Presence Of Clay Minerals Research Articles

Effects of froth properties on dewatering of flotation products– A critical review

The presence of tenacious froth in flotation products has a detrimental effect on the downstream dewatering process, which is a challenge in processing plants of a range of commodities, such as coal, talc, molybdenum, bitumen, potash, zinc, copper and gold. The generation of tenacious froth is not only related to the properties of mineral particles but can also be affected by water salinity and the presence of clay minerals. In this article, the effects of stable froth on the dewatering of flotation products were presented. Froth properties including froth structure, froth stability and froth rheology were presented first and then recent studies on the influence of froth on dewatering process were reviewed. Finally, future directions of research to increase the dewatering efficiency of flotation products are recommended.

Modeling of hydrothermal processes of transformation of super-viscous oil of the Ekaterinovsky deposit in the presence of clay minerals

Using a set of physicochemical methods, the influence of hydrothermal effects on the composition of super-heavy oil of the Ekaterinovsky field in a carbon dioxide medium in the presence of a composition of catalysts - metals of variable valence in model experiments on clay rock-forming minerals was studied. Peculiarities of the transformation of the oil composition associated with the destruction of its high molecular weight components - resins and asphaltenes, and the formation of light saturated and aromatic hydrocarbons are revealed. Changes in the structural-group composition indicate an increase in the aromaticity of the products of the experiments. The greatest changes occur in the composition of resins and asphaltenes, which is reflected in a change in their structural-group composition and their paramagnetic properties. The high sorption ability of the rock to metals included in the composition of the used catalyst composition was revealed.

Impact of Mine Panel Size on Hydraulic Permeability of Weakly Cemented Strata

The effect of underground coal mining on groundwater, ranging from minimal to severe depending on the mined-out panel size, is primarily associated with the change in ground hydraulic permeability. This paper presents a novel panel design method, taking consideration of reducing water loss during the mining operation, which is based on evaluating and ranking the impact of panel size on the hydraulic permeability of weakly cemented strata. The permeability test results of weakly cemented rock samples collected in the Yili No.4 Coal Mine in Xinjiang, China strongly indicates that, in contrast to common rock, their post-peak permeability during the total stress–strain process is lower than the initial permeability due to high porosity and the presence of clay minerals. A numerical modeling based on strain–permeability functions reveals that the post-mining permeability distribution in the weakly cemented overlying strata could be subdivided into three zones: the permeability reduction zone, the permeability restoring zone, and the permeability high-increment zone. The impact significance of different size factors on the post-mining permeability of overlying strata can be ranked in decreasing order as follows: mining height, panel width, and panel length, the quantification of which was based on the variance analysis of such indices as maximum pore pressure and maximum flow velocity. Based on the above findings, the optimal size of panel 21103 in the Yili No.4 Coal Mine was determined and validated by water level field observations.

Zeta potential of cation-treated soils and its implication on unfrozen water mobility

Most frozen soils contain unfrozen water – water that remains liquid at subfreezing temperatures – which affects a frozen soil's strength and contributes to frost heave. Among the variables that influence the flow of unfrozen water through a freezing soil is the presence of clay minerals and their adsorbed cations. Zeta potential (ζp) is one measure of clay mineral surface properties that may provide insight into the interaction of mineral surfaces with unfrozen water films; however, one gap in the literature is the lack of ζp measurements at subfreezing temperatures. The purpose of this research was to measure the ζp of six cation-treated soils as a function of temperature, including measurements at a subfreezing temperature. The results indicate that the magnitude of the ζp decreases as a function of temperature. The ζp of the divalent cation-treated clays generally had a smaller magnitude and was less sensitive to temperature than the monovalent cation treatments, suggesting that unfrozen water mobility (and thus frost heave) may be correlated with smaller ζp. Based on these results, it is hypothesized that the amounts of immobile unfrozen water may depend on the ζp at the shear plane. To complement the results of this research, we recommend additional tests to determine the viscosity of unfrozen water as a function of temperature.

