Degree Of Water Saturation Research Articles

The Water-Dependent Evolution of Pore Size Distribution due to Hydro-Chemical Transport within Cement-based Materials

This work explores the evolution of pore structure by considering the coupling effect of ionic transport and chemical reaction, especially salt precipitation. The reactive transport system is based on two sets of equations: a set of partial differential equations based on mass conservation for the ionic transport, and a set of nonlinear algebraic equations based on the law of mass action for the chemical processes. By adopting this model, transport properties such as ionic concentration and mass of chemical components are implemented. The porosity and the water saturation degree are also considered and examined in our work. Besides, we propose a probabilistic-based porous network representing the evolution of microstructure induced by precipitation/dissolution. The probabilistic porous network is the interconnection between the microstructure and the macro properties. With a given water saturation degree and porosity calculated by the reactive transport model, we could establish the water-dependent evolution of pore structure in cement-based materials. Such a numerical model could be used to interpret the mechanism of the local precipitation/dissolution process in pore scales, which cannot be implemented by experimental measurements.

Forced gas injection and water infiltration into sand — A two‐phase flow barrel and column experiment

AbstractSoil aeration (i.e., soil air content and composition) is of major importance in agricultural and environmental practices. Poor aeration reduces plant growth, development, yield, and resistance to diseases and other abiotic stresses (e.g., salinity). In many soils contaminated with hydrocarbons, low O2 supply limits the rate of contaminant decomposition and prolongs remediation. Soil aeration is governed by diffusion of O2 from the atmosphere and countercurrent diffusion of CO2 to the atmosphere. Injection of air (with an atmospheric O2 concentration of 20.9%) into poorly aerated soils is expected to improve soil aeration by enriching it with O2 and extracting CO2. In addition, air flow causes redistribution of soil water. Water redistribution is affected by operational (discharge rate, frequency, duty cycle) and geometrical (depth and distance between sources) air injection parameters, soil parameters (e.g., water retention and conductivity), and irrigation geometry and scheduling. We studied forced one‐ and three‐dimensional air (or N2) and water injection into packed wet sand and analyzed the effect of air injection on soil aeration and water redistribution in granular media. The study demonstrates the applicability of the Darcy–Buckingham law to air flow at different degrees of water saturation and for a large relevant range of capillary numbers. We also suggest a simple method to measure the soil's conductivity to air (Darcy's constant) for different air contents and use a simple analytical solution to estimate O2 diffusion from the atmosphere. We discuss the effect of operational air injection parameters on aeration's effectiveness and efficiency.

Determination of normative values of mechanical indicators of bonded soils based on dynamic probing data

In the work on the basis of analytical analysis of tabular data, both current and previous domestic regulatory documents on civil engineering, for mechanical indicators of bonded soils of natural occurrence graphic and analytical (formula) interpretation of these values in relation to the values of the dynamic probing index of Pd, MPa, and yield index IL, units, for the degree of water saturation of these soils Sr ≥ 0.8 units is given. Correlation with the value of dynamic probing of Pd, MPa allows not only to differentiate engineering and geological (geotechnical) cross-sections, more or less detailed, but also to estimate the load-bearing capacity of selected layers of bonded soils accurately enough. The theoretical analysis has shown that the values of mechanical indicators of natural bonded soils adopted in the current regulatory documents, even taking into account their structural strength, can not be directly used as a prototype to assess similar indicators of compacted technogenic soils of artificial structures in the form of embankments of hydraulic dams, road embankments or airfields. This is due to the fact that in the vast majority of cases in civil construction assessed the properties of soils in the plastic state, which tend to have a lower density of dry soil than at the border of rolling, and a mandatory condition for the use of such soils in artificial soil structures is their compliance with the requirements of the so-called standard compaction, that is, the density of dry soil there should be more than the density of dry soil at the border of rolling. These soils are in a solid state (their concentration is ≥ 85 %) and indeed (through direct contact between the soil parts) work as an elastic body and can be characterized by a modulus of elasticity with a corresponding small elastic deflection lmax and a sufficiently large design critical resistance value of R0 ≥ 0.6 MPa, which must be determined at each laboratory test of the samples before they fracture or disproportional movement of the stamp.

