Showing papers on "Permeability (earth sciences) published in 1984"
TL;DR: In this article, the authors presented data from four projects in which rates of leakage from ponds lined with clay significantly exceeded the rates that would have been predicted on the basis of laboratory permeability tests.
Abstract: Data are presented from four projects in which rates of leakage from ponds lined with clay significantly exceeded the rates that would have been predicted on the basis of laboratory permeability tests. The actual hydraulic conductivities of the clay liners were generally found to be 10 to 1,000 times larger than values obtained from laboratory tests on either undisturbed or recompacted samples of the clay liner. The source of difficulty with laboratory permeability tests is the problem of obtaining a representative sample of soil for testing. Neither recompacted samples nor small, undisturbed samples are likely to contain a representative distribution of desiccation cracks, fissures, slickensides, or other hydraulic defects that may be present in the liner. Field permeability tests were performed for three of the four case histories and yielded results that compared well with field performance. Field permeability tests seem to produce much better results than laboratory tests. The four projects had certai...
225 citations
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01 Jan 1984
142 citations
126 citations
TL;DR: In this paper, changes in stress and corresponding changes in rock mass hydraulic conductivity are analyzed for a circular shaft using simplifying assumptions regarding fracture geometry and initial stress state, and stress distributions around the shaft are calculated using closed-form soltions and are related to changes in hydraulic conductivities using a form of the cubic law for flow through fractured media.
105 citations
TL;DR: In this paper, a series of laboratory experiments was conducted with four ocean sediments, two biogenic oozes and two clays, and the results show no discernible effects of pressure, within the range of 2-60 MPa, upon the permeability of any of the samples.
Abstract: A series of laboratory experiments was conducted with four ocean sediments, two biogenic oozes and two clays. Permeability and thermal conductivity were directly measured as a function of porosity, and the testing program was designed to identify any dependence of these physical properties upon hydrostatic pressure and temperature. The results show no discernible effects of pressure, within the range of 2–60 MPa, upon the permeability of any of the samples. Temperature effects, from 22° to 220°C, upon this property are accounted for by applying a viscosity correction to the permeating seawater. Previous investigations have suggested the existence of a pressure-induced and/or a temperature-induced breakdown of the absorbed water which surrounds clay particles, thereby promoting an increase in sediment permeability. Our experimental findings cannot confirm this phenomenon and fail to provide a satisfactory solution to the conflicting data which now exist between the pore water velocities inferred from nonlinear thermal profiles of ocean sediments and those fluid velocities derived from Darcy's law and laboratory permeability data. The effects of sizeable variations in pressure and temperature upon sediment thermal conductivity are found to reflect closely the behavior of the conductivity of the liquid phase alone under these same changes in environmental conditions. This is not surprising due to the relatively narrow range of high porosities encountered in this study. Empirical equations are developed which allow sediment thermal conductivity to be calculated as a function of temperature and void ratio. A hydrostatic pressure correction term is also presented.
102 citations
TL;DR: A boundary integral equation method (BIEM) for Darcy's flow with spatially varied permeability is developed in this article, which requires that Green's function be found for each given permeability variation.
Abstract: A boundary integral equation method (BIEM) for Darcy's flow with spatially varied permeability is developed The formulation requires that Green's function be found for each given permeability variation For a few permeability functions in one and two dimensions, which can be used to fit field permeability data, closed-form Green's functions are obtained Numerical examples are solved and verified
91 citations
TL;DR: Permeability tests were performed on materials of differing grain size and shape of gradation as discussed by the authors, and it was found that permeability was primarily dependent on and was practically independent of the shape of the gradients.
Abstract: Permeability tests were performed on materials of differing grain size and shape of gradation. It was found that permeability was primarily dependent on and was practically independent of the shape...
86 citations
TL;DR: In this article, a mixed finite-element procedure is proposed to solve for both the pressure and velocity of the total fluid simultaneously as a system of first-order partial differential equations, which minimizes the difficulties occurring in standard methods caused by differentiation or differencing of p and multiplication by rough coefficients k/..mu.
Abstract: Effective numerical simulation of many EOR problems requires very accurate approximation of the Darcy velocities of the respective fluids. In this paper the authors describe a new method for the accurate determination of the Darcy velocity of the total fluid in the miscible displacement of one incompressible fluid by another in a porous medium. The new mixed finite-element procedure solves for both the pressure and velocity of the total fluid simultaneously as a system of first-order partial differential equations. By solving for u=(-K/..mu..) p as one term, we minimize the difficulties occurring in standard methods caused by differentiation or differencing of p and multiplication by rough coefficients k/..mu... By using mixed finite elements for the pressure equation coupled in a sequential method with a finite element procedure for the concentration of the invading fluid, we are able to treat a variety of problems with variable permeabilities, different mobility ratios, and a fairly general location of injection and production wells. Mixed finite-element methods also produce minimal grid-orientation effect. Computational results on a variety of two-dimensional (2D) problems are presented.
85 citations
TL;DR: In this paper, the authors present correlation equations which relate permeability, maximum dry density and optimum moisture content with classification properties of the soils, and the correlation equations were developed for each of these properties.
Abstract: This paper presents correlation equations which relate permeability, maximum dry density and optimum moisture content with classification properties of the soils. The correlation equations were dev...
79 citations
TL;DR: In this paper, a simple network model of pore space in rocks is developed with which permeability and bulk modulus as a function of confining pressure can be calculated, based on the analogy of fluid flow in Darcy's law to current flow in Ohm's law.
Abstract: A simple network model of pore space in rocks has been developed with which permeability and bulk modulus as a function of confining pressure can be calculated. Pores are modeled as straight conduits with circular, elliptic, or tapered cross sections. The interconnection of these conduits is modeled by emplacing them in regular two-dimensional hexagonal, square, or triangular networks. Flow through each conduit is modeled using Poiseuille's law. Flow through the network is calculated based upon the analogy of fluid flow in Darcy's law to current flow in Ohm's law. An estimate of the effective bulk modulus is obtained by summing the contributions of the individual pores. The effect of confining pressure on permeability and bulk modulus is determined by the solid properties and the shape of the pores. For appropriate aspect ratio distributions, the permeability and bulk modulus characteristics of the network model are similar to those found for laboratory rock samples. For rocks of moderate porosity, like sandstone, the model predicts that the bulk modulus is most affected by small, low aspect ratio pores. In contrast, for rocks like granite and tight sandstones (permeability less than 0.5 mdarcy) in which there are relatively few round pores, the bulk modulus and the permeability are both controlled by easily deformed pores. These types of responses are observed in experimental data. The success of the model in predicting these general bulk modulus and permeability responses indicates that while the models presented are too simple to represent a rock completely, the network theory approach is a promising method for modeling porous media.
77 citations
TL;DR: In this article, a resistivity technique has been developed and used to monitor the changes in permeability of five mortars and one concrete on exposure to sea-water, and all mixes studied showed a fall in their permeability on immersion in sea water.
Abstract: Synopsis Permeability is a fundamental property governing the durability of concrete in the marine environment and it has only recently been appreciated that some concretes exhibit a very significant reduction in permeability on immersion in sea-water. To investigate this phenomenon further, a resistivity technique has been developed and used to monitor the changes in permeability of five mortars and one concrete on exposure to sea-water. All mixes studied showed a fall in permeability (increase in resistance) on immersion in sea- water. Indeed 25 mm thick specimens of the two most permeable mortars showed a fall equivalent to over 20 mm of additional thickness after only 10 weeks. This increase is due to the formation of an aragonite-brucite layer on the surface of the mortar plus a more widespread progressive constriction of the cement paste pore system. This effect also has a considerable influence upon the absorption capacity of concrete after a period of drying, which is important in the tidal and sp...
01 Jan 1984
TL;DR: In this article, detailed analyses of more than 50 core samples of western tight sands have resulted in several unanticipated observations that are set forth in this paper, including porosity, pore volume compressibility, stress dependence of permeability to gas, and slope of the Klinkenberg plot (permeability at constant net stress vs the inverse of pore pressure).
Abstract: Detailed analyses of more than 50 core samples of western tight sands have resulted in several unanticipated observations that are set forth in this paper. Core analyses performed under stress representative of producing conditions provided data on porosity, pore volume compressibility, stress dependence of permeability to gas, and slope of the Klinkenberg plot (permeability at constant net stress vs. the inverse of pore pressure). Scanning electron microscope (SEM) and petrographic microscope analyses were performed on samples cut from the ends of core plugs tested. The microscopic studies were explicitly directed toward observing the <0.1 micron flow path openings deduced from permeability data. All samples were from depths that were either known to be gas producers or judged likely to be producers on the basis of wireline log analysis.
TL;DR: In this paper, a numerical simulation of double-packer tests in hypothetical formations of a priori known permeability, with the rate of flow and the water overpressure at quasi steady state measured as in a real packer test, is presented.
TL;DR: In this paper, a generalized Darcy's law (Dagan, 1979) is adopted to describe the oscillatory flow motions in the sea bed and a boundary-layer-Poincare method is used to derive the damping rate and to obtain the small wave number shift due to viscosity.
TL;DR: In this article, a relationship between fracture permeability and attenuation of Stoneley waves was obtained on the basis of a physical mechanism, which involves an energy transfer under the form of a fluid flow inside permeable formations, applied to the cases of a single open fracture, a multi-fractured medium and a homogeneous porous medium.
Abstract: Development of borehole geophysics has recently focused on reservoir characterization. Within this effort, extensive full waveform acoustic surveys have demonstrated a correlation between the occurance of open fractures and attenuation of Stoneley waves. A relationship is obtained here between fracture permeability and attenuation of Stoneley waves, on the basis of a physical mechanism. This mechanism involves an energy transfer under the form of a fluid flow inside permeable formations. It is applied to the cases of a single open fracture, a multi-fractured medium and a homogeneous porous medium. Theoretical results show the effects of frequency, borehole radius, permeability, fracture density and porosity on attenuation. The single fracture theory is applied to observed attenuation data due to isolated large open fractures: the theoretical fracture apertures obtained compare favorably to values determined from packer tests.
01 Jan 1984
TL;DR: In this paper, the authors found that the amount of FGD porosity developed was a function of the sandstone's initial permeability, and they proposed that clay and organic maturation in shales produce the necessary water, acid, and complexing agents for FGD.
Abstract: Framework grain dissolution (FGD) involving feldspars and rock fragments was found to be significant to reservoir properties in sandstones with more than 10% soluble grains. FGD porosity ranged up to approximately 70% and averages about 30% of the visible porosity in a study of some reservoir sandstones. FGD does not appreciably increase reservoir permeability. However, the amount of FGD porosity developed was found to be a function of the sandstone's initial permeability. We propose that clay and organic maturation in shales produce the necessary water, acid, and complexing agents for FGD. The FGD solvent is expelled into the sandstones where feldspars and rock fragments are dissolved, and the resulting aqueous aluminum is complexed for transport out of the sandstone.
13 Feb 1984
TL;DR: In this paper, a pore network model is described which is generated from laboratory derived pore size distribution data and the incorporation of particle capture mechanisms enables it to be used to predict the reduction in permeability of a core arising from injection fluids.
Abstract: Pressure maintenance by sea water injection is part of many offshore field developments. Experiences gained over the last decade in the North Sea, where there is a wide variance in the systems used, appears not to have clarified design specifications. The paper describes various approaches to analysing water quality criteria with reference to water injection schemes and presents the philosophy of the interrelated approach of laboratory experiments, theoretical models and well injectivity predictions in relation to reservoir characteristics. Results are presented from a laboratory and modelling investigation of permeability impairment as a function of the depth of invasion. A pore network model is described which is generated from laboratory derived pore size distribution data. Predictions of permeability from the model are compared to experimental values and good agreement is demonstrated. The incorporation into the model of particle capture mechanisms enables it to be used to predict the reduction in permeability of a core arising from injection fluids. Another modelling approach is described where the contribution of pore size to permeability is demonstrated. Water quality experimental results are presented showing permeability profiles obtained using a multiport pressure tapped core holder which demonstrate local permeability impairment as a function of particle sizemore » and rock properties. The results of one modelling approach is applied in the paper to the prediction of well injectivities and filtration requirements.« less
01 Jan 1984
TL;DR: In this paper, the authors show that natural earth materials are rather heterogeneous in terms of their hydrologic properties, and that the variation of hydraulic conductivity or permeability is not completely disordered in space.
Abstract: It is becoming widely recognized that natural earth materials are rather heterogeneous in terms of their hydrologic properties. Figure 1 shows observations of permeability and porosity in a sandstone aquifer in Illinois. These data are based on laboratory analysis of cores collected from deep boreholes in the Mt. Simon aquifer in central Illinois. The variation of permeability is seen to be rather large; the values range over four orders of magnitude. Porosity on the other hand shows a somewhat smaller degree of variability but still a significant percentagewise change. Figure 2 is the second example of the variability of permeability in earth materials. These data show observed infiltration rates of surface soils along a transect some 700 m long in an irrigated area near Socorro, New Mexico. Here the saturated hydraulic conductivity is seen to vary over two orders of magnitude. The observations in Figure 1 and 2 also illustrate that the variation of hydraulic conductivity or permeability is not completely disordered in space. There is some spatial structure which should be taken into account when considering the effects of such heterogeneity. Many other observations from different geologic environments show similar kinds of natural variability of permeability and other properties.
TL;DR: Permeability changes during creep are a result of the competing processes of dissolution, precipitation and dilatant microcracking as mentioned in this paper, which could have ramifications which are beneficial for waste isolation, but deleterious for geothermal energy extraction schemes.
Abstract: Permeability was measured during creep deformation of a tight sandstone and a granite at upper crustal conditions. With water at 100°C as the pore fluid, permeability first decreased then increased during loading to peak stress. Thereafter, permeability decreased as much as 50% over time, even though sample volumetric strain indicated continuous dilatant creep. A silica-rich precipitate was found at the ends of the specimens and etch pits found on quartz grain surfaces. From these observations, we infer that permeability changes during creep are a result of the competing processes of dissolution, precipitation and dilatant microcracking. Depending upon deformation rates, this could have ramifications which are beneficial for waste isolation, but deleterious for geothermal energy extraction schemes.
TL;DR: In this paper, the amplitude of the water level oscillations induced by small harmonic gravity variations of the earth tides and the phase lag relative to the tide are related to the reservoir porosity and permeability.
Abstract: Summary. Periodic gravity perturbations, known as earth tides, produce minute expansions and contractions of subsurface geologic formations. The motions induce water level oscillations in wells connected to the deep reservoirs, and a measurable phase lag occurs between the maximum gravity and the maximum water level. The amplitude of the water level oscillations induced by the small harmonic gravity variations of the earth tides and the phase lag relative to the tide are related to the reservoir porosity and permeability.
The motions of an elastic subsurface reservoir are analysed by considering an axially symmetric system of finite volume which is activated by oscillations of a rigid rock mass overlying the reservoir. The geometric parameters involved are the thickness of the reservoir, radial extent, depth and fluid level in the well. The physical parameters for which data are available or satisfactory estimates can be made are the fluid viscosity, densities, temperature, compressibilities and shear modulus. These properties refer to in situ conditions at large overburden pressure. Permeability and porosity at in situ conditions are not directly measurable, and methods of indirect estimation are of practical interest. This analysis correlates these two parameters with the amplitude and phase lag of the induced well fluid oscillation.
For the very small strains and fluid volume fraction changes induced by the tides, slow flow of a viscous fluid through an isotropic porous matrix is assumed. An axially-symmetric analysis for a uniform permeable layer perturbed by the oscillations of the rigid overburden rock yields explicit expressions for the oscillation amplitude and phase in the well. Selected results from numerical solutions having a wide range of realistic parameter values are presented. The results clearly show the dependence of amplitude and phase lag on the dimensionless permeability, and the near proportionality of the amplitude on the reciprocal of the porosity (porosity has no other significant influence). Finally, it is shown how asymptotic approximations of the direct solution allow an inversion which determines the permeability and porosity in terms of the amplitude and phase lag, given the other reservoir properties.
01 Dec 1984
TL;DR: In this paper, a number of constant head tests have been conducted on mechanically-mixed sand samples for the laboratory tests based on the laboratory test results, it appears that the permeability coefficient can be correlated to the effective size, uniformity coefficient, and the void ratio of sand.
Abstract: The coefficient of permeability is an important parameter in the estimation of seepage through soil In order to develop a better understanding of the variation of the coefficient of permeability of sands, a number of constant head tests have been conducted Twenty mechanically-mixed sand samples have been used for the laboratory tests Based on the laboratory test results, it appears that the permeability coefficient can be correlated to the effective size, uniformity coefficient, and the void ratio of sand (Author/TRRL)
TL;DR: The unsaturated zone at Yucca Mountain, Nevada, is being evaluated as a potential repository for high-level nuclear wastes as discussed by the authors, and estimates of ambient moisture tension, effective hydraulic conductivity, and vertical flux are needed to design additional investigations and to develop preliminary models of the geohydrologic system.
Abstract: The unsaturated zone at Yucca Mountain, Nevada, is being evaluated as a potential repository for high-level nuclear wastes Estimates of ambient moisture tension, effective hydraulic conductivity, and vertical flux are needed to design additional investigations and to develop preliminary models of the geohydrologic system In deep unsaturated zones of uniform properties, hydraulic-head gradients are unity, and effective hydraulic conductivity may be used to estimate vertical flux Analyses were made on 19 core samples of unsaturated tuff from test well USW H-1 Moisture-characteristic curves relating saturation and moisture tension were developed from results of mercury-injection tests Ambient moisture tension estimated from these curves generally was 100 to 200 kilopascals Values of relative permeability ranging from about 0002 to 01 were determined by fitting an analytical expression to eight of the moisture-characteristic curves, and then integrating to solve for relative permeability These values of relative permeability were applied to values of saturated hydraulic conductivity of core from a nearby test well to obtain effective hydraulic conductivities of about 8 x 10{sup -12} to 7 x 10{sup -10} centimeter per second If a unit hydraulic-head gradient is assumed, these values convert to a vertical flux through the tuff matrix of 0003 to 02more » millimeter per year The validity of this assumption was not verified due to the sparseness of data and uncertainties in their reliability Consequently, the results of this study are preliminary and need to be used only as a guide for future studies 9 references, 30 figures, 1 table« less
TL;DR: In this article, the authors describe the construction and operation of an apparatus for the measurement of concrete permeability, which is cast in epoxy resin before insertion in a pressure cell.
Abstract: This paper describes the construction and operation of an apparatus for the measurement of concrete permeability. The concrete samples used in the apparatus are cast in epoxy resin before insertion in a pressure cell. Uniaxial water flow, under pressures up to 3.5 MPa, is ensured by O-ring seals.Results are presented for the permeability of laboratory samples with water/cement ratios varying from 0.35 to 0.75. Key words: concrete, permeability, apparatus.
