Kaolinite Powder Research Articles

Cementitious properties of coal-based metakaolin prepared from coal gangue via Fe3O4-Assisted microwave activation

Coal gangue is the largest emission of solid waste in the coal industry, and its large accumulation has posed serious hazards to environment. Low-quality coal gangue can be transformed into an auxiliary cementing material (coal-based metakaolin) with pozzolanic activity after calcination. However, the conventional calcination has slow heating rate, high energy consumption and serious pollution issues. Therefore, the fast and efficient calcination of coal gangue must be explored. In this study, coal series kaolinite (coal gangue with a kaolinite content of more than 80%) from Inner Mongolia was calcined by Fe3O4-assisted microwave calcination craft to prepare coal-based metakaolin (CBM). Results indicated that the efficiency of the microwave calcination of coal series kaolinite powder (CSKP) was considerably increased by adding analytical-grade Fe3O4 to CSKP. After substituting 30% of cement with CBM prepared by Fe3O4-assisted microwave calcination of CSKP to prepare cement–coal based metakaolin mortar (CCBMM), the mortar specimen made of CBM prepared at 675 °C showed the highest compressive strength (61.3 MPa) and activity index (112%). The analytical-grade Fe3O4 particles in CSKP will form spherical hematite microparticles (Fe2O3) with good dispersion after microwave calcination at appropriate temperatures (650 °C and 675 °C), which acted as microaggregates to optimize the pore structure of CCBMM, thereby enhancing the strength of CCBMM. The findings of this study confirmed that analytical-grade Fe3O4 addition not only increased the efficiency of preparing CBM by microwave calcination and reduced energy consumption, but also improved the cementitious performance of CBM.

The effects of mechanical activation on corrosion resistance of cordierite ceramics

The corrosion degrees of produced non-activated and activated cordierite-based ceramics were investigated in hydrochloric and sulfuric acid solutions. The composition of talc, alumina, and kaolinite powders was mechanically activated in a planetary mill. The concentrations of aluminum, magnesium, silicon, calcium, and potassium leached to the acid solutions from non-activated and activated cordierites were measured using ICP-OES. The amorphization of the structures was examined by XRD analysis. As a result, it has been determined that activated cordierite-based ceramics are more durable, and sulfuric acid solution causes more corrosion than hydrochloric acid.

Principal slip zone in kaolinite gouge: A seismic slip indicator?

Some fault gouges (e.g., kaolinite) exhibit velocity-strengthening behavior and slide stably at low, subseismic slip rates (e.g., 1–10 μm/s), accompanied by the preferential development of foliation rather than a principal slip zone or a discrete narrow band of large shear strain. However, a remarkable observation from experimental gouges sheared at seismic slip rates (>0.1 m/s) is that all the gouges show a well-developed principal slip zone, irrespective of their frictional behaviors (velocity weakening or velocity strengthening) at subseismic slip rates. These observations imply that in some gouges, a principal slip zone develops only at seismic slip rates and can be used as a seismic slip indicator. To test this idea, we conducted shear tests on dry kaolinite powder and wet kaolinite paste at low (0.1–100 μm/s), intermediate (∼1 mm/s), and high (1 m/s) slip rates and at a normal stress of 3 MPa. The dry powder specimen recovered after the experiments showed a principal slip zone at all slip rates. In contrast, the paste specimens showed a principal slip zone only at the seismic slip rate. They display foliation and R-shears at low and intermediate slip rates, indicating the occurrence of distributed shear. The microstructure of the wet paste at the seismic slip rate is similar to that reported from a natural kaolinite-rich seismic slip zone. Considering the experimental results, the structures of the experimental and natural seismic slip zones, and the unlikely fault slip under dry conditions, we suggest that kaolinite gouges with principal slip zone(s) can be a seismic slip indicator. Further studies may be extended to other gouge materials showing similar velocity strengthening and stable sliding at subseismic slip rates to determine whether the same conclusion can be drawn.

