Clay Distribution Research Articles

Detrital clay grain coats in estuarine clastic deposits: origin and spatial distribution within a modern sedimentary system, the Gironde Estuary (south‐west France)

AbstractPorosity and permeability may be preserved in deep sandstone reservoirs by clay coating (mainly chlorite) which limits quartz overgrowths. Chloritization around quartz grains results mainly from mineralogical transformations of pre‐existing clays. It is fundamental to study those clay precursors to better understand and predict the location and distribution of clay coatings in subsurface sandstones for petroleum or geothermal prospecting. This paper reports a high‐resolution analysis of the composition, distribution and fabric of clays along a modern estuary, the Gironde (south‐west France). The scale of the study ranges from thin sections, through sand bar bodies, up to the entire estuary. Results show that clays are detrital and deposited at the same time as sand grains despite strong hydrodynamic conditions. Clays bind to medium‐grained sands forming detrital clay grain coats. On average, 26% of detrital sand grains are coated along the entire length of the estuary. Coat thickness varies from 1 μm to more than 200 μm, and coat coverage exceeds 30% in some samples. The turbidity maximum zone position (surface water turbidity from 1 to 10 g l−1) in the estuary, which is controlled by seasonal variations in hydrodynamic processes, significantly impacts the location of the maximum clay content and the abundance of coated grains in sandy facies along the estuary. Flocculation in the water column results in the accumulation of suspended matter and contributes to the high turbidity in the estuary. Exopolymeric substances produced by diatoms are observed both in the field and by cryo‐scanning electron microscopy, suggesting that they may play a major role in binding detrital clay around sand grains. Finally, tidal bars and heterolithic point bars in the estuary funnel and estuarine channels are prime sedimentological targets for finding clay coatings and potentially good reservoir quality in deeply buried sandstones.

Lateral and vertical juxtaposition of matrix‐rich and matrix‐poor lithologies caused by particle settling in mixed mud–sand deep‐marine sediment suspensions

AbstractSandy sedimentary rocks rich in detrital matrix (>10% silt/clay) have long been recognized in the ancient sedimentary record, and nowhere more commonly than in deep‐marine turbidite systems. Despite this, their depositional mechanisms remain poorly understood, in part because these rocks, which are enriched in fine‐grained sediment, are often poorly exposed in outcrop or are confined to observation in core. Matrix‐rich strata in the Neoproterozoic Windermere Supergroup, in contrast, are very well‐exposed and show systematic changes in lithofacies over distances of several tens to a few hundreds of metres along‐strike. Notably, these strata are observed in both basin floor and continental slope deposits, suggesting that their occurrence and systematic lithological arrangement is related to mechanistic, rather than palaeogeographic, controls. Specifically, the facies transect consists of structureless, clayey sandstone that transforms along‐strike to a two‐layer deposit with the development of an upper, planar‐based, markedly more matrix‐rich layer. Further along‐strike, the basal clayey sandstone thins and eventually pinches out, leaving only the (upper) sandy claystone layer, which in turn thins along‐strike and then pinches out. These systematic changes in lithology, but more specifically the distribution of clay, is interpreted to form a depositional continuum related to particle settling in a horizontally advecting, high concentration particle suspension formed along the margins of an avulsion‐related high‐energy turbulent suspension.

A quantitative research of water distribution characteristics inside shale and clay nanopores

Understanding the fluid distribution characteristics inside nanopores are of great significance to evaluate shale gas reservoirs. In this work, the quantitative evaluations for water saturation distribution of porous shale and clay are performed by experiments. The experimental results show that the capillary condensation is remarkable for clay pores during the process of water adsorption, the pores less than 6.76 nm would be blocked by the capillary water when the relative humidity is approximate to 0.98; moreover, the inorganic pore is hydrophilic while the organic pore is hydrophobic, the coupled effect make less water uptake inside shale sample. Meanwhile, a mathematic model for studying the effect of pore shape on water adsorption is established based on the difference of morphology characteristics between organic and inorganic pore. The results indicate that the slit pore is better similar with the actual condition, and the calculated film thickness and water saturation is more coincide with the measured value. Thus, the slit pore is more appropriate than the circular pores for studying the water uptake characteristic of shale. Our work lays the foundations for better understanding and evaluating the fluids occurrence pattern and gas generation mechanism of different pores in shale reservoir.

