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Raj Bali - One of the best experts on this subject based on the ideXlab platform.

R. R. Sahoo - One of the best experts on this subject based on the ideXlab platform.

G. Mohanty - One of the best experts on this subject based on the ideXlab platform.

Rosemary Knight - One of the best experts on this subject based on the ideXlab platform.

  • A theoretical treatment of the effect of microscopic Fluid Distribution on the dielectric properties of partially saturated rocks
    Geophysical Prospecting, 1992
    Co-Authors: Anthony L. Endres, Rosemary Knight
    Abstract:

    Microscopic Fluid Distribution can have a significant effect on the dielectric properties of partially saturated rocks. Evidence of this effect is found in the laboratory data presented by Knight and Nur in which different methods for controlling saturation produced very different results for the dependence of the dielectric response on water saturation. In this study, previously derived models for the dielectric response of a heterogeneous medium are generalized and the case of a pore space occupied by multiple pore Fluids is considered. By using various geometrical Distributions of water and gas, it is observed that both the pore geometry in which saturation conditions are changing and the gas–water geometry within a given pore space are critical factors in determining the effective dielectric response of a partially saturated rock. As an example, data for a tight gas sandstone undergoing a cycle of imbibition and drying are analysed. Previous research has demonstrated that significantly different microscopic Fluid Distributions result from the application of these two techniques to control the level of water saturation. By approximating these microscopic Fluid Distributions using simple geometrical models, good agreement is found between experimental data and calculated dielectric properties.

  • The effects of pore‐scale Fluid Distribution on the physical properties of partially saturated tight sandstones
    Journal of Applied Physics, 1991
    Co-Authors: Anthony L. Endres, Rosemary Knight
    Abstract:

    Pore‐scale Fluid Distribution has a significant effect on the physical properties of a partially saturated porous medium. Experimental data for the dielectric response and elastic wave velocities for a tight gas sandstone undergoing a cycle of water saturation change through imbibition and drainage are analyzed. Mathematical formulations describing the internal geometrical configuration of a porous medium in terms of a rock matrix background with embedded oblate spheroidal inclusions representing the porosity are used to theoretically predict the dielectric constant and elastic wave velocities of the partially saturated sandstone. Simple geometrical models, incorporating homogeneous and heterogeneous inclusions, are used to simulate the pore‐scale Fluid Distribution which should result from the two saturation methods employed. It is found that these simple scenarios accurately predict the functional form and magnitude of the observed saturation‐induced hysteresis in the experimental data for both the diel...

  • a laboratory study of the dependence of elastic wave velocities on pore scale Fluid Distribution
    Geophysical Research Letters, 1990
    Co-Authors: Rosemary Knight, Richard Nolenhoeksema
    Abstract:

    Laboratory data have been collected during a continuous imbibition/drainage experiment that show a clear dependence of elastic wave velocities on the details of the pore scale Distribution of water and air in a sandstone. Compressional wave velocity (Vp) was measured at a frequency of 1 MHz; shear wave velocity (Vs) was measured at a frequency of 600 kHz. During the experiment, Vp showed little variation with the level of water saturation (Sw) during increasing Sw through imbibition until Sw = 0.80, at which point Vp increased dramatically. When Sw was decreased, pronounced saturation-induced hysteresis was observed in the region 03 0.4. As a simple model, we consider the imbibition process as producing a partially saturated state in all pores; i.e. all pores contain both air and water. The drainage process, in contrast, favors the existence of either air-filled or water-filled pores. As elastic wave velocities are very sensitive to the saturation state in the smaller, “crack-like” pores, these variations in Fluid Distribution cause related variations in velocities.

  • Numerical modeling of microscopic Fluid Distribution in porous media
    Journal of Applied Physics, 1990
    Co-Authors: Rosemary Knight, Alice Chapman, Michael D. Knoll
    Abstract:

    Three numerical methods have been developed to model the equilibrium Distribution of Fluid phases in a multiphase saturated porous medium. The basic assumption made is that the Distribution of phases is governed by the static interfacial free energy of the system, such that the equilibrium phase Distribution corresponds to a minimum in the total interfacial free energy of the system. The example of determining the Distribution of water vapor and liquid water in 2D numerical models of the pore space in a rock is considered. Starting with a numerical model of the pore space, the objective of each method is to obtain the minimum energy configuration of water vapor and liquid water in the pore space for some set level of water saturation. Two of the methods are simple and computationally fast methods that can produce Fluid Distributions close to, or matching, the equilibrium configuration. These methods can, however, produce metastable configurations due to the simplistic nature of the algorithms. The third m...

Richard Nolenhoeksema - One of the best experts on this subject based on the ideXlab platform.

  • a laboratory study of the dependence of elastic wave velocities on pore scale Fluid Distribution
    Geophysical Research Letters, 1990
    Co-Authors: Rosemary Knight, Richard Nolenhoeksema
    Abstract:

    Laboratory data have been collected during a continuous imbibition/drainage experiment that show a clear dependence of elastic wave velocities on the details of the pore scale Distribution of water and air in a sandstone. Compressional wave velocity (Vp) was measured at a frequency of 1 MHz; shear wave velocity (Vs) was measured at a frequency of 600 kHz. During the experiment, Vp showed little variation with the level of water saturation (Sw) during increasing Sw through imbibition until Sw = 0.80, at which point Vp increased dramatically. When Sw was decreased, pronounced saturation-induced hysteresis was observed in the region 03 0.4. As a simple model, we consider the imbibition process as producing a partially saturated state in all pores; i.e. all pores contain both air and water. The drainage process, in contrast, favors the existence of either air-filled or water-filled pores. As elastic wave velocities are very sensitive to the saturation state in the smaller, “crack-like” pores, these variations in Fluid Distribution cause related variations in velocities.