Shale Heterogeneity in Western Hunan and Hubei: A Case Study from the Lower Silurian Longmaxi Formation in Well Laidi 1 in the Laifeng-Xianfeng Block, Hubei Province

Shale heterogeneity directly determines the alteration ability and gas content of shale reservoirs, and its study is a core research topic in shale gas exploitation and development. In this study, the shale from the Longmaxi Formation from well Ld1 located in western Hunan and Hubei is investigated. The shale’s heterogeneity is analyzed based on shale mineral rocks, microslices, geochemistry, and low-temperature N2 adsorption-desorption. It is found that the shales of the Longmaxi Formation from well Ld1 are mainly composed of siliceous shale, mixed shale, and clayey shale. The three types of shale facies exhibit strong heterogeneity in terms of the occurrence state of organic matter, organic content, mineral composition, microstructure and structure, brittleness, and micropore type. Sedimentation, late diagenesis, and terrigenous input are the main factors influencing the shale’s heterogeneity. With a total organic carbon (TOC) of 0.41%-4.18% and an organic matter maturity ( R o ) of 3.09%-3.42%, the shales of the Longmaxi Formation from well Ld1 are in an overmature stage, and their mineral composition is mainly quartz (5%-66%) and clay minerals (17.8%-73.8%). The main pore types are intergranular pores, intragranular pores, microfractures, and organic pores. The results of the low-temperature N2 adsorption-desorption experiment show that the shale pores are mainly composed of micropores and mesopores with narrow throats and complex structures, and their main morphology is of a thin-necked and wide-body ink-bottle pore. Based on the Frenkel-Halsey-Hill (FHH) model, the pore fractal dimension is studied to obtain the fractal dimension D 1 (2.73-2.76, mean 2.74) under low relative pressure ( P / P 0 ≤ 0.5 ) and D 2 (2.80-2.89, mean 2.85) under high relative pressure ( P / P 0 > 0.5 ). The shales of the Longmaxi Formation in the study area have a strong adsorption and gas storage capacity; however, the pore structure is complex and the connectivity is poor, which, in turn, imposes high requirements on reservoir reformation measures during exploitation. Moreover, the fractal dimension has a positive correlation with organic matter abundance, TOC, clay mineral content, and pyrite content and a negative correlation with quartz content. Since the organic matter contained in the shales of the Longmaxi Formation in the study area is in the overmature stage, the adsorption capacity of the shales is reduced, and the controlling effect of organic matter abundance on the same is not apparent.

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Nano-Scale Pore Structure and Its Multi-Fractal Characteristics of Tight Sandstone by N2 Adsorption/Desorption Analyses: A Case Study of Shihezi Formation from the Sulige Gas Filed, Ordos Basin, China

Minerals ◽

10.3390/min10040377 ◽

2020 ◽

Vol 10 (4) ◽

pp. 377

Author(s):

Zhelin Wang ◽

Xuewei Jiang ◽

Mao Pan ◽

Yongmin Shi

Keyword(s):

Fractal Dimension ◽

Specific Surface ◽

Pore Structure ◽

Surface Area ◽

Mineral Composition ◽

Fractal Dimensions ◽

Contribution Rate ◽

Tight Sandstone ◽

N2 Adsorption ◽

Adsorption Desorption

Fractal dimension is a critical parameter to evaluate the heterogeneity of complex pore structure in tight sandstone gas and other low permeability reservoirs. To quantify the fractal dimension of tight sandstone at various pore size classes and evaluate their implications on mineral composition and nano pore structure parameters, we conducted an integrated approach of N2 adsorption/desorption experiment (N2-GA), X-ray diffraction (X-RD), and field emission scanning electron microscopy (FE-SEM) on Sulige tight sandstone reservoirs. By comparing the nine types of fractal dimensions calculated from N2 adsorption data, we put forward the concept of “concentrated” fractal dimensions and “scattered” fractal dimensions (DN2, DN3, DN5, DN7 and DN8) for the first time according to its concentration extent of distribute in different samples. Result shows that mineral composition has a significant influence of a different level on specific surface area (SSA), pore volume (PV), and fractal dimensions (DN), respectively, where the “scattered” fractal dimension is more sensitive to certain specific property of the reservoir, including mineral content and the specific surface area contribution rate (Sr) of type II mesopores (Mesopore-II: 10~50nm). In addition, three type of hysteresis loops were distinguished corresponding to different pore shape combination of N2-GA isotherm curve, which reveals that pore structure heterogeneity is mainly controlled by inkbottle-shaped pores and the volume contribution rate (Vr) of mesopores in this study area. These findings could contribute to a better understanding of the controlling effect of pore heterogeneity on natural gas storage and adsorption.

