北羌塘水合物钻井QK-6孔中更新世以来沉积记录及意义

发布时间：2018-02-17 06:22

  本文关键词： 沉积记录 砾石特征 孢粉组合 水合物钻井 更新世　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：本论文利用我国天然气水合物勘查和开采专项2014年在北羌塘冻土区水合物钻井QK-6第四系沉积物展开了沉积学研究,得到以下成果和认识:(1)综合利用2个ESR测年和5个生物或沉积标志年代记录,将该井246.4m岩心确定为中更新世1311±174 ka以来沉积,建立了该井的地层年代框架。(2)获得该钻孔中更新世-全新世冻土的粒径及垂向变化记录,在此基础上尝试建立了该套沉积序列的沉积相,指出该套沉积总体为湖相沉积的的滨湖和扇三角洲相,并进一步划分为6个微相。(3)对该套沉积序列中砾石组分进行了进一步研究,发现砾石含量变化分为3段,下段(246.40-172.00m)极低含量段,中段(172.00-55.25m)含量逐增段,上段(55.25-0m)高含量段,其中下段砾石磨圆度比中段和上段好。初步分析了这三段砾石的岩石学和化学成分组成及垂向变化。(4)孢粉分析可识别出5个孢粉带,指示了该区周边陆地从中更新世由旱生草本为主的疏林草原,逐渐向旱生草原演化的过程。(5)研究表明,该套沉积序列砾石中段含量增加变化初期可能与青藏高原发生“昆仑-黄河运动”这一青藏高原构造抬升事件(0.9~0.8Ma)对比。研究初步认为,尽管该次钻探未发现水合物,从沉积条件角度来说,该井第四系冻土具有含松散的、砾粗粒径组分含量高、沉积厚度大等特征属于有利于水合物成藏的沉积条件。
[Abstract]:In this paper, the sedimentology of QK-6 Quaternary sediments of hydrate drilling in the frozen soil area of Qiangtang, North China, was carried out in 2014 by means of the exploration and exploitation of natural gas hydrate in China. Using 2 ESR dating and 5 biotic or sedimentary marker dating records, the 246.4 m core of the well is determined to have been deposited since the Middle Pleistocene period (1311 卤174ka). The stratigraphic chronological framework of the well is established. (2) the records of the grain size and vertical variation of permafrost in this borehole during the Pleistocene to Holocene are obtained, and the sedimentary facies of the sedimentary sequence are attempted to be established on this basis. It is pointed out that this set of sediments is a lacustrine and fan delta facies, and further divided into 6 microfacies. (3) the gravel components in the sedimentary sequence are further studied. It is found that the variation of gravel content is divided into three sections. The lower segment (246.40-172.00 m), the middle segment (172.00-55.25m), the upper segment (55.25-0 m), the middle segment (172.00-55.25m), The gravel grinding roundness in the lower section is better than that in the middle and upper sections. The petrology and chemical composition and vertical variation of the gravel in these three sections are preliminarily analyzed. It is indicated that the study on the evolution process of the open forest steppe, which is dominated by xerophytic herbaceous in the middle Pleistocene, to the xerophytic steppe in the surrounding land, indicates that, In the initial stage of the increase in the content of gravel in this set of sedimentary sequences, it may be compared with the "Kunlun Yellow River Movement", a tectonic uplift event of the Qinghai-Xizang Plateau, which occurred in the Qinghai-Tibet Plateau at the initial stage. The preliminary study shows that although no hydrates were found during the drilling, From the point of view of sedimentary conditions, the Quaternary permafrost of the well has the characteristics of loose, high content of coarse gravel-size components and large deposition thickness, which are favorable to hydrate accumulation.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13;P512.2;P534.631
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本文编号：1517425