Pore structure and its impact on CH4 adsorption capacity and flow capability of bituminous and subbituminous coals from Northeast China

Cai, Yidong; Liu, Dameng; Pan, Zhejun; Yao, Yanbin; Li, Junqian; Qiu, Yongkai

doi:10.1016/j.fuel.2012.06.055

Cited by 577 publications

(385 citation statements)

References 42 publications

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“…The Langmuir volumes of the shale samples had a positive relationship with fractal dimension (Figure 14), which was consistent with many previous studies of coal and shale [13,14,37,45]. The higher fractal dimension values represented a rough and irregular surface, which provided more adsorption sites and resulted in higher adsorption capacity.…”

Section: Effects Of Fractal Dimension On the Adsorption Capacity Of Ssupporting

confidence: 89%

“…Mandelbrot first proposed fractal concepts and geometry for evaluating the complex shapes of objects found in nature [35] and the geometry of coal or shale pores is a typical example of such shapes. Many previous studies have used fractal theory to evaluate the pore heterogeneity of shale, coal, or sandstone [11][12][13][36][37][38][39]. Fractal dimension D is frequently used as a parameter to quantitatively characterize the heterogeneous pore structure of shale [40].…”

Section: Organic Geochemistrymentioning

confidence: 99%

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Pore Structure and Fractal Characteristics of Niutitang Shale from China

Tang

Wang

et al. 2018

Minerals

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A suite of shale samples from the Lower Cambrian Niutitang Formation in northwestern Hunan Province, China, were investigated to better understand the pore structure and fractal characteristics of marine shale. Organic geochemistry, mineralogy by X-ray diffraction, porosity, permeability, mercury intrusion and nitrogen adsorption and methane adsorption experiments were conducted for each sample. Fractal dimension D was obtained from the nitrogen adsorption data using the fractal Frenkel-Halsey-Hill (FHH) model. The relationships between total organic carbon (TOC) content, mineral compositions, pore structure parameters and fractal dimension are discussed, along with the contributions of fractal dimension to shale gas reservoir evaluation. Analysis of the results showed that Niutitang shale samples featured high TOC content (2.51% on average), high thermal maturity (3.0% on average), low permeability and complex pore structures, which are highly fractal. TOC content and mineral compositions are two major factors affecting pore structure but they have different impacts on the fractal dimension. Shale samples with higher TOC content had a larger specific surface area (SSA), pore volume (PV) and fractal dimension, which enhanced the heterogeneity of the pore structure. Quartz content had a relatively weak influence on shale pore structure, whereas SSA, PV and fractal dimension decreased with increasing clay mineral content. Shale with a higher clay content weakened pore structure heterogeneity. The permeability and Langmuir volume of methane adsorption were affected by fractal dimension. Shale samples with higher fractal dimension had higher adsorption capacity but lower permeability, which is favorable for shale gas adsorption but adverse to shale gas seepage and diffusion.

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Section: Effects Of Fractal Dimension On the Adsorption Capacity Of Ssupporting

confidence: 89%

Section: Organic Geochemistrymentioning

confidence: 99%

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Tang

Wang

et al. 2018

Minerals

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“…Generally, coal is characterized as a dual-pore system [6] including the matrix porosity consisting of micropores/ mesopores in the coal matrix (i.e., the porous material region) and the fracture porosity composed of nonuniformly distributed macropores and microfractures (i.e., the free flow region) [7]. The adsorption processes of methane in the reservoir can be divided into two parts: Enter the irregular macropore-microfractures system by advection-diffusion; diffuse in the nanopore network of a matrix, then adsorbed on the interior surface of pores.…”

Section: Introductionmentioning

confidence: 99%

“…As for the coal gas adsorption process, in general, it is considered as a physisorption process because the molecular forces involved are normally of the Van der Waals type [2,7]. Many studies, including both experiment and numerical simulation, have focused on (isothermal) adsorption equilibrium without concerning the intermediate states or time in recent years [11,18].…”

