Influence Of Pore Geometry Research Articles

Influence of Pore Geometry on Sandstone Pore Analysis Based on a Digital Core

A digital core obtained without damage and contact can provide intuitive and quantitative analysis data for sandstone pore structure analysis. However, pore analysis results based on digital cores are quite different from experimental results due to limitations of scanning resolution, quality, pore extraction method, and experimental errors. In this research, the influence of pore geometry on pore analysis is studied from pore angles and pore resolution. First, sharp angles are extracted by image processing, and the influence of angles on pore radius distribution is analyzed. Then, by up–down sampling, high- and low-resolution digital cores are reconstructed, and the effects of resolution on pore connectivity and throat structure are discussed.

Influence of pore geometry on the state of bulk pore water in the pressure-temperature phase space

Influence of pore geometry on the state of bulk pore water in the pressure-temperature phase space

Structural and thermodynamic properties of inhomogeneous fluids in rectangular corrugated nano-pores

Based on the free-energy average method, an area-weighted effective potential is derived for rectangular corrugated nano-pore. With the obtained potential, classical density functional theory is employed to investigate the structural and thermodynamic properties of confined Lennard–Jones fluid in rectangular corrugated slit pores. Firstly, influence of pore geometry on the adsorptive potential is calculated and analyzed. Further, thermodynamic properties including excess adsorption, solvation force, surface free energy and thermodynamic response functions are systematically investigated. It is found that pore geometry can largely modulate the structure of the confined fluids, which in turn influences other thermodynamic properties. In addition, the results show that different geometric elements have different influences on the confined fluids. The work provides an effective route to investigate the effect of roughness on confined fluids. It is expected to shed light on further understanding about interfacial phenomena near rough walls, and then provide useful clues for the design and characterization of novel materials.

Effective medium theory and multiple linear regression‐based velocity estimation in syn‐rift clastic sequence of the Krishna–Godavari basin, India

ABSTRACTAn inclusion model, based on the Kuster–Toksöz effective medium theory along with Gassmann theory, is tested to forward model velocities for fluid‐saturated rocks. A simulated annealing algorithm, along with the inclusion model, effectively inverts measured compressional velocity (VP) to achieve an effective pore aspect ratio at each depth in a depth variant manner, continuously along with depth. Early Cretaceous syn‐rift clastic sediments at two different depth intervals from two wells [well A (2160–2274 m) and well B (5222–5303 m)], in the Krishna–Godavari basin, India, are used for this study. Shear velocity (VS) estimated using modelled pore aspect ratio offers a high correlation coefficient (>0.95 for both the wells) with measured data. The modelled pore aspect ratio distribution suggests the decrease in pore aspect ratio for the deeper interval, mainly due to increased effective vertical stress. The pore aspect ratio analysis in relation to total porosity and volume of clay reveals that the clay volume has insignificant influence in shaping the pore geometry in the studied intervals. An approach based on multiple linear regression method effectively predicts velocity as a linear function of total porosity, the volume of clay and the modelled pore‐space aspect ratio of the rock. We achieved a significant match between measured and predicted velocities. The correlation coefficients between measured and modelled velocities are considerably high (approximately 0.85 and 0.8, for VP and VS, respectively). This process indicates the possible influence of pore geometry along with total porosity and volume of clay on velocity.

Description of chalk microporosity via automated mathematical morphology on scanning electron microphotographs

The spatial geometry of microporosity influences fluid flow through chalk reservoirs and aquifers, and, hence, numerous geological processes. Analysing porosity is thus often critical in geological studies. Techniques such as mercury injection capillary pressure (MICP), nuclear magnetic resonance (NMR) and X-ray computed tomography (CT) are expensive, and hence often inapplicable to many geological studies, which often necessitate the analysis of large numbers (hundreds) of samples. However, scanning electron microscopes (SEM) have become widely available, and SEM imagery analysis, therefore, is cheaper and faster. However, extracting meaningful porosity descriptors from SEM images can be difficult, in part because of the difficulty in digitally separating pores in laterally continuous pore networks. Moreover, mathematical morphology can be automated to collect porosity parameters from hundreds of images in a short time frame. The technique also quantifies the shape complexity of porosity. Considering the influence of pore geometry on fluid flow, the capacity of image analysis to deconstruct the pore network by pore shapes is crucial when building flow models. This study concludes that mathematical morphology constitutes an alternative to other techniques in geological studies of microporosity. Lithologies dominated by micro- and nanoporosity, such as shales and tight sandstones, could also benefit from this technique.

