Permeability (earth sciences)

About: Permeability (earth sciences) is a research topic. Over the lifetime, 15424 publications have been published within this topic receiving 288535 citations.

Preliminary experiments on hydrodynamic movement induced by evaporation and their bearing on the dolomite problem

Abstract: SUMMARY Experiments were performed to demonstrate that saline interstitial waters under an arid coastal plain could be set in hydrodynamic movement to replace the evaporative loss near the surface. In contrast to movement in a vadose zone, which is related to capillary forces caused by surface tension, the type of movement we observed was induced by a vertical hydraulic gradient under the evaporated area. Fluid flow through porous media was induced by an upward decrease in hydrodynamic potential during evaporation. We propose to call this type of movement evaporative pumping. Experiments further verified that flow rate induced by evaporative pumping was directly governed by evaporation alone; linear flow rate through coarse sand and that through very fine silt was approximately the same under the same evaporative condition. Yet the movement apparently obeyed Darcy's law. Since the permeability of the medium was fixed, and the flow rate was dictated by evaporation, only the hydraulic gradient could be the dependent variable in the Darcy equation. We observed that the gradient was indeed much greater in relative impermeable silt than in permeable sand, when the water to replace evaporative loss must flow with the same rate through those media. Our experiments suggested that hydrodynamic movement induced by evaporation could be an effective mechanism to transport magnesium-bearing solutions through relatively impermeable sediments of an arid coastal plain. Computations showed that dolomitization by evaporative pumping could proceed at a rate to account for the origin of Recent dolomite crusts, and for the great thickness of ancient supratidal dolomites. In contrast, we believed that dolomitization by seepage reflux or by groundwaters cannot be extensive, because of the inadequate magnesium-supply rates by such waters.

Pore-scale investigation of viscous coupling effects for two-phase flow in porous media.

Abstract: Recent studies have revealed that viscous coupling effects in immiscible two-phase flow, caused by momentum transfer between the two fluid phases, can be important in porous medium systems. In this work, we use a three-dimensional parallel processing version of a two-fluid-phase lattice Boltzmann (LB) model to investigate this phenomenon. A multiple-relaxation-time (MRT) approximation of the LB equations is used in the simulator, which leads to a viscosity-independent velocity field. We validate our model by verifying the velocity profile for two-phase flow through a channel with a square cross section. We then simulate co-current flow through a sphere-pack porous medium and obtain correlations of the relative permeabilities as a function of capillary number, wettability, and the fluid viscosities. The results are qualitatively consistent with experimental observations. In addition, we calculate the generalized permeability coefficients and show that the coupling coefficients are significant and the matrix is nonsymmetric. We also find a strong correlation between the relative permeability and interfacial area between fluids, indicating that both the common extension of Darcy's Law and the generalized formulation accounting for viscous coupling effects do not provide adequate insight into two-phase flow processes in porous media. This work lends additional support for the hypothesis that interfacial area is a key variable for multiphase flow in porous medium systems.

Hydro-mechanical aspects of the sand production problem

Abstract: This paper examines the hydro-mechanical aspect of the sand production problem and sets the basic frame of the corresponding mathematical modelling. Accordingly, piping and surface erosion effects are studied on the basis of mass balance and particle transport considerations as well as Darcy's law. The results show that surface erosion is accompanied by high changes of porosity and permeability close to the free surface. Quantities which can be measured in experiment, like the amount of produced solids or fluid discharge, can be used in an inverse way to determine the constitutive parameters of the problem.