Petrographic Controls on Pore and Fissure Characteristics of Coals from the Southern Junggar Coalfield, Northwest China

Zhou, Sandong; Liu, Dameng; Cai, Yidong; Karpyn, Zuleima T.; Yao, Yanbin

doi:10.3390/en11061556

Cited by 8 publications

(4 citation statements)

References 44 publications

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“…The exact sampling locations and the significance of their respective identification codes are graphically represented in Figure 2. The tiny pores and original fractures in the coal matrix jointly form the dual poresfractures system of coal [53][54][55]. Within this system, CBM primarily exists in an adsorbed state within the pores of the coal and migrates outward through the fracture network.…”

Section: Sampling Collection and Experimental Schemementioning

confidence: 99%

“…Subsequently, the pore structure data of coal samples were obtained by low-temperature liquid nitrogen adsorption, high-pressure MIP, and NMR. It is believed that these testing methods can complement The tiny pores and original fractures in the coal matrix jointly form the dual poresfractures system of coal [53][54][55]. Within this system, CBM primarily exists in an adsorbed state within the pores of the coal and migrates outward through the fracture network.…”

Section: Sampling Collection and Experimental Schemementioning

confidence: 99%

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Porosity Characteristics of Coal Seams and the Control Mechanisms of Coal Petrology in the Xishanyao Formation in the Western Part of the Southern Junggar Basin

Yuan,

Tang,

Tong

et al. 2024

Minerals

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The porosity characteristics of coal seams serve as a pivotal factor in assessing the development potential of coalbed methane (CBM) resources, significantly influencing the adsorption and permeability capabilities of coal reservoirs, as well as the accumulation, entrapment, and preservation of CBM. In this study, we focused on the coal seams of the Xishanyao Formation in the western part of the southern Junggar Basin (NW China). By leveraging the complementarity of nuclear magnetic resonance (NMR), low-temperature liquid nitrogen experiments, and high-pressure mercury intrusion porosimetry (MIP) in spatial exploration range and precision, we conducted a comprehensive analysis to achieve a fine description of porosity characteristics. Furthermore, we explored the coal petrology factors controlling the pore characteristics of the Xishanyao Formation, aiming to provide geological evidence for the selection of favorable areas and the development potential evaluation of CBM in the study area. The results indicate the following: (1) The total pore volume of the coal samples is 6.318 × 10−3 cm3/g on average, and the micropore volume accounts for a relatively high proportion (averaging 44.17%), followed by the fine pores (averaging 39.41%). The average porosity is approximately 3.87%, indicating good gas storage and connectivity of the coal seams, albeit with some heterogeneity. The coal reservoir is dominated by micropores and fine pores with diameters less than 100 nm, and the pore structure is characterized by low pore volume and high pore area. (2) The pore structure is influenced by both the coalification degree and the coal maceral. Within the range of low coalification, porosity increases with the increase in coalification degree. Building upon this, an increase in the vitrinite content promotes the development of micropores and fine pores, while an increase in the inertinite content promotes the development of meso–macropores. The clay mineral content exhibits a negative correlation with the adsorption pore volume ratio and a positive correlation with the seepage pore volume ratio.

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Section: Sampling Collection and Experimental Schemementioning

confidence: 99%

Section: Sampling Collection and Experimental Schemementioning

confidence: 99%

Porosity Characteristics of Coal Seams and the Control Mechanisms of Coal Petrology in the Xishanyao Formation in the Western Part of the Southern Junggar Basin

Yuan,

Tang,

Tong

et al. 2024

Minerals

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“…Previous investigations in the study area primarily focused on the CBM enrichment model and resource potential evaluation, but the research on the physical properties of coal reservoirs was insufficient (Fu et al, 2016b(Fu et al, , 2017bHou et al, 2021). The productivity and recovery efficiency of methane are significantly affected by the pore and fracture system of coal reservoirs (Zhou et al, 2018). Furthermore, in-depth research on the pore structure and its effect on adsorption and seepage of coal reservoirs in the southern Junggar Basin will contribute to future CBM exploration and development.…”

Section: Introductionmentioning

confidence: 99%

Fractal characterization of pore structure and its influence on CH4 adsorption and seepage capacity of low-rank coals

Hou

Zhang

et al. 2022

Front. Earth Sci.