Combination of techniques to quantify the distribution of bacteria in their soil microhabitats at different spatial scales

To address a number of issues of great societal concern at the moment, like the sequestration of carbon, information is direly needed about interactions between soil architecture and microbial dynamics. Unfortunately, soils are extremely complex, heterogeneous systems comprising highly variable and dynamic micro-habitats that have significant impacts on the growth and activity of inhabiting microbiota. Data remain scarce on the influence of soil physical parameters characterizing the pore space on the distribution and diversity of bacteria. In this context, the objective of the research described in this article was to develop a method where X-ray microtomography, to characterize the soil architecture, is combined with fluorescence microscopy to visualize and quantify bacterial distributions in resin-impregnated soil sections. The influence of pore geometry (at a resolution of 13.4 μm) on the distribution of Pseudomonas fluorescens was analysed at macro- (5.2 mm × 5.2 mm), meso- (1 mm × 1 mm) and microscales (0.2 mm × 0.2 mm) based on an experimental setup simulating different soil architectures. The cell density of P. fluorescens was 5.59 x 107(SE 2.6 x 106) cells g−1 soil in 1–2 mm and 5.84 x 107(SE 2.4 x 106) cells g−1 in 2–4 mm size aggregates soil. Solid-pore interfaces influenced bacterial distribution at micro- and macroscale, whereas the effect of soil porosity on bacterial distribution varied according to three observation scales in different soil architectures. The influence of soil porosity on the distribution of bacteria in different soil architectures was observed mainly at the macroscale, relative to micro- and mesoscales. Experimental data suggest that the effect of pore geometry on the distribution of bacteria varied with the spatial scale, thus highlighting the need to consider an “appropriate spatial scale” to understand the factors that regulate the distribution of microbial communities in soils. The results obtained to date also indicate that the proposed method is a significant step towards a full mechanistic understanding of microbial dynamics in structured soils.

Molecular Modelling for Reactor Design.

Chemical reactor modelling based on insights and data on a molecular level has become reality over the last few years. Multiscale models describing elementary reaction steps and full microkinetic schemes, pore structures, multicomponent adsorption and diffusion inside pores, and entire reactors have been presented. Quantum mechanical (QM) approaches, molecular simulations (Monte Carlo and molecular dynamics), and continuum equations have been employed for this purpose. Some recent developments in these approaches are presented, in particular time-dependent QM methods, calculation of van der Waals forces, new approaches for force field generation, automatic setup of reaction schemes, and pore modelling. Multiscale simulations are discussed. Applications of these approaches to heterogeneous catalysis are demonstrated for examples that have found growing interest over the last few years, such as metal-support interactions, influence of pore geometry on reactions, noncovalent bonding, reaction dynamics, dynamic changes in catalyst nanoparticle structure, electrocatalysis, solvent effects in catalysis, and multiscale modelling.

Variation of polymer-template pore geometry as a means of controlling the magnetic properties of metallic nanostructures

The influence of pore geometry of polyethylene terephthalate track-etched membranes on the structural, conducting, and magnetic characteristics of cobalt nanotubes (NTs) synthesized by electrochemical deposition has been studied. It has been found that there are significant differences in average size of crystallites and texture coefficients between various forms of cobalt nanotubes. Thus, the α-Co hexagonal closepacked phase dominates in Co-NT samples with cylindrical and hourglass pore shapes and the β-Co facecentered cubic phase prevails in conical Co nanotubes. Measurements of the magnetic properties have shown that the coercivity of cylindrical Co nanotubes is almost two times that of the conical forms because of crystal anisotropy of nanotube-forming cobalt crystallites.

