No description available.

The thesis investigates the behaviour of aqueous montmorillonite suspensions and also the interactions between montmorillonite as a free standing film and in highly dispersed aqueous suspension with water soluble polymers used as additives in water based drilling fluids. FTIR microscopy and FTIR ATR spectroscopy have been employed to study in-situ dehydration of fully dispersed aqueous montmorillonite suspensions. The IR spectrum of the dispersed bentonite shows significant differences from that of a dry bentonite powder, which have been attributed to the hydration of the exchangeable cation. Drying, or concentrated salt solution causes the differences to disappear and this is attributed to the exchangeable cation settling back to its ditrigonal cavity in the silicate sheet of the mineral under these conditions. The adsorption of various molecular weights of neutral polyacrylamide (PAM) onto montmorillonite has been studied using FTIR transmission, ATR spectroscopy and XRD. Shifts seen in the NH[2] stretching and bending bands have been interpreted as being due to H-bonding with the outer co-ordination sphere of exchangeable cations. KCl has shown to have some influence on this system. Another neutral polymer used extensively in water based drilling fluids is polyalkylglycol (PAG). The adsorption of two molecular weights of this polymer from aqueous solutions of various concentrations have been monitored both in the presence and absence of KCl. The physical form of the montmorillonite (either as a free standing film or as a dispersed suspension), the concentration of the polymer solution, the polymer molecular weight and the presence of KCl all have significant effects on the adsorption of polymer. The stabilisation of montmorillonite films by PAG and PAG/KCl solutions has been monitored by ATR spectroscopy, and the dehydration of these films by polymer has been monitored using FTIR spectroscopy and XRD. The interaction of PAG is thought to be via hydrogen bonding with the innermost co-ordination sphere of the exchangeable cations which thus presents a hydrophobic surface to solvent molecules, preventing the film from collapse. Since all water based drilling fluids are multi-component systems, techniques previously used have been employed to study the competitive adsorption of the polyalkylglycol and polyacrylamide components. Preferential adsorption of the PAG is seen in these systems either due to the mass transport effects (PAG is considerably smaller than PAM) or due to PAG removing all but the inner cation hydration sphere, and presenting a hydrophobic surface for the PAM, and therefore preventing its adsorption.

Designing a fit-for-purpose drilling fluid for high-pressure, high-temperature (HP/HT) operations is one of the greatest technological challenges facing the oil and gas industry today. Typically, a drilling fluid is subjected to increasing temperature and pressure with depth. While higher temperature decreases the drilling fluid’s viscosity due to thermal expansion, increased pressure increases its viscosity by compression. Under these extreme conditions, well control issues become more complicated and can easily be masked by methane and hydrogen sulfide solubility in oil-base fluids frequently used in HP/HT operations. Also current logging tools are at best not reliable since the anticipated bottom-hole temperature is often well above their operating limit. The Literature shows limited experimental data on drilling fluid properties beyond 350°F and 20,000 psig. The practice of extrapolation of fluid properties at some moderate level to extreme-HP/HT (XHP/HT) conditions is obsolete and could result in significant inaccuracies in hydraulics models. This research is focused on developing a methodology for testing drilling fluids at XHP/HT conditions using an automated viscometer. This state-of-the-art viscometer is capable of accurately measuring drilling fluids properties up to 600°F and 40,000 psig. A series of factorial experiments were performed on typical XHP/HT oil-based drilling fluids to investigate their change in rheology at these extreme conditions (200 to 600°F and 15,000 to 40,000 psig). Detailed statistical analyses involving: analysis of variance, hypothesis testing, evaluation of residuals and multiple linear regression are implemented using data from the laboratory experiments. I have developed the FluidStats program as an effective statistical tool for characterizing drilling fluids at XHP/HT conditions using factorial experiments. Results from the experiments show that different drilling fluids disintegrate at different temperatures depending on their composition (i.e. weighting agent, additives, oil/water ratio etc). The combined pressure-temperature effect on viscosity is complex. At high thresholds, the temperature effect is observed to be more dominant while the pressure effect is more pronounced at low temperatures. This research is vital because statistics show that well control incident rates for non- HP/HT wells range between 4% to 5% whereas for HP/HT wells, it is as high as 100% to 200%. It is pertinent to note that over 50% of the world’s proven oil and gas reserves lie below 14,000 ft subsea according to the Minerals Management Service (MMS). Thus drilling in HP/HT environment is fast becoming a common place especially in the Gulf of Mexico (GOM) where HP/HT resistant drilling fluids are increasingly being used to ensure safe and successful operations.

