Showing papers on "Permeability (earth sciences) published in 2008"
TL;DR: In this article, the authors derived an analytical expression for the permeability in homogeneous porous media based on the fractal characters of porous media and capillary model, which is expressed as a function of fractal dimensions, porosity and maximum pore size.
577 citations
TL;DR: In this paper, a cubic relation between coal porosity and permeability is introduced to relate the coal storage capability (changing porosity) to the coal transport property (changing permeability).
404 citations
TL;DR: In this paper, the authors measured porosity, gas permeability, velocity and attenuation of ultrasonic wave propagation in the thermally-cracked rock of granite in order to assess, respectively, its transport properties and its mechanical strength.
368 citations
TL;DR: In this article, the authors conducted a program of measuring the relative permeability and other displacement characteristics of CO2-brine systems for sandstone, carbonate and shale formations in central Alberta in western Canada.
Abstract: Carbon dioxide capture and geological storage (CCGS) is an emerging technology that is increasingly being considered for reducing greenhouse gas emissions to the atmosphere. Deep saline aquifers provide a very large capacity for CO2 storage and, unlike hydrocarbon reservoirs and coal beds, are immediately accessible and are found in all sedimentary basins. Proper understanding of the displacement character of CO2-brine systems at in-situ conditions is essential in ascertaining CO2 injectivity, migration and trapping in the pore space as a residual gas or supercritical fluid, and in assessing the suitability and safety of prospective CO2 storage sites. Because of lack of published data, the authors conducted a program of measuring the relative permeability and other displacement characteristics of CO2-brine systems for sandstone, carbonate and shale formations in central Alberta in western Canada. The tested formations are representative of the in-situ characteristics of deep saline aquifers in compacted on-shore North American sedimentary basins. The results show that the capillary pressure, interfacial tension, relative permeability and other displacements characteristics of CO2-brine systems depend on the in-situ conditions of pressure, temperature and water salinity, and on the pore size distribution of the sedimentary rock. This paper presents a synthesis and interpretation of the results.
289 citations
01 Jan 2008
TL;DR: In this article, the authors described some of the technology-based solutions that have been used to successfully exploit these reservoirs, such as horizontal drilling, multi-stage completions, innovative fracturing, and fracture mapping.
Abstract: A significant portion of gas production in North America comes from unconventional reservoirs such as gas shales, coalbed methane (CBM) deposits and tight gas sands. Due to their limited permeability, stimulation processes are needed for economic recovery from wells drilled into these formations. This paper described some of the technology-based solutions that have been used to successfully exploit these reservoirs, such as horizontal drilling, multi-stage completions, innovative fracturing, and fracture mapping. Economic production depends on the matrix permeability of these reservoirs as well as the conductivity that can be generated in hydraulic fractures and network fracture systems. Simulations have shown that a fracture network of moderate conductivity is needed in ultra-low shale permeabilities. The spacing between fractures must be small to obtain reasonable recovery factors. Such networks are achievable according to results of microseismic mapping. In contrast, tight gas sands may be successfully depleted without inducing complex fracture networks because they have orders of magnitude greater permeability than gas shales. However, the recovery in tight gas sands is complicated by other issues of damage and zonal coverage in these reservoirs. It was concluded that fracture mapping can help improve the understanding of fractures and improve the ability to change the fracture complexity through operational changes to the well design and treatment implementation. 47 refs., 15 figs.
283 citations
TL;DR: In this article, the authors studied the pore fluid volume evolution of initially intact crystalline rocks (Cerro Cristales granodiorite and Westerly granite) under increasing differential load leading to macroscopic failure at water pore pressures of 50 MPa and varying effective pressures from 10 to 50 MPA.