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Accumulation Factors Analysis of Coal-Bearing Strata Shale Gas in Qinshui Basin

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.868.121 ◽

2013 ◽

Vol 868 ◽

pp. 121-124 ◽

Cited By ~ 1

Author(s):

Jun Yuan ◽

Yan Bin Wang ◽

Xin Zhang ◽

Jing Jing Fan ◽

Pei Xue

Keyword(s):

Organic Matter ◽

Mineral Composition ◽

Shale Gas ◽

Vitrinite Reflectance ◽

Qinshui Basin ◽

Factors Analysis ◽

Upper Paleozoic ◽

Organic Matter Type ◽

Organic Matter Abundance

The Shanxi and Taiyuan formations in Permo-Carboniferous of upper Paleozoic Erathem of Qinshui Basin, not only has abundant coal and CBM resources, also has a lot of shales. By analyzing the shale thickness, organic matter type, organic matter abundance, vitrinite reflectance, mineral composition of the Permo-Carboniferous coal-bearing strata, considered that the shale thickness of coal-bearing strata in the Qinshui Basin is larger, the organic matter abundance is general, but maturity is high and full of rich brittle mineral. It is in favor of late fracturing.

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Micropore Structural Heterogeneity of Siliceous Shale Reservoir of the Longmaxi Formation in the Southern Sichuan Basin, China

Minerals ◽

10.3390/min9090548 ◽

2019 ◽

Vol 9 (9) ◽

pp. 548 ◽

Cited By ~ 8

Author(s):

Li ◽

Tang ◽

Zheng

Keyword(s):

High Pressure ◽

Fractal Dimension ◽

Low Temperature ◽

Shale Gas ◽

Sichuan Basin ◽

Nitrogen Adsorption ◽

Structural Heterogeneity ◽

Longmaxi Formation ◽

Shale Reservoir ◽

Siliceous Shale

In recent years, the shale gas in the southern Sichuan Basin has achieved great commercial development, and the Silurian Longmaxi Formation is the main development stratum. In order to solve the problems of great difference production and inaccurate gas content of the Longmaxi Formation shale gas field in the southern Sichuan Basin, based on thin section identification, argon ion polishing-field emission scanning electron microscopy, high pressure mercury injection, low temperature nitrogen adsorption and the fractal method, the micropore structural heterogeneity of the siliceous shale reservoir of the Longmaxi Formation has been studied. The results show the following: The pores of siliceous shale are mainly intergranular pores and organic pores. Image analysis shows that there are obvious differences in size and distribution of shale pores among different types. The micropore structural heterogeneity is as follows: intragranular pore > intergranular pore > organic pore. In the paper, the combination of low temperature nitrogen adsorption method and high-pressure mercury injection method is proposed to characterize the micropore size distribution and fractal dimension, which ensures the credibility of pore heterogeneity. The shale pores are mainly composed of mesopores (2–20 nm), followed by macropores (100–300 nm). For different pore sizes, the fractal dimension from large to small is mesopore, micropore and macropore. Shale pore structure and fractal dimension are correlated with mineral composition and total organic carbon (TOC) content, but the correlation is significantly different in different areas, being mainly controlled by the sedimentary environment and diagenesis.

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Research On the Fractal Dimensions of the Organic-Rich Shale Pores Via Different Models

Journal of Physics Conference Series ◽

10.1088/1742-6596/2152/1/012020 ◽

2022 ◽

Vol 2152 (1) ◽

pp. 012020

Author(s):

Fangyao Dai

Keyword(s):

Fractal Dimension ◽

Gas Adsorption ◽

Fractal Theory ◽

Fractal Dimensions ◽

Fractal Model ◽

Relative Pressure ◽

Longmaxi Formation ◽

High Relative Pressure ◽

Adsorption Data ◽

Different Dimensions

Abstract Fractal dimension can be used to the pore surface characterize. For pore structures in different sizes, the calculation models of fractal theory should be distinguished due to the different principles of the gas adsorption experiments. To further study the adaptability of the fractal model for gas adsorption experimental data, the author collected shale samples of Longmaxi formation from Well JY1, then CO2 and N2 adsorption provided the PSD curves. In addition, the fractal dimensions of micropore and mesopore were calculated by the Jaroniec fractal model and Frenkel–Halsey–Hill (FHH) fractal model respectively. The research shows that the Jaroniec model may be suitable to calculate CO2 adsorption data and could characterize the fractal dimension of micropore, while the FHH model may be suitable to calculate N2 adsorption data in the high relative pressure region. It suggests that the micropore and mesopore could have different dimensions and the evaluation of the structure in shale pores should consider both of them.