Effect of Different Sands on One-Dimensional and Hydraulic Consolidation (Radial) Tests of Clay

In settlement problems, the soil type is generally determined by the sand, silt and clay contents. Sieve analysis considers only the percentage of sand, and the grain shape of the sand is ignored. Specifically, sand grains with different characteristics are considered a single type of sand. In this study, variations in the pore size distribution of clay associated with sand particles of different shapes are investigated via consolidation tests. For this purpose, mixtures containing 10%, 20%, 30% and 40% of the two types of sand additions to clay were obtained. Samples of reconstituted clay were prepared using the slurry deposition method. One-dimensional consolidation and radial consolidation (with drainage radially outwards) tests were performed on the samples, and the relationship between the pore size distributions of the mixtures and the consolidation tests was examined. In addition, the mixtures were analysed using helium pycnometry, X-ray diffraction, mercury intrusion porosimetry, Brunauer–Emmett–Teller surface area analysis and scanning electron microscopy.

Determination of static and dynamic characteristics of microscopic pore-throat structure in a tight oil-bearing sandstone formation

In this study, an integrated and practical framework has been developed to quantify the static and dynamic characteristics of microscopic pore-throat structure in a tight oil-bearing sandstone formation. Experimentally, thin sections were prepared out of core samples collected from a tight formation, while corresponding analyses were respectively performed by using the scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. In addition to pore types and clay minerals, the size, fraction and distribution of grains were identified and classified. Pore and throat size distributions were then determined by using pressure-controlled mercury injection (PMI) and rate-controlled mercury injection (RMI) respectively to quantify the changes in microscopic pore-throat structure after brine flow tests. Subsequently, displacement experiments of waterflooding and surfactant flooding were performed to determine the upper and lower cutoff value of the movable throat radius. Rock grains primarily containing fine sand and silt are found to possess complex compositions, while both intergranular pores and intragranular dissolution pores are dominant. Nano-throats may have developed in a tight formation due to small radii of pores and throats. Compared to the pore size distribution, throat radius is found to be reduced by 13.9% after brine flow tests, while the cutoff value of movable throat can be decreased to 0.019 µm from 0.033 µm by using a surfactant.

Clay amount and distribution influence organic carbon content in sand with subsoil clay addition

Sandy soils cover large proportions of Australia’s cereal-cropping region and are wide-spread globally. Sandy soils often have low organic C (OC) content due to limited plant growth and rapid decomposition because of low clay concentration. The addition of subsoil clay to sandy soil has the potential to increase OC storage. This study aimed to (i) compare OC stock in a range of clay-amended and unamended sandy soils under cereal cropping and (ii) identify factors that influence OC stock to develop best practices to increase OC storage in clay-amended sandy soils. The study was carried out on four agricultural properties in South Australia and assessed soil OC content, clay content and select physical and chemical properties of clay-amended treatments compared to unamended sands. Clay-amendment treatments differed in the method of clay amendment (clay spread and delved), depth of incorporation (shallow and deep) and amount of subsoil clay added to the surface 30 cm of sand. For each site and treatment, ten soil cores to 50 cm depth were collected within a 25 m grid. There was a positive correlation between OC and clay stock, but it only explained 46% of the variation in OC stock. This indicated that other factors influenced OC stock in clay-amended treatments. Even vertical distribution of clay within the surface 30 cm was a key factor to increase OC storage in clay-amended soils. Subsoil clay properties and the amount added to the surface 30 cm, as well as depth to undisturbed subsoil also influenced OC stock.

Clay Distribution Patterns Regulate Natural Attenuation of Marcellus Shale Waters in Natural Aquifers

This work examines the largely unexplored role of clay distribution patterns in determining reactive transport and natural attenuation of Marcellus Shale waters accidentally released into natural w...

Assessment of arsenic and heavy metal pollution and ecological risk in inshore sediments of the Yellow River estuary, China

