This paper presents a study of the dynamic adsorption of gas (methane) with single-phase flows in porous media. The purpose is to determine the effect of grain size distribution on dynamic adsorption at different ratios between inter- and intraparticle diffusion coefficients. The findings of this paper have been obtained using lattice Boltzmann equations and ’’computational rock physics’’ technology, which involves numerical simulations on binary images of porous structures. The results showed that grain size distribution and the ratio between inter- and intraparticle diffusion coefficients are factors affecting dynamic adsorption. It has been established that at low ratios between diffusion coefficients, dynamic adsorption is determined by surface adsorption and does not depend on grain size distribution. At high ratios, an increase in the standard deviation contributes to a slowdown in the total dynamic adsorption. In addition, it has been found that an increase in the variety of grain sizes promotes a significant decrease in the prediction reliability of the adsorption dynamics.

Contamination of soils and aquifers as a result of heavy metal ions adsorption is an extremely negative environmental phenomenon associated with natural or industrial disasters. This paper presents the first systematic study of the dynamic adsorption of heavy metal ions in soils during water-air immiscible displacement induced by pressure drop and gravitational force. This study addresses three objectives. The first purpose is to determine a representative elementary volume to estimate the adsorbed amount of heavy metal ions during two-phase flow with density contrast. The second objective is to study the effect of different balances between viscous and gravitational forces, described by the gravity number, on the adsorbed amount at drainage and imbibition regimes. And the final task is to identify the effect of the pore space heterogeneity on the adsorbed amount for various gravity numbers and wetting conditions. As samples of study, we examine two-dimensional granular digital images characteristic of soils. The lattice Boltzmann method, verified on the problem of capillarygravitational equilibrium of a meniscus, was used as a research tool. It has been established that the scale of 4-5 mm is sufficient to be representative for estimating the adsorbed amount of heavy metal ions. An increase in gravity number promotes the destabilization of the interfacial front both in the drainage and imbibition regimes and results in suppression of the adsorbed amount. The effect of gravity number on the adsorbed amount is stronger in the drainage mode compared to the imbibition regime. It has been found that pore space heterogeneity is a factor negatively affecting the adsorbed amount of heavy metal ions. The strength of the heterogeneity effect is independent of wetting conditions and gravity numbers.

Research subject. Framboidal pyrites and sulfide micro-concretions in carbonaceous-siliceous and ore rocks of the Safyanovskoye deposit (Middle Urals). Aim. To identify the signs of vital activity of microbial communities in bottomhydrothermal deposits using the example of the Safyanovskoye sulfide deposit. The methods. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). Results. TThe analyzed ore and carbonaceous-siliceous rock samples showed the presence of mineralized silicon dioxide films covering framboidal pyrites. Micro-concretions were found to consist of microfossils of filamentous organisms and framboids. Pyrite samples included the remains of tubular casts of sulfidized vestimentifera and polychaetes, associated with framboids. The possibility of using fossilized remains of microbial communities for distinguishing bottom-hydrothermal facies among pyrite deposits was confirmed. Conclusions. Hydrothermal-sedimentary deposits are characterized by the traces of specific microbial communities, since prokaryotic organisms were pioneers in hydrothermal oases. Their long active existence created a basis for the second trophic link, i.e. filter feeding macrofauna and endosymbiotrophs. These organisms, in turn, formed another level in the food chain of the trophic pyramid. It is believed that micro-concretions and framboidal pyrites are indicators of the vital activity of microbial communities.

