Types and genesis of horizontal bedding of marine gas-bearing shale and its significance for shale gas：A case study of the Wufeng-Longmaxi shale in southern Sichuan Basin，China

被引：0
|
作者：
Shi Z. [1 ]
Zhao S. [1 ]
Zhou T. [1 ]
Sun S. [1 ]
Yuan Y. [3 ]
Zhang C. [2 ]
Li B. [2 ]
Qi L. [1 ]
机构：
[1] Research Institute of Petroleum Exploration and Development, PetroChina, Beijing
[2] Shale Gas Research Institute, Southwest Oil and Gas Field Company, PetroChina, Sichuan, Chengdu
[3] Zhejiang Oilfield Company, PetroChina, Zhejiang, Hangzhou
来源：
Oil and Gas Geology | 2023年 / 44卷 / 06期
关键词：
contourites; horizontal bedding; Paleozoic; pelagic sediments; southern Sichuan Basin; turbidites; Wufeng-Longmaxi Formations;
D O I：
10.11743/ogg20230613
中图分类号：
学科分类号：
摘要：
Shale has horizontal bedding of diverse origins in differential permeability. An integrated analysis of core data，full-diameter images of enlarged thin section and scanning electron microscope（SEM）images of argon-ion-milled samples，shows that the gas-bearing Wufeng-Longmaxi shale in southern Sichuan Basin develops four types of horizontal bedding，that is，grading type composed of claystone，grading type composed of siltstone and claystone，alternating siltstone and claystone type，and page type. The grading type of claystone constitutes the multi-layer superimposed siltstones in parallel，with siltstone and claystone depositing in graded bedding. The grading type composed of siltstone and claystone is composed of parallelly alternating silty and clayey beds，where the silty beds mainly in clast-supported texture，has abrupt boundary at the bottom and gradual contact with the clayey bed on top，featuring normal grading as a whole. The alternating siltstone and claystone type features abrupt contact between both beds and lamina with no grading. The page type constitutes parallel bedding of very thin clayey lamina with weakly normal grading. The four types of horizontal bedding are of different genesis. The grading type of claystone and grading type of siltstone and claystone are of relatively low-energy turbidite origin，with the former derived from even weaker hydrodynamic conditions；the alternating siltstone and claystone is of contourite origin such as shelf facies；and the page type is of pelagic origin from suspended sediment deposition. The horizontal bedding serves to directly affect shale permeability. The page type is characterized by the abundance of organic matter and organic pores，ranking top in permeability；the alternating siltstone and claystone type takes the second place in permeability with better sorting；while the two grading types come at last in permeability with poor sorting and low organic matter content. © 2023 Editorial Department of Oil and Gas Geology. All rights reserved.
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页码：1499 / 1514
页数：15
相关论文
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