Showing papers on "Permeability (earth sciences) published in 1983"

Transport processes in wood

Abstract: 1 Basic Wood-Moisture Relationships.- 1.1 Introduction.- 1.2 Saturated Vapor Pressure.- 1.3 Relative Humidity.- 1.3.1 Use of the Psychrometric Chart.- 1.3.2 Measurement of Relative Humidity.- 1.3.3 Control of Relative Humidity.- 1.4 Equilibrium Moisture Content and the Sorption Isotherm.- 1.5 The Effect of Changes in Pressure and Temperature on Relative Humidity.- 1.6 Specific Gravity and Density.- 1.7 Specific Gravity of the Cell Wall and Porosity of Wood.- 1.8 Swelling and Shrinkage of the Cell Wall.- 1.9 Swelling and Shrinkage of Wood.- 2 Wood Structure and Chemical Composition.- 2.1 Introduction.- 2.2 The Cell Wall.- 2.3 Structure of Softwoods.- 2.4 Types of Pit Pairs.- 2.5 Softwood Pitting.- 2.6 Microscopic Studies of Flow in Softwoods.- 2.7 Structure of Hardwoods.- 2.8 Hardwood Pitting.- 2.9 Microscopic Studies of Flow in Hardwoods.- 2.10 Chemical Composition of Normal Wood.- 2.10.1 Cellulose.- 2.10.2 Hemicelluloses.- 2.10.2.1 Introduction.- 2.10.2.2 Softwood Hemicelluloses.- 2.10.2.3 Hardwood Hemicelluloses.- 2.10.3 Lignins.- 2.11 Chemical Composition of Reaction Wood.- 2.11.1 Introduction.- 2.11.2 Compression Wood.- 2.11.3 Tension Wood.- 2.12 Topochemistry of Wood.- 3 Permeability.- 3.1 Introduction.- 3.2 Darcy's Law.- 3.3 Kinds of Flow.- 3.4 Specific Permeability.- 3.5 Poiseuille's Law of Viscous Flow.- 3.6 Turbulent Flow.- 3.7 Nonlinear Flow Due to Kinetic-Energy Losses at the Entrance of a Short Capillary.- 3.8 Knudsen Diffusion or Slip Flow.- 3.9 Corrections for Short Capillaries.- 3.10 Permeability Models Applicable to Wood.- 3.10.1 Simple Parallel Capillary Model.- 3.10.2 Petty Model for Conductances in Series.- 3.10.3 Comstock Model for Softwoods.- 3.10.4 Characterization of Wood Structure from Permeability Measurements.- 3.11 Measurement of Liquid Permeability.- 3.12 Measurement of Gas Permeability.- 3.13 The Effect of Drying on Wood Permeability.- 3.14 Treatments to Increase Permeability.- 3.15 The Effect of Moisture Content on Permeability.- 3.16 The Influence of Specimen Length on Permeability.- 3.17 Permeability of the Cell Wall.- 3.18 Zones of Widely Differing Permeabilities in Wood.- 3.19 General Permeability Variation with Species.- 4 Capillary and Water Potential.- 4.1 Surface Tension.- 4.2 Capillary Tension and Pressure.- 4.3 Mercury Porosimetry.- 4.4 Influence of Capillary Forces on the Pressure Impregnation of Woods with Liquids.- 4.5 Collapse in Wood.- 4.6 Pit Aspiration.- 4.7 The Relationship Between Water Potential and Moisture Movement.- 4.8 Notes on Water Potential. Equilibrium Moisture Content, and Fiber Saturation Point of Wood.- 5 Thermal Conductivity.- 5.1 Fourier's Law.- 5.2 Empirical Equations for Thermal Conductivity.- 5.3 Conductivity Model.- 5.4 Resistance and Resistivity Conductance and Conductivity.- 5.5 Derivation of Theoretical Transverse Conductivity Equation.- 5.6 Derivation of Theoretical Longitudinal Conductivity Equation.- 5.7 R and U Values Convection and Radiation.- 5.8 Application to Electrical Resistivity Calculations.- 5.9 Application to Dielectric Constant Calculations.- 6 Steady-State Moisture Movement.- 6.1 Fick's First Law Under Isothermal Conditions.- 6.2 Bound-Water Diffusion Coefficient of Cell-Wall Substance.- 6.3 The Combined Effect of Moisture Content and Temperature on the Diffusion Coefficient of Cell-Wall Substance.- 6.4 Water-Vapor Diffusion Coefficient of Air in the Lumens.- 6.5 The Transverse Moisture Diffusion Model.- 6.6 The Importance of Pit Pairs in Water-Vapor Diffusion.- 6.7 Longitudinal Moisture Diffusion Model.- 6.8 Nonisothermal Moisture Movement.- 6.9 Measurement of Diffusion Coefficients by Steady-State Method.- 7 Unsteady-State Transport.- 7.1 Derivation of Unsteady-State Equations for Heat and Moisture Flow.- 7.2 Derivation of Unsteady-State Equations for Gaseous Flow in Parallel-Sided Bodies.- 7.3 Graphical and Analytical Solutions of Diffusion-Differential Equations with Constant Coefficients.- 7.3.1 Solutions of Equations for Parallel-Sided Bodies.- 7.3.2 Solutions of Equations for Cylinders.- 7.3.3 Simultaneous Diffusion in Different Flow Directions.- 7.3.4 Significance of Flow in Different Directions.- 7.3.5 Special Considerations Relating to the Heating of Wood.- 7.4 Relative Values of Diffusion Coefficients.- 7.5 Retention.- 7.6 Unsteady-State Transport of Liquids.- 7.6.1 Parallel-Sided Bodies, Permeability Assumed Constant with Length.- 7.6.2 Parallel-Sided Bodies with Permeability Decreasing with Length (Bramhall Model).- 7.6.3 Cylindrical Specimens.- 7.6.4 Square and Rectangular Specimens.- 7.7 Unsteady-State Transport of Moisture Under Noniso-thermal Conditions.- 7.8 Heat Transfer Through Massive Walls.- References.- Symbols and Abbreviations.