A transparent kaolinite-loaded zinc oxide nanocomposite sunscreen with UV shielding rate over 99% based on bidirectional dispersion

Nano-sized TiO2 and ZnO are the most efficient and widely used inorganic sunscreen, but they still have some drawbacks including agglomeration, delamination, clogging pores and high cost. In this study, a kaolinite-loaded zinc oxide nanocomposite sunscreen was prepared and the key technical problems in application of inorganic nano-sized sunscreens was solved. The synthesized kaolinite-loaded zinc oxide nanocomposite was characterized by XRD, SEM, EDS, XRF and UV–vis spectrophotometry. The SEM image of the nanocomposite suggests that agglomeration of nano-ZnO is avoided by bidirectional dispersion of superfine kaolinite powder and nano-ZnO. Nano-effect and UV shielding rate are enhanced and the nanocomposite sunscreen possesses UV shielding efficiency of 1 + 1 > 2. The UV shielding rate of the nanocomposite sunscreen is greater than 99%, only 10% addition of it endows ordinary skin care products with excellent UV protective efficacy. Moreover, the content of nano-ZnO is reduced by half through introduction of kaolinite, the cost of the sunscreen is lowered, delamination and pore clogging are avoided. This work provides a technical approach for producing stronger, safer and more economical popularized anti-UV skincare products.

Feasibility of Using Green Laser in Monitoring Local Scour around Bridge Pier

Scour around bridge piers is considered as one of the major factors which causes failure of bridges in the United States. An undetected scour can affect the stability of the bridge, eventually leading to the collapse of the bridge. The experimental investigation of scour around a pier using a non-contact measuring method is carried out in this research. A green laser-based non-contact ranging technique is performed on a prefabricated scour hole to study the factors influencing the ability to reconstruct the shape of a scour hole. The experiment was conducted in a 10 ft diameter pool and Leica scan station II was used for the scanning of the scour hole. The turbidity of the water was changed by adding Kaolinite powder to the water. The turbidity was varied from 1.2 NTU to 20.8 NTU by adding Kaolinite. The lab experiments involved changing the turbidity of water to simulate real world conditions. The results from the experimental study show that the turbidity of the water has a direct dependence on the efficiency of the green laser to map the underwater scour profile. The ability of the green laser to capture the fabricated scour hole and pool bed topography were decreased as the turbidity was increased even when the water depth of the pool was reduced. The results from the study show that the green laser is effective in underwater scanning and can be also used for bathymetry profiling and the detection of underwater objects. The method of underwater scanning using a green laser for detecting scour around bridge pier is safe, efficient, and economical.

Development of high strength, porous mullite ceramic hollow fiber membrane for treatment of oily wastewater

Ceramic hollow fiber membranes (CHFMs) are known for their excellent characteristics including high surface area, compact design, and good chemical, thermal, and mechanical stabilities. Despite these interesting attributes, CHFMs are also prone to certain limitations, such as brittleness and high cost that hinder them from being commercialized. To mitigate this drawback, we have developed a high strength, porous ceramic hollow fiber membrane, derived from mullite–kaolinite powder, for efficient oil–wastewater separation. The superhydrophilic, low-cost mullite-based (CHFM) was successfully fabricated through combined phase inversion and sintering techniques. Prior to the fabrication, the as-received mullite–kaolinite was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analyses. Subsequently, operational parameters such as the effect of mullite content, sintering temperature, and air gap were optimized during the fabrication of mullite ceramic hollow fiber membrane. The resulting membranes were systematically characterized and evaluated in terms of morphology, porosity, mechanical strength, water flux, and oil–water separation. Increasing the mullite content, air gap, and sintering temperature enhanced the formation of microvoid structure. It is interesting to note that the mechanical strength of 86 MPa was obtained for the membrane containing 60 wt % of mullite sintered at 1450 °C and an air gap of 5 cm. The membrane induced a stable permeate water flux and oil rejection of mullite CHFM of 182 L/m2∙h and 97.1%, respectively. As compared to kaolin ceramic counterparts, this porous mullite ceramic hollow fiber membrane can be used in various water treatment applications, including for the separation of oily wastewater due to its mechanical strength and water flux.

