Physical characteristics of high-rank coal reservoirs in different coal-body structures and the mechanism of coalbed methane production

Xiao-dong, Zhang; Du, Zhigang; Li, Pengpeng

doi:10.1007/s11430-016-5178-y

Cited by 32 publications

(24 citation statements)

References 17 publications

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“…Generally, the higher the vitrinite content, the larger the SSA of super-micropores, the stronger the adsorption capacity, the stronger the Knudsen diffusion, and the weaker the Fick diffusion. Research has shown that the Fick diffusion is considerably larger than the Knudsen diffusion [56]. The effective diffusion coefficient, therefore, negatively correlates with the SSA of super-micropores.…”

Section: Discussionmentioning

confidence: 98%

Effects of Pore Structures of Different Maceral Compositions on Methane Adsorption and Diffusion in Anthracite

et al. 2019

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The pore structure of coal reservoirs is the main factor influencing the adsorption–diffusion rates of coalbed methane. Mercury intrusion porosimetry (MIP), low-pressure nitrogen adsorption (LP-NA), low-pressure carbon dioxide adsorption (LP-CA), and isothermal adsorption experiments with different macerals were performed to characterize the comprehensive pore distribution and methane adsorption–diffusion of coal. On the basis of the fractal theory, the pore structures determined through MIP and LP-NA can be combined at a pore diameter of 100 nm to achieve a comprehensive pore structural splicing of MIP, LP-NA, and LP-CA. Macro–mesopores and micro-transitional pores had average fractal dimensions of 2.48 and 2.18, respectively. The Langmuir volume (VL) and effective diffusion coefficients (De) varied from 31.55 to 38.63 cm3/g and from 1.42 to 2.88 × 10−5 s−1, respectively. The study results showed that for super-micropores, a higher vitrinite content led to a larger specific surface area (SSA) and stronger adsorption capacity but also to a weaker diffusion capacity. The larger the average pore diameter (APD) of micro-transitional pores, the stronger the diffusion capacity. The diffusion capacity may be controlled by the APD of micro-transitional pores.

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Section: Discussionmentioning

confidence: 98%

Effects of Pore Structures of Different Maceral Compositions on Methane Adsorption and Diffusion in Anthracite

et al. 2019

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“…The SSA of samples was calculated using the BET multipoint method (Liu et al., 2018), and the pore size distribution characteristics were calculated using the BJH method according to the desorption branch of LP-N 2 GA test (Okolo et al., 2015). According to the previous decimal pore classification standard (Zhang et al., 2017), the pore structure can be divided as follows: macropores (>1000 nm), mesopores (100–1000 nm), transition pores (10–100 nm), and micropores (<10 nm).…”

Section: Analysis Of Pore Structure Changementioning

confidence: 99%

Experimental investigation on the effect of ethanol on micropore structure and fluid distribution of coalbed methane reservoir

Zhou

Zhang²,

Lai

et al. 2020

Energy Exploration & Exploitation

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The development of coalbed methane not only ensures the supply of natural gas but also reduces the risks of coal mine accidents. The micropore structure of coalbed methane reservoir affects the seepage of coalbed methane; improvement of pore structure is one of the effective methods to enhance the efficiency of coalbed methane exploitation. In this study, low-pressure nitrogen gas adsorption, specific surface area analysis, nuclear magnetic resonance spectroscopy, and centrifugation experiment were used to evaluate the effect of ethanol on coal microscopic pore structure and fluid distribution during hydraulic fracturing. Seven coal samples were collected from the No. 3 coal seam in Zhaozhuang Mine, Qinshui Basin. The samples are mainly composed of micropores, transition pores, and mesopores. The experimental results show that ethanol can significantly change the pore structure by increasing the pore diameter. The average specific surface area, pore volume, and pore diameter of rock samples before ethanol immersion are 1.1270 m2/g, 0.0104 cm3/g, and 14.20 nm, respectively. The three parameters of rock samples after ethanol immersion are 0.5865 m2/g, 0.0025 cm3/g, and 29.37 nm. Ethanol improves the connectivity between micropores and mesopores. The average irreducible fluid saturation of samples saturated with formation water after centrifugation is 86%, and the average irreducible fluid saturation of samples soaked in three concentrations of ethanol solution decreases. It is considered that an ethanol solution of 0.4% concentration has the best effect on improving the pore structure and fluid distribution.

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“…The Advection-Diffusion Equation for Mass Transfer. Generally, gas transport in porous media can be considered as a mass transfer process [20][21][22], which can be expressed by the advection-diffusion equation…”

Section: Governing Equation For Gasmentioning

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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Physical characteristics of high-rank coal reservoirs in different coal-body structures and the mechanism of coalbed methane production

Cited by 32 publications

References 17 publications

Effects of Pore Structures of Different Maceral Compositions on Methane Adsorption and Diffusion in Anthracite

Effects of Pore Structures of Different Maceral Compositions on Methane Adsorption and Diffusion in Anthracite

Experimental investigation on the effect of ethanol on micropore structure and fluid distribution of coalbed methane reservoir

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

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