Important Deepwater Hydrocarbon Reservoirs: the Central Canyon System in the Qiongdongnan Basin
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摘要: 南海北部海域琼东南盆地发育一个大型中央峡谷体系，平面上呈“S”型NE向展布，西起莺歌海盆地中央拗陷带东缘，横穿琼东南盆地中央拗陷带，向东延伸进入西沙海槽。通过2D及3D地震资料的精细解释和钻井资料综合分析，研究揭示该峡谷体系可以划分为4个区段，不同区段不仅具有明显不同的剖面形态，而且具有不同沉积物构成、沉积微相以及不同沉积物源。不同区域峡谷形态及充填分析表明，自西向东，中央峡谷下切深度越来越大，下切层位越来越老。其下切剖面形态发育有“V”、“U”、“W”和复合型。其中“V”型峡谷下切深度最大，冲刷、削截特征最明显。峡谷西段以浊积水道沉积为主，峡谷东段为浊积水道与块体流沉积互层沉积，但在不同区带不同沉积物所占比例有一定差异。浊积水道沉积的物源主要来自于盆地西侧，块体流沉积的物源主要来自于盆地北部陆坡体系，从而，来自于西部浊积水道沉积与来自于北部块体流沉积在中央峡谷内形成了多源多期发育的复杂的峡谷系统。Abstract: The Central Canyon in the Qiongdongnan basin shows a Sshaped NEtrending depositional system, which originates from the east margin of the Yinggehai basin, crosses the Central depression and extends into the Xisha trough. Based on the detailed interpretation of 2D and 3D seismic data and drillhole data, the Central Canyon can be divided into 4 segments. Each segment has not only different morphology in section, but also has distinct depositional architectures, genetic facies and sedimentsupplies. Analysis of morphology and infilling features indicates that the canyon shows the deeper downcutting and scours to the older strata eastwards. There are 4 types of V, U, W and composed shapes in vertical. Of them, Vtyped canyon shows the strongest downcutting, and the more significant scouring. Turbidite channel deposits are dominated in the western segment. Interbeds of turbidite channel and mass transport deposits occur in the eastern segment, but there are different ratios in different places. Turbidite channel deposits originate from the west side, however, mass transport deposits originate from the slope system in the northern side of the basin. Those deposits from different sedimentsupplies are composed of a multipleepisodic and multiple sedimentsupplied complex canyon system.
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Key words:
- deepwater canyon /
- turbidite channel /
- mass transport deposits /
- Qiongdongnan Basin /
- Miocene
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