Abstract: [1] Detailed experimental studies of the development of permeability of crustal rock during deformation are essential in helping to understand fault mechanics and constrain larger-scale models that predict bulk fluid flow within the crust. Permeability is particularly enhanced in the damage zone of faults, where microfracture damage accumulates under stress less than that required for macroscopic failure. Experiments performed in the prefailure region can provide data directly applicable to these zones of microfracture damage surrounding faults. The strength, permeability, and pore fluid volume evolution of initially intact crystalline rocks (Cerro Cristales granodiorite and Westerly granite) under increasing differential load leading to macroscopic failure has been determined at water pore pressures of 50 MPa and varying effective pressures from 10 to 50 MPa. Permeability is seen to increase by up to, and over, 2 orders of magnitude prior to macroscopic failure, with the greatest increase seen at lowest effective pressures. Postfailure permeability is shown to be over 3 orders of magnitude higher than initial intact permeabilities and approaches the lower limit of predicted in situ bulk crustal permeabilities. Increasing amplitude cyclic loading tests show permeability-stress hysteresis, with high permeabilities maintained as differential stress is reduced and the greatest permeability increases are seen between 90 and 99% of the failure stress. Prefailure permeabilities are nearly 7 to 9 orders of magnitude lower than that predicted by some high-pressure diffusive models suggesting that if these models are correct, microfracture matrix flow cannot dominate, and that bulk fluid flow must be dominated by larger-scale structures such as macrofractures. We present a model, based on our data, in which the permeability of a highly stressed fault tip process zone in low-permeability crystalline rocks increases by more than 2 orders of magnitude. Stress reduction related to the onward migration of the fault tip close damage zone cracks, while some permeability is maintained due to hysteresis from permanent microfracture damage.
223 citations
TL;DR: In this article, the authors performed experiments on mixtures of fine-grained quartz and kaolinite at 10 wt% intervals between the two end-member components (analogues for natural fault gouge) in order to establish their strength and fluid flow properties during hydrostatic and shear loading.
Abstract: [1] The strength and permeability of fault zones must be quantified in order to accurately predict crustal strength and subsurface fluid migration To this end, we performed experiments on mixtures of fine-grained quartz and kaolinite incremented at 10 wt% intervals between the two end-member components (analogues for natural fault gouge) in order to establish their strength and fluid flow properties during hydrostatic and shear loading Hydrostatically compacted samples exhibited permeability reduction on increasing effective pressures from 5 MPa to 50 MPa, with the rate of reduction displaying strong dependency on the synthetic fault gouge composition The permeability decreases continuously with increasing kaolinite content Porosity exhibits a distinct minimum that evolves with increasing effective pressure according to the relative compaction of the quartz and kaolinite end-members Porosity evolution with increasing clay content is predicted satisfactorily by a simple ideal packing model At the highest effective pressure (50 MPa), permeability reduced log-linearly over 4 orders of magnitude with increasing clay content Mechanically, sheared gouge samples showed a continuous reduction in frictional strength with increasing clay fraction Permeability decreased further on shear loading after initial hydrostatic compaction to 50 MPa This was most evident for the pure quartz end-member, with two orders of magnitude additional reduction, whereas the clay-rich samples were reduced only tenfold, mostly before a shear strain of 5 Variation of permeability with both clay content and shear deformation may be adequately described by previously published empirical predictors for fault zone permeability Clay content has the largest effect on permeability, and shear deformation affects permeability of quartz-rich gouges more than clay-rich gouges
209 citations
TL;DR: In this paper, a new model for coal permeability under variable stress conditions has been proposed, which is applicable to confinement pressure schemes commonly used during the collection of permeability data in the laboratory.
Abstract: This paper describes the derivation of a new equation that can be used to model the permeability behavior of a fractured, sorptive-elastic medium, such as coal, under variable stress conditions. The equation is applicable to confinement pressure schemes commonly used during the collection of permeability data in the laboratory. The model is derived for cubic geometry under biaxial or hydrostatic confining pressures. The model is designed to handle changes in permeability caused by adsorption and desorption of gases onto and from the matrix blocks in fractured media. The model equations can be used to calculate permeability changes caused by the production of methane (CH{sub 4}) from coal as well as the injection of gases, such as carbon dioxide, for sequestration in coal. Sensitivity analysis of the model found that each of the input variables can have a significant impact on the outcome of the permeability forecast as a function of changing pore pressure, thus, accurate input data are essential. The permeability model also can be used as a tool to determine input parameters for field simulations by curve fitting laboratory-generated permeability data. The new model is compared to two other widely used coal-permeability models using a hypothetical coal with averagemore » properties.« less
173 citations
Book•
22 Jul 2008TL;DR: In this paper, the concept of saturation was introduced, and the notion of mass conservation was used to quantify the amount of water that can be extracted from the ground water in a single phase.
