珠江口盆地西江30-2油田新近系中新统沉积微相及层序地层分析

西江30-2油田位于珠江口盆地惠州凹陷南部的次级构造带上，油田主要分布在新近系中新统的珠江组及韩江组下部。研究区目的层段主要为三角洲沉积，其沉积微相类型丰富，既包括三角洲平原的分流河道、分流间湾、天然堤、决口扇沉积，又包括三角洲前缘的水下分流河道、河口坝、远砂坝及席状砂沉积等，其中分流河道、水下分流河道及河口坝等主要砂体的单层厚度大、连续性好。目的层段可划分为4个长期基准面旋回和15个中期旋回。根据区内的4种测井旋回划分模式，其短期旋回（五级层序）对应油藏级别；而超短期旋回（六级层序）与砂体级别一致，且基本与砂体微相的划分一致。本文中采用高分辨率层序地层学的方法进行油田开发过程中的砂体对比，充分考虑了区块大小、构造位置、沉积微相变化及井距大小，其结果表明油藏顶部以上升半旋回（正旋回）为主的分流河道或水下分流河道易产生水淹；而以下降半旋回（反旋回）为主的河口坝砂体和间湾不易水淹，这有利于剩余油的分布。

Sedimentary microfacies and sequence stratigraphy of the Miocene of Neogene in Xijiang 30-2 Oil Field,Pearl River Mouth basin

Xijiang30-2 Oil Field is located at the sub-structural belt in southern Huizhou Depression in the Pearl River Mouth basin.This oilfield is mainly distributed in the Zhujiang Formation and the lower part of the Hanjiang Formation of Miocene of Neogene. The sedimentary facies of the studied formation is a delta in Xijiang 30-2 Oil Field. In this area, the types of sedimentary microfacies include distributary channel, inter-distributary, natural levee and crevasse splay in the delta plain and underwater distributary channel, mouth bar,distributary bar and sand sheet in the delta front. The major sandbodies, such as distributary channel, underwater distributary channel and mouth bar, relatively, are thick and continuous. Meanwhile, the studied formation consists of 4 long-term base level cycles and 15 mid-term base level cycles in Xijiang 30-2 oilfield. On the basis of these, 4 types of logging models about short-term and supper short-term base level cycles are summarized in this area.As for this area, approximately, short-term base level cycle, which is equal to the fifth order sequence, can be correlated with reservoir strata,while supper short-term cycle, which corresponds to the sixth order sequence,corresponds to sand body and sedimentary micro-facies. When correlating the sand bodies based on high resolution sequence stratigraphy, it is very important to take into account the scale of the work area, the tectonic position,the diversities of the sedimentary microfacies and the well spacing.In Xijiang 30-2 Oil Field, at the reservoir top, the distributary channel or underwater distributary channel mostly with base level rising half cycle is apt to flood,however, the sand bar(distributary mouth bar or distal bar) or distributary bay mainly with base level falling half cycle is not prone to flood ,among which it is propitious to remaining oil distribution.