The permeability of natural soft clays. Part II: Permeability characteristics

Abstract: The permeability characteristics of a number of intact natural soft clays from Quebec, the USA, and Sweden have been investigated in the laboratory. The variation of permeability with void ratio is...

The effect of the capillary number and its constituents on two-phase relative permeability curves

Abstract: The goal of this study is to determine the effect of the capillary number on two-phase (oil-water) relative permeability curves Specifically, a series of steady-state relative permeability measurements were carried out to determine if the capillary number causes changes in the two-phase permeabilities or if any one of its constituents, such as flow velocity, fluid viscosity, or interfacial tension, are the controlling variables For the core tests, run in fired Berea sandstone, a Soltrol 170 oil-calcium chloride brine-isopropyl alcohol-glycerin system was utilized Alcohol was the interfacial tension reducer and glycerin was the wetting phase viscosifier The non-wetting phase (oil) relative permeability showed little correlation with the capillary number As the interfacial tension decreased below 20 dynes/cm, the oil permeability increased dramatically However, as the wetting phase viscosity increased, the non-wetting phase demonstrated less ability to flow For the wetting phase (water) relative permeability, the opposite capillary number effect was shown For both the tension decrease and the viscosity increase, ie, a capillary number rise, the water permeability increased, but not as much as with the oil curves No velocity effects were noted for the range studied A relative permeability model was then developed from the experimental data, based on fluidmore » saturations, interfacial tension, fluid viscosities, and the residual saturations, using regression analysis The applicability of these regression models were then tested with the aid of a two-phase reservoir simulator« less

Investigation of equivalent porous medium permeability in networks of discontinuous fractures