An insight into pore-network models of high-temperature heat-treated sandstones using computed tomography

The pore network attributes help assess the fluid-flow behaviour in various reservoir rocks. As, in the cases of various unconventional energy exploration, the reservoir rocks are being exposed to different sets of temperatures that result in microstructural alteration in the pore and throat scale. Since the last decade, X-ray computed tomography (XCT) has been proved to be a useful tool in determining the micro-scale pore structures. However, such results are greatly influenced by the structure of the rocks, pore spaces, grain size, and nature of minerals. Here in this study, an attempt has been made to investigate the microstructural alteration and pore-network configuration of thermally-treated three Indian sandstones (Dholpur sandstone, Jodhpur sandstone and Gondwana sandstone) of varying mineralogy using the high-resolution micro-CT techniques. Microstructural modifications, the evolution of pores spaces, pore-size distribution, pore-network attributes such as nature of connectivity, pore radius, pore-volume, pore coordination number, throat radius and throat channel lengths of the three sandstones were investigated in a temperature range from 25 °C to 800 °C. The microstructural responses of these sandstones in terms of pore-space evolution and pore network models were found to be dependent on the presence of clay minerals. The overall trend of porosity for Dholpur and Gondwana sandstone was found to increase as a function of temperature. For Jodhpur sandstone, the maximum porosity was achieved at 600 °C and thereafter a decreasing trend up to 800 °C. Gondwana sandstone, most clay-rich, was found to be most vulnerable to elevated temperatures compared to the other two sandstones. The maximum average pore coordination number for Dholpur and Jodhpur sandstone was observed at 600 °C (7.097) and 800 °C (6.953), respectively.

High contribution of hydrocarbon transformation during the removal of polycyclic aromatic hydrocarbons from soils, humin and clay by thermal treatment at 100–200 °C

Polycyclic aromatic hydrocarbons (PAHs) are major pollutants in air, soils and sediments. PAH-polluted soils can be cleaned rapidly by thermal treatment. PAH volatilization is considered as the main process explaining PAH removal at low temperature, yet other processes may occur. Particularly, we hypothesize that thermal transformation can also explain PAH removal, where transformation refers to both degradation and formation of bound PAHs. We thus studied the removal of spiked benzo[a]pyrene at 0.5 mg/g in bauxite soil, fluvo-aquic soil, chernozem soil, montmorillonite, humin, and quartz sand as control, from 100 to 200 °C. We measured concentrations of benzo[a]pyrene in the volatilized fraction and solid residues by high-performance liquid chromatography. We identified transformation products by gas chromatography–mass spectrometry. Results show that the contribution of thermal transformation to the removal of benzo[a]pyrene increased from 24.7 to 58.4 wt% for bauxite soil, from 4.4 to 38.2 wt% for fluvo-aquic soil, and from 11.5 to 35.9 wt% for chernozem soil, with temperature increasing from 100 to 200 °C. Transformation such as oxidation occurred in all samples except in benzo[a]pyrene-spiked quartz sands. Transformation of benzo[a]pyrene was thus partly explained by the presence of clay minerals, as evidenced for the montmorillonite assay where transformation contributed 74.6 wt% to the total removal of benzo[a]pyrene at 200 °C. Overall, our findings demonstrate a major overlooked contribution of transformation to PAH removal at low temperature.

The role of clay surfaces in the heterogeneous nucleation of calcite: Molecular dynamics simulations of cluster formation and attachment

In many environments calcium carbonate minerals precipitate in the presence of clay minerals, and observations suggest that clays, particularly smectites, facilitate carbonate formation. In order to understand the interactions between clay surfaces and carbonate-precipitating solutions, we built model aqueous solutions of various compositions (containing Ca2+, Mg2+ and CO32– ions) between layers of clay minerals (montmorillonite and kaolinite), and performed extensive molecular dynamics simulations. The results were compared with simulations for bulk solutions. Contrary to intuition, ionic clusters formed preferentially in the interlayer solution (instead of on the clay surface). The clusters grew both by the association of individual ions and aggregation, and were adsorbed to the clay surfaces with distinctly different efficiencies in the various systems. Montmorillonite was found to be more efficient than kaolinite in capturing clusters from solution. However, the efficiency of anchoring ionic clusters to the clay surfaces strongly depended on the Na+ concentration of the solution, since Na+ appeared to strongly attach to the surface and thereby block it from clusters in the solution. Montmorillonite (and probably other smectite clays as well) may thus have an important role in certain, primarily freshwater, systems in the localization of ionic clusters on its surface, thereby promoting the nucleation and templated growth of crystalline calcium‑magnesium carbonate minerals.

