远源浅水辫状河三角洲前缘储层构型模式研究:以冀中坳陷饶阳凹陷留西油田L18断块为例*

利用渤海湾盆地冀中坳陷饶阳凹陷留西油田留18断块内岩心、录井、测井、三维地震以及生产动态资料,应用层次分析的方法,对远源浅水辫状河三角洲前缘进行了相带划分,对砂体构型进行了解剖,明确了各相带内沉积构型样式的特征,建立了远源浅水辫状河三角洲前缘精细的沉积构型模式。研究表明: (1)研究区水体整体较浅,远源浅水辫状河三角洲前缘亚相广泛发育,并进一步分为前缘近端、前缘中端和前缘远端3个相带,不同相带在砂体厚度、岩性组合特征和砂体横向连通性等方面存在差异。(2)前缘远端水下分流河道水动力较弱,所携带沉积物较少,形成横向连通性较差的小规模河口坝,河口坝之间的厚层泥质披覆夹层为主要的夹层类型。(3)前缘中端分流河道水动力强度中等,形成串珠状或分叉树枝状的河口坝,单一河口坝由2~4期前积增生体构成,前积倾角约2.2°,增生体间的泥质披覆夹层为主要的夹层类型。(4)前缘近端分流河道水流强度较大,下切作用较强,所携带沉积物较多;下伏河口坝互相叠置切割,形成连片分布的复合体;单个河口坝由多个前积增生体构成,前积倾角约3.5°,增生体内的漫溢夹层及增生体间的泥质披覆夹层为主要夹层类型。

Reservoir architecture pattern analysis of distal shallow water braided delta front: A case study of L18 fault block,Liuxi Oilfield,Raoyang sag,Jizhong Depression

Core, well logging, 3D seismic data and production dynamic data of L18 fault block in Liuxi Oilfield, Raoyang sag, Jizhong Depression, were used to analyze the facies of distal shallow water braided delta front and architecture pattern of sand body and to establish a refined sedimentary architecture model of distal shallow water braided delta front. The research shows that: (1) The water was at a low level in study area and the delta front was widely developed. The delta front is divided into the proximal, middle and distal belts. Each facies belt varied in thickness, lithology combination and the lateral connectivity of the sand body; (2) The distributary channel in the distal belts was formed under weak hydrodynamics and limited sediment supply, which resulted in a small-scale mouth bar with poor lateral connectivity, and the thick muddy layers deposited between the bars formed the main type of interlayer.(3) The hydrodynamic strength of the distributary channel in the middle belt is moderate, forming bead-like or bifurcated mouth bars. A single mouth bar is composed of 2~4 accretion sand bodies with a dip angle of~2.2°. The muddy layer sdeposited between the accretion sand bodies is the main type of interlayer; (4) Controlled by the strong hydrodynamics, sufficient sediment supply and strong incision effect, the mouth bar stacked with each to form a continuously distributed mouth bar complex. The single mouth bar is composed of multiple accretion sand bodies with a high dip angle of 3.5°. The overflow muds and muddy deposited between accretion sand bodies are the two main types of interlayer developed in the mouth bar.