Section: Introductionmentioning

confidence: 99%

Multicomponent Lattice Boltzmann Simulations of Gas Transport in a Coal Reservoir with Dynamic Adsorption

et al. 2018

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Gas adsorption occurs when the dynamic adsorption equilibrium conditions of the local adsorptive sites are broken. In the overall process of unconventional natural gas generation, enrichment, storage, and production, this phenomenon plays a significant role. A double-distribution Lattice Boltzmann model for solving the coupled generalized Navier-Stokes equation and advection-diffusion equation with respect to the gas-solid dynamic adsorption process is proposed for multicomponent gas migration in the unconventional reservoir. The effective diffusion coefficient is introduced to the model of gas transport in the porous media. The Langmuir adsorption rate equation is employed to control the adsorption kinetic process of gas-solid adsorption/desorption. The model is validated in two steps through fluid flow without and with gas diffusion-adsorption between two parallel plates filled with porous media, respectively. Simulation results indicate that with other parameters being equal, the rate of gas diffusion in the porous material and the area of the dynamic adsorption equilibrium-associated region increase with the matrix porosity/permeability. Similar results will happen with a greater saturation adsorption amount or a lower Langmuir pressure. The geometric effect on adsorption is also studied, and it is found that a higher specific surface area or free flow region can enhance the gas transport and the rate of adsorption.

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“…Various pore characterization techniques have been applied to quantify the pore structures from total porosity, pore volume, pore size distribution (PSD), SSA, and so on [2,[9][10][11][12][13][14][15]. These include low-pressure gas (N 2 /CO 2 ) adsorption/desorption techniques [9][10][11][12], high-pressure mercury intrusion porosimetery (MIP) [12][13][14], ultra/small-angle neutron scattering (SANS) [15,16], focused ion beam scanning electron microscopy [17], field emission scanning electron microscopy/transmission electron microscopy [18], nuclear magnetic resonance [19,20], and X-ray computed tomography [17,19,20].…”

Section: Introductionmentioning

confidence: 99%

Changes in Pore Structure of Coal Caused by CS₂ Treatment and Its Methane Adsorption Response

et al. 2018

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The pore structure and gas adsorption are two key issues that affect the coal bed methane recovery process significantly. To change pore structure and gas adsorption, 5 coals with different ranks were treated by CS 2 for 3 h using a Soxhlet extractor under ultrasonic oscillation conditions; the evolutions of pore structure and methane adsorption were examined using a highpressure mercury intrusion porosimeter (MIP) with an AutoPore IV 9310 series mercury instrument. The results show that the cumulative pore volume and specific surface area (SSA) were increased after CS 2 treatment, and the incremental micropore volume and SSA were increased and decreased before and after R o,max = 1 3%, respectively; the incremental big pore (greater than 10 nm in diameter) volumes were increased and SSA was decreased for all coals, and pore connectivity was improved. Methane adsorption capacity on coal before and after R o,max = 1 3% also was increased and decreased, respectively. There is a positive correlation between the changes in the micropore SSA and the Langmuir volume. It confirms that the changes in pore structure and methane adsorption capacity due to CS 2 treatment are controlled by the rank, and the change in methane adsorption is impacted by the change of micropore SSA and suggests that the changes in pore structure are better for gas migration; the alteration in methane adsorption capacity is worse and better for methane recovery before and after R o,max = 1 3%. A conceptual mechanism of pore structure is proposed to explain methane adsorption capacity on CS 2 treated coal around the R o,max = 1 3%.

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Pore structure and its impact on CH4 adsorption capacity and flow capability of bituminous and subbituminous coals from Northeast China

Cited by 577 publications

References 42 publications

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Multicomponent Lattice Boltzmann Simulations of Gas Transport in a Coal Reservoir with Dynamic Adsorption

Changes in Pore Structure of Coal Caused by CS₂ Treatment and Its Methane Adsorption Response

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Pore structure and its impact on CH4 adsorption capacity and flow capability of bituminous and subbituminous coals from Northeast China

Cited by 577 publications

References 42 publications

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Multicomponent Lattice Boltzmann Simulations of Gas Transport in a Coal Reservoir with Dynamic Adsorption

Changes in Pore Structure of Coal Caused by CS2 Treatment and Its Methane Adsorption Response

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Changes in Pore Structure of Coal Caused by CS₂ Treatment and Its Methane Adsorption Response