Pedogenesis in a karst environment in the Cerrado biome, northern Brazil

Karst terrains in tropical regions are object of few studies on soil properties and pedogenesis. In this study, soils pedogenesis was evaluated in a karst environment in the Cerrado biome, northern region of Brazil. The assumption is that even in the Cerrado conditions the characteristics of the soils are similar to other limestone soils in arid and semi-arid climates. Six soil profiles along a toposequence were sampled in trenches located at the summit (P1), shoulder (P2), backslope (P3), footslope (P4) and toeslope (P5 and P6) positions. The profiles were described, and their morphological (macromorphology and micromorphology), physical, chemical, mineralogical and organic matter attributes analyzed. The soils were classified as Calcic Luvisol (P1), Calcaric Eutric Cambisol (P2), Haplic Kastanozem (P3), Calcic Pellic Vertisol (P4), Orthofluvic Gleyic Calcaric Eutric Fluvisol (P5), Orthofluvic Calcaric Eutric Fluvisol (P6). Melanization and calcification are the main pedogenic processes, and they are controlled by the nature of parent material and the landscape position of the soil profile. The profiles P1, P2 and P3, at footslope and toeslope, show higher values of weathering ratios, which indicates the presence of clay minerals with a higher SiO2/Al2O3 ratio. They also have the highest amounts of CaCO3 which are associated with precipitation and neoformation of calcite. Although soils in the Cerrado biome are mostly highly weathered and with low natural fertility, the soils in the study area show accumulation of carbonates, high levels of exchangeable calcium and magnesium, pH values and base saturation that are associated with specific pedo-environments. The combination of the soil forming factors parent material and karst terrain controlled the dynamics of carbonates, leading to their accumulation in soils, regardless of the regional climatic conditions of the Cerrado biome.

Weathering behaviour of road aggregate of andesitic composition in a New Zealand quarry

The process of weathering progressively affects the characteristics of geomaterials. Despite prior assertions, this process may happen in a relatively short time and can cause ageing and deterioration of the structure of aggregates. This study investigates the effect of natural weathering processes on characteristics of road materials, exposed within a quarry that produces road materials compliant with New Zealand specifications for premium base course material. While not an exact replica of in-use weathering conditions, this case study serves as an observable analogue, recording the chemical and mineralogical degradation of andesite aggregate materials. The variations in chemical and physical properties of roading materials of andesitic composition were investigated using image processing and a variety of analytical methods, including thin section petrography, X-Ray Fluorescence (XRF), and X-ray Diffraction (XRD). Whilst initially there was almost no obvious sign of weathering in fresh materials, within a short time-frame (less than 15 years) intense weathering was evident. The immediate loss of bases (notably alkalies) is the primary chemical trend in the natural weathering, although the rate of loss appears to decrease with time. It is consistent with the results of chemical indices of weathering, including Chemical Index of Weathering and Alteration (CIW and CIA), Weathering Index of Parker (WIP), Plagioclase Index of alteration (PIA), and A-CN-K diagram. Furthermore, XRD analysis revealed the presence of clay minerals in the weathered materials, with kaolinite and smectites the product of relatively short-term of weathering. Thin-section petrography indicates that the original textural features of the andesites were significantly changed during weathering. The results suggested that the grain size and zonation of primary minerals are critical controls in the weathering process and glass and plagioclase phenocryst are the least stable mineral phases in the examined andesitic aggregate materials.

Surface precipitation of Mn2+ on clay minerals enhances Cd2+ sorption under anoxic conditions.

