Qualidade fisiológica de sementes de genótipos de algodoeiro sob estresse salino

The germination of cotton seeds and the seedlings emergency are generally delayed and reduced by the salinity. Although the cotton is considered a tolerant culture, it can suffer substantial reductions in regarding its growth and production when exposed to salinity condition. The aims of this study went evaluate the effect of the saline stress in the germination phase to four cotton genotypes (BRS Rubi, BRS Safira, BRS 201 and CNPA 187 8H), using different osmotic potentials generated with increment of sodium chloride (NaCl). The saline stress was simulated using NaCl aqueous solutions in the potentials: 0.0 (Control); -0.2; -0.4; -0.6; -0.8 and -1.0 MPa. The treatments were monitored by means of tests for analysis of seeds, germination, first counting, speed germination index, length of shoot, radicle length, dry weigth of embrionic axis and shoot/radicle ratio. The tests for germination, first counting and index of germination speed were accomplished using 50 seeds for repetition and for the study of length of shoot, radicle length, dry weigth of embrionic axis and shoot/radicle ratio were used 20 seeds by repetition. For both tests four repetitions were accomplished by genotype for each one of the potentials. The seeds of each repetition were involved in papers Germitest humidified with NaCl solution corresponding to the potential. The repetitions of both tests were maintained in a germinator with saturated humidity. The analysis were initiate four days after the induction of the saline stress. The evaluations of the first three variables analyzed were accomplished daily; the seeds were remove and counted when its germinated. For the length tests just the repetitions corresponding to the potential of NaCl 0,0 MPa were analysis 4 days after the beginning of the induction of the saline stress. The analysis of the repetitions of the potentials -0,2 and -0,4 and of the potentials -0,6, -0,8 and -1,0 MPa they were accomplished with 12 and 20 days, respectively. For accomplishment of the analisis of this test the shoot of the 20 plantules of each repetition was separate from the radicle and both parts were measured. The statistical analyses were performed using the GENMOD and GLM procedures of the SAS. For the variable germination, the cultivates CNPA 187 8H and BRS Safira stood out for the potential -0.8 MPa, with averages of 89% and 81%, respectively. The test of speed germination index to cultivate BRS Safira presented the largest averages for the two higher saline potentials. It was observed that the increase of the saline potential reduces the germination percentage and speed germination index. For each day of evaluation it was verified that the increase of the saline potential causes a reduction of the length both of the shoot and of the radicle. The radicle tends to grow more than the shoot until the potential -0,4 MPa

Interações entre a carboximetilcelulose, carbonato de cálcio e bentonita: repercussões sobre as propriedades dos fluidos de perfuração aquosos

The role of carboxymethylcellulose (CMC) in association to calcium carbonate particles (CaCO3) in most water-based drilling fluids is to reduce the fluid loss to the surrounding formation. Another essential function is to provide rheological properties capable of maintaining in suspension the cuttings during drilling operation. Therefore, it is absolutely essential to correlate the polymer chemical structure (degree of substitution, molecular weight and distribution of substituent) with the physical-chemical properties of CaCO3, in order to obtain the better result at lower cost. Another important aspect refers to the clay hydration inhibitive properties of carboxymethylcellulose (CMC) in drilling fluids systems. The clay swelling promotes an undesirable damage that reduces the formation permeability and causes serious problems during the drilling operation. In this context, this thesis consists of two main parts. The first part refers to understanding of interactions CMC-CaCO3, as well as the corresponding effects on the fluid properties. The second part is related to understanding of mechanisms by which CMC adsorption occurs onto the clay surface, where, certainly, polymer chemical structure, ionic strength, molecular weight and its solvency in the medium are responsible to affect intrinsically the clay layers stabilization. Three samples of carboximetilcellulose with different molecular weight and degree of substitution (CMC A (9 x 104 gmol DS 0.7), CMC B (2.5 x 105 gmol DS 0.7) e CMC C (2.5 x 105 gmol DS 1.2)) and three samples of calcite with different average particle diameter and particle size distribution were used. The increase of CMC degree of substitution contributed to increase of polymer charge density and therefore, reduced its stability in brine, promoting the aggregation with the increase of filtrate volume. On the other hand, the increase of molecular weight promoted an increase of rheological properties with reduction of filtrate volume. Both effects are directly associated to hydrodynamic volume of polymer molecule in the medium. The granulometry of CaCO3 particles influenced not only the rheological properties, due to adsorption of polymers, but also the filtration properties. It was observed that the lower filtrate volume was obtained by using a CaCO3 sample of a low average size particle with wide dispersion in size. With regards to inhibition of clay swelling, the CMC performance was compared to other products often used (sodium chloride (NaCl), potassium chloride (KCl) and quaternary amine-based commercial inhibitor). The low molecular weight CMC (9 x 104 g/mol) showed slightly lower swelling degree compared to the high molecular weight (2.5 x 105 g/mol) along to 180 minutes. In parallel, it can be visualized by Scanning Electron Microscopy (SEM) that the high molecular weight CMC (2.5 x 105 g/mol e DS 0.7) promoted a reduction in pores formation and size of clay compared to low molecular weight CMC (9.0 x 104 g/mol e DS 0.7), after 1000 minutes in aqueous medium. This behavior was attributed to dynamic of interactions between clay and the hydrodynamic volume of CMC along the time, which is result of strong contribution of electrostatic interactions and hydrogen bounds between carboxylate groups and hydroxyls located along the polymer backbone and ionic and polar groups of clay surface. CMC adsorbs on clay surface promoting the skin formation , which is responsible to minimize the migration of water to porous medium. With the increase of degree of substitution, it was observed an increase of pores onto clay, suggesting that the higher charge density on polymer is responsible to decrease its flexibility and adsorption onto clay surface. The joint evaluation of these results indicate that high molecular weight is responsible to better results on control of rheological, filtration and clay swelling properties, however, the contrary effect is observed with the increase of degree of substitution. On its turn, the calcite presents better results of rheological and filtration properties with the decrease of average viii particle diameter and increase of particle size distribution. According to all properties evaluated, it has been obvious the interaction of CMC with the minerals (CaCO3 and clay) in the aqueous medium

