中非BG盆地BN区块下白垩统湖底扇沉积特征  

Sedimentary characteristics of Lower Cretaceous sublacustrine fan in BN block of BG Basin,Central Africa

作　　者：欧阳雪琪 王亮 刘峰 郑荣才[1] 任伟[1] 

机构地区：[1]成都理工大学沉积地质研究院,成都610059 [2]中国石油玉门油田分公司勘探开发研究院,甘肃酒泉735019

出　　处：《岩性油气藏》2016年第3期86-94,126,共10页Lithologic Reservoirs

基　　金：中国石油天然气集团公司研究课题"海外油气田勘探与开发技术研究"(编号:Y2013JF8-02)资助

摘　　要：湖底扇砂体是较为有利的油气储集体,深入研究其沉积特征对油气勘探具有重要意义。以中非BG盆地BN区块下白垩统P组为例,在沉积岩石学及层序地层学理论基础上,对该组岩心的沉积构造、测井曲线组合形态和地震剖面响应特征进行分析,并对区域地质特征进行研究。结果表明:中非BG盆地BN区块下白垩统P组属于湖底扇沉积,自下而上表现为正旋回沉积序列,一般发育内扇、中扇和外扇等3种亚相,以及分支水道、水道侧溢天然堤与无水道前缘席状砂等微相类型;P组湖底扇砂体受重力流作用控制,主要沿北东—南西向延伸,总体呈扇形展布,其中,中扇分支水道的砂体顶、底常被灰黑色泥岩包围,具备较好的油气富集条件;湖底扇的物源主要来自盆地东北部,于盆缘先形成较大规模的扇三角洲沉积体系,后以浊流的形式被搬运至前三角洲或更远的深水湖区,最终形成湖底扇沉积体系。P组有利储层主要分布于盆地北部陡坡带断层下降盘一侧湖底扇的内扇水道和中扇分支水道砂体中。Sublacustrine fan sand bodies are favorable oil and gas reservoirs,so the study on its sedimentary characteristics has important guiding significance for hydrocarbon exploration.Taking the Lower Cretaceous P Formation in BN block of BG Basin as an example,based on the theories of sedimentary petrology and sequence stratigraphy,this paper analyzed the sedimentary structure of cores,well logging curve combination forms and seismic response characteristics,and studied the regional geological features.The results show that sublacustrine fan is developed in the study area,showing positive cycle sedimentary sequence from bottom to top,and it can be divided into inner-fan,middle-fan and outer-fan sub-facies,which can be subdivided into micro-facies such as branch channel,channel edge natural levee and front sheet sand without channel.The sublacustrine fan sand bodies of P Formation are controlled by gravity flow,and they distributed along the NE-SW with fan shape.The sand bodies at the top and bottom of the branch channel of middle-fan are often sealed by dark-gray mudstones,with good oil and gas accumulation conditions.The sources of the sublacustrine fan mainly came from the northeastern fault basin,first formed large-scale fan delta depositional system in the margin of basin,then were transported to the prodelta or the farther deep lake in the form of turbidity current,and formed sublacustrine fan depositional system eventually.Favorable reservoirs of P Formation are mainly distributed in channel sand bodies of inner-fan and branch channel sandstones of middle-fan on one side of the hanging wall of fault in the northern basin.

关 键 词：湖底扇 测井相标志 地震相标志 沉积特征 沉积模式 下白垩统 BG盆地 

分 类 号：TE121.3[石油与天然气工程—油气勘探]