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Pore structure and influencing factors of shell-clay mixed shale: a case study from the Da’anzhai member in Longgang area,northern Sichuan Basin
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Jiayan XIN1, Haihua ZHU1, Minglei WANG2, Benjian ZHANG3, Zhongbao WU2, Libin WANG2, Chunyu QIN3, Yucong LI3
Journal of Palaeogeography (Chinese Edition) | 2026, 28(2) : 568 - 581
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Journal of Palaeogeography (Chinese Edition) | 2026, 28(2): 568-581
• OIL AND GAS GEOLOGY •
Pore structure and influencing factors of shell-clay mixed shale: a case study from the Da’anzhai member in Longgang area,northern Sichuan Basin
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Jiayan XIN1, Haihua ZHU1, Minglei WANG2, Benjian ZHANG3, Zhongbao WU2, Libin WANG2, Chunyu QIN3, Yucong LI3
Affiliations
  • 1 School of Geoscience and Technology,Southwest Petroleum University,Chengdu 610500, China
  • 2 Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083, China
  • 3 Research Institute of Petroleum Exploration and Development,PetroChina Southwest Oil & Gas Field Company,Chengdu 610041,China
  • XIN Jiayan,born in 1998,is a master degree candidate. Her main research direction is reservoir geology. E-mail: .

About Author:

XIN Jiayan,born in 1998,is a master degree candidate. Her main research direction is reservoir geology. E-mail: .

Published: 2026-04-01 doi: 10.7605/gdlxb.2026.058
Outline
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To investigate the pore structure characteristics of the shale oil reservoir in the Jurassic Da’anzhai Member in Longgang area,northern Sichuan Basin,a systematic analysis of pore features and their controlling factors in the Da’anzhai shale was conducted using organic carbon analysis,field emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD),nitrogen adsorption,and nuclear magnetic resonance(NMR)experiments. The results indicate that: (1)The pore types in the Da’anzhai shale oil reservoir are dominated by clay mineral intercrystalline pores,followed by calcite intercrystalline pores,quartz intercrystalline pores,with minor organic matter pores and pyrite intercrystalline pores. (2)Clay content controls the pore volume and specific surface area of the shale,while organic matter content has minimal influence on porosity. (3)Calcite intercrystalline pores primarily contribute to larger pores but are limited in number and volume. Microscopically,these pores are mainly found within biogenic shells,with the shell edges being dense and non-porous. The low degree of asphalt filling and poor connectivity are notable. The development of calcite intercrystalline pores is controlled by shell recrystallization,with larger shells being more prone to recrystallization and forming intercrystalline porosity. (4)Authigenic quartz intercrystalline pores are distributed along shell edges,exhibiting better connectivity than calcite intercrystalline pores. These pores formed earlier than the hydrocarbon generation stage of organic matter and are often filled with hydrocarbons,contributing significantly to effective storage space. Their development is controlled by the degree of silicification of shells,with larger shells more susceptible to replacement,forming quartz intercrystalline pores. (5)The mixing of clay and shells results in a distinct “binary” structure in the reservoir space: clay-rich areas are characterized by pores with high specific surface area,small pore size,and good adsorption capacity,while shell-rich areas are dominated by pores with low specific surface area,large pore size,but limited connectivity.

pore structure  /  nitrogen adsorption  /  nuclear magnetic resonance  /  shale oil  /  Da’anzhai member  /  Sichuan Basin
辛佳艳, 祝海华, 王明磊, 张本健, 吴忠宝, 汪莉彬, 秦春雨, 李育聪. 介壳-黏土混积页岩孔隙结构及影响因素: 以川北龙岗地区大安寨段为例*. 古地理学报, 2026 , 28 (2) : 568 -581 . DOI: 10.7605/gdlxb.2026.058
Jiayan XIN, Haihua ZHU, Minglei WANG, Benjian ZHANG, Zhongbao WU, Libin WANG, Chunyu QIN, Yucong LI. Pore structure and influencing factors of shell-clay mixed shale: a case study from the Da’anzhai member in Longgang area,northern Sichuan Basin[J]. Journal of Palaeogeography (Chinese Edition), 2026 , 28 (2) : 568 -581 . DOI: 10.7605/gdlxb.2026.058
  • National Natural Science Foundation of China(42202176)
  • PetroChina-Southwest Petroleum University Innovation Consortium Science and Technology Cooperation Project(2020CX050103)
Year 2026 volume 28 Issue 2
142
61
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Article Info
doi: 10.7605/gdlxb.2026.058
  • Receive Date:2025-07-14
  • Online Date:2026-09-24
  • Published:2026-04-01
Article Data
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History
  • Received:2025-07-14
  • Revised:2025-10-20
Funding
National Natural Science Foundation of China(42202176)
PetroChina-Southwest Petroleum University Innovation Consortium Science and Technology Cooperation Project(2020CX050103)
Affiliations
    1 School of Geoscience and Technology,Southwest Petroleum University,Chengdu 610500, China
    2 Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083, China
    3 Research Institute of Petroleum Exploration and Development,PetroChina Southwest Oil & Gas Field Company,Chengdu 610041,China

Corresponding:

ZHU Haihua,born in 1987,a master supervisor,is mainly engaged in research on oil and gas reservoir evaluation. E-mail: .
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表12种不同金属材料的力学参数
科
Family
属数
Number of
genus
种数
Number of
species
占总种数比例
Percentage of
total species (%)
属
Genus
种数
Number of
species
占总种数比例
Percentage of total
species (%)
鹅膏菌科Amanitaceae 2 11 5.26 鹅膏菌属 Amanita 10 4.78
小菇科 Mycenaceae 2 12 5.74 丝盖伞属 Inocybe 5 2.39
多孔菌科 Polyporaceae 8 14 6.70 蜡蘑属 Laccaria 5 2.39
红菇科 Russulaceae 3 23 11.00 小皮伞属 Marasmius 6 2.87
小菇属 Mycena 11 5.26
光柄菇属 Pluteus 5 2.39
红菇属 Russula 17 8.13
栓菌属 Trametes 5 2.39
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