A number of soils and parent rocks at different stages of weathering were investigated for the formation of heterogeneous wettability under residual hydrophobic contamination in situ. The aim of the study was to determine specific wetting contact angles of soils and parent rocks under different conditions. The wetting contact angle was measured by the captive bubble method, which implied attaching an air bubble to the specially prepared horizontal surface of a water-placed specimen with subsequent measuring the wetting contact angle according to the profile of the bubble’s photo. The soil specimens were artificially hydrophobized using media containing less than 1 wt % of oil degradation products with adapted microflora. Leached chernozem, alluvial silty loam, bentonite, dolomite–clayey marl, ornamental marl, and phyllite were studied. Based on the Pearson’s goodness-of-fit criterion, good angular data approximation by both the von Mises–Tikhonov distribution and the normal distribution was found. The dependence of the types and parameters of statistical distributions of the wetting contact angle on hydrophobization conditions of the specimens was revealed. The formation of the specimens’ hydrophobicity exclusively under introduced organic matter and incomplete water saturation conditions was found; at the same time, a high heterogeneity of wettability and hydrophobic areas at wetting contact angles above 129° was manifested. The results of the study can be useful for assessing and predicting the impact of soil hydrophobic contaminants and amendments, as well as for advancing methods for determining the wetting contact angle on the soil surface.

This paper presents a systematical study of the effect of porosity, pore-level heterogeneity and anisotropy on the absolute permeability of digital images of porous media. The main goal is to develop an analytical formula that estimates permeability as a function of these three parameters at once. Permeability is assessed based on numerical simulations using the lattice Boltzmann equations. Digital models of porous media are generated by a combined method consisting of Monte-Carlo and quartet structure generation set (QSGS) algorithms. Increase in heterogeneity negatively affects permeability. With an increase in porosity, the effect of heterogeneity on flow properties decreases. There was a linear decrease in permeability during the transition between favorable and unfavorable anisotropy. The influence of anisotropy is most pronounced in samples with high porosity and monotonically reduces with decreasing porosity. Heterogeneity negatively influences on the sensitivity of flow properties to changes in anisotropy and independent on porosity.

This paper systematically investigates the impact of porous mediadisorder and its coupling with flow rates, favorable andunfavorable viscosity ratios, as well as surface tensions on thedynamics of interfaces development during two-phase drainage flow.A special attention is paid to establishing relationship betweenthe dynamics of fluid–fluid and fluid–solid interfacial lengths,the pore selectivity and the displacement efficiency using imagingof fluids distribution in porous media. As samples of study, weused artificially generated models of porous media with differentdisorder parameters and with two-types of pore-channels systems"— hexagonal and square. In our methodology, the disorderdefines the range of grain size distribution and is applied tocontrol the pore size range. For two-phase flow simulation, thelattice Boltzmann equations and the color-gradient model areapplied. It was established the linear relationships betweenfluid–fluid and fluid–solid interfacial length and saturation ofthe invaded fluid. During numerical simulations at differentdisorders, the lack of disorder effect on the fluid–fluidinterface dynamics and negative disorder impact on thefluid–solid interface dynamics was found. When varying the flowparameters, it was identified that the increase in thefluid–fluid interface dynamics is accompanied by a decrease inthe fluid–solid interface dynamics. For all displacementmechanisms considered in this paper, except capillary fingering,an inverse relationship between pore selectivity and pore number,involved in displacement, was detected. We found a shift of poreselectivity towards higher values with increasing disorder whichnegatively impacts on the displacement efficiency. In capillaryfingering regime, a strong tendency to minimize fluid–fluidinterfacial length with surface tension explains the lack ofrelationship between pore selectivity and pore number which leadsto bad predictable displacement efficiency in this regime.

Microorganisms emit substances changing the surface tension of soil solution and the surface energy of solid soil particles. Clays and soils have high heterogeneity of the surface energy distribution among particles. The change in the surface energy of soil particles is caused not only by alteration of their chemical properties but also an increase/decrease in their spatial heterogeneity, which determines contact angle hysteresis. Available techniques of measurement the contact angle and the contact angle hysteresis require further improvement and adaptation to specific clay types. The purpose of this research is to study the change in wettability of clays due to the influence of mesophilic soil microorganisms’ activity when adding model contaminants: water-in-oil emulsion, glycerol and oleic acid. During the experiments, the objectives of this study were to specify peculiarities of wetting contact angle hysteresis of clays with substrates of different mineral composition and microbial activity. Hydrophilicity/hydrophobicity of the stimulator for microbial activity does not have a clear effect on clay properties. The surface heterogeneity mostly increases with time, perhaps, due to biofilm exudates whatever was a type of microbial stimulator. Chemical and geometric heterogeneities played comparable roles in the surface hydrophilic-hydrophobic balance. Results obtained prove that microbial communities and/or the Fe chemical state alteration (pyrite, hematite or goethite) were responsible for both hydrophilization and hydrophobization of the surface. The equation for the drop spreading rate was presented and verified by well comparison of experimental results with simulations.