The influence of pore geometry and orientation on the strength and stiffness of porous rock

The geometry of voids in porous rock falls between two end-members: very low aspect ratio (the ratio of the minor to the major axis) microcracks and perfectly spherical pores with an aspect ratio of unity. Although the effect of these end-member geometries on the mechanical behaviour of porous rock has received considerable attention, our understanding of the influence of voids with an intermediate aspect ratio is much less robust. Here we perform two-dimensional numerical simulations (Rock Failure Process Analysis, RFPA2D) to better understand the influence of pore aspect ratio (from 0.2 to 1.0) and the angle between the pore major axis and the applied stress (from 0 to 90°) on the mechanical behaviour of porous rock under uniaxial compression. Our numerical simulations show that, for a fixed aspect ratio (0.5) the uniaxial compressive strength and Young's modulus of porous rock can be reduced by a factor of ∼2.4 and ∼1.3, respectively, as the angle between the major axis of the elliptical pores and the applied stress is rotated from 0 to 90°. The influence of pore aspect ratio on strength and Young's modulus depends on the pore angle. At low angles (∼0–10°) an increase in aspect ratio reduces the strength and Young's modulus. At higher angles (∼40–90°), however, strength and Young's modulus increase as aspect ratio is increased. At intermediate angles (∼20–30°), strength and Young's modulus first increase and then decrease as pore aspect ratio approaches unity. These simulations also highlight that the influence of pore angle on compressive strength and Young's modulus decreases as the pore aspect ratio approaches unity. We find that the analytical solution for the stress concentration around a single elliptical pore, and its contribution to elasticity, are in excellent qualitative agreement with our numerical simulations. The results of our numerical modelling are also in agreement with recent experimental data for porous basalt, but fail to capture the strength anisotropy observed in experiments on sandstone. We conclude that the alignment of grains or platy minerals such as clays exerts a greater influence on strength anisotropy in porous sandstones than pore geometry. Finally, we show that the strength anisotropy that arises as a result of preferentially aligned elliptical pores is of a similar magnitude to that generated by bedding in porous sandstones and foliation in low-porosity metamorphic rocks. The modelling presented herein shows that porous rocks containing elliptical pores can display a strength and stiffness anisotropy, with implications for the preservation and destruction of porosity and permeability, as well as the distribution of stress and strain within the Earth's crust.

The differential Kuster–Toksöz rock physics model for predicting S-wave velocity

The Kuster–Toksoz (KT) model is a classical rock physics model concerning the influence of pore geometry on elastic wave velocities. However, this model is limited to a dilute concentration of pores, which means the porosity cannot be too high. In order to overcome this limitation, this paper transforms the KT model into a new differential Kuster–Toksoz (DKT) model. In other words, we propose a process in which porosity with certain geometries increases step by step from zero up to its final value. The simulation of the new model notably shows that it is superior to the classical KT model and the differential effective medium model since it takes multiple–porosity and higher porosity rocks into consideration. Furthermore, by combining the DKT model, the Gassmann equation and the Voigt–Reuss–Hill average equation, a S-wave velocity prediction procedure is proposed under the constraint of the P-wave velocity which is from the logging data. The new method is applied to both the measured data in laboratory and well data in logging. The results show that the predicted S-wave velocities match well with the measured ones, especially for data with high porosity. By comparing estimated S-wave velocity deduced from the new method and the KT model, the results demonstrate that the new method is effective for S-wave velocity prediction.

The Influence of Pore Geometry on the Viscous Instability in Surfactant-polymer Flooding in Heavy Oil Reservoirs

This study examines the effect of pore geometry on the viscous instability in surfactant-polymer flooding in an initially preferential water-wet porous medium filled with heavy oil and brine. Two approaches are used to characterize the effect of viscous instability. In both approaches, the dynamic mean pore-scale capillary number is considered as the foremost criterion to characterize the effect of viscous instability. In the first approach, which is a pore network approach, the effect of viscous instability on is neglected. In the second approach, the viscous instability effect is included by using the viscous instability theory to determine . The comparison between from the port network approach and viscous instability theory is used to show the effect of viscous instability. The change in was found to be an appropriate tool to characterize the effect of viscous instability in surfactant-polymer flooding.