The main goal of drilling a horizontal well is to enhance productivity or injectory by placing a long distance drain-hole within the pay-zone. Poor drilling fluid design results in difficulties such as poor hole cleaning, excessive torque or drag, wellbore instability, stuck drill string, loss of circulation, subsurface pressure control, poor cement jobs, and difficulties associated with running electric logs and formation damage can result. Neither of the conventional chemical cleaning methods can overcome problems for filter-cake removal in long horizontal and maximum reservoir contact wells because of limitations such as the complex geometry of wells, non-uniform chemical distribution, low contact between cleaning fluids/filter cake, and high chemical reaction rate, especially at high temperatures. This study describes a novel self-destructing drilling fluid system. Filter cakes are formed from a formula of drilling fluid that have a mixture of solid acid precursor and particulate solid acid-reactive materials. Then in the presence of water, the solid acid precursor (polylactic acid) hydrolyzes and dissolves, generating acids that then dissolve the solid acid-reactive materials (calcite). It effectively stimulates the horizontal section right after drilling and eliminates acidizing, resulting in significant cost savings, and improves filter-cake removal, thus enhancing the performance of the treated wells. A series of experiments have been run in the lab to determine the efficiency of this new system. Properties of this drilling fluid are measured. Experiments on solid acid particle size showed that the best size-distribution of solid acid precursor and solid reactive material to make a self-destructing filter cake is fine particles of calcium carbonate used as weighting material with 150 microns polylactic acid as solid acid precursor. By comparison of the results of the experiments at different temperatures, 230 degrees F has been chosen as the best temperature for running experiments. The self-destructing drilling fluid systems need enough time for the solid acid to be hydrolyzed and therefore remove the filter cake. After 20 hours of contact with the water as the only cleaning solution, about 80 percent of the filter cake was removed. Calcite is found to be the dominant compound in the sample of remained filter cake, which was proved by x-ray diffraction tests. Secondary electron microscopy (SEM) results show the morphology of the remained filter cake sample and confirm the crystalline area of calcite.

No description available.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-18T15:15:54Z No. of bitstreams: 1 RAQUEL SANTOS LEITE - DISSERTAÇÃO PPG-CEMat 2014..pdf: 1921020 bytes, checksum: 963eb1edee3115174a9a06b4af8c7f59 (MD5) / Made available in DSpace on 2018-04-18T15:15:54Z (GMT). No. of bitstreams: 1 RAQUEL SANTOS LEITE - DISSERTAÇÃO PPG-CEMat 2014..pdf: 1921020 bytes, checksum: 963eb1edee3115174a9a06b4af8c7f59 (MD5) Previous issue date: 2014-08-27 / Os fluidos inibidos são empregados na perfuração de folhelhos hidratáveis para evitar que as argilas encontradas sejam hidratadas e causem prisão de ferramentas. O conhecimento das propriedades de filtração dos fluidos é importante durante a perfuração de poços, uma vez que o controle dessas propriedades garante menos problemas de perfuração e melhora a produtividade dos poços. Assim, este trabalho teve como objetivo estudar e aperfeiçoar as propriedades de filtração de fluidos aquosos, inibidos com sal de potássio isentos de cloro (citrato de potássio), visando sua aplicação na perfuração de formações argilosas e folhelhos hidratáveis e dispersivos. Para tanto, foram estudados fluidos de perfuração com e sem adição do inibidor citrato de potássio. Foram determinadas as propriedades reológicas (viscosidades aparente (VA) e plástica (VP), limite de escoamento (LE) e força gel (FG)), filtração (volume de filtrado (VF), spurt loss (SL), espessura de reboco (ER) e permeabilidade (k)) e o poder de inibição (ensaios de dispersibilidade e o teste de inibição de bentonita) dos fluidos estudados. De acordo com os resultados obtidos conclui-se que os fluidos estudados apresentaram comportamento pseudoplástico e a adição do citrato de potássio ao fluido não ocasionou mudança no comportamento pseudoplástico dos fluidos. Concluiu-se ainda, que o uso conjunto dos aditivos amido, CMC BV e calcita reduz de forma mais efetiva as propriedades de filtração dos fluidos de perfuração estudados e que as propriedades de filtração dos fluidos inibidos com citrato de potássio foram otimizadas, uma vez que os valores de VF obtidos foram inferiores ao do fluido tido como base. As formulações que apresentaram eficientes propriedades de filtração e inibição foram preparadas com altas concentrações de citrato de potássio. As