Abstract: 1. Setting the Stage. 1.1 Introduction. 1.2 Phases and Porousmedia. 1.3 Grain and Pore Size Distributions. 1.4 The Concept of Saturation. 1.5 The Concept of Pressure. 1.6 Surface Tension Considerations. 1.7 Concept of Concentration. 1.8 Summary. 1.9 Exercises. 2. Mass Conservation Equations. 2.1 Introduction. 2.2 Microscalemass Conservation. 2.3 Integral Forms Ofmass Conservation. 2.4 Integral Theorems. 2.4.1 Divergence Theorem. 2.4.2 Transport Theorem. 2.5 Point Forms Ofmass Conservation. 2.6 Themacroscale Perspective. 2.6.1 The Representative Elementary Volume. 2.6.2 Global and Local Coordinate Systems. 2.6.3 Macroscopic Variables. 2.6.4 Definitions Of Macroscale Quantities. 2.6.5 Summary Of Macroscale Quantities. 2.7 The Averaging Theorems. 2.7.1 Spatial Averaging Theorem. 2.7.2 Temporal Averaging Theorem. 2.8 Macroscalemass Conservation. 2.8.1 Macroscale Point Forms. 2.8.2 Integral Forms. 2.9 Applications. 2.9.1 Integral Analysis. 2.9.2 Point Analysis. 2.10 Summary. 2.11 Exercises. 3. Flow Equations. 3.1 Introduction. 3.2 Darcy'S Experiments. 3.3 Fluid Properties. 3.4 Equations of State for Fluids. 3.4.1 Mass Fraction. 3.4.2 Mass Density and Pressure. 3.4.3 Fluid Viscosity. 3.5 Hydraulic Potential. 3.5.1 Hydrostatic Force and Hydraulic Head. 3.5.2 Derivatives of Hydraulic Head. 3.6 Single Phase Fluid Flow. 3.6.1 Darcy'S Law. 3.6.2 Hydraulic Conductivity and Permeability. 3.6.3 Derivation of Groundwater Flow Equation. 3.6.4 Recapitulation of the Derivation. 3.6.5 Initial and Boundary Conditions. 3.6.6 Two-Dimensional Flow. 3.7 Two-Phase Immiscible Flow. 3.7.1 Derivation of Flowequations. 3.7.2 Observations on the Pc - Sw Relationship. 3.7.3 Formulas for The Pc - Sw Relationship. 3.7.4 Observations of the Ka Rel - Sw Relationship. 3.7.5 Formulas for the Ka Rel - Sw Relation. 3.7.6 Special Cases of Multiphase Flow. 3.8 The Buckley-Leverett Analysis. 3.8.1 Fractional Flow. 3.8.2 Derivation of the Buckley-Leverett Equation. 3.8.3 Solution of the Buckley-Leverett Equation. 3.9 Summary. 3.10 Exercises. 4. Mass Transport Equations. 4.1 Introduction. 4.2 Velocity in the Species Transport Equations. 4.2.1 Direct Approach. 4.2.2 Rigorous Approach. 4.2.3 Distribution Approach. 4.2.4 Summary. 4.3 Closure Relations for the Dispersion Vector. 4.4 Chemical Reaction Rates. 4.5 Interphase Transfer Terms. 4.5.1 Kinetic Formulation. 4.5.2 Equilibriumformulation. 4.5.3 Summary: Kinetic Vs. Equilibrium Formulations. 4.6 Initial and Boundary Conditions. 4.7 Conclusion. 4.8 Exercises. 5. Simulation. 5.1 1-D Simulation of Air-Water Flow. 5.1.1 Drainage in a Homogeneous Soil. 5.1.2 Drainage in a Heterogeneous Soil. 5.1.3 Imbibition in Homogeneous Soil. 5.2 1-D Simulation of Dnapl-Water Flow. 5.2.1 Primary Dnapl Imbibition In Homogeneous Soil. 5.2.2 Density Effect. 5.2.3 Dnapl Drainage in Homogeneous Soil. 5.2.4 Secondary Imbibition of Dnapl in Homogeneous Soil. 5.2.5 Secondary Drainage in Homogeneous Soil. 5.2.6 Primary Imbibition in Heterogeneous Soil. 5.3 2-D Simulation of Dnapl-Water Flow. 5.3.1 Dnapl Descent into a Water-Saturated Reservoir. 5.4 Simulation Of Multiphase Flow And Transport. 5.4.1 1-D Two-Phase Flow and Transport. 5.4.2 2-D Two-Phase Flow and Transport. 5.5 2-D Single-Phase Flow and Transport. 5.5.1 Base-Case. 5.5.2 Effect of Inflow. 5.5.3 Impactofwell Discharge. 5.5.4 Effect of Adsorption. 5.5.5 Effect of a Low Transmissivity Region. 5.5.6 Effect of a High Transmissivity Region. 5.5.7 Effect of Rate of Reaction. 5.6 3-D Single-Phase Flow and Transport. 5.7 2-D Three-Phase Flow. 5.8 Summary. 6. Select Symbols.
166 citations
