Variation in Pore Structure and Associated Fractal Dimensions of Barakar and Barren Measures Carbon-Rich Gas Shales of Jharia Basin, India

The characteristics of the nanopore structure in shale, tight sandstone and mudstone from the Ordos Basin of China were investigated by X-ray diffraction (XRD) analysis, porosity and permeability tests and low-pressure nitrogen adsorption experiments. Fractal dimensions D1 and D2 were determined from the low relative pressure range (0 < P/P0 < 0.4) and the high relative pressure range (0.4 < P/P0 < 1) of nitrogen adsorption data, respectively, using the Frenkel–Halsey–Hill (FHH) model. Relationships between pore structure parameters, mineral compositions and fractal dimensions were investigated. According to the International Union of Pure and Applied Chemistry (IUPAC) isotherm classification standard, the morphologies of the nitrogen adsorption curves of these 14 samples belong to the H2 and H3 types. Relationships among average pore diameter, Brunner-Emmet-Teller (BET) specific surface area, pore volume, porosity and permeability have been discussed. The heterogeneities of shale nanopore structures were verified, and nanopore size mainly concentrates under 30 nm. The average fractal dimension D1 of all the samples is 2.1187, varying from 1.1755 to 2.6122, and the average fractal dimension D2 is 2.4645, with the range from 2.2144 to 2.7362. Compared with D1, D2 has stronger relationships with pore structure parameters, and can be used for analyzing pore structure characteristics.

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

Minerals ◽

10.3390/min9020127 ◽

2019 ◽

Vol 9 (2) ◽

pp. 127 ◽

Cited By ~ 6

Author(s):

Zhuo Li ◽

Zhikai Liang ◽

Zhenxue Jiang ◽

Fenglin Gao ◽

Yinghan Zhang ◽

...

Keyword(s):

Fractal Dimension ◽

Pore Structure ◽

Fractal Dimensions ◽

Organic Medium ◽

Songliao Basin ◽

Sem Images ◽

Fractal Characteristics ◽

Inorganic Mineral ◽

Nanopore Structure ◽

High Fractal Dimension

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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Quantification of the influences of radiolarian fossils on the pore structure of Wufeng-Lungmachi gas shales (Ordovician-Silurian) in the Sichuan Basin, South China

Journal of Natural Gas Science and Engineering ◽

10.1016/j.jngse.2020.103442 ◽

2020 ◽

Vol 81 ◽

pp. 103442

Author(s):

Ruining Hu ◽

Jingqiang Tan ◽

Jeffrey Dick ◽

Lei Li ◽

Wenhui Wang

Keyword(s):

Pore Structure ◽

South China ◽

Sichuan Basin ◽

Gas Shales ◽

The Sichuan Basin

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Evaluation Shale Pore Size Spectrum Using Mercury Porosimetry and Nitrogen Adsorption Experiment: A Case Study from the Longtan Formation Shale, Southeastern Hunan, China

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.962-965.34 ◽

2014 ◽

Vol 962-965 ◽

pp. 34-40

Author(s):

Ning Yang ◽

Shu Heng Tang ◽

Song Hang Zhang ◽

Jun Jie Yi

Keyword(s):

Pore Structure ◽

Parallel Plate ◽

Mercury Porosimetry ◽

Nitrogen Adsorption ◽

Size Spectrum ◽

Adsorption Experiment ◽

Structure Characteristics ◽

Gas Shales ◽

Strong Ability

Gas shales have a complex pore structure. Using mercury porosimetry and nitrogen adsorption experiment on shale of Longtan Formation in southeastern of Hunan, the pore structure characteristics were contrast analyzed, influencing factors and its impact on reservoir-forming were discussed. Longtan Formation shale is composed of nanopores, include the cylinder pores with two ends open and parallel-plate pores with four sides open. The efficiency of mercury ejection ranges 31.45%~63.82%, 51.94% on average, pores uniformity is well. The size of nanopores is 5~30nm, taking up 94.74% of the total volume and 98.08% of specific surface area. Brittle minerals content is high, as an important parameter influencing pore development. The nanopores have a strong ability to absorb gas, methane molecule exist in a structured way.

