Characteristics and Evolution of Low-Rank Coal Pore Structure Around the First Coalification Jump: Case Study in Southeastern Junggar Basin

Jia, TengFei; Zhang, Songhang; Tang, Shuheng; Wang, Meng; Di, Xin; Zhang, Qian

doi:10.1007/s11053-022-10094-z

Cited by 10 publications

(10 citation statements)

References 53 publications

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“…In addition, the hysteresis loop formed by the adsorption and desorption curves of nitrogen can reflect the pore structure of coal. The desorption and adsorption curves of samples W1–5, W1–8a, and W1–8b are almost overlapped (Figure a–c), without evident hysteresis loops, indicating that their pore types primarily consist of one-end closed pores and parallel plate pores. − However, for sample W2–8, a relatively prominent hysteresis loop is observed when P / P 0 ranges from 0.5 to 1 (Figure d), indicating that in addition to one-end closed pores, there are typical bottle-shaped pores in the sample. , …”

Section: Resultsmentioning

confidence: 96%

Estimation of Adsorption Isotherm for Deep Coalbed Methane: A Monolayer-Filling Model Based on Pore Fractal Dimension

Feng,

Li,

Tang

et al. 2024

Energy Fuels

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Understanding the state of adsorbed methane in coal under high temperatures and pressures is crucial for the exploration and production of deep coalbed methane (CBM). However, the commonly used isothermal adsorption models are inadequate in describing the complex adsorption behavior of methane with multiple occurrence states. Moreover, these models have limited applicability under high-temperature and highpressure conditions, restricting our understanding of the absorptivity and occurrence mechanism of deep CBM. To address this gap, low-temperature nitrogen adsorption and methane isothermal adsorption experiments under high-temperature and high-pressure conditions were carried out on four high-rank coal samples from the deep CBM block of Daning-Jixian in China's Ordos Basin. Based on the experimental results, a novel methane isothermal adsorption model combining the pore fractal dimension of coal was constructed, and the model exhibits good applicability in studying the adsorption behavior of methane in high-rank coal samples from a deep CBM reservoir. As the pressure increases, the monolayer adsorption amount of methane continues to rise slowly after reaching a certain value, while the adsorption amount in micropores decreases gradually after the pressure exceeds about 12 MPa. This phenomenon can be attributed to the transfer of methane molecules from the micropore filling area to the monolayer adsorption area at high pressures. Furthermore, it is found that the coal in the study area exhibits significant adsorption heterogeneity, with variations in adsorption capacity due to differences in coal composition and pore structure as well as varying degrees of coalification. The adsorption process of methane during the pressure rise can be categorized into three stages: a rapid increase in adsorption amount, conversion of micropore filling to monolayer adsorption, and final stabilization stage.

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Section: Resultsmentioning

confidence: 96%

Estimation of Adsorption Isotherm for Deep Coalbed Methane: A Monolayer-Filling Model Based on Pore Fractal Dimension

Feng,

Li,

Tang

et al. 2024

Energy Fuels

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“…When P / P 0 was greater than 0.9, the amount of N 2 adsorbed increased rapidly, indicating that capillary condensation occurred . Therefore, the LT-N 2 GA isothermal adsorption curves belonged to type IV isotherms. , Second, the desorption and adsorption branches of some samples did not overlap at high pressure, indicating that hysteresis loops existed. According to the delineation by IUPAC, the hysteresis loops can be classified into three types .…”

Section: Resultsmentioning

confidence: 99%

Pore Structure and Adsorption Characteristics of Maceral Groups: Insights from Centrifugal Flotation Experiment of Coals

et al. 2023

Self Cite

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Coal has various types of macerals, which have different pore structures and adsorption properties that change with coal’s thermal metamorphism. In-depth study of the characteristics of different coal macerals, especially the pore structure and adsorption properties, can better predict the coal reservoir gas storage capacity and migration ability. In this study, the sub-samples enriched in a specific maceral group with different coal ranks and particle sizes were obtained by centrifugal flotation experiments. Then, experiments containing low-temperature N2 isotherm adsorption (LT-N2GA), low-temperature CO2 isotherm adsorption (LT-CO2GA), and methane isothermal adsorption were carried out on the sub-samples to quantitatively analyze the evolution characteristics of pore structure and adsorption properties of different maceral groups. The results showed the following: (1) The separation effect of the light maceral groups by centrifugal flotation experiments increased with the decrease of particle sizes, which were treated with the heavy liquid of low and medium densities, while that of the heavy maceral groups had the relatively best separation effect in the particle sizes of 0.1–0.125 mm, which were treated with the heavy liquid of high densities. (2) The vitrinite-enriched samples had more ultra-micropores (mainly within the diameter range of 0.4–0.65 nm), while the inertinite enriched samples had more mesopores and transition pores (mainly within the diameter range of 40–50 nm). (3) For the low-rank coal, inertinite had more potential methane adsorption capacity. However, for the medium- and high-rank coal, vitrinite had more potential methane adsorption capacity. (4) For the low-rank coal, the adsorption potential and adsorption space increased with the increase of the inertinite content, while the adsorption potential, adsorption space, and surface free energy for the medium- and high-rank coal increased with the increase of vitrinite content. It is expected that the results can deepen the understanding about the gas storage capacity and migration ability and be used in the prevention of gas outburst and the reduction of carbon emission.