In order to investigate the pollution levels, sources and ecological risks of arsenic (As) and heavy metals (Cr, Ni, Cu, Zn, Pb and Cd) in inshore sediments of the Yellow River estuary, the surface sediment in areas of inshore coastal waters were sampled in October 2014 as the flow-sediment regulation project (FSRP) was implemented for 13 years. Results showed that the concentrations of As and heavy metals in inshore sediments of the Yellow River estuary were in the order of Zn > Cr > Cu > Ni > Pb > As > Cd. Higher levels of As, Cr, Ni, Cu, Zn and Pb generally occurred in fine-grained sediments of the Yellow River estuary and the southeast region, which was consistent with the spatial distribution of clay. In contrast, higher concentrations of Cd were generally observed in northwest area of the Yellow River estuary and near the Qingshuigou estuary, which showed similarly spatial distribution with that of sand. The sediment quality guidelines (SQGS) and geoaccumulation indices (Igeo) indicated that the inshore sediments were polluted by Cu, Cd, As, Pb and Zn, and, among them, Cd pollution was more serious. Ecological risk indices (E ) demonstrated low risks for Cr, Ni, Cu, Zn, Pb and As, and high potential toxicity by Cd. The integrated ecological risk index implied that 6.8% of stations presented moderate risk, 4.5% of stations exhibited disastrous risk, and 88.7% of stations demonstrated considerable risk. Principal component analysis indicated that Ni, Cu, Zn, Pb and As might originate from common pollution sources, while Cr and Cd might share another similar sources. With the continuous implementation of FSRP, As and heavy metal levels in inshore sediments of the Yellow River estuary could be classified as stage I (2002–2010) and stage II (2010–2014). In the stage I, As, Cr, Ni, Cu, Zn and Pb levels fluctuated but decreased significantly, whereas Cd concentrations showed little variation. In the stage II, As and heavy metal levels significantly increased although some little fluctuations occurred. The continuous accumulation of As and heavy metals (especially for Cd) in inshore sediments of the Yellow River estuary would occur again as the FSRP was implemented for 9 years (since 2010). The ecotoxicological risk of Cd, As, Ni and Cu in inshore sediments might be more serious since the accumulation of the four elements would be continuously occurred in future years. Next step, there will be long-term potential consequences for marine organism if effective measures are not taken to control the loadings of metal pollutants into estuary.

Effect of polyampholyte-bentonite interactions on the properties of saltwater mud

Hydrolyzed poly(acrylamide/dimethyl diallyl ammonium chloride) was synthesized via free-radical copolymerization followed by hydrolyzation. The synthesized polyampholyte was characterized by Fourier transform-IR and 1H NMR measurements. An intensive investigation was carried out to identify the effect of salt, temperature, pH, polymer composition, and intrinsic viscosity on the adsorption of the polyampholyte samples on bentonite, the bentonite particle size distribution, and the filtration of saltwater mud. In the mud samples, the polyampholyte interacted with bentonite via adsorption. By introducing electrostatic repulsion and entropic repulsion, the polyampholyte helped maintain a broad bentonite particle size distribution, allowing the bentonite to form a densely packed filter cake after aging treatment. In summary, using a polyampholyte with a high cationic group content, a high intrinsic viscosity, and an anionic group content in a specific range resulted in a strong adsorptive ability on bentonite and allowed ideal control over the clay particle size distribution and mud filtration behavior.

Clay minerals damage quantification in sandstone rocks using core flooding and NMR

Sandstone oil reservoirs consist of different clay minerals such as kaolinite, illite, and chlorite. These clay minerals highly affect the formation damage during enhanced oil recovery (EOR) and well stimulation operations in these reservoirs. No attention was paid to investigate the effect of these clay minerals on the formation damage during different reservoir processes. In addition, no solution was introduced to mitigate the effect of clay minerals on the formation damage in sandstone reservoirs. In this study, the effect of clay mineral contents and type on the formation damage was studied in detail by injecting water and HCl as damaging fluids. Bandera grey, Berea, and Bandera brown sandstone rocks with various clay mineral contents were studied. XRD was used to characterize the sandstone rocks to determine the clay type and content in each rock. Two core plugs from each rock were selected for HCl and water injection. Core flooding experiments were performed to measure the initial and final permeability. In the core flooding experiments, fluids were injected into the cores at 25 °C and at a backpressure of 1000 psi. SEM was carried out before and after flooding for the tested rocks to locate the change in the clay distribution inside the rocks. The NMR analysis of core samples was done before and after flooding with the damaging fluid to quantify the formation damage and to find the possible damaging mechanism. NMR was used to locate the damage inside the rock due to the migration of clay minerals. Based on the core flooding, SEM, and NMR analysis, the maximum damage by the fresh water took place in Berea sandstone core due to fine migration and clay swelling. The illite clay mineral and chlorite can cause the formation damage on HCl injection. Illite can break down and migrates in the cores during the acid injection. In sandstone acidizing, chlorite clay mineral caused iron hydroxide precipitation inside the cores during treatment with mud acid. NMR showed that clay minerals plugged the pore throats of the rocks and reduced the rock permeability during the injection of fresh water.

A COMPARATIVE MINERALOGICAL STUDY OF SOME SOILS FORMED UNDER VARYING CLIMATIC CONDITIONS FROM NORTHERN IRAQ

To determine factors controlling abundance and distribution pattern of clay minerals, four soil pedons derived from calcareous sedimentary parent rocks in Northern Iraq were investigated. Results revealed that the regional variation in annual rainfall plays a major role in determining amounts and distribution of clay minerals such as palygorskite,chlorite, vermiculite, smectite, illite and kaolinite. Palygorskite and smectite are available in three studied soils (Al-Khuder, Tel-Auskuf and Sumeel) with average annual precipitation of around 250 mm, 350 mm and 480 mm respectively, but these minerals are totally disappear in Batofa profile (Annual rainfall around 800mm).However vermiculite illite and kaolinite are the dominated clay minerals in Batofa soil.XRD analysis was detected a small amounts of random interstratified layer silicate minerals.Biotite-vermiculite mixed layers were found in Batofa soil,but in Al-Khuder soil an increasing amounts of (chlorite - smectite) mixed layer was detected while in Tel-Auskuf soils it appears that (chlorite-vermiculite) is the dominated mixed layer and (chlorite-smectite) is available at Sumeel soil. The general variations in clay minerals content and distributions in different soil locations can be attributed mainly to weathering conditions and mineral transformation. Palygorskite is considered to be inherited in soils of arid regions with gypsum content and limited annual rainfall, whereas illite, vermiculite and kaolinite occurs in soils with high annual rainfall.

Estimation of Shale Intrinsic Permeability with Process-Based Pore Network Modeling Approach

A multi-scale pore network model is developed for shale with the process-based method (PBM). The pore network comprises three types of sub-networks: the $$\upmu $$ m-scale sub-network, the nm-scale pore sub-network in organic matter (OM) particles and the nm-scale pore sub-network in clay aggregates. Process-based simulations mimic shale-forming geological processes and generate a $$\upmu $$ m-scale sub-network which connects interparticle pores, OM particles and clay aggregates. The nm-scale pore sub-networks in OM and clay are extracted from monodisperse sphere packing. Nm-scale throats in OM and clay are simplified to be cylindrical and cuboid-shaped, respectively. The nm-scale pore sub-networks are inserted into selected OM particles and clay aggregates in the $$\upmu $$ m-scale sub-network to form an integrated multi-scale pore network. No-slip permeability is evaluated on multi-scale pore networks. Permeability calculations verify that shales permeability keeps decreasing when nm-scale pores and throats replace $$\upmu $$ m-scale pores. Soft shales may have higher porosity but similar range of permeability with hard shales. Small compaction leads to higher permeability when nm-scale pores dominate a pore network. Nm-scale pore networks with higher interconnectivity contribute to higher permeability. Under constant shale porosity, the shale matrix with cuboid-shaped nm-scale throats has lower no-slip permeability than that with cylindrical throats. Different from previous reconstruction processes, the new reconstruction process first considers the porous OM and clay distribution with PBM. The influence of geological processes on the multi-scale pore networks is also first analyzed for shale. Moreover, this study considers the effect of OM porosities and different pore morphologies in OM and clay on shale permeability.

Downhole physical property-based description of a gas hydrate petroleum system in NGHP-02 Area C: A channel, levee, fan complex in the Krishna-Godavari Basin offshore eastern India

India's second National Gas Hydrate Program expedition, NGHP-02, collected logging while drilling and sediment core data in Area C offshore eastern India, to investigate controls on the distribution and peak saturations of methane gas hydrate occurrences in buried channel, levee and fan deposits. Physical property results are presented here for the four Area C coring sites: NGHP-02-07, targeting an upper continental-slope channel deposit; NGHP-02-08 and −09, targeting levee deposits on either side of a channel further downslope, and NGHP-02-05, targeting a sequence of fan deposits extending out from the slope base. Coarse-grained sediment exists at each site, but site-specific differences in clay distribution provide significant controls on the gas hydrate distribution and saturation. At NGHP-02-07, only the upper ∼4 m of a ∼42 m-thick, relatively low clay-content, coarse-grained interval is inferred to be gas hydrate-bearing. NGHP-02-07 has a relatively thin, high-permeability overburden seal, and methane-rich fluid likely leaks from the primary reservoir. NGHP-02-08's levee deposit seal is similarly permeable near the reservoir, but becomes less permeable toward the seafloor. Relative to NGHP-02-07, methane is retained more effectively in the NGHP-02-08 reservoir, but that reservoir is interbedded with layers of high clay-content, low gas hydrate saturation sediment, limiting the maximum gas hydrate content for NGHP-02-08. NGHP-02-09, the second levee deposit site, has a thicker, less permeable overburden than NGHP-02-08, combined with >50 m-thick, low clay-content reservoir sediments. Correspondingly, NGHP-02-09 has a thicker gas hydrate-bearing reservoir with consistently higher gas hydrate saturations than NGHP-02-08. NGHP-02-05 has abundant coarse-grained material spread over nearly the entire drilling interval, but the sediment is poorly sorted. Gas hydrate is distributed among several primarily coarse-grained layers, but gas hydrate saturations are limited by relatively high clay contents, and an overlying seal that is too thin and permeable to effectively retain methane in the reservoir. • Clay content provides a primary control on the distribution and peak saturation of gas hydrate. • Gas hydrate was not observed to form in the coarse-grained, primary reservoir where the clay fraction exceeded ~0.3. • Overlying fine-grained sediment is a more effective low-permeability seal than the gas hydrate-saturated reservoir is. Imperfect seals in Area C can be linked with incomplete occupation of the coarse-grained sediment by gas hydrate.

Effect of Internal Magnetic-Field Gradients on Nuclear-Magnetic-Resonance Measurements and Nuclear-Magnetic-Resonance-Based Pore-Network Characterization

Summary Nuclear-magnetic-resonance (NMR) measurements have been extensively used for determining porosity, pore-size distribution, and fluid saturation in porous media. However, internal gradients of the magnetic field generated by the presence of paramagnetic or diamagnetic centers such as shale or clay particles can significantly affect NMR response. Consequently, the resulting interpretation for pore-size distribution and porosity is also affected. In this paper, we quantify the effect of internal magnetic-field gradients and spatial distribution of matrix components such as clay minerals on NMR response using pore-scale NMR numerical simulations. We also quantify the influence of the aforementioned parameters on the NMR-based evaluation of porous media. We used the finite-volume method to numerically solve the Bloch (1946) equations and simulated magnetization decay in porous media. We cross validated the reliability of numerical simulations using analytical solutions given for spherical pores in different diffusion regimes. The model was then used for simulation of NMR response in the pore-scale images of sandstone and carbonate rocks. We used Larmor frequency of 2 MHz, external magnetic-field gradient of 0.10 T/m, and half-echo spacing time of 0.5 ms for simulating NMR response in pore-scale images of sandstones and carbonates. We then developed synthetic cases using actual rock images covering a wide range of spatial distribution of clay minerals (i.e., paramagnetic centers) to quantify the sensitivity of NMR decay to internal magnetic-field gradients. We quantified the sensitivity of NMR response for distribution of clays as thin laminae in the rock and as thin layers on the surface of the grains. The results showed that at low concentration (0.3 to 0.7%) of dispersed clay, there is a negligible effect of internal magnetic-field gradients on magnetization decay. At higher concentration of dispersed clay (5.1 to 7.3%), we observed a significant effect of internal magnetic-field gradients on magnetization decay. The presence of shale minerals can cause 53% variation in the location of the transverse-relaxation-time constant (T2) and up to 67% relative error in the assessment of dominant pore sizes. Shale laminations containing clay were found to produce an effect of up to 31.8% on T2 relaxation-time constant, which could cause a relative error of 50.0% in estimates of dominant pore size in the rock. The outcomes of this paper demonstrated the effect of heterogeneous rock mineralogy on NMR response. The effect of internal magnetic-field gradients generated by shale and clay on NMR becomes relevant when shale and clay particles are close to the pore fluid and their magnetic field starts to affect the distribution of magnetic field in the pore space. The results reveal the importance of characterizing the distribution of shale and clay minerals before interpreting NMR response and can potentially improve conventional techniques of pore-network characterization (pore-size distribution and pore volume) in the presence of clay minerals where internal magnetic-field gradients are not negligible.

