青海湖近岸现代沉积滩坝主要类型及沉积特征  

Sedimentary characteristics and types of beach bars deposited in modern times in nearshore of Qinghai Lake

作　　者：韩元红[1,2,3] 郝乐伟[2] 王琪[2] 陆建林[3] 朱建辉[3] 罗厚勇[3] Han Yuanhong Hao Lewei Wang Qi Lu Jianlin Zhu Jianhui Luo Houyong(Ocean College, Zhejiang University, Zhoushan 316000, Zhefiang Lanzhou Center for Oil and Gas Resources, Institute of Geology and Geophysics, CAS, Lanzhou 730000, Gansu Wuxi Institute of Petroleum Geology, SINOPEC, Wuxi 214151, Jiangsu)

机构地区：[1]浙江大学海洋学院,浙江舟山316000 [2]中国科学院油气资源研究重点实验室,甘肃兰州730000 [3]中国石化石油勘探开发研究院无锡石油地质研究所,江苏无锡214151

出　　处：《古地理学报》2016年第5期759-768,共10页Journal of Palaeogeography：Chinese Edition

基　　金：国家自然科学基金(编号:41502142)项目资助~~

摘　　要：滩坝是隐蔽油气藏最重要的沉积储集层类型之一,已成为陆相断陷盆地油气勘探的重要领域。现代沉积滩坝的研究是深入认识滩坝沉积相的有效手段。环湖考察研究发现青海湖近岸滩坝类型多样,主要发育了废弃三角洲前缘处滩坝、三角洲侧缘处滩坝、湖岸线拐弯处滩坝、开阔滨浅湖处滩坝和冲积扇改造处滩坝5种类型。通过对各种类型滩坝剖面的详细分层及沉积物室内矿物组成分析等,发现不同类型滩坝砂体沉积特征存在很大差异。整体而言,青海湖近岸滩坝沉积物粒度较粗,黏土含量低,结构成熟度较高,沉积构造多见平行层理、交错层理和冲洗交错层理,垂向上表现出上粗下细的反韵律特征。同时,选取了青海湖南岸规模较大的坝相,分别对坝主体、坝间和坝侧缘进行详细的探槽剖面分析,得出坝主体单旋回厚度较坝间和坝侧缘大,沉积物粒度也相对较粗,黏土含量最低,分选性也最好,是发育为隐蔽油藏最有利的区域。Beach bars are important sediment system that can develop into subtle reservoirs. They have become target region for oil-gas exploration（ especially in the middle to late periods） in continental faulted basins. The studies of beach bars deposited in modern times could provide the basis for the studies of subtle beach bar reservoirs. Fieldworks for beach bars were taken,trenches and outcrops of beach bars were observed, and sediments of beach bars were analyzed in Qinghai Lake. According to sediment sources and geographic locations,beach bars were recognized into five types in the study area,whichwere beach bars in abandoned delta front area,beach bars in delta flank area,beach bars in bend shoreline area,beach bars in wide offshore area and beach bars near alluvial fan area. Sedimentary characteristics of those beach bars were studied by cross-section analysis. It was found that there were substantial differences between different types of beach bars. It was summarized overall that sediments of beach bars were coarse,medium sorted and rounded. The main bedding structures of the beach bars were parallel bedding,cross bedding and flushing cross-bedding in Qinghai Lake. Beach bars developed in here have a reverse rhythm in ascending order. Moreover, sedimentary characteristics of microfacies in one typical beach bar were contrastively analyzed in southern shore of Qinghai Lake. It is suggested that the bar-center microfacies has the most coarse size,the most thick stratum,the lowest clay content and the best-sorted grains in the same sedimentary cycle,which make it is most favorable for subtle reservoirs.

关 键 词：青海湖 滩坝 沉积特征 沉积模式 

分 类 号：P512.32[天文地球—地质学]