Continental shale pore structure characteristics and their controlling factors: A case study from the lower third member of the Shahejie Formation, Zhanhua Sag, Eastern China

Li, Tingwei; Jiang, Zhenxue; Li, Zhuo; Wang, Pengfei; Xu, Chengyun; Liu, Guoheng; Su, Siyuan; Ning, Chuanxiang

doi:10.1016/j.jngse.2017.06.005

Cited by 60 publications

(42 citation statements)

References 41 publications

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“…No obvious correlation was observed between multiscale pore volumes and carbonate components ( Figure 11J-L). IntraP pores can be formed due to the solubility of calcite, consequently, abundant calcite contents may play significant roles in pore development in organic shales [7,47,55]. Relatively small amount of calcite and dolomite with dissolved pores are identified in the Shahezi shales, which may be the cause of the scatter correlations in the plots of pore volumes against carbonate contents.…”

Section: The Impacts Of Lithofacies On Pore Structurementioning

confidence: 99%

The Impacts of Matrix Compositions on Nanopore Structure and Fractal Characteristics of Lacustrine Shales from the Changling Fault Depression, Songliao Basin, China

Liang

Jiang

et al. 2019

Minerals

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The Lower Cretaceous Shahezi shales are the targets for lacustrine shale gas exploration in Changling Fault Depression (CFD), Southern Songliao Basin. In this study, the Shahezi shales were investigated to further understand the impacts of rock compositions, including organic matters and minerals on pore structure and fractal characteristics. An integrated experiment procedure, including total organic carbon (TOC) content, X-ray diffraction (XRD), field emission-scanning electron microscope (FE-SEM), low pressure nitrogen physisorption (LPNP), and mercury intrusion capillary pressure (MICP), was conducted. Seven lithofacies can be identified according to on a mineralogy-based classification scheme for shales. Inorganic mineral hosted pores are the most abundant pore type, while relatively few organic matter (OM) pores are observed in FE-SEM images of the Shahezi shales. Multimodal pore size distribution characteristics were shown in pore width ranges of 0.5–0.9 nm, 3–6 nm, and 10–40 nm. The primary controlling factors for pore structure in Shahezi shales are clay minerals rather than OM. Organic-medium mixed shale (OMMS) has the highest total pore volumes (0.0353 mL/g), followed by organic-rich mixed shale (ORMS) (0.02369 mL/g), while the organic-poor shale (OPS) has the lowest pore volumes of 0.0122 mL/g. Fractal dimensions D1 and D2 (at relative pressures of 0–0.5 and 0.5–1 of LPNP isotherms) were obtained using the Frenkel–Halsey–Hill (FHH) method, with D1 ranging from 2.0336 to 2.5957, and D2 between 2.5779 and 2.8821. Fractal dimensions are associated with specific lithofacies, because each lithofacies has a distinctive composition. Organic-medium argillaceous shale (OMAS), rich in clay, have comparatively high fractal dimension D1. In addition, organic-medium argillaceous shale (ORAS), rich in TOC, have comparatively high fractal dimension D2. OPS shale contains more siliceous and less TOC, with the lowest D1 and D2. Factor analysis indicates that clay contents is the most significant factor controlling the fractal dimensions of the lacustrine Shahezi shale.

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Section: The Impacts Of Lithofacies On Pore Structurementioning

confidence: 99%

The Impacts of Matrix Compositions on Nanopore Structure and Fractal Characteristics of Lacustrine Shales from the Changling Fault Depression, Songliao Basin, China

Liang

Jiang

et al. 2019

Minerals

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“…5i), (a), (d) and (g) Graptolite fragments (BSE images for samples YJ1-04, WX2-04, and YJ1-01, respectively); (b) enlargement of the red frame area shown in (a) displaying the numerous honeycomb-like pyrite moulage pores on the graptolite periderm of YJ1-04; (c) Framboidal pyrite moulage pores and organic nanopores developed on the graptolite periderm of WX2-04; (e) enlargement of the red frame area shown in (d) displaying the numerous honeycomb-like pyrite moulage pores on the graptolite periderm of WX2-04; (f) enlargement of the red frame area shown in (e) in which the nanometer-sized OM pores were well developed in the moulage pore walls with elliptical or rounded cross sections, and the pore sizes ranged from 10 nm to 50 nm in WX2-04; (h) enlargement of the red frame area shown in (g) indicating that the nanoscale OM pores were locally developed on the graptolite periderm of YJ1-01; (i) enlargement of the red frame area shown in (h) indicating that the shapes of the OM pores were elliptical or rounded with pore sizes ranging between 10 and 50 nm in which were determined to be equivalent to dimensions of the OM pores in the moulage pores. It had been previously established that OM pores were created during hydrocarbon maturation (Loucks et al, 2009(Loucks et al, , 2012Jarvie et al, 2007;Milliken et al, 2013;Li et al, 2017). The results of previous studies also showed that the graptolite periderm was comprised primarily of an aromatic structure with aliphatic groups, which had a certain hydrocarbon generation potential and mainly generated gaseous hydrocarbons (Bustin et al, 1989;Briggs et al, 1995;Gupta et al, 2006;Shen et al, 2016).…”