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Nano/Micro Pore Structure and Fractal Characteristics of Baliancheng Coalfield in Hunchun Basin

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2021.18729 ◽

2021 ◽

Vol 21 (1) ◽

pp. 682-692

Author(s):

Youzhi Wang ◽

Cui Mao

Keyword(s):

Fractal Dimension ◽

Specific Surface ◽

Pore Structure ◽

Surface Area ◽

Specific Surface Area ◽

Pore Diameter ◽

Fractal Dimensions ◽

Nitrogen Adsorption ◽

Average Pore ◽

Coal Reservoir

The pore structure characteristic is an important index to measure and evaluate the storage capacity and fracturing coal reservoir. The coal of Baliancheng coalfield in Hunchun Basin was selected for experiments including low temperature nitrogen adsorption method, Argon Ion milling Scanning Electron Microscopy (Ar-SEM), Nuclear Magnetic Resonance (NMR), X-ray diffraction method, quantitative mineral clay analysis method. The pore structure of coal was quantitatively characterized by means of fractal theory. Meanwhile, the influences of pores fractal dimension were discussed with experiment data. The results show that the organic pores in Baliancheng coalfield are mainly plant tissue pores, interparticle pores and gas pores, and the mineral pores are corrosion pores and clay mineral pores. There are mainly slit pore and wedge-shaped pore in curve I of Low temperature nitrogen adsorption. There are ink pores in curve II with characteristics of a large specific surface area and average pore diameter. The two peaks of NMR T2 spectrum indicate that the adsorption pores are relatively developed and their connectivity is poor. The three peaks show the seepage pores and cracks well developed, which are beneficial to improve the porosity and permeability of coal reservoir. When the pore diameter is 2–100 nm, the fractal dimensions D1 and D2 obtained by nitrogen adsorption experiment. there are positive correlations between water content and specific surface area and surface fractal dimension D1, The fractal dimension D2 was positively and negatively correlated with ash content and average pore diameters respectively. The fractal dimensions DN1 and DN2 were obtained by using the NMR in the range of 0.1 μm˜10 μm. DN1 are positively correlated with specific surface area of adsorption pores. DN2 are positively correlated volume of seepage pores. The fractal dimension DM and dissolution hole fractal dimension Dc were calculated by SEM image method, respectively controlled by clay mineral and feldspar content. There is a remarkable positive correlation between D1 and DN1 and Langmuir volume of coal, so fractal dimension can effectively quantify the adsorption capacity of coal.

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3D Visualization and Classification of Pore Structure and Pore Filling in Gas Shales

10.2118/134582-ms ◽

2010 ◽

Cited By ~ 10

Author(s):

Carl Sisk ◽

Elizabeth Diaz ◽

Joel Walls ◽

Avrami Grader ◽

Michael Suhrer

Keyword(s):

Pore Structure ◽

3D Visualization ◽

Pore Filling ◽

Gas Shales

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Pore Structure and Fractal Characteristics of Organic-Rich Lacustrine Shales of the Kongdian Formation, Cangdong Sag, Bohai Bay Basin

Frontiers in Earth Science ◽

10.3389/feart.2021.760583 ◽

2021 ◽

Vol 9 ◽

Author(s):

Shouxu Pan ◽

Ming Zha ◽

Changhai Gao ◽

Jiangxiu Qu ◽

Xiujian Ding

Keyword(s):

