Changes In Pore Space Research Articles

Thermal Conductivity Variations in Frozen Hydrate-Bearing Sand upon Heating and Dissociation of Pore Gas Hydrate

High-latitude permafrost, including hydrate-bearing frozen ground, changes its properties in response to natural climate change and to impacts from petroleum production. Of special interest is the behavior of thermal conductivity, one of the key parameters that control the thermal processes in permafrost containing gas hydrate accumulations. Thermal conductivity variations under pressure and temperature changes were studied in the laboratory through physical modeling using sand sampled from gas-bearing permafrost of the Yamal Peninsula (northern West Siberia, Russia). When gas pressure drops to below equilibrium at a constant negative temperature (about −6 °C), the thermal conductivity of the samples first becomes a few percent to 10% lower as a result of cracking and then increases as pore gas hydrate dissociates and converts to water and then to ice. The range of thermal conductivity variations has several controls: pore gas pressure, hydrate saturation, rate of hydrate dissociation, and amount of additionally formed pore ice. In general, hydrate dissociation can cause up to 20% thermal conductivity decrease in frozen hydrate-bearing sand. As the samples are heated to positive temperatures, their thermal conductivity decreases by a magnitude depending on residual contents of pore gas hydrate and ice: the decrease reaches ~30% at 20–40% hydrate saturation. The thermal conductivity decrease in hydrate-free saline frozen sand is proportional to the salinity and can become ~40% lower at a salinity of 0.14%. The behavior of thermal conductivity in frozen hydrate-bearing sediments under a pressure drop below the equilibrium and a temperature increase to above 0 °C is explained in a model of pore space changes based on the experimental results.

EOR Displacement Characteristics from Cluster Analysis and Fractional Pore Occupation

AbstractThe in situ saponification of crude oil lowers the interfacial tensions of oil–water systems in chemical-enhanced oil recovery (cEOR). When the interfacial tension is sufficiently low, emulsion phases occur, and the fluid phase distribution in the pore space changes, affecting oil displacement efficiency. This change in capillarity allows the injection water to penetrate different classes of pores, which must be reflected in the distribution of fluids in the pore space. This issue still needs to be adequately researched and is not reflected in the classic analyses of oil cluster size. We have performed μCT-based coreflood experiments to study the displacement efficiency of crude oil by alkaline solutions acting as cEOR agents for in situ saponification. The measured fluid distributions were analyzed using oil-cluster size statistics. In addition, the pore classes from which the oil was preferentially displaced and the degree of displacement as a function of alkali concentration were determined. Despite ultralow interfacial tension and emulsion formation, a clear separation of the oil and aqueous phases was observed over a wide range of alkali concentrations, allowing a two-phase analysis of the microscopic fluid distribution. It was found that (a) a Lorentz analysis of the cluster volume distribution is useful to characterize the cEOR displacement efficiency. It shows the tendency of oil clusters toward a more uniform size distribution toward optimal alkali concentration. (b) the additional oil recovery toward optimal displacement conditions comes from the fraction of smaller pores; at optimal conditions, all pore classes are flooded almost equally and to a high degree, equivalent to miscible displacement, i.e., extremely low interfacial tension.

Dynamic response and damage evolution of red sandstone with confining pressure under cyclic impact loading

AbstractAbundant mesoscale damage occurs prior to rock destruction, and the change in porosity can reflect the dynamic mechanical characteristics of the rock. In this study, red sandstone specimens were dynamically loaded by a split Hopkinson pressure bar (SHPB) with confining pressure. The change in porosity was reflected by the new index of porosity variation rate (Rv), and the relationships between the cyclic impact and the dynamic characteristics and porosity variation were analyzed. The average filtering algorithm was emphasized to remove the noise of grayscale NMR images. It was concluded that the number of impacts before crushing gradually decreases with increasing air pressure for the overall trend, there is no obvious rebound, and the energy dissipation increases before the crushing of the specimens. There is an abrupt difference in the dynamic characteristics between the third impact and the fourth impact. The pore space changes from medium and large pores to micropores with impact loading. The peak of the microporous porosity difference curve shifts to smaller micropores. The new index can describe pore closure and expansion. The image processing method used in this work obtained accurate statistical information that confirms the presence of a large number of microcracks before crushing.

