川西北部地区须家河组三段砂砾岩是致密气上产的现实领域,通过野外踏勘、岩心精细观察描述和微量元素测试分析,结合前人对川中-川西地区须家河组研究成果和区域地质背景,开展川西北地区须三段沉积相标志、沉积相类型及特征、瞬时沉积模式等研究。结果表明,川西北部地区须三段发育湿地扇、辫状河和辫状三角洲沉积,以辫状三角洲沉积为主。湿地扇沉积局限分布在盆缘近物源区,辫状河道和三角洲分流河道以砾石和砂质沉积为特征,这两类沉积体是研究区储层主要的砂体类型。从山前到盆内依次发育湿地扇→辫状河→辫状三角洲的沉积模式。

Sedimentary facies marker,sedimentary facies type and instantaneous deposition pattern of the 3 th Member of the Xujiahe Formation in northwest Sichuan are studied.The results indicate that wetland fan,and braided river,especially,braided river delta deposits were developed in the 3 th Member of the Xujiahe Formation in northwest Sichuan.The wetland fan deposits were confined to the source area near the basin margin.The braided channels and deltaic distributary channels were characterized by gravel and sandy deposits which were the main sand body types of the reservoir in the studied area.From the piedmont to the basin center,the wetland fan,braided river and braided delta deposits were developed successively.