Showing papers on "Permeability (earth sciences) published in 1978"

A note on permeability changes in geologic material due to stress

Abstract: Stress produces dramatic changes in fluid permeability of geologic materials. An increase of nearly threefold occurred in granite at high stress, an increase of 20 percent in sandstone, and a hundredfold decrease in compacted sand. Permeability of sand and sandstone did not follow the effective stress law. Flow along joints was very sensitive to effected stress changes, a fourfold change being caused by as little as 1.0 MPa.

Influence of cellular membrane permeability on drying behavior

Abstract: The basic transport equations and alternative cellular membrane permeability definitions are reviewed. An analysis of data on osmotic and diffusional permeability and a discussion of boundary layer resistances allows a representative water permeability value to be chosen. The rate of drying for a cellular membrane water permeability controlled drying experiment is then predicted for two extreme cases of convective contribution to the diffusional rate. Experimental results indicate that in the case of apples the drying phenomenon is not controlled by the cellular permeability.

Petrographical factors relating to porosity and permeability in the fell sandstone

Abstract: Samples of Fell Sandstone were taken from approximately every 3 m from the core material left at Shirlawhope Well, Longframlington, Northumberland. Most of the core remains and it extends to a depth of 94 m. Various analyses were made at each 3 m depth interval. These included a modal analysis, particular attention being given to the cement and matrix material, as well as the void space; and a petrographic analysis of grain packing. Grain size analyses were also carried out at each depth to determine the individual median size and sorting coefficients. The absolute and effective porosities were obtained for each depth interval, together with permeabilities of intact specimens. The results of the individual parameters were compared statistically by means of correlation coefficients and Student9s t tests in order to evaluate the significance of their relationships. Porosity and permeability were shown to be influenced by void percentage and grain packing. Particle size distribution, however, does not influence porosity, although it has some influence on permeability. Cement-matrix content has little influence on porosity. A highly significant relationship was found to exist between effective porosity and permeability. Both porosity and permeability decrease with increasing depth from the surface.

The Optimization Of Well Spacing And Fracture Length In Low Permeability Gas Reservoirs

Abstract: This study describes a process for optimizing well spacing and fracture length in a low permeability gas reservoir. Three examples are discussed which represent a high permeability, a low permeability, and a medium permeability gas reservoir. The results from these investigations suggest that the solution is not always intuitively obvious. The complex interaction of the variables involved in each problem almost necessitates the use of a computer model to optimize the exploitation of a tight gas reservoir. Numerous computer runs have been made to illustrate the economic optimum fracture lengths for a variety of reservoir cases.

Diffusional water permeability in selected marine bivalves

Abstract: 1. The diffusional water permeability of the isolated mantle tissue from a series of marine, and one freshwater, species of lamellibranch molluscs was determined.2. The water permeability of the mantle tissue was generally correlated with the habitat of the organism, permeability decreasing with increasing height above the sublittoral zone.3. Evidence is presented that a given intertidal lamellibranch species, Mytilus edulis, is capable of altering its tissue water permeability when presented with changes in external osmolality.4. The observed differences in tissue water permeability from different animals are not due to change in the physical dimensions of the tissue, but may be the result of changes in the chemical composition of the tissue.

The water permeability of the human erythrocyte in the temperature range +25CÌ to -10CÌ

Abstract: Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Shaping and sintering porous ceramic oxide products - to obtain controlled porosity in finished articles, esp. for filters, catalyst supports etc.

Abstract: Method of shaping and sintering mfd. products with determined characteristics of porosity and permeability, esp. porous tubes entirely made of Al2O3 or other high purity oxides, consists of dry or wet granulating finely powdered oxide to achieve granules having an apparent density of 40% of theoretical density and particle size 25-75 mu, adding thickeners and/or binders then shaping to a tube or similar shape by compression moulding e.g. by isostatic pressing or extrusion etc., then sintering in air or combustion gas at a temp. increasing to 1550-1780 degrees C with a period of 1 hr at max. temp. followed by cooling. Improved control over the porosity and permeability can be achieved, esp. with varying shapes.

The Relationship between the Axial Permeability of Wood to Dry Air and to a Non-Polar Solvent

Abstract: The different approaches to the use of steady-state gas flow data in the prediction of the steady-state axial permeability of wood to liquids are reviewed. Since these may be shown to have certain theoretical shortcomings, a new predictive method based on a computer analysis is presented. This and previous methods are tested experimentally; apparently, none can be relied upon to predict the liquid permeability accurately. However, it is clear that the true liquid permeability is not measured; the reasons for this are uncertain. Until this difficulty is resolved, the precision of predictive methods cannot be accurately assessed.

