an improved model of mud dispersion has been introduced in this work. the advantages of this model consist of a new analytical correlation for dispersivity by using resistivity log data and using a new aspect of capacitance dispersion model. mathematical formulations were expressed, solved by numerical model taking advantage of actual log and formation data. achieved results yielded reasonable ...

diffusivity equation commonly used for pressure distribution prediction in porous media results from substituting equation of state and continuity equation in navier-stokes momentum equation. from mathematical point of view this equation format shows infinite propagation speed for pressure pulse through porous media, which is physically impossible. this issue may caused by numerous assumptions ...

  Diffusivity equation commonly used for pressure distribution prediction in porous media results from substituting equation of state and continuity equation in Navier-Stokes momentum equation. From mathematical point of view this equation format shows infinite propagation speed for pressure pulse through porous media, which is physically impossible. This issue may caused by numerous assumption...

distinguishing productive zones of a drilled oil well plays a very important role for petroleum engineers to decide where to perforate to produce oil. conventionally, net pay zones are determined by applying a set of cut-offs on perophysical logs. as a result, the conventional method finds productive intervals crisply. in this investigation, a net index value is proposed, then; diffusivity equa...

Gas reservoirs with low permeability (k<0.1 mD) are among the unconventional reservoirs and are commonly termed as "Tight Gas Reservoirs". In conventional gas reservoirs that have high permeability, the flow of gas is basically controlled by the reservoir permeability and it is calculated using the Darcy equation. In these reservoirs, gas flow due to gas diffusion is ignored compared to Dar...

Two finite difference discretization schemes for approximating the spatial derivatives in the diffusion equation in spherical coordinates with variable diffusivity are presented and analyzed. The numerical solutions obtained by the discretization schemes are compared for five cases of the functional form for the variable diffusivity: (I) constant diffusivity, (II) temporally-dependent diffusivi...

An investigation of the drying of spherical food particles was performed, using peas as the model material. In the development of a mathematical model for drying curves, moisture diffusion was modelled using Fick’s second law for mass transfer. The resulting partial differential equation was solved using a forward-time central-space finite difference approximation, with the assumption of variab...

A generalized Langevin equation with fluctuating diffusivity (GLEFD) is proposed, and it shown that the GLEFD satisfies a fluctuation-dissipation relation. If memory kernel power law, exhibits subdiffusion, non-Gaussianity, stretched-exponential relaxation. The case in which given by single exponential function also investigated as an analytically tractable example. In particular, mean-square d...

Tropospheric transport can be described qualitatively by the slow mean diabatic circulation and rapid isentropic mixing, yet a quantitative understanding of the transport circulation is complicated, as nearly half of the isentropic surfaces in the troposphere frequently intersect the ground. A theoretical framework for the effective isentropic diffusivity of tropospheric transport is presented....

the drying behavior and characteristics of date paste were studied at temperatures of 60, 70, and 80ºc as thin layer with sample thicknesses of 1, 1.5, and 2 cm in a laboratory scale vacuum chamber. modeling of drying kinetics of date paste was investigated based on the specific temperatures and sample thicknesses. the experimental moisture loss data were fitted to eight thin layer drying model...