石油与天然气地质 ›› 2023, Vol. 44 ›› Issue (6): 1333-1349.doi: 10.11743/ogg20230601

• 油气地质 • 上一篇    下一篇

陆相页岩油富集机理探讨

郭旭升1,2(), 马晓潇1,2, 黎茂稳1,2, 钱门辉1,2, 胡宗全1,2   

  1. 1.页岩油气富集机理与高效开发全国重点实验室,北京 102206
    2.中国石化 石油勘探开发研究院,北京 102206
  • 收稿日期:2023-03-07 修回日期:2023-08-28 出版日期:2023-12-01 发布日期:2023-12-20
  • 第一作者简介:郭旭升(1965—),男,博士、教授级高级工程师、中国工程院院士,石油天然气地质和勘探。E-mail:guoxs.syky@sinopec.com
  • 基金项目:
    国家自然科学基金项目(42090022)

Mechanisms for lacustrine shale oil enrichment in Chinese sedimentary basins

Xusheng GUO1,2(), Xiaoxiao MA1,2, Maowen LI1,2, Menhui QIAN1,2, Zongquan HU1,2   

  1. 1.State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Beijing 102206, China
    2.Petroleum Exploration and Production Research Institute, SINOPEC, Beijing 102206, China
  • Received:2023-03-07 Revised:2023-08-28 Online:2023-12-01 Published:2023-12-20

摘要:

通过对中国陆相湖盆富有机质页岩形成的构造和沉积环境分析,明确不同湖盆类型陆相优质烃源岩发育条件存在巨大差异性,淡水湖盆形成的泥页岩层系以长英质-黏土质页岩为主要岩相,松辽盆地上白垩统青一段和鄂尔多斯盆地三叠系长7段为典型代表;而咸水湖盆陆相页岩以富碳酸盐-蒸发岩类岩相为主,济阳坳陷古近系沙河街组是典型的实例。中国陆相页岩层系具有互层/夹层、混积页岩和黏土质页岩等3种主要岩相组合类型,它们控制了陆相富有机质泥页岩的源-储耦合特征、烃类差异演化和流体性质多样性。互层/夹层型页岩源-储分离、近源运移;混积页岩宏观上源-储一体,微观上源-储分离;黏土质页岩源-储一体,整体含油。多重证据揭示,无机孔是中-低成熟陆相页岩油最有利的储集空间类型,它们与多类型、多级次微裂缝耦合形成有效的孔缝网络系统,自封闭作用有利于页岩油气原位或近源保存。在典型盆地陆相页岩层系对比分析的基础上,提出良好的源-储耦合关系、适宜的热演化程度和自封闭性是陆相页岩油富集的主控因素,初步建立了中国陆相页岩油差异富集模式。断陷湖盆陆相页岩油勘探应重视缓坡带中-低成熟纹层状页岩和深洼区中-高成熟富黏土质页岩层系,而互层/夹层型和中-高成熟黏土质页岩是坳陷湖盆陆相页岩油突破的关键。

关键词: 岩相组合类型, 孔缝系统, 源-储耦合, 成烃差异演化, 自封闭性, 富集机理, 陆相页岩油

Abstract:

By analyzing the tectonic and sedimentary environments for the formation of organic-rich shales in China’s continental lacustrine basins, we identify significant differences in the development of high-quality continental source rocks across various types of lacustrine basins. For shale sequences deposited in fresh-water lacustrine basins, the main lithofacies are felsic and clayey shales, as observed from the 1st member of the Upper Cretaceous Qingshankou Formation (K2qn1 section) in the Songliao Basin and the 7th member of the Triassic Yanchang Formation (T3yc7 section) in the Ordos Basin. For shale sequences developed in a saline lacustrine environment, however, carbonates and evaporites are dominant lithofacies, as represented by the Paleogene Shahejie Formation in the Jiyang Depression. There are three types of lithofacies assemblages for Chinese lacustrine shales, that is, the shale interbedded/intercalated with sand, mixed shale, and clayey shale. These lithofacies assemblages determine the hydrocarbon source-reservoir coupling characteristics, differential evolution of hydrocarbon generation, and property differences of in-situ fluids in the lacustrine organic-rich shales. The shale interbedded/intercalated with sand assemblage is characterized by source-reservoir separation and near-source migration. The mixed shale assemblage shows macroscopic integration and microscopic separation between source rock and reservoir. In contrast, the clayey shale acts as both the source and reservoir of in-situ generated hydrocarbons, featuring pervasive oil distribution. As revealed by evidence, inorganic pores provide the most favorable storage space for lacustrine shale oil in medium-low maturity, and form effective pore-fracture networks for hydrocarbon transport together with multi-type and multi-scale microfractures. Self-sealing capacity of shale is conducive to the in-situ or proximal preservation of shale oil and gas. Comparison of typical continental shale sequences in the Chinese sedimentary basins indicates that favorable source-reservoir coupling, suitable thermal maturity level, and self-sealing capacity of shale are the major controls for oil enrichment in lacustrine shale. This study also presents a preliminary model for differential enrichment of lacustrine shale oil in China. Therefore, the laminated shales in medium-low maturity in gentle slope zones and the clayey shale-rich strata in medium-high maturity in deep sags should be prioritized in lacustrine shale oil exploration in downfaulted lacustrine basins. Moreover, both the shale interbedded/intercalated with sand and the clayey shale in medium-high maturity are crucial to making breakthroughs in lacustrine shale oil exploration therein.

Key words: lithofacies assemblage type, pore-fracture network system, source-reservoir coupling, differential evolution of hydrocarbon generation, self-sealing, enrichment mechanism, lacustrine shale oil

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