An experiment to verify the permeability of Hele‐Shaw cells

Abstract: A fluid layer sandwiched between 2 flat plates (Hele-Shaw cell) has been assumed to model a saturated porous medium with permeability, D2/12, dependent only on the gap width, D. For situations where the properties of the porous matrix are important, such as thermal convection, the total cross section (Y) of the sandwich should enter into the computation of permeability. To decide which of these approaches is valid, the onset of convection was observed in a Hele-Shaw cell with constant gap width but spatially varying wall thickness. Convection begins in the thin-walled section at a lower temperature difference than it does where the walls are thick. Data confirm that D3/12Y is the permeability of Hele-Shaw cells used to model thermal convection in porous layers.

Estimation of aquifer permeabilities from electric well logs

Abstract: Evidence from core data and log studies shows that permeability is related to formation resistivity factor. Empirical correlation relating the two rock parameters is determined using core data. Knowing the formation resistivity factor from electric logs, it is possible to calculate the permeability of a given formation interval. Field examples show that the proposed method is applicable in both water bearing and hydrocarbon bearing zones. The ability to predict the permeability of water bearing zones from electric well logs is of great importance in the assessment of aquifers geopressure energy resource.

Measurement of the Average Pore Velocity of Water Flowing Through a Rock Specimen

Abstract: Measurement of the Average Pore Velocity of Water Flowing Through a Rock Specimen. This paper describes a method to measure the modified permeability referring to the average pore velocity instead of the filter velocity. In many applications like for instance in erosion of rock with a high speed water jet the modified permeability is of interest. The principle of the method is to introduce a small amount of ions at a certain time in the water passing through a rock specimen and record the electric current due to a voltage in the direction of the pressure gradient. The record of the current will then show a rather steep increase after a defined time. This time makes it possible to calculate the average pore velocity. Experiments have been performed with three Swedish rocks, Lemunda sandstone, Bohus granite and Stockholm granite. The results show that the permeability of the granites is much less than that of the sandstone.

Factors affecting water blocking and gas flow from hydraulically fractured gas wells

Abstract: This study presents results which were generated and analyzed over a 2-yr period. Several hundred computer runs were made during this project and an extensive amount of rock property data was reviewed to insure that these data were representative of tight gas reservoirs. The following conclusions reflect the combined information which was generated during the study. The reservoir properties, such as capillary pressure, change of capillary pressure in damaged zones, and relative permeability (in low permeability gas reservoirs) are primary factors in determining the behavior of a fractured well during cleanup. If the reservoir rock permeability is not damaged by frac fluid invasion, no serious water blockage to gas flow will occur when (1) the pressure drawdown is much greater than the capillary pressure in the formation, or (2) the capillary pressure and water mobility are large enough to rapidly imbibe the frac water into the formation. If the reservoir rock permeability is not damaged by frac fluid invasion, a complete water block to gas flow cannot occur; however, gas production can be severely curtailed if the pressure drawdown does not exceed the formation capillary pressure and the water mobility is so low that the frac water remains immobile nextmore » to the fracture face.« less

Equivalence of Air and Water Permeability Tests in Evaluating Engineering Fabrics

Abstract: Permeability characteristics of civil engineering filter fabrics are currently evaluated by three types of tests: air permeability and falling-head and constant-head water permeability. Test procedures for the falling-head and constant-head water permeability tests are discussed, and results from these tests are correlated to air permeability results for filter fabrics. Several commercially available filter media were tested by these methods and a high degree of linearity between the tests was observed.

Improving method for water permeability of porous plastic membrane

Abstract: PURPOSE:To increase water permeability of porous plastic membrane without change in porosity and pore size by the sputter etching of the membrane at a specific atmosphere pressure and under the specific conditions depending on the product of power density and treating time.

Permeability of conical shells deep drawn from porous sheet

Abstract: The distribution of permeability over the surface of a deep-drawn shell from a porous sheet is determined by its stress-strain state. The permeability of a conical shell increases in the direction of its narrower end.

Factors Affecting The Design Of Hydraulic Fracturing Treatments

Abstract: Hydraulic fracturing as a method of oil and gas well stimulation has evolved into a highly sophisticated science. The process creates a highly conductive flow channel which penetrates deeply into a producing formation. The design of an effective and efficient fracturing treatment becomes complicated due to the great number of variables which affect the outcome of the treatment. Rock properties (porosity, permeability, composition, and strength), rock mechanics (existing stresses, and behavior of rock under applied stress), type reservoir fluids (oil, gas, water or mixtures), and reservoir properties (depth, temperature, and pressure) all must be considered in the selection of the best fluid, best rate, best prop size and concentrations, and most economical volume to be used. This work discusses the effects of the various parameters and, by an example design problem, attempts to show how all can be considered to arrive at the most effective treatment to meet a given set of conditions.

Full-scale investigations of seepage in an experimental blast-fill dam

Abstract: 1. The seepage flow through the experimental dam is of a complex nature spatially. The law of motion of the seepage flows is nonlinear, i.e., it does not follow Darcy's law. The permeability of the soils composing the structure varies over a large range. 2. A characteristic feature of blast-fill dams is the zonal variation in the granulometric composition and, consequently, the permeability coefficient. In the central zone the material contains a greater quantity of fine fractions and is placed more compactly than in the shoulders.