Swelling of clay

The problems caused by shales in petroleum activities are not new. At the beginning of the 1950s, many soil mechanics experts were interested in the swelling of clays. It is important to maintain wellbore stability dining drilling, especially in water-sensitive shale and clay formations. The rocks within these types of formations absorb the fluid used in drilling this absorption causes the rock to swell and may lead to a wellbore collapse. The swelling of clays and the problems that may arise from these phenomena are reviewed in the literature [528,529,1788,1900]. Various additives for clay stabilization are shown in Table 3-1. 

Inhibitors of swelling act in a chemical manner rather than in a mechanical manner. They change the ionic strength and the transport behavior of the fluids into the clays. Both the cations and the anions are important for the efficiency of the inhibition of swelling of clays [503]. 

The reactivity of steam can be reduced via pH control. The injection or addition of a buffer such as ammonium chloride inhibits the dissolution of certain mineral groups, controls the migration of fines, inhibits the swelling of clays, controls chemical reactions in which new clay minerals are formed, and... 

I. Suratman. A Study of the Laws of Variation (Kinetics) and the Stabilization of Swelling of Clay (Contribution a U etude De La Cinetique et De La Stabilisation Du GonflementDesArgiles). PhD thesis, Malaysia, 1985. 

Acids were an early exception to the no water rule. It was recognized that aqueous solutions of acids would inhibit swelling of clays and shales as well as dissolve any acid-soluble minerals contained in a formation. By 1933 commercial well stimulation with hydrochloric acid was of great interest. A whole separate methodology and treatment chemistry has since evolved around acidizing and fracture acidizing(54). Water emulsions, mainly emulsified acids, and gelled acids thickened with polymeric additives were applied early in the history of well treatment. 

Solutions of TKPP have been shown to have unique and advantageous properties for use in formulating a wide variety of well fluids. Its reasonable cost, worldwide availability, and nontoxic properties make it a preferred additive for use in many petroleum applications. It has been shown to be a most effective salt with respect to inhibiting hydration and swelling of clay minerals commonly encountered in drilling operations and/or reservoirs. Avoiding clay problems is the major impetus for the incorporation of potassium ions in well fluids, and the use of TKPP provides advantages over and above those available from other potassium salts. 

The catalytic application of clays is related closely to their swelling properties. Appropriate swelling enables the reactant to enter the interlamellar region. The ion exchange is usually performed in aquatic media because the swelling of clays in organic solvents, and thus the expansion of the interlayer space, is limited and it makes it difficult for a bulky metal complex to penetrate between the layers. Nonaqueous intercalation of montmorillonite with a water-sensitive multinuclear manganese complex was achieved, however, with the use of nitromethane as solvent.139 The complex cation is intercalated parallel to the sheets. 

Lim CH, Jackson ML, Koons RD, Helmke PA (1980) Kaolins Sources of differences in cation exchange capacity and cesium retention. Qays Clay Miner 28 223-229 Low PE (1981) The swelling of clay III Dissociation of exchangeable cation. Soil Sci Soc Amer J 45 1074-1078... 

The swelling of clays in water results from the extra hydration of the interlamellar cations (Fig. 77). This is the best known example of the important phenomenon of intercalation, which is simply the insertion of guest species into an accommodating host, usually, but not exclusively, a layered solid. The degree of swelling, however, is governed by the nature of the interlamellar cation and the sorption isotherm often exhibits steps, as so often occurs with clathrates. 

For many systems this is indeed observed. There are, however, important exceptions. One such exception is the swelling of clay [159-161], In the presence of water or even water vapor, clay swells even at high salt concentrations. This cannot be understood based on DLVO theory. To understand phenomena liken the swelling of clay we have to consider the molecular nature of the solvent molecules involved. 

Brown, K.W. Shrinking and Swelling of Clay, Clay Strength, and Other Properties of Clay Soils and Clays in Minerals in Soil Environments, Dixon, J.B. Weed, S.B., Eds., Soil Sd. Soc. Amer. Madison, 1977, pp. 689-707. 

