Active Clay Minerals Research Articles

STUDY OF DEPENDENCE BETWEEN CLAY MINERAL DISTRIBUTION AND SHALE VOLUME IN RESERVOIR ROCKS USING GEOSTATISTICAL AND PETROPHYSICAL METHODS

Identify and obtain a detailed understanding of shale and its clay minerals in three segments; exploration, drilling and reservoir in the oil industry are very important. The study of the formation clay minerals in terms of depth and layers of earth is done through X-ray tests on samples taken from the reservoir which in comparison with logging requires a lot more time and cost and also can't provide continuous results because continuous sampling from the whole well is not possible. NGS (Gamma-ray Spectrometry) log is used to identify formation clay minerals that is an indicator of three radioactive elements thorium, uranium and potassium and the amount of each of these elements and according to amount of each of these elements and their ratio gives a description of clay minerals of each zone. CGR log represents the sum of two elements Thorium and potassium that are present in the shale and uranium has no effect on it. The CGR log is usually used as a shale indicator and it is an essential tool for determining the Shale volume in well logging operation. In this study the relationship between shale volume shown by the CGR log and the type of formation clay mineral was investigated. A very clear relationship between the shale volume and formation clay minerals was observed. In intervals with low shale volume the amount of active clay minerals, especially montmorillonite was higher and in intervals with high shale volume, inactive clay minerals were more. In order to investigate the spatial relation between the logging data, frequency distribution and correlation between logging data was studied. By using logging data and identifying the type of clay minerals in each zone and also the spatial correlation between logging data a suitable program for drilling and exploitation of oil fields in different areas can be proposed.

Mechanical behaviour of unsaturated expansive clay under K0 conditions

The mechanical response of unsaturated soils with significant amounts of active clay minerals can be highly stress path dependent. Traditionally, the Axis Translation Procedure has been used to study these materials in the laboratory. This technique, however, does not fully replicate conditions in the field, nor is it able to test soils during the important process of desaturation and resaturation. A novel osmotic oedometer has been developed at Imperial College London to test unsaturated soils under atmospheric pressure. With this equipment, it has been possible to continuously record changes in vertical and radial stress, gravimetric water content, degree of saturation, matrix suction, and void ratio, throughout a test. The Paper presents results from tests carried on samples of compacted London clay using the new oedometer and standard oedometers. The full data set gives an insight into the mechanical response of unsaturated expansive clay along complex stress paths. Results are interpreted using an existing framework for unsaturated expansive clays. Because of inherent limitations in the method of testing, some of the data needs to be interpreted with care. Nevertheless, the response recorded along different stress paths was found to be consistent and in agreement with framework predictions.

Electrochemical investigation on steel corrosion in iron-rich clay

The iron-rich clay mineral, such as the red soil, is found corrosive toward pipeline steel, which may partly attribute to the active Fe oxide constituents residing in the clay. Surface charge and electrokinetic properties of the red clay mineral were characterized and related to corrosion behavior of X80 steel in the soil. Results show that surface charge of the Fe-rich clay mineral is variable according to pH. Active clay minerals, especially Fe oxides, distinctly influence corrosion process of the steel. The dynamic redox cycle of Fe oxides promotes and sustains corrosion of the steel in contact with iron-rich clay environments.

Pyrite Formation in Organic-rich Clay, Calcitic and Coal-Forming Environments

Abstract The early diagenetic characteristics of pyrite formation processes in a Miocene freshwater sequence of mixed sediments (coal fragments in clays, sandstones or shales) alternating with continuous brown coal layers was investigated. Based on abundant minerals, the following main sedimentary environments were distinguished: the illite-montmorillonitic (I-M), calcitic (Ct) and coal-forming environment (CL). For these hydrogeochemically differing environments the effects of limiting factors on the pyrite formation process (availability of sulphate and Fe, amount of organic matter and participation of organic sulphur) were assessed by correlation analysis. Significant differences in the effects of these limiting factors in the particular environments were observed. These differences were explained taking in account the different oxidative activity, Fe-complex and surface complex forming properties of humic substances in dependence of pH of environment and the abundance of sorptionally active clay minerals. In environments having a relatively low pH and containing clay minerals (I-M-and CL-environments) the oxidative activity of humic substances (Hs) on pyrite precursors was greatly prevented however pyrite formation depended on reactive Fe availability as the consequence of complex formation. On the contrary, in environments with a relatively high pH, as it was the calcitic, the oxidative activity of Hs was greatly enhanced, thus oxidizing the sulfur precursors of pyrite. The oxidation degree of organic matter was probably also a consequence of the differing activity of the humic electron-acceptors.