mesmas apresentaram baixos valores de VF e menores valores de SL. / The inhibited fluids are used in drilling hydratable shales, to prevent found clays to be hydrated and cause stuck tools. The knowledge of the filtration properties of the fluids is important during drilling, since the control of these properties ensures less drilling problems and improves well productivity. This work aimed to study and improve the filtration properties of aqueous fluids inhibited with potassium salt chlorine-free (potassium citrate), for their application in drilling hydratable and dispersive clays and shales. For this purpose, the drilling fluids with and without addition of the inhibitor potassium citrate were studied. It was determined the rheological properties (apparent viscosity (AV), plastic viscosity (PV), yield limit (YL) and gel strength (GS)), filtration (filtrate volume (FV), spurt loss (SL), cake thickness (CT) and permeability (k)) and the inhibition power (dispersibility test and the bentonite inhibition test) of the studied fluids. According to the obtained results it was concluded that the study fluids showed pseudoplastic behavior and addition of potassium citrate to the fluid did not cause changes in the pseudoplastic behavior of fluids. It was concluded that the combined use of additives starch, CMC LV and calcite reduces more effectively the filtration properties of drilling fluids studied and the filtration properties of the fluids inhibited with potassium citrate were optimized since the FV values obtained were lower than the considered base fluid. The formulations which showed efficient filtration and inhibition properties were prepared with high concentrations of potassium citrate. They have presented low values of FV and lower values of SL.

O sucesso da conclusão de um poço por perfuração e o custo do projeto estão relacionados às propriedades dos fluidos de perfuração. O estudo experimental foi realizado a partir da determinação e análise das curvas de tensão de cisalhamento versus taxa de deformação de suspensões aquosas de bentonita e carboximetilcelulose com diferentes concentrações de NaCl. Investigou-se, inicialmente, o comportamento reológico de suspensões de carboximetilcelulose 0,5% (em massa) com concentrações de sal, NaCl de 0 a 4% (em massa), para temperaturas variando de 14 a 26ºC. Os resultados experimentais possibilitam a caracterização reológica destas soluções como fluidos pseudoplásticos e indicam que a adição de NaCl em soluções com CMC alteram significativamente o comportamento reológico desse tipo de solução. Numa segunda etapa, estudou-se o comportamento reológico de suspensões de bentonita e carboximetilcelulose em diferentes concentrações de sal, NaCl. Empregaram-se soluções contendo 4,8 % de bentonita, 0,5 % de carboximetilcelulose e concentrações de 0 a 4% de NaCl. Constata-se o comportamento tixotrópico destas suspensões e a forte dependência com a concentração de sal. O estudo foi complementado com uma análise comparativa dos resultados do comportamento reológico obtidos por reômetro de cilindros coaxiais modelo Brookfield e o viscosímetro FANN 35 A, usualmente empregado na análise de fluidos de perfuração. O equacionamento do escoamento do fluido nos aparelhos permitiu uma interpretação mais detalhada dos valores descritos na norma, obtendo-se uma equivalência dos valores medidos em campo com os obtidos no reômetro Brookfield apesar de as faixas de operação de taxas de deformação serem distintas. / The properties of drilling fluids have a very significant effect on the successful of a well completion and the project costs. The experimental study was conducted based on the determination and analysis of the curves of shear stress and shear rate of aqueous suspensions composed of bentonite and carboxymetil cellulose at different concentrations of NaCl. The rheological behaviour of carboxymetil cellulose suspensions 0.5% w/w at NaCl concentrations in the range of 0 to 4% w/w from 14 to 26°C was studied. The experimental results allow the rheological characterization of these solutions as pseudoplastic fluid. It was observed that the addition of NaCl to CMC solutions changes its rheological behaviour significantly. In addition, the rheological behaviour of 4,8% bentonite suspensions with 0,5% carboxymethyl cellulose at different concentrations of NaCl in the range of 0 to 4% was studied. The characterization of these solutions showed thixotropic behaviour and a strong dependence on the salt concentration. The study was complemented with a comparative analysis of the results obtained by using a coaxial cylinders rheometer model Brookfield and the FANN Model 35 A viscometer, usually employed in drilling fluids analysis. The analytical solutions allowed a more detailed interpretation of the values described in the standard resulting in an equivalence between the measured values obtained in the field and in the Brookfield rheometer despite the differents shear rate ranges.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2016-09-28T13:47:04Z No. of bitstreams: 1 2011- Marcio Osvaldo Lima Magalhaes.pdf: 4632406 bytes, checksum: 8ccefc16f724417fcb426aaf9aac9f4a (MD5) / Made available in DSpace on 2016-09-28T13:47:04Z (GMT). No. of bitstreams: 1 2011- Marcio Osvaldo Lima Magalhaes.pdf: 4632406 bytes, checksum: 8ccefc16f724417fcb426aaf9aac9f4a (MD5) Previous issue date: 2011-12-19 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Despite the known problems caused by the by-products generated from the exploration of oil, this activity will be a part of our reality for the next 50 years. The oil drilling and exploration industry creates a substantial amount of waste that, if not adequately disposed of, could cause environmental problems. One of the main contaminates found in the waste related to oil drilling is the element barium. The purpose of this study was to evaluate the contamination of soil containing barium, its impact on the growth of rice plants (Orysa sativa) and potential risk of contaminating groundwater. This paper was divided into four chapters. The goal of the first chapter was to evaluate the spatial variability of barium levels found in former oil well drilling waste disposal sites. For this study, soil was collected from georeferenced points, analyzed in terms of its pseudo total levels, and prepared for the geochemical fractionation of barium, classifying the material in accordance with resolution 420 of CONAMA [Brazilian National Counsel on the Environment] (2009). In the second chapter, the effect of redox potential in soil on the mobility and absorption of barium by rice, having barium sulfate P.A. as the element?s source, was assessed. The effect was evaluated by performing rice culture pot and column leaching tests. The aim of the third chapter was the characterization and traceability of heavy metals in waste generated during the recovery of oil well drilling fluids. The waste was collected during the drilling of well 7-MGP-98D-BA, where the material was separated by composite sample, based on depth and equipment. In the fourth chapter, the effects of redox potential in soil interaction and heavy metals coming from the waste generated from onshore oil well drilling were analyzed. This chapter was similar to chapter two, with the main difference being the waste generated from well 7-MGP-98D-BA, which supplied the source of barium. The waste materials selected were those that displayed the lowest levels of arsenic, cadmium, barium, lead, and sodium. The obtained results showed that waste generated from oil well drilling contains high levels of barium, and that when disposed of in soil can significantly contribute to site contamination, having used the guiding values of CONAMA (2009) as a reference. As such, the barium present in this area was in the form of low solubility, as evidenced by the geochemical fractionation of the element. It was also observed that the conditions of low values of redox potential (-200 mV) promoted an increase of barium in fractions of greater mobility, causing major losses of the element by leaching, and increased absorption by plants. Among the studied waste materials, the waste from the dehydrator and the centrifuge 1 presented high levels of sodium as its greatest limitation, which affected the development of plants. / Apesar da verifica??o de problemas ocasionados pelo uso de produtos gerados a partir da explora??o do petr?leo, essa atividade ? uma realidade nos pr?ximos 50 anos. A industria de perfura??o e explora??o de petr?leo ? uma atividade que gera muitos residuos que, caso dispostos de forma inadequada, podem ocasionar problemas ambientais. Um dos principais contaminantes relacionados aos res?duos de perfura??o de po?os de petr?leo ? o elemento b?rio. A proposta desse estudo foi de avaliar a contamina??o dos solos com b?rio e seu impacto no desenvolvimento de plantas de arroz (Orysa sativa) e o risco de contamina??o do len?ol fre?tico. Para isso o trabalho foi dividido em quatro cap?tulos. O primeiro cap?tulo teve como objetivo avaliar a variabilidade espacial dos teores de b?rio em antiga ?rea de disposi??o de res?duo de perfura??o de po?os de petr?leo. Nesse estudo foram coletados solos em pontos georreferenciados e analisados quanto aos teores pseudototais e feito o fracionamento geoqu?mico do b?rio, classificando o material de acordo com a resolu??o 420 do Conama (2009). No segunto cap?tulo foi avaliado o efeito do potencial redox do solo na mobilidade e absor??o de b?rio por arroz, tendo como fonte do elelmento o sulfato de b?rio P.A. Esse efeito foi avaliado atrav?s de ensaios em vasos com cultivo de