Organic Matter ◽

Specific Surface ◽

Pore Structure ◽

Surface Area ◽

Clay Minerals ◽

Mineral Composition ◽

Fractal Dimensions ◽

Nitrogen Adsorption ◽

Thermal Maturity ◽

Pore Types

In order to examine the pore structure and reveal the fractal geometric nature of shales, a series of laboratory experiments were conducted on lacustrine shale samples cored from the Kongdian Formation. Based on the low temperature nitrogen adsorption, fluorescent thin section and field emission scanning electronic microscope, a comprehensive pore structure classification and evaluation were conducted on shale samples. Fractal dimensions D1 and D2 (with relative pressure of 0–0.45 and 0.45–1.00, respectively) were obtained from the nitrogen adsorption data using the fractal Frenkel-Halsey-Hill (FHH) method. With additional means of X-ray diffraction analysis, total organic carbon content analysis and thermal maturity analysis, the relationships between pore structure parameters, fractal dimensions, TOC content and mineral composition are presented and discussed in this paper. The results show that interparticle pores and microfractures are predominant, whereas organic matter pores are rarely found. The pore morphology is primarily featured with wide-open ends and slit-shaped structures. In terms of pore scale, mesopores and macropores are predominant. The value of fractal dimension D1 representing small pores ranges from 2.0173 to 2.4642 with an average of 2.1735. The value of D2 which represents large pores ranges from 2.3616 to 2.5981 with an average of 2.4960. These low numbers are an indication of few pore types and relatively low heterogeneity. In addition, smaller D1 values reveal that large pores have more complicated spatial structures than smaller ones. The results of correlation analysis show that: 1) D2 is correlated positively with specific surface area but negatively with average pore diameter; 2) D1 and D2 literally show no obvious relationship with mineral composition, TOC content or vitrinite reflectance (Ro); 3) both total Barrett-Joyner-Halenda (BJH) volume and specific surface area show a positive relationship with dolomite content and a negative relationship with felsic minerals content. These results demonstrate that the pore types are relatively few and dominated by mesopores, and the content of brittle minerals such as dolomite and felsic minerals control the pore structure development whilst organic matter and clay minerals have less influence due to low thermal maturity and abundance of clay minerals.

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Quantitative Characterization of Heterogeneity in Different Reservoir Spaces of Low-Permeability Sandstone Reservoirs and Its Influence on Physical Properties

Advances in Civil Engineering ◽

10.1155/2021/2399016 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Fengjuan Dong ◽

Na Liu ◽

Zhen Sun ◽

Xiaolong Wei ◽

Haonan Wang ◽

...

Keyword(s):

Fractal Dimension ◽

Pore Structure ◽

Fractal Theory ◽

Fractal Dimensions ◽

Low Permeability ◽

Quantitative Characterization ◽

Average Value ◽

Porosity And Permeability ◽

Sandstone Reservoirs

The complex pore structure of low-permeability sandstone reservoir makes it difficult to characterize the heterogeneity of pore throat. Taking the reservoir of Sanjianfang formation in QL oilfield as an example, the fractal dimension of different storage spaces is calculated by using fractal theory based on casting thin section, scanning electron microscope, and high-pressure mercury injection, and the correlation between porosity, permeability, and contribution of different storage space permeabilities is analyzed. The results show that the reservoir of Sanjianfang formation in QL oilfield mainly develops small pores, fine pores, and micropores, and the fractal dimension of micropore structure is between 2.6044 and 2.9982, with an average value of 2.8316. The more complex the pore structure is, the stronger the microheterogeneity is. The higher the fractal dimension, the more complex the pore structure and the smaller the porosity and permeability. The fractal dimensions of small pores, fine pores, and micropores increase successively with the decrease in pore radius, and the microstructure heterogeneity of large pores is weaker than that of small pores. It provides a theoretical basis for the exploration and development of low-permeability sandstone reservoirs.

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Fractal Characteristics of Pores in the Longtan Shales of Guizhou, Southwest China

Geofluids ◽

10.1155/2020/8834758 ◽

2020 ◽

Vol 2020 ◽

pp. 1-16

Author(s):

Yuqi Huang ◽

Peng Zhang ◽

Jinchuan Zhang ◽

Xuan Tang ◽

Chengwei Liu ◽

...