The influence of Mn2+ on the sorption of metal(loid)s onto clay minerals is still unclear despite its relevance in suboxic and anoxic environments which often exhibit elevated dissolved Mn2+ concentrations. In this study, the effects of Mn2+ on Cd2+ sorption to two types of clay minerals, a well-crystalline natural kaolinite (KGa-1b) and a synthetic montmorillonite (Syn-1), were investigated. Batch experiments on Mn2+ and Cd2+ sorption to Ca-saturated KGa-1b and Syn-1 were conducted under anoxic conditions. At low Mn2+ and Cd2+ concentrations (1 and 5 µM), both metals exhibited similar affinity for sorption to the clays, suggesting that elevated Mn2+ concentrations might effectively decrease Cd2+ sorption as predicted using a three-plane surface complexation model. However, competitive Mn-Cd experiments at higher concentrations (≥50 µM) revealed that for both clay minerals, the presence of Mn2+ increased Cd2+ sorption to the solid phases. Although solutions were undersaturated with respect to known Mn(ii) solid phases, analysis using X-ray absorption spectroscopy (XAS) evidenced the formation of Mn(ii)-containing solid phases which can specifically adsorb or incorporate Cd2+. This process, which was mediated by the presence of clay minerals, overcompensated the decrease in Cd2+ adsorption to clay surfaces due to competition with Mn2+. We conclude that, contrary to predictions based on a competitive surface complexation model, elevated Mn2+ concentrations can contribute to decrease dissolved Cd2+ concentrations in anoxic clay-containing environments, such as contaminated sediments or flooded paddy soils.

In vitro antibacterial activities of selected TB drugs in the presence of clay minerals against multidrug-resistant strain of Mycobacterium smegmatis

Healing clay is a rich source of diverse minerals. The relevance of these indigenous minerals in the improvement of antibiotic chemotherapy against prevailing bacterial pathogens is yet to be thoro...

New Chemical Treatment for Permanent Removal of Condensate Banking from Different Gas Reservoirs.

Condensate banking represents a challenging problem in producing the hydrocarbon from tight gas reservoirs. The accumulation of liquid condensates around the production well can significantly impair the gas flow rate. Gas injection and hydraulic fracturing are the common techniques used to avoid the condensate development by maintaining the reservoir pressure above the dew point curve. However, these treatments are associated with high operational costs and large initial investment. This study presents a new chemical treatment for removing the condensate banking using thermochemical solutions. The presented treatment can cause a permanent impact on the treated formations. Chemicals are injected to react downhole and generate in situ pressure and heat in certain conditions. The generated pressure can raise the gas pressure above the dew point, and the generated heat can change the phase of the liquid condensate to gas. Kinetic analysis indicates that thermochemical fluids can increase the temperature and heat by 85 °C and 369 kJ/mol, respectively. In addition, the impact of clay content on the efficiency of thermochemical treatment was studied using coreflooding experiments. A condensate removal of more than 60% was achieved using the huff and puff injection mode. A good correlation between the rock permeability and the condensate removal efficiency was observed. Higher condensate removal was obtained for the rock samples with high permeability values. Moreover, the presence of clay minerals in the treated rock showed a minor impact on the condensate removal, indicating that the injected chemicals are able to stabilize the clay minerals and avoid clay damage. This research shows that thermochemical treatment can remove more than 60% of the condensate damage for different types of tight sandstones. Huff and puff treatment was found to be a very practical approach to diminish the condensate banking from different sandstone rocks. Also, this work confirms that thermochemical treatment can be applied in the clayey formation for removing the condensate blockage without affecting the clay stability or inducing clay damage. Ultimately, this study introduces a new chemical treatment in the gas industry, and the used chemicals are effective, environmentally friendly, and not expensive.

