石油与天然气地质 ›› 2024, Vol. 45 ›› Issue (4): 893-909.doi: 10.11743/ogg20240402

• 油气地质 • 上一篇    下一篇

基于变尺度岩相组合的陆相页岩源-储耦合机理探讨

胡宗全1,2,3(), 刘忠宝1,2,3, 李倩文1,2,3, 吴舟凡4   

  1. 1.页岩油气富集机理与有效开发全国重点实验室，北京 102206
    2.中国石化页岩油气勘探开发重点实验室，北京 102206
    3.中国石化 石油勘探开发研究院，北京 102206
    4.中国地质大学（北京），北京 100083
  • 收稿日期:2024-04-17 修回日期:2024-07-12 出版日期:2024-09-05 发布日期:2024-09-05
  • 第一作者简介:胡宗全（1971—），男，博士、教授级高级工程师，非常规油气地质。E‑mail： huzongquan.syky@sinopec.com。
  • 基金项目:
    国家科技重大专项(2017ZX05036-004);中国石油化工股份有限公司基础前瞻项目(P23240-3)

Exploring source rock-reservoir coupling mechanisms in lacustrine shales based on varying-scale lithofacies assemblages： A case study of the Jurassic shale intervals in the Sichuan Basin

Zongquan HU1,2,3(), Zhongbao LIU1,2,3, Qianwen LI1,2,3, Zhoufan WU4   

  1. 1.State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development，Beijing 102206，China
    2.Key Laboratory of Shale Oil/Gas Exploration and Production Technology，SINOPEC，Beijing 102206，China
    3.Petroleum Exploration and Production Research Institute，SINOPEC，Beijing 102206，China
    4.China University of Geosciences （Beijing），Beijing 100083，China
  • Received:2024-04-17 Revised:2024-07-12 Online:2024-09-05 Published:2024-09-05

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摘要：

中国陆相页岩层系沉积成因及岩相组合复杂多样，陆相页岩源、储特征及耦合机理研究薄弱。以四川盆地侏罗系页岩层段为研究对象，以岩石学、沉积学及非常规储层地质学等理论为指导，综合运用岩矿、有机球化学及页岩储层表征等多种实验测试技术，开展了基于变尺度岩相组合的陆相页岩源-储耦合机理研究。提出了宏观与微观结合定岩相、变尺度分析定岩相组合的研究思路与方法，识别出陆源泥-砂沉积型、内源泥-灰沉积型和混源泥-砂-灰沉积型3种沉积成因岩相组合类型。研究发现：①页岩夹介壳灰岩或粉砂岩大尺度组合页岩段中可发育较多纹层-薄层状方解石介壳层或粉砂层，同一组合中不同尺度夹层类型具有较好的一致性；②大尺度岩相组合中米级介壳灰岩或粉砂岩层储集物性较差，对油气储集贡献有限，而小尺度岩相组合中毫米级纹层与厘米级薄层状方解石介壳粒内孔较发育，且内部有暗色有机质充填，可为油气提供有效储集空间。建立了3种沉积成因岩相组合的源-储耦合发育模式，提出由陆源型—混源型—内源型沉积岩相组合，源（总有机碳含量TOC）-储（孔隙度）参数相关性依次变好，其相关性主要与热演化程度、有机显微组分及无机矿物差异密切相关。探讨了不同类型、不同尺度岩相组合形成的影响因素，分析了从变尺度岩相组合角度认识陆相页岩油气源、储特征及耦合机理的必要性，旨在探索陆相页岩油气富集机理研究的新思路。

关键词: 陆相页岩油气, 变尺度岩相组合, 介壳灰岩, 源-储耦合, 页岩储层, 侏罗系, 四川盆地

Abstract:

China’s lacustrine shale sequences exhibit complex sedimentary genesis and lithofacies assemblages， and studies on their source rock-reservoir characteristics and coupling mechanisms remain limited. Guided by theories of petrology， sedimentology， and unconventional reservoir geology， we investigate the Jurassic shale intervals within the Sichuan Basin. An integration of experimental and testing techniques such as rock and mineral analyses， organic geochemistry， and shale reservoir characterization is applied to explore the source rock-reservoir coupling mechanisms in the lacustrine shale based on varying-scale lithofacies assemblages. As a result， a methodology that combines macroscopic observations with microscopic analyses to identify lithofacies and uses varying-scale analysis to determine lithofacies assemblages is put forward in the study. Using this， we identify three types of lithofacies assemblage in terms of sedimentary genesis： terrestrial mud-sand sedimentary type， endogenetic mud-lime sedimentary type， and mixed source mud-sand-lime sedimentary type. Our findings indicate that many lamellar to thin-layered calcite-shell or silt layers tend to occur in the shale intervals featuring large-scale lithofacies assemblages consisting of shale interbedded with shell limestone or siltstone， with varying-scale interlayers within the same lithofacies assemblage being of the same type. Meter-scale shell-limestone or siltstone layers within large-scale lithofacies assemblages display inferior reservoir physical properties， thus contributing minimally to hydrocarbon accumulation. In contrast， millimeter-scale laminae and centimeter-scale thinly-layered calcite shells within small-scale lithofacies assemblages feature well-developed intragranular pores filled with dark organic matter， providing effective storage spaces for hydrocarbons. The source rock-reservoir coupling models for the three types of lithofacies assemblages are established， revealing that the correlations between the source rock （total organic carbon， TOC） and reservoir （porosity） for these lithofacies assemblages show a gradual improvement from terrigenous to mixed and then to endogenetic assemblages. This finding is closely associated with their differences in maturity， organic macerals， and inorganic minerals. Additionally， we explore the factors affecting the formation of various lithofacies assemblages different in type and scale and analyze the necessity of understanding the source rock-reservoir characteristics and their coupling mechanisms of lacustrine shale oil and gas from the perspective of varying-scale lithofacies assemblage， aiming to develop a novel philosophy of research on the hydrocarbon accumulation mechanism of lacustrine shales.

Key words: lacustrine shale oil and gas, varying-scale lithofacies assemblage, shell limestone, source rock-reservoir coupling, shale reservoir, Jurassic, Sichuan Basin

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