石油与天然气地质 ›› 2024, Vol. 45 ›› Issue (3): 696-709.doi: 10.11743/ogg20240309

• 油气地质 • 上一篇    下一篇

渤海湾盆地沧东凹陷古近系孔店组二段页岩高丰度有机质富集模式

蒲秀刚(), 董姜畅(), 柴公权, 宋舜尧, 时战楠, 韩文中, 张伟, 解德录   

  1. 中国石油 大港油田公司,天津 300280
  • 收稿日期:2023-10-30 修回日期:2024-05-10 出版日期:2024-07-01 发布日期:2024-07-01
  • 通讯作者: 董姜畅 E-mail:puxgang@petrochina.com.cn;dongjiangchuang@petrochina.com.cn
  • 第一作者简介:蒲秀刚(1968—),男,博士、教授级高级工程师,沉积储层、油气成藏、页岩油勘探开发。E-mail:puxgang@petrochina.com.cn
  • 基金项目:
    国家重点研发计划项目(2022YFF0801204);中国石油天然气股份有限公司科技重大专项(2023ZZ15)

Enrichment model of high-abundance organic matter in shales in the 2nd member of the Paleogene Kongdian Formation, Cangdong Sag, Bohai Bay Basin

Xiugang PU(), Jiangchang DONG(), Gongquan CHAI, Shunyao SONG, Zhannan SHI, Wenzhong HAN, Wei ZHANG, Delu XIE   

  1. Dagang Oilfield Company,PetroChina,Tianjin 300280,China
  • Received:2023-10-30 Revised:2024-05-10 Online:2024-07-01 Published:2024-07-01
  • Contact: Jiangchang DONG E-mail:puxgang@petrochina.com.cn;dongjiangchuang@petrochina.com.cn

摘要:

渤海湾盆地沧东凹陷古近系孔店组二段(孔二段)页岩有机质丰度高,具有良好的页岩油勘探潜力,但由于缺乏精细的地球化学研究,有机质富集机理尚不清晰。通过开展全岩X射线衍射、全岩光片显微组分、岩石热解、总有机碳含量(TOC)、饱和烃色谱-质谱、单体烃碳同位素、主量元素与微量元素分析测试,研究了沧东凹陷孔二段页岩有机质富集的影响因素与模式。研究结果表明:孔二段页岩有机质富集受陆源碎屑输入、古生产力、古气候、古水深和古盐度多种因素影响,这些影响因素通过控制湖盆中菌藻类生物的生长、发育,在五级层序T-R旋回转换期形成高丰度有机质富集段。陆源碎屑输入为湖盆带来的丰富营养物质提高了湖盆生产力;古气候、古水深与古盐度主导了湖盆中水生/陆源有机质贡献比例的变化;细菌活动对有机质的改造提高了页岩H/C原子量比与“腐泥化”程度。以C3开发层系T-R旋回转换期为主的⑧号小层页岩形成于温湿气候、低盐度和水体较深的沉积古环境, TOC平均为2.7 %,游离烃含量(S1)为3.7 mg/g,可动油指数(OSI)为215 mg/g,有机质丰度高、有机质类型较好,是页岩油有利靶窗。

关键词: 生烃母质, 沉积环境, 有机质富集, 页岩油, 孔店组, 古近系, 沧东凹陷, 渤海湾盆地

Abstract:

Shales in the 2nd member of the Paleogene Kongdian Formation (also referred to as the Kong 2 Member) in the Cangdong Sag contain high-abundance organic matter, showing great potential for shale oil exploration. However, the mechanisms underlying the organic matter enrichment are yet to be clarified due to the lack of fine geochemical research. Given this, we investigate the factors influencing of organic matter enrichment and the enrichment model in the Kong 2 Member shale using whole-rock X-ray diffraction, maceral identification on polished surfaces of whole-rock shale samples, rock pyrolysis, measurement of the total organic carbon (TOC) content, chromatography-mass spectrometry of saturated hydrocarbons, carbon isotopic analysis of monomer hydrocarbons, and the analyses and tests of major and trace elements. The results indicate that the organic matter enrichment inthe Kong 2 Member shale is influenced by multiple factors including terrigenous clastic input, paleoproductivity, paleoclimate, paleo-water depth, and paleosalinity. These factors govern the growth and development of algae and bacteria in the lacustrine basin of the Cangdong Sag, contributing to the formation of organic matter enrichment horizons with high TOC content during the T-R cycle transition period of the fifth-order sequence. Specifically, the terrigenous clastic input introducing abundant nutrients enhanced the biological productivity of the lacustrine basin. The paleoclimate, paleo-water depth, and paleosalinity largely determined the terrigenous/aquatic ratio (TAR) of the lacustrine basin. Furthermore, bacterial activity transformed organic matter, increasing the H/C atomic ratio and the saprofication degree of the shale. Shales in sublayer ⑧, primarily taking shape during the T-R cycle transition, of the C3 layer under development are formed under paleoenvironmental conditions of a warm and humid climate, low salinity, and deep water. This sublayer, with an average TOC content of 2.7 %, S1 of 3.7 mg/g, and producible oil index (POI) of 215 mg/g, boasts high abundance and favorable organic matter types, proving to be favorable landing zone for horizontal wells.

Key words: hydrocarbon-generating parent material, sedimentary environment, organic matter enrichment, shale oil, Kongdian Formation, Paleogene, Cangdong Sag, Bohai Bay Basin

中图分类号: