壳化石与页岩油的成因关系——以川东北侏罗系页岩储层为例

IF 4.7 3区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY
China Geology Pub Date : 2025-04-25 DOI:10.31035/cg2024221
Yong Ma , Cheng-yu Yang , Da-hua Li , Hong-wei Zhao , Zhe-jun Pan , Yong-shui Zhou , Dai-duo Zhu , Ning-ning Zhong
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引用次数: 0

摘要

底栖双壳类动物是自中生代以来分布最广泛的软体动物,它们的化石残骸经常生活在富含有机物的页岩附近或混杂的环境中。近期四川盆地侏罗系页岩油勘探发现,生物碎屑层具有丰富的双壳类化石,与页岩关系密切,具有重要的油气潜力。然而,这些双壳类化石的微观结构及其在油气储存和运移中的作用仍然知之甚少。本文采用二维成像(薄片、扫描电镜)、三维重建(FIB-SEM)和渗透率模拟相结合的方法,对川东北地区中下侏罗统生物碎屑页岩双壳壳微孔隙度进行了表征。壳化石中的微孔半径在100 ~ 1000nm之间,在壳内部呈网格状均匀分布,为液态烃的宿主。生物碎屑碳酸盐层整体孔隙度约为0.8%。与现存双壳类壳的对比分析表明,这些微孔是珠光砖壁结构的残余孔。由于双壳类化石及其微孔珍珠层取向规则,沿长双壳类化石轴的渗透系数比沿短双壳类化石轴的渗透系数高3 ~ 5倍。这些生物碎屑化石壳内的残余微孔对页岩油气的储集和运移都有积极的影响,使含生物碎屑化石页岩成为类似沉积环境下页岩油气勘探的有希望的“甜点”。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Genetic relationship between shell fossils and shale oil: A case study of Jurassic shale reservoir in the northeast Sichuan Basin
Benthic bivalves, the most widely distributed mollusks since the Mesozoic era, often inhabited environments where their fossilized remains are found adjacent to or intermingled with organic-rich shale. Recent Jurassic shale oil exploration in the Sichuan Basin has revealed that bioclastic layers, composed of abundant fossil bivalves and closely associated with shales and, exhibit significant hydrocarbon potentials. However, the microscopic structures of these bivalve fossils and their role in hydrocarbon storage and migration remain poorly understood. In this study, we characterized the microporosity of bivalve shells within the Middle-Lower Jurassic bioclastic shale in the northeastern Sichuan Basin using a combination of 2D imaging (thin section, SEM), 3D reconstruction (FIB-SEM), and permeability simulation. The micropores within the shell fossils range from 100 to 1000 nm in radius and are uniformly distributed in a grid-like pattern within the shell interior, where they host liquid hydrocarbons. The bioclastic carbonate layers exhibit an overall porosity of approximately 0.8%. Comparative analysis with extant bivalve shells suggests that these micropores represent residual pores from the nacreous brick wall structure. Due to the regular orientation of the shells and their microporous nacres, permeability coefficients along the long bivalve fossil axes are three to five times higher than those along the short axes. These residual micropores within the bioclastic fossil shells have a positive influence on both the storage and migration of shale oil and gas, making bioclastic fossil-bearing shalespromising sweet spots for shale oil and gas exploration in similar sedimentary environments.
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来源期刊
China Geology
China Geology GEOLOGY-
CiteScore
7.80
自引率
11.10%
发文量
275
审稿时长
16 weeks
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