The kinetics of radical formation on mechanically activated kaolinite surfaces

Kaolinite is a versatile material with many applications in various fields such as in cosmetics or wastewater treatment. Here, we report the first evaluation of mechanoradicals formation on activated kaolinite powders, and its kinetics, via wet-grinding in ethanol using a free-radical scavenger (2,2-diphenyl-1-picrylhydrazyl; DPPH). Increasing the duration of ball milling of two reference kaolinite samples resulted in increased DPPH consumption due to an increase in the surface area of the processed powders. The correlation between the increasing rates of the surface areas and DPPH consumption yielded information on the density of radical species that may react with ethanol to form H radicals on the newly created surfaces of the kaolinite powders. The radical density was much lower than that reported previously for quartz, possibly due to the anisotropic nature of the kaolinite crystal structure. The actual surfaces that take part in the radical formation reaction were mainly newly created edge surfaces rather than basal surfaces. The kaolinite sample with fewer defects was more resistant to delamination, and thus its edge-to-basal surface-area ratio was also higher, which may have resulted in higher reactivity during mechanical processing. This knowledge is key for industrial applications of processed kaolinite powders.

Impact and Flexural Strength of Kaolinite / Glass Fibers Reinforced Heat-Cured Acrylic Denture

Nowadays, most materials used to manufacture denture base are heat-cured PMMA, to overcome the low strength of this material, different methods were used to strengthen the denture base and enhanced their properties. This study investigated the effect of glass fiber woven powder kaolinite (Al2Si2O5 (OH) 4) to influence and strength of flexure. Acrylic and kaolinite powders were mixed together and mixed again with acrylic liquid to prepare hybrid composite samples. Woven glass fiber composite was prepared by inserting woven glass fiber between the two halves of the dough. PMMA reinforced by (0, 20) wt% of woven glass fibers or/and (0, 2, 5, 7) wt% of kaolinite powder to prepare eight experimental groups (n= 7). The fractured surface was an evaluation by scanning electron microscope (SEM). X-ray diffraction and Fourier transforminfrared spectra FTIR tests were used to examine kaolinite powder. Samples were tested with the use of a Charpy testing machine for impact test and Instron tensile testing machine for flexural test after storage in water for 10 days at 37 °C. The results showed woven glass fibers with clay powder together significantly increased the mechanical properties of PMMA.

Effects of bleaching and functionalization of kaolinite on the mechanical and thermal properties of polyamide 6 nanocomposites.

Polyamide 6 nanocomposites (PA6)/kaolinite were prepared by melt compounding. First, kaolinite was bleached via a solvothermal reaction using oxalic acid as a bleaching agent; then, the bleached product was modified using dimethylsulfoxide (DMSO) and subsequently methanol (MeOH) via a displacement method. Thus, cetyltrimethyl ammonium bromide (CTAB) and triethoxy(octyl)silane (TEOS) molecules were intercalated into kaolinite nano-platelets. Seven types of nanocomposites were prepared using pristine, bleached or intercalated kaolinite. The kaolinite powder and the nanocomposite specimens were characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), thermal analysis, scanning electronic microscopy (SEM), whiteness index and tensile tests. The influence of the bleaching process of kaolinite and the intercalation methods on the whiteness index of the nanocomposites was also observed, in which the whiteness index of the functionalized kaolinite nanocomposites was enhanced by up to 10.65% when compared to neat PA6. The thermal results revealed that the intercalation and functionalization greatly affect the thermal stability of the virgin polymer. On the other hand, the intercalation of kaolinite enhances the dispersion/distribution, improves the interfacial adhesion, and increases the aspect ratio of the kaolinite nanoparticles; this affords remarkable nanocomposite property enhancements, represented by a high Young's modulus value of 4.68 GPa and a maximum percentage growth of 80.6% for silane-grafted kaolinite nanoparticles at just 8 wt%.