Estudo sobre tratamento térmico e mudança superficial da diatomita de Punaú/RN para o desenvolvimento de um auxiliar de filtração

The diatomite is a natural material that has numerous applications due to changes in their physical and chemical properties after processing. It is currently used in the industry as a sound insulator , filter aid and industrial load . The filter material shall be inert chemical composition , which will diatomite confers a high commercial value and performance not found in other particulate materials , for this application. The diatomite surface undergoes changes after thermal treatment at high temperatures , from 800ºC , with properties that enable its application in the food , beverage , pharmaceutical , cosmetic and textiles . In this work , we developed a study on thermal treatment on natural diatomite to adapt their properties to the application as a filter aid . The heat treatments were performed in an open oven at temperatures of 800ºC , 1000ºC and 1200ºC for a time of 24 hours. Reagents were added in the constitution of the samples analyzed. The reagents used were sodium carbonate (Na2CO3 ) and sodium chloride (NaCl) . The samples were characterized by x - ray diffraction , x -ray fluorescence , scanning electron microscopy , analysis and particle size distribution , specific surface area by the BET method , and pore volume by BJH method. The results showed a reduction in porosity of the material as well as a significant increase in specific surface area after heat treatment and the reactants in the ratio of 3 wt%. The diatomaceous earth , after heat treatment , undergone changes in its coloration , varying in white, cream and beige , which directly interferes with the speed of filtration materials process. All results obtained before and after heat treatment of the material with the values obtained for samples already used industrially , Brazilian and American industry , which were characterized using the same test methods performed with the samples in the study were compared and showed promising efficiency when material studied in the region of Punaú - RN , after processing , reagent addition and heat treatment, as an element in the composition of filter .

Fluidos de perfuração aquosos: a contribuição da goma xantana e carboximetilcelulose no controle de filtrado

This study aimed mainly to evaluate the influence of xanthan gum (XG) and carboxymethylcellulose (CMC) in the filtration process of water-based drilling fluids, considering the conformational changes suffered by the polyelectrolyte with the addition of sodium chloride (NaCl) in different concentrations (0.17, 0.34 and 0.51 mol.L-1). It was also evaluated the behavior of the fluid by the addition of calcium carbonate (CaCO3) in pure water and in brine. Seeking a better understanding of the interaction between the polymers used and CaCO3, polymer adsorption analyzes were performed using a depletion method, which yielded a higher percentage of adsorption of Xanthan Gum in this material (29%), which can justify the formation of a thin and waterproof filter cake for drilling fluids containing this polymer. However, the best values of apparent viscosity (20 and 24 mPa.s) and volume of filtrate (8.0 and 8.1 mL) were obtained for the systems consisting of xanthan gum, CMC and CaCO3, in NaCl aqueous solutions concentrations of 0.34 and 0.51 mol.L-1, respectively. The values can be related to the presence of CMC that increases the apparent viscosity and reduces the volume of filtrate. In addition, the CaCO3 added acts as a bridging agent, promoting the formation of a less permeable filter cake

Contribuição da poliacrilamida parcialmente hidrolisada em associação com a bentonita em fluidos de perfuração aquosos