Morgenstem, N. R., and Balasubramonian, B. I. (1980). Effects of pore fluid on the swelling of clay shale. In 4th International Conference on Expansive Soils, pp. 190-205. Denver. 

The swelling of clays is a two-step process. First, hydration of the platelet surface occurs, leading to a slight volume increase. Second, repulsion takes place between the electric double layers, leading to the complete separation of the platelets this is so-called osmotic swelling. 

Delville, A. 1992. Structure of liquids at a solid interface An application to the swelling of clay by water. Langmuir 8 1796-1805. 

Karabomi, S., B. Smit, W. Heidug, J. Urai, and E. van Oort. 1996. The swelling of clays Molecular simulations of the hydration of montmorillonite. Science (Washington, DC) 271 1102—1104. 

The permeability reduction may be due to the dislodging of fine particles and subsequent trapping in pore restrictions, or the swelling of clay particles, or both. 

The swelling of clays in water represents an example in which the internal osmotic pressure is associated with double-layer repulsion between the clay platelets. 

The particles plucked out of the rock skeleton by fluid flow and the swelling of clay materials may block pore throats, locally increase the pressure gradient, and thus increase the destabilizing force. 

I. Ravina and D. Zaslavsky, Nonlinear electrokinetic phenomena. Part II Experiments with electrophoresis of clay particles. Soil Sci. 106 94 (1968). I. C. Callaghan and R. H. Ottewill, Interparticle forces in montmorillonite gels, Faraday Disc. Chem. Soc. 57 110(1974). P. F. Low, The swelling of clay. Ill Dissociation of exchangeable cations, Soil Sci. Soc. Am. J. 45 1074 (1981). 

There are various hypotheses explaining this aggregate expansion mechanism. The most wide spread refer to the swelling of clay minerals and of osmotic pressure formation [141,142]. All these hypotheses agree that this phenomenon relates to the reaction of soluble alkalis from cement with the aggregate leading to the decomposition of dolomite ... 

The chemical activity of the clay is due to its surface electrical charge, which causes the attraction and adsorption of mainly positive ions, such as hydrogen ions, exiting in water, or calcium, or sodium ions. The swelling of clay in the presence of water is due to the attraction of hydrogen ions. The stabilisation of clay, however, is due to the attraction of calcium or sodium ions. 

Several methods including melt compounding, solution-based process, and in-situ polymerization could be used for the preparation of PET/clay nanocomposites. In-situ polymerization involves swelling of clays in a liquid monomer, or a monomer solution, followed by polymerization initiated thermally or by the addition of a suitable compound in the presence of intercalated/exfoUated days. It is considered as one of the best methods to produce polymer nanocomposites based on day because relativdy small-sized monomers could be easily intercalated into day layers before polymerization. Then, further polymerization between days could easily lead to weU-dispersed clay in the polymer matrix. Furthermore, day could be added into the redpe for the polymerization process thus, no further process is needed to reahze industrial application. 

Lessivage. Lessivage involves the vertical transport of particles and colloids of clay minerals. The downward horizons where the accumulation of the transported clays occurs are called argillic (denoted B,) horizons. Usually, due to the swelling of clay minerals with water, the plugging of argillic horizons ensures an impermeabilization of lower horizons. 

Nevertheless, immersion calorimetry is unique in that it is the only method that is able to detect the enthalpic interaction between a bare surface and a solution. Further, the method can be applied advantageously to study adsorption phenomena on fine powders, including the swelling of clays. 

The existence of a short-range (<4 nm) repulsive pressure was first observed in experiments on the swelling of clays [531,532] and on the stabilization of foam films [533]. This short-range repulsion has been called the hydration force [534], The school of Derjaguin terms this effect structural component of disjoining pressure [535]. Indications for its action were found in measurements... 

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