In the North Sea Tertiary section, wellbore instability problems are frequently reported in Palaeocene-Early Oligocene smectite-rich mudrocks. Analysis of the mechanical properties of these Tertiary mudrocks is generally hampered by the lack of suitable core material. This study represents an attempt to study the geomechanical behaviour of mudrocks by triaxial tests of side-wall cores obtained from the borehole wall. The tests performed include measuring the changes in pore pressure during shearing and undrained shear strength in specimens initially consolidated to in situ effective stress levels. The coefficients of permeability (kf), estimated from the consolidation time behaviour range from 2.6 x 10-11 to 2.4 x 10-12 m/s. The tested cores behaved like slightly overconsolidated to normally consolidated materials with an initial near constant volume (elastic behaviour) for low deviatoric load followed by an increasingly contractant behaviour approaching failure. Compared with results from onshore analogues, the strength properties of the investigated mudrocks appear to be related to their content of expandable clay minerals. A wellbore stability chart to forecast adequate drilling fluid pressures for future wells has been developed by the use of linear (Mohr-Coulomb) failure criteria based on the peak strength data. It is demonstrated that side-walt cores can provide satisfactory test materials for rock mechanical analysis, and their use may serve to improve our knowledge of the rock mechanical behaviour of typically troublesome mudrocks for which no conventional cores are available.

The structure of kaolin has been examined together with aspects of dosimetry and energy loss mechanisms of radiation to explain the formation of g = 2 EPR centres. The analysis points to the formation of a trapped hole on the ‘inner layer’ oxygen atoms of kaolin located at the boundaries between divalent ion and trivalent ion ‘cells’, in particular at the boundaries with excess negative charge. Direct interaction of X-rays with atoms and the possibility of proton recoil are eliminated. The means of production appears to be by transfer of charge following ionization of atoms by secondary electrons, with transfer of vacancies ultimately to the oxygen ions. Mechanisms which result in a decrease in signal strength with increase in concentration are examined. It is concluded that the cell mechanisms discussed are consistent with the rates of production and that at 20 Mrad (air) the number of centres should be reaching saturation.

X-ray powder diffraction data were used to determine the mineralogical composition of the fine suspended material present in nine English rivers. The mineralogy of these solids is discussed in relation to the geological formations through which the rivers flow.

Synthetic hectorites and the corresponding surfactant-exchanged clays have been characterized by X-ray diffraction and 1H, 7Li, 13C, 23Na and 29Si solid-state nuclear magnetic resonance (NMR) spectroscopy. The low-charge clays retain water more efficiently, forming aggregates without extensive drying. The hydroxylated hectorite exhibits two 1H NMR signals near 0 ppm whereas the fluorohectorites are characterized by a single peak in the same region. The 23Na 2D 3Q magic angle spinning (MAS) spectra of the low-charge hectorites show a single peak. The 29Si NMR shift depends on the interlayer charge. Tactoids formed by the low-charge hectorites reduce the rate of surfactant incorporation. The population of the all-trans conformer of the hydrocarbon chain, determined by 13C MASNMR, varies with the surfactant content. 13C NMR relaxation data show an increase in mobility with the surfactant loading and along the long alkyl chain, from the polar head to the terminal group. Complexity of the motional behaviour precludes any detailed analysis. These modified clays are not useful in preparing poly(ε-caprolactone) nanocomposites by in situ polymerization.

The adsorption and retention of phosphates in soil systems is of wide environmental importance, and understanding the surface chemistry of halloysite (a common soil clay mineral) is also of prime importance in many emerging technological applications of halloysite nanotubes (HNTs). The adsorption of phosphate anions on tubular halloysite (7 Å) has been studied to gain a greater understanding of the mechanism and kinetics of adsorption on the surface of HNTs. Two well-characterized tubular halloysites with differing morphologies have been studied: one polygonal prismatic and one cylindrical, where the cylindrical form has a greater surface area and shorter tube length. Greater phosphate adsorption of up to 42 μmol g–1 is observed on the cylindrical halloysite when compared to the polygonal prismatic sample, where adsorption reached a maximum of just 15 μmol g–1 compared to a value for platy kaolinite (KGa-2) of 8 μmol g–1. Phosphate adsorption shows strong pH dependence, and the differences in phosphate sorption between the prismatic and cylindrical morphologies suggest that phosphate absorption does not occur at the same pH-dependent alumina edge sites and that the lumen may have a greater influence on uptake for the cylindrical form.