Sustainable Improvement of Marine Clay Using Recycled Blended Tiles

The usage of recycled material for improving problematic soil as a construction and pavement material has been a sustainable interest. Recycled blended tiles (RBT), a waste from ceramic tiles factories containing high amount of sodium and magnesium, was used as a soil stabilizer for marine clay improvement in this study. This research investigated the effects of sizes and percentages of RBT on the physical and strength properties, which included particle size distribution, Atterberg limits, compaction, and unconfined compressive strength (UCS) of marine clay. Microstructural characterization, including the scanning electron microscopic, energy dispersive X-ray spectroscopy, and X-ray diffraction was conducted on both untreated and treated marine clay-RBT samples to examine the mechanism of strength development. The addition of RBT reduced the water holding capacity, which then caused the reduction in soil plasticity (from 18 to 11%) and optimum water content (from 20 to 16%) along with the increase in peak dry density (from 1.66 to 1.74 Mg/m3). The UCS of marine clay increased from 50 to almost 220 kPa. The optimum RBT contents, providing the highest UCS, were at 20 and 30% for 0.063 mm RBT and 0.15 mm RBT, respectively. The UCS improvement of treated marine clay is attributed to the formation of cementation compounds, mainly aluminum magnesium silicate hydrate (A–M–S–H). The outcome of this research will allow the use of RBT as a low-carbon soil stabilizer across civil engineering applications.

Influence of Selectively Localised Nanoclay Particles on Non-Isothermal Crystallisation and Degradation Behaviour of PP/LDPE Blend Composites.

In immiscible polymer blend nanocomposites, nanoparticles can be localised either in polymer matrices or at the interface, invoking the simple question of how the spatial distribution of the nanoparticles and the resulting morphological changes affect the non-isothermal crystallisation and degradation kinetics. In this study, the non-isothermal crystallisation of polypropylene in polypropylene (PP)-rich compatibilised and non-compatibilised PP/low-density polyethylene (LDPE)/clay composites and their degradation are investigated. The non-isothermal crystallisation analyses show that the localisation of the clay particles in the blend composites has two opposing effects. First, the poorly dispersed clay particles at the PP/LDPE interface in the non-compatibilised blend composite has no significant effect on the crystallisation temperature of PP but allows the free movement of PP chains, resulting in a higher crystallinity of PP than that of PP in the neat blend. Second, the well-dispersed clay particles in the compatibilised blend composites disrupt the free movement of PP chains, resulting in a lower crystallisation temperature and crystallinity than that of PP in the neat blend. The influences of different selective localisations of clay particles on the activation energies of degradation are studied. The presence of maleated compatibilisers, clay, and the distribution of clay in the blend composite play important roles in determining the activation energies of degradation.

Preparation and Characterization of Chemical Agents for Augmenting Injectivity in Low Permeability Reservoirs

In this paper, experimental techniques have been developed to prepare and characterize chemical agents for augmenting injectivity in low permeability reservoirs. First, chemical agents are selected, formulated, and optimized on the basis of interfacial tension (IFT), scale inhibition ratio, and clay particle size distribution and specific surface area. The spinning drop method is utilized to measure the IFT between crude oil and the formulated solution, while contact angle between brine and rock surface is measured to examine effect of the chemical agents on the rock wettability. Also, scale inhibition ratio and antiswelling ratio are, respectively, measured by performing static-state scale inhibition experiments and centrifugation experiments. Then, displacement experiments are conducted to evaluate injectivity improvement after one pore volume (PV) of such formulated chemical agents has been injected into a core plug. It is found that the optimized solution consists of 0.15 wt % fluorocarbon surfactant FC-117, 4.00 wt % isopropanol, 1.20 × 10−3 wt % scale inhibitor 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA), and 1.50 wt % clay stabilizer diallyl dimethyl ammonium chloride (DMDAAC). The IFT between crude oil and the optimized solution can be reduced to 5.36 × 10−3 mN/m within a short time, while the scale inhibition ratio and antiswelling ratio are measured to be 94.83% and 86.96%, respectively. It is found from comprehensive evaluation experiments that such a formulated and optimized solution can not only alter the rock surface from oil-wet to water-wet but also reduce the scale formation of the reservoir brine. In addition, it is shown from displacement experiments that the pressure is decreased by 34.67% after the injection of such formulated solution. When the formulated solution contains 0–300,000 mg/L sodium chloride (NaCl) and 0–5000 mg/L calcium chloride (CaCl2) at 50–90 °C, the IFT between crude oil and the formulated solution can be reduced to lower than 10−2 mN/m.