Keyword(s):

Organic Matter ◽

Fractal Dimension ◽

Pore Structure ◽

Shale Gas ◽

Storage Capacity ◽

Evaluation Criteria ◽

Fractal Dimensions ◽

Gas Absorption ◽

Relative Pressure ◽

And Storage

The pore structure of marine-continental transitional shales from the Longtan Formation in Guizhou, China, was investigated using fractal dimensions calculated by the FHH (Frenkel-Halsey-Hill) model based on low-temperature N2 adsorption data. Results show that the overall D 1 (fractal dimension under low relative pressure, P / P 0 ≤ 0.5 ) and D 2 (fractal dimension under high relative pressure, P / P 0 > 0.5 ) values of Longtan shales were relatively large, with average values of 2.7426 and 2.7838, respectively, indicating a strong adsorption and storage capacity and complex pore structure. The correlation analysis of fractal dimensions with specific surface area, average pore size, and maximum gas absorption volume indicates that D 1 can comprehensively characterize the adsorption and storage capacity of shales, while D 2 can effectively characterize the pore structure complexity. Further correlation among pore fractal dimension, shale organic geochemical parameters, and mineral composition parameters shows that there is a significant positive correlation between fractal dimensions and organic matter abundance as well as a complex correlation between fractal dimension and organic matter maturity. Fractal dimensions increase with an increase in clay mineral content and pyrite content but decrease with an increase in quartz content. Considering the actual geological evaluation and shale gas exploitation characteristics, a lower limit for D 1 and upper limit for D 2 should be set as evaluation criteria for favorable reservoirs. Combined with the shale gas-bearing property test results of Longtan shales in Guizhou, the favorable reservoir evaluation criteria are set as D 1 ≥ 2.60 and D 2 ≤ 2.85 . When D 1 is less than 2.60, the storage capacity of the shales is insufficient. When D 2 is greater than 2.85, the shale pore structure is too complicated, resulting in poor permeability and difficult exploitation.

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Fractal analysis of pore structures in graphene oxide-carbon nanotube based cementitious pastes under different ultrasonication

Nanotechnology Reviews ◽

10.1515/ntrev-2019-0010 ◽

2019 ◽

Vol 8 (1) ◽

pp. 107-115 ◽

Cited By ~ 12

Author(s):

Yuan Gao ◽

Hongwen Jing ◽

Zefu Zhou

Keyword(s):

Graphene Oxide ◽

Fractal Dimension ◽

Pore Structure ◽

Pore Size ◽

Size Range ◽

Fractal Dimensions ◽

Pore Characteristics ◽

Pore Structures ◽

Cement Additive ◽

Multi Walled Carbon Nanotubes

Abstract Nano cement additive using a hybrid of graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) combines the excellent affinity of GO and the superior mechanical properties of MWCNTs. Ultrasonication is the key process to disperse the GO/MWCNTs and further optimizes the pore structures of cement-based pastes. Fractal dimension can effectively and quantitatively characterize the pore structures of cementitious composites. The present study investigates the fractal dimensions of pore structures of GO/MWCNT-OPC pastes under power- and time-controlled ultrasonication based on the mercury intrusion porosimetry (MIP) tests data. The finding of this study shows that comparing to calculating the fractal dimension of the overall pore size range, assessing the variations of fractal dimension of individual pore size range is more effective in evaluating the pore characteristic. The fractal dimension of larger capillary pores $$\left( {{D}_{>{{10}^{4}}nm}} \right)$$can be use to describe the change of pore structure of GO/MWCNT-OPC pastes under ultrasonication treatment with sufficient accuracy as higher value of $${{D}_{>{{10}^{4}}nm}}$$indicates better pore characteristics. The fractal dimension change trend of mesopores is always opposite to that of bigger capillary pores. Modest increment in both power- and time-controlled ultrasonication seems to result in the increase of the fractal dimension of capillary pores and lead to better reinforcement effects. Prolongation of ultrasonication time slightly influences the pore structure of the specimens, while nano cement additives exposed to excess ultrasonication power fail to afford adequate reinforcing effect and finally cause the deterioration of the pore structures. The findings of this study can provide helpful information of GO/MWCNT-OPC pastes and ultrasonication treatment in the future.

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