Fine-Grained Sediment Characterization and Process Monitoring Using Nuclear Magnetic Resonance (NMR)

Abstract The intrinsic magnetic moment of hydrogen nuclei allows them to interact with externally imposed magnetic fields; then, nuclear magnetic resonance (NMR) can be used to probe the pore space of wet soils using the water molecules in pores. Surface relaxivity at pore walls combines with molecular diffusion to produce a relaxation rate that is inversely proportional to the pore size in saturated specimens or the mean distance to a pore wall in unsaturated soils. We used NMR to nondestructively characterize pore size distribution, monitor changes in pore space during sedimentation, and track the evolution of water conditions during drying and infiltration. Results show that the evolution of relaxation time distribution reflects pore size contraction, water film thickness reduction, and pore water redistribution. In all cases, the mean relaxation time and water content exhibit a unique relationship for both saturated and unsaturated soils; we propose a parallel plate model to interpret this relationship that only depends on surface relaxivity and specific surface area. Finally, we impose a magnetic field gradient to obtain spatially resolved relaxation spectra; this technique shows the evolution of moisture profile with depth and changes in moisture transport mechanisms during 1D drying. The carefully designed experiments demonstrate the potential of NMR spectroscopy as an effective tool to monitor water conditions and characterize the pore space in fine-grained sediments.

Interpreting Self-Potential Signal during Reactive Transport: Application to Calcite Dissolution and Precipitation

Geochemistry and reactive transport play a critical role in many fields. In particular, calcite dissolution and precipitation are chemical processes occurring ubiquitously in the Earth’s subsurface. Therefore, understanding and quantifying them are necessary for various applications (e.g., water resources, reservoirs, geo-engineering). These fundamental geochemical processes can be monitored using the self-potential (SP) method, which is sensitive to pore space changes, water mineralization, and mineral–solution interactions. However, there is a lack of physics-based models linking geochemical processes to the SP response. Thus, in this study, we develop the first geochemical–geophysical fully coupled multi-species numerical workflow to predict the SP electrochemical response. This workflow is based on reactive transport simulation and the computation of a new expression for the electro-diffusive coupling for multiple ionic species. We apply this workflow to calcite dissolution and precipitation experiments, performed for this study and focused on SP monitoring alternating with sample electrical conductivity (EC) measurements. We carried out this experimental part on a column packed with calcite grains, equipped for multichannel SP and EC monitoring and subjected to alternating dissolution or precipitation conditions. From this combined experimental investigation and numerical analysis, the SP method shows clear responses related to ionic concentration gradients, well reproduced with electro-diffusive simulation, and no measurable electrokinetic coupling. This novel coupled approach allows us to determine and predict the location of the reactive zone. The workflow developed for this study opens new perspectives for SP applications to characterize biogeochemical processes in reactive porous media.

Characteristics of Pore Structure in the Evaporated Stage of Wood-Derived Carbon

Major water loss in the first stage of wood-derived carbon preparation had a direct impact on pore structure during the subsequent pyrolysis of biochar materials. To explore the changes in pore space at this stage, poplar was used as the subject of this study. The pore morphology before and after water evaporation was quantitatively characterized by scanning electron microscope, nitrogen adsorption method, and mercury injection method. Both the fractal dimensions of the multistage pores were obtained by the Frenkel-Halsey-Hill model and the thermodynamic relationship model. The results showed as follows: the adsorption isotherms were presented the mixed type of II and IV after supercritical drying, indicating the mesopores and macropores of wood. The adsorption isotherms after conventional drying were characterized a type II, which was inferred to the reduced mesopores compared to supercritical drying. The hysteresis loops of all wood samples were examined for the H3 type, which was deduced from the presence of slit-like pores. After treatment at 103±2 °C, the porosity and its connectivity properties are reduced by the mercury pressure data. For <50 nm the pore size distribution of the samples shows a shoulder peak at around 6.5 nm. Simultaneously, the pore structure is significantly deformed and the pore size distribution produces smaller peaks at 3014 and 12510 nm. The pore fractal dimension increases in the <50 nm stage. The fractal dimension of pores decreases when the pore size is 50 nm~5 μm. Stability of the pore fractal dimension in the pore size >50 nm stage. This indicates that the conventional drying treatment made the micropore complexity increase, and leads to a reduced or invariable pore structure complexity for the >50 nm. The fractal analysis could assist in better analyzing the changes of pore structure and provide a new perspective for studying the pore structure in the carbonation stage.

