Swelling Of Clay Minerals Research Articles

Methane Adsorption and Desorption on Continental Shaly Matrix: Implications for Shale Gas Condensate Exploration and Production.

Shale gas condensate is a burgeoning unconventional resource with adsorbed methane (CH4) as its dominant component. Successful evaluation of marine shale gas gives limited insights into the evaluation of continental shale gas condensate due to their different occurrence patterns of organic matter and inorganic minerals and resultant contributions to pore development and CH4 ad-/desorption capability. To address this issue, we employed an advanced low-temperature oxygen plasma (LTOP) technology to extract organic matter from the continental shaly matrix. Results showed that the continental shaly matrix contains more clay minerals and less quartz, and develops fewer pores and fractures than typical marine shaly matrix. The organic matter-hosted pores instead of inorganic mineral-hosted pores are more weighted to the pore development in the continental shaly matrix. However, the inorganic minerals of the continental shaly matrix contribute more to CH4 adsorption capability than the organic matter, which could be attributed to the higher density of available adsorption sites toward CH4. Besides, the CH4 ad-/desorption hysteresis is more pronounced for the organic matter-free continental shaly matrix than the raw continental shaly matrix, which is attributed to the remarkable CH4 adsorption-induced clay mineral swelling. Overall, the effects of inorganic minerals in CH4 adsorption and desorption, particularly clay minerals, are crucial for continental shale gas condensate exploration and production.

Wetting-induced collapse of loess: Tracing microstructural evolution

Loess is a silt-dominated, clastic yellow-to-yellowish brown aeolian sediment with high porosity and low density. The metastable microstructure of loess makes it highly susceptible to collapse, which plays a major role in landform evolution, geohazard development and engineering damages, particularly the widespread occurrences of settlement, deformation and cracking of civil engineering structures. Differing from the existing investigations based on pre- and post-collapse comparison, the present study is to report the microstructural changes during the collapse process and to determine how each microstructural constitutive element participates in this process. A series of laboratory tests was conducted on undisturbed loess specimens to simulate and capture snapshots of microstructure at five representative points during the entire collapse process. Results show that the loess microstructure becomes more homogeneous as the outstanding macropores are crushed into smaller (meso- and mini-pores) pores, the number of pores is dramatically increased, and the pore throats become narrower. The pore shapes have no obvious changes and remain elongated and rough-edged morphology from the point of view of statistic. Regarding solids, the pre-collapse unstable point-to-point contacts tend to transform into relatively stable edge (edge-edge or point-edge) type contacts, whilst coarse particles tend to reorient along the horizonal direction. XRD, SEM and EDS analysis indicates that these changes in the nature and distribution of pores and particles result from (1) the breakage and disintegration of moderately to highly weathered particles, (2) the disintegration of the matrix due to the swelling of clay minerals and the dissolution of calcium carbonates, (3) the consequential modifications of the microscopic forces which lead to slipping, rotation and therefore dislocation of particles, and (4) the collapse of mesoscale force chains along particles, reforming on smaller scales with larger numbers, shorter lengths and horizontal alignments.

Нydrogeological characteristics and analysis of the compatibility of disposal and formation water at the field N in Western Siberia

The article presents the hydrogeochemical characteristics of a field located in the West Siberian megabasin in Khanty-Mansiysk Autonomous Okrug — Ugra, the peculiarity of the hydrogeochemical conditions of which is confined to the elysium lithostatic system and inversion hydrogeochemical zonality. This is characterised by a decrease in mineralisation with depth and a change in formation water type. This is related to the transformation of organic and mineral matter in sedimentary rocks at the elision stage of the West Siberian megabasin development during their sinking and compaction. The object of placement of formation and used water is the Aptian-Albian-Cenomanian hydrogeological complex.The article calculates the compatibility of formation waters of the Aptian-Albian-Cenomanian hydrogeological complex and hosted waters, and also estimates the probability of swelling of clay minerals in the reservoirs of this complex.