Implications of basement rock alteration in the Nankai Trough, Japan for subduction megathrust slip behavior

The Nankai Trough is an exceptionally well-studied convergent margin known to host damaging megathrust earthquakes as well as various forms of slow fault slip. Outcrop studies of exhumed analogues for the modern subduction thrust, as well as seismic reflection images of the active subduction zone, suggest that the basaltic basement participates in plate-boundary shearing at depths of a few km and greater. We obtained altered basaltic upper basement from the modern Nankai Trough seaward of the trench, recovered by drilling on IODP Expedition 333. We performed laboratory friction experiments on bare surfaces and gouge powders of this material, in addition to and in combination with other materials for comparison. The altered basalt exhibits predominantly velocity-strengthening frictional behavior, indicating a tendency for stable slip. For bare surface experiments, few instances of velocity-weakening friction occur and are restricted to slip rates of <10−6 m/s. Thin sections and XRD analyses of the starting material indicate that the velocity-strengthening behavior is likely associated with the presence of clay minerals, mostly Mg-smectite, which coat the rims of larger, stronger grains. Based our friction data, we suggest that in addition to creep the altered Nankai basalts may also allow the possibility of slow slip events for two reasons: (1) velocity-weakening friction may be expected at low slip rates, but velocity-strengthening at higher rates will damp any potential slip instabilities; and (2) based on a critical stiffness criterion for accelerating (stable) slip, SSEs are capable of nucleating in the altered Nankai basalt despite velocity-strengthening friction. In light of these observations, and given the depth at which altered basement appears to be incorporated along the plate interface, we raise the possibility that some shallow slow slip events in the Nankai accretionary prism could originate from shearing in altered basalt.

Experimental clues for detecting biosignatures on Mars

Forthcoming exploration of Mars aims at identifying fossil biosignatures within ancient clay-rich formations. The subsurface of Mars has mostly acted as a giant freezer for the last 4 Gyr, thereby preserving potential remains of martian life. Yet, volcanism and impactors have periodically triggered the circulation of hydrothermal fluids, inevitably causing alteration of potentially fossilised biogenic organic materials. It thus appears crucial to quantify the impact of hydrothermal processes on organic biogeochemical signals in the presence of clay minerals. Here, we submitted RNA to hydrothermal conditions in the presence of Mg-smectites. Results show heterogeneous organo-mineral residues, with sub-micrometric phosphates, carbonates and amorphous silica particles together with Mg-smectites with interlayer spaces saturated by N-rich organic compounds. Although the chemical structure of RNA did not withstand hydrothermal conditions, clay minerals efficiently trapped organic carbon, confirming the relevance of drilling for organic carbon in ancient martian sediments. In addition, the degradation of RNA in the presence of Mg-smectites led to the precipitation of a quite uncommon mineral assemblage that could be seen as a biosignature per se. Martian targets exhibiting this mineral assemblage will thus constitute high priority and highly relevant candidates for sample return.

Formation of adenosine from adenine and ribose under conditions of repeated wetting and drying in the presence of clay minerals

Ribonucleic acid (RNA) was possibly the most important biopolymer in Earth’s early existence. However, the prebiotic synthesis of the nucleoside component of RNA is problematic. Here we report the formation of adenosine by subjecting a mixture of adenine and ribose to repeated wetting and drying from 40 to 80 °C in air, with or without the addition of clay minerals. Using liquid chromatography-mass spectrometry (LCMS) and 1H NMR spectroscopy, we were able to detect the formation of adenosine in the presence of kaolinite and Mg2+-exchanged montmorillonite at 70 °C. At this temperature adenosine was also formed in the absence of these minerals but none was detected in the presence of the raw (sodium-rich) montmorillonite. In all instances, only small amounts of adenosine were formed. On the other hand, a 12–13% yield of adenosine was measured in the presence of kaolinite at 60–80 °C, using the highly sensitive method of liquid chromatography coupled with tandem mass spectrometry (LCMS/MS). Kaolinite can apparently act as both a concentrating surface and a catalyst in the formation of adenosine from adenine and ribose although the underlying mechanism has yet to be established. The mild experimental conditions used here for nucleoside formation could plausibly obtain in some parts of the prebiotic Earth.