Seismic site characteristics of shallow sediments in the Bangkok Metropolitan Region, and their inherent relations

This paper presents the site characteristics of soft deposits in Bangkok Metropolitan Region, and their inherent relations, which were explored using microtremor observations. The predominant period (TP) and shear wave velocity (VS) profiles from the surface to a 100-m depth at 150 sites over an area of approximately 150 × 200 km were explored using the Horizontal-to-Vertical (H/V) spectral ratio method and the Spatial Autocorrelation (SPAC) method, respectively. Spatial variations of TP and average VS are presented in maps and discussed with the distribution of soft clay. The results show that the shallow structure is rather uniform in the central area, having low VS, long TP, and thick soft clay. VS increases, while TP tends to decrease gradually towards the north and east and more sharply towards the west. Using a number of the observed site characteristics, relations among the average VS at different depths and TP were examined. Regression analysis revealed high correlations and almost linear relations among them, suggesting that VS at deep strata could be simply estimated from the shallow VS or TP. Finally, a simple scheme to estimate the VS profile using only the phase velocity at specific wavelengths is proposed.

Adhesion properties of the nanocomposites filled with aluminosilicates and factors affecting them: A review

Use of nanoclays for the adhesives enhancement is being considered in the review as well as adhesive properties of filled adhesives. Both structural and pressure-sensitive adhesives (PSAs) are discussed. Maximum adhesive properties are usually obtained when clay is exfoliated or at least intercalated, which is mostly achieved by using appropriate clay surface modifier, proper mixing techniques or both. In case of structural adhesives, overall improvement of cohesion strength and a decrease in the residual stresses in the system achieved in this case, are usually the main reasons for the adhesion strength growth at low clay content. Further clay addition causes appearance of defects and adhesion strength decrease, thus leading to the adhesion strength vs. modifier content dependencies with a maximum. An increase of 20–40% in lap shear or pull-out adhesion strength is often obtained at 1–2 wt% clay content. For PSAs shear resistance often increases notably with clays incorporation due to the increase in storage modulus (cohesive strength) of the systems, accompanied by a tack decrease because of the worsening in the conditions of adhesion joint formation. To obtain better compromise between tack and shear resistance a uniform clay distribution in the adhesive should be achieved, for this purpose in-situ polymerization techniques of clay incorporation and clay surface modification could be most helpful. Also, a trend to simultaneous increase in the shear and peel strength due to nanofillers incorporation could be observed for clay-filled PSAs. For non-crosslinked PSAs a structure with the elastic network formed by the polymer chains, adsorbed simultaneously at several nanoparticles seem to be most beneficial. An increase of PSA holding time up to 3–4 orders of magnitude could be obtained in this case, with simultaneous growth of peel strength at high clay content (30–40%).

Suitability of Foumban Clays (West Cameroon) for Production of Bricks and Tiles

Particle size analysis, Atterberg limits, X-ray diffraction, X-ray fluorescence and firing tests were used to determine physico-chemical, mineralogical and technological characteristics of residual lateritic (K1M, Ma2) and alluvial (KB3, KG3) clays from Foumban (West-Cameroon). For technological properties, the samples were pressed and fired over a temperature range of 900d relative high feldspars (20%) and illite contents (10%) in KB3 and MA2; high smectite content in KG3 (up to 20%). Chemical analyses indicate high SiO2 (49% - 77%) and low Al2O3 (14% - 23%) contents in the four samples, with comparatively low contents of iron oxides (4% - 7% in samples KB3 and KG3, 2.5% in MA2 and ~1.5% in sample K1M). The particle size distribution of the alluvial clays (KG3 and KB3) differs considerably: 7% to 37% of clay fraction, 20% to 78% of silt, and 15% to 58% of sand, while residual clays (K1M and MA2) present on average 12% of clay, 51% of silt and 37% of sand. Two raw clays (KB3 and MA2) can be used for bricks/tiles production without beneficiation or addition. K1M requires some flux addition to decrease the sintering temperature while KG3 presents poor properties due to the combined occurrence of smectite and a high clayey fraction (37%). Such mineralogical composition is responsible for very high plasticity (PI: 50), high shrinkage (LS: 5% - 16%), low porosity (OP: up to 21%) and high flexural strength (FS: 16 - 23 N/mm2) above 1050&degC. This last clay is therefore less appropriate for bricks and roofing tiles production since degreasers must be added to the raw material.