Physical and geotechnical properties of clay phyllites

An experimental programme is presented with the aim of characterising – from physical, microstructural and geotechnical perspectives – the main properties of compacted clay phyllites. These clay phyllites are widely used as waterproofing material for roofs in the Alpujarra (Andalusia, Spain), as sealing liners in irrigation ponds, and as core material of small earthen zoned dams. An exhaustive physical-characterisation programme on the powder fraction has been followed using X-ray fluorescence (XRF), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), chemical analysis by energy dispersive X-ray spectroscopy (EDX), thermal analysis, particle-size distribution analysis, consistency limits, and density of solid particles. From a microstructural standpoint, mercury intrusion porosimetry (MIP) tests, as well as nitrogen-adsorption tests, were carried out to characterise the pore network and surface area of the material in both natural and compacted states. The geotechnical characterisation programme on the compacted material was focused on the water-permeability and water-retention properties, the volume change on soaking (swelling or collapse), the compressibility on loading, the shear-strength properties, and the mechanical-penetration properties. In this way, an important physical and hydro-mechanical data base is provided, which could help in evaluating the suitability for using this material in a wide range of earthen constructions (liners, road subgrades, embankments, core material in zoned dams). It has been found that the material contains illite, chlorite and quartz as the main components, and feldspar, iron oxide and interstratified illite–smectite as minor ones. Despite the presence of active clay minerals, the compacted material did not display an important swelling on soaking at low stresses, as a consequence of its low specific surface and low water-retention ability. The material exhibited good compaction properties and, consequently, low water permeability plus a stiff response on loading. Nevertheless, despite the low porosity attained on the dry-side compaction, the material underwent some collapse on soaking at stresses greater than 100 kPa.

Equilibrium modeling for the adsorption of methylene blue from aqueous solutions on activated clay minerals

This work reports the application of an activated clay mineral as adsorbent for the removal of a basic dye, methylene blue (MB), from aqueous solutions. The thermal treatment at 300°C for 2h and the acid activation with nitric acid of 0.5mol/dm3 under reflux conditions improve the adsorption capacity of the raw clay mineral. A maximum of 500mg/g of MB at equilibrium is achieved. Equilibrium data are mathematically modelled using the Freundlich, Langmuir and Toth isotherm adsorption models.

A double structure generalized plasticity model for expansive materials

AbstractThe constitutive model presented in this work is built on a conceptual approach for unsaturated expansive soils in which the fundamental characteristic is the explicit consideration of two pore levels. The distinction between the macro‐ and microstructure provides the opportunity to take into account the dominant phenomena that affect the behaviour of each structural level and the main interactions between them. The microstructure is associated with the active clay minerals, while the macrostructure accounts for the larger‐scale structure of the material. The model has been formulated considering concepts of classical and generalized plasticity theories. The generalized stress–strain rate equations are derived within a framework of multidissipative materials, which provides a consistent and formal approach when there are several sources of energy dissipation. The model is formulated in the space of stresses, suction and temperature; and has been implemented in a finite element code. The approach has been applied to explaining and reproducing the behaviour of expansive soils in a variety of problems for which experimental data are available. Three application cases are presented in this paper. Of particular interest is the modelling of an accidental overheating, that took place in a large‐scale heating test. This test allows the capabilities of the model to be checked when a complex thermo‐hydro‐mechanical (THM) path is followed. Copyright © 2005 John Wiley & Sons, Ltd.

