Porosity

About: Porosity is a research topic. Over the lifetime, 35388 publications have been published within this topic receiving 710019 citations. The topic is also known as: void ratio & void fraction.

Electromagnetic determination of soil water content: Measurements in coaxial transmission lines

Abstract: The dependence of the dielectric constant, at frequencies between 1 MHz and 1 GHz, on the volumetric water content is determined empirically in the laboratory. The effect of varying the texture, bulk density, temperature, and soluble salt content on this relationship was also determined. Time-domain reflectometry (TDR) was used to measure the dielectric constant of a wide range of granular specimens placed in a coaxial transmission line. The water or salt solution was cycled continuously to or from the specimen, with minimal disturbance, through porous disks placed along the sides of the coaxial tube. Four mineral soils with a range of texture from sandy loam to clay were tested. An empirical relationship between the apparent dielectric constant Ka and the volumetric water content θv, which is independent of soil type, soil density, soil temperature, and soluble salt content, can be used to determine θv, from air dry to water saturated, with an error of estimate of 0.013. Precision of θv to within ±0.01 from Ka can be obtained with a calibration for the particular granular material of interest. An organic soil, vermiculite, and two sizes of glass beads were also tested successfully. The empirical relationship determined here agrees very well with other experimenters' results, which use a wide range of electrical techniques over the frequency range of 20 MHz and 1 GHz and widely varying soil types. The results of applying the TDR technique on parallel transmission lines in the field to measure θv versus depth are encouraging.

The Behavior of Naturally Fractured Reservoirs

Abstract: An idealized model has been developed for the purpose of studying the characteristic behavioroja permeable medium which contains regions which contribute sigizificantly to tbe pore volume O! the system but contribute negligibly to the flow capacity; e.g., a naturally fractured or vugular reservoir, Vnsteady-state flow in this model reservoir has been investigated analytically. The pressure buiid-up performance has been examined insomedetait; and, a technique foranalyzing tbebuild.up data to evaluate the desired parameters has been suggested. The use of this ap$roacb in the interpretation of field data has been discussed. As a result of this study, the following general conclusions can be drawn: 1. Two parameters are sufficient to characterize the deviation of the behavior of a medium with “double porosity ”from that of a homogeneously porous medium. 2. These Parameters can be evaluated by the proper analy~is of pressure buildup data ob~ained from adequately designed tests. 3. Since the build-up curve associated with this type of porous system is similar to that obtained from a stratified reservoir, an unambiguous interpretation is not possible without additional information. 4, Dif@rencing methods which utilize pressure data from the /inal stages of a buik-kp test should be used with extreme caution. INTRODUCTION In order to plan a sound exploitation program or a successful secondary-recovery pro ject, sufficient reliable information concerning the nature of the reservoir-fluid system must be available. Sincef it is evident chat an adequate description of the reservoir rock is necessary if this condition is to be fulfilled, the present investigation was undertaken for the purpose of improving the fluid-flow characterization, based on normally available data, ofs particular porous medium. DISCUSSION OF THE PROBLEM For many years it was widely assumed that, for the purpose of making engineering studies, two psram. . -. . Origlml manuscriptreceived fn eociaty of Petroleum Ertatneere offiae AUS. 17, 1962.Revieed manuscriptreceived.March21, 1963. P eper pr+$eented at the Fetl Meeting of the %ciot Y of. Petreleum Enginsera In Lo= Ar@Ies on Oct. 7-10, 1962. ‘ . GULF RESEARCH d DEVELOPMENT CO. PITTSBURGH, PA, eters were sufficient to desckibe the single-phase flow properties of a prodttcing formation, i.e., the absolute permeability and the effective porosity. It : later became evident that the concept of directional permeability was of more thin academic interest; consequently, the de$ee of permeability anisotropy and the orientation of the principal axes of permeability were accepted as basic parameters governing reservoir performance. 1,2 More recently, 3“6 it was recognized that at least one additional parameter was required to depict the behavior of a porous system containing region,s which contributed significantly to the pore volume but contributed negligibly to the flow capacity. Microscopically, these regions could be “dead-end” or “storage” pores or, microscopically, they could be discrete volumes of lowpermeability inatrix rock combined with natural fissures in a reservoir. It is obvious thst some provision for the ;.ncIusion of all the indicated parameters, as weIl as their spatial vstiations$ must be made if a truly useful, conceptual model of a reaetvoir is to be developed. A dichotomy Qf the internaI voids of reservoir rocks has been suggested, r~s These two classes of porosity can be described as follows: a. Primary porosity is intergranular and controlled by deposition and Iithification. It ie highly intercoririected arid “usually can be correlated with permeability since it is largely dependent on the geometry, size distribution and spatial distribution of the grains. The void systems of sands, sandstones and oolitic limestones are typical of this type. b. Secondary porosity is foramenular and is controlled by fracturing, jointing and/or solution in circulating water although it may be modified by infilling as a result of precipitation. It is not highly interconnected and usually cannot be correlated with permeability. Solution channels or vugular voids developed during weathering or buriaI in sedimentary basins are indigenous to carbonate rocks such as limestones or dolomites. Joints or fissures which occur in massive, extensive formations composed of shale, siltstone, schist, limestone or dolomite are generally vertical, and they are ascribed to tensional failure, during mechanical deformation (the permeability associated with this type of void system is often anisotropic). Shrinkage cracks are the result 1 ~ef&ence. aiven atendof p@er. ‘-

Fundamentals of soil behavior

Abstract: The book is intended to develop an understanding of the factors determining and controlling the engineering properties of soil, the factors controlling their magnitude, and the influences of environment and time. The two-part book contains the following chapters: Part 1 - the nature of soils; bonding, crystal structure and surface characteristics; soil mineralogy; soil formation and soil deposits; determination of soil composition; soil water; clay-water-electrolyte system; soil fabric and its measurement; Part 2 - soil behavior; soil composition and engineering properties; effective, intergranular and total stress; soil structure and its stability; fabric, structure and property relationships, volume change behavior; strength and deformation behavior; and, conduction phenomena. /TRRL/