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通过野外露头和岩心观察、薄片鉴定分析,结合测井和录井资料,对柴达木盆地北缘古近系-新近系的沉积相及其特征进行了深入研究。研究表明,该区主要发育冲积扇-辫状河-辫状河三角洲-滨浅湖沉积体系,建立了相应的辫状河相沉积序列及沉积模式、间歇性湖泊沉积相模式。研究区辫状河相发育两套不同地层,中下部广泛发育粒度粗的河床亚相沉积,河漫滩亚相发育不多;而中上部河床亚相沉积较少发育,粒度细的河漫滩亚相沉积则急剧增加。这是由于降水量及气候变化造成冲积扇及河流水动力变化形成的。这种变化还造成沉积物供应速率的变化以及湖平面升降的变化,导致湖盆湖岸线的迁移与河流及三角洲沉积范围的变迁,这种变迁最终造成了沉积序列上粒度粗细的频繁变化及有利储集岩和区域盖层的发育。
Through the outcrop and core observation in the field and the identification and analysis of the thin slices, the sedimentary facies and their characteristics of the Paleogene-Neogene system in the northern margin of the Qaidam Basin are studied based on well logging and logging data. The results show that alluvial fan-braided river-braided river delta-shallow lake sedimentary system is mainly developed in this area, and corresponding braided river sedimentary sequence and sedimentary model and intermittent lacustrine sedimentary facies model are established. There are two different strata in the braided river facies in the study area. The coarse-grained sediments in the riverbed are extensively developed in the middle and lower parts of the study area. The sub-facies of the floodplain are not well developed. The sub-facies sediments of the middle- upper part of the riverbed are less developed. increase. This is due to precipitation and changes in climate caused by alluvial fans and river hydrodynamic changes. This change also resulted in changes in sediment supply rates and changes in lake level rise and fall, resulting in the migration of the lake basin shoreline and changes in the depositional range of rivers and deltas, which eventually led to frequent changes in grading and thickness of sedimentary sequences Development of reservoir rocks and regional cap rocks.