In this study, we investigated the effect of addition of partially hydrolyzed polyacrylamide (HPAM) and bentonite in the physicochemical properties of acquous drilling fluids. Two formulations were evaluated: F1 formulation, which was used as reference, containing carboxymethylcellulose (CMC), magnesium oxide (MgO), calcite (calcium carbonate - CaCO3 ), xanthan gum, sodium chloride (NaCl) and triazine (bactericidal); and F2, containig HPAM steady of CMC and bentonite in substituition of calcite. The prepared fluids were characterized by rheological properties, lubricity and fluid loss. Calcite was characterized by granulometry and thermal gravimetric analysis (TGA). The formulation F2 presented filtration control at 93◦C 34 mL while F1 had total filtration. The lubricity coefficient was 0.1623 for F2 and 0.2542 for F1, causing reduction in torque of 25% for F1 and 52 % for F2, compared to water. In the temperature of 49 ◦C and shear rate of 1022 s −1 , the apparent viscosities were 25, 5 and 48 cP for F1 and F2 formulation, respectively, showing greater thermal resistance to F2. With the confirmation of higher thermal stability of F2, factorial design was conducted in order to determine the HPAM and of bentonite concentrations that resulted in the better performance of the fluids. The statistical design response surfaces indicated the best concentrations of HPAM (4.3g/L) and bentonite (28.5 g/L) to achieve improved properties of the fluids (apparent viscosity, plastic viscosity, yield point and fluid loss) with 95% confidence, as well as the correlations between these factors (HPAM and bentonite concentrations). The thermal aging tests indicated that the formulations containing HPAM and bentonite may be used to the maximum temperature until 150 ◦C. The analyze of the filter cake formed after filtration of fluids by X-ray diffraction showed specific interactions between the bentonite and HPAM, explaining the greater thermal stability of F2 compared to the fluid F1, that supports maximum temperature of 93 ◦C.

Avaliação da influência do nacl em pastas de cimento portland para cimentação de poços de petróleo em zonas evaporíticas

One of the major current challenges for oilwell companies is the extraction of oil from evaporitic zones, also known as pre-salt basins. Deep reservoirs are found under thick salt layers formed from the evaporation of sea water. Salt layers seal the flow of oil from underneath rock formations, which store hydrocarbons and increase the probability of success in oil and gas exploration. Oilwells are cemented using Portland-based slurries to promote mechanical stability and zonal isolation. For pre-salt oilwells, NaCl must be added to saturate the cement slurries, however, the presence of salt in the composition of slurries affects their overall behavior. Therefore, the objective of the present study was to evaluate the effect of the addition of 5 to 25% NaCl on selected properties of Portland-based slurries. A series of tests were carried out to assess the rheological behavior, thickening time, free water and ultrassonic compressive strength. In addition, the slurries were also characterized by thermal analysis, X ray diffraction and scanning electron microscopy. The results showed that the addition of NaCl affected the thickening time of the slurries. NaCl contents up to 10% shortened the thickening time of the slurries. On the other hand, concentrations in excess of 20% not only extended the thickening time, but also reduced the strength of hardened slurries. The addition of NaCl resulted in the formation of a different crystalline phase called Friedel´s salt, where free chlorine is bonded to tricalcium aluminate

Influência da adição do NaCl e KCl em sistemas de pastas contendo sílica para poços de petróleo em zonas evaporíticas e carbonáticas

One of the major challenges faced nowadays by oil companies is the exploration of pre-salt basins. Thick salt layers were formed in remote ages as a consequence of the evaporation of sea water containing high concentrations of NaCl and KCl. Deep reservoirs can be found below salt formations that prevent the outflow of oil, thus improving the success in oil prospection. The slurries used in the cement operations of salt layers must be adequate to the properties of those specific formations. At the same time, their resulting properties are highly affected by the contamination of salt in the fresh state. It is t herefore important to address the effects of the presence of salt in the cement slurries in order to assure that the well sheath is able to fulfill its main role to provide zonal isolation and mechanical stability. In this scenario, the objective of the present thesis work was to evaluate the effect of the presence of NaCl and KCl premixed with cement and 40% silica flour on the behavior of cement slurries. Their effect in the presence of CO2 was also investigated. The rheological behavior of slurries containing NaCl and KCl was evaluated along with their mechanical strength. Thermal and microstructural tests were also carried out. The results revealed that the presence of NaCl and KCl affected the pozzolanic activity of silica flour, reducing the strength of the hardened slurries containing salt. Friedel´s salt was formed as a result of the bonding between free Cl- and tricalcium aluminate. The presence of CO2 also contributed to the degradation of the slurries as a result of a process of carbonation/bicarbonataion