TL;DR: In this article, the influence of variability of coal permeability and strength on gas outbursts in underground coal mines has been investigated using Monte-Carlo techniques. But the authors did not consider the effect of coal gas reservoir variables such as gas composition, fluid pressure, desorption pressure and rate, porosity, intrinsic permeability, and relative permeability.
165 citations
TL;DR: In this article, the authors examined peat hydraulic conductivity profiles at three sites in north-western Canada, each representing a widely occurring organic-covered, permafrost terrain type.
Abstract: Subsurface flow through peat plays a critical role in the hydrology of organic-covered, permafrost terrains, which occupy a large part the continental arctic, sub-arctic, and boreal regions. Hillslope drainage in these terrains occurs predominantly through the active flow zone between the relatively impermeable frost table and the water table above it. The hydraulic conductivity profile within this zone controls the subsurface drainage of snowmelt and storm water. Peat hydraulic conductivity profiles were examined at three sites in north-western Canada, each representing a widely occurring organic-covered, permafrost terrain type. Three independent measures of saturated hydraulic conductivity were used—tracer tests, constant-head well-permeameter tests, and laboratory measurements of undisturbed samples. At all three sites, the conductivity profiles contained very high values (10–1000 m d−1) within the top ca 0·1 m where the peat is only lightly decomposed, a large reduction with increasing depth below the ground surface in the transition zone, and relatively low values in a narrow range (0·5–5 m d−1) below ca 0·2 m depth, where the peat is in an advanced state of decomposition. Digital image analysis of resin-impregnated peat samples showed that hydraulic conductivity is essentially controlled by pore hydraulic radius. The strong dependence of hydraulic conductivity on hydraulic radius implies that peat soils subjected to similar degrees of decomposition and compaction have a similar hydraulic conductivity regardless of the location. This explains the similarity of the depth-conductivity profiles among all three terrain types. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this paper, a two-scale model for fluid flow in a deforming, unsaturated and progressively fracturing porous medium is developed, where the local momentum and the mass balances are derived from the micromechanics of the flow in the cavity.
Abstract: A two-scale model is developed for fluid flow in a deforming, unsaturated and progressively fracturing porous medium. At the microscale, the flow in the cohesive crack is modelled using Darcy’s relation for fluid flow in a porous medium, taking into account changes in the permeability due to the progressive damage evolution inside the cohesive zone. From the micromechanics of the flow in the cavity, identities are derived that couple the local momentum and the mass balances to the governing equations for an unsaturated porous medium, which are assumed to hold on the macroscopic scale. The finite element equations are derived for this two-scale approach and integrated over time. By exploiting the partition-of-unity property of the finite element shape functions, the position and direction of the fractures are independent from the underlying discretization. The resulting discrete equations are nonlinear due to the cohesive crack model and the nonlinearity of the coupling terms. A consistent linearization is given for use within a Newton–Raphson iterative procedure. Finally, examples are given to show the versatility and the efficiency of the approach. The calculations indicate that the evolving cohesive cracks can have a significant influence on the fluid flow and vice versa.