Petrographical studies can be undertaken to investigate the effects of production operations on sandstone reservoirs and to identify the nature of any rock-fluid interaction. In combination with diagenetic models the results may be employed to predict the effects of field development programmes on reservoir mineralogy, and to avoid costly damage to the reservoir's permeability. Acidization to remove drilling mud from Reservoir A samples was undertaken in two stages to avoid adverse rock-fluid interaction. HCl dissolved siderite and chlorite but did not increase permeability. This is because the dissolved siderite released previously cemented clay particles into the pore space. A subsequent mixture of HCl and HF dissolved all the clays present in the treated area including the drilling mud, but also etched the quartz cement. Permeability increased significantly but the rock's strength decreased. This could cause an influx of loose sand during hydrocarbon production. Water injection into Reservoir B samples caused a variety of rock-fluid interactions. In finer-grained samples movement of siderite rhombs as well as clay particles blocked pores, and changes in porewater composition caused smectite to swell. Both effects caused permeability to decline. In the coarser-grained siderite-free samples, permeability improved after oil and clay particles had been displaced. In the reservoir these effects would combine to exacerbate the effects of the existing reservoir heterogeneity. Steam injection into Reservoir C samples caused mineralogical reactions. Amounts of dolomite and kaolinite decreased, and smectite and calcite were generated. This may affect the permeability of the reservoir and will determine whether oil can be produced through the affected sediment.

Four major sedimentary sequences of the Triassic and Upper Jurassic of the Main Claymore Oilfield of the North Sea each contain a characteristic suite of diagenetic minerals and fabrics. (1) Triassic Skagerrak Formation fluvial sandstones contain early authigenic pore-lining smectite, together with kaolinite and chlorite which form grain replacements and pore fills. Quartz and feldspar overgrowths are minor. Ferroan dolomite forms a late diagenetic patchy poikilotopic cement. Smectite is converted to illite-smectite in a 5 m thick zone beneath the sub-Jurassic unconformity. Smectite formed early in diagenesis prior to oil migration and destroyed permeability. Thus oil is not found in these sandstones although they occur in the oilzone. (2) The Piper Formation (late Oxfordian/early Kimmeridgian) paralic deposits mainly contain authigenic, pore-lining illite-smectite, vermicular kaolinite grain replacements and pore fills. Quartz overgrowths are generally well developed. (3) The Kimmeridge Clay Formation (early Kimmeridgian/early Volgian) comprises thin marine sandstone turbidites, contained within a thick siltstone/shale sequence. In the sandstones (the ‘Ten Foot Sandstone’) discrete double-ended quartz crystals (1–20 µm) developed prior to quartz, K- and Na-feldspar overgrowths. Only minor kaolinite and lllite-smectite are present. Late diagenetic dolomitic occurs as a patchy poikilotopic cement and as clusters of pore-filling rhombs. (4) The Claymore Sandstone Member (early to middle Volgian) thick marine sandstone turbidites are interbedded with thin siltstones/shales. Sandstones have well-developed quartz, K and Na-feldspar overgrowths, and kaolinite and illite-smectite occur as grain replacements and rarely as pore fills. Late-diagenetic dolomite and ferroan dolomite form poikilotopic cement and clusters of pore-filling rhombs. The major factors which control diagenetic features are depositional environment and associated porewater together with original mineralogy. Burial history and textural features of the sandstones also have important influences. Reservoir quality is controlled by a complex interplay of these features.

Im klassischen Lössprofil von Stillfried an der March wurden in der oberen Humuszone des Stillfrieder Komplexes Mineralbestand und Mikrogefüge mittels Röntgendiffraktometeranalyse und Rasterelektronenmikroskopie untersucht. In der Schluffund Tonfraktion fand sich neben anderen Tonmineralen Palygorskit, der vor allem in Form feinstrukturierter Mineralanhäufungen über Karbonatknollen auftritt.

Die charakteristische Morphologie der dünnstengeligen und faserförmigen Einzelkristalle sowie die Bildungsbedingungen bei alkalischem Milieu und hohem Mg-Gehalt der Bodenlösung sprechen für eine pedogenetische Neubildung des Palygorskit.

The principal methods for studying clay minerals in andosoils differ especially by the succession of the pretreatments, i.e. differential dissolution of amorphous mineral cements before (first method) or after (second method) the dispersion and recovery of granulometric fractions.

The first method permits a rapid total quantitative estimation of amorphous components and an accurate identification of crystallized clay minerals by means of X-ray diffraction. The second method only proves the presence of allophane and imogolite.

The two methods were applied in two different laboratories on the same soils from the Massif Central. The comparison of the results emphasizes the profit of using the two methods, especially if hypotheses on the mechanisms of clay genesis are to be proposed.

These results, if placed in the context of a more comprehensive study, suggest the existence of two principal phases of clay genesis, strongly connected to the evolution of organic matter in andosoils, as follows: (i) an early, prepedologic phase during which halloysites and smectites would form; (ii) a late phase giving rise especially to some kaolinite and gibbsite.

The kaolin deposit at the Adelita mine, located in the province of Rí;o Negro (Patagonia, Argentina), was studied. Petrographic studies on thin sections and chemical analyses of major, minor and trace elements on bulk samples were carried out. The kaolin content of the rock ranges from 31% to 65%. The mineralogy of the working front, which is about 45 m thick, varies from the upper zone, where the rock is strongly silicified, stained with iron oxides and carbonated, grading downwards to a kaolinized zone, with a quartz-kaolinite-dickite assemblage with relict lithic particles and a smaller amount of iron oxides, and ending in the deepest zone where dickite, alunite, diaspore, quartz and scarce associated kaolinite occur.

The kaolin mineralogy was determined by SEM, XRD, DTA-TG, IR and δ18O and δD isotope analyses. The S, Ba and Sr contents are enriched during hydrothermal alteration, whereas Cr, Nb, Ti and lanthanide elements are concentrated mainly during weathering. The (Ba+Sr) concentrations in the samples studied vary between 600 and 6000 ppm and (Ce+Y+La) between 2 and 150 ppm; (Cr+Nb) remains constant for all the samples, whereas (TiO2+Fe2O3) is below 0.3%. In the hypogene deposits P2O5 is also more abundant and increases with the degree of alteration. Chondritenormalized rare earth element diagram shows a marked enrichment in LREE relative to HREE, with negative europium anomalies and D18O values range between 3.8‰ and 7.7‰ and δD between –123‰ and –103‰, suggesting that kaolin formed from the hydrothermal alteration of rhyolitic tuffs.

A study has been made of the influence of adsorbed alkylammonium ions on the water sorption and swelling of Na+ and Ca++ montmorillonite, under controlled conditions of temperature and suction. The water uptake and extensive crystalline swelling of Na+ montmorillonite decrease as the proportion of exchangeable alkylammonium/ammonium ions increases. This decrease is more associated with the degree of surface coverage than with the degree of saturation of the exchange sites by the alkylammonium ions. These observations are explained in terms of binding of the organic cation by the clay surface and the collapse of diffuse double layers on interlamellar surfaces. Differences in water uptake betwen complexes saturated with different alkylammonium ions are attributed to differences in the structural arrangement of the clay crystals in the swollen state. Similarly, there is a continual slight decrease in the water uptake and swelling of Ca++ montmorillonite as the amount of alkylammonium ions present increases. However, for alkylammonium ions containing less than five carbon atoms and when only about half of the exchangeable Ca++ ions have been replaced by the organic ions, extensive crystalline swelling sometimes takes place. When this occurs, it is suggested that the alkylammonium ions disrupt the regularity of the water network initially associated with the Ca++ ions, enabling these to participate in the formation of diffuse double layers in the interlamellar space.

The uptake of Ba2+ and K+ by a synthetic Na-phyllomanganate has been studied by chemical analysis, X-ray diffractometry and X-ray photoelectron spectroscopy. The changes in basal spacing arising from cation exchange have been used to monitor the progress of the exchange reaction and confirm the selectivity measured by bulk chemical analysis. However, the selective uptake of Ba2+ over Ca2+ is much greater than that of K+ over Na+ and it is suggested that charge distribution in the interlayer is important. The results are discussed in the light of recent advances in our understanding of the phyllomanganate structure.

Une vermiculite-M (M = Na,K) sous la forme de macrocristaux gonflés à l'eau, de 1 à 4 mm2, adsorbe par échange d'ions des colorants cationiques en solution aqueuse. La sélectivité de cette vermiculite-M pour ces cations est très faible et sa teneur ne dépasse pas 7% de la capacité d'échange de cations.

Les spectres d'absorption visible des vermiculite-(M,colorant) obtenues, comparés à ceux des cations colorant en solution aqueuse, montrent dans le cas des cations bleu de méthylène, bleu de Nil A et vert brillant un déplacement de l'ordre de 25 nm de l'une des bandes. Du fait de l'adsorption, la charge des cations colorant adsorbés est plus localisée, soit sur leurs hétéroatomes centraux (bleu de méthylène), soit sur leurs hétéroatomes périphériques (vert brillant). La spectrométrie infrarouge ne contredit pas ces résultats.

Les vermiculite-(M,colorant) ne sont pas des pigments colorés et l'utilisation de la vermiculite comme support de colorants est très limitée.