Influence of pore geometry, pressure and partial water saturation to electrical properties of reservoir rock: Measurement and model development

Pressure and saturation are of two important parameters to be considered to evaluate the electrical properties of reservoir rock. As confining pressure can cause pore space of rock to collapse as well as rock properties to change, it for some reason is necessary to examine the degree of the pressure and saturation changes in affecting the electrical properties in detail. This work mainly focuses on the investigations of electrical properties of sandstones and carbonates. The effects of pore geometries, confining pressure, and partial water saturation on electrical properties are investigated. The new electrical dispersion models from 0.01 Hz until 0.2 MHz for shaly sandstone are also developed. Petrographic image analysis is carried out to asses pore geometry of media. Circularity, gamma, pore aspect ratio, pore size distribution and pore angle distribution are calculated to evaluate their effect on electrical dispersion. An observation on confining pressure and water saturation is then evaluated to obtain their impact on pore structure and complex resistivity. The result of this work, indicated by electrical resistivity dispersion in low water saturation, shows that surface conductivity plays as a dominant factor particularly in shaly media. In evaluating the surface conductivity, it is necessary to consider the pore geometry in that a large structure is easier to saturate rather than a small one. The high water salinity moreover can significantly reduce diffusive layer thickness and if the pore radii are very small, the diffusive layer thickness will touch each other and block an anion movement. The results further show that pore radius distribution provides more contribution to the electrical resistivity dispersion and becomes a basis to extract porosity from resistivity. The confining pressure only contributes small changes in pore geometry of media and the use of imaginary resistivity offers a better detection on it. Modified d-model and Archie's model are developed to calculate the dielectric permittivity and effective conductivity in high water salinity of saturated-rock as a function of water saturation degree.

On the influence of pore geometry and acidity on the activity of parent and modified zeolites in the synthesis of methylenedianiline

Methylenedianiline synthesis from formaldehyde and aniline is catalyzed by solid acid catalysts, such as zeolites, which offer strong acidity and high acid site density. Critical parameters for catalyst activity were explored using materials with MFI, BEA, MOR and FAU structure. While materials with MOR and MFI structure hardly show activity, BEA and FAU type zeolites are active and selective. The higher activity for the latter materials is related to their larger pore structure. Nevertheless, the reaction is limited by pore diffusion over parent BEA- and FAU-type zeolites. Mesoporous materials, such as dealuminated FAU, offer significantly higher activity as pore diffusion limitation can be overcome. Therefore, we synthesized and tested other mesoporous aluminosilicates such as desilicated BEA and the delaminated MWW materials ITQ-2 and MCM-36. It was shown that desilication increases the activity of parent BEA type zeolites for MDA formation, yet not to the same extend as dealumination in case of FAU. ITQ-2 shows promising results, but MCM-36 surpasses ITQ-2 in terms of activity by a factor of two displaying activities similar to the dealuminated FAU materials.

Pore geometry influence on the deactivation behavior of Ni-based catalysts for simultaneous production of hydrogen and nanocarbon

Pore geometry of Ni-containing Mg–Al–O mixed oxide catalysts could be controlled by varying the Ni content in the synthesis. Low Ni content may lead to the catalysts having mesopores with shape cylinder and narrow pore size distribution; high Ni content results in the catalyst having pores with shape ink-bottle and a wide pore size distribution. In methane decomposition to produce hydrogen and nanocarbon, the 50 wt.% Ni/Mg–Al–O catalyst was rapidly deactivated after 2 h of reaction; however, the catalysts with 15 and 25 wt.% of Ni showed much longer lifetime, which can be explained by assuming a new modal related to pore geometry of the catalysts.

Multiscale analysis of the coupled effects governing the movement of interstitial fluid in cortical bone

A multiscale approach (periodic homogenization) is carried out to model osteon's behaviour, and especially the coupled phenomena that govern its interstitial fluid movement. Actions of electro-osmotic and osmotic motions in addition to the classical Poiseuille flow are studied at the mesoscale of the canaliculus and within the micropores of the collagen-apatite matrix. Use of this fully coupled modelling leads to a comparison of these different effects. Limitation of a classical Darcian description of the fluid flow at the two scales is so studied. For each of these studies a special attention is given to the pore's geometry influence and to their electrical and hydraulic properties.

