KL油田沙三上亚段沉积特征及砂体叠置类型

Sedimentary characteristics and superimposition types of sand bodies in the E_(2)s_(3)^(U) of KL Oilfield

渤海湾盆地莱州湾凹陷古近系沙三上亚段发育辫状河三角洲前缘沉积,是KL油田的主力含油层段。文中综合利用钻井、测录井、岩屑和岩心等资料,建立了KL油田沙三上亚段Ⅲ油组井间砂体沉积相剖面,结合层序地层学原理,详细分析了KL油田沙三上亚段Ⅲ油组辫状河三角洲前缘砂体的叠置类型及控制因素。研究结果表明:Ⅲ油组辫状河三角洲前缘主要发育水下分流河道和河口坝砂体,整体以进积为特征,内部发育水下分流河道加积沉积;水下分流河道自下而上逐渐向湖盆推进,河口坝范围逐渐收缩,至Ⅲ油组1小层和2小层,研究区范围内只发育水下分流河道砂体;根据水下分流河道和河口坝的接触关系,将砂体叠置类型划分为三大类、12个小类。砂体叠置类型主要受湖平面变化、沉积物供给变化和沉积相类型所控制。该研究成果可为油田后期加密调整和剩余油潜力分析提供借鉴。

The braided river delta front deposits developed in the upper 3 rd Member of Eogene Shahejie Formation(E_(2)s_(3)^(U)) in Laizhou Bay Sag, Bohai Bay Basin are the main oil-bearing intervals in KL Oilfield. Using the drilling, logging, rock debris and core data comprehensively, the sedimentary facies section of inter-well of the Ⅲ oil group in the E_(2)s_(3)^(U) of KL Oilfield is built. Combined with the principle of sequence stratigraphy, the superimposition types and controlling factors of braided river delta sand bodies of the Ⅲ oil group in the E_(2)s_(3)^(U) of KL Oilfield are analyzed in detail. The results show that the braided river delta front sand bodies of the Ⅲ oil group are mainly underwater distributary channel and mouth bar sandstones, which is characterized by the progradation and develops unnderwater distributary channel aggradation deposits internally;from bottom to up, underwater distributary channel gradually advanced toward the lake basin, and the mouth bar gradually shrink to the 1 st and 2 nd layers of the Ⅲ oil group, only the underwater distributary channel sandstone was developed within the study area;according to the contact relationship between the underwater distributary channel and the mouth bar, the sandstone superimposition relationship is divided into 3 categories and 12 subcategories. The sandstone superimposition relationships were mainly controlled by lake level changes, sediment supply changes,and sedimentary facies types. The research results can provide reference for the later stage of the oilfield′s infill adjustment and reamining oil potential analysis.