The influence of soil texture on the course of volume changes of soil

Volume changes of soil associated with soil moisture changes are caused by the presence of clay minerals from illite and montmorillonite groups. Clay minerals are found in the so-called clay soil component which can be quantified by laboratory analysis of the soil particle-size distribution. Consequently, the potential for volume changes in soil can be assessed from soil texture. In our study, 172 soil samples with different textures were used to measure dependencies between volume changes in soil and changes in soil moisture under laboratory conditions. The samples were collected from 11 sites in the Eastern Slovak Lowland. On the basis of the measurements, 10 mathematical models were created to compute the correlation between volume changes of soil and soil moisture content and texture. The highest accuracy was obtained with the model which assumes the content of particles &amp;lt; 0.002 mm. When comparing the clay particles &amp;lt; 0.001 mm (colloidal clay) with the particles &amp;lt; 0.002 mm (colloidal + physical clay) it was also found that the particles &amp;lt; 0.002 mm have a larger impact on the volume changes of soil than the particles &amp;lt; 0.001. The inclusion of particles &amp;gt; 0.002 mm (silt + sand) into the models resulted in either no or only negligible refinement of the soil volume change calculations.

Strontium (87Sr/86Sr) isotopes: A tracer for geochemical processes in mineralogically-complex mine wastes

Interpretation of geochemical data based primarily on elemental concentrations often lead to ambiguous results due to multiple potential sources including mineral weathering, atmospheric input, biological cycling, mineral precipitation and exchange processes. The 87Sr/86Sr ratio is however not fractionated by these processes. In this study, Sr isotope (87Sr/86Sr) ratios have been coupled with chemical data of Sr and Rb-bearing minerals, tailings and leachates (water-soluble) to gain insight into the geochemical processes occurring within the Yxsjöberg Cu-W mine tailings, Sweden. The tailings have been exposed to oxidizing conditions resulting in three geochemical zones namely (i) oxidized, (ii) transition and (iii) unoxidized zones. Leachates from the oxidized zone are acidic (pH = 3.6–4.5) and contain elevated concentrations of metals (e.g. Fe, Cu and Zn) and SO4. The low pH has also led to subsequent weathering of most silicates, releasing Al, Ca, Mg and Na into solution. The 87Sr/86Sr ratio in the tailings ranges from 0.84787 to 1.26640 in the oxidized zone, 0.92660–1.06788 in the transition zone, whilst the unoxidized zone has values between 0.76452 and 1.05169. For the leachates, the 87Sr/86Sr ratio ranges from 2.44479 to 5.87552 in the oxidized zone, 1.37404–1.68844 in the transition zone and 1.03697–2.16340 in the unoxidized zone. Mixing (between mineral weathering and atmospheric sources) was identified as the major process regulating the Sr composition of the tailings and leachates. The highly radiogenic signatures of the leachates in the oxidized zone suggests weathering of biotite, K-feldspar and muscovite. Despite the very radiogenic signatures in the oxidized zone, increments in Ca/K ratios, Be, Ce, Tl, Al, Fe and SO4 concentrations in the water-soluble phase were recorded in its lower parts which suggests the dissolution of amphibole, pyroxene, plagioclase, fluorite, gypsum, Al and Fe –(oxy) hydroxides as well as cation exchange by clay minerals. Presence of clay minerals has led to the partial retainment of radiogenic 87Sr/86Sr resulting in increased 87Sr/86Sr in the solid tailings material at these depths. The 87Sr/86Sr ratios of the water-soluble phase in the transition zone is similar to that of helvine and could indicate its dissolution. In the upper part of the unoxidized zone, the 87Sr/86Sr ratios and trends of Be, Ca, SO4, Tl and Zn in the water-soluble phase suggest the dissolution of gypsum which precipitated from a leachate with the isotopic signature of helvine. In the lower part of the unoxidized zone, elevated concentrations of W were recorded suggesting scheelite weathering. But the 87Sr/86Sr ratios are higher than that expected from dissolution of scheelite and indicates additional processes. Possible sources include biotite weathering and groundwater. This study reveals that when interpreting geochemical processes in mine waste environments, 87Sr/86Sr should be considered in addition to chemical constituents, as this isotopic tracer offers better insights into discriminating between different solute sources.