TL;DR: In this paper, the authors evaluate how single-phase permeability varies as a function of sample support for ripple laminated sandstone intercalated with mudstone, and identify three flow upscaling regimes that each require a different method for up-scaling: (1) layered systems where the arithmetic and harmonic averages are appropriate, (2) systems close to the percolation threshold, (3) discontinuous systems where an effective medium method provides the best estimate of permeability.
Abstract: Using a range of realistic 3D numerical lithofacies (dm-scale) models of ripple laminated sandstone intercalated with mudstone we evaluate how single-phase permeability varies as a function of sample support. The models represent a range of mudstone content which is typical for tidal deposits. Furthermore, the spatial distribution of flow barriers (i.e. mudstone) is not random, but governed by sedimentological rules giving a variable anisotropy ratio as a function of mudstone content. Both vertical and horizontal permeability are found to vary at small sample volumes, but these fluctuations reduce as the sample volume increases. The vertical permeability increases while the horizontal permeability is nearly constant as a function of sample support for small mudstone contents. For higher mudstone content, the horizontal permeability decreases while the vertical permeability is nearly constant as a function of sample support. We propose a criterion, based on a normalised standard deviation, to determine the Representative Elementary Volume (REV). The size of the REV is dependent on both the property measured (vertical and horizontal permeability) and the correlation lengths of the lithological elements (i.e. lithofacies). Based on this we identify three flow upscaling regimes that each require a different method for upscaling: (1) layered systems where the arithmetic and harmonic averages are appropriate, (2) systems close to the percolation threshold where a percolation model should be used, and (3) discontinuous systems where an effective medium method provides the best estimate of permeability. The work gives, by using numerical experiments on a range of heterogeneous systems, a new insight in determination of the REV for permeability at the lithofacies scale and its relation to sedimentological parameters.
TL;DR: In this article, the results of computerized tomography (CT) monitored laboratory experiments to analyze permeability and porosity changes as well as to characterize relevant chemical reactions associated with injection and storage of CO2 in carbonate formations.
Abstract: Although there are a number of mathematical modeling studies for carbon dioxide (CO2) injection into aquifer formations, experimental studies are limited and most studies focus on injection into sandstone reservoirs as opposed to carbonate ones. This study presents the results of computerized tomography (CT) monitored laboratory experiments to analyze permeability and porosity changes as well as to characterize relevant chemical reactions associated with injection and storage of CO2 in carbonate formations. CT monitored experiments are designed to model fast near well bore flow and slow reservoir flows. Highly heterogeneous cores drilled from a carbonate aquifer formation located in South East Turkey were used during the experiments. Porosity changes along the core plugs and the corresponding permeability changes are reported for different CO2 injection rates and different salt concentrations of formation water. It was observed that either a permeability increase or a permeability reduction can be obtained. The trend of change in rock properties is very case dependent because it is related to distribution of pores, brine composition and thermodynamic conditions. As the salt concentration decreases, porosity and the permeability decreases are less pronounced. Calcite deposition is mainly influenced by orientation, with horizontal flow resulting in larger calcite deposition compared to vertical flow.
TL;DR: This paper presents a fast and accurate simulation method for the permeability of a textile reinforcement, based on a finite difference discretisation of the Stokes equations, for single layer, multi-layer and sheared models.
TL;DR: In this paper, the authors determined the relationship between permeability and other petrophysical properties in synthetic mudstones as a function of vertical effective stress and showed that smectite-rich clays compact significantly less and have lower bulk density, velocity, permeability, bulk and shear modulus but higher Poisson9s ratio compared to kaolinite-rich clay clays at the same effective stress.