Abstract: The purpose of this study is to determine when a fracture system behaves as a porous medium and when it does, what is the appropriate permeability tensor for the medium. A volume of fractured rock can be said to behave like a representat ive volume of an equivalent porous medium when' (1) there is an insignificant change in the value of the equivalent permeability with a small addition or subtraction to the test volume and (2) an equivalent permeability tensor exists which predicts the correct flux when the direction of a constant gradient is changed. A two-dimensional fracture system model is developed. The density, size, orientation, and location of fractures in an impermeable matrix are random variables in the model. Simulated flow tests through the models measure directional permeability, Kg. A polar coordinate plot of 1/"Kg will be an ellipse if the medium behaves like a equivalent anisotropic, homogeneous porous medium. Whatever shape the plot is, a best fit ellipse can be calculated and the scatter of measurements around the ellipse is expressed as NMSE, the normalized mean square error. NMSE approaches zero as the behavior approaches that of a continuum. Studies were performed where fracture length and areal density were

Consolidation analysis for partly saturated clay by using an elastic–plastic effective stress–strain model

Abstract: The theory of consolidation is extended to partly saturated clay soils, and formulated for finite element analyses. This formulation couples the effects of both stress and flow. It takes account of variations of this permeability of the soil and compressibility of the pore fluid with changes in void ratio, and the non-linear stress–strain behaviour of soil. The Cam Clay model is revised to model the stress–strain behaviour of compacted soils. The compressibility of pore fluid is derived using Boyle's Law and Henry's Law, taking into account the effect of surface tension. An empirical equation is developed for permeability of pore fluid. An example of settlement of a footing on partly saturated soil is described and discussed.

Experimental investigation on irreversible changes of hydraulic conductivity on the seawater-freshwater interface in coastal aquifers

Abstract: Seawater and fresh groundwater were made to flow through columns filled with samples from a ‘good aquifer’ that contained 5% or less clay minerals. Hydraulic conductivities decreased very sharply whenever seawater was flushed by fresh groundwater. The extent of the decrease depended mainly on the percentage of clays and reached maximum values of 10−1 to 10−3 of the original hydraulic conductivity. Subsequent flushing with seawater restored hydraulic conductivity only in a slight measure, if at all. The mechanism of this process was investigated by using CaCl2 and NaCl solutions with the ionic strengths of seawater and fresh groundwater. It appears that the decrease of hydraulic conductivity is caused by an incipient stage of gel formation. The small water-clay configurations that are formed during this stage behave as practically rigid particles and close the bottlenecks between adjacent pores. The major implications of these findings for groundwater hydrology are as follows: (1) In natural coastal aquifers the seawater-freshwater interface is likely to undergo shifts on a semigeologic time scale. If the aquifer contains even a small percentage of clays, these shifts may create an almost impermeable boundary in the zone of the interface. Hitherto existing theories on movements of the interface regard permeability as constant. (2) The attempt to repel a fresh water-seawater interface by the injection of fresh water may create a practically impermeable boundary within a relatively short time, and thus defeat its own purpose.

Microcrack Permeability in Tight Gas Sandstone

Abstract: A model of stress-dependent permeability was developed on the basis of flow through cracks. The compliance of the cracks is controlled by elastic deformation of a Gaussian distribution of surface asperities, indented into the opposing crack face. The theory was applied to data from tight gas sand cores, with the following results. 1. The theory explains the Jones and Owens permeability correlation/sup 1/ and predicts a modification of it that yields a better fit. 2. The slope of the permeability/stress curve on a loglog plot is predicted to be about 1.0, which agrees with the data. 3. The Jones and Owens Klinkenberg correlation supports a slit-like flow model and indicates that flow occurs along almost every grain boundary. 4. The size of the surface roughness was computed from the Klinkenberg factor and the slope of the permeability/stress curve. It is independent of stress, as predicted by the theory. 5. The porosity of tight sand cores decreases linearly with the log of net confining stress, in accordance with the Walsh-Grosenbaugh model of crack compressibility. This detailed agreement supports the theory and indicates that the permeability of tight gas sand cores is due to microcracks.

