细粒沉积岩岩相划分类型及其油气勘探意义——以四川盆地川西坳陷须家河组五段为例

doi:10.13809/j.cnki.cn32-1825/te.2023.05.002

摘要/Abstract

摘要：

为解决四川盆地川西坳陷须家河组五段（以下简称须五段）细粒沉积岩岩性复杂、“甜点”类型难以明确的问题，利用X射线衍射、岩石薄片、扫描电镜、物性、有机碳、元素分析等多种地质资料，结合岩心观察，在分析岩相类型和沉积古环境演化关系的基础上，划分了14种岩相类型，并基于页岩气评价参数对比分析，确定了发育“甜点”的主要岩相类型，为须五段陆相页岩气勘探指明了方向。结果表明：①川西坳陷须五段主要发育块状黏土质粉砂岩、块状混合沉积岩，其次为纹层混合沉积岩、纹层黏土质粉砂岩和块状粉砂质黏土岩；②须五段沉积环境经历了微咸水—浅水—干热、淡水—水体较深—湿润、微咸水—浅水—干热的演化过程，陆源输入先减少后增加，须五段中部是有机质富集的有利层段；③纹层黏土质粉砂岩和纹层混合沉积岩有机质含量较高，储集空间以碎屑颗粒溶孔为主，脆性矿物含量较高，可压裂性较好，是“甜点”发育的有利岩相类型。

关键词: 川西坳陷, 须五段, 细粒沉积岩, 岩相划分类型

Abstract:

Due to the complex lithology of fine-grained sedimentary rocks and the difficulty to determine the “sweet spot” of the fifth member of Xujiahe Formation（short for Xu-5 Member） of western Sichuan Depression, Sichuan Basin, a comprehensive geological analysis was conducted. This analysis encompassed various geological data sources, including X-ray diffraction, thin sections, scanning electron microscopy, physical properties, organic carbon content, and elemental analysis. Additionally, core observations were incorporated into the study. Upon scrutinizing this array of data, a classification of 14 distinct lithofacies types was established. This categorization was formulated based on the analysis of lithofacies and the evolution of sedimentary paleoenvironments. Furthermore, through a comparative examination of shale gas evaluation parameters, the primary lithofacies types constituting the “sweet spots” were identified. This not only sheds light on the composition of Xu-5 Member but also provides valuable guidance for the exploration of continental shale gas within this formation. The results indicate that: ①The main lithofacies of Xu-5 Member in western Sichuan Depression are massive clayey siltstone and massive mixed sedimentary rock, followed by laminated mixed sedimentary rock, laminated clayey siltstone and massive silty clay rock; ②The sedimentary paleoenvironment of Xu-5 Member undergoes the process from dry heat sedimentary with shallow brackish water to wet sedimentary with deep fresh water, then back to dry heat sedimentary with shallow brackish water. The land source input decreases first and then increases. The middle part of Xu-5 Member is the “sweet spot” for the enrichment of organic matter. ③Laminated clayey siltstone and laminated mixed sedimentary rock are favorable lithofacies types for “sweet spot” development due to the high organic matter content, debris particle dissolution pore, high content of brittle minerals and good fracturing performance.

Key words: western Sichuan Depression, Xu-5 Member, fine-grained sedimentary, types of lithofacies assemblages

中图分类号:

TE121

熊亮,曹勤明,张玲等. 细粒沉积岩岩相划分类型及其油气勘探意义——以四川盆地川西坳陷须家河组五段为例[J]. 油气藏评价与开发, 2023, 13(5): 548-558.

Liang XIONG,Qinming CAO,Ling ZHANG, et al. Types of fine-grained sedimentary rocks assemblage and its significance for shale oil exploration: A case study of the fifth member of Xujiahe Formation in western Sichuan Depression, Sichuan Basin[J]. Petroleum Reservoir Evaluation and Development, 2023, 13(5): 548-558.

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