Zmiany właściwości konsolidacyjnych, filtracyjnych i mikrostrukturalnych glin lodowcowych w przebiegu badań konsolidacji z ciągłym wzrostem obciążenia

Changes in the consolidation, seepage and microstructural properties of glacial tills estimated in continuous loading tests. A b s t r a c t. The article presents results of CRL (Constant Rate of Loading) tests obtained for glacial till from the Warsaw region (Fort Sluzew). The analyses show that the significant factors affecting the course of the consolidation with continuous loading (CL) of tested soils are related to the degree of water saturation of pore space, the state of soil structure, and the rate of loading. Values of filtration and consolidation parameters documented during CRL tests are dependent on the structural history and properties of soils. Before and after CRL tests, microstructure of till was studied by SEM methods. Changes in the pore space parameters in matrix microstructure, evaluated from CRL tests, are marked in different consolidation behaviours of tested natural and remould till.

Tailing dams formation algorithm

The object of research of the present work is the tailing dump, located on the territory of north of Siberia. Based on the operating conditions of alluvial storage in permafrost, it should be noted that the increase in the annual capacity of the layer may not provide its complete consolidation during short spring-summer period before freezing. Thus, it will reduce the stability of the structure. In order to optimize the inwash technology of tailing dam, it is necessary to determine the time of tail’s consolidation. On the basis of laboratory tests, the approach to coefficient definition of filtrational and secondary consolidation of tails during alluvium depending on a physical condition, density, water saturation degree, and the mathematical model to calculate the time of their consolidation has been developed. The results obtained from researches can be successfully used as a basis for constructing consolidation models of required layer tails.

An elastoplastic model of frost deformation for the porous rock under freeze-thaw

Freeze-thaw action has caused many engineering geology disasters in cold regions, such as frost cracking of tunnel and pavement, rockfall of rock slope, falling off of building materials. The freeze-thaw damage of porous rock is mainly induced by the frost heaving pressure due to pore water freezing. Although some elastic crystallization theories have been proposed to model the freezing process of pore water, the long-term frost heave characteristics under cyclic freeze-thaw are rarely studied. The ice crystallization and frost heave theory under freeze-thaw have been developed in the elastoplastic regime in this study. A novel elastoplastic model has been proposed to estimate the long-term frost heave and frost damage under freeze-thaw. This model has considered the influence of the pore size, yield stress of matrix and degree of water saturation on the development of the frost heaving pressure in pores. During freezing, a plastic region will produce inside the matrix around the pore. This plastic region gradually expands outwards with the increase of this pressure. During thawing, the elastic deformation will be recovered but a considerable residual plastic strain is accumulated. However, the growth rate of the residual plastic strain will decrease under freeze-thaw due to the production of new empty voids. Therefore, the freezing of pore water in porous rock is an elastoplastic problem. Besides, the water saturation and mechanical properties of the porous rock are very important to quantify the frost heave. This study provides a better understanding of the frost damage of the porous rock and a reference for the stability of rock engineering under freeze-thaw in cold regions.

Study of the Effect of Movable Water Saturation on Gas Production in Tight Sandstone Gas Reservoirs

The movable water saturation of tight sandstone reservoirs is an important parameter in characterizing water production capacity, and there is a great need to understand the relationship between movable water saturation and water production characteristics. However, movable water behavior in this context remains unclear. In this study, four groups of tight sandstone cores from the Sulige gas field are measured to understand the movable water saturation characteristics. Then, the effects such as reservoir micropore throat, clay mineral and physical properties on movable water saturation are analyzed, and the movable water saturation and water production characteristics are discussed. The results show that higher movable water saturation will result in a greater amount of water in the gas drive. There is a critical pressure difference of the gas drive, and a large amount of movable water will flow out. Movable water saturation is independent of the porosity, permeability and initial water saturation, while it is closely related to the reservoir micropore throat and clay mineral content. Movable water is mainly distributed in the medium and large pores; the larger the proportion of such pores, the higher the degree of movable water saturation. A lower mineral content will lead to higher movable water saturation in tight sandstone gas reservoirs. These results provide clues for identifying gas–water bearing reservoirs and evaluating and predicting the water production characteristics in gas wells in tight sandstone gas reservoirs.