arroz e em colunas de lixivia??o. O terceiro cap?tulo teve como objetivo a caracteriza??o e rastreabilidade de metais pesados em res?duos gerados na recupera??o do fluido de perfura??o de po?os de petr?leo. O res?duo foi coletado durante a perfura??o do po?o 7-MGP-98D-BA, onde os materiais foram separados em amostras compostas em fun??o da profundidade e do equipamento. No quarto cap?tulo foi analisado o efeito do potencial redox na intera??o solo e metais pesados provenientes de res?duos oriundos da perfura??o de po?os de petr?leo ?onshore?. Esse cap?tulo foi semelhante ao cap?tulo 2, diferindo principalmente na fonte de b?rio que foi o res?duo gerado no po?o 7-MGP-98D-BA. Os res?duos selecionados foram os que apresentaram como os mais restrit?vos com rela??o aos teores de ars?nio, c?dmio, b?rio, chumbo e s?dio. Os resultados obtidos evidenciaram que os res?duos oriundos da perfura??o de po?os de petr?leo possuem altos teores de b?rio, que quando dispostos nos solos podem contribuir significativamente para a contamina??o das ?reas, tendo como refer?ncia os valores orientadores do Conama (2009). Entretanto, o b?rio presente nessa ?rea estava sob forma de baixa solubilidade, evidenciada pelo fracionamento geoqu?mico do elemento. Tamb?m foi observado que a condi??o de baixos valores de potencial redox (-200 mV) promoveu o aumento do b?rio nas fra??es de maior mobilidade, ocasionando maiores perdas do elemento por lixivia??o e maior absor??o pelas plantas. Dentre os res?duos estudados, os res?duos do secador e da centr?fuga 1 apresentaram como maior limita??o os altos teores de s?dio, o que afetou o desenvolvimento das plantas.

[pt] A maioria dos problemas de instabilidade ocorre quando rochas argilosas como folhelhos são perfuradas e o fluido de perfuração interage com a rocha. A interação rocha- fluido é materializada através da troca de íons e moléculas de água entre o fluido de perfuração e a rocha, gerando como conseqüências à variação nas poropressões dentro do folhelho e a alteração na estrutura dos minerais. O presente trabalho tem como objetivo o estudo das mudanças nas propriedades físico-químicas de amostras de folhelhos quando imersas em água e em sais orgânicos e inorgânicos. Um equipamento de imersão foi desenvolvido no qual amostras de folhelho são postas em contato com fluidos. Os resultados eletroquímicos indicam que a imersão dos folhelhos em soluções salinas reduz, quando comparada com a água, as alterações nas propriedades mecânicas, químicas e eletroquímicas dos fluidos. Os resultados mostram também que os folhelhos de origem offshore são mais reativos que os folhelhos originados de plataforma terrestres, devido às propriedades de seus constituintes individuais e de sua microestrutura. Quando imersos, os cloretos e os formiatos reduzem a hidratação das amostras, as mudanças no pH, as alterações nas atividades químicas dos folhelhos e dos fluidos dos poros, na capacidade de troca catiônica, na composição química da matriz da rocha e fluido dos poros, além de diminuir a desintegração superficial das amostras. A microscopia ótica, eletrônica e a espectrometria de dispersão de energia indicam a deposição dos sais nas superfícies das amostras. / [en] Most of borehole instability problems occur when argillaceous rocks such as shales are drilled and the drilling fluid interacts with the rock. The rock-fluid interaction is materialized through the exchange of ions and water molecules between the drilling fluid and the rock, generating pore pressure variation inside the shale and changes in minerals structure. The present work has the objective of studying the changes in the physicochemical properties of shale samples when immersed in the water, inorganic and organic salts. Immersion equipment was developed in which shale samples are put in contact with fluid. The results show that immersion of shale samples in salt solutions reduce, when compared with de-ionized water, the changes in mechanics, chemical and electrochemical of solutions. The results also show that the shales from offshore platform are more reactive than terrestrial basin, in function of shale s individual constituents and microstructure. When immersed, the chlorides and formates reduce the rock water content, the changes in the rock pH, water activity of shale and interstitial water, in the cation exchange capacity, in the chemical composition of rock and interstitial water e reduce the shale s loss of mass. The results indicate that the ions presents in the rock and the fluids flow in the direction of decreasing solute concentration gradient. This result in the alteration the exchangeable bases of shales and the specific surface of clays minerals. The electronic and optic microscopy and energy dispersion spectrometry indicated a deposition of salts in the surface of samples.