Clay mineral characterization through the methylene blue test: comparison with other experimental techniques and applications of the method

This article illustrates an experimental study of clay mineral characterization conducted with the aid of the methylene blue "stain" test, which yields a semiquantitative evaluation of the activity of a geomaterial based on the type and quantity of clay minerals contained in it. The properties of clay minerals are described briefly, with special regard to their swelling behaviour in the presence of water. The testing method is described with reference to the procedures and interpretation criteria specified in the Association française de Normalization (AFNOR) and American Society for Testing and Materials (ASTM) standards. The results are then presented of a testing campaign conducted to assess the applicability of the methylene blue test for the characterization of geomaterials through a comparison with other testing methods. Additional tests were performed on stratigraphic sequences to identify the levels containing higher proportions of active clay minerals, based on their tendency to swell on coming into contact with water. This characterization technique was applied to marly–arenaceous formations of the Langhe region (Piedmont, Italy), where planar sliding instability phenomena have often been observed following abundant rainfall, and marly–arenaceous formations of Monferrato (another region in southeast Piedmont, Italy), where studies of a geological–structural nature have often revealed traces of postsedimentary tectonic phenomena.Key words: methylene blue stain test, marl, clay mineral, swelling phenomenon, planar sliding instability.

Settling Behaviour and Clay Mineralogy

Sedimentary soils are formed due to the process of settling of soil particles in suspension. The settling process is physico-chemical in nature as the soil contains chemically active clay minerals. The extent to which the clay mineralogy affects the settling process depends upon the initial water content of the soil-water suspension. For montmorillonitic soils, the limiting water content at which the nature of settling changes from a discrete free type to a flocculated free type increases with an increase in the soil plasticity and decreases with an increase in the soil plasticity for kaolinitic soils. While the diffuse double layer repulsion controls this kind of behaviour of montmorillonitic soils, the behaviour of kaolinitic soils can be attributed to the fabric effect.

The relationship between suction and swelling properties in a heavily compacted unsaturated clay

In order to study the hydro-mechanical behaviour of highly compacted unsaturated clays used in engineered clay barriers for nuclear waste disposal, some experimental techniques for controlling suction were extended into the range of high suctions. The technique of control by imposing a given relative humidity was considered for very high suctions (several hundreds of MPa), and calibration data from the literature were examined. Some corrected values were proposed, based on a calibration made with sodium chloride. The extension of the osmotic technique to higher suctions was made, and a value of 10MPa was attained, enlarging considerably the range of this method. The study of the water retention and swelling properties of the FoCa7 clay under controlled suction and zero applied stress is presented. A good continuity between the two methods of suction control was observed. Fairly reversible responses to suction cycles were observed, in terms of water content and volume change. During these changes, it was observed that the air volume remained constant. The reversibility is related to the predominant role of a saturated microstructural level, strongly influenced by the physico-chemical bonds existing between water and the active clay minerals.

Evolution model and formation mechanism of bio-thermocatalytic transitional zone gas

As a new genetic type of natural gas exploration area, the bio-thermocatalytic transitional zone gas (BTTZG) has been highly stressed by geologists both at home and abroad. Systematic study on the generation mechanism of hydrocarbon at the transitional zone is presented. Based on simulating experiments and geochemistry analysis of the source rock with lower evolution, a hydrocarbon-forming model at the transitional zone has been established. The mechanism is proposed that under the condition of low temperature and pressure combining with extremely active structural stress and clay mineral catalysis, BTTZG is formed by de-group of soluble organic matter and polarized compositions through orthocarbon ion as well as by condensation polymerization of aromatic ring-rich insoluble organic matter. This mechanism controls the formation of BTTZG, and furthermore, BTTZG is the product of superimposition and interaction of all the factors mentioned above.

Selective Friedel–Crafts Alkylation on a Vermiculite, a Highly Active Natural Clay Mineral with Lewis Acid Sites

Abstract Acid-catalyzed Friedel–Crafts alkylation reactions of p-methylbenzyl chloride with benzene were carried out on four unmodified natural clay minerals. Phenyl-p-tolymethane was quickly and selectively formed in the presence of vermiculite. Although the specific surface area of vermiculite is smaller than those of the other clay minerals examined, such a characteristic property of vermiculite as a catalyst may be attributed to the absence of Brønsted acid sites and to the Lewis acid sites on the outer surface of vermiculite.

The mechanism of β‐ Carotene adsorption on activated montmorillonite

AbstractsThe variations in the structure of mineral during adsorption have been examined comparing the results of X‐ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetry (TG) and infrared (IR) spectroscopy of the acid activated montmorillonite clay mineral before and after adsorption of β‐carotene. Based on the results, it was concluded that β‐carotene attaches to the clay surface in the form of carbonium ions either by forming hydrogen bonds with Brönsted sites or by forming coordination bonds with Lewis sites of the activated clay mineral.