Relevance of the study is due to the importance of composition and maturity of the dispersed organic matter (DOM) as indicators of rock forming conditions, which may contribute to the paleoecological reconstruction of sedimentation conditions for rocks in the ore-bearing stratum of the Safyanovskoe deposit. Objective: to analyze the composition and characteristics of DOM in carbon-siliceous rocks of the ore-bearing stratum of the Safyanovsky copper-pyrite deposit. The obtained characteristics of the DOM make it possible to reveal the source of original accumulation and the level of its transformation under the influence of various geological processes. Methods. A detailed study of DOM was carried out by the EPR method (electron paramagnetic resonance) for powder preparations. EPR spectra were recorded at room temperature on X-band spectrometers DX-70, ESR 70-03 DX/2, and SE/X-2547 RadioPAN. The analytical procedure for studying organic matter (OM) included: determination of insoluble residue and C org content in the rock, extraction of the chloroform bitumoids (CB) and the alcohol-benzol bitumoids (ABB), humic acids (HA), determining the group composition of CB and hydrocarbons (HC), chromatographic fractionation with determination of the sum of methane-naphthenic and aromatic fractions of hydrocarbons, GC-MS analysis of n-alkanes, cyclic and polyaromatic hydrocarbons (PAHs). GC-MS analysis was performed on the complex Hewlett Packard 6850/5973 with a quadrupole mass detector and analytical information processing software. Results. Analysis of the EPR spectra of carbon-siliceous rocks of the Safyanovskoe deposit showed the presence of the two types of carbon signal (C-org), characteristic of the plant and the animal residues. It was also found that the DOM has never been exposed to temperatures greater than 300 °C. Geochemical analysis of OM indicates that DOM is at a high maturation stage (residual organic matter (ROM) > 99%). But the type of distribution of polyaromatic hydrocarbons (PAHs) suggests that the primary OM was specifically altered at elevated temperatures. Conclusions. DOM of carbon-siliceous rocks of the Safyanovsky deposit is genetically the same, its type is mainly sapropelic and accumulation is associated with marine conditions. A characteristic feature is, on the one hand, its high polymerization, which is typical for DOM of the stage of late mesocatagenesis, and, on the other hand, its molecular composition does not allow us to talk about the maturation of DOM in the process of natural regional metamorphism.

In this paper, we investigate the effects which are manifested at two-phase drainage flows in porous media at domination of capillary forces - Haines jumps. This pore-scale event is a rapid or burst-like invasion process and is reflected in sharp pressure drop during drainage displacement. This phenomenon was explored in three-dimensional digital model of natural sandstone which was extracted using X-ray computed tomography. For two-phase flow simulation the lattice Boltzmann equations (LBE) were used. The interface interactions between fluids and wetting effects were modeled with color-gradient method in framework of the LBE. We performed an association between pressure drop at Haines jump and direct imaging of corresponding rapid invasion event in 3D model. It was shown that Haines jump occurs at meniscus migration from narrow pore throat to its wide body. The velocity of meniscus displacement exceeds bulk flow rate in more than 100 times and it looks like burstlike invasion. Also, we studied the effects of flow rate and surface tension on Haines jumps statistics. It was revealed that Haines jumps at high flow rates occur simultaneously and individual jumps can’t be distinguished on pressure signal. At regimes, where only individual Haines jumps take place, the flow rate influence is insignificant and the distribution of pressure drops can be fitted using lognormal law. Increasing of surface tension leads to growth of mean value of pressure drop and amount of Haines jumps.

