Sedimentary characteristics and types of beach bars deposited in modern times in nearshore of Qinghai Lake
Han Yuanhong1, 2, 3, Hao Lewei2, Wang Qi2, Lu Jianlin3, Zhu Jianhui3, Luo Houyong3
1 Ocean College,Zhejiang University,Zhoushan 316000,Zhejiang; 2 Lanzhou Center for Oil and Gas Resources,Institute of Geology and Geophysics,CAS,Lanzhou 730000,Gansu; 3 Wuxi Institute of Petroleum Geology,SINOPEC,Wuxi 214151,Jiangsu
Abstract：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,which were 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.
Han Yuanhong,Hao Lewei,Wang Qi et al. Sedimentary characteristics and types of beach bars deposited in modern times in nearshore of Qinghai Lake[J]. JOPC, 2016, 18(5): 759-768.
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