石油学报 ›› 2020, Vol. 41 ›› Issue (8): 940-959.DOI: 10.7623/syxb202008004

• 地质勘探 • 上一篇    下一篇

柴达木盆地西部渐新统纹理石沉积特征与原位成藏

王建功1,2, 张永庶3, 李翔1, 徐丽1, 石亚军1, 黄叶秋3, 王玉林1, 管斌3, 张世铭1,2, 高妍芳1   

  1. 1. 中国石油天然气股份有限公司勘探开发研究院西北分院 甘肃兰州 730020;
    2. 中国石油天然气集团公司油藏描述重点实验室 甘肃兰州 730020;
    3. 中国石油青海油田公司勘探开发研究院 甘肃敦煌 736202
  • 收稿日期:2019-08-12 修回日期:2020-01-20 出版日期:2020-08-25 发布日期:2020-09-01
  • 通讯作者: 王建功,男,1969年12月生,1994年获阜新矿业学院学士学位,2006年获中国地质大学(北京)博士学位,现为中国石油勘探开发研究院西北分院高级工程师,主要从事沉积学、层序地层学和油气勘探的研究工作。Email:wangjg@petrochina.com.cn
  • 作者简介:王建功,男,1969年12月生,1994年获阜新矿业学院学士学位,2006年获中国地质大学(北京)博士学位,现为中国石油勘探开发研究院西北分院高级工程师,主要从事沉积学、层序地层学和油气勘探的研究工作。Email:wangjg@petrochina.com.cn
  • 基金资助:

    中国石油天然气股份有限公司科技重大专项(2016E-01)资助。

Sedimentary characteristics and in-situ accumulation of the Oligocene laminites in the western Q aidam Basin

Wang Jiangong1,2, Zhang Yongshu3, Li Xiang1, Xu Li1, Shi Yajun1, Huang Yeqiu3, Wang Yulin1, Guan Bin3, Zhang Shiming1,2, Gao Yanfang1   

  1. 1. PetroChina Research Institute of Petroleum Exploration and Development-Northwest(NWGI), Gansu Lanzhou 730020, China;
    2. CNPC Key Laboratory of Reservoir Description, Gansu Lanzhou 730020, China;
    3. Research Institute of Exploration and Development, PetroChina Qinghai Oilfield Company, Gansu Dunhuang 736202, China
  • Received:2019-08-12 Revised:2020-01-20 Online:2020-08-25 Published:2020-09-01

摘要:

柴达木盆地西部(柴西地区)渐新统下干柴沟组发育咸化湖泊、盐湖沉积,其盆内深水区主要发育纹层状泥晶灰岩。泥晶灰岩连同富有机质泥岩、深水粉砂岩等一起构成纹层状交互且纵向叠置的纹理化构造,形成纹理石。基于柴西地区大量的岩心、薄片及地球化学资料,通过分析咸化湖泊深水区纹理石的沉积特征及其成因机理,建立了纹理石的沉积模式,并讨论了其石油地质意义。研究表明,咸化湖泊深水区纹理石的形成受化学作用、生物作用和物理沉积作用共同控制,其结构主要表现为纹层状泥晶灰岩、富有机质泥岩、钙质粉砂岩以及少量的石膏呈交替互层状分布,纹层厚度一般为200~1 200 μm。纹理石通常由成对出现的2种不同岩性的纹层形成若干对偶纹层单元,发育水平层理和平行层理,表现出垂向加积和反旋回沉积。根据不同岩性组合可识别出5类纹理石。对纹理石形成的主控因素和对纹理石中不同岩性纹层成因机理的分析认为,碳酸盐岩纹层的形成与高矿化度粒子的化学作用和微生物的诱导作用共同控制有关,与研究区周期性的季节变化也密切相关;石膏和黄铁矿主要通过硫化合物的相互转化形成;深水区富有机质泥岩+钙质粉砂岩的纹层组合与河流、特别是洪水等事件性沉积密切相关;咸化湖泊中水体的分层特征有利于适盐性水生生物的繁盛和保存。柴西地区下干柴沟组纹理石形成于强还原咸水环境、含有大量葡萄藻和疑源类等有机质组分并伴生大量黄铁矿,具备良好生油条件,与灰岩构成良好的源-储配置,这些特征使得纹理石中易于形成低成熟、高效的原位油藏。

关键词: 微生物岩, 纹理石, 湖相碳酸盐岩, 下干柴沟组, 柴达木盆地

Abstract:

In the western Qaidam Basin, the Oligocene Xiaganchaigou Formation developed salinized lacustrine deposits, and the deep water area of the basin mainly developed laminated micritic limestones. Micritic limestone, together with organic-rich mudstone and deep water siltstone, forms a laminized texture with interbedding and longitudinal overlaying, forming laminites. Based on plenty of core, thin-section and geochemical data in the western Qaidam Basin, through analyzing the sedimentary characteristics and geneses of laminites in the deep water area of salinized lake, this study establishes a sedimentary pattern of laminites and explores its significance of petroleum geology. The study shows that the formation of laminites in the deep water area of salinized lake is controlled by chemical, biological and physical sedimentation, and its structure is mainly shown as the interbedded layers of laminated micritic limestones, organic-rich mudstone, calcareous siltstone and a small amount of gypsum. The lamina thickness generally ranges from 200 μm to 1 200 μm. The laminites are usually composed of two layers of two different lithologies in pairs and form several dual lamina units, with the development of horizontal and parallel bedding, showing the characteristics of vertical accretion and reverse cyclic deposition. Five types of lamina stone can be identified according to different lithology combinations. By analyzing the main controlling factors for the formation of laminites and discussing the genesis of laminae of various lithologies in the laminites, it is believed that the formation of carbonate lamina is jointly controlled by the chemical action of high-salinity particles and the induction from microorganisms. This is also closely related to the periodic seasonal changes in the study area. Gypsum and pyrite are mainly formed by the mutual transformation of sulfur compounds. The lamina combination of organic-rich mudstone and calcareous siltstone in deep water is closely related to the event-causing deposition of rivers, especially floods. The stratification in salinized lake is beneficial to the flourishing and preservation of halophilic aquatic organisms. The laminites of Xiaganchaigou Formation in the western Qaidam Basin are formed in a highly reduced salt water environment, contained plenty of organic matter components such as Botryococcus braunii and acritarchs, and associated with plenty of pyrites. It has good oil-generating conditions and constitutes a good source-reservoir configuration together with limestone. These characteristics make it easy to form low-mature and high-efficiency in-situ reservoirs in the laminites.

Key words: microbialite, laminites, lacustrine carbonate rock, Xiaganchaigou Formation, Qaidam Basin

中图分类号: