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Showing papers on "Permeability (earth sciences) published in 1994"


Journal ArticleDOI
TL;DR: The coefficient of permeability for unsaturated soil is primarily determined by the pore-size distribution of the soil and can be predicted from the soil-water characteristic curve as mentioned in this paper.
Abstract: The coefficient of permeability for an unsaturated soil is primarily determined by the pore-size distribution of the soil and can be predicted from the soil-water characteristic curve. A general eq...

864 citations


Journal ArticleDOI
TL;DR: In this article, the authors quantified fault zone permeability in outcrop by detailed geologic mapping and by measurements using a minipermeameter, and found that deformation bands have porosity about one order of magnitude less than the surrounding host rock.
Abstract: Fault zone permeability in outcrop is quantified by detailed geologic mapping and by measurements using a minipermeameter. Deformation bands, zones of deformation bands, and slip planes are structural elements associated with successive stages in the evolution of a fault zone in porous sandstones. Deformation bands have a porosity about one order of magnitude less than the surrounding host rock and, on average, a permeability three orders of magnitude less than the surrounding host rock. The intensity of cataclasis and the clay content control the amount of permeability reduction as measured perpendicular to a band. The wall rock in proximity to slip planes can have permeabilities more than seven orders of magnitude less than the pristine sandstone. Capillary pressure wit in deformation bands is estimated to be 10-100 times larger than that in the surrounding host rock. Thus, deformation bands and slip planes can substantially modify fluid flow properties of a reservoir and have potential sealing capabilities with respect to a nonwetting phase, as evident in outcrop exposure.

595 citations


Journal ArticleDOI
TL;DR: In this paper, the dependence of pore pressure and porosity on the pore structure and its compressibility has been investigated experimentally in five sandstones with porosities ranging from 14% to 35%.
Abstract: Permeability exerts significant control over the development of pore pressure excess in the crust, and it is a physical quantity sensitively dependent on the pore structure and stress state. In many applications, the relation between permeability and effective mean stress is assumed to be exponential and that between permeability and porosity is assumed to be a power law, so that the pressure sensitivity of permeability is characterized by the coefficient γ and the porosity sensitivity by the exponent α. In this study, we investigate experimentally the dependence of permeability on pressure and porosity in five sandstones with porosities ranging from 14% to 35% and we review published experimental data on intact rocks, unconsolidated materials and rock fractures. The laboratory data show that the pressure and porosity sensitivities differ significantly for different compaction mechanisms, but for a given compaction mechanism, the data can often be approximated by the empirical relations. The permeabilities of tight rocks and rock joints show relatively high pressure sensitivity and low porosity sensitivity. A wide range of values for α and γ have been observed in relation to the mechanical compaction of porous rocks, sand and fault gouge, whereas the porosity sensitivity for chemical compaction processes is often observed to be given by α≈3. We show that since the ratio γ/α corresponds to the pore compressibility, the different dependences of permeability on porosity and pressure are related to the pore structure and its compressibility. Guided by the laboratory data, we conduct numerical simulations on the development of pore pressure in crustal tectonic settings according to the models ofWalder andNur (1984) andRice (1992). Laboratory data suggest that the pressure sensitivity of fault gouge is relatively low, and to maintain pore pressure at close to the lithostatic value in the Rice model, a relatively high influx of fluid from below the seismogenic layer is necessary. The fluid may be injected as vertically propagating pressure pulses into the seismogenic system, andRice's (1992) critical condition for the existence of solitary wave is shown to be equivalent to α>1, which is satisfied by most geologic materials in the laboratory. Laboratory data suggest that the porosity sensitivity is relatively high when the permeability is reduced by a coupled mechanical and chemical compaction process. This implies that in a crustal layer, pore pressure may be generated more efficiently than cases studied byWalder andNur (1984) who assumed a relatively low porosity sensitivity of α=2.

548 citations


Journal Article
TL;DR: In this paper, the pore dimension is used to predict porosity and other measurable rock parameters, such as grain, surface area, or pore dimensions, and the results show that porosity reduction is always accompanied by a reduction in characteristic pore size.
Abstract: In many consolidated sandstone and carbonate formations, plots of core data show that the logarithm of permeability (k) is often linearly proportional to porosity (0). The slope, intercept, and degree of scatter of these log(k)-0 trends vary from formation to formation, and these variations are attributed to differences in initial grain size and sorting, diagenetic history, and compaction history. In unconsolidated sands, better sorting systematically increases both permeability and porosity. In sands and sandstones, an increase in gravel and coarse grain size content causes k to increase even while decreasing. Diagenetic minerals in the pore space of sandstones, such as cement and some clay types, tend to decrease log(k) proportionately as 0 decreases. Models to predict permeability from porosity and other measurable rock parameters fall into three classes based on either grain, surface area, or pore dimension considerations. (Models that directly incorporate well log measurements but have no particular theoretical underpinnings form a fourth class.) Grain-based models show permeability proportional to the square of grain size times porosity raised to (roughly) the fifth power, with grain sorting as an additional parameter. Surface-area models show permeability proportional to the inverse square of pore surface area times porosity raised to (roughly) the fourth power; measures of surface area include irreducible water saturation and nuclear magnetic resonance. Pore-dimension models show permeability proportional to the square of a pore dimension times porosity raised to a power of (roughly) two and produce curves of constant pore size that transgress the linear data trends on a log(k)-0 plot. The pore dimension is obtained from mercury injection measurements and is interpreted as the pore opening size of some interconnected fraction of the pore system. The linear log(k)-0 data trends cut the curves of constant pore size from the pore-dimension models, which shows that porosity reduction is always accompanied by a reduction in characteristic pore size. The high powers of porosity of the grain-based and surface-area models are required to compensate for the inclusion of the small end of the pore size spectrum.

329 citations



Patent
Hooman Laali1
19 Apr 1994
TL;DR: In this paper, a method for improving hydrocarbon flow from a consolidated, tight reservoir rock having authigenic clay cementation is proposed, which includes thermally heating the reservoir rock in-situ surrounding a production well to change the mode of occurrence of clay cements within the rock so as to enhance reservoir permeability and carry out rapid flowback into the production well.
Abstract: A method for improving hydrocarbon flow from a consolidated, tight reservoir rock having authigenic clay cementation includes thermally heating the reservoir rock in-situ surrounding a production well to change the mode of occurrence of clay cements within the rock so as to enhance reservoir permeability and carrying out rapid flowback into the production well.

268 citations


Book ChapterDOI
Aroon Shenoy1
TL;DR: In this paper, a review of the literature on non-Newtonian-fluid heat transfer in porous media is presented, with a focus on boundary layer and confined flows.
Abstract: Publisher Summary The chapter focuses on non-Newtonian-fluid heat transfer in porous media and reviews the existing literature, the number of citations in which has rapidly grown reaching a sizable number on the topic. The existing body of information covers most of the relevant Darcy and non-Darcy situations in boundary layer and confined flows. Heat transfer in porous media is of great pragmatic importance in a wide variety of scientific and engineering applications, as can be seen from some of the applications summarized in the chapter. The chapter presents pure Darcy natural-convection boundary-layer problem for flow past an isothermal vertical flat plate, a nonisothermal smooth surface of arbitrary shape, and a nonuniform horizontal flat plate embedded in a porous medium saturated with an Ostwald-de Waele power-law fluid. The problem of pure Darcy natural-convection boundary-layer flow past an isothermal vertical flat plate embedded in a porous medium saturated with a Herschel-Bulkley fluid—namely, a pseudoplastic fluid with yield stress is discussed. The problem of pure Darcy natural-convection boundary-layer flow past an isothermal vertical flat plate embedded in a porous medium saturated with an elastic Boger fluid with constant viscosity is discussed. The chapter presents pure Darcy mixed-convection boundary-layer problem for flow past an isothermal vertical flat plate and a nonisothermal smooth surface of arbitrary shape embedded in a porous medium saturated with an Ostwald-de Waele power-law fluid. The problem of pure Darcy mixed-convection boundary-layer flow past an isothermal vertical flat plate embedded in a porous medium saturated with an elastic Boger fluid with constant viscosity is presented. The chapter presents some more additional topics on steady-state convection. Nonsteady state convections based on pure Darcy regime are discussed.

165 citations


Journal ArticleDOI
TL;DR: In this paper, the authors modify the Carman-Kozeny equation to express the single-phase permeability of unconsolidated media in terms of both the psd statistics and the bulk physical properties.
Abstract: The single-phase permeability of a permeable medium is determined by both the bulk physical properties of the interconnected pore system (e.g., porosity and tortuosity) and the statistics of its particle-size distribution (psd). An expression of the relation between permeability and pore-level properties is the Carman-Kozeny (CK) equation. This equation has historically been used to explain the fundamental causes of permeability because it provides a link between media attributes and flow resistance. Because the CK equation has not been applied to media consisting of mixed particle sizes, we modify the CK equation to express the single-phase permeability of unconsolidated media in terms of both the psd statistics and the bulk physical properties. We find that we can relate permeability to the parameters of a psd for unconsolidated media. This relationship matches published data. It generally fails for permeabilities less than 1 µm2 (~1 darcy), probably because not all of the pore space is supporting flow in this region. With the model partially verified by experimental data, we use it to investigate the nature of permeability-porosity relationships and of the origin of variability in permeability. The latter capability will explain many of the permeability differences observed in outcrop studies.

156 citations


Journal ArticleDOI
TL;DR: In this paper, the authors examined the impact of hydraulic conductivity in a porous medium on solute transport, considering the similarities and differences between parallel flow and convergent/divergent flow.
Abstract: The variation of hydraulic conductivity in a porous medium causes the fluids flowing through it to have nonuniform velocities. Variation in fluid velocity is one of the main contributors to solute dispersion, causing a part of the contaminants dissolved in the fluid to be transported with greater than average velocities. In practical problems concerning transport of radioactive or toxic wastes, the velocity of contaminant flow may be of vital importance. This paper examines a three dimensional case, considering also the similarities and differences between parallel flow and convergent/divergent flow. Fluid flow in a porous medium is shown to perfer the most conductive paths. For a medium with strongly variable permeability this effect can be very pronounced. This paper discusses the impact of this flow distribution upon solute transport. 28 refs., 11 figs., 2 tabs.

139 citations


Journal Article
TL;DR: In this article, a large sample of compacted clay (diameter = 298 mm; thickness = 914 mm) was subjected to freeze-thaw in the field for 60 days.
Abstract: A large specimen of compacted clay (diameter = 298 mm; thickness = 914 mm) was subjected to freeze-thaw in the field for 60 days. Afterward, the hydraulic conductivity was measured. The hydraulic conductivity of the entire specimen remained essentially unchanged, but increases in hydraulic conductivity of 1.5-2 orders of magnitude were observed above the freezing plane. The increase in hydraulic conductivity was highest at the top of the specimen and decreased with depth. Changes in hydraulic conductivity also occurred at depths 150 mm below the freezing plane, where desiccation occurred because of water redistribution. Numerous horizontal and vertical cracks formed in the soil mass. Dissection of the sample after permeation revealed that the cracks were laden with water. Cracking was greatest at the surface and became less frequent with depth. For depths greater than 150 mm below the freezing plane, cracking was absent. The frequency of cracks is consistent with principles of mechanistic models of soil freezing. The results of laboratory tests were used to predict the hydraulic conductivity of the large specimen. Tests were conducted on specimens subjected to various freeze-thaw cycles, temperature gradients, and states of stress. It was found that the predicted hydraulic conductivities were lower thanmore » those measured on the large specimen, but they closely resembled the trend in hydraulic conductivity with depth.« less

130 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigate several flow models for sandstones, and examine their impact on the calculation of effective permeability for single phase flow, and indicate how the method of calculating tensor permeabilities may be extended to model multiphase flow in sedimentary structures, e.g., in crossbedded structures with a high bedding angle, high permeability contrast, and laminae of comparable thickness.
Abstract: Accurate modeling of fluid flow through sedimentary units is of great importance in assessing the performance of both hydrocarbon reservoirs and aquifers. Most sedimentary rocks display structure from the mm or cm scale upwards. Flow simulation should therefore begin with grid blocks of this size in order to calculate effective permeabilities for larger structures. In this paper, we investigate several flow models for sandstones, and examine their impact on the calculation of effective permeability for single phase flow. Crossflow arises in some structures, in which case it may be necessary to use a tensor representation of the effective permeability. We establish conditions under which tensors are required, e.g., in crossbedded structures with a high bedding angle, high permeability contrast, and laminae of comparable thickness. Cases where the off-diagonal terms can be neglected, such as in symmetrical systems, are also illustrated. We indicate how the method of calculating tensor permeabilities may be extended to model multiphase flow in sedimentary structures.




Journal ArticleDOI
TL;DR: In this paper, a three-dimensional simulation of flow in the Uinta basin was done to test the hypothesis that the high pore-fluid pressure is due to the generation of oil from kerogen in the Green River oil shale at depth.
Abstract: The Altamont oil field in the deep Uinta basin is known to have reservoir fluid pressures that approach lithostatic. One explanation for this high pore-fluid pressure is the generation of oil from kerogen in the Green River oil shale at depth. A three-dimensional simulation of flow in the basin was done to test this hypothesis. In the flow simulation, oil generation is included as a fluid source. The kinetics of oil generation from oil shale is a function of temperature. The temperature is controlled by (1) the depth of sediment burial and (2) the geothermal gradient. Using this conceptual model, the pressure buildup results from the trade-off between the rate of oil generation and the flow away from the source volume. The pressure increase depends primarily on (1) the rate of the oil-generation reaction and (2) the permeability of the reservoir rocks. A sensitivity analysis was performed in which both of these parameters were systematically varied. The reservoir permeability must be lower than most of the observed data for the pressure to build up to near lithostatic. The results of the simulations indicated that once oil generation was initiated, the pore pressure built up rapidly to near lithostatic. We simulated hydrofractures in that part of the system in which the pressures approach lithostatic by increasing both the horizontal and the vertical permeability by an order of magnitude. Because the simulated hydrofractures were produced by the high pore pressure, they were restricted to the Altamont field. A new flow system was established in the vicinity of the reservoir; the maximum pore pressure was limited by the least principal stress. Fluids moved vertically up and down and laterally outward away from the source of oil generation. The analysis indicated that, assuming that one is willing to accept the low values of permeability, oil generati n can account for the observed high pressures at Altamont field.

Journal ArticleDOI
TL;DR: In this article, a review of the Katz-Thompson theory and its assumptions is presented, and its applicability to cementitious materials is investigated using two sets of data of various hardened cement pastes and concretes.

Journal ArticleDOI
TL;DR: In this article, the influence of fly ash on concrete permeability was evaluated by using the Figg method and the results showed that the addition of a Class C fly ash caused a decrease in chloride permeability of concrete up to 50% cement replacement.

Journal ArticleDOI
TL;DR: In this article, a mathematical model of transport phenomena and chemical processes of the thermal degradation of cellulose is presented, where the kinetic model developed by Bradbury et al. (J. Appl. Polym. Sci.23, 3271, 1979) for primary pyrolysis is extended to include secondary reactions of volatiles.
Abstract: A mathematical model of transport phenomena and chemical processes of the thermal degradation of cellulose is presented. The kinetic model developed by Bradbury et al. (J. Appl. Polym. Sci.23, 3271, 1979) for primary pyrolysis is extended to include secondary reactions of volatiles: From the physical point of view, the model describes convective, conductive and radiative heat transfer, mass convection and diffusion and velocity and pressure variations interior to the porous solid (Darcy law). Furthermore, porosity, mass diffusivity, permeability and thermal conductivity vary with the composition of the reacting medium. Time and space evolution of the main variables, and reaction product distribution, are simulated by varying the reactor temperature and the reactor heating rate.



Patent
10 Mar 1994
TL;DR: In this paper, a method to rapidly determine the fluid-flow permeability of porous media with nuclear magnetic resonance (NMR) was proposed, which can be applied to measurements of permeability in fluid-saturated earth formations using NMR logging tools.
Abstract: The present invention is a method to rapidly determine the fluid-flow permeability of porous media with nuclear magnetic resonance (NMR). The method can be applied to measurements of permeability in fluid-saturated earth formations using NMR logging tools.

Journal ArticleDOI
M.S. Bruno1
TL;DR: In this paper, a discrete element model for cemented granular material is described which combines simple mechanisms of granular deformation, intergranular and intragranular microcracking, and pore channel fluid flow.

Journal ArticleDOI
TL;DR: In this paper, experimental data of soils in both the normally consolidated and overconsolidated states reveal that the proposed relationships are tenable and that preconsolidation stress level influences the level of permeability.
Abstract: Analysis of experimental data of soils in both the normally consolidated and overconsolidated states reveal that the proposed relationships are tenable. Preconsolidation stress level influences the level of permeability.

Journal ArticleDOI
TL;DR: In this paper, the transplane fjuid permeability of various fiber reinforcements was measured and analyzed using independent methods, including the measured injection pressure and flow rate, together with a one-dimensional Darcy's law, and a method was proposed to simplify the simulation of a 3D flow through the fiber perform.
Abstract: This work discusses tow independent methods to measure and analyze the trans-plane fjuid permeability of various fiber reinforcements. In the unidirectional flow method, the measured injection pressure and flow rate, together with a one-dimensional Darcy's law were used to calculate the trans-plane permeability of fiber mats was independent of flow rate only at low injection pressure. Flow-induced fiber mat permeability change occurred when the injection pressure exceeded the clamping pressure. Measured permeability in conjunction with a three-dimensional mold filling computer program was used to simulate the effect of stacking sequence for a combination of different fiber mats on the mold filling pattern. Finally, a method is proposed to simplify the simulation of a three-dimensional flow through the fiber perform.

Book ChapterDOI
01 Jan 1994

Journal ArticleDOI
TL;DR: In this article, the authors assess and develop experimental techniques that allow capillary pressure and per meability to be measured over a wide range of saturations, including near zero to 100.
Abstract: Once capillary pressure and permeability are determined for saturations ranging from near zero to 100%, liquid transport related to both wicking and wetting behavior can be described by Darcy's equation. The purpose of the work reported here is to assess and develop experimental techniques that allow capillary pressure and per meability to be measured over a wide range of saturations. Cotton and polypropylene fabrics are the test materials. Capillary pressure head is measured as a function of saturation for cotton and polypropylene fabric samples using the column test, and permeability is measured as a function of saturation using the siphon test. The siphon test works for cotton but not for polypropylene. A new method using a transient measurement technique is developed to determine the permeability of both samples as a function of saturation; it works well for both samples.


Journal ArticleDOI
R.A. Beier1
TL;DR: In this paper, a model for a heterogeneous reservoir with a fractal structure was developed for a well with a vertical fracture in an infinite reservoir and is an extension of a previous fractal model that handles a finite circular wellbore.
Abstract: Conventional pressure-transient models have been developed under the assumption that reservoirs are areally homogeneous. Yet, core, log, and outcrop data indicate this assumption is not justified in many cases. Still, homogeneous models are applied to obtain an effective permeability corresponding to a fictitious homogeneous reservoir. This approach seems reasonable if the correlation length of the permeability variation is small compared with the interwell scale and the permeability variation is sufficiently small. Mishra et al. formed a heterogeneity index that contained the spatial correlation and the variation. One would suspect the homogeneous model might eventually fail as the permeability variation and correlation-length scale increase. The field data given below confirm that homogeneous models do not always apply. Instead, a model developed for a heterogeneous reservoir with a fractal structure matches the field tests. The model considers a reservoir that contains permeable and impermeable rock. The resulting permeable network is assumed to have a fractal structure, which imposes heterogeneities at all length scales. The permeability distribution is bimodal because, at any location, the permeability is either zero or a fixed finite value. The model treats a well with a vertical fracture in an infinite reservoir and is an extension of a previousmore » fractal model that handles a finite circular wellbore. Chang and Yortsos have previously applied a fractal model to naturally fractured reservoirs.« less

Journal ArticleDOI
TL;DR: In this article, a lattice gas automaton (LGA) model is proposed to simulate fluid flow in heterogeneous porous media, where the loss in momentum of the fluid is directly related to the permeability of the LGA model.
Abstract: A lattice gas automaton (LGA) model is proposed to simulate fluid flow in heterogeneous porous media. Permeability fields are created by distributing scatterers (solids, grains) within the fluid flow field. These scatterers act as obstacles to flow. The loss in momentum of the fluid is directly related to the permeability of the lattice gas model. It is shown that by varying the probability of occurrence of solid nodes, the permeability of the porous medium can be changed over several orders of magnitude.

Journal ArticleDOI
TL;DR: In this paper, a variably saturated flow model was used to investigate the effects of independent variations in the saturated hydraulic conductivity and the two Van Genuchten parameters, and the relationship between these descriptive soil parameters, which may be used to describe the pore-size-density function of a porous medium, was surmised based upon limited empirical evidence.