Effective molecular diffusion coefficient in a two-phase gel medium

2006 ◽  
Vol 124 (20) ◽  
pp. 204903 ◽  
Author(s):  
Owen A. Hickey ◽  
Jean-François Mercier ◽  
Michel G. Gauthier ◽  
Frédéric Tessier ◽  
Smaine Bekhechi ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Molecular Diffusion ◽  
Two Phase ◽  
Molecular Diffusion Coefficient

Concentration-dependent molecular diffusion coefficient of dimethyl ether in bitumen

Fuel ◽  
2020 ◽  
Vol 274 ◽  
pp. 117809
Author(s):  
Mohammad Khalifi ◽  
Mohsen Zirrahi ◽  
Hassan Hassanzadeh ◽  
Jalal Abedi
Keyword(s):  
Diffusion Coefficient ◽  
Dimethyl Ether ◽  
Molecular Diffusion ◽  
Molecular Diffusion Coefficient

Diffusion Coefficients from Capillary Flow

1963 ◽  
Vol 3 (03) ◽  
pp. 256-266 ◽  
Author(s):  
H.R. Bailey ◽  
W.B. Gogarty
Keyword(s):  
Differential Equation ◽  
Diffusion Coefficient ◽  
Numerical Solution ◽  
Diffusion Coefficients ◽  
Molecular Diffusion ◽  
Capillary Flow ◽  
Molecular Diffusion Coefficient ◽  
Flow Method ◽  
And Diffusion ◽  
Flow Experiments

Abstract Methods are presented for determining molecular diffusion coefficients by using data from capillary flow experiments. These methods are based on a numerical solution (presented in a previous paper) of the partial differential equation describing the combined mechanisms of flow and diffusion. Results from this numerical solution are given and compared with the approximate analytical solution of G. I. Taylor. The numerical solution is valid over a much larger time range. These methods are applied to experimental results for the fluid pairs water-potassium permanganate solution and amyl acetateorthoxylene. Both of these fluid pairs have approximately equal densities and viscosities. Graphical and numerical techniques are presented for deters mining diffusion coefficients from the flow data. Values obtained by these techniques are compared with values obtained by other methods. Introduction The molecular diffusion coefficient is known to be a variable in determining the amount of mixing in a miscible displacement process. The effect of molecular diffusion on dispersion in longitudinal flow through porous media has been examined by different investigators. These investigators concluded that at low velocities of flow, the amount of dispersion is approximately proportional to the molecular diffusion coefficient. The influence of diffusion on fingering, channeling, and overriding has been mentioned by other investigators. Recent studies have been made on the effects of molecular diffusion in connection with the problem of gravity segregation. Many different methods have been developed for the experimental determination of molecular diffusion coefficients. These methods differ mainly according to boundary conditions selected and analytical procedures used. Nevertheless, all of these methods have the condition in common that the bulk fluids in which diffusion is occurring are stationary with respect to each other. In connection with a series of papers on mixing in capillary flow, Taylor suggested the use of a flow method for determining molecular diffusion coefficients. Additional studies have been conducted on miscible displacements in capillary tubes, but the data from these studies were not used for the specific purpose of determining diffusion coefficients. The flow method proposed by Taylor results in a single value of the diffusion coefficient for the fluid pair used in the displacement experiments. This single value represents the true value for the fluid pair when the diffusion coefficient is independent of concentration. If the diffusion coefficient is a function of concentration, the single value obtained by the flow method gives an average value for the coefficient of the fluid pair. These average values are based on diffusion taking place over the entire range of concentration, i.e., from 0 per cent of one fluid to 100 per cent of that same fluid. In field applications of the miscible displacement process, gradients occur over the same range of concentration as are found in the displacements in capillary tubes. Molecular diffusion coefficients obtained from the capillary flow method should, therefore, be especially relevant to field operations. This investigation was undertaken to evaluate the feasibility of obtaining molecular diffusion coefficients from capillary flow experiments. In making this evaluation, diffusion coefficients were first determined for two systems from data obtained in capillary flow experiments. These values of the diffusion coefficient were then compared to values obtained by other methods. MIXING IN CAPILLARY FLOW-THEORETICAL The theoretical basis for determining molecular diffusion coefficients from capillary flow experiments is the partial differential equation relating the mechanisms of flow and diffusion. SPEJ P. 256^

Experimental Investigation of Gas-Heavy Oil Molecular Diffusion Coefficient in Porous Media: Experimental Results for CO2 in Iranian Crudes

2011 ◽  
Vol 312-315 ◽  
pp. 1049-1054 ◽  
Author(s):  
Navid Mirjordavi ◽  
M. Kazemeini ◽  
R. Kharrat ◽  
M.H. Ghazanfari ◽  
A. Salehi
Keyword(s):  
Experimental Investigation ◽  
Porous Media ◽  
Diffusion Coefficient ◽  
Heavy Oil ◽  
Molecular Diffusion ◽  
Initial Pressure ◽  
Experimental Results ◽  
Molecular Diffusion Coefficient ◽  
Molecular Diffusivity ◽  
Mathematical Correlation

Molecular diffusion of gases in crude oils plays a crucial role in several oil recovery processes especially in cold-based production process. However, experimental data concerning CO2 diffusivity in heavy oils due to the tedious nature of diffusivity measurements are relatively rare in the open literature. In this work, a comprehensive experimental investigation of the effective molecular diffusion determination of CO2-heavy oil systems in homogeneous porous media was studied. The so-called pressure decay method was applied to measure the molecular diffusivity of carbon dioxide in heavy oil. Furthermore, effect of various parameters such as initial pressure, temperature and porous media on molecular diffusion coefficient have been analyzed and based upon experimental results, a new mathematical correlation for prediction of CO2-heavy oil molecular diffusion coefficient in presence of porous medium as a function of temperature was proposed.

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