黄河口凹陷A区古近系沙河街组三段沉积相

Sedimentary facies of the Member 3 of Shahejie Formation of Paleogene in Area A of Huanghekou Sag

通过岩心观察描述和沉积相分析,结合地震、测井、录井、分析化验资料综合分析结果表明:黄河口凹陷A区沙河街组三段发育扇三角洲相、湖底扇相和湖泊相。沙三段下亚段沉积相特征在沙三段沉积时期具有代表性。沙三段下亚段主要储层沉积相类型为扇三角洲相和湖底扇相。扇三角洲相划分为扇三角洲平原、扇三角洲前缘和前扇三角洲3个亚相。扇三角洲平原亚相由泥石流和水道沉积组成。扇三角洲前缘亚相由近端坝和远端坝沉积组成。湖底扇相可分为内扇、中扇和外扇3个亚相。内扇主要由滑塌堆积和碎屑流沉积组成,中扇主要由碎屑流和浊流沉积组成,外扇主要由浊流沉积组成。沙三段下亚段沉积时期,沉积相的平面展布具有一定的规律性,表现为:靠近南部盆缘断裂发育扇三角洲相,向湖方向发育湖底扇相,向北逐渐过渡为湖泊相。沙三段下亚段沉积时期,盆地明显为南陡北缓的箕状断陷湖盆,陡坡带活动盆缘断裂控制了扇三角洲相的分布。

Three types of sedimentary facies including fan-delta, sublacustrine fan and lacustrine facies were developed in the Member 3 of Shahejie Formation in the Area A of Huanghekou Sag, based on the studies of cores, well logs, seismic analyses and the analyses of sedimentary facies. The characteristics of sedimentary facies of the Member 3 of Shahejie Formation are typical. In the lower part of Member 3 of Shahejie Formation, the main reservoir types are fan-delta and sublacustrine fan facies. Fan-delta can be divided into three kinds of subfacies： fan delta plain, fan delta front and prodelta. The fan delta plain is mainly composed of mud debris flow and channel sediments. Fan delta front includes proximal and distal bar deposits. Sublacustrine fan facies includes inner fan, middle fan and outer fan subfacies. The inner fan is mainly composed of slumping sediments and debris flow. The middle fan is dominated by debris flow and turbidity flow sediments. The outer fan is mainly composed of turbidity sediments. The distribution features of sedimentary facies of the lower part of Member 3 of Shahejie Formation are studied. Fan delta is located along the southern basin-margin faulted belt. Sublacustrine fan is located in the lake area. The lacustrine facies is distributed in other areas. During the sedimentary period of the lower part of Member 3 of Shahejie Formation, the basin was a graben rifted lacustrine basin and the active basin-margin faulted belt controlled the distribution of fan delta facies.