Made available in DSpace on 2015-04-01T12:17:42Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1676391 bytes, checksum: 8c1712b1a1b20bab712cd61fd62f5650 (MD5) Previous issue date: 2014-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The physical characteristics as particle size distribution, density, shape, specific surface area and surface roughness affects the rheological behavior of dispersions. The objective of this work is to study the influence of particle size variation of bentonite clay used as viscosifying agents in water based drilling fluids, the rheological and filtration properties. For both six bentonite clays from deposits in Boa Vista, PB, which were prepared for physical and mineralogical characterization were selected. Then, they were crushed and sieved into different sieve ABNT N° 80, 200 and 325 (180, 75 and 45 μm), being determined from the particle size distribution by laser diffraction their dispersions and then treatment performed with a solution of sodium carbonate (Na2CO3 ) determining the rheological and filtration properties of their aqueous dispersions. We also evaluated the influence of two different curing conditions on the transformations performed on the polycationic bentonite with sodium in their rheological properties. Clays had physical and mineralogical characteristics typical of bentonite clays. The variation of the openings of the sieves influenced, in general, only the accumulated mass below 2 μm who showed greater for sieve clays in the opening 45 μm and all size analysis showed monomodal distribution. It was observed that, in general, the decrease in average particle diameter and increase in cumulative weight below 2 μm, VA is decreased. It was not possible to generalize the influence given by the size of the particles in the VP and VF. The curing time longer possible to clays which had accumulated mass lower than 2 μm (clay) higher to obtain dispersions with thixotropic characteristics and higher and lower values of VA and VP. It was not possible to generalize the influence of curing time in VF. The fine particles of bentonite have great tendency to form agglomerates hindering the analysis of the actual particle size and its relation to the rheological properties. / As características físicas das partículas como distribuição granulométrica, densidade, formato, área superficial específica e rugosidade superficial afetam o comportamento reológico de dispersões. O objetivo deste trabalho é estudar a influência da variação granulométrica de argilas bentoníticas utilizadas como agentes viscosificantes em fluidos de perfuração base água, nas propriedades reológicas e de filtração. Para tanto, foram selecionadas seis argilas bentoníticas provenientes de jazidas do município de Boa Vista, PB, que foram preparadas para caracterização física e mineralógica. Em seguida foram moídas e peneiradas em diferentes peneiras ABNT n° 80, 200 e 325 (180, 75 e 45 μm), sendo determinadas as distribuições granulométricas de suas dispersões por difração laser e posteriormente realizado o tratamento com solução de carbonato de sódio (Na2CO3) determinando-se as propriedades reológicas e de filtração de suas dispersões aquosas. Também foi verificada a influência de duas diferentes condições de cura realizadas nas transformações das bentonitas policatiônicas em sódicas em suas propriedades reológicas. As argilas apresentaram características físicas e mineralógicas típicas de argilas bentoníticas. A variação das aberturas das peneiras influenciou, em geral, apenas na massa acumulada abaixo de 2 μm que se apresentou maior para as argilas peneiradas na abertura de 45 μm e todas as análises granulométricas apresentaram distribuição monomodal. Observou-se que, em geral, com a diminuição no diâmetro médio das partículas e aumento na massa acumulada abaixo de 2 μm, ocorre diminuição na VA. Não foi possível generalizar a influência apresentada pelo tamanho de partículas na VP e no VF. O tempo de cura maior possibilita, para as argilas que apresentaram massas acumuladas abaixo de 2 μm (fração argila) mais elevadas, a obtenção de dispersões com características tixotrópicas e com maiores VA e menores valores de VP. Não foi possível generalizar a influência do tempo de cura no VF. As partículas finas de bentonitas apresentam grande tendência em formar aglomerados dificultando a análise do real tamanho de partículas e sua relação com as propriedades reológicas.