Abstract: This study determines the relationship between permeability and other petrophysical properties in synthetic mudstones as a function of vertical effective stress. Six brine-saturated clay slurries consisting of smectite and kaolinite were compacted in the laboratory under both controlled pore pressure and proper drained conditions. Porosity, permeability, bulk density, velocity (both V p and V s ) and rock mechanical properties were measured constantly under increasing vertical effective stress up to 50 MPa. The results show that smectite-rich clays compact significantly less and have lower bulk density, velocity, permeability, bulk and shear modulus but higher Poisson9s ratio compared to kaolinite-rich clays at the same effective stress. Kaolinite aggregates compacted to about 26% porosity at 10 MPa effective stress corresponding to about 1 km burial depth in a normally compacted basin, whereas a pure smectite aggregate has a porosity of about 46% at the same stress. The permeability of kaolinite aggregates varies between 0.1 mD and 0.001 mD, while that of smectite aggregates varies from 0.004 mD to 0.00006 mD (60 nD) at stresses between 1 MPa and 50 MPa. Permeabilities in clays show a logarithmic decrease with increasing effective stress, bulk density, velocity or decreasing porosity. At the same porosity or bulk density, permeabilities differ up to five orders of magnitude within the smectite–kaolinite mixtures. Applications of the Kozeny–Carman equation for calculating permeability based on porosity in mudstones will therefore produce highly erroneous results. The relationships between V p , V s , bulk and shear modulus to permeability also vary by up to four orders of magnitude depending on the clay compositions. Velocities or rock mechanical properties will therefore not be suitable to estimate permeability in mudstones unless the mineralogy and textural relationships are known. These experimental results demonstrate that smectite content may be critical for building up pore pressure in mudstones compared to kaolinite. The results help to constrain compaction and fluid flow in mudstones in shallower parts of the basins (
TL;DR: In this paper, the authors compared the three-dimensional shape of the invasion front with the X-ray porosity maps obtained before injection to study the effect of the pore space geometry on the anisotropy of permeability.
Abstract: [1] The complete permeability tensor of 18 porous rock cores was determined by means of X-ray tomography monitoring during the displacement of a salty tracer. To study the effect of the pore space geometry on the anisotropy of permeability, we compared the three-dimensional shape of the invasion front with the X-ray porosity maps obtained before injection. The samples (clean and shale-bearing sandstones, limestones, and volcanic rocks) belong to a broad variety of granulometry and pore space geometry. Their porosity ranges from 12 to 57%, and their permeability ranges from 1.5 × 10−14 to 4 × 10−12 m2. For sandstones the permeability anisotropy is well correlated with the presence of bedding. For volcanic rocks it is clearly related to the orientation of vesicles or cracks. However, for limestones, no evident link between the geometry of the porous network and the permeability anisotropy appears, probably because of the influence of the nonconnected porosity that does not contribute to the hydraulic transport. This systematic work evidences the ability and the limitations of the tracer method to characterize the anisotropy of permeability in the laboratory in a simple and rapid way.
TL;DR: In this article, high-energy, synchrotron-based x-ray difference micro-tomography (XDMT) was combined with lattice Boltzmann simulations to assess changes in pore-scale flow patterns and bulk permeability resulting from colloid deposition in a granular porous medium.
Abstract: High-energy, synchrotron-based x-ray difference micro-tomography (XDMT) was combined with lattice Boltzmann simulations to assess changes in pore-scale flow patterns and bulk permeability resulting from colloid deposition in a granular porous medium. The detailed structural information obtained from XDMT was used to define internal boundary conditions for simulations of pore fluid flow both with and without colloidal deposits. As colloids accumulated in the pore space, the mean tortuosity increased and the tortuosity distribution became multi-modal, indicating the development of macro-scale heterogeneity. These structural changes also produced large reductions in bulk permeability that were not captured by empirical or semi-empirical estimators based on the first-order geometric properties of the porous medium. This work demonstrates that coupling between fluid flow and particle transport produces heterogeneities at the sub-millimeter scale that greatly affect the hydrogeologic properties of natural porous media.