The influence of tectonic processes on the transformation of organic matter in volcanic and volcano-sedimentary rocks within the East Ural uplift in the southern Rezh structural-formational zone was studied. The basic features and temperature ranges of organic matter (OM) and ore-bearing rock metamorphic transformations in the Saf'yanovka deposit were established using the methods of thermal analysis, electron paramagnetic resonance, and complex geochemical studies, including GC-MS. The geochemical study of organic matter in the ore-bearing rocks of the Saf'yanovka deposit confirmed its relation to the sapropelic type and to shallow marine conditions of formation. The syngenetic nature of the OM and ore-bearing rocks was established on the basis of the geochemical and physicochemical analyses. The transformation stage of OM in the Saf'yanovka deposit indicates its rapid, but incomplete maturation in the evolution of hydrothermal fluid.

This paper investigates the calculation features of sandstones absolute permeability coefficients on their digital images using the lattice Boltzmann equations (LBE) and Navier-Stokes equations (NSE). The main attention in this work is given to comparison of numerical solutions of NSE and LBE, and to study the effects of grid refinement and grid coarsening on the calculated permeability coefficient. 3D digital images of sandstones were obtained using X-ray computed tomography. The permeability coefficients were calculated in sandstone samples from Imperial College London open library as well as from Ashalchinskoe (Tatarstan, Russia) and Vostochno-Birlinskoe (Ulyanovsk region, Russia) oil fields. When using LBE, a multi-relaxation time collision operator was applied. It was shown that permeability coefficients, calculated using LBE, of original digital images are 20-30% higher than when using NSE. The study of grid refinement was performed at the refinement levels ranges from 2 to 10. In this paper, the level of grid refinement characterizes the multiplicity of the grid step splitting. Strong dependence of the permeability coefficients on the grid refinement level was revealed for each mathematical model. The NSE solutions are significantly less sensitive to the refinement level in comparison with LBE solutions and the discrepancy between them decreases with increase in the refinement level. The grid independence of the NSE solution is achieved at grid refinement level 3, whereas for LBE even refinement level 10 is not enough for this. Issues arising from grid coarsening are discussed and solutions are developed at coarsening resolutions in two and three times. It was found that grid coarsened in two times is valid for single-phase flow simulations and for calculation of permeability coefficients with good accuracy of <10% error compared to original grid. This result allows one to reduce the grid dimension in 2(3) times which can significantly economy computational cost. For grid coarsened in three times, the calculated flow characteristics deviate by more than 10% from the initial values, but deviations decrease with increasing permeability. (C) 2018 Elsevier Ltd. All rights reserved.

We have investigated the features of using STR and MTR models of lattice Boltzmann equations for calculating the filtration characteristics of porous media with the use of their digital images. The results of calculations performed on the basis of these models were compared with the results of analytical calculations made with the use of stationary Navier–Stokes equations and continuity equations. Calculations of the laminar flow in a pipe with the use of the MTR model had a much higher accuracy as compared to analogous calculations by the SRT model and showed independence of the relaxation parameter. It has been established that for fluid flow in pore channels the MRT model and the Navier–Stokes equations give comparable results, whereas in using the SRT model the numerical solution depends on the relaxation parameter.

The results of numerical simulation of the processes of two-phase flow through a porous medium in three-dimensional digital models of the porous space of three natural sandstone samples are given. The calculations are carried out using the lattice Boltzmann equations and the digital field gradient model over a wide range of the capillary numbers and the viscosity ratios of injected and displaced fluids. The conditions of flow through a porous medium with capillary fingering, viscous fingering and with stable displacement front are revealed.

