辽河油田西部凹陷沙三段沉积相及演化

Sedimentary facies and evolution of the third member of Shahejie Formation in West Depression of Liaohe basin

西部凹陷沙河街组三段沉积厚度很大,分布范围广,是深层储层重要组成部分。根据地球化学、化石组合及生态习性分析,沙三段沉积期处于暖湿气候的较深水还原湖泊环境。主体物源来自西侧,发育了一系列自西而东的扇三角洲砂体。根据沉积背景和岩心描述所建立的沉积层序,可确认这一沉积砂体的主要类型为浅水至较深水环境的水进型扇三角洲沉积,根据扇3角洲的岩性、沉积层序和形态可进一步划分为扇根、扇中和扇端3个亚相带。砂体发育主要受西侧物源控制,发育了多个扇三角洲体系。这些扇三角州砂体邻近生油洼陷,与烃源岩直接接触,有利于油气的优先富集,可形成一系列岩性-构造圈闭,不失为深层油气勘探的有利区带。

The lacustrine sandbodies in the 3^(rd) member of Shahejie Formation in West Depression are most important reservoirs for petroleum accumulation in the deeply buried sequences in Liaohe basin. The sedimentary environments of the 3^(rd) member of Shahejie Formation are dominantly deeper water lakes on the basis of organic geochemical marks and sedimentary features including fossils and trace fossils. Fandelta systems are recognized based on studies of sedimentary sequences and sandbody geometries. The overall finding upward sequence is characteristic of fandeltas that build out to the slope of a basin. The slope fandelta facies can be divided into proximal fan, middle fan and distal fan. Types, characteristic, areal distributions and vertical evolution of sedimentary facies of the fandelta systems in the 3^(rd) member of Shahejie Formation are described. The sedimentary supply from the western provinance produced the thick fandelta clastic wedges in the 3^(rd) member of Shahejie Formation. The sandbodies adjacent to the oil source area, and integrating with the structure and trapping conditions are important targets to find out oil and gas fields.