Dynamic response and meso-deterioration mechanism of water-saturated sandstone under different porosities

The dynamic response of sandstone to porosity and the amount of water are crucial to understanding the role of these physical parameters on the dynamic behaviour of rock. This study used four different types of sandstone, selected based on a microscopic analysis, for experimental tests and an analytical evaluation. During the experimental tests, dynamic compressive examination was employed on these types of sandstone under both water-saturated and dry states. The ratio of dynamic mechanical parameters of water-saturated sandstone to those of dry sandstone was focused on to eliminate the effect of the self-properties of the sandstone. The results indicate that the effect of water saturation on the dynamic mechanical properties of sandstone significantly affected by the porosity and the weakening degree of water saturation to sandstone positively correlates with the porosity. This effect is intuitively expressed in the features of the fracture propagation as recorded by a high-speed camera and dominated by the micromechanics between the pores and microfracture. This is microscopically attributed to the effect of the pore water pressure and the Stefan effect between the fracture surface and water on the fracture initiation and propagation. In addition, the dynamic mechanical model was further established and applied to discuss the effect mechanism of porosity on the dynamic behaviour of water-saturated sandstone. These insights can contribute significantly to improving the safety and cost-effectiveness of water-saturated rock engineering.

Ultrasonic Imaging of the Onset and Growth of Fractures Within Partially Saturated Whitby Mudstone Using Coda Wave Decorrelation Inversion

AbstractUsing active ultrasonic source survey data, coda wave decorrelation (CWD) time‐lapse imaging during the triaxial compression of Whitby Mudstone cores provides a 3‐D description of the evolution and redistribution of inelastic strain concentrations. Acoustic emissions (AEs) monitoring is also performed between any two consecutive surveys. From these data, we investigate the impact of initial water saturation Sw on the onset, growth, and reactivation of inelastic deformation, compared to the postdeformation fracture network extracted from X‐ray tomography scans. Our results indicate for the applied strain rate and degree of initial water saturation, and within the frequency range of our ultrasonic transducers (0.1 to 1 MHz), that inelastic strain localization and propagation in the Whitby Mudstone does not radiate AEs of sufficient magnitude to be detected above the average noise level. This is true for both the initial onset of inelasticity (strain localization) and during macroscopic failure. In contrast, the CWD results indicate the onset of what is interpreted as localized regions of inelastic strain at less than 50% of the peak differential stress the Whitby Mudstone can sustain. The seemingly aseismic nature of these clay‐rich rocks suggests the gradual development of inelastic strain, from the microscopic diffuse damage, up until the macroscopic shear failure.

Assessing the impact of groundwater mixing and sea water intrusion on oil production in coastal oil fields using resistivity sounding methods

Issaran oil field is a major heavy oil field in the Western shoreline of the Gulf of Suez, Egypt, which is facing challenges in field development and operations. Therefore, it is under development for many years to identify the required parameters to improve the quality of the produced oil. Identifying the source of groundwater mixing with heavy oil during the production process is a prerequisite. Geoelectric resistivity survey is suggested to identify aquifer characteristics, as well as the distribution of structural elements affecting the groundwater aquifer in Issaran oil field. A total of 94 Vertical Electrical Resistivity Soundings (VESs) were conducted to evaluate the groundwater aquifer. The recorded VESs were corrected and modeled to create two-dimensional profiles (2D) and areal contour maps throughout the studied site. Geoelectric modeling revealed five distinct resistivity subsurface layers. The top three layers are corresponding to dry friable gravelly sand and alluvial sediments of a total thickness of about 15–70 m and resistivity values ranging from 15 to 200 Ω m. The fourth layer represents the groundwater bearing horizon and is characterized by high degree of saline water saturation, where resistivity ranged from 0.5 to 15 Ω m. Finally, the lower stratigraphic layer is characterized by its relatively high resistivity (greater than 70 Ω m), and it is not observed through all the conducted VESs. The findings shows that the groundwater bearing horizon is structurally controlled and is mainly affected by the Red Sea structural regime, which could act as seawater passages to the oil field area.