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The Effect of Thermal Modification on the Development of Carbon Material Microporous Structure

Journal of Vasyl Stefanyk Precarpathian National University ◽

10.15330/jpnu.1.1.41-53 ◽

2014 ◽

Vol 1 (1) ◽

pp. 41-53

Author(s):

B.K. Ostafiychuk ◽

I.M. Budzulyak ◽

N.Ya. Ivanichok ◽

B.I. Rachiy ◽

R.P. Lisovsky

Keyword(s):

Low Temperature ◽

Carbon Material ◽

Total Pore Volume ◽

Micropore Volume ◽

Thermal Modification ◽

Porous System ◽

Microporous Structure ◽

N2 Adsorption ◽

Adsorption Desorption ◽

System Characteristics

A research is done to characterize the microporous structure of outgoing and thermally modified (673 K, 180 min) plant-extracted carbon material. The porous system characteristics are worked out by different methods on low temperature (77K) N2 adsorption-desorption based isotherm. It is stated that thermal modification contributes to the enlargement of specific surface (from 361 m2/g to 673 m2/g), an increase in total pore volume (from 0,166 cm3/g to 0,477 cm3/g) and an increase in micropore volume (from 0,127 cm3/g to 0,173 cm3/g). Most effectively thermal modification is apt to form nanopores with diameters of 0,75; 1,25 and 4 nm.

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Adsorption Characteristics of Oxytetracycline by Different Fractions of the Organic Matter from Humus Soil: Insight from Internal Structure and Composition

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph17030914 ◽

2020 ◽

Vol 17 (3) ◽

pp. 914

Author(s):

Mengya Luo ◽

Shengke Yang ◽

Siqi Shen ◽

Yu Li

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Adsorption Capacity ◽

Internal Structure ◽

Batch Experiments ◽

N2 Adsorption ◽

Sem Images ◽

Organic Fractions ◽

Adsorption Desorption ◽

Humus Soil

For minimizing the transport of antibiotics to groundwater, the migration of antibiotics in soils should be investigated. Soil organic matter can affect the migration of antibiotics. To date, the influence of aromatics and aliphatic content of organic matter on the adsorption of antibiotics has been controversial. To better understand the reaction mechanism of soil organic matter with antibiotics, this study investigated the adsorption of oxytetracycline (OTC) by humus soils (HOS) and their fractions. HOS were sequentially fractionated into four organic fractions, including the removal of dissolved organic matter (HRDOM), removal of minerals (HRM), removal of free fat (HRLF), and nonhydrolyzable organic carbon (HNHC). Moreover, batch experiments revealed that adsorption capacity was ordered by HNHC > HOS > HRDOM > HRLF > HRM. SEM images and N2 adsorption/desorption isotherms indicate that adsorption capacity is independent of the external structure. However, adsorption capacity is related to the internal structure and composition. Combination analysis with elemental composition and infrared spectroscopy showed that the adsorption capacity of HRM, HRLF, and HNHC had a good positive correlation with aromaticity, but a negative correlation with polarity and hydrophilicity. Additionally, the rule of binding affinity between OTC and functional groups with different properties was summarized as aromatic > polarity > hydrophilic.

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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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Shale Gas Resources Evaluation of the Songliao Basin

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.508.129 ◽

2014 ◽

Vol 508 ◽

pp. 129-132

Author(s):

Xin Zhang ◽

Jun Yuan ◽

Pei Xue ◽

Jing Jing Fan ◽

Jin Wang

Keyword(s):

Organic Matter ◽

Mineral Composition ◽

Shale Gas ◽

Upper Cretaceous ◽

Oil And Gas ◽

Vitrinite Reflectance ◽

Songliao Basin ◽

Resources Evaluation ◽

Organic Matter Type ◽

Organic Matter Abundance

The Qingshankou and Nenjiang group in upper cretaceous of Songliao basin is a set of dark shale. Analyze the shale thickness, organic matter type, organic matter abundance, vitrinite reflectance, mineral composition of the permo-carboniferous coal-bearing strata. Consider that the thickness of shale in the Songliao basin is larger, despite the organic matter abundance is good, but maturity is lower, less of the formation of oil and gas.

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