Effect of voids in kaolin stabilised by ground granulated blast furnaces slag mixtures

Kaolin is known as problematic soil which has a low strength that needs to improve before construction. Chemical stabilization with cement is used widely to stabilize different clay types; however, using it comes with disadvantages associated with carbon dioxide emission and sustainability issues. As an alternative to cement, Ground Granulated Furnaces Blast Slag (GGBS) has been applied to stabilise kaolin. The increment in the strength is due to the formation of new products that fill the soil voids. The formation of those new products is verified using Field Emission Scanning Electron Microscopy (FESEM). However, the changes in pore space cannot be quantified using FESEM. Thus, this study uses Image J to calculate voids area detected by (FESEM) for different kaolin-GGBS mixtures with different content of GGBS cured for different curing period. The book-like structure for the raw kaolin have changed slightly when mixed with GGBS. This is due to the formation of hydrate gels as a result of the pozzolanic reaction. The results from image J indicates that the void decreases as the content of GGBS increases as well as the curing period.

Topology-based characterization of chemically-induced pore space changes using reduction of 3D digital images

We present an algorithm for the pore-scale simulation of the reactive transport in a 3D case. The algorithm is designed to facilitate the observation of pore space changes caused by chemical fluid-solid interaction. Additionally, the algorithm allows estimation of the main macroscopic properties evolution of the porous material, such as permeability, hydraulic tortuosity, and formation factor. Also, we develop an algorithm to compute the persistence diagrams for the independent cycles in the pore space, which quantitatively characterizes the changes in the pore space topology. Moreover, we speed up this algorithm by using the original digital image reduction approach. Applying the clustering technique to the persistence diagrams, we show that different matrix dissolution scenarios can be distinguished based on the persistence homology. These scenarios depend on the flow rate, reaction rate, and species concentration at the inlet. At the same time, the samples from the different clusters illustrate utterly different behavior of the cross-property (porosity-permeability) relations.This is extended version of our conference paper [1].

Effects of Clay Mineral Composition on the Dynamic Properties and Fabric of Artificial Marine Clay

Marine clays are easily affected by different mineral composition in cyclic load-based geological hazards. Therefore, based on analyzing the mineral composition of natural marine clay, it is the key to predict the dynamic properties of natural materials under cyclic loading by using quantitated artificial marine clay. In this study, the marine clay found in the South China Sea deltas was investigated. Based on the results of geological conditions and mineral composition analyses, raw non-clay minerals (such as quartz, albite) and clay minerals (such as Na-montmorillonite and kaolinite) were used to produce artificial marine clay, the dynamic properties of which were studied from the impact of mineral composition. Dynamic triaxial laboratory testing for artificial marine clay comprising various clay minerals was performed under identical test conditions. The artificial marine clay with high montmorillonite content exhibited slower development of strain, more sluggish growth in pore water pressure, more rounded hysteresis curves, greater stiffness, and more prolonged viscous energy growth than the clay with low montmorillonite content. In addition, the flocculated fabric of the artificial marine clay with high montmorillonite content demonstrated sufficient pore space changes, more uniform pore distribution, and larger specific surface area than the dispersed fabric of the clay with low montmorillonite content. The factors arising from the influence of montmorillonite may lead to microstructural and fabric changes, hinder the development of pore water, and increase intergranular contact stiffness as well as delay the cyclic strain amplitude at the breakpoint of viscous energy dissipation. In general, the results presented in this study confirm that clay minerals, especially montmorillonite, have significant influence on the dynamic properties of large strain.

RELATIONSHIP OF COMPLEX DIELECTRIC PERMEABILITY AND NMR CHARACTERISTICS OF DRILL CUTTINGS WITH ITS RESERVOIR PROPERTIES

The paper presents the results of experimental studies of the dielectric and NMR characteristics of drill cuttings. It is shown how the fluid distribution in the pore space changes at different stages of extraction and saturation. It is shown that it is possible to estimate the degree of saturation of samples by sequential interpretation the spectra of the dielectric and NMR characteristics.