Pressure-dependent cross-property relationships between elastic and electrical properties of partially saturated porous sandstones

Successful joint inversion of seismic and electromagnetic survey data to estimate parameters and improve the characterization of the earth’s subsurface relies on the understanding of the cross-property relations between the elastic and electrical properties. Pressure-dependent cross-property relationships of rocks with varying degrees of fluid saturation remain poorly understood even though such conditions are encountered frequently. We investigate this problem by designing and undertaking dedicated laboratory experiments to simultaneously measure the elastic velocity and electrical resistivity in two Berea sandstone samples subject to varying confining pressure and water saturation, using a state-of-the-art joint elastic-electrical measurement system. P- and S-wave velocities are found to increase exponentially with increasing confining pressure at each water saturation, whereas electrical conductivity can either increase or decrease with confining pressure depending on the degree of water saturation. More interestingly, the elastic and electrical properties of the two samples are shown to be systematically correlated as functions of water saturation and the applied confining pressure. The correlations reveal the natural link between the elastic and electrical properties in the two porous sandstones with partial water saturation, and they help to better indicate the fluid flow within compliant pores in addition to the known flow between stiff and compliant pores. The results will form the theoretical basis for the successful joint interpretation of seismic and electromagnetic survey data acquired from partially saturated porous rocks in the subsurface of the earth.

Influence of carbonation on the microstructure and the gas diffusivity of hardened cement pastes

The influence of carbonation on the oxygen-effective diffusion coefficient (De,O2) of hardened cement pastes (HCP) is investigated in the scope of durability. Experiments are carried out on HCP made with different binders (Portland cement, fly ash, slag, metakaolin binders) and water-to-binder ratios at three relative humidity levels. At a given RH, the change in De,O2 due to carbonation depends on the mix composition. However, in most of cases, De,O2 increases after carbonation, despite the porosity clogging. This is explained by both the decrease in the water saturation degree, especially at high RH, and the change in the pore size distribution. A good correlation is found between the mean pore diameter and gas diffusivity before and after carbonation at low water saturation degree (R2 > 0.84 on a log–log scale). De,O2 is significantly less dependent on the water saturation degree after carbonation.

Calculation of the Height of Capillary Rise of Water in Soils

Rain and melt water will form temporary accumulations of surface water on the surface. When they seep into the ground, temporary streams of leaky filter water are formed. If a limited section of water-resistant soil layer or the roof of an underground structure is encountered in the path of these waters, a temporary aquifer-the upper layer of ground water-may form above them. In temporary and permanent aquifers, the soil pores are completely filled with gravitational water, the degree of water saturation is equal to one, and there is pressure under the surface of underground water. Above this surface is a zone of capillary moisture, while the level of capillary rise is determined by the granulometric composition of the soil and ranges from tens of centimeters in sand to several meters in dusty and clay soils. Capillary water rises in the ground on free canals formed by mutually communicating pores, or is kept in them in limbo.The lifting of the liquid in the capillary continues until the gravity acting on the column of the liquid in the capillary becomes equal to the resulting force. Capillary water penetrates from the ground into the walls and rises to a height of up to 2 meters. The normal moisture content of the brick walls is 0.02...0,03, and in the case of unprotected contact with moist soil is increased to 0.15...0.25. On the inside of the walls there is a damp, mildew. Evaporating water increases humidity in the room, and the salts released when it evaporates from salt solutions lead to peeling paint, destruction of plaster and wall material.

Investigation of residual oil saturation in the process of filtration of viscous multicomponent flow with a wide range of pressures and temperatures

An experimental setup was created to study the process of oil displacement by supercritical CO2 and fringes of supercritical CO2 and water from the model of homogeneous and inhomogeneous formation of different degrees of water saturation. The process of multicomponent filtration of oil-water-supercritical CO2 systems at 333 K isotherm in the pressure range of up to 14 MPa was studied at the experimental plant. The new data, the oil displacement efficiency of supercritical CO2 from a homogeneous porous medium with water content of 65% and rims supercritical CO2, and water from homogeneous porous medium with a water cut of 25%. The results showed that the use of supercritical CO2 in the filtration processes of multicomponent reservoir systems allows further displacement of oil from the watered porous medium.

