Petrophysical characterization of high-rank coal by nuclear magnetic resonance: a case study of the Baijiao coal reservoir, SW China

Zhang, Dongming; Chu, Yapei; Li, Shujian; Yang, Yushun; Bai, Xin; Ye, Chen; Wen, Decai

doi:10.1098/rsos.181411

Cited by 14 publications

(8 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While Tang et al [7] experimentally studied the effect of temperature on spontaneous combustion of coal and proposed the critical temperature for spontaneous combustion of different coal types. Several researchers found that gas adsorption in coal is related to the oxygen functional group by infrared spectroscopy, and the oxygen concentration affects the combustion of coal particles [8][9][10][11]. Recently, Xin et al [12,13] carried out continuous measurement on sub-bituminous coal samples under different temperatures and oxygen concentrations, and analysed the chemical relationship between oxygen consumption and oxygen effect.…”

Section: Introductionmentioning

confidence: 99%

A numerical study on oxygen adsorption in porous media of coal rock based on fractal geometry

Liang

et al. 2020

R. Soc. open sci.

View full text Add to dashboard Cite

In order to explore the factors affecting coal spontaneous combustion, the fractal characteristics of coal samples are tested, and a pore-scale model for oxygen adsorption in coal porous media is developed based on self-similar fractal model. The liquid nitrogen adsorption experiments show that the coal samples indicate evident fractal scaling laws at both low-pressure and high-pressure sections, and the fractal dimensions, respectively, represent surface morphology and pore structure of coal rock. The pore-scale model has been validated by comparing with available experimental data and numerical simulation. The present numerical results indicate that the oxygen adsorption depends on both the pore structures and temperature of coal rock. The oxygen adsorption increases with increased porosity, fractal dimension and ratio of minimum to maximum pore sizes. The edge effect can be clearly seen near the cavity/pore, where the oxygen concentration is low. The correlation between the oxygen adsorption and temperature is found to obey Langmuir adsorption theory, and a new formula for oxygen adsorption and porosity is proposed. This study may help understanding the mechanisms of oxygen adsorption and accordingly provide guidelines to lower the risk of spontaneous combustion of coal.

show abstract

Section: Introductionmentioning

confidence: 99%

A numerical study on oxygen adsorption in porous media of coal rock based on fractal geometry

Liang

et al. 2020

R. Soc. open sci.

View full text Add to dashboard Cite

show abstract

“…According to the principles of NMR, the total lateral relaxation rate

\frac{1}{T_{2}}

can be expressed as follows 31 :

\frac{1}{T_{2}} = \frac{1}{T_{2 b}} + \frac{1}{T_{2 s}} + \frac{1}{T_{2 d}},

where

T_{2} b

is the transverse relaxation time of free fluid,

T_{2} s

is the transverse relaxation time of fluid caused by surface relaxation, and

T_{2} d

is the transverse relaxation time caused by diffusion relaxation in a gradient magnetic field; surface relaxation plays a major role. Based on Equation 1, the T 2 spectrum obtained by NMR experiments can reflect the pore size distribution characteristics of sandstone samples treated at different temperatures.…”

Section: Test Results and Analysismentioning

confidence: 99%

“…Finally, the different samples were observed by a Quattro S scanning electron microscope system, and micromorphology photos of each sample were obtained. According to the principles of NMR, the total lateral relaxation rate 1 T 2 can be expressed as follows 31 :…”

Section: Sem Testmentioning

confidence: 99%

Thermal cracking characteristics and mechanism of sandstone after high‐temperature treatment

Xiao

Yu²,

Li³

et al. 2021

Fatigue Fract Eng Mat Struct

Self Cite

View full text Add to dashboard Cite

To study the thermal cracking characteristics and mechanism of sandstone after high-temperature treatment, the pore size distribution and micromorphology of sandstone were observed by nuclear magnetic resonance and scanning electron microscopy. Then, based on the Weibull distribution theory, a thermal elastic mechanical model of random heterogeneous rock was established for the rock unit, the thermal stress distribution characteristics of sandstone were analyzed, and the thermal fracture mechanism of rock was discussed. The results show that the porosities of the samples increased with increasing temperature and the proportion of large pores increased significantly when exceeded 400 C. Particularly when reached 1000 C, thermal cracking was distributed in a complex network. Additionally, different rock units are in different thermal stress states, which leads to the regional differences in the distribution of rock thermal fracture. When exceeded 400 C, there were obvious thermal cracks near the outer edge that weakened the mechanical properties of rock.

show abstract

“…The critical value I HRC at the boundary between supercriticality and subcriticality was determined as a function of pile volume. (5) The effect of the ratio of coal particle size to coal pile size, D/L S , on T CSIT was incorporated into the original equation that gave T CSIT in terms of just coal pile volume. The modified equation may be useful to evaluate the effect of coal particle size on coal temperature rise in a coal pile.…”

Section: Discussionmentioning

confidence: 99%

“…Whatever the mining method, coal is transported to the ground in large quantities, and because of the intrinsic properties of coal, this presents hazards in all processing stages after mining [1]. These hazards include spontaneous combustion resulting from the complex physical and chemical structure of coal and its propensity to oxidization [2][3][4][5]. The spontaneous combustion of coal starts from slow physico-chemical reaction processes in the low-temperature range, culminating in a final stage when red-hot spots can be found on the surfaces of coal piles or pillars.…”

Section: Introductionmentioning

confidence: 99%

Effects of temperature gradient and particle size on self-ignition temperature of low-rank coal excavated from inner Mongolia, China

Wang

Zhang

et al. 2019

R. Soc. open sci.

View full text Add to dashboard Cite

This study investigates the effects of temperature gradient and coal particle size on the critical self-ignition temperature T CSIT of a coal pile packed with low-rank coal using the wire-mesh basket test to estimate T CSIT based on the Frank–Kamenetskii equation. The values of T CSIT , the temperature gradient and the apparent activation energy of different coal pile volumes packed with coal particles of different sizes are measured. The supercriticality or subcriticality of the coal is assessed using a non-dimensional index I HR based on the temperature gradient at the temperature cross-point between coal and ambient temperatures for coal piles with various volumes and particle sizes. The critical value I HRC at the boundary between supercriticality and subcriticality is determined as a function of pile volume. The coal status of supercritical or subcritical can be separated by critical value of I HR as a function of pile volume. Quantitative effects of coal particle size on T CSIT of coal piles are measured for constant pile volume. It can be concluded that a pile packed with smaller coal particles is more likely to undergo spontaneous combustion, while the chemical activation energy is not sensitive to coal particle size. Finally, the effect of coal particle size on T CSIT is represented by the inclusion of an extra term in the equation giving T CSIT for a coal pile.

show abstract

Petrophysical characterization of high-rank coal by nuclear magnetic resonance: a case study of the Baijiao coal reservoir, SW China

Cited by 14 publications

References 29 publications

A numerical study on oxygen adsorption in porous media of coal rock based on fractal geometry

A numerical study on oxygen adsorption in porous media of coal rock based on fractal geometry

Thermal cracking characteristics and mechanism of sandstone after high‐temperature treatment

Effects of temperature gradient and particle size on self-ignition temperature of low-rank coal excavated from inner Mongolia, China

Contact Info

Product

Resources

About