Reservoir engineering in coal seams

Abstract: This study examines the behavior of coal seam gas reservoirs which are found to exhibit significantly different behavior from conventional gas reservoirs. These differences involve the nature of permeability variations and the method of gas storage. The permeability variations appear to be caused primarily by effective stress variations and to a lesser extent to water saturation changes. These effective stress changes are brought about both by fluid pressure variations and by coal matrix shrinkage and expansion with changing gas content. Directional permeability with cleat (joint) direction is shown to be important. Experimental work was conducted in underground mines of the Bowen Basin, Queensland, Australia.

A theoretical explanation of solute dispersion in saturated porous media at the Darcy Scale

Abstract: The transport of a nonreactive dilute solute in saturated porous media is explained at three distinct space-time scales. These are the kinetic, microscopic, and Darcy scales. The transition from one scale to the next higher scale, i.e., from the kinetic to the microscopic to the Darcy, is a consequence of the central limit theorem of probability theory. At the microscopic scale, the solid and the liquid phases together form a heterogeneous continuum. The microscopic solute concentration is governed by a parabolic equation with spatially varying drift and diffusion coefficients. The so-called dispersion phenomenon at the Darcy scale is shown to appear in the transition from the microscopic to the Darcy scale. In the computation of the dispersion coefficients, the Peclet number appears naturally as a dimensionless parameter. For large Peclet numbers the coefficients of dispersion at the Darcy scale are shown to be linear in the liquid convective velocity. A general expression is obtained which gives the order of magnitude of the dispersion coefficient for all Peclet numbers within the Darcy regime of the liquid convective velocities. This expression shows that for very small Peclet numbers, only the molecular diffusion provides the dominant contribution, whereas for intermediate values of Peclet numbers, both the liquid convection and the molecular diffusion contribute to the dispersion coefficients; in this range the dispersion coefficients are not linear in the liquid convective velocity. These findings are well supported by existing experimental observations. These theoretical insights into dispersion at the Darcy scale are also important in explaining the so-called macrodispersion and the scale effect at field scales.

Low Interfacial Tension Relative Permeability

Abstract: Enhanced oil recovery processes that feature a near miscible process, CO/sub 2/ injected below the minimum miscibility pressure, or micellar fluids, require relative permeability data to calculate the flow behavior of the low interfacial tension (low IFT) fluids. The flow behavior of low IFT fluids differs from that of conventional gas and oil or water and oil; it depends upon IFT, viscosity, and flow rate as well as the rock properties of pore size distribution and wettability. The results of laboratory core tests using an alcohol, brine, and oil fluid system in outcrop and reservoir rock samples are presented. Both water and oil relative permeability curves were found to shift upward, indicating the 2 phases interfere less with each other as IFT is reduced. For a given reservoir rock type, the flow behavior is adequately characterized by a capillary number defined by combined (total) fluid velocity, average viscosity, and interfacial tension. It also was found that flow tests on representative reservoir rock samples are necessary to describe low interfacial tension relative permeability for field process performance calculations. 16 references.

Low-Permeability Laboratory Measurements by Nonsteady-State and Conventional Methods

Abstract: Evaluation of tight gas reservoirs requires an accurate but rapid and practical method to determine permeability Such a method is presented for determining both specific and effective gas permeability in the 00001- to 035-md range for plug-size core samples Equipment is described that meets the requirements for calculation of nonsteady-state flow and incorporates the capability of simulating high net overburden pressures by either hydrostatic or triaxial confining pressures with ease of operation The time required to collect data and calculate Klinkenberg permeability is typically less than 6 minutes per sample Values normally differ by less than +or -5% from those obtained by steady-state methods This method is well suited for routine laboratory determinations of permeability on samples from reservoirs with tight or very low gas permeability Effective gas permeabilities on samples containing nearly irreducible water saturations and the water permeabilities presented are closer to the Klinkenberg permeability values in low-permeability samples than most previously reported

Effect of alteration on pore structure of crystalline rocks; core samples from Atikokan, Ontario