Thermal conductivity of supraglacial volcanic deposits in Iceland

Supraglacial deposits of tephra or volcaniclastics have the potential to cause significant anomalies of glacier ablation and runoff. The intensity of these anomalies is governed by the thermal resistivity of the covering layer and hence the thermal conductivity of the deposited grains. This study concentrates on causal and quantitative relationships between density, geochemical composition and thermal conductivity of volcanic materials based on the analysis of 43 samples from locations across Iceland. Thermal conductivity is primarily influenced by density, whereas geochemical composition has been proved to be of subsidiary importance. Four different multiple regression models were calibrated that calculate the grain thermal conductivity of a volcanic material based on rock properties and geochemical composition. In a subsequent step, the bulk thermal conductivity of the respective deposit is calculated as a function of porosity and degree of water saturation. Examples using volcanic material from the Eyjafjallajökull 2010 and Grímsvötn 2011 eruptions confirm that the presented calculation scheme can be executed using only limited geochemical data as input. This facilitates an easy application of the modeling scheme immediately after a volcanic eruption.

Serial Laboratory Effective Thermal Conductivity Measurements of Cohesive and Non-cohesive Soils for the Purpose of Shallow Geothermal Potential Mapping and Databases—Methodology and Testing Procedure Recommendations

The article presents the methodology of conducting serial laboratory measurements of thermal conductivity of recompacted samples of cohesive and non-cohesive soils. The presented research procedure has been developed for the purpose of supplementing the Engineering–Geology Database and its part–Physical and Mechanical Properties of Soils and Rocks (abbr. BDGI-WFM) with a new component regarding thermal properties of soils. The data contained in BDGI-WFM are the basis for the development of maps and plans for the assessment of geothermal potential and support for the sustainable development of low enthalpy geothermal energy. Effective thermal conductivity of soils was studied at various levels of water saturation and various degrees of compaction. Cohesive soils were tested in initial moisture content and after drying to a constant mass. Non-cohesive soils were tested in initial moisture, fully saturated with water and after drying to a constant mass. Effective thermal conductivity of non-cohesive soils was determined on samples mechanically compacted to the literature values of bulk density. Basic physical parameters were determined for each of the samples. In total, 120 measurements of thermal conductivity were carried out, for the purposes of developing the guidelines which allowed statistical analysis of the results. The results were cross-checked with different measuring equipment and with the literature data.

Combined Effects of Pressure and Water Saturation on the Seismic Anisotropy in Artificial Porous Sandstone With Aligned Fractures

AbstractFractures are commonly existing in the subsurface rocks, and understanding the seismic anisotropy in fractured rocks is of great importance in a range of geophysical applications. However, although all the fractured rocks are suffering from geological stresses and most of them are experiencing partial water saturation, the combined effects of confining pressure and water saturation on the seismic anisotropy in fractured rocks remain poorly understood. To obtain such knowledge, we measured and compared the anisotropic velocities and corresponding seismic anisotropy in two artificial porous sandstone samples with and without aligned fractures, respectively, as functions of varying confining pressure and degree of water saturation. We showed that the existence of aligned fractures significantly reduced the five measured velocities but dramatically enhanced the seismic anisotropy in the fractured sample. We also showed that confining pressure and water saturation had an interdependent complex effect on the seismic anisotropy of the fractured sample. The seismic anisotropy of the dry sample showed the highest‐pressure sensitivity, and the saturation effect was most significant at low confining pressure. Integrated interpretation of the experimental data indicated that wave‐induced fluid flow due to pore‐scale and mesoscale fluid distribution in the rocks is responsible for most of the observed pressure and saturation‐dependent anisotropic behaviors in the rocks. The results have helped to gain new knowledge on the seismic anisotropy in partially saturated fractured rocks subject to varying pressures and suggest the requirement for advanced theoretical models to fully understand the acquired data.

ФИЗИКО-ХИМИЧЕСКИЕ ОСНОВЫ СТОЙКОСТИ БЕТОНОВ К ВОЗДЕЙСТВИЮ НИЗКИХ ОТРИЦАТЕЛЬНЫХ ТЕМПЕРАТУР (ЧАСТЬ 2)