The plastic behavior and compression of bentonite clay under heating effect

The bentonite material is currently used in a variety of applications ranging from hydraulic barriers and waste-buffer protection to other special uses in industry and underground disposal of high-level nuclear waste. In the deep geological repository for high-level radioactive waste, the clay acting as a buffer material between the host rock and the canister is subjected to thermal load, which could impact its geotechnical properties. Thus this study is aimed at investigating the swell and compressibility of bentonite subjected to heating at 200 °C, 400 °C, and 600 °C. The impact of heating on the index properties, the swell and compression and hydraulic conductivity is explored. The change in temperature due to weather fluctuations was found to have a minor effect on physical behavior, but this effect is found to be significant when the temperature is raised to high levels in the order of 200 °C–600 °C (Celsius). The rate at which swell and hydraulic conductivity is developed is presented in this study. The result indicated an elimination of the swellable clay minerals effect in the bentonite clay upon exposure to a temperature of 600 °C. This study introduces useful information and data for modeling the behavior of bentonite when subjected to elevated temperatures for use in application for deep geological repository for high-level radioactive waste storage and other applications.

In-silico investigation of mechanical behavior of hydrated Na-montmorillonite tactoid

Swelling clay minerals, exemplified by Na-montmorillonite (Na-Mt), are vital constituents in expansive soils and hold significant relevance in geotechnical engineering. Comprehending their distinctive swelling behavior upon hydration is imperative for managing potential damage to civil infrastructure. Conversely, this swelling property gives rise to numerous advantageous applications, including using these clays in barrier materials and nanocomposites. The hierarchical structure of montmorillonite, consisting of clay mineral layers, tactoids, aggregates, and assemblies of aggregates, plays a pivotal role in the swelling behavior of expansive clays. This investigation employs molecular dynamics (MD) and steered molecular dynamic (SMD) simulations to explore the nanomechanical properties of hydrated Na-Mt tactoids at various hydration levels. It provides insights into their responses to compression, tensile, and shear deformation. This study reveals increased hydration levels increase interlayer spacing in clay structures, resulting in higher average d‐values. Water molecules drive attractive electrostatic interactions with clay mineral layers, predominantly mediated by sodium ions, highlighting the complex interplay between interlayer hydration and tactoid stability. Higher hydration enhances tactoid compressibility, reducing the stress required for deformation by compressing water molecules and clay mineral layers in the interlayer space. The study also demonstrates a notable reduction in tensile modulus with increasing hydration, signifying the significant impact of even minimal hydration on interlayer cation-clay layer interactions. Hydrated tactoids exhibit altered mechanical responses in shear deformation compared to dry ones, requiring lower shear stress to detach the top clay layer from the tactoid. The presence of water molecules impedes the locking of clay mineral layers, further influencing mechanical properties. The results and insight provided by this work will contribute to a better understanding of the impact of interlayer hydration on the stability and response of swelling clay minerals.

Inhibition of the polymer grafted with dopamine derivatives on hydration and swelling of clay

Swelling of clay minerals is one of the main factors restricting the efficient exploration and development of shale oil and gas. To solve this issue, the free radical induction method was employed to synthesize a polymer grafted with dopamine derivatives, P(AM-DA). This study aimed to evaluate the inhibitory properties of P(AM-DA) on the hydration and swelling of clay and analyze its mechanism. Firstly, P(AM-DA) was characterized by FTIR, HNMR, and TGA. Subsequently, anti-swelling, anti-disintegration, and immersion tests were conducted to evaluate its inhibitory properties. Then, the inhibitory mechanism was further elucidated through Zeta potential tests, particle size analysis, XRD tests, and SEM analysis. Finally, the properties of P(AM-DA) on mud rheology and fluid loss were evaluated. The experimental results showed that the dopamine derivatives were successfully grafted onto the polymer's side chains. Additionally, the result of TGA demonstrated the polymer's good thermal stability below 200℃. P(AM-DA) showed a superior inhibitory effect, and the swelling rate of cores was much lower than that of KCl and polyetheramine. Despite the clay mineral content of shale cuttings being as high as 51.1 %, the anti-disintegration rate could be increased by 66.45 %. The Na-BT core retained its shape and structural integrity after 72-hours immersion, and it could support a weight of 200 g. Regarding the inhibitory mechanism, P(AM-DA) could adsorb onto the surface of clay particles through hydrogen bonding and electrostatic interaction, which reduced the dispersion of clay particles. The protonated amine groups could neutralize the electronegativity of the clay particles, reducing the electrostatic repulsion between the layers. Besides, P(AM-DA) exhibited a series of special behaviors, such as adsorption on the core surface to form a homogeneous layer and insertion into the crystal layer of clay. Both of these behaviors could decrease the passage of water molecules, and the intercalation behavior could also reduce and stabilize the interlayer spacing. In addition, P(AM-DA) could dramatically increase the viscosity of the fluid at higher concentrations and unexpectedly reduce fluid loss. In conclusion, P(AM-DA) showed considerable promise in inhibiting hydration and swelling of clay.

Shale permeability and microstructural alternation during CO2 pre-fracturing: A mechanistic study

CO2 pre-fracturing technology represents a novel approach to CO2 fracturing, effectively enhancing carbon capture efficiency in shale reservoirs while increasing the recovery of hydrocarbon resources. This study systematically quantifies the impact of water injection on the pore structure and permeability of shale samples saturated with pre-injected CO2. Based on X-ray diffraction (XRD) and low-temperature nitrogen adsorption (LT-NA) results, the dominant mechanism of the swelling-chemical coupling effect in shale property is clarified. Pre-injected CO2 can effectively mitigate the impact of water absorption. After a reaction time of 7 days, the permeability of the CO2-involved hydrated shale samples is four times that of samples without CO2. Nevertheless, the influence of subsequently injected water on shale permeability persists, resulting in an 80% reduction in shale permeability. XRD and LT-NA results indicate that the swelling-chemical coupling effect is the dominant factor in shale property variation during CO2 pre-fracturing. In the initial stage, the decline in calcite and clay mineral content is significant, and chemical dissolution dominates the change in pore structure. As the reaction progresses, the intensity of chemical reactions weakens, and clay mineral swelling becomes the primary factor affecting the shale properties. In this stage, K+ generated from original minerals effectively inhibits clay mineral swelling. Therefore, the swelling-chemical coupling effects should be comprehensively considered during the CO2 pre-fracturing process, and an appropriate soaking time should be selected to maximize CO2 storage efficiency and oil and gas production.

Evaluation of drying shrinkage effects on the elastic properties of porous sandstones using a modified micromechanical model

SUMMARY The effects of pore fluids on the elastic properties of sedimentary rocks can be broadly categorized into two mechanisms: variations in pore compressibility due to the physical properties of the fluids and alterations in the stiffness of the rock frame resulting from rock–fluid interactions. Particularly, as rock–fluid interactions alter the stiffness of contacts between mineral grains, changes in the fluid properties around grain contacts can induce volumetric deformation of the rock as well as in variations of the associated elastic coefficients. Even though many previous studies have explored the influence of swelling of clay minerals, the relationships between changes in elastic moduli and deformation in rocks, which hardly contain swellable minerals, remain to date enigmatic. In this paper, to evaluate quantitatively these effects, drying rates, strains and ultrasonic velocities of small cylindrical Berea sandstone samples were measured as their water saturation was decreased by evaporative drying. The measurements clearly showed drying shrinkage and drastic increases in shear and compressional moduli for all the samples under an almost fully dried condition. Previous studies considered that the alteration in surface energy of grain minerals between wet and dry states affected the contact stiffness between them. Some of them used micromechanical model, uniting the Digby grain contact model with the effective medium theory, to interpret the changes in elastic moduli observed in the non-swellable sandstones during water adsorption on the grain surface. The conventional micromechanical model assumes that a mineral grain is a pure sphere and that the number of contacts between the grains is one. However, grains in a sedimentary rock are generally not purely spherical, and the contact surface is composed of several adhesive asperities. We therefore modified the conventional model by introducing the curvature radius and the number of asperities per contact surface. The modified model well reproduced the shear moduli under wet conditions using the strain and moduli measured under dry conditions. On the other hand, the predictions of the compressional moduli using the model were partially in agreement with the experimental results. Therefore, we attempted to qualitatively interpret the relationship by combining the model with the viscoelastic effect associated with wave-induced fluid flow. The deformation and changes in the elastic moduli of rocks resulting from multiple pore fluids within them can be better understood by the present combined model.

Rehydroxylation of calcined swellable clay minerals at ambient conditions

Thermal treatment of clay minerals is used to produce building materials like supplementary cementitious materials (SCM). New, environmentally friendly binders, that are alkali activated materials (AAM) or geopolymers can be produced with calcined clay minerals, too. Four typical reactions occur during thermal treatment of clay minerals, namely dehydration, dehydroxylation, breakdown of structure, and recrystallization of high temperature phases. Heating to temperatures below the breakdown of structure makes rehydration and rehydroxylation of the clay minerals possible, ass observed in ancient bricks and pottery. As swellable clay minerals or mixtures of different clay minerals come into focus as precursors for geopolymers or as SCM, it is important to pay attention to rehydroxylation in this context as well. This work studied the rehydration and rehydroxylation of three different homoionic (Na+, Ca2+, Mg2+) exchanged trans- and cis-vacant dioctahedral smectites at equal relative humidity (75% r.H.) at different temperatures (22, 40, and 60 °C) after calcination at 700 °C. Simultaneous thermal analysis was used to determine the amount of H2O uptake (after 4, 24, 48, 72, and 168 h) due to rehydroxylation. Rehydroxylation between 8.7% for a Na+ exchanged sample and up to 37.3% for a predominantly Mg2+ exchanged sample took place within 7 d. The process of rehydroxylation could be further verified by X-ray diffraction, these measurements should be part of future studies. The α-free isoconvertional approach resulted in Ea of rehydroxylation in the range 32–90 kJ/mol for Ca2+ exchanged samples.

Hydrogen and Metal–Ligand Bonds in Swelling of Smectite Clay Minerals

Hydrogen and Metal–Ligand Bonds in Swelling of Smectite Clay Minerals

Effectiveness of self-sealing after gas transport in Boom Clay

The study of gas transport in low permeable materials is becoming a significant focus in energy-related geotechnics, particularly for managing deep geological disposal of long-lived and heat-emitting radioactive waste. Argillaceous rocks, studied to host the disposal, may present induced fractures caused by the excavation activities that increase the permeability to liquid and gas. The generation of gases can also lead to an excessive pressure build-up in these saturated media resulting in the development or reactivation of fractures/fissures creating preferential pathways for the gas flow [1]. Nevertheless, these rocks present the advantage of self-seal (via swelling of clay minerals due to re-saturation, consolidation or creep), reducing fissure permeability and potentially restoring the barrier function [2].
 This study focuses on Boom Clay, a Cenozoic clay candidate for hosting the repository in the Belgian programme, aiming at characterising the effectiveness of its self-sealing process after gas injection/dissipation tests due to the swelling of clay minerals during re-saturation. This poorly indurated rock presents sedimentary bedding planes that can act as preferential pathways during the gas invasion. In a previous experimental campaign, samples at two bedding orientations (parallel and orthogonal to the flow) were tested under oedometer conditions [3, 4]. The results indicate that gas transport induced slight expansion of the samples in both orientations, increasing their intrinsic permeability, which suggested the opening of preferential paths. Furthermore, the analyses of the pore network using mercury intrusion porosimetry (MIP) and micro-focus X-ray computed tomography (µ-CT) confirmed the development of gas pathways following the bedding direction or interconnecting bedding planes [4, 5].
 To assess the self-sealing capacity, oedometer tests were carried out at two bedding directions using an oedometer cell with lateral stress measurement to comprehensively understand the stress state and ensure that gas flow occurred through the sample rather than between the sample-ring interface. Prior to the gas injection stage, water permeability was measured. Subsequently, a gas injection/dissipation stage was performed at constant vertical stress. Immediately after, the sample was placed in contact with synthetic water to allow re-saturation. Finally, the water permeability was measured again. The self-sealing capacity of the clay was assessed by comparing the water permeability at both stages. If the obtained values are similar, the barrier function has been restored. Some tests also included a second gas injection to evaluate the potential pathway reopening. MIP and µ-CT data allowed for evaluating microstructural changes due to these processes.
 The experimental results demonstrate that gas can flow at pressures lower than the minor lateral stress, and the computed effective gas permeability is always higher than the initial intrinsic water permeability, pointing to the opening of preferential pathways (Figure 1a). Water permeability after re-saturation showed values comparable to the initial intrinsic permeability, recovering the hydraulic barrier function thanks to the clay minerals’ swelling (Figure 1a). This indicates the good self-sealing capacity of the Boom Clay. The gas permeability calculated during a second injection/dissipation stage is slightly higher than the initial one, suggesting some memory of the previously opened path (Figure 1a). The self-sealing effect was also observed in the CT images performed under unstressed conditions after water-undrained unloading of the tested samples. The fissures detected after the gas injection (Figure 1b left) are no longer visible after re-saturation within the technique resolution (fissures > 40µm) (Figure 1b middle). However, a small proportion of large and disconnected pores were identified in CT images, likely due to some gas exsolution. Regarding the subsequent gas injection, it again led to the development of fissures following the bedding direction detected with microstructural techniques (Figure 1b right).

Comparison of adsorption ability of PAM, APAM and CPAM on Sodium-Montmorllonite surface: A molecular dynamics study

Swelling of clay minerals caused by the adsorption of water is one of the main problems encountered in oil well drilling industry during the operations of drilling with water-based fluids. Different types of chemicals can be used as inhibitor to solve the hydration of clay minerals in drilling fluids operations. So, the adsorption process of novel polymer inhibitor remained as well a complex surface phenomenon to understand. Recently, the polymer adhesion mechanism and the development of novel polymer inhibitors that can impart improved adhesion characteristics have become ultimately important to the drilling process. In this research, molecular dynamics simulations are applied to quantify and compare the adsorption density of PAM (Nonionic Polyacrylamide), APAM (Anionic Polyacrylamide) and CPAM (Cationic Polyacrylamide) on Sodium Montmorllonite (Na-MMT) Surface. And also to analyze the hydration inhibition effectiveness for solving shale swelling problem while drilling well. This work mainly explained and summarized the parameters which achieve directly the adsorption mechanism and affect the inhibition process. Including the adsorption characteristics of PAM, APAM and CPAM. The simulation results show that PAM and APAM molecules have low adsorption density on Na-MMT surface compared to CPAM molecules. PAM and APAM molecules interact more through h-bonding with their own molecules leading to a weak interaction with Na-MMT particles. CPAM molecules provide high mobility and have good attraction with Na-MMT particles through electrostatic forces, Van der Waals forces and hydrogen bonding. APAM exhibit high energy, as the distance between its molecules and MMT increase, due to high electrostatic repulsion caused by the negative charge. The adhesion of CPAM molecules affects the inhibition of Na-MMT surface hydration more than PAM and APAM.

Mechanisms of swelling inhibition and seepage promotion of weathered crust elution-deposited rare earth ore by hydroxypropyl methyl cellulose

In-situ leaching process of weathered crust elution-deposited rare earth ore (WCE-DREO) often faces problems such as poor permeability and occurrence of landslides. The main reasons are the swelling of clay minerals by water absorption and blockage of seepage channels by fine particles. This study proposed using hydroxypropyl methyl cellulose (HPMC) as a novel green swelling inhibitor with the combination of ammonium sulfate ((NH4)2SO4) as an efficient composite leaching agent. The swelling inhibition performance of HPMC on swelling inhibition was evaluated through linear swelling tests and mud ball immersion tests. The mechanisms of HPMC on swelling inhibition and seepage promotion were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Scanning electron microscopy (SEM), Surface area analysis (BET), X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA), and the contact angle, zeta potential and particle size distribution were characterized. The results indicated that HPMC showed a good performance on swelling inhibition, which improved with the increase of HPMC concentration. HPMC expels the water from the interlayer. Moreover, HPMC adsorbs onto the surface of clay minerals by hydrogen bonding to form a hydrophobic film, which can prevent the clay minerals from hydration swelling. Due to the electric neutrality property of HPMC, the electrostatic repulsion of clay minerals can be reduced. Therefore, the fine particles of the clay minerals can be bridged to form larger particles by the long carbon chain of HPMC which leads to expansion of the seepage channels as well as the improvement of the permeability of the ores. According to the column leaching tests, the novel leaching agent composed of 0.05 wt% HPMC and 2 wt% (NH4)2SO4 not only showed a good leaching capacity of rare earth, but also inhibited the swelling of clay and enhanced the seepage when comparing with traditional leaching agent ((NH4)2SO4). Developing a novel leaching agent benefits the green, safe and high-efficiency exploitation of WCE-DREO.

Effect of Potassium Salt on Swelling of Halloysite Clay Mineral during Leaching Process of Ionic Rare Earth Ore

Currently, the primary method for leaching rare earth ores is through in situ leaching. This approach involves contact between clay minerals and liquids, which can lead to the potential swelling of clay minerals with water, triggering natural disasters such as landslides. The main purpose of this study is to select the suitable anti-swelling solution for Hunan Jianghua ionic rare earth ore. According to the ore composition analysis, 88 wt% of Hunan Jianghua ionic rare earth ore is composed of halloysite clay mineral. Therefore, halloysite clay mineral is used to investigate its anti-swelling behavior in order to provide a reference for future research on the selection of raw ore swelling inhibitors. In this study, the traditional leaching agent, MgSO4 solution, was used as the solvent along with two additional compounds, CH3COOK and KCl, which were prepared in different concentrations to form a new composite swelling inhibitor solution to observe their effect on the swelling rate of halloysite clay mineral. At the same time, the seepage velocity of halloysite clay mineral with different anti-swelling solutions is studied. The results indicate that the optimal concentration in the CH3COOK + MgSO4 solution system is 0.05 mol/dm3. At this concentration, the swelling rate is 5.129%, the inhibition rate is 20.08%, and the seepage velocity rate is 12.51 × 10−3 cm/min, respectively. In KCl + MgSO4 solution, the swelling rate is 4.868%, the inhibition rate is 24.15% and the seepage velocity rate is 13.23 × 10−3 cm/min at the concentration of 0.02 mol/dm3, which is the optimum concentration. In addition, FTIR and TG studies have further demonstrated the mechanism by which these two composite bulking inhibitors inhibit the swelling of halloysite clay mineral.

Interfacial interactions controlling adsorption of metal cations on montmorillonite

