Experimental study on flow characteristics of gas transport in micro- and nanoscale pores

Shen, Weijun; Song, Fuquan; Hu, Xiao; Zhu, Genmin; Zhu, Weiyao

doi:10.1038/s41598-019-46430-2

Cited by 65 publications

(36 citation statements)

References 47 publications

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“…Only when the total gas amount is larger than the sum of adsorbed and dissolved gas amount does a free gas state exist. Under high-pressure or high-temperature reservoir conditions, gas behaviors do not satisfy the ideal gas equation of state (EOS), so the real gas EOS needs to be adopted to describe its behaviors [42,43].…”

Section: Free Gas Characterizationmentioning

confidence: 99%

Review of Formation and Gas Characteristics in Shale Gas Reservoirs

et al. 2020

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An accurate understanding of formation and gas properties is crucial to the efficient development of shale gas resources. As one kind of unconventional energy, shale gas shows significant differences from conventional energy ones in terms of gas accumulation processes, pore structure characteristics, gas storage forms, physical parameters, and reservoir production modes. Traditional experimental techniques could not satisfy the need to capture the microscopic characteristics of pores and throats in shale plays. In this review, the uniqueness of shale gas reservoirs is elaborated from the perspective of: (1) geological and pore structural characteristics, (2) adsorption/desorption laws, and (3) differences in properties between the adsorbed gas and free gas. As to the first aspect, the mineral composition and organic geochemical characteristics of shale samples from the Longmaxi Formation, Sichuan Basin, China were measured and analyzed based on the experimental results. Principles of different methods to test pore size distribution in shale formations are introduced, after which the results of pore size distribution of samples from the Longmaxi shale are given. Based on the geological understanding of shale formations, three different types of shale gas and respective modeling methods are reviewed. Afterwards, the conventional adsorption models, Gibbs excess adsorption behaviors, and supercritical adsorption characteristics, as well as their applicability to engineering problems, are introduced. Finally, six methods of calculating virtual saturated vapor pressure, seven methods of giving adsorbed gas density, and 12 methods of calculating gas viscosity in different pressure and temperature conditions are collected and compared, with the recommended methods given after a comparison.

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Section: Free Gas Characterizationmentioning

confidence: 99%

Review of Formation and Gas Characteristics in Shale Gas Reservoirs

et al. 2020

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“…The liquid in this model is water, and the flowing behavior follows the Hagen-Poiseuille equation. Although the slip exists in both gas phase [ 29 ] and liquid phase [ 30 ], we ignored its effect and focus on the influence of pore structure. When the imbibition front is at

th level, the imbibition mass

can be determined as:

where

.…”

Section: Co-current Imbibition Based On the Fractal Modelmentioning

confidence: 99%

The Spontaneous Imbibition of Micro/Nano Structures in Tight Matrix and the Influence on Imbibition Potential

Chen

Wang

et al. 2020

Micromachines

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Tight matrix has relatively low permeability and porosity, with abundant micro/nano pores. The capillary force in these pores are relatively strong, making the wetting liquid easier to be imbibed in the matrix. This process is called spontaneous imbibition. The complexity of pore structure is identified as one of the key factors influencing the imbibition process, but the detailed mechanism is not clear. Thus, in this work, a method is proposed to evaluate the influence of pore structure on imbibition process. Pore structure has fractal properties in a specific scale. By using the fractal theory, an imbibition model is provided to analyze the influence of microscopic structures on spontaneous imbibition, considering the pore size distribution and pore connectivity. Also, based on this model, the influencing factors on dimensionless imbibition and diffusion rate are discussed. Results show that the pore structure has more branches, larger and shorter sub-throats has higher chance to gain a high imbibition rate. Finally, a 3D imbibition parameter cube is constructed to determine the parameter combinations in favor of strong water diffusion potential. By utilizing the analysis method based on the fractal theory, we can effectively evaluate the imbibition potential. It is helpful to provide a guidance to evaluate the water imbibition to gas production.

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“…In general, pores in shale are much smaller than those in conventional sandstone reservoirs (Loucks et al 2012;Shen et al 2019). Pore structure characterization has attracted great attention.…”

Section: Introductionmentioning

confidence: 99%

Pore structure characterization and its effect on methane adsorption in shale kerogen

et al. 2020

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Pore structure characterization and its effect on methane adsorption on shale kerogen are crucial to understanding the fundamental mechanisms of gas storage, transport, and reserves evaluation. In this study, we use 3D scanning confocal microscopy, scanning electron microscopy (SEM), X-ray nano-computed tomography (nano-CT), and low-pressure N2 adsorption analysis to analyze the pore structures of the shale. Additionally, the adsorption behavior of methane on shales with different pore structures is investigated by molecular simulations. The results show that the SEM image of the shale sample obviously displays four different pore shapes, including slit pore, square pore, triangle pore, and circle pore. The average coordination number is 4.21 and the distribution of coordination numbers demonstrates that pores in the shale have high connectivity. Compared with the adsorption capacity of methane on triangle pores, the adsorption capacity on slit pore, square pore, and circle pore are reduced by 9.86%, 8.55%, and 6.12%, respectively. With increasing pressure, these acute wedges fill in a manner different from the right or obtuse angles in the other pores. This study offers a quantitative understanding of the effect of pore structure on methane adsorption in the shale and provides better insight into the evaluation of gas storage in geologic shale reservoirs.

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Experimental study on flow characteristics of gas transport in micro- and nanoscale pores

Cited by 65 publications

References 47 publications

Review of Formation and Gas Characteristics in Shale Gas Reservoirs

Review of Formation and Gas Characteristics in Shale Gas Reservoirs

The Spontaneous Imbibition of Micro/Nano Structures in Tight Matrix and the Influence on Imbibition Potential

Pore structure characterization and its effect on methane adsorption in shale kerogen

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