Concentration Dependence of the Diffusion Coefficient During Adsorption of Methane into Partially Water-Saturated Crushed Shale
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Abstract In view of the weak research on the availability of typical shale oil reservoirs from the perspective of development, this study introduced a two-dimensional nuclear magnetic resonance (NMR) evaluation method on the basis of the previous one-dimensional NMR combined with centrifugal physical simulation experiments. Not only the production characteristics of typical shale oil reservoirs were studied but also the microscopic production laws of different occurrence states were studied. The results show that the pore distribution of Jilin shale is more concentrated than that of Qinghai shale. The oil of the two blocks mainly occurs in 0.01–10 ms pores, and the occurrence ratio of Jilin shale in the pores is higher, which is more than 90%. The oil production of the two blocks is mainly dominated by 0.01–10 ms pores, and the utilization efficiency contribution of these pores in Jilin shale is higher, accounting for about 80%. The utilization efficiency (UE) increases logarithmically with centrifugal force, and the growth rate of Jilin shale is greater than that of Qinghai shale. The proportion of free oil in Jilin block is less than that in Qinghai block. The shale oil in the two blocks is both at 15% final UE, and the UE of free oil in Jilin shale is about 9% and that of Qinghai shale is about 12%. The recoverability of Jilin shale is lower than that of Qinghai shale.
Shale oil extraction
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The diffusion of group III and group V impurities into germanium and silicon is reviewed. Observed and possible variations of the diffusion coefficient with concentration are discussed, followed by a summary of the diffusion coefficients and of solutions to the diffusion equation. Finally, methods for the evaluation of diffused layers and diffusion techniques are described.
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Ambipolar diffusion
Lattice diffusion coefficient
Anomalous Diffusion
Diffusion layer
Molecular diffusion
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The concentrations and modes of occurrence of U and Th in 23 oil shale samples from China were studied.The concentrations of U and Th were determined by inductively coupled plasma-mass spectrometry.The occurrence of U and Th in Huadian and Luozigou oil shale was investigated using six-step sequential chemical extract method.The concentrations of U in oil shale are within 10×10-6 and average of 3.92×10-6.The concentrations of Th in oil shale are within 20×10-6 and average of 10.51×10-6.The abundances of U and Th in oil shale are slightly higher than in crust and close to sedimentary rocks.The experimental results of floating and sinking roughly equal that of the sequential chemical extraction in U and Th.The U and Th in oil shale are mainly existed in minerals.
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Pulsed field gradient
Field strength
Molecular diffusion
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Effective diffusion coefficient and diffusion-controlled reactions in insulating solids with defects
Abstract The expressions for effective diffusion coefficient are obtained in the mean field approximation for two-phase system for spatial dimensions of 1, 2 and 3. The existence of potential barrier for diffusion on the phase boundary was taken into account via the boundary conditions. Obtained formulae could be applied in the theory of diffusion-controlled reactions and for interpreting the experimental data on defect diffusion in two-phase media.
Phase boundary
Diffusion layer
Reaction–diffusion system
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The problem of diffusion coefficients with fixed surface composition and variable diffusion coefficients is considered in the present paper. The rate of solute uptake or loss is given using the same equations as for constant diffusion coefficients taking the diffusion coefficient equal to D lim = approximately the first moment of the diffusion coefficient about the surface composition. When a new phase forms on the surface of the diffusion couple and it has a small composition range the rate of movement of the phase boundary is given by the same equations as for constant diffusion coefficients, but using D̄, the weighted mean diffusion coefficient. As the composition range of the phase increases, the diffusion coefficient to be used deviates towards the value of the diffusion coefficient at the surface. The results are illustrated with calculated single-and two-phase composition profiles for carburization of a steel specimen.
Diffusion layer
Molecular diffusion
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Retorting studies of Sunbury Shale from northeastern Kentucky have been carried out systematically and compared with earlier studies of Colorado oil shale. The Fischer assay method is used as a baseline model for evaluation of the retorting parameters. The effects of inert gas flow and of particle size variation when retorting Sunbury Shale are similar to effects observed in retorting Colorado shale. However, oil yield is very dependent on shale heat-up rate; its effect is much greater on Sunbury Shale than on western shale. Pyrite has a detrimental effect on the quantity of oil generated from Sunbury Shale, and a number of design parameters impact oil production. Fischer assay is not nearly as optimum a method for obtaining oil from the Sunbury Shale as it is for retorting Colorado shale. For this eastern oil shale, an assay employing 5 times the Fischer assay heating rate and a 1380F upper temperature (i.e., 100F/min to 1380F) results in a process yield that is 110-116%
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Oil shale gas
Shale oil extraction
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A theoretical description of the diffusion of a thin film of titanium (Ti) into a lithium niobate (LiNbO3) crystal is reported. A variable depth diffusion coefficient is used to explain the prominent lateral surface diffusion generally observed in the fabrication of Ti-diffused optical waveguides on non-Z-cut LiNbO3. A finite integral transform technique is used to solve the diffusion equation described by Fick’s law. Since the enhanced lateral diffusion is usually ascribed to anisotropic diffusion, we compare our calculations with those obtained using different diffusion coefficients for each diffusion direction. The approach with a variable depth diffusion coefficient can explain the enhancement of lateral diffusion and the peak of Ti concentration close to the surface observed experimentally.
Diffusion layer
Surface diffusion
Anomalous Diffusion
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