Abstract Montmorillonite (Mt) is a ubiquitous swelling clay mineral and major component of soft rocks, sediments, and soils with an inherent capability to sorb metal cations. This unique feature renders Mt important for the enrichment and mobilization of environmentally important metal cations, retardation of heavy metals and radionuclide ions, the evolution of clay mineral itself, soils and sediments, and other geological processes. Understanding the interfacial interactions of Mt with metal cations at the molecular level is of fundamental importance in all these processes, but still remains elusive, due to the chemical and structural complexity of Mt surfaces and the diverse chemistries of metal cations. In this Review, we aim to provide the reader with a comprehensive overview of the adsorption modes of metal cations on basal and edge surfaces of Mt, local chemical environments of the cation binding sites, the driving forces for metal sorption, and factors influencing the dynamics of cation uptake onto Mt surfaces. Various surface complexation models [i.e., nonelectrostatic model (NEM), constant capacitance model (CCM), diffuse layer model (DLM), and triple-layer model (TLM)], advanced spectroscopic techniques (i.e., NEM, CCM, DLM, and TLM), and atomistic simulation methods (i.e., MD, DFT, and FPMD) have been used in conjunction with macroscopic adsorption experiments to gain detailed insights into the interfacial interactions of metal cations on Mt. Mt adsorbs metal cations via three independent pathways: (1) cation exchange; (2) surface complexation; and (3) nucleation and surface precipitation. The principal driving force for cation exchange is electrostatic interaction, while chemical bonding governs the two other mechanisms that depend on the basal and edge surface properties of Mt. The siloxane cavities on the tetrahedral basal plane exhibit the strongest adsorption sites for cation exchange and are greatly affected by the the degree of Al3+/Si4+ tetrahedral substitutions. At the amphoteric edge surfaces bearing hydroxyl groups, metal cations could form mono/multiden-tate surface complexes on Mt [010] and [110] edges. Ionic strength, pH, the presence of competing cations, temperature, and layer charge have been shown to affect the adsorption mechanisms and quantity of adsorbed cations. The updated information on the interfacial interactions of metal cations with Mt basal and edge surfaces presented in this review provides an improved understanding of the enrichment of metals, formation of metal ores, and natural biogeochemical cycles, as well as may promote technological and engineering applications of this important clay mineral in environmental remediation, geological repository, petroleum exploration and extraction, and extraterrestrial research.

Development and numerical implementation of a multiscale constitutive law for double-porosity swelling clayey rocks

The swelling of clayey rocks originates at different scales of the material. Clay mineral swelling is governed by two different phenomena: crystalline and osmotic swellings. In this paper, we adapt a multiscale numerical model that considers both crystalline swelling and interlayer osmotic swelling (four water layers and more) to efficiently implement it in a finite element method code. To this end, we itemize the different interactions arising in the interlayer space with respect to the disjoining pressure, and in the interparticular space considering the capillary effects. The overall model is based on the upscaling of the constitutive law from the nanoscopic scale to the macroscopic scale by adding all the different interactions that appear while upscaling. Additionally, the general model adapted in this paper can be considered as a new definition of the effective stress governing the chemo-hydromechanical behavior of clayey rocks. The numerical model is then implemented in Code_Aster software. The validation of our model is conducted by reproducing constant-volume swelling test. Simulation results for different pore size distributions demonstrate fair agreement between the experimental results and the numerical modeling in comparison with linear elasticity that overestimate the final swelling pressure compared to the model developed herein.

Effects of Ammonium Salts on Rare Earth Leaching Process of Weathered Crust Elution-Deposited Rare Earth Ores

In order to reveal the influence of ammonium salts on the rare earth leaching process of weathered crust elution-deposited rare earth ores, ammonium acetate, ammonium chloride, and ammonium sulfate were used as leaching agents. The effects of the leaching agent on the rare earth leaching efficiency and the expansion, dissolution, and transformation behavior of clay minerals in the rare earth leaching process were studied. The results showed that rare earth leaching efficiency followed the order ammonium acetate > ammonium chloride > ammonium sulfate, with values of 90.60%, 85.96%, and 84.12%, respectively. The swelling ratio of clay mineral followed the order ammonium acetate < ammonium chloride < ammonium sulfate; the clay mineral swelling ratio was 2.09% when ammonium acetate was the leaching agent. Thermogravimetric analysis showed that the interlayer water content was the lowest when ammonium acetate was used as the leaching agent. Under the conditions of different leaching agents, the clay mineral contents changed from illite and halloysite to smectite and kaolinite. When ammonium acetate was used as the leaching agent, the relative conversion of illite was 1.49%, and that of smectite was only 0.17%. SEM analysis showed that the clay minerals expanded and dissolved obviously when ammonium chloride and ammonium sulfate were used as the leaching agents. Meanwhile, the clay mineral layered structure was relatively complete when ammonium acetate was used as the leaching agent. Therefore, when ammonium acetate was used as the leaching agent, it had the least effect on the swelling, dissolution, and transformation of clay minerals. This can provide a theoretical basis for the safe production of weathered crust elution-deposited rare earth ore, and for the screening of green and efficient leaching agents.

