Differences of Pore Features in Marine Shales between Lower Cambrian and Lower Silurian Formations of Upper Yangtze Area, South China

Lower Cambrian shale and lower Silurian shale are both typical of oil-prone kerogen and siliceous composition, but different in thermal maturities. Porosity differences were determined in marine shales between the two shales. Measurements were utilized including organic geochemistry, XRD, scanning e...

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Main Authors: Minghui Li, Mingliang Li, Haiping Huang, Lei Gong, Debao Zheng
Format: Article
Language:English
Published: MDPI AG 2022-01-01
Series:Energies
Subjects:
Online Access:https://www.mdpi.com/1996-1073/15/3/820
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author Minghui Li
Mingliang Li
Haiping Huang
Lei Gong
Debao Zheng
author_facet Minghui Li
Mingliang Li
Haiping Huang
Lei Gong
Debao Zheng
author_sort Minghui Li
collection DOAJ
description Lower Cambrian shale and lower Silurian shale are both typical of oil-prone kerogen and siliceous composition, but different in thermal maturities. Porosity differences were determined in marine shales between the two shales. Measurements were utilized including organic geochemistry, XRD, scanning electron microscopy (SEM) and N<sub>2</sub> gas adsorption. Pore volume (PV) of lower Silurian shale was approximately 1.5 times higher than that of lower Cambrian shale, and pore surface area (PSA) of lower Silurian shale was almost 2.5 times higher than that of lower Cambrian shale. Lower Cambrian shale and lower Silurian shale possess similar materials, but distinctive thermal degrees. Evolution mechanisms of different types of pores, especially organic matter (OM)-hosted pores, may trigger this different pore features. Pores of rigid framework are the residue of primary interparticle pores during the burial history. Pores associated with clay flakes can be preserved well adjacent to rigid grains or secondary minerals acting as rigid frameworks or grain supporters. Dissolved pores in both lower Cambrian shale and lower Silurian shale barely contribute to the total porosity and mean little to the permeability. Both excessive OM content and over thermal maturity are detrimental to development of OM-hosted pores. Rigid particles, clay flakes, and OM commonly co-exist within shale matrix. Rigid grains act as supporters, clay flakes confine ample space, and OM first migrates into and provides secondary OM-hosted pores. In this condition, pores can be preserved owing to associating matrix with good mechanic and chemical stability. The significant differences of structural settings result into various hydrocarbon explosion efficiency and different pressure circumstance, which consequently leads to the different pore features between the two shales. For lower Cambrian shale, overpressure circumstance diminish if hydrocarbon expels outside of the shale system, and OM-hosted pores destroy through compaction. Sustaining overpressure and abundant residue hydrocarbon (migrated OM) make positive contributions to the pore properties, in terms of numbers, diameters and connectivity of the lower Silurian shale samples.
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spelling doaj.art-495b7180cea0417ca634d5e2481f89bb2023-11-23T16:20:32ZengMDPI AGEnergies1996-10732022-01-0115382010.3390/en15030820Differences of Pore Features in Marine Shales between Lower Cambrian and Lower Silurian Formations of Upper Yangtze Area, South ChinaMinghui Li0Mingliang Li1Haiping Huang2Lei Gong3Debao Zheng4School of Energy Resource, China University of Geosciences (Beijing), Beijing 100083, ChinaProduction Operation Department, Qinghe Oil Production Plant of Sinopec Shengli Oilfield Co., Ltd., Weifang 262714, ChinaSchool of Energy Resource, China University of Geosciences (Beijing), Beijing 100083, ChinaBohai-Rim Energy Research Institute, Northeast Petroleum University, Qinhuangdao 066004, ChinaDownhole Operations Company, Daqing Oilfield, CNPC, Daqing 163453, ChinaLower Cambrian shale and lower Silurian shale are both typical of oil-prone kerogen and siliceous composition, but different in thermal maturities. Porosity differences were determined in marine shales between the two shales. Measurements were utilized including organic geochemistry, XRD, scanning electron microscopy (SEM) and N<sub>2</sub> gas adsorption. Pore volume (PV) of lower Silurian shale was approximately 1.5 times higher than that of lower Cambrian shale, and pore surface area (PSA) of lower Silurian shale was almost 2.5 times higher than that of lower Cambrian shale. Lower Cambrian shale and lower Silurian shale possess similar materials, but distinctive thermal degrees. Evolution mechanisms of different types of pores, especially organic matter (OM)-hosted pores, may trigger this different pore features. Pores of rigid framework are the residue of primary interparticle pores during the burial history. Pores associated with clay flakes can be preserved well adjacent to rigid grains or secondary minerals acting as rigid frameworks or grain supporters. Dissolved pores in both lower Cambrian shale and lower Silurian shale barely contribute to the total porosity and mean little to the permeability. Both excessive OM content and over thermal maturity are detrimental to development of OM-hosted pores. Rigid particles, clay flakes, and OM commonly co-exist within shale matrix. Rigid grains act as supporters, clay flakes confine ample space, and OM first migrates into and provides secondary OM-hosted pores. In this condition, pores can be preserved owing to associating matrix with good mechanic and chemical stability. The significant differences of structural settings result into various hydrocarbon explosion efficiency and different pressure circumstance, which consequently leads to the different pore features between the two shales. For lower Cambrian shale, overpressure circumstance diminish if hydrocarbon expels outside of the shale system, and OM-hosted pores destroy through compaction. Sustaining overpressure and abundant residue hydrocarbon (migrated OM) make positive contributions to the pore properties, in terms of numbers, diameters and connectivity of the lower Silurian shale samples.https://www.mdpi.com/1996-1073/15/3/820marine shalelower Cambrianlower Silurianpore typespore propertiesporosity development mechanism
spellingShingle Minghui Li
Mingliang Li
Haiping Huang
Lei Gong
Debao Zheng
Differences of Pore Features in Marine Shales between Lower Cambrian and Lower Silurian Formations of Upper Yangtze Area, South China
Energies
marine shale
lower Cambrian
lower Silurian
pore types
pore properties
porosity development mechanism
title Differences of Pore Features in Marine Shales between Lower Cambrian and Lower Silurian Formations of Upper Yangtze Area, South China
title_full Differences of Pore Features in Marine Shales between Lower Cambrian and Lower Silurian Formations of Upper Yangtze Area, South China
title_fullStr Differences of Pore Features in Marine Shales between Lower Cambrian and Lower Silurian Formations of Upper Yangtze Area, South China
title_full_unstemmed Differences of Pore Features in Marine Shales between Lower Cambrian and Lower Silurian Formations of Upper Yangtze Area, South China
title_short Differences of Pore Features in Marine Shales between Lower Cambrian and Lower Silurian Formations of Upper Yangtze Area, South China
title_sort differences of pore features in marine shales between lower cambrian and lower silurian formations of upper yangtze area south china
topic marine shale
lower Cambrian
lower Silurian
pore types
pore properties
porosity development mechanism
url https://www.mdpi.com/1996-1073/15/3/820
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