Bi-Fractal Characterization of the Pore Network of Tight Sandstone

Fluid seepage performance and accumulation in tight sandstone is a critical research topic for in-depth exploration and development, closely related to the heterogeneity of the pore network. The fractal characterization is one of the most compelling and direct ways for quantitative investigation of...

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Autores principales:	Zezhang Song, Junyi Zhao, Yuanyin Zhang, Dailin Yang, Yunlong Wang, Li Hu, Chenghai Li, Wenlei Liu
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	bi-fractal analysis pore structure tight sandstone Xujiahe formation central Sichuan basin Science Q
Acceso en línea:	https://doaj.org/article/db8230efaab141ba9510e5572f7a6d6c
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spelling	oai:doaj.org-article:db8230efaab141ba9510e5572f7a6d6c2021-12-01T19:51:53ZBi-Fractal Characterization of the Pore Network of Tight Sandstone2296-646310.3389/feart.2021.751944https://doaj.org/article/db8230efaab141ba9510e5572f7a6d6c2021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/feart.2021.751944/fullhttps://doaj.org/toc/2296-6463Fluid seepage performance and accumulation in tight sandstone is a critical research topic for in-depth exploration and development, closely related to the heterogeneity of the pore network. The fractal characterization is one of the most compelling and direct ways for quantitative investigation of heterogeneity. However, only one kind of fractal is used in most studies, and the differences and relations between different fractal dimensions are rarely discussed. This paper chose one of the most representative tight sandstone formations in China, the second member of the Xujiahe Formation, as the research object. First, based on physical analysis and XRD analysis, we carried out a qualitative investigation on pore structure utilizing thin-section and scanning electron microscopy. Then, detailed pore structure parameters were obtained using high-pressure mercury intrusion (HPMI). Lastly, we combined two-dimensional fractal analysis on thin-section images and three-dimensional fractal analysis on HPMI data to characterize the pore network heterogeneity quantitatively. The Xu2 tight sandstone is mainly medium- to fine-grained lithic feldspathic sandstone or feldspathic lithic sandstone with low porosity and permeability. Also, the Xujiahe tight sandstone is mainly composed of quartz, feldspar, and clay. The pore types of Xu2 tight sandstones are primarily intergranular pores, micro-fractures, and intra- and intergranular dissolution pores. Moreover, most of the micro-fractures in gas-bearing formation are open-ended, while most are filled by clay minerals in the dry formation. The r50 (median pore radius) is the most sensitive parameter to seepage capability (permeability) and gas-bearing status. The 2D fractal dimension (Ds) of gas-bearing samples is significantly larger than that of dry samples, while the 3D fractal dimension (D1, D2) of gas-bearing samples is lower than that of dry samples. There is a strong negative correlation between D2 and gas-bearing status, permeability, quartz content, and r50, but a positive correlation between Ds and these parameters. D2 represents the heterogeneity of pore space, while the Ds indicates the development of the pore network. Tectonic movements that generate micro-fractures and clay cementation that blocks the seepage channels are the two main controlling factors on fractal dimensions. Combining 2D and 3D fractal analysis could give a more in-depth investigation of pore structure.Zezhang SongZezhang SongJunyi ZhaoJunyi ZhaoYuanyin ZhangDailin YangYunlong WangLi HuChenghai LiWenlei LiuFrontiers Media S.A.articlebi-fractal analysispore structuretight sandstoneXujiahe formationcentral Sichuan basinScienceQENFrontiers in Earth Science, Vol 9 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	bi-fractal analysis pore structure tight sandstone Xujiahe formation central Sichuan basin Science Q
spellingShingle	bi-fractal analysis pore structure tight sandstone Xujiahe formation central Sichuan basin Science Q Zezhang Song Zezhang Song Junyi Zhao Junyi Zhao Yuanyin Zhang Dailin Yang Yunlong Wang Li Hu Chenghai Li Wenlei Liu Bi-Fractal Characterization of the Pore Network of Tight Sandstone
