石油与天然气地质 ›› 2023, Vol. 44 ›› Issue (5): 1173-1187.doi: 10.11743/ogg20230508

• 油气地质 • 上一篇    

致密砂岩砂-泥结构发育特征及其对储集空间的控制作用

李军亮1(), 王鑫2,3(), 王伟庆1, 李博1, 曾溅辉2,3, 贾昆昆2,3, 乔俊程2,3, 王康亭2,3   

  1. 1.中国石化 胜利油田分公司 勘探开发研究院,山东 东营 257029
    2.油气资源与探测国家重点实验室,北京 102249
    3.中国石油大学(北京) 地球科学学院,北京 102249
  • 收稿日期:2023-04-07 修回日期:2023-06-02 出版日期:2023-10-01 发布日期:2023-10-19
  • 通讯作者: 王鑫 E-mail:lijunliang.slyt@sinopec.com;xinwang.geo@outlook.com
  • 第一作者简介:李军亮(1975—),男,博士、高级工程师,油气地质综合研究。 E-mail: lijunliang.slyt@sinopec.com
  • 基金项目:
    国家自然科学基金项目(41972147)

Influence of sand-mud assemblages in tight sandstones on reservoir storage spaces: A case study of the lower submember of the 3rd member of the Paleogene Shahejie Formation in the Linnan sub-sag, Bohai Bay Basin

Junliang LI1(), Xin WANG2,3(), Weiqing WANG1, Bo LI1, Jianhui ZENG2,3, Kunkun JIA2,3, Juncheng QIAO2,3, Kangting WANG2,3   

  1. 1.Exploration and Development Research Institute,Shengli Oilfield Branch Company,SINOPEC,Dongying,Shandong 257029,China
    2.State Key Laboratory of Petroleum Resources and Prospecting,Beijing 102249,China
    3.College of Geosciences,China University of Petroleum (Beijing),Beijing 102249,China
  • Received:2023-04-07 Revised:2023-06-02 Online:2023-10-01 Published:2023-10-19
  • Contact: Xin WANG E-mail:lijunliang.slyt@sinopec.com;xinwang.geo@outlook.com

摘要:

在陆相含油气沉积盆地中,沉积水体变化快,砂岩和泥岩频繁交互。不同的砂-泥互层形式导致砂岩储层的储集空间差异性明显。以渤海湾盆地惠民凹陷临南洼陷古近系沙河街组三段下亚段(沙三下亚段)为例,基于砂岩和泥岩在空间上的组合形式及其单层厚度分析,利用铸体薄片观察、物性测试和微米CT技术,系统分析不同砂-泥结构下砂岩储层的物性特征、孔隙类型和孔隙结构特征。结果表明,研究区沙三下亚段发育厚泥岩夹薄砂岩、中泥岩夹薄砂岩、厚泥岩夹中砂岩、薄砂岩-薄泥岩互层、中砂岩-中泥岩互层、厚砂岩-厚泥岩互层、中砂岩夹薄泥岩、厚砂岩夹中泥岩和厚砂岩夹薄泥岩9种砂-泥结构类型。砂岩和泥岩之间的离子交互关系,导致不同砂-泥结构砂岩储层储集能力具有较强的非均质性。对于砂/地比较小的砂-泥结构,泥岩能够为砂岩提供充足的CO32-,Ca2+,Fe2+和Mg2+离子。砂岩被胶结物完全充填,储层变得极为致密。随着砂/地比增大,泥岩无法为砂岩提供充足的CO32-,Ca2+,Fe2+和Mg2+离子。砂-泥界面附近砂岩中碳酸盐胶结作用较强,储层极为致密;而砂岩内部碳酸盐胶结作用较弱,发育少量的原生孔隙。同时,砂岩厚度比较大的砂-泥结构,有利于有机酸的注入,形成大量的粒间溶蚀孔,改善储层质量。基于砂-泥结构的差异性,揭示了砂-泥结构控制下砂岩储层储集空间演化路径和模式,对指导致密储层的甜点预测具有重要意义。

关键词: 胶结作用, 孔隙结构, 砂-泥结构, 致密储层, 济阳坳陷, 渤海湾盆地

Abstract:

The swift shifts in sedimentary water bodies in continental petroliferous sedimentary basins result in frequent intercalation of sandstone and mudstone layers. Various sandstone-mudstone intercalation patterns (sand-mud assemblages) lead to significant differences in the storage spaces in sandstone reservoirs. Focusing on the lower submember of the 3rd member of the Paleogene Shahejie Formation in the Linnan sub-sag, Huimin Sag, Bohai Bay Basin, we first analyze the spatial assemblages and single-layer thickness of sandstone and mudstone layers. Using casting thin section observations, physical property tests, and micro-CT scanning, we systematically elucidate the physical properties, pore types, and pore structures of sandstone reservoirs with different sand-mud assemblages. As indicated by the findings, the lower submember contains nine types of sand-mud assemblages, namely thick mudstone interbedded with thin sandstone, medium mudstone interbedded with thin sandstone, thick mudstone interbedded with medium sandstone, intercalated thin sandstone and thin mudstone, intercalated medium sandstone and medium mudstone, intercalated thick sandstone and thick mudstone, medium sandstone interbedded with thin mudstone, thick sandstone interbedded with medium mudstone, and thick sandstone interbedded with thin mudstone. The ionic interactions between sandstones and mudstones lead to strong heterogeneity in the storage capacity of sandstone reservoirs with different sand-mud assemblages. For sand-mud assemblages with low net-to-gross ratios, mudstones supply ample CO32-, Ca2+, Fe2+, and Mg2+ to sandstones, and sandstones are completely filled with cements. Consequently, the sandstone reservoirs become extremely tight. However, when this ratio rises, mudstones cannot provide sandstones with sufficient ions mentioned above. In this case, sandstones near the sand-mud interfaces exhibit strong carbonate cementation, forming extremely tight reservoirs. In contrast, the interior of the sandstones shows weak carbonate cementation, with a small number of primary pores present. Additionally, the sand-mud assemblages with relatively thick sandstones promote organic acid infiltration, enhancing reservoir quality through the formation of numerous intergranular dissolution pores. Based on the differences in sand-mud assemblages, we reveal the influence of sand-mud assemblages on the evolutionary path and model of the storage spaces in sandstone reservoirs. Our insights are pivotal for predicting sweet spots in tight sandstone reservoirs.

Key words: cementation, pore structure, sand-mud assemblage, tight reservoir, Jiyang Depression, Bohai Bay Basin

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