Abstract: Recent studic indicate that the extensive microDore network within the unfractured rock around major iractures may have a significant effect in reducing the rate of radionuclide migration. The micropore stmcture of granite samples from Atikokan, Ontario has been studied bv analyzing the results of porosity, electrical and permeability mq$urements. The effective porosity, connecting porosity, tortuosity and permeability are calculated from these measurements; their values for these samples are in the order of 0. 1 9-0. 6490, 0.06-0.3 4t10, 1.7 4. 5 and 0. l -54.9 microdarcies, respectively. Results indicate that alteration reduces the connecting porosity and permeability, and increases the tortuosity. This is explained by reduction of the aperture of pore pathways due to dissolution of certain minerals followed by deposition of secondary minerals. The results also suggest that laboratory data for permeability may be extended to field conditions below a certain depth (abour 400 metres).

Method and apparatus for fracturation detection

Abstract: A method and apparatus for detecting cracks or other separations deep inside massive rock-like structures and assessing the integrity and safety of mine roofs and the like, wherein at least one borehole is drilled into the rock and a negative fluid pressure is applied thereto. The permeability of the rock at selected intervals along the borehole is measured and thereby the presence or absence of fractures in the rock is detected. The extension of the fracture to an adjoining hole may be determined by a pressure respond test in the adjoining hole.

Non-abrasive particulate material for permeability alteration in subsurface formations

Abstract: An improved particulate material is disclosed for use in a method for altering the permeability of a gravity override or relatively high permeability path through a subsurface earth formation resulting from fluid injection into the subsurface formation. The method includes adding selectively sized, finely divided, amorphous non-abrasive particulate material to a fluid and injecting the fluid into the gravity override or relatively high permeability path to deposit the particulate material thus altering the permeability in the override, or relatively high permeability path. The particulate material may include graphite, carbon black, clay suspensions, quartz, or other minerals reduced in size range to behave as non-abrasive amorphous material which will present a non-abrasive characteristic in injection wells and if the particulate material is produced with formation fluids from the treated formation.

Porosity and permeability of mesaverde sandstone core from the U. S. DOE multiwell experiment, Garfield County, Colorado

Abstract: Eight higher permeability Mesa Verde sandstone core samples were selected for determination of the effect of fractional water saturation upon permeability. The dry core samples measured porosity, Klinkenberg permeability, and slope, and pore volume compressiblity and pressure. Measurement of the variation in permeability to gas as functions of net stress and water content revealed a dramatic difference between fluvial samples with high pore volume compressibility and paludal samples with lower pore volume compressibility.

Permeability to water of the wood cell wall and its variation with temperature

Abstract: The permeability to water of the cell wall has been measured by applying a known osmotic pressure generated by PEG 6000 across wood samples containing water-swollen cell walls. In pine the void space was filled with silicone resin with the wood at near fibre saturation point. Permeability kx1021 as defined by the Darcy equation was 37.9 m2 for longitudinal flow and 0.96 m2 for tangential flow. Tangential permeability was also measured using water-saturated samples of spruce and lime, and allowance was made for the very high permeability of the water-filled cell cavities. The results were in satisfactory agreement with values obtained previously using wood filled with wax or resin. The variation of tangential permeability with temperature was measured over the range 10–55°C for pine and lime. The activation energy for flow through the cell wall was 6.8 kcal/mole for pine and 5.3 kcal/mole for lime. These values are much higher than the activation energy for viscous flow of water, presumably owing to hydrogen bonding of the water to the cell wall material.

Oil recovery process for stratified high salinity reservoirs

Abstract: There is provided a process for improving oil recovery from stratified reservoirs by (1) injecting low saline water to reduce the salinity in high permeability zones, (2) injecting a surfactant solution into the high permeability zones, (3) injecting high salinity water into the reservoir, thereby forming a surfactant/water/oil emulsion which reduces effective brine permeability in the high permeability zones, and (4) continuing to inject high salinity water into the reservoir, whereby water is diverted to low permeability zones and oil is recovered from the low permeability zones. Low salinity water may then be injected to break-up or release the emulsion in the high permeability zones and to recover oil from the high permeability zones.

