Experiment of coal damage due to super-cooling with liquid nitrogen

Cai, Chengzheng; Li, Gensheng; Huang, Zhongwei; Tian, Shouceng; Shen, Zhonghou; Fu, Xuan

doi:10.1016/j.jngse.2014.11.016

Cited by 153 publications

(59 citation statements)

References 12 publications

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“…Cai et al 31,32 also used NMR to study rock and coal that had been frozen using LN 2 . They discovered that LN 2 causes greater freezing damage to coal compared to other rocks.…”

Section: Previous Studiesmentioning

confidence: 99%

Pore Structure in Coal: Pore Evolution after Cryogenic Freezing with Cyclic Liquid Nitrogen Injection and Its Implication on Coalbed Methane Extraction

et al. 2016

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Freezing and thawing cycles occur with cyclic liquid nitrogen (LN 2 ) injection in coal. The freeze−thaw treatment damages the pore structure of coal and thus increases its permeability. In this study, NMR and strain monitoring were employed to investigate the changes in coal structure when the coal specimens were under cryogenic treatment using LN 2 . We classified freeze−thaw process into four stages; stages I and III are dominated by seepage pore development, and stages II and IV are dominated by adsorption pore development. It was found that LN 2 freeze−thaw cycles can cause structural deterioration in the coal so as to improve both fracture density and overall permeability. The results demonstrate that the rate of increase of both the effective porosity and total porosity of the coal are positively correlated with the LN 2 freezing time and the number of freezing cycles but negatively correlated with the residual porosity. For the same absolute LN 2 freezing time, cyclic freeze−thawing has a greater effect on the rate of growth of pore spaces and reduction of P-wave velocity in the coal compared with single freeze−thaw treatment. It was also found that the number of freeze−thaw cycles is a very important factor for the creation of larger pores, pores that can connect the fracture network. The results suggest that appropriate control of the number of freeze−thaw cycles can result in effective fracturing of coal.

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“…Cai et al 31,32 also used NMR to study rock and coal that had been frozen using LN 2 . They discovered that LN 2 causes greater freezing damage to coal compared to other rocks.…”

Section: Previous Studiesmentioning

confidence: 99%

Pore Structure in Coal: Pore Evolution after Cryogenic Freezing with Cyclic Liquid Nitrogen Injection and Its Implication on Coalbed Methane Extraction

et al. 2016

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“…Cha et al (2014) and also performed laboratory tests on cryogenic fracturing with LN 2 and found that LN 2 cooling could cause sandstone, concrete and shale to produce many interlaced micro-cracks, and decrease the initiation pressure by 40%. Moreover, Cai et al (2014Cai et al ( , 2015 and Cheng et al (2017) also noted that LN 2 cooling can increase the pore connectivity and permeability of shale and coal and reduce their bearing capacity. Although considerable efforts have been made to develop the cryogenic fracturing using LN 2 , but these studies mainly focused on the change in rock micro-cracks after LN 2 cooling, and only a few publications mentioned on the change in the damage characteristics and mechanical properties of rocks.…”

Section: Introductionmentioning

confidence: 99%

Effect of liquid nitrogen cooling on the permeability and mechanical characteristics of anisotropic shale

Jiang

Cheng

Han

et al. 2018

J Petrol Explor Prod Technol

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Liquid nitrogen (LN 2 ) fracturing is a promising new technology for unconventional reservoir simulation because it can effectively solve problems related to low permeability, low brittleness, and water shortage. The present work conducted a series of permeability and strength property-related experiments to evaluate the effect of LN 2 cooling on the permeability and mechanical characteristics of anisotropic shale. The main findings of the study are as follows: (1) The influence of the bedding direction on the permeability of anisotropic shale cannot be eliminated by LN 2 cooling. LN 2 cooling could effectively increase the initial natural damage and the pore space of anisotropic shale, possibly increasing the volume of reservoir stimulation and provide more channels for the seepage and migration of oil and gas. (2) After LN 2 cooling, the strength and brittleness of shale are obviously reduced, leading to the decrease in the ability of shale to resist deformation and failure, thereby helping to decrease the initiation pressure of reservoir stimulation. (3) The brittleness of shale will markedly increase during cryogenic fracturing, thus helping to form more complex fracture networks. Based on the present research, LN 2 fracturing has obvious advantages compared with hydraulic fracturing in increasing the volume of reservoir stimulation. The results of this study are instructive for understanding the synergistic mechanism of LN 2 fracturing and evaluating the effectiveness of reservoir simulation.

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“…After each cycle of cold loading, structural damage will occur to the coal body, and the accumulation of structural damage finally made the coal body completely break into pieces [29]. Noticeably, the damage of coal structure should also be affected by confining pressure and the influence rule of confining pressure on the damage of coal structure under the effect of liquid nitrogen is not clear.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Structural Damage in Low Permeability Coal Material of Coalbed Methane Reservoir under Cyclic Cold Loading

Zuo

Wang

et al. 2020

Energies

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The pore and fracture structure of coal is the main factor that affects the storage and seepage capacity of coalbed methane. The damage of coal structure can improve the gas permeability of coalbed methane. A coal sample with a drilled hole was kept inside of a custom-designed device to supply confining pressure to the coal sample. Liquid nitrogen was injected into the drilled hole of the coal sample to apply cyclic cold loading. Confining pressures varying from 0~7 MPa to the coal sample were applied to explore the relationship between the structural damage and confining pressure. The structural damage rules of coal samples under different confining pressure were revealed. The results showed that: (1) The structural damage degree of the coal sample increases with the increase of confining pressure; (2) The coal sample was broken after three cycles of cold loading under 7 MPa confining pressure; (3) Without confining pressure, the coal sample is more likely to be damaged or even destroyed by cold liquid nitrogen. (4) The fracture extends along the stratification direction of coal samples, which is significant for coal samples with original fractures, but not obvious for the coal sample without fracture. The research results provide a new method and theoretical basis for permeability improvement of the coal seam.

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Experiment of coal damage due to super-cooling with liquid nitrogen

Cited by 153 publications

References 12 publications

Pore Structure in Coal: Pore Evolution after Cryogenic Freezing with Cyclic Liquid Nitrogen Injection and Its Implication on Coalbed Methane Extraction

Pore Structure in Coal: Pore Evolution after Cryogenic Freezing with Cyclic Liquid Nitrogen Injection and Its Implication on Coalbed Methane Extraction

Effect of liquid nitrogen cooling on the permeability and mechanical characteristics of anisotropic shale

Mechanism of Structural Damage in Low Permeability Coal Material of Coalbed Methane Reservoir under Cyclic Cold Loading

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