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The pore structures of coal can directly affect the adsorption and seepage capacity of coalbed methane (CBM), which therefore is an important influence on CBM exploration and development. In this study, the pore structures of low-rank coals from the Middle Jurassic Xishanyao Formation in the southern Junggar Basin were analyzed, and the fractal dimensions (D1, D2, D3 and D4 corresponding to pore sizes of 0−5 nm, 5−100 nm, 100−1000 nm and 1000−20,000 nm, respectively) were calculated to quantitatively describe these coal pore structures. The results show that Xishanyao coal is characterized by open pore morphology, good pore connectivity and well-developed seepage pores and microfractures, which is beneficial to CBM seepage. The D1 and D2 can be used to characterize the pore surface and structure of adsorption pores respectively. The D3 and D4 can be used to represent the pore structure of seepage pores. Compared with adsorption pores, the structure of seepage pores is more affected by the change of coal rank. The D1 is better than D2 in characterizing the methane adsorption capacity. When D1 > 2.2, D1 is positively correlated with Langmuir volume (VL) and negatively correlated with Langmuir pressure (PL), while D2 shows a weak opposite trend. The coals with the higher D1 and lower D2 are associated with a higher VL, indicating the coal reservoir with more complex pore surfaces and simpler pore structures has stronger methane adsorption capacity. D4 is better than D3 in characterizing the methane seepage capacity. The porosity and permeability of coal reservoirs increases with the increase of D4, while D3 displays an opposite trend, which is mainly related to the well-developed microfractures. The well-developed fracture system enhances the seepage capacity of the Xishanyao coal reservoir. This study reveals the fractal characteristics of pore structure and its significant influence on adsorption and seepage capacity of low-rank coal.

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“…Coal is a kind of porous medium material, and its microscopic pore structure determines the adsorption, desorption, diffusion, seepage, and mechanical properties of coal. [1,2] The pore and fissure structure of a coal body has a significant influence on the exploitation, storage, migration, and spontaneous combustion tendency of coal, and it is also a key factor affecting the extractability of coalbed methane [3,4]. As early as the 1960s, domestic and foreign scholars have begun to study the micropore structure of coal.…”

Section: Introductionmentioning

confidence: 99%

Study on Pore and Fissure Structure Characteristics of Deep Soft Coal Rock

Zhang

Zhang³

et al. 2021

Geofluids

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The microscopic pore and fissure structure is the key factor affecting the exploitation, storage, and migration of coalbed methane and coal spontaneous combustion tendency. For further research of the microstructure of deep soft coal rock, such as pores and fissures, the coal samples from the Yangdong mining area were qualitatively and quantitatively analyzed in terms of morphological characteristics, pore shape, pore specific surface area, pore volume, and pore diameter by a scanning electron microscope (SEM) and a low-temperature liquid nitrogen adsorption experiment. The results show that there are three major categories and five minor categories of pores with different genetic types, including metamorphic pore, exogenous pore, and mineral pore, and there are endogenous fissures, exogenous tensile fissures, and exogenous shear fissures developed in the coal body. According to the results of the low-temperature liquid nitrogen adsorption experiment, the hysteresis curves of coal samples can be divided into two types. The I type curve produces a loop. There is a “hysteresis loop” which is obvious, and there is an inflection point that is not obvious. The pore system is mainly composed of open pores. The II type curve has no adsorption back line and no obvious inflection point. The pore structure is mainly composed of an impermeable hole closed at one end. The BET specific surface area of coal samples ranges from 0.2810 to 4.7569 m2/g, with an average of 1.27984 m2/g. The BJH pore volume ranges from 0.002864 to 0.007377 cm3/g, with an average of 0.0041246 cm3/g. The average BJH pore diameter of coal samples ranges from 4.3935 to 20.1501 nm, with an average of 16.0313 nm. The pore specific surface area of coal is mainly contributed by micropores, and the transition pores contribute the most to pore volume. The distribution of pore volume in each pore section of a coal sample has the rule that the transition pore is larger than the micropore, and the micropore is larger than the mesopore, and the maximum ratio is 66.2%. The distribution of pore specific surface area has the rule that the micropore is larger than the transition pore, and the transition pore is larger than the mesopore. The maximum ratio is 91.2%.

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Petrographic Controls on Pore and Fissure Characteristics of Coals from the Southern Junggar Coalfield, Northwest China

Cited by 8 publications

References 44 publications

Porosity Characteristics of Coal Seams and the Control Mechanisms of Coal Petrology in the Xishanyao Formation in the Western Part of the Southern Junggar Basin

Porosity Characteristics of Coal Seams and the Control Mechanisms of Coal Petrology in the Xishanyao Formation in the Western Part of the Southern Junggar Basin

Fractal characterization of pore structure and its influence on CH4 adsorption and seepage capacity of low-rank coals

Study on Pore and Fissure Structure Characteristics of Deep Soft Coal Rock

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