Stress-Sensitive Permeability in a High-Permeability Sandstone Reservoir-The Kuparuk Field

Abstract: Buildup test analyses for wells in the Kuparuk field, Alaska, give permeability values that are two to seven times higher than values from drawdown test analyses. Often buildup skins indicate extreme formation damage, while drawdown skins indicate minimal damage. This sandstone reservoir exhibits the characteristics of stress-sensitive permeability. The existence of stress-sensitive permeability was demonstrated using well test analyses, simulation studies, core analyses, and laboratory flow experiments. Comparisons were made for most wells in the field, with significant differences between buildups and drawdowns evident in a majority of the analyses. Simulation of well tests required stress-sensitive permeability to match both buildup and drawdown tests. Core analyses and laboratory flow tests were done to determine the cause and magnitude of the stress-sensitive permeability. Evidence points to open vertical fractures as the cause of this stress-sensitive permeability. These fractures are small-scale, with characteristic heights on the order of inches, and apparently randomly distributed in the reservoir. Because of the fractures' size and distribution, the reservoir behaves as a homogeneous porous medium with stress-sensitive permeability rather than as a classical naturally fractured reservoir. Well tests show no typical fractured reservoir behavior (i.e., linear flow). The extreme effects of stress-sensitive permeability, as seen inmore » this reservoir, can seriously impact field operations.« less

Gas Permeability Determination In Urethane Foams

Abstract: Rigid urethane foam is widely used as a thermal insulation material. One of the reasons for this is its excellent thermal insulation properties, i.e., the initial low thermal conductivity and the retention of K factor with service time. In order to determine apriori the service life of urethane foam insulation systems, the thermal conductivity-time relationships have been investigated extensively. Experimentally, [1-8] both protected and unprotected foams were monitored for their thermal conductivity changes over a long period of time under a variety of service conditions. A number of theoretical studies for the prediction of K factor change with aging on unfaced urethane foams were made by various researchers [2,3,7-10]. Both experimental and theoretical investigations pointed out the paramount importance of the effusion of blowing agents and the infusion of air in controlling the K factor retention characteristics. Norton [2] in his earlier study showed from gas composition determination in the cell a gain of oxygen and nitrogen and a loss of FREON 11 (Trichloromonofluoromethane CC13F) upon aging of

The Permeability of a Random Array of Identical Rigid-Spheres

Abstract: The permeability of a random array of identical rigid-spheres is determined as a function of the radius, a , and the volume concentration, c , of the spheres. A statistical formulation due to Lundgren is used here. A particular state formed around a test sphere, which is called the intermediate layer, is taken into consideration by adding the radial dependence of a coefficient of a Darcy resistance. A resultant equation is solved approximately by Galerkin's method, then the permeability is derived from the solution by using the self-consistency condition. It agrees with the experimental data near c =2/3. Thus, the formula for the permeability of the densely packed bed of spheres is improved.

Laboratory tests to determine hydraulic and thermal properties of bentonite-based backfill materials

Abstract: Terra Tek Research has conducted a testing program on a variety of backfill mixtures to evaluate their thermal and hydraulic properties under conditions expected to be representative of a nuclear waste repository in a deep salt formation. Backfill mixtures were produced by combining bentonite clay with a number of different solid materials, primarily silica sand and crushed salt, in a variety of proportions. Generally, samples were compacted to specified densities, after which appropriate properties were determined. Thermal conductivity and hydraulic conductivity as functions of composition, density and temperature were the principal material properties determined in this program. Additional measurements were performed to determine gas permeability of several mixtures, time-dependent axial deformation of bentonite, water loss from bentonite at elevated temperatures, viscosity of synthetic heavy brines used, and grain size distribution of sands used in the program. Program tests are shown in tabular form which include backfill mixture compositions, test conditions and descriptions of data collected during each test. Measured sand size grain distributions are presented in Appendix A. A discussion of gas (nitrogen) permeability theory and data collected is in Appendix B. A detailed technical discussion of the transient technique of thermal conductivity measurement is given in Appendix C. Brinemore » viscosity data are presented in Appendix D.« less