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Effective porosity

About: Effective porosity is a research topic. Over the lifetime, 1199 publications have been published within this topic receiving 26511 citations.


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Journal ArticleDOI
TL;DR: In this paper, a sequential method from real coal model to computer-aided designed (CAD) coal model was proposed to obtain the real physical model characterizing the pore structure of coal rocks and further explore the rules governing the flow of coalbed methane.
Abstract: To obtain the real physical model characterizing the pore structure of coal rocks and further explore the rules governing the flow of coalbed methane (CBM) using numerical simulation, we proposed a sequential method from real coal model to computer-aided designed (CAD) coal model to finite element coal model. First, six different coal samples were scanned using $$\upmu $$ CT225kVFCB CT system. The obtained CT data were subject to threshold segmentation using the compensated digital terrain model and a coal model in STL format was established. Then, we elaborated a reverse engineering method to convert the coal model into a CAD coal model. Lastly, we obtained the finite element coal model after setting the boundary conditions with CFX software, numerically simulated CBM flow at 30 different pressure gradients based on the finite element coal model and analyzed the impacts of effective porosity on permeability and seepage velocity of CBM. The results showed that (1) at the microscale ( $${<}100\,\upmu \hbox {m}$$ ), the seepage velocity and pressure gradient were in agreement with the Forchheimer law of high-speed nonlinear seepage; (2) permeability of CBM shows a fluctuating, but not absolute increase with effective porosity increasing; (3) at the same pressure gradient, the overall seepage velocity of CBM increases with the effective porosity increasing, but declines with non-Darcy flow coefficient increasing; (4) the non-Darcy flow coefficient reduces with both effective porosity and permeability increasing. Fitting to power function analysis shows that compared with permeability, the effective porosity has more significant impact on the non-Darcy flow coefficient.

12 citations

Journal ArticleDOI
TL;DR: In this article, the effect of geo-stress fields on macroscopic hydro-geological conditions or microcosmic permeability of water-bearing media should follow some laws or principles.
Abstract: The effect of geo-stress fields on macroscopic hydro-geological conditions or microcosmic permeability of water-bearing media should follow some laws or principles. Cases study and tests show that: (1) At macro-geologic large scale, deformed and crashed rocks which were induced by geo-stress fields changing provided space for groundwater storage and flow. Groundwater adjusts water-bearing space and dilatants fractures by flowing and press transferring. Coupling of liquid and solid can be implemented for rocks and groundwater. Although tectonic fields witness several times of change and build-up in geological time, stress fields forming regional tectonic framework are coherent with seepage fields, orientation of the maximum horizontal stress demonstrates main seepage directions. (2) At macro-geologic middle scale, zones of stresses changing sharply, quite low stresses, stress or shear concentration can be used to show locations and types of main fractures, zones of geo-stresses changing equably can be acted as normal base media zones of tri-porosity media. (3) At micro-geologic small scale, tri-porosity media include fractured rocks, porous rocks and capillary rocks. Investigations indicate that porosity or permeability is functions of effective stresses, and porosity or permeability changing rules of porous rocks with variation of effective stresses can be described as the index model, the model of power exponent functions is suitable for those of fractured rocks, the model of the second power parabola for capillary rocks. The porosity and permeability loss in fractured rocks, which are greater than that in porous rocks, are shown by calculation of effective compressive coefficient and closing pressure in cracks. The calculations can also explain the mechanism why porosity changes are always larger than permeability changes. It is proved by the thick wall cylinder theory that the second power parabola relation between porosity or permeability loss and effective stresses for capillary rocks is correct.

12 citations

Journal ArticleDOI
TL;DR: In this article, a series of water absorption tests on dried soft rock have been conducted by the intelligent testing system for water absorption in deep soft rock, including tests of water absorbing with and without pressure.
Abstract: A series of water absorption tests on dried soft rock have been conducted by the intelligent testing system for water absorption tests in deep soft rock, including tests of water absorption with and without pressure. The results show that the water absorbing capacity of rock with a certain pressure is larger than that of rock without pressure; however, the relationship between the water absorbing percentage and the time can be expressed by w ( t ) = a (1 − e - bt ). In bi-logarithmic coordinates, the hydrophilic relationship with time in tests with pressure could be characterized by linearity, while they present concave or convex in tests without pressure. Based on the hypothesis that each influential factor is irrelevant and they have a linear correlation with the water absorbing capacity, we calculated the weight coefficient of each factor according to experimental results under different conditions. The calculations demonstrate that the effective porosity, content of smectite and kaolinite are all positively correlated with the water absorption capacity of rock; meanwhile, the fractal dimension of the effective pores presents a negative correlation with the water absorption capacity of rock. The water absorption capacity with pressure increases with increasing illite, chlorite and chlorite/smectite formation and a decrease in illite/smectite formation and the fractal dimension of the effective pores, while it is opposite in tests without pressure. The weight coefficient of smectite is smallest among positive factors, and the fractal dimension of the effective pores is the smallest amongst the negative factors.

12 citations

Journal ArticleDOI
01 Jan 1969
TL;DR: In this paper, it was shown that besides normal gas diffusion surface diffusion also occurs in cement-bonded building materials, and the effective pore radius (reff) was calculated.
Abstract: From the data presented it is apparent that besides normal gas diffusion surface diffusion also occurs in cement-bonded building materials. Only with further measurements of the gas diffusion at varying total pressures will it be possible to determine the effective porosity which plays a role in any transportation effects in the material, and hence allow the labyrinth factor (η) and the effective pore radius (reff) to be calculated, using the equation Open image in new window

12 citations

Journal ArticleDOI
TL;DR: In this article, a classification criterion was established using four reservoir grading evaluation parameters, median throat radius, effective porosity and effective permeability of fracture-cavity development zone, relationship between fracture and dissolution pore development and assemblage.

12 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20236
202232
202162
202065
201971
201847