基于浅水三角洲沉积的供源差异与砂体分布空间配置关系--以松辽盆地长垣西部葡萄花油层为例

Relationship between source difference and spatial distribution of sand bodies of shallow-water delta:an instance of Putaohua Oil Layer in the Western Changyuan,Songliao Basin

为明确松辽盆地长垣西部葡萄花油层前缘河道砂体受不同因素影响的发育特征及其差异,根据测井、岩心等资料,结合多种矿物含量分析交汇,定量识别长垣西部地区受水动力条件、供源成分及方向影响的不同物源交汇范围,根据相对湖平面变化和物源供给等方面的耦合关系,以水下分流河道砂体为骨架,分析不同供源方向沉积成因的砂体岩相组合及发育特征差异。结果表明:松辽盆地长垣西部葡萄花油层发育时期受北部齐齐哈尔水系与西部英台水系两大水系影响,发育两类沉积特征明显不同的浅水三角洲沉积体系,即东北部物源控制的长源缓坡大型浅水三角洲与西部物源控制的短轴陡坡正常三角洲两个沉积体系。不同沉积体系交汇区三角洲前缘砂体可分为曲流型水下分流河道砂体与浅水型水下分流河道砂体两种类型。三角洲水下交汇区自下而上沉积物单层厚度增大,平面上形成大前缘、小湖泊的沉积特征;不同期次、来自不同三角洲的水动力大小、展布形态不同,致使砂体在空间上产生交切、叠置,形成厚度小、分布多、层数多的特点,可成为有利的油气储层。该结果可为研究缓坡浅水三角洲前缘砂体体系提供指导。

In order to clarify the development characteristics and differences of channel sandbodies in the front of Putaohua Reservoir in the west of Changyuan,Songliao Basin,based on logging and core data,combined with the analysis and intersection of various mineral elements,the intersection range of different provenances affected by hydrodynamic conditions,source composition and direction in the western region of Changyuan are quantitatively identified.The results show that the deposition of Putaohua Oil Layers are affected by Qiqihar water system in the north and Yingtai water system in the west.Therefore,there are two types of shallow water delta depositional systems with obviously different sedimentary characteristics in Western Changyuan.The study areas controlled by different provenances were quantitatively identified,and two sedimentary systems were formed:the large shallow water delta with long source and gentle slope under the control of northeast provenances,and the normal delta with short axis and steep slope under the control of west provenances.The delta front sand bodies in the intersection area of different sedimentary systems can be divided into two types:meandering subaqueous distributary channel and shallow subaqueous distributary channel sand bodies.As a favorable place for sediment unloading,the underwater intersection area of delta increases the thickness of single layer of sediments from bottom to top,and the sedimentary characteristics of large front and small lakes are formed on the plane.Different deltas have different hydrodynamic and distribution forms,which result in the superposition of sand bodies in space,forming the characteristics of small thickness,multiple distribution and multiple layers,which can become favorable oil and gas reservoirs.The research results can provide a reference for the study of sand body system of shallow water delta front on gentle slope shallow water delta.