Effective porosity

About: Effective porosity is a research topic. Over the lifetime, 1199 publications have been published within this topic receiving 26511 citations.

Determination of porosity and fluid saturation of underground formations

Abstract: A method of determining the porosity and fluid saturation for a given volume of an underground formation through which a borehole is drilled, the method comprising: measuring, from within the borehole, parameters relating to characteristics of the underground formation; determining volumetric values for resistivity, hydrogen index, density and neutron capture cross-section for the given volume from the measured parameters, each volumetric value including a contribution from formation matrix, water, oil and gas; determining, from the volumetric values, the volumes of rock matrix, pore water, oil and gas, and the salinity of the pore water; and determining the porosity and fluid saturation of the volume of the formation from the determined volumes and salinity.

Porosity Partitioning and Permeability Quantification in Vuggy Carbonates, Permian Basin, West Texas, U.S.A.

Abstract: Using high-resolution electrical borehole images and other open-hole log data in 13 wells, a case study was conducted to analyze the porosity and permeability heterogeneity in the Means field in the Permian Basin, west Texas. Because of negligible clay and other conductive minerals in the predominantly dolomitic rocks, the electrical images are converted into microporosity maps of the boreholes using a modified Archie equation. The vug porosity is then partitioned from the total porosity by analyzing the porosity spectra around the boreholes in the sliding windows of 1-in. (2.5-cm)-thick interval. A practical workflow was also developed to compute a sonic vug-porosity index using the sonic, neutron, and density logs. The two vug porosities based on the independent measurements support each other in the Means field except that the sonic vug-porosity index has much lower resolution than the image-derived porosity. Through iterative experiments, a synthetic permeability model is established using the total porosity and vug-porosity logs. The core permeability in the vuggy dolomites varies exponentially with the product of the vug-porosity and vug-connectivity factor. Thin superpermeable vuggy zones below the resolution of the conventional logs are revealed by the electrical images and the permeability quantification. These superpermeable zones sandwiching thick oil-bearing reservoir rocks are the primary cause for the early high water cut and the bypassed oil. Integration of the continuous high-resolution permeability logs, the petrophysical facies from supervised neural network (SNN) processing, and the production data from both producers and injectors provide valuable insights to reservoir modeling.

Physical Characteristics of Medical Textile Prostheses Designed for Hernia Repair: A Comprehensive Analysis of Select Commercial Devices

Abstract: Inguinal hernia repairs are among the most frequent operations performed worldwide. This study aims to provide further understanding of structural characteristics of hernia prostheses, and better comprehensive evaluation. Weight, porosity, pore size and other physical characteristics were evaluated; warp knitting structures were thoroughly discussed. Two methods referring to ISO 7198:1998, i.e., weight method and area method, were employed to calculate porosity. Porosity ranged from 37.3% to 69.7% measured by the area method, and 81.1% to 89.6% by the weight method. Devices with two-guide bar structures displayed both higher porosity (57.7%-69.7%) and effective porosity (30.8%-60.1%) than single-guide bar structure (37.3%-62.4% and 0%-5.9%, respectively). Filament diameter, stitch density and loop structure combined determined the thickness, weight and characteristics of pores. They must be well designed to avoid zero effective porosity regarding a single-bar structure. The area method was more effective in characterizing flat sheet meshes while the weight method was perhaps more accurate in describing stereoscopic void space for 3D structure devices. This article will give instructive clues for engineers to improve mesh structures, and better understanding of warp knitting meshes for surgeons.

Impact of kinetic mass transfer on free convection in a porous medium

Abstract: We investigate kinetic mass transfer effects on unstable density-driven flow and transport processes by numerical simulations of a modified Elder problem. The first-order dual-domain mass transfer model coupled with a variable-density-flow model is employed to describe transport behavior in porous media. Results show that in comparison to the no-mass-transfer case, a higher degree of instability and more unstable system is developed in the mass transfer case due to the reduced effective porosity and correspondingly a larger Rayleigh number (assuming permeability is independent on the mobile porosity). Given a constant total porosity, the magnitude of capacity ratio (i.e., immobile porosity/mobile porosity) controls the macroscopic plume profile in the mobile domain, while the magnitude of mass transfer timescale (i.e., the reciprocal of the mass transfer rate coefficient) dominates its evolution rate. The magnitude of capacity ratio plays an important role on the mechanism driving the mass flux into the aquifer system. Specifically, for a small capacity ratio, solute loading is dominated by the density-driven transport, while with increasing capacity ratio local mass transfer dominated solute loading may occur at later times. At significantly large times, however, both mechanisms contribute comparably to solute loading. Sherwood Number could be a nonmonotonic function of mass transfer timescale due to complicated interactions of solute between source zone, mobile zone and immobile zone in the top boundary layer, resulting in accordingly a similar behavior of the total mass. The initial assessment provides important insights into unstable density-driven flow and transport in the presence of kinetic mass transfer.