浅水湖泊三角洲平原分流河道类型与叠置模式

浅水湖泊三角洲在中国许多陆相盆地中广泛发育,其中分流河道是三角洲平原最主要的砂体类型,它们大多呈现河道频繁改道、多级交叉及叠置的特点,往往形成极为复杂的地下储集层相互叠置的分布格局。基于松辽盆地浅水三角洲平原分流河道砂体的测井曲线特征,系统总结了浅水三角洲平原的分流河道河道类型与砂体叠置模式,并且分析了其对三角洲平原储集层砂体对比的约束作用。研究表明,分流河道河型可划分为3种基本类型:非典型辫流河型、非典型曲流河型和过渡型,其共同点是规模小、下切浅、分支快;而分流河道的叠置存在5种基本模式;河型与叠置特点决定了分流河道中泥质夹层分布存在2种基本类型,即平行分布式泥夹层与低角度侧积泥夹层。利用分流河道类型与叠置模式,可以分析河道发生变化的位置及井间砂体的连通情况,对储集层对比及连通关系分析具有约束作用。

Types and superposed patterns of distributary channels in a shallow lacustrine delta plain

Shallow lacustrine deltas are well-developed in many continental basins in China. Distributary channel is the main type of the sand body in a delta plain. Most of distributary channels are characterized by frequent diversion,multistage cross and superposition,which usually formed superposed distribution pattern of complex reservoirs. Based on the well-logging of distributary channel sand bodies of the shallow delta plain in Songliao Basin,this paper summarizes channel types and superposed patterns of the distributary channels in the shallow delta plain.Further,the constraint effect of these patterns on the correlation of sand bodies is analyzed. Study shows that channel types of the distributary channels can be classified into three foundational types,including an atypical braided channel type,an atypical meandering channel type and a transitional type. Small scale,shallow cutting and fast branching are the common features of these three channel types. In addition,there are five foundational superposed patterns of the distributary channels. And there are two foundational mud interbed distributions in distributary channels based on channel types and superposed patterns of the distributary channels,such as parallel distributed mud interbeds and low-angle lateral-accretion mud interbeds. Finally,in terms of channel types and superposed patterns,the changed position of certain channel types and the connection of sand bodies between boreholes can be determined,then constraint the reservoir correlation and connection analysis of the sand bodies.