Generalization and analysis of scientific hypotheses and theories of domestic and foreign researchers in the field of the frost action mechanism on concrete has been performed. A critical author's assessment of them from the point of view of the basics of physical chemistry of silicates and solid state physics is presented. The initial prerequisites for the frost resistance of heavy concrete and equal-strength structural light concrete in connection with their structure are formulated, including of this article author's targeted experimental studies on the relationship of the frost resistance of these concretes with their pore structure. Thermodynamic models of freezing-thawing of water, including its adsorption layers in capillaries of cement materials porous structures are used. The data of studies of the critical degree of water saturation of concrete are considered and a reasonable assessment of it is given as an integral characteristic that determines the possibility of formation of micro- and then macro-defects in the concrete structure during its cyclic freezing and thawing. Based on the results of analytical and experimental studies, using the basic principles of physics of the solid state, as well as the physical and physical-chemistry of silicates, has been developed the physical-chemical basis for the resistance of structural lightweight concrete in comparison with equally strong normal weight concrete to the effects of low (up to minus 70 °C) subzero temperatures. The results of this work are considered by the authors as a modern scientific basis for the development of the main provisions of the technology for manufacturing structural lightweight and normal weight concretes with high durability (frost resistance and water resistance), intended for reinforced concrete structures of engineering constructions, operated in severe climatic conditions, including in the conditions of the Arctic coast.

Analysis of Water–Gas System Equilibria in Jurassic–Cretaceous Reservoirs (by the Example of the Yamal-Kara Depression)

Abstract —The paper presents results of the pioneering study of equilibria in the water–gas system by the example of Jurassic–Cretaceous deposits of the Yamal–Kara depression located within northern West Siberia and its Arctic regions. Numerical modeling of physicochemical equilibria and evasion–invasion processes in the water–gas system allowed determination of the degree of groundwater saturation with gases and the nature of diffusive redistribution of gases in the media that form at the hydrocarbon deposit–groundwater contact. According to the degree of water saturation with gases (Kg), aquifers with poorly (<0.2) to ultimately (0.8–1.0) gas-saturated waters have been established. The revealed increase in the degree of groundwater saturation with gases in sinking producing reservoirs reflects its dependence on their total gas saturation. All waters with a total gas saturation of more than 1.8 L/L become ultimately saturated with gases (Kg = 1.0), thus theoretically predetermining the formation of hydrocarbon accumulations. Major gas condensate deposits are confined to the zone of gas-saturated waters with Kg from 0.8 to 1.0, while oil accumulations, to waters with lower gas saturation. Based on the established nature of water–gas, we can argue that oil and gas accumulations in Jurassic–Cretaceous reservoirs act as a conservative element of the lithosphere, i.e., its geologic and geochemical “relics”. The surrounding subsurface waters, as a more active constituent of the system, have largely anticipated its geochemical development, which is manifested in the differentiation of the fugacity ratios of individual gases in groundwater and hydrocarbon accumulations. The composition of the latter is therefore subjected to slow directional changes while the equilibrium is established, to usher in the qualitatively new state of the geochemical water–gas system.

ФИЗИКО-ХИМИЧЕСКИЕ ОСНОВЫ СТОЙКОСТИ БЕТОНОВ К ВОЗДЕЙСТВИЮ НИЗКИХ ОТРИЦАТЕЛЬНЫХ ТЕМПЕРАТУР

Generalization and analysis of scientific hypotheses and theories of domestic and foreign researchers in the field of the frost action mechanism on concrete has been performed. A critical author's assessment of them from the point of view of the basics of physical chemistry of silicates and solid state physics is presented. The initial prerequisites for the frost resistance of heavy concrete and equal-strength structural light concrete in connection with their structure are formulated, including of this article author's targeted experimental studies on the relationship of the frost resistance of these concretes with their pore structure. Thermodynamic models of freezing-thawing of water, including its adsorption layers in capillaries of cement materials porous structures are used. The data of studies of the critical degree of water saturation of concrete are considered and a reasonable assessment of it is given as an integral characteristic that determines the possibility of formation of micro- and then macro-defects in the concrete structure during its cyclic freezing and thawing. Based on the results of analytical and experimental studies, using the basic principles of physics of the solid state, as well as the physical and physical-chemistry of silicates, has been developed the physical-chemical basis for the resistance of structural lightweight concrete in comparison with equally strong normal weight concrete to the effects of low (up to minus 70 °C) subzero temperatures. The results of this work are considered by the authors as a modern scientific basis for the development of the main provisions of the technology for manufacturing structural lightweight and normal weight concretes with high durability (frost resistance and water resistance), intended for reinforced concrete structures of engineering constructions, operated in severe climatic conditions, including in the conditions of the Arctic coast.