Predicting soil–water characteristic curves of compacted plastic soils from measured pore-size distributions

The unsaturated hydraulic conductivity function, k, is often predicted from the soil–water characteristic curve (SWCC). Most methods implicitly or explicitly derive a pore-size distribution (PSD) from the SWCC, which is then used to calculate k at any suction. Two important factors ignored by most methods are the change in the PSD during the SWCC test, and the influence of pore geometry on the SWCC. In this paper the SWCCs and evolution of the PSDs of four fine-grained compacted soils are measured. The SWCCs are measured from 0 to 3000 kPa by the axis-translation technique, and the PSDs are obtained by mercury intrusion porosimetry. A method is developed to predict the SWCCs from the measured PSD distribution data. Processes modelled include the effect of pore geometry on shrinkage during the SWCC tests, the isolation of water by the invading non-wetting phase (air), and differences in the relative accessibility of pores from the surface of the mercury intrusion and SWCC test samples. Different methods to model the above phenomena are developed and compared. The best predictions of gravimetric water content lie between one and two standard deviations of the measured SWCC data.

Predicting soil—water characteristic curves of compacted plastic soils from measured pore-size distributions

The unsaturated hydraulic conductivity function, k, is often predicted from the soil–water characteristic curve (SWCC). Most methods implicitly or explicitly derive a pore-size distribution (PSD) from the SWCC, which is then used to calculate k at any suction. Two important factors ignored by most methods are the change in the PSD during the SWCC test, and the influence of pore geometry on the SWCC. In this paper the SWCCs and evolution of the PSDs of four fine-grained compacted soils are measured. The SWCCs are measured from 0 to 3000 kPa by the axis-translation technique, and the PSDs are obtained by mercury intrusion porosimetry. A method is developed to predict the SWCCs from the measured PSD distribution data. Processes modelled include the effect of pore geometry on shrinkage during the SWCC tests, the isolation of water by the invading non-wetting phase (air), and differences in the relative accessibility of pores from the surface of the mercury intrusion and SWCC test samples. Different methods to model the above phenomena are developed and compared. The best predictions of gravimetric water content lie between one and two standard deviations of the measured SWCC data.

The influence of pore geometry in cp Ti-implants--a cell culture investigation.

Biocompatibility testing of differently structured titanium implants was performed using an in vitro test system of a newly established human fetal osteoblastic cell line (hFOB 1.19). Cell adhesion of osteoblastic cells on the different porous geometries and the suitability of a copper vapor laser system for surface structuring was tested with the following parameters: cell-number, cell viability, alkaline phosphatase expression. The analysis of the cell culture results demonstrated that 25 microm and 200 microm porous geometries showed similar or even better results than the negative control of polystyrene; there was no sign of toxic effects. However, the 100 microm porous geometry showed an impressive negative influence on the calculated parameters. The reason for this effect is unclear. The series with 50 microm, 300 microm, 400 microm and 500 microm showed a comparable, intermediate effect on the cell culture with respect to the different parameters. However, the results were worse than with the 25 and 200 microm porous geometry. In conclusion, the 25 microm and 200 microm porous geometry seems to have the most positive effect on the human osteoblastic cell line hFOB 1.19.

Influence of pore geometry on the effective response of porous media

The generalized method of cells (GMC) is used to study the influence of pore geometry on the effective elastic properties and inelastic response of porous materials. Periodic microstructures with four distinct pore geometries are studied and the results for effective elastic properties are compared with several other available models and experimental results. Predictions for the inelastic response of porous alumina are presented for tensile loading, as a function of pore geometry and pore volume fraction, with the inelastic behavior of the bulk material modeled using a unified visco-plasticity theory. All results are presented for discrete pore shape and discrete porosity. It is shown that pore geometry can have a significant influence on both elastic and inelastic response, that pore geometry can be associated with parameters from other models, and that the generalized method of cells is an efficient, flexible and reliable method of analysis for such problems.

Influence of pore geometry on the design of microporous materials for methane storage

The advantages of storing methane by adsorption in microporous materials are briefly reviewed, and the merits of currently available zeolites and microporous carbons are discussed. Grand canonical ensemble Monte-Carlo computer simulations of methane in slit pores (to model porous carbons) and cylindrical pores (to model zeolites) were carried out to determine the best geometry and the optimal pore size for storing the maximum amount of methane at a given storage pressure. At 274K, the optimal material is a porous carbon of pore size sufficient to contain two adsorbed layers of methane. At 500 psi (3.4 MPa), the energy density of such a material at 274K is only a quarter that of gasoline. These results suggest that an optimal zeolitic material would be a less useful material for adsorptive storage of methane than an optimal porous carbon. 21 refs., 10 figs., 3 tabs.