Effect of electrostatic forces on the porosity of saturated mineral powder samples and implications for chalk strength

Electrostatic forces acting at the particle scale can be an important drive behind water weakening of chalk. Upon the replacement of oil with brine, ions present in the imbibing brine can exchange with ions already adsorbed to the calcite surface, leading to a change in the surface potential. This can cause an increase in the disjoining pressure between particles, either reducing the cohesion of particles connected via contact cement or decreasing friction between free particles. We have assessed the effect of electrostatic forces by measuring pore-water effects on porosity in sediment columns using nuclear magnetic resonance relaxometry. Samples of calcite, quartz, or kaolinite powder were saturated with brines containing ions found in seawater ([Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]) at varying ionic strengths and as a nonpolar reference, with ethylene glycol. The difference in porosity between samples saturated with glycol and with brines reflects the disjoining pressure. For calcite samples, saturation with solutions containing divalent cations ([Formula: see text] and [Formula: see text]) lead to higher repulsive forces between the grains, whereas adsorption of [Formula: see text] counteracts the initially positive surface charge, lowering the repulsive forces. Calcium-based brines induced the highest repulsion, probably due to higher surface coverage of [Formula: see text] than that of [Formula: see text] due to its smaller hydrated radius. For kaolinite, differences in potential between the silica and alumina faces as well as the edges can either lead to repulsion between particles or to flocculation, depending on the ionic strength and ionic species of the fluid. Our results indicate that low-salinity water flooding may lead to kaolinite mobilization within reservoirs. A comparison of the results from our calcite powder experiments with results from mechanical tests performed on chalk samples indicates that electrical double layer-related forces can contribute to the weakening of chalk. Saturating brines for which the repulsion between grains in powder experiments was larger corresponds to weaker chalk samples.

Interface load–displacement behaviour of sand grains coated with clayey powder: Experimental and analytical studies

In the present study, the micromechanical behaviour at the interfaces of sand grains coated with kaolinite powder is examined. Two different classes of coated grains were produced, one with lighter coating and one with heavier coating. The interface micromechanical experiments were conducted on pairs of grains and the emphasis was placed on the normal and tangential load-displacement relationships and the inter-particle friction of the different pairs highlighting the differences between uncoated and coated grains and also between the different classes of coating. All the experiments were conducted using a micromechanical custom-built loading apparatus and for the analysis of the data, analytical models from the literature were used, where adequate modifications were applied in specific in the tangential direction to match with the experimental results. Iteration processes, image analyses and microscopic image observations were adopted in the study of the frictional behaviour of the grains as well as the study of the damage of the surfaces. Work done and rate of work done concepts were introduced and linked to the damage of the surfaces of the grains and the role of repeating the shearing tests following the same shearing paths were particularly emphasized. The results from the study can provide some useful insights into the grain-scale behaviour of soil grains as well as input parameters in DEM studies.

Adsorption of Cu(II), Ni(II) and Zn(II) ions by nano kaolinite: Thermodynamics and kinetics studies

An easy route for preparation emulsion of kaolinite (Al2Si2O5.4H2O) from Sweileh sand deposits, west Amman, Jordan by hydrochloric acid under continuous stirring for 4 h at room temperature was performed and nano kaolinite powder was used as an adsorbent for the removal of Cu(II), Zn(II) and Ni(II) ions. Nano kaolinite was characterized by XRD, FT-IR and SEM techniques. Effect of pH, adsorbent dose, initial metal ion concentration, contact time and temperature on adsorption process was examined. The negative values of ΔGo and the positive value of ΔHo revealed that the adsorption process was spontaneous and endothermic. The Langmuir isotherm model fitted well to metal ions adsorption data and the adsorption capacity. The kinetic data provided the best correlation of the adsorption with pseudo-second order kinetic model. In view of promising efficiency, the nano kaolinite can be employed for heavy metal ions adsorption.