Computational topology-based characterization of pore space changes due to chemical dissolution of rocks

In this paper, we present an algorithm for the numerical simulation of reactive transport at the pore scale to facilitate observation of pore space and rock matrix evolution. Moreover, simulation at the pore scale opens up the possibility of estimating changes in the transport properties of rocks, such as permeability and tortuosity. To quantitatively analyze pore space evolution, we developed a numerical algorithm that can be used to construct persistence diagrams of the connectivity components for pore space and the rock matrix, which characterize the topology evolution during rock matrix dissolution. Introducing the “bottle-neck” metric in the space of the persistence diagrams, we cluster the numerical experiments in terms of similarities in topology evolution. We demonstrate that the application of this metric to the persistence diagrams allowed us to distinguish topologically different dissolution scenarios, for instance, the formation of a dissolution front near the inlet, homogeneous dissolution of the matrix inside the core sample, and formation of wormholes. We illustrate that the differences in topology evolution lead to cross-correlations among the transport properties of rocks (porosity-permeability-tortuosity).

Assessment of pore space changes during drying and wetting cycles in hysteresis of soil water retention curve in Russia using X-ray computed tomography

Hysteresis of soil water retention curve (SWRC hysteresis) is a unique character of SWRC. It can be attributed to changes in distribution, form, geometry, and connectivity of pores, as well as entrapping air. X-ray computed tomography (X-CT) is widely used for estimating the number, volume, shape, size distribution, and structure of pores. The aim of the work was to monitor visually and quantitatively the pore space changes during the drying and wetting cycles using X-CT. Moreover, the dynamics of the occurrence of SWRC hysteresis was visually observed as a function of pore space structure changes using visual images of pore space. The hysteresis of SWRC was measured including drying and wetting curves using capilaremeter. Furthermore, the visual images of soil samples were implemented for the drying and wetting processes at different values of soil water potential. Also, the number, volume and the percentages of open, closed and total porosity were estimated using X-CT software during the drying and wetting processes. Moreover, the effective degree of saturation was calculated for the drying and wetting curves. The results observed that the visual images of pore space and the percentage of total porosity were increased during the drying process, whereas the pore space and the percentage of total porosity were decreased during the wetting process. However, the values of open, closed and total porosity for the wetting curve were usually larger than their values for the drying curve due to inadequate shrinkage and swelling processes. On the other hand, the effective degree of saturation was decreased during the drying process, but it was increased during the wetting process. The reason of the difference of soil moisture and an effective degree of saturation between drying and wetting curves is due to the difference of pore space structure for drying and wetting curves at the same soil water potential.

Characterisation of wellbore cement microstructure alteration under geologic carbon storage using X-ray computed micro-tomography: A framework for fast CT image registration and carbonate shell morphology quantification

An aqueous CO2–cement interaction experiment along with X-ray computed micro-tomography characterisation of pre- and post-exposure cement samples was carried out to investigate the cement structure evolution under geologic carbon storage conditions. An image processing framework was proposed for mapping mineral dissolution and precipitation and characterisation of carbonate shell morphology. The main workflow covered in this framework is to, 1) register cement CT images before and after reaction; 2) generate the difference image showing chemical alteration and map the difference image to demonstrate local content changes of pore space, calcite and portlandite; 3) segment carbonate shell from the difference image; 4) generate auxiliary images including skeleton, 3D local thickness and surface boundaries of the carbonate region, and 5) spatial quantification of the area, thickness, penetration depth and pore/calcite/portlandite content changes of the carbonate shell. The effectiveness of the framework was validated through step-by-step demonstration of results when deploying the framework to process the CT images of six cement samples acquired before and after reaction with CO2. The 3D mineral precipitation and dissolution (or local mineral content change) map and the internal and external carbonate shells were visualised. The spatial distribution of the shell area, thickness, penetration depth and pore/calcite/portlandite content changes along the height of the sample was revealed. Overall, the dissolution and precipitation map gives more intuitive and interpretable results of CO2-induced chemical alteration than direct visual comparison from the original CT images, and the morphological quantification of the carbonate shell gives reasonable interpretation of the spatial distribution of the carbonate reaction.