ChemInform Abstract: The Nature of the Thermal Decomposition of a Catalytically Active Anionic Clay Mineral.

AbstractThe changes occurring during heat activation of synthetic hydrotalcite, Mg6Al2(OH)16CO3 · H2O, have been studied by 27Al MAS NMR, Auger and XPS spectroscopy, TEM, and high resolution nitrogen desorption techniques.

The nature of the thermal decomposition of a catalytically active anionic clay mineral

Certain synthetic, anionic clays, after a carefully controlled heat activation, have been shown to promote a wide variety of base catalyzed reactions such as aldol condensations, oxirane polymerizations, carbon-bound HD exchange, and lactone polymerizations. The changes which take place during the heat activation of such a synthetic, anionic clay mineral, hydrotalcite (Mg 6Al 6(OH) 16 (CO 3 · 4H 2O), have been studied by 27Al nuclear magnetic resonance-magic angle spinning, Auger and XPS spectroscopy, transmission electron microscopy, and high resolution nitrogen desorption techniques. The heating of this material (to ~450 °C) results in the loss of interstitial water, carbon dioxide, and dehydroxylation until a catalytically active material analyzing approximately as Mg 6 Al 2O 8(OH) 2 remains. This heating does not cause a change in the crystal morphology nor in exfoliation of the layered structure. Instead, numerous fine pores (20–40 Å radius) form perpendicular to the crystal surface from which the gases vent. This is accompanied by an increase in the surface area from about 120 to about 230 m 2/g (N 2/BET) and a doubling of the pore volume (0.6 to 1.0 cm 3/g, Hg intrusion). The bulk aluminum changes from all octahedral to about 20% tetrahedral-80% octahedral. Auger spectroscopy did not appear to indicate changes in the surface aluminum environment. The X-ray powder pattern changes from that of a diffuse hydrotalcite to a very poor magnesium oxide pattern.

On the Swelling Behaviours of the Artificially Crushed Tertiary Mud-stones

In this paper the property of free swelling of artificially crushed Tertiary (Kobe, Tsuyama and Mizunami group) mudstone is discussed. The degrees of free swelling depend on the the content of active clay minerals, such as montmorillonite and vermiculite, and the water contents are decided with pF value which is determined by soil suction, i.e. The results show that the degrees of free swelling are in proportion to the content of montmorillonite minerals in a soil and the water contents at a certain soil suction except Mizunami group mudstones.

Electrolyte Concentration-Permeability Relationships in Sodium Illite-Silt Mixtures

AbstractTo examine the effects of clay swelling and dispersion on electrolyte concentration-permeability relationships of low clay content soils, flow experiments were conducted on a silt of fixed particle size distribution containing 0, 5, 7·5, 10 and 15 per cent clay (sodium illite, 2 μm fraction). Flocculated specimens were sedimented using both slow and rapid procedures. After compression each specimen was permeated successively with electrolyte solutions which caused (1) swelling of the clay fraction (0·10 N), and (2) dispersion (0·05 N). Absolute permeabilities varied with clay content, sedimentation procedure, compression rate, and electrolyte concentration; however, the form of this variation plotted against through-put volume was similar for all specimens containing electrolyte solutions causing only swelling of the clay. Increasing the hydraulic gradient above a critical value apparently increased the swelling slightly as evidenced by further reductions in permeability. The permeability of mixtures permeated with electrolyte solution causing dispersion of the clay was more complex and depended on clay content, the hydraulic gradients used to introduce the dispersing electrolyte solution and the pre-dispersion gradients to which the specimens had been subjected. Permeability decreases were attributed to the last stages of swelling prior to dispersion and to pore plugging. Increases in permeability were the result of erosion of dispersed particles. Specimens previously subjected to the highest gradients while swelling dispersed more rapidly and had a greater tendency to erode. The effects of predispersion gradients diminished with increasing clay contents. It is concluded that both compositional and mechanical factors play an important role in determining electrolyte concentration-permeability relationships for soils containing active clay minerals.