A Novel Method for Mixing Nanomaterials with Soil

Mixing of nano-sized powders with soils (macro-sized powders) is a noteworthy issue for geotechnical projects. Thus, this study examined the horizontal ball mill mixing of nano-copper oxide with kaolinite. Ball milling parameters (rotation speed, weight ratio of balls to powder and milling time) of the planetary ball milling were optimized for proper mixing of nano-copper oxide and kaolinite powder. Results showed that increase in mixing time decreased the agglomeration of nano-copper powders and kaolinite and increased the homogeneity of nano-copper powder with kaolinite particles. The quality of mixing was assessed through intensity and scale of segregation using concentration data obtained through energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses. It was observed through these two tests that, increase in ball milling time after 6 hours resulted in grain size reduction. Field emission scanning electron microscopy analysis showed that nano-coppers were regularly found on the surface of kaolinite particles after 6 hrs. of horizontal milling at 4:1 ratio of balls to powder mixture. Furthermore, 24 hrs. mixing resulted in grinding of kaolinite particles and hence their size was reduced. Particle size analysis confirmed these results, as the highest size span value of 3.417 was observed after 6 hrs. milling with speed of 200 rpm.

Characterization of Libyan metakaolin and its effects on the mechanical properties of mortar

Environmental concerns, stemming from high-energy demands and CO2 emission associated with cement manufacture, have brought about pressures to reduce cement consumption through the use of supplementary cementitious materials (SCMs). Besides addressing environmental concerns, the incorporation of SCMs in cement bound materials and concrete can modify and improve specific concrete properties. Metakaolin (MK) in an important SCM which can enhance the performance of cementitious composites through its high pozzolanic reactivity. This study was carried out to characterize the materials and to assess the effect of Libyan metakaolin (LMK) on the mechanical properties including the compressive strength of cement mortar. LMK was produced by calcining kaolinite clay at 700°C for 2 h. X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Differential Thermal Analysis / Thermo-Gravimetric analysis (DTA/TG) and Fourier Transform Infrared Spectroscopy (FTIR) s were performed on the raw and calcined kaolinite powders. Seven mixes were prepared with different LMK replacement percentages (0.0 to 30%), by weight of cement, and a constant water binder ratio (w/b) of 0.5. The specimens were cured for 3, 7, 28, 56 and 90 days. At the end of each curing period, the specimens were tested for compressive strength. The results confirm the transformation of kaolinite clay into metakaolin and the pozzolanic reactivity of the produced LMK and conforms to ASTM requirements in this respect. The study confirms that LMK could be effectively used in reducing cement content up to 30% by weight without compromising compressive strength of the cement mortar.

A micromechanical experimental study of kaolinite-coated sand grains

Abstract The micromechanical behaviour of sand grains coated with a clay agent is examined in the study. The coating was applied using a suspension of sand grains and kaolinite powder with a wide spectrum of coating percentages and durations of vibration to achieve different classes of coating. Element composition, measurement of surface roughness and single grain crushing tests were used for the basic characterisation of the materials. From pure sand grains to lightly coated grains, there was observed a significant shift of the inter-particle friction but the differences were smaller between lighter and heavier coating. Microscopic images showed the creation of debris during shearing which might have contributed to the increase of friction from the uncoated to the coated grains.

Acid-base properties of kaolinite, montmorillonite and illite at marine ionic strength