Physical and optical characteristics of heavily melted “rotten” Arctic sea ice

Abstract. Field investigations of the properties of heavily melted “rotten” Arctic sea ice were carried out on shorefast and drifting ice off the coast of Utqiaġvik (formerly Barrow), Alaska, during the melt season. While no formal criteria exist to qualify when ice becomes rotten, the objective of this study was to sample melting ice at the point at which its structural and optical properties are sufficiently advanced beyond the peak of the summer season. Baseline data on the physical (temperature, salinity, density, microstructure) and optical (light scattering) properties of shorefast ice were recorded in May and June 2015. In July of both 2015 and 2017, small boats were used to access drifting rotten ice within ∼32 km of Utqiaġvik. Measurements showed that pore space increased as ice temperature increased (−8 to 0 ∘C), ice salinity decreased (10 to 0 ppt), and bulk density decreased (0.9 to 0.6 g cm−3). Changes in pore space were characterized with thin-section microphotography and X-ray micro-computed tomography in the laboratory. These analyses yielded changes in average brine inclusion number density (which decreased from 32 to 0.01 mm−3), mean pore size (which increased from 80 µm to 3 mm), and total porosity (increased from 0 % to > 45 %) and structural anisotropy (variable, with values of generally less than 0.7). Additionally, light-scattering coefficients of the ice increased from approximately 0.06 to > 0.35 cm−1 as the ice melt progressed. Together, these findings indicate that the properties of Arctic sea ice at the end of melt season are significantly distinct from those of often-studied summertime ice. If such rotten ice were to become more prevalent in a warmer Arctic with longer melt seasons, this could have implications for the exchange of fluid and heat at the ocean surface.

Modeling granular soils liquefaction using coupled lattice Boltzmann method and discrete element method

In this paper, a novel coupled pore-scale model of pore-fluid interacting with discrete particles is presented for modeling liquefaction of saturated granular soil. A microscale idealization of the solid phase is achieved using the discrete element method (DEM) while the fluid phase is modeled at a pore-scale using the lattice Boltzmann method (LBM). The fluid forces applied on the particles are calculated based on the momentum exchange between the fluid and particles. The presented model is based on a first principles formulation in which pore-pressure develops due to actual changes in pore space as particles׳ rearrangement occurs during shaking. The proposed approach is used to model the response of a saturated soil deposit subjected to low and large amplitude seismic excitations. Results of conducted simulations show that at low amplitude shaking, the input motion propagates following the theory of wave propagation in elastic solids. The deposit response to the strong input motion indicates that liquefaction took place and it was due to reduction in void space during shaking that led to buildup in pore-fluid pressure. Soil liquefaction was associated with soil stiffness degradation and significant loss of interparticle contacts. Simulation results also indicate that the level of shaking-induced shear strains and associated volumetric strains play a major role in the onset of liquefaction and the rate of pore-pressure buildup.

Microtomographic Characterization of Dissolution-Induced Local Porosity Changes Including Fines Migration in Carbonate Rock

Summary The microstructure of carbonate rocks experiences substantial changes under reactive processes, in particular chemical dissolution and deposition, including dissolution-released-fines migration occurring during acidizing. A better understanding of such changes at the pore scale and their influences on rock properties is of great value for the effective design and implementation of reactive processes in carbonate reservoirs. In this work, we demonstrate the use of X-ray micro-computed tomography (micro-CT) to quantitatively investigate the local porosity changes in a meso-/microporous carbonate core sample during chemical dissolution. A reactive flooding experiment in a core sample by a nonacidic solution is designed such that changes in pore space from before to after the reactant injection could be imaged in exactly the same locations with micro-CT at a resolution of less than 5 μm. A methodology with three-phase segmentation and 2D histograms of image intensity is used to quantify distributions of the evolution of each image voxel. This technique allows the incorporation of microporosity into the calculation of the evolution regions, including the migration of fines, to accurately quantify the evolution scenarios. The micro-CT images reveal a quasiuniform dissolution pattern and allow characterizing the accompanying migration of fines within the core sample. The 3D pore networks are derived from the image data, which quantify changes in network structure and the pore geometry. The 2D histograms of image intensity derived from the pre- and post-dissolution images show quantitatively how macro- and micropores are enlarged by dissolution close to the inlet, whereas the deposition of fines mainly occurs in pores far from the inlet boundary. These results can explain why permeability of the sample initially decreases and then increases when injection time increases. Pore-surface area between each region is computed on the basis of the spatially resolved voxel evolution scenarios. This allows calculation of local distribution of reactive surface area, which, in turn, will assist in the prediction of local reaction rates in reactive flow simulators.