TL;DR: In this paper, large scale experimental models of various natural clayey soils with various plasticity indices were subjected to cyclic drying and wetting and hydraulic conductivity testing to better understand cracking behaviour and self-healing in fine-grained soils.
TL;DR: In this article, a nonlinear evolution equation for the thickness of a thin Newtonian fluid layer on a porous inclined plane is obtained, assuming that the flow through the porous medium is governed by Darcy's law.
Abstract: The flow of a thin Newtonian fluid layer on a porous inclined plane is considered. Applying the long-wave theory, a nonlinear evolution equation for the thickness of the film is obtained. It is assumed that the flow through the porous medium is governed by Darcy’s law. The critical conditions for the onset of instability of a fluid layer flowing down an inclined porous wall, when the characteristic length scale of the pore space is much smaller than the depth of the fluid layer above, are obtained. The results of the linear stability analysis reveal that the film flow system on a porous inclined plane is more unstable than that on a rigid inclined plane and that increasing the permeability of the porous medium enhances the destabilizing effect. A weakly nonlinear stability analysis by the method of multiple scales shows that there is a range of wave numbers with a supercritical bifurcation, and a range of larger wave numbers with a subcritical bifurcation. Numerical solution of the evolution equation in a...
TL;DR: In this paper, the pore size distribution and porosity of sediment with different grain size distributions were measured using proton nuclear magnetic resonance (NMR) and mercury porosimetry.
Abstract: [1] This study used proton nuclear magnetic resonance (NMR) to measure pore size distribution of sediment in order to characterize methane hydrate-bearing sediment by pore size distribution and permeability. Sand sediment with different grain size distributions was measured as fundamental research and for application of natural methane hydrate-bearing sediment. Sediment pore size distribution and porosity were measured by NMR and mercury porosimetry. The absolute permeability of sediment measured by water flow based on the Darcy law was compared with the permeability calculated from NMR spectra based on the sediment delivery ratio equation. NMR spectra were also analyzed by a conversion technique in order to obtain pore size distribution with higher spatial resolution.
TL;DR: In this paper, the authors examined data from 23 studies to determine the range in permeabilities reported for sublittoral marine sands and assess the utility of permeability-grain size relationships in this setting.
Abstract: More than half of the surface sediments covering the continental shelves are sandy, which may permit substantial sub-seafloor pore water advection. Knowledge of sediment permeability is required for quantifying advection and associated solute transport, but studies of marine sediments typically report grain size analyses rather than permeability. Here data from 23 studies were examined to determine the range in permeabilities reported for sublittoral marine sands and to assess the utility of permeability– grain size relationships in this setting. In the resulting database, the permeability of small (w30 cm) undisturbed cores collected from the sea floor all fell between 2 � 10 � 12 and 4 � 10 � 10 m 2 , a range where advective transport induced by wave and current action should be pervasive. The range in grain size was very similar for near-shore ( 10 m water depth), but the permeability of the continental shelf samples was consistently lower for the same median grain size. Empirical permeability–grain size relationships generated a poor fit (r 2 ¼ 0.35) for the aggregate data, but separate relationships for near-shore and continental shelf samples were significantly better, r 2 ¼ 0.66 and 0.77, respectively. Permeability–grain size relationships thus may be useful for sublittoral sands, but a larger database needs to be accumulated before reliable fit parameters and variability can be predicted. Thus it is recommended that permeability be routinely determined when characterizing sedimentological properties of marine sand deposits. Concurrent determinations of sediment bulk density and porosity may further improve estimates of permeability. 2008 Published by Elsevier Ltd.
TL;DR: In this article, the authors explore the interactions between deformation, faulting, dilation, fluid flow and chemical processes, which are suggested to result in this control, with special attention to fault dilatant jog structures.
