柴北缘鱼卡地区中侏罗统石门沟组沉积相特征研究

沉积相分析是有机质富集及油页岩和煤形成和分布研究的基础。通过鱼油页1井岩芯的岩性组合、泥岩颜色、沉积结构和构造、含有物及接触关系等特征研究,结合显微镜下薄片鉴定、粒度分析和地球物理测井资料分析,得出柴北缘鱼卡地区中侏罗统石门沟组主要发育三角洲和湖泊沉积相类型,并进一步识别出5种沉积亚相及11种沉积微相。中侏罗统石门沟组沉积相组合在垂向上具有一定的规律:页岩段沉积物较细,底部为砂质浅湖与泥质浅湖交替,向上为半深湖-深湖相沉积,而顶部存在滑塌作用形成的浊积岩,浊积岩顶底均与半深湖-深湖相暗色泥岩突变接触;含煤段底部为三角洲平原沉积,向上沉积物入湖为三角洲前缘沉积。含煤段中下部为一套沉积厚煤层的湖沼沉积物,向上为浅湖沉积物,顶部为一套厚层的三角洲前缘沉积物。沉积相分析可以为本区层序地层及能源矿产赋存特征研究奠定基础。

Sedimentary facies characteristics in Middle Jurassic Shimengou Formation, Yuqia area, North Qaidam Basin

Sedimentary facies analysis is the basis for the study of organic matter enrichment, oil shale formation and coal distribution. By means of rock association, mudstone colour, sedimentary structure, the containing, combined with the microscopic identification and geophysical logging data of borehole YYY1,2 types of sedimentary facies of fan delta and lake have been identified, and 5 kinds of sedimentary subfacies and 11 kinds of sedimentary microfacies have been further identified. Sedimentary facies assemblage of Middle Jurassic Shimengou Formation has displayed a certain rule vertically:sediments of the Shale Member of Shimengou Formation were relatively fine, the bottom of the Shale Member were sandy shallow lake and argillaceous shallow lake microfacies, upward were semi-deep to deep lake sediments, the top were turbidite sediments which were abruptly contact with the dark mudstone of semi-deep to deep lake sediments; while sediments of the Coal-bearing Member of Shimengou Formation were relatively coarse, the bottom were deposited delta plain sediments and upward were delta front sediments, the lower part deposited a set of marsh sediments with thick coal seams and upward were shallow lake sediments. The top part deposited a set of thick delta front deposit. The analysis of sedimentary facies can lay a foundation for the study of sequence stratigraphy and energy minerals occurrence of Qaidam Basin.