Abstract In marginal marine settings, understanding the role that clay minerals play in the transfer of metal cations from the water column to the seafloor is important if the composition of modern muds is to be used as a proxy for the precursors of ancient shale deposits. In this study, we conducted potentiometric titrations of three naturally abundant clay minerals (kaolinite, montmorillonite and illite) in 0.56 M NaCl electrolyte solutions to ascertain the surface reactivity of each clay mineral at seawater ionic strength. Our results demonstrate that all three clay minerals were increasingly anionic as pH increases from 3 to 9, with montmorillonite having the highest negative-charge. The potentiometric titrations and adsorption data were modeled using both non-electrostatic (NEM) and electrostatic (constant-capacitance model, CCM) surface complexation models (SCMs). A two-site surface complexation model, that included one basal siloxane surface site (≡X−) and one amphoteric edge site (≡SOH), provided an excellent fit for the protonation data of each mineral. Cd(II) adsorption experiments were conducted to quantify the magnitude of cation adsorption, which showed that 10 g montmorillonite, illite, and kaolinite powder could bind an equivalent of 4.7 × 10−4 g, 4.3 × 10−4 g, and 4.0 × 10−4 g of Cd, respectively, under conditions relevant to seawater (initial Cd concentration of 8.9 × 10−6 M, and pH = 8). To place this value into the context of modern riverine clay inputs to the ocean, 13.5 × 109 tons of total suspended sediment are deposited annually (Milliman and Meade, 1983) of which 10 to 25% is clay (Manheim et al., 1970; Schroeder et al., 2015). The total amount of Cd adsorbed to suspended clay minerals entering the modern oceans could then amount to approximately 104 to 105 tons per year. The results of this study highlight the potential role of clay minerals in transporting metals from the ocean water column to the seafloor.

Designing Injection Water for Enhancing Oil Recovery from Kaolinite Laden Hydrocarbon Reservoirs: A Spectroscopic Approach for Understanding Molecular Level Interaction during Saline Water Flooding

Numerous experiments were performed to understand the mechanism(s) behind incremental oil recovery from hydrocarbon reservoirs during low saline water flooding (LSWF). It is believed that the roles of clay minerals present in the hydrocarbon reservoir rocks and the salt concentration in the injected water have a significant effect on the oil recovery during LSWF. Yet, the exact interaction mechanism(s) is still doubtful for designing injection fluids for enhancing oil recovery from subsurface reservoirs. For understanding the interaction between reservoir components explicitly, kaolinite and crude oil, and the interaction between reservoir components and injection saline water, three dead crude oil samples collected from different reservoirs of Cambay basin, India, and two kaolinite powder samples were used in this study. The kaolinites are different on the basis of their exchangeable cations, Fe3+ substitution in octahedral sites, and cation exchange capacity (CEC) values. The three crude oils show differences regarding asphaltene content and the abundance of polycyclic aromatic hydrocarbon in asphatenes. The interaction between reservoir components, particularly, kaolinite and crude oil, was demonstrated by keeping both the kaolinite and crude oil mixtures for two months. Detailed analysis of X-ray diffraction patterns, Fourier transform infrared (FTIR) spectra, and CEC values indicated that the polar oil components are adsorbed onto the interlayer surfaces of kaolinite, making it oil wet, and the interaction depends highly upon the composition of kaolinite and crude oil. The oil removal capacity of three brine concentrations of 500 (low saline), 3000 (intermediate saline), and 8000 ppm (high saline) of NaCl, CaCl2, and MgCl2 from oil adsorbed kaolinites was investigated using UV–visible and fluorescence spectroscopy techniques. The present study demonstrated that low saline water (500 ppm) rich in Na+ ion is more capable of desorbing the maximum amount of 4–6 ring size polycyclic aromatic hydrocarbon (PAH) components from kaolinite interlayer surfaces with respect to Ca2+ and Mg2+ ions. The composition of polar oil components, particularly, asphaltenes enriched with 4–6 ring PAH, greatly influences the recovery of oil from a mixed wet to oil wet kaolinite laden hydrocarbon reservoir during saline water flooding. Thus, apart from the concentration level of the saline water, the type of cation present in the saline water plays the major role during LSWF. The kaolinite composition, its crystallinity, and ring size of PAH in asphaltenes present inside a hydrocarbon reservoir also influence the enhanced oil recovery (EOR). These molecular level insights are valuable for designing effective injection fluids for enhancing oil recovery during LSWF in kaolinite laden hydrocarbon reservoirs.