Abstract: Abstract Fault-related host rock deformation and dilation control fluid flow and mineralization in many world-class mineral deposits. This numerical modelling study explores the interactions between deformation, faulting, dilation, fluid flow and chemical processes, which are suggested to result in this control, with special attention to fault dilatant jog structures. Our two-dimensional numerical models focus on faulting-related deformation, dilation and permeability enhancement, fluid flow patterns and fluid focusing/mixing locations, while three-dimensional models examine several different cases of fault underlap and overlap. The results show that fault-dilation and faulting-induced permeability enhancement, which are closely associated with tensile failure, represent important ways to generate fluid flow conduits for more effective fluid flow and mixing. Dilation during strike–slip faulting is localized near fault tips (wing crack locations) and jog sites, where fluids are strongly focused and mixed. These locations are the tensile domains of the strike–slip regime. In overlapping-fault (dilatant jog) cases, the magnitude of dilation and the extent of the dilatant region are closely related to the extent of fault overlap. These results provide insight into the transport of fluids through low-permeability rocks with isolated, but more permeable, faults. Gold and quartz precipitation patterns as a result of the coupling of chemical reactions to deformation induced fluid flow velocities are also computed. The rates of precipitation depend on structural and fluid flow conditions and on the geometrical relation between local fluid velocity and chemical concentration gradients generated by mixing. Maximum precipitation rates for gold occur in the dilation zones and in faults where high fluid flow rates, sufficient fluid mixing and high concentration gradients of critical chemical species are all present, while the quartz precipitation rate is predominantly controlled, in this isothermal situation, by the rate of fluid flow across concentration gradients in the aqueous silica concentration.
TL;DR: The Hijiori hot dry rock (HDR) system, Japan, consists of a shallow and a deep reservoir, both in fractured granitic rocks during a long-term circulation test (LTCT) lasting approximately 18 months and which tested different fluid production scenarios as discussed by the authors.
TL;DR: In this paper, a pore morphology method was used to determine the distribution of gas and water phases in a gas diffusion layer, and the authors were able to determine permeability, diffusivity and heat conductivity as a function of the saturation of the porous medium with comparatively low numerical costs.
Abstract: In this paper, we give a complete description of the process of determining two-phase material parameters for a gas diffusion layer: Starting from a 3D tomography image of the gas diffusion layer the distribution of gas and water phases is determined using the pore morphology method. Using these 3D phase distributions, we are able to determine permeability, diffusivity, and heat conductivity as a function of the saturation of the porous medium with comparatively low numerical costs. Using a reduced model for the compression of the gas diffusion layer, the influence of the compression on the parameter values is studied.
TL;DR: In this article, the authors analyzed a data set of thermally induced changes in fractured rock permeability during a 4-year heating (up to 200 °C) and subsequent 4 year cooling of a large volume, partially saturated and highly fractured volcanic tuff at the Yucca Mountain Drift Scale Test, Nevada, USA.
TL;DR: Results indicate that improvement in water quality associated with source removal diminish with distance downgradient of the source, and pollutant degradation and contaminant adsorption in the stagnant zone are shown to be critical factors governing the timing and magnitude of downgradient improvements in waterquality.
TL;DR: In this paper, a mathematical model based on Fick's law for predicting O2, CO2, N2, and water vapor exchanges in modified atmosphere packaging (MAP) films with macroperforations was developed.
TL;DR: In this article, a two-dimensional double diffusion, natural convection in a rectangular enclosure filled with binary fluid saturating porous media is investigated numerically, where multiple motions are driven by the external temperature and concentration differences imposed across horizontal walls with the simultaneous presence of discrete heat and contaminant sources.
TL;DR: In this paper, a core displacement experiment, simulated oil, formation water, injected water, and distillated water were used as fluids to measure and analyze the threshold pressure gradient (TPG) for both a single and two-phase fluid flow.
Abstract: In a core displacement experiment, simulated oil, formation water, injected water, and distillated water were used as fluids to measure and analyze the threshold pressure gradient (TPG) for both a single- and two-phase fluid flow. A certain Chinese oil field core sample was used, which represents a typical ultra-low permeability reservoir: “block 119.” The study indicates that different types of fluids give a different TPG versus permeability power function, with index equal to approximately −1. The study also indicates that, due to the capillary pressure and the Jamin effect, the TPG for the two-phase oil and water is greater than that for the single-phase flow. By combining laboratory and field data, the effect of the TPG in the development of the ultra-low permeability reservoirs can be explained.