Mineral Tanah sebagai Indikator Stabilitas Tanah pada Daerah Berlereng: Studi Kasus Tombolopao Kabupaten Gowa

Soil forming process can influence soil stability, especially on a sloping area, which is currently related to landslides. This research aims to study mineral content in the soil as an indicator to evaluate soil stability in slope area. Soil texture analyzed with hydrometer and soil mineral analyzed with Kerr method. Soil parent rock comes from Tpbv (Tertiary Pliocene Baturape Volcanic) Formation that consists of lava, breccia, tuff, and conglomerate. Soil texture in A horizon dominated with silty clay loam and in B horizon with silty clay. Clay content in A horizon to B horizon increase ranges from 2-6%. Soils mineral have been weathering on the physical and chemical, which caused cracking on minerals lattice and formed clay minerals inside it. The presence of clay minerals between soil mineral particles can cause mutual repulsion force and cause friction particles that triggering the movement of particles in a small scale when soil saturated by water and triggers soil movement (landslide).

Interaction study of clay-bearing amphibolite–crude oil–saline water: Molecular level implications for enhanced oil recovery during low saline water flooding

Low saline water flooding (LSWF) had proved to be an efficient method for enhanced oil recovery in clay-bearing hydrocarbon reservoirs, but the interaction mechanisms among in-situ rocks – fluids and injection fluids within the reservoir – are not yet known properly. Understanding the molecular level interaction among these components is critical for designing and field scale implementation of LSWF in clay-bearing crystalline reservoir rocks, which is very limited in the existing literature. A weathered amphibolite rock and one dead crude oil from the Bakrol field (Cambay basin, India) have been used in this study. The presence of clay minerals in the weathered amphibolite rock was observed using a polarising microscope and characterised by the X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques. The crude oil and its fractionated SARA components have been extensively studied by spectroscopic techniques for their characterisation. The interaction study among the rock powder, hydrocarbon crude oil and saline water has been performed in the present work for gaining better insight for designing the injection fluid for LSWF. The weathered amphibolite rock powder was mixed with the dead crude oil and kept for 30 days in room temperature (T) and pressure (P) for proper interaction. The XRD, FTIR and cation exchange capacity results clearly demonstrated the incorporation of crude oil components in the interlayer surfaces of clay minerals. The oil removal efficiency, from the oil-treated rock powder of three saline water samples having NaCl concentration of 3000, 5000 and 8000 ppm, was investigated using the UV–Vis and fluorescence spectroscopies. The low saline NaCl water is capable of removing the maximum amount of polar components from the oil-treated rock powder. These molecular level insights are valuable for designing effective injection fluid for enhancing the oil recovery from the clay-rich crystalline reservoir rock.

Mineralogical, Petrographic, and Physical Investigations on Fossiliferous Middle Jurassic Sandstones from Central Sardinia (Italy) to Define Their Alteration and Experimental Consolidation

In the present work, the mineralogical-petrographic and physical features of Middle Jurassic sandstones with macrofossil plant remains belonging to the Domenico Lovisato collection, housed at the Geological and Palaeontological Museum of the Cagliari University (Sardinia, Italy), have been studied to define the alteration processes and the consolidating treatment. These sandstones, coming from the Genna Selole formation (central Sardinia), show evident problems of physical decay, due to petrophysical and compositional characteristics such as high porosity, low cementing degree, and presence of clay minerals (e.g., phyllosilicates). This latter leads to subsequent cyclic mechanisms of hydration/dehydration, which affect these sedimentary rocks. For this purpose, five main different sandstone specimens with evident crystalline matrix decohesion have been selected and analyzed. To define their mineralogical-petrographic (composition, microstructure) and physical characteristics (real and bulk densities, helium porosity, water absorption, mechanical strength, etc.), the optical microscope (OM) in polarized light, X-ray powder diffraction analysis (XRPD), helium and water pycnometer, and point load test were used. Testing the most suitable and compatible products for consolidation and time-saving of the palaeobotanical remains, several experimental treatment tests have been performed using four chemical products (i.e., alkoxysilane ethyl silicates and Na/K-silicate).