Nodules of different compositions from Paleozoic sedimentary rocks and those deposited by microbial communities in laboratory-scale experiments were studied by the use of electron paramagnetic resonance, X-ray diffraction, and scanning electron microscopy with energy-dispersive spectrometer. The study of the mineral composition of fossil nodules showed that they have monomineral composition of dolomite or chalcedony, mixed composition of dolomite-chalcedony or of opal-dolomite, and finally nodules can be composed of alternating opal and chalcedony layers cementing fine dispersed dolomite grains or clusters of irregular shape. Similarity in dolomite crystal lattice defects in both the nodules and the host rocks confirms their formation during synsedimentary early diagenesis. Bacterial activity during sedimentary nodules growth is evidenced by the presence of paramagnetic carbon-centered free radicals of fossilized protein substances and findings of fossil bacteria. Experimental laboratory-scale modeling of natural carbonate deposition by microbial communities confirms that bacteria can promote nodules formation.

We report the use of X-ray micro-CT and numerical simulations for studying the reservoir properties of sandstone and carbonate rocks in the Melekess depression of the Volga-Ural anteclise, Russia. To simulate the flow of a viscous fluid in the pore scale, we use a mathematical model which consists of the continuity equation, stationary Navier-Stokes equations and Darcy law. As a result of computational micro-scale experiments on digital three-dimensional images of sandstone, we get satisfactory compatible permeability coefficients, which are calculated using Navier-Stokes and Kozeny-Carman equations. Carbonates with fracture porosity reveals significant variations in permeability coefficients, calculated by the two methods. The Kozeny-Carman equation can describe the flow properties of carbonates with a predominantly matrix porosity. It is shown that a pronounced heterogeneity of the pore space leads to the representative elementary volume for permeability coefficient in carbonates several times larger than in sandstones.

X-ray computed microtomography investigated filtration-capacitive characteristics of core sand Ashalchinsk reservoirs series. To simulate the flow of a viscous fluid in the pore scale we use a mathematical model, which consists of the continuity equation and stationary Navier - Stokes equations. It was shown that Kozeny - Carman formula gives curtained values of permeability coefficients, compared with filtration characteristics calculated using the Navier - Stokes equations. It was revealed that the reservoir properties of cores, calculated on the basis of microtomography data can be extrapolated to the samples of porous media with larger scale.

Carbonates from Amfiteatr and Chudnoe gold ore deposits (Nether-Polar Urals) were studied by a number of physical-chemical methods to reveal typomorphic features of carbonate mineralization. Only insignificant changes in the parameters of carbonate crystal structure caused by the presence of isomorphic impurities were observed by X-ray diffraction analysis. The EPR spectra showed the presence of dispersed organic matter with a high degree of metamorphization in the rocks of the Amfiteatr deposit. Two generations of dolomite (marine sedimentary and hydrothermal wallrock) were also revealed. Hydrothermal calcite from the Chudnoe deposit was characterized by a high degree of structural imperfection. According to the type of origin, submarine sedimentary and hydrothermal veined facies were distinguished. As regards the process of gold mineralization, hydrothermal veined carbonates correspond to the early alkaline pre-ore stage at the Amfiteatr deposit and the late alkaline post-ore stage at the Chudnoe one.

Au-Pd-проявлении Чудное - в позднещелочную пострудную.Carbonates from Amfiteatr and Chudnoe gold ore deposits (Nether-Polar Urals) were studied by a number of physical-chemical methods to reveal typomorphic features of carbonate mineralization. Only insignificant changes in the parameters of carbonate crystal structure caused by the presence of isomorphic impurities were observed by X-ray diffraction analysis. The EPR spectra showed the presence of dispersed organic matter with a high degree of metamorphization in the rocks of the Amfiteatr deposit. Two generations of dolomite (marine sedimentary and hydrothermal wallrock) were also revealed. Hydrothermal calcite from the Chudnoe deposit was characterized by a high degree of structural imperfection. According to the type of origin, submarine sedimentary and hydrothermal veined facies were distinguished. As regards the process of gold mineralization, hydrothermal veined carbonates correspond to the early alkaline pre-ore stage at the Amfiteatr deposit and the late alkaline post-ore stage at the Chudnoe one.