description	Fluid seepage performance and accumulation in tight sandstone is a critical research topic for in-depth exploration and development, closely related to the heterogeneity of the pore network. The fractal characterization is one of the most compelling and direct ways for quantitative investigation of heterogeneity. However, only one kind of fractal is used in most studies, and the differences and relations between different fractal dimensions are rarely discussed. This paper chose one of the most representative tight sandstone formations in China, the second member of the Xujiahe Formation, as the research object. First, based on physical analysis and XRD analysis, we carried out a qualitative investigation on pore structure utilizing thin-section and scanning electron microscopy. Then, detailed pore structure parameters were obtained using high-pressure mercury intrusion (HPMI). Lastly, we combined two-dimensional fractal analysis on thin-section images and three-dimensional fractal analysis on HPMI data to characterize the pore network heterogeneity quantitatively. The Xu2 tight sandstone is mainly medium- to fine-grained lithic feldspathic sandstone or feldspathic lithic sandstone with low porosity and permeability. Also, the Xujiahe tight sandstone is mainly composed of quartz, feldspar, and clay. The pore types of Xu2 tight sandstones are primarily intergranular pores, micro-fractures, and intra- and intergranular dissolution pores. Moreover, most of the micro-fractures in gas-bearing formation are open-ended, while most are filled by clay minerals in the dry formation. The r50 (median pore radius) is the most sensitive parameter to seepage capability (permeability) and gas-bearing status. The 2D fractal dimension (Ds) of gas-bearing samples is significantly larger than that of dry samples, while the 3D fractal dimension (D1, D2) of gas-bearing samples is lower than that of dry samples. There is a strong negative correlation between D2 and gas-bearing status, permeability, quartz content, and r50, but a positive correlation between Ds and these parameters. D2 represents the heterogeneity of pore space, while the Ds indicates the development of the pore network. Tectonic movements that generate micro-fractures and clay cementation that blocks the seepage channels are the two main controlling factors on fractal dimensions. Combining 2D and 3D fractal analysis could give a more in-depth investigation of pore structure.
format	article
author	Zezhang Song Zezhang Song Junyi Zhao Junyi Zhao Yuanyin Zhang Dailin Yang Yunlong Wang Li Hu Chenghai Li Wenlei Liu
author_facet	Zezhang Song Zezhang Song Junyi Zhao Junyi Zhao Yuanyin Zhang Dailin Yang Yunlong Wang Li Hu Chenghai Li Wenlei Liu
author_sort	Zezhang Song
title	Bi-Fractal Characterization of the Pore Network of Tight Sandstone
title_short	Bi-Fractal Characterization of the Pore Network of Tight Sandstone
title_full	Bi-Fractal Characterization of the Pore Network of Tight Sandstone
title_fullStr	Bi-Fractal Characterization of the Pore Network of Tight Sandstone
title_full_unstemmed	Bi-Fractal Characterization of the Pore Network of Tight Sandstone
title_sort	bi-fractal characterization of the pore network of tight sandstone
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/db8230efaab141ba9510e5572f7a6d6c
work_keys_str_mv	AT zezhangsong bifractalcharacterizationoftheporenetworkoftightsandstone AT zezhangsong bifractalcharacterizationoftheporenetworkoftightsandstone AT junyizhao bifractalcharacterizationoftheporenetworkoftightsandstone AT junyizhao bifractalcharacterizationoftheporenetworkoftightsandstone AT yuanyinzhang bifractalcharacterizationoftheporenetworkoftightsandstone AT dailinyang bifractalcharacterizationoftheporenetworkoftightsandstone AT yunlongwang bifractalcharacterizationoftheporenetworkoftightsandstone AT lihu bifractalcharacterizationoftheporenetworkoftightsandstone AT chenghaili bifractalcharacterizationoftheporenetworkoftightsandstone AT wenleiliu bifractalcharacterizationoftheporenetworkoftightsandstone
_version_	1718404602731167744

Bi-Fractal Characterization of the Pore Network of Tight Sandstone

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