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“…However, at 10 μm resolution, the pore shape factor decreased to 0.025–0.04, while the coordination number increased to 1.18 . The study of pore structure of coal showed that the stronger the heterogeneity of coal was, the more irregular the pore shape was, and the larger was the connected pore space . In addition, Jiao et al obtained the shape factors of different pore types in Longmaxi shale using FE-SEM images and found that the shape factors of organic pores were the largest (0.73) followed by IntraP pores (0.43) and InterP pores (0.37).…”

Section: Resultsmentioning

confidence: 99%

“…31 The study of pore structure of coal showed that the stronger the heterogeneity of coal was, the more irregular the pore shape was, and the larger was the connected pore space. 77 In addition, Jiao et al 78 obtained the shape factors of different pore types in Longmaxi shale using FE-SEM images and found that the shape factors of organic pores were the largest (0.73) followed by IntraP pores (0.43) and InterP pores (0.37). In other words, the organic pores had the lowest complexity, and InterP pores had the highest complexity.…”

Section: The Effect Of Pore Connectivity Of Shale and Its Components ...mentioning

confidence: 99%

Controlling Effect of Shale Pore Connectivity on the Adsorption State of Shale Gas: A Case Study of Continental Shale of Jurassic Ziliujing Formation, Sichuan Basin

Bai,

Duan,

Gao

et al. 2023

Energy Fuels

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The pore connectivity of shale directly affects the migration and distribution of oil and gas within shale reservoirs and controls the adsorption state of shale gas by determining the accessible pore spaces for methane molecules. However, previous studies mostly focused on the surficial properties, pore size, and specific surface area, ignoring the significant impact of pore connectivity on the adsorption state of shale gas. Accordingly, taking the continental shale of the Jurassic Ziliujing Formation from the northeastern Sichuan Basin as the research object, this study mainly investigates the effects of shale pore connectivity on the adsorption state of shale gas by conducting methane adsorption and field emission scanning electron microscopy experiments together with image processing software. The results show that the methane adsorption capacity per unit specific surface area of type III kerogen is higher than that of type II 2 kerogen, indicating type III kerogen has a stronger affinity to methane. However, the total methane adsorption capacity of type II 2 kerogen in Ziliujing Formation shale samples is about four times that of type III kerogen, which is due to the much higher specific surface area, providing more methane adsorption sites. The development of OM and clay minerals in the shale of the Ziliujing Formation has a certain orientation and promotes the pore connectivity of the shale. Furthermore, a better pore connectivity of shale samples, which is usually accompanied by more developed microfractures of OM and clay minerals, higher roughness of pore surface, and stronger randomness of pore arrangement, results in a stronger methane adsorption capacity. Based on the close relationship between pore connectivity and methane adsorption capacity, a new pore connectivity index is proposed, considering the difference between the actual and the theoretical methane adsorption capacity of shale samples. Finally, a shale methane adsorption model is established based on pore connectivity.

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Characteristics and Evolution of Low-Rank Coal Pore Structure Around the First Coalification Jump: Case Study in Southeastern Junggar Basin

Cited by 10 publications

References 53 publications

Estimation of Adsorption Isotherm for Deep Coalbed Methane: A Monolayer-Filling Model Based on Pore Fractal Dimension

Estimation of Adsorption Isotherm for Deep Coalbed Methane: A Monolayer-Filling Model Based on Pore Fractal Dimension

Pore Structure and Adsorption Characteristics of Maceral Groups: Insights from Centrifugal Flotation Experiment of Coals

Controlling Effect of Shale Pore Connectivity on the Adsorption State of Shale Gas: A Case Study of Continental Shale of Jurassic Ziliujing Formation, Sichuan Basin

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