珠江口盆地白云凹陷北坡新近系层序构型及油气有利区

Sequence stratigraphic architecture and play fairways of the Neogene on the north slope of Baiyun Sag,Pearl River Mouth Basin

易雪斐 张昌民 李少华 杜家元 周凤娟 袁才

Yi Xuefei Zhang Changmin Li Shaohua Du Jiayuan Zhou Fengjuan Yuan Cai

珠江口盆地白云凹陷北坡是南海油气勘探的重要区域之一。前人借助岩心、地震、测井曲线以及古生物资料,将全盆地新近系划分出14个三级层序。在等时地层层序格架下,对白云凹陷北坡重点层序进行了层序构型分析,进而指导了油气勘探有利区域的预测。从北向南,研究区依次发育H型、TH型、T型以及L型层序。其中,L型和H型层序有利于储层发育,而T型有利于烃源岩发育。另外,内、外多种地质条件的共同控制使得白云凹陷北坡新近系发育着不同类型的三角洲,单个层序内可依次出现陆架边缘三角洲—内陆架三角洲—中陆架三角洲的交替。L型层序主要由陆架边缘三角洲-峡谷水道-浊积扇体等沉积体系组成;TH型、T型层序以内-中陆架三角洲及陆棚体系为主;H型主要包括了中陆架三角洲-陆棚沉积体系。白云凹陷北部的内-中陆架三角洲中的分流水道,以及白云凹陷中部的陆架边缘三角洲中的水下分流河道、河口坝及远砂坝、峡谷水道、浊积扇体均为油气富集的有利砂体。

The north slope of Baiyun Sag is one of the important areas for the oil-gas exploration in Pearl River Mouth Basin. Based on cores,seismic,log and paleontological data,14 third-order sequences were identified in the Neogene of the study area by the former researcher. Under an isochronous stratigraphic framework,this paper analyzed the sequence architecture of key sequences on the north slope of Baiyun sag,and predicted the play fairways. From north to south,4 types of sequences,including H type,TH type,T type and L type,were developed successively. Among them,the H type and L type were favorable for reservoir development,while T type was favorable for development of source rocks. Moreover,the joint control of multiple geologic conditions led to the development of various types of delta in the Neogene on the north slope of Baiyun sag. Alternating shelf-margin delta,inner-shelf delta and mid-shelf delta may occur successively in a single sequence. The L type sequence is mainly composed of shelf-margin delta,canyon channel and turbidite fans;the T and TH type sequences are dominated by inner-mid shelf delta and shelf system;and the H type sequence consists minaly of mid-shelf delta and shelf system. As a result,distributary channel sandbodies in the inner- or mid-shelf delta in the northern part of Baiyun sag,as well as the underwater distributary channel,river mouth bars,distal bars,canyon channel and turbidite fans were all favorable for oil & gas accumulation in the study area.

10.11743/ogg20130209