Study of Drainage and Percolation of Nitrogen–Water Flooding in Tight Coal by NMR Imaging

Xue, Dongjie; Zhou, Hongwei; Liu, Y. T.; Deng, Lijun; Zhang, L.

doi:10.1007/s00603-018-1473-6

Cited by 63 publications

(35 citation statements)

References 44 publications

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“…Combining nuclear magnetic resonance technology with traditional foam displacement experimental methods, a foam flooding NMR experimental can be conducted. Nuclear magnetic resonance is a method to calculate the amount of hydrogen nuclei and the volume of fluid by measuring the fluid magnetization decay with time ( the change in relaxation time T 2 ) in an external magnetic field [6] . The NMR technique obtains the nuclear magnetic resonance T 2 spectrum by measuring the superposition of the signals of water in different sizes of pores.…”

Section: Theory Of Nmrmentioning

confidence: 99%

Nuclear Magnetic Resonance Evaluation Study for Effect of Foam flooding in Heterogeneous Cores

Hua

2020

E3S Web Conf.

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Foam flooding demonstrated the ability to solve the viscous fingering problem of gas flooding and increase the sweep efficiency in enhancing oil recovery. It is commonly used in development of heterogeneous reservoirs. While the characteristics of fluid migration in pores and between layers were still unclear. In this paper, Dynamic change of oil and water with different foam quality was tested during foam flooding by NMR method. Oil displacement effect of water flooding and foam flooding was compared. The results showed the foam quality affected the foam stability and profile control effect. Compared with water flooding, the foam could increase the recovery rate of the low-permeability layer, and the foam system with high stability had a high sweep efficiency and a high oil displacement efficiency in the heterogeneous cores.

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Section: Theory Of Nmrmentioning

confidence: 99%

Nuclear Magnetic Resonance Evaluation Study for Effect of Foam flooding in Heterogeneous Cores

Hua

2020

E3S Web Conf.

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“…When coal as a porous medium changes into a fracture-dominated structure, few results of stress-permeability can illustrate the sudden transition of the geometric phase. Darcy's law can describe the seepage behavior in porous media, and the cubic law is the theoretical basis for analyzing stress-permeability for fractures [35][36][37]. For steady flow, the two laws can well describe before and after the dilatant boundary.…”

Section: Percolation Model For Transition Behavior Of Ch 4 Seepagementioning

confidence: 99%

A Strain-Based Percolation Model and Triaxial Tests to Investigate the Evolution of Permeability and Critical Dilatancy Behavior of Coal

et al. 2018

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Modeling the coupled evolution of strain and CH 4 seepage under conventional triaxial compression is the key to understanding enhanced permeability in coal. An abrupt transition of gas-stress coupled behavior at the dilatancy boundary is studied by the strain-based percolation model. Based on orthogonal experiments of triaxial stress with CH 4 seepage, a complete stress-strain relationship and the corresponding evolution of volumetric strain and permeability are obtained. At the dilatant boundary of volumetric strain, modeling of stress-dependent permeability is ineffective when considering the effective deviatoric stress influenced by confining pressure and pore pressure. The computed tomography (CT) analysis shows that coal can be a continuous medium of pore-based structure before the dilatant boundary, but a discontinuous medium of fracture-based structure. The multiscale pore structure geometry dominates the mechanical behavior transition and the sudden change in CH 4 seepage. By the volume-covering method proposed, the linear relationship between the fractal dimension and porosity indicates that the multiscale network can be a fractal percolation structure. A percolation model of connectivity by the axial strain-permeability relationship is proposed to explain the transition behavior of volumetric strain and CH 4 seepage. The volumetric strain on permeability is illustrated by axial strain controlling the trend of transition behavior and radical strain controlling the shift of behavior. A good correlation between the theoretical and experimental results shows that the strain-based percolation model is effective in describing the transition behavior of CH 4 seepage in coal.Processes 2018, 6, 127 2 of 22 seams, to improve permeability for easy extraction, premining the protective coal is often carried out to relieve the stress [4,5]. At the working face, the hydraulic fracturing method is often employed to achieve local stress adjustment. The huge demand in CH 4 promotes a deep understanding of sudden changes in permeability, especially induced by the coupled effect of gas and stress. The key to all these problems is to accurately understand the transition of permeability. We need a new model that can illustrate the whole change in permeability, even sudden transitions.Under triaxial compression, the permeability of CH 4 mainly depends on the shearing-induced dilatancy of the coal. Modeling enhanced permeability with deviatoric stress is useful for understanding the coupled mechanism between the dilatant deformation and the seepage or percolation channel. Many outstanding achievements focus on the study of stress-dependent permeability without considering transition effect. Many models [6][7][8][9][10][11], as shown in Table 1, have been made based on the excavation damage zone (EDZ), which depends on continuous media to explain the coupled process [12]. To our knowledge, the stress-dependent model can effectively explain the coupled effect before the dilatant boundary, taking coal as a continuous porous mediu...

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“…As an instantaneous, in situ, and dynamic method, the low-field NMR method has been used in the field of unconventional reservoir characterization (i.e., permeability, porosity, and wettability) in recent years [36][37][38][39][40][41][42][43][44][45][46][47]. There are, however, quite few studies involving low-field NMR relaxation characteristics of adsorbed methane in coal.…”

Section: Introductionmentioning

confidence: 99%

Application of a Modified Low-Field NMR Method on Methane Adsorption of Medium-Rank Coals

et al. 2021

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Methane adsorption capacity is an important parameter for coalbed methane (CBM) exploitation and development. Traditional examination methods are mostly time-consuming and could not detect the dynamic processes of adsorption. In this study, a modified low-field nuclear magnetic resonance (NMR) method that compensates for these shortcomings was used to quantitatively examine the methane adsorption capacity of seven medium-rank coals. Based on the typical T 2 amplitudes obtained from low-field NMR measurement, the volume of adsorbed methane was calculated. The results indicate that the Langmuir volume of seven samples is in a range of 18.9–31.85 m3/t which increases as the coal rank increases. The pore size in range 1-10 nm is the main contributor for gas adsorption in these medium-rank coal samples. Comparing the adsorption isotherms of these coal samples from the modified low-field NMR method and volumetric method, the absolute deviations between these two methods are less than 1.03 m3/t while the relative deviations fall within 4.76%. The absolute deviations and relative deviations decrease as vitrinite reflectance ( R o ) increases from 1.08% to 1.80%. These results show that the modified low-field NMR method is credible to measure the methane adsorption capacity and the precision of this method may be influenced by coal rank.

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Study of Drainage and Percolation of Nitrogen–Water Flooding in Tight Coal by NMR Imaging

Cited by 63 publications

References 44 publications

Nuclear Magnetic Resonance Evaluation Study for Effect of Foam flooding in Heterogeneous Cores

Nuclear Magnetic Resonance Evaluation Study for Effect of Foam flooding in Heterogeneous Cores

A Strain-Based Percolation Model and Triaxial Tests to Investigate the Evolution of Permeability and Critical Dilatancy Behavior of Coal

Application of a Modified Low-Field NMR Method on Methane Adsorption of Medium-Rank Coals

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