A novel architecture for pore network modelling with applications to permeability of porous media

Network models of porous media are beneficial for predicting the evolution of macroscopic mass transport properties. This work proposes a novel bi-regular network model based on truncated octahedral support. With the model, pore systems with different pore coordination spectra for a given average coordination number can be constructed to match experimental data. This feature and the maximum allowed pore coordination of 14 make the proposed model more realistic and flexible than the existing models based on cubic supports. Limestone is used as a study material to illustrate the model performance. Experimental pore space data for this material obtained by X-ray tomography (CT) are used for constructing microstructure-informed model realisations. It is demonstrated that with these realisations the experimentally measured permeability of the material can be predicted. The model is further used to assess the effects of pore connectivity and porosity on the permeability. It is shown that the effect of pore connectivity is substantially stronger than the effect of porosity. A strategy for calculating the evolution of permeability with damage-related pore space changes is also described. The results reveal the effects of the mechanical properties of the medium on the permeability evolution as a function of damage evolution. Developments of this strategy are suggested for deriving mechanism-based constitutive laws for engineering applications.

Mechanics of light weight proppants: A discrete approach

The computational and experimental assessment of light-weight proppants are undertaken to identify their effectiveness and efficiency to replace sand enlisted in hydraulic fracturing treatments in oil or gas well operations. A mixture of ground-nut-shells, aluminum or ceramic particles are shown to reduce the viscosity of the fracturing fluid while increasing its resistance to compression. Herein explicit dynamic finite element method is implemented to study quasi-static compression of a proppant pack where each granule (particle) is modeled individually. Various mixtures of hard and soft particles are investigated as a function of shape, size and inter-particle friction. The particle interactions clearly illustrate changes in pore space as a function of pressure, mixture composition and friction. The pressure vs displacement response of a proppant pack reflects strong dependence on mixture composition and initial particle configuration and has been compared with the test data. Friction leads to higher porosity by limiting particle rearrangement. Models reveal that softer rock with a mixture of hard and soft particles inhibit flowback but may decrease the pack permeability.

FRACTAL ANALYSIS OF SOIL PORE VARIABILITY WITH TWO DIMENSIONAL BINARY IMAGES

The manure which we are using for plant growth does not help to increase the porosity of the soil. We use pyroligneous acid to treat the soil as softener, nutrient and porosity increaser. This helps to the soil to remove unwanted carbonates and separate the soil particles. In this way, we can increase 30% porosity of the soil. When we pour pyroligneous acid into soil, the soil increase the carbon content. We consider changes of pore space of a soil by image analysis and also assess the applicability of fractal scaling of pore surfaces. The calculated pore surface dimension showing that the surface exhibit fractal structure. Lacunarity shows the size distribution of holes. If Lacunarity increases, then the value become decreases. This study demonstrates that applicability of fractal scaling for evaluating pore surface of the soil images.

Air entry–based characteristic length for estimation of permeability of variably compacted earth materials

The permeability k of a porous medium is a geometrical pore space attribute required for quantifying fluid flows and transport processes for hydrological, civil, agriculture, and petroleum engineering applications. Permeability is often expressed as proportional to a characteristic length squared and inversely proportional to factors accounting for porosity, pore shape, and tortuosity effects. Compaction and diagenesis reduce porosity, mean pore size, and connectivity, resulting in decrease in k. Permeability prediction relies on suitable selection of a characteristic length that may vary from simple hydraulic radius approximation of Kozeny‐Carman to more complex critical path analysis to identify flow‐limiting pore size. For porous media undergoing significant changes in pore space (e.g., compaction due to anthropogenic activities), the proper choice of a robust characteristic length is particularly challenging. We propose using the air entry pressure, a natural characteristic length that gauges the largest drainable pore size. This choice of a characteristic length is compatible with the Aissen formula that provides robust estimates of k for complex pore shapes. Additionally, the model considers geometrical (tortuosity) factors and links relative changes in porosity to concurrent changes in k. The model was tested against experimental data for sands, sandstones with different cementing agents, and unconsolidated soils. For unconsolidated sands and soils the model provides reasonable predictions of permeability for the entire range of porosities determined in laboratory or field experiments. However, for sandstones, and especially those containing cementing agents such as clay, the model is valid up to a critical porosity where hydraulic connectivity is lost, resulting in drastic reduction in k. The geometrical factor for soils was influenced by silt‐to‐clay ratio, while for sands, it was correlated with mean grain diameter. The model offers improvement in predicting k and provides a means for incorporating critical pore size and connectivity information in addition to porosity.