Section: Organic Gas Poresmentioning

confidence: 89%

Graptolite‐Derived Organic Matter and Pore Characteristics in the Wufeng‐Longmaxi Black Shale of the Sichuan Basin and its Periphery

Zhou

Sun

et al. 2019

Acta Geologica Sinica (Eng)

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A key target of shale gas exploration and production in China is the organic‐rich black shale of the Wufeng Formation‐Longmaxi Formation in the Sichuan Basin and its periphery. The set of black shale contains abundant graptolites, which are mainly preserved as flattened rhabdosomes with carbonized periderms, is an important organic component of the shale. However, few previous studies had focused on the organic matter (OM) which is derived from graptolite and its pore structure. In particular, the contributions of graptolites to gas generation, storage, and flow have not yet been examined. In this study, focused ion beam‐scanning electron microscope (FIB‐SEM) was used to investigate the characteristics of the graptolite‐derived OM and the micro‐nanopores of graptolite periderms. The results suggested that the proportion of OM in the graptolite was between 19.7% and 30.2%, and between 8.9% and 14.4% in the surrounding rock. The total organic carbon (TOC) content of the graptolite was found to be higher than that of the surrounding rock, which indicated that the graptolite played a significant role in the dispersed organic matter. Four types of pores were developed in the graptolite periderm, including organic gas pores, pyrite moulage pores, authigenic quartz moldic pores, and microfractures. These well‐developed micro‐nano pores and fractures had formed an interconnected system within the graptolites which provided storage spaces for shale gas. The stacked layers and large accumulation of graptolites resulted in lamellation fractures openning easily, and provided effective pathways for the gas flow. A few nanoscale gas pores were observed in the graptolite‐derived OM, with surface porosity lie in 1.5%–2.4%, and pore diameters of 5–20 nm. The sapropel detritus was determined to be rich in nanometer‐sized pores with surface porosity of 3.1%–6.2%, and pore diameters of 20–80 nm. Due to the small amount of hydrocarbon generation of the graptolite, supporting the overlying pressure was difficult, which caused the pores to become compacted or collapsed.

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“…However, the samples with a calcite content <5 wt % show a negative correlation (Figure 9c). Therefore, we speculate that only a high concentration of calcite (over 20 wt %) plays significant roles in pore development and in the enhancement of pore connectivity [59,85].…”

Section: Effects Of Matrix Compositions On Pore Connectivitymentioning

confidence: 95%

Pore Connectivity Characterization of Lacustrine Shales in Changling Fault Depression, Songliao Basin, China: Insights into the Effects of Mineral Compositions on Connected Pores

Liang

Jiang

et al. 2019

Minerals

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Pore connectivity of lacustrine shales was inadequately documented in previous papers. In this work, lacustrine shales from the lower Cretaceous Shahezi Formation in the Changling Fault Depression (CFD) were investigated using field emission scanning electron microscopy (FE-SEM), mercury intrusion capillary pressure (MICP), low pressure gas (CO2 and N2) sorption (LPGA) and spontaneous fluid imbibition (SFI) experiments. The results show that pores observed from FE-SEM images are primarily interparticle (interP) pores in clay minerals and organic matter (OM) pores. The dominant pore width obtained from LPGA and MICP data is in the range of 0.3–0.7 nm and 3–20 nm. The slopes of n-decane and deionized (DI) water SFI are in the range of 0.34–0.55 and 0.22–0.38, respectively, suggesting a mixed wetting nature and better-connected hydrophobic pores than hydrophilic pores in the Shahezi shales. Low pore connectivity is identified by the dominant nano-size pore widths (0.3–20 nm), low DI water SFI slopes (around 0.25), high geometric tortuosity (4.75–8.89) and effective tortuosity (1212–6122). Pore connectivity follows the order of calcareous shale > argillaceous shale > siliceous shale. The connected pores of Shahezi shales is mainly affected by the high abundance and coexistence of OM pores and clay, carbonate minerals host pores.

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Continental shale pore structure characteristics and their controlling factors: A case study from the lower third member of the Shahejie Formation, Zhanhua Sag, Eastern China

Cited by 60 publications

References 41 publications

The Impacts of Matrix Compositions on Nanopore Structure and Fractal Characteristics of Lacustrine Shales from the Changling Fault Depression, Songliao Basin, China

The Impacts of Matrix Compositions on Nanopore Structure and Fractal Characteristics of Lacustrine Shales from the Changling Fault Depression, Songliao Basin, China

Graptolite‐Derived Organic Matter and Pore Characteristics in the Wufeng‐Longmaxi Black Shale of the Sichuan Basin and its Periphery

Pore Connectivity Characterization of Lacustrine Shales in Changling Fault Depression, Songliao Basin, China: Insights into the Effects of Mineral Compositions on Connected Pores

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