Clay minerals have been prepared by synthesis in solutions of comparable strength to their solubility (10–20 mgm./l). Syntheses have been carried out in boiling water and at normal temperatures, at various pH's, and with various components; the products have been examined with X-rays and the electron microscope. In general it is found that the proportion of the components has only a small effect on the product, this being determined mainly by the pH. The low temperature gives less crystalline products. Some results are:

Si-Mg syntheses.—Montmorillonite: “crushed paper” type at pH 9 (Fig. 1); “star” type at pH 8 (Fig. 2 from boiling solutions, Fig. 3 at ordinary temperature).

Si-Mg-Al syntheses.—Al as aluminate at pH 8 gives montmorillonite; with more Al, “swelling chlorite” (and 7Å mineral?) (Fig. 4). With cationic Al at pH 8·5 a filmy, almost amorphous product (sepiolite?) (Fig. 5); at pH 7·7 boeh-mite (Fig. 6). Anionic Al with KCl in great excess gives micas (Fig. 7).

Syntheses with iron.—Iron-rich saponites, montmorillonite minerals, and Fe2O3+“swelling chlorite” have been obtained. In NaCl excess, mica-like (but isotropic, poorly crystalline) products (Fig. 8).

The authors consider that the brucite-gibbsite layer forms first in these syntheses, and the silicate layer attaches itself to it: analogous products have been made with aluminate and chromate in place of silicate.

The quantitative interpretation of the reflection intensities of the SAED patterns of glauconites reveals the mechanism of migration of the octahedral sheet cations during heating up to 750°C. It confirms that Mg2+ has a greater ability than Fe3+ to migrate from cis-to trans-sites, as previously found by means of XRD pattern modelling. For samples heated to 650°C, the two formerly vacant trans-sites in the base-centred unit-cell become occupied, but differently, which leads to a primitive unit-cell, and the cis-sites remain filled almost entirely by Fe3+ only. The cation migration occurs through the nearest shared edges in the [010] and [310] directions. The samples heated to 750°C reveal a base-centred super-cell with A = 3a and B = b. All Mg cations leave the cis-sites to occupy completely four of the six available trans-sites of the super-cell. Migration also occurs through the shared edges in the [010] and [310] directions. The primitive unit-cell is not an intermediate step in the migration process leading to the super-cell. The existence of additional satellites in the SAED patterns of some crystals heated to 750°C corresponds to the existence of antiphase domains with a 3b/2 width and an antiphase shift of a/2.

The morphological and structural changes in smectite caused by hexadecyltrimethylammonium (HDTMA) treatment were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The HDTMA-exchanged smectite shows not only morphological features such as irregular, wavy surface with curled edges, but also structural features such as large d-spacings (20 – 26 Å ) and lattice distortions. The surface morphological heterogeneity is assumed to be related to the inhomogeneous intercalation of HDTMA cations into the interlayer of smectite.

Iranian montmorillonite (MMT) was modified with hexadecyltrimethylammonium bromide (HDTB) and used as a nano-additive for the enhancement of the mechanical and anticorrosion properties of an epoxy coating. Infrared (IR) spectroscopy, thermo-gravimetric analysis (TGA), transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis indicated that HDTB reacted with MMT (with 97% yield) and increased the d001 spacing of MMT from 1.27 to 3.92 nm. Some 1, 3 and 5 wt.% of organically modified montmorillonite (OMMT) were added to the epoxy coating formulation. XRD and TEM/image processing analysis showed that the extent of intercalation/exfoliation of OMMT was substantially greater than that of MMT. Dynamic mechanical analysis showed that the glass transition temperature and storage modulus increased significantly with the addition of OMMT. Electrochemical impedance spectroscopy (EIS) and salt spray/image processing results revealed that addition of OMMT to the epoxy coating significantly increased the corrosion resistance of the coating compared to neat and MMT-containing epoxy coatings. The optimum concentration of OMMT was 3 wt.%. At this concentration, the mechanical and anticorrosion properties were greatly superior to those of neat and MMT-containing epoxy coatings.

Porous clay heterostructures were prepared from Al-intercalated clays, and they allowed the insertion of Al into the framework of intercalated silica in porous clay heterostructures (PCHs). This method has led to tuneable Al contents within the resulting porous clay heterostructures. X-ray fluorescence confirmed the presence of Al in the intercalated precursors and their derivatives (porous clay heterostructure materials) in various environments, as indicated by 27Al magic-angle spinning nuclear magnetic resonance. The Al porous clay heterostructures exhibited specific surface areas that varied from 743 to 850 m2/g with total acid concentrations which varied from 0.969 to 1.420 mmol of protons/g of material, values which were deduced from the temperature desorption of cyclohexylamine. These acid sites were sufficiently strong to initiate the hydro-isomerization of n-heptane. The catalytic properties of the porous clay heterostructures depended on the Al contents and reached a maximum conversion rate of 50% and an isomer selectivity of 70% at a test reaction temperature of 350°C.