A kaolinite-based filter to capture gaseous cesium compounds in off-gas released during the pyroprocessing head-end process

In this study, a new filter was developed to capture radioactive cesium vapors evaporated from spent nuclear fuels during the pyroprocessing head-end process. For the fabrication of the filter, kaolinite powder was used as a raw material to form a fixed composition of silicon and aluminum oxide. The feasibility of the kaolinite-based filter was investigated using a system that enables the capture of gaseous cesium with respect to the trapping temperature. Characterization of the filters after cesium trapping showed that cesium vapors were chemically adsorbed in the filters by forming thermally stable cesium compounds. In addition, most of the volatilized cesium was successfully separated by the kaolinite-based filter.

Novel kaolinite based coolant for hyperthermal pyrotechnic aerosol cooling

Novel spherical pyrotechnic aerosol cooling granulates which are made of 42.8% kaolinite powder, 38.8% water, 8.1% epoxy A&B glue and 10.2% ethyl cellulose are successfully synthesized and can cool down the temperature of hot pyrotechnic aerosol from 1400 to 400°C below with only a 1:1 mass ratio of coolant to the aerosol forming agent. The cooling system is a packing bed randomly stacked with 5mm diameter cooling granulates. The kaolinite based cooling granulate has proper yield stress to provide the cooling bed a constant porosity in order to avoid any tunneling effect and granulate structural failure during hot aerosol cooling. Moreover, the synthesis process of current novel kaolinite based granulate coolant is simple and economic. Compared to other coolants like irregular granite gravels or ceramic intalox used for pyrotechnic aerosol cooling, the cooling performance of spherical kaolinite based cooling granulates is superior.

Compaction of quartz-kaolinite mixtures: The influence of the pore fluid composition on the development of their microstructure and elastic anisotropy

Shales play important roles in sedimentary basins, acting as both seals and reservoir rocks, and knowledge of their anisotropic velocity trends is of practical importance for correct seismic image processing and inversion, and for seismic to well tie. Whereas velocity-depth trends are extensively studied for conventional reservoirs and critical factors that control their compaction are well understood, little work has been done on shales. Compaction trends of shaly formations are controlled by a number of parameters such as clay mineralogy, silt fraction and depositional environment. This large number of parameters, which are difficult if not impossible to control in naturally deposited shales, make the study of shale compaction a statistically complex, multivariate and non-unique problem. In such a situation, laboratory experiments that allow precise planning of mixture mineralogy and chemical compositions of pore fluids as well as an accurate control of microstructural changes seems to be an attractive alternative.In this work, we have conducted two sets of compaction experiments on quartz-kaolinite mixtures with 100%, 75% and 60% of kaolinite powders (dry weight). In the first set, the use of a KCl brine solution to saturate the mixtures has led to the aggregation of the existing clay particles with each other and with silt particles. In the other set, the mixtures have been treated with a dispersant to separate existing clay aggregates into individual platelets. The mixtures have been further compacted in an oedometric cell at uniaxial stresses up to 30 MPa. Compressional (in vertical and horizontal directions) and shear (in vertical direction) ultrasonic wave velocities have been measured during these compaction experiments and the P-wave anisotropy has been estimated. The effect of the chemical composition of the pore fluid on shale microstructure has been studied using the micro-CT and SEM image analysis. Neutron diffraction experiments have been conducted to understand the orientation of clay platelets at the final stage of the compaction.Our research shows that the chemical composition of pore fluid significantly affects the microstructure of the clay component and via this the elastic properties of the artificial shales. The samples with the dispersed clay microstructure (DCM) have shown larger elastic anisotropies at the same porosity and significantly larger anisotropies at the same stress. The dispersed clay platelets have orientated preferably parallel to bedding plane while the clay platelets in the samples with the aggregated clay microstructure (ACM) show a wider angle distribution in the absence of quartz particles (100% kaolinite samples). In the case of 40% of quartz fraction though, the clay particles are more aligned in the ACM sample than in the DCM one.