Swelling of compacted bentonite in organic solvents: Correlation of rate and extent of swelling with solvent properties

The swelling of clay minerals within shale formations during oil and gas exploration, and within compacted bentonite barriers for radioactive waste containment, presents a number of challenges to operators. Whilst much work has been devoted to understanding the interlayer swelling properties of clay mineral crystals, significantly less has been devoted to understanding coupled pore and interlayer swelling in reactive shale/compacted clay minerals. Here we study the swelling of compacted clay mineral tablets on exposure to a range of organic solvents, selected so that the effect of key solvent properties such as dielectric constant, density, octanol-water partition coefficient, viscosity and surface tension can be correlated with the swelling observed. We use a novel non-contact swelling meter to carry out the swelling tests, allowing us to access information on rate of swelling. Short-term swelling rate showed the strongest correlation to the solvent octanol-water partition coefficient. In long term swelling, good correlation was found between total linear swelling and viscosity, and the octanol-water partition coefficient.

Investigating Different Fluids and Injection Patterns on the Effect of Reservoir Rock Quality Alteration due to Swelling and Migration of Clay Minerals at Carbonate Reservoirs

Abstract Nowadays, with the progress in technology, the demand for fossil fuels has increased. Therefore, improving the oil recovery from the current oil reservoir is among the crucial issues. Formation damage is a well-recognized subject that causes a reduction in the productivity or injectivity of an oil well. Reducing or controlling formation damage can be effective in improving oil recovery. There are various mechanisms that cause formation damage such as fine migration and clay swelling. In this study, the simultaneous effect of fine migration and swelling on the permeability of a carbonate rock was investigated. Kaolinite and smectite(bentonite) minerals were selected as the representative case for migration and swelling, respectively. Primarily, bottle tests were conducted to study the effect of different fluids on the swelling potential of the kaolinite and smectite. According to the structural feature of the kaolinite, it has the smallest cation exchange capacity (CEC) and consequently a low swelling tendency. Therefore, it showed negligible swelling in the presence of all fluids. According to the high cation concentration of the formation water (FW) and seawater (SW), smectite did not show a high swelling effect. However, diluting the FW and SW increased the swelling tendency of the bentonite. Nanoparticles were not able to control the swelling of the bentonite according to their larger size than the spacing of clay layers. Zirconium oxychloride was also utilized as the swelling inhibitor which showed high efficiency. Eventually, different injection scenarios were tried using synthetic carbonate core samples with specific clay contents, and the best injection plan for formation damage control was determined.

Flotation separation of coal dust from foundry dust enhanced by pre-soaking assisted mechanical stirring

Foundry dust is the main refractory solid waste in the foundry industry, and its resource utilization is a top priority for realizing green and cleaner production. The massive amount of coal dust in foundry dust is a potential impediment to the recycling of foundry dust, and the efficient separation of coal dust is crucial to solving the above problems. In this paper, the flotation separation of coal dust from foundry dust enhanced by pre-soaking assisted mechanical stirring was reported. The influence of pre-soaking, stirring speed, and stirring time on the flotation results of foundry dust was systematically studied, and the enhancement mechanism was analyzed based on the microstructure and hydrophobicity of foundry dust. Flotation kinetics experiments with different stirring time were conducted to clarify the flotation process of foundry dust. The results indicate that the pre-soaking of foundry dust is beneficial for the water-absorbing swelling of clay minerals coated on the surface of coal dust, and the subsequent mechanical stirring pretreatment promotes the monomer dissociation of foundry dust, which increases the contact angle of foundry dust and considerably improves the flotation results. The optimal stirring speed and stirring time were 2400 rpm and 30 min, respectively. The classical first-order model presented the highest degree of fitting with the flotation data among the five flotation kinetics models. Therefore, the pre-soaking assisted mechanical stirring is a promising method for promoting flotation separation and the complete recycling of foundry dust.