01 Jan 1984
TL;DR: In this article, a pressure-permeability relation has been used with a numerical, two-phase coalbed methane simulator to examine the effect of pressure dependent coal sample permeability on well-tests and on production of coal-bed methane.
Abstract: Laboratory measurements have shown that the permeability of coal samples varies significantly for ranges of pressure encountered during the testing of coalbed methane wells. A laboratory pressure-permeability relation has been used with a numerical, two-phase coalbed methane simulator to examine the effect of pressure dependent permeability on well-tests and on production of coalbed methane.
01 Jan 1984
TL;DR: In this article, the behavior of water permeability as a function of net stress in coalbeds was studied and the results showed that water permeabilities of a given sample decreased by as much as two orders of magnitude over pressure ranges that simulated normal dewatering and production cycles.
Abstract: Coalbed methane production is initiated by the removal of formation water in quantities sufficient to accomplish a large reduction of fluid pressure in the cleat system. Pressure reduction causes gas to be desorbed from the coal; the cleat system channels this gas to the wellbore. The rate and quantity of water removal is limited by permeability of the cleat system which is usually stimulated to facilitate dewatering and gas production. Experiments were performed at IGT under in-situ conditions on coal from five U.S. basins. Results showed that water permeability of a given sample decreased by as much as two orders of magnitude over pressure ranges that simulated normal dewatering and production cycles. Knowledge of the behavior of permeability as a function of net stress allows a better understanding of the following realities of coalbed stimulation: 1) a horizontal drill hole of a given length is much more productive than a propped fracture of the same length; 2) in general, fractures induced in coalbeds are much shorter and wider than designed; and, 3) frac pressures in coalbeds are abnormally high significantly above overburden in many cases. Other consequences of a permeability-net stress functionality include: 1) skin factor determinations from injection testsmore » are necessarily more optimistic than those based on drawdown data; 2) overbalanced drilling increases the invasion radius of drilling fluid filtrate, thereby creating the potential for more extensive formation damage than in conventional reservoirs; and, 3) leakoff during fracturing operations is significantly higher than for ''conventional'' sandstone or limestone beds having identical pre-injection permeabilities.« less
TL;DR: In this paper, gas-production characteristics of naturally fractured Devonian shale have been quantified through a three-well interference field test by use of an established producing well and two offsets placed on the primary and secondary regional fracture trends relative to the producer.
Abstract: Gas-production characteristics of naturally fractured Devonian shale have been quantified through a three-well interference field test by use of an established producing well and two offsets placed on the primary and secondary regional fracture trends relative to the producer. Three individual shale zones were evaluated simultaneously by buildup, drawdown, and pulse tests to investigate reservoir gas flow characteristics, natural fracture properties, and gas storage and release mechanisms. Test results show severe permeability anisotropy, indicating elliptical drainage pattern with an 8:1 axis ratio. Essentially all gas is stored in a sorbed state in the shale matrix and is transported toward the wells through the native fracture system.
TL;DR: In this article, a detailed comparison between the hydraulic conductivity and resistivity, respectively, and the character of fractures in the core and the borehole wall is made to get a better understanding of the influence of fractures on resistivity and permeability.
01 Jul 1984
TL;DR: In this paper, the effects of scale and time on hydraulic fracturing in compacted samples of Teton Dam silt and Pittsburg silty clay were investigated and a theory was developed to show how size of opening, time of pressurizing opening, and soil permeability are related to the occurrence of hydraulic fracturing.
Abstract: : An experimental study was conducted to determine the effects of scale and time on hydraulic fracturing in compacted samples of Teton Dam silt and Pittsburg silty clay. A theory was developed to show how size of opening, time of pressurizing opening, and soil permeability are related to the occurrence of hydraulic fracturing. Finite element analyses were used to investigate the possible effects of nonlinear soil behavior. Both experimental and theoretical studies show that hydraulic fracturing can be initiated by seepage-induced forces without the presence of a preexisting flaw in the soil. (Author)