石油与天然气地质 ›› 2025, Vol. 46 ›› Issue (5): 1430-1445.doi: 10.11743/ogg20250504

• 油气地质 • 上一篇    

陆源物质输入对有机质类型的影响——以鄂尔多斯盆地三叠系延长组长73油层亚组页岩为例

耳闯1,2(), 关宏博1, 刘伟3, 程妮4, 白洁5, 胡崇6   

  1. 1.西安石油大学 地球科学与工程学院,陕西 西安 710065
    2.陕西省油气成藏地质学重点实验室,陕西 西安 710065
    3.中国石油 勘探开发研究院,北京 100083
    4.延长油田股份有限公司,陕西 延安 716000
    5.西南石油大学 地球科学与技术学院,四川 成都 610500
    6.中国石油集团测井有限公司 长庆分公司,陕西 西安 710200
  • 收稿日期:2025-08-02 修回日期:2025-08-29 出版日期:2025-10-30 发布日期:2025-10-29
  • 第一作者简介:耳闯(1982—),男,副教授,沉积储层与非常规油气地质学。E‑mail: erchuang@xsyu.edu.cn
  • 基金项目:
    国家自然科学基金项目(41702132)

Impacts of terrigenous inputs on organic matter type: A case study of shales in the Chang 73 oil sub-group of the Triassic Yanchang Formation, Ordos Basin

Chuang ER1,2(), Hongbo GUAN1, Wei LIU3, Ni CHENG4, Jie BAI5, Chong HU6   

  1. 1.School of Earth Sciences and Engineering,Xi’an Shiyou University,Xi’an,Shaanxi 710065,China
    2.Shaanxi Key Laboratory of Petroleum Accumulation Geology,Xi’an,Shaanxi 710065,China
    3.Research Institute of Petroleum Exploration & Development,PetroChina,Beijing 100083,China
    4.Yanchang Oil Field Co. ,Ltd. ,Yan’an,Shaanxi 716000,China
    5.School of Geoscience and Technology,Southwest Petroleum University,Chengdu,Sichuan 610500,China
    6.Changqing Branch,China National Logging Corporation,Xi’an,Shaanxi 710200,China
  • Received:2025-08-02 Revised:2025-08-29 Online:2025-10-30 Published:2025-10-29

摘要:

为了探究陆源物质输入对半深湖-深湖相页岩有机质类型的影响,以鄂尔多斯盆地三叠系延长组长73油层亚组页岩为例,选取延长组沉积期湖盆东北部、西北部和西南部的4口钻井岩心样品,综合开展岩石学、沉积学以及有机地球化学研究,分析了陆源物质输入对有机质类型的影响。研究结果表明:①4口钻井的样品为富有机质泥岩和页岩,成熟度(镜质体反射率Ro)介于0.91% ~ 1.03%,属于中-低成熟度页岩;干酪根类型为Ⅱ1型和Ⅱ2型,显微组分均以腐泥组为主,镜质组次之,不同井之间显微组分类型有较大的差异。②长73油层亚组页岩发育层状页岩、不连续-连续纹层状页岩、块状-不连续纹层状含粉砂页岩、块状-不连续纹层状粉砂质页岩、层状粉砂质页岩、纹层状粉砂质页岩和块状粉砂质页岩等7种岩相类型。其中,层状页岩受陆源物质输入的影响最小,而块状-不连续纹层状粉砂质页岩、层状粉砂质页岩、纹层状粉砂质页岩以及块状粉砂质页岩受陆源物质输入的影响最大。这4口井中,W336井受陆源碎屑输入影响较小,发育Ⅱ1型干酪根,显微组分中腐泥组含量为64% ~ 83%,占绝对优势;其余3口井受陆源碎屑的输入影响较大,以Ⅱ2型干酪根为主,镜质组含量介于15% ~ 42%。③在强陆源物质输入的影响下,半深湖-深湖环境中有机质母质类型仍以水生生物为主,有机质类型好,且伴随石英和长石等陆源输入的高等植物碎屑,在缺氧底层水中与藻类共存,形成了Ⅱ1-Ⅱ2混合型干酪根,有机质类型变差。

关键词: 干酪根类型, 显微组分, 陆源物质, 页岩岩相, 富有机质页岩, 延长组, 三叠系, 鄂尔多斯盆地

Abstract:

This study aims to explore the impacts of terrigenous inputs on the organic matter type of semi-deep- to deep-lacustrine shales. Focusing on shales in the 3rd sub-group of the 7th oil group of the Triassic Yanchang Formation (also referred to as the Chang 73 oil sub-group) in the Ordos Basin, we conduct comprehensive petrological, sedimentological, and geochemical analyses on core samples from four wells located in the northeastern, northwestern, and southwestern parts of the lacustrine basin during the deposition of the Yanchang Formation. Accordingly, the impacts of terrigenous inputs on the organic matter type are delved into. The results indicate that the samples involved are all rich in organic matter, with maturities ranging from 0.91% to 1.03%, suggesting medium to low maturity. The organic matter comprises types Ⅱ1 and Ⅱ2 kerogens, with kerogen macerals dominated by sapropelinite, followed by vitrinite. Notably, maceral types differ greatly across different wells. Shales in the Chang 73 oil sub-group comprise seven lithofacies types: layered shale, shale with discontinuous to continuous laminae, silt-bearing shale with massive-discontinuous laminae, silty shale with massive-discontinuous laminae, layered silty shale, laminated silty shale, and massive silty shale. The layered shale, among others, is the least affected by terrigenous inputs, whereas the last four lithofacies are strongly affected. Shales from well W336 are weakly influenced by terrigenous clastic inputs. Correspondingly, type Ⅱ1 kerogen occurs in this well, with macerals dominated by sapropelinite (with a content of 64% ~ 83%). In contrast, shales from the other three wells are more strongly affected by terrigenous clastic inputs. In these wells, type Ⅱ2 kerogen predominates, with vitrinite content ranging from 15% to 42%. Despite the strong influence of terrigenous inputs, the parent materials of organic matter in the semi-deep to deep lacustrine environment remain dominated by aquatic organisms, producing favorable organic matter types. However, in the anoxic bottom water, higher plant debris accompanied by terrigenous inputs such as quartz and feldspar coexist with algae, leading to the formation of mixed type Ⅱ1-Ⅱ2 kerogen and comparatively less favorable organic matter types.

Key words: kerogen type, terrigenous material, maceral, shale lithofacies, organic-rich shale, Yanchang Formation, Triassic, Ordos Basin

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