Efeito de um extrato de Ganoderma lucidum (Reishi) na marcação de constituintes sanguíneos com tecnécio-99M e na sobrevivência de Escherichia coli

Clinical evaluations have been made possible with radiobiocomplexes marked with tecnecium-99m (99mTc). Natural or synthetic drugs are able to interfere in the marking of blood structures with 99m Tc. Also, the toxicity of several natural products has been described. The aim of this study was evaluating the effect of an extract of Ganoderma lucidum (Reishi) in the marking of blood constituents with 98m Tc and in the survival of Escherichia coli. Blood samples from Wistar rats were treated with reishi extract. Radiomarking procedure was performed. Samples of plasma (P), blood cells (CS), and insoluble (FI) and soluble (FS) fractions of P and CS were separated and the radioactivity was counted to determine radioactivity percentages (%ATI). Escherichia coli AB1157 cultures were treated with stannous chloride in the presence and absence of the reishi extract. Blood samples and bacterial cultures treated with NaCl 0.9% were used as controls. Data indicated that the reishi extract has significantly altered (p<0,05) the %ATI of P, CS, FI-P, FS-P, FI-CS e FS-CS, as well as it has increased survival of bacterial cultures treated with stannous chloride. Our results suggest that the Reishi extract would be able to present a redox/ chelant action by altering blood constituent marking with 99mTc and by protecting bacterial cultures against stannous chloride-induced oxydating lesions. The study had a multidisciplinary character, with the participation of the following areas of knowledge: Biophysics, Radiobiology, Botanics, Phytotherapy, and Hematology

Desgaste corrosivo-cavitativo-erosivo de um aço-carbono em meio aquoso com frações de sal (NaCl), CO2 e particulados sólidos (SiO2)

A batch of eighty-four coupons of low carbon steel were investigated at laboratory conditions under a corrosive, cavitative-corrosive (CO2) and corrosive-erosive (SiO2 + CO2) in an aqueous salt solution and two levels of temperature. The following measurements were made on Vickers (HV0,05, HV0,10, HV0,20) Microhardness tests at three levels of subsurface layer. A turbulent flow collided on the cylindrical sample, with and without mechanical stirring and gas bubbling, with and without fluid contamination by solid particles of SiO2, at two temperatures. Surface Roughness and Waviness, under two conditions "as received, after machining" and "after worn out", as well as gravimetric and electrochemical parameter were measured on the two opposite generatrices of each cylindrical sample, on the flow upstream (0°) and downstream (180°) by Profilometry, Mass Variation and Linear Polarization Resistance (LPR). The results of the Microhardness and Surface Texture of all coupons were subjected to statistical comparison, using the software Statgraphics® Centurion XVI, 95% statistical certainty, and significant differences were observed in some arrays of measurements. The corrosive wear rate measured by LPR and mass variation shown to be sensitive to the presence of bubbles and hydrodynamic fluctuations inside the cell, considering the temperature and contamination of corrosive fluid by solid particles. The main results of visual inspection relative to some topologies of the surface damages involving different mechanisms that were seen to give explanation for some fluctuations in wear rates of the steel experimentally investigated

efeito da aplicação de uma solução salina no crescimento e na composição química da atriplex nummularia

This study aimed to analyze the effect of a saline solution on growth and chemical composition of Atriplex nummularia, shrubby plant, absorbing salts used in the diet of animals and the management of water and saline soils. These plant seedlings were planted and grown in a reserved area at the Federal University of Rio Grande do Norte. The plantation was divided into two blocks, in which one of them was irrigated with saline solution with a concentration of 2840 mgL-1 of NaCl and the second group was irrigated with drinking water. After six months, the plants were collected, harvested and divided into three parts: leaf, thin and thick stem. Monthly, dimension measurements were carried out for cataloging the growth of Atriplex. Ion Chromatography (IC) and Optical Emission Spectroscopy Inductively Coupled Plasma (ICP-OES) were used to analyze the chemical composition of the partition plant parts. The results of these analyses revealed that an absorption process of anions and cations by Atriplex nummularia plant during its growth was achieved, in particular by a higher concentration of sodium and chloride ions. Scanning electron microscopy images showed and confirmed the presence of small crystals on the leaf surface. Electrical conductivity and pH measurements of the aerial parts of the plant were carried out and these results showed that the leaf is the plant part where there is a largest concentration of ions. In addition, measurements of specific surface were obtained from irrigated plants with saline solution, achieving higher surface area, in all cases. Plant dimensions obtained monthly showed that the plants irrigated with water grew 5% more than those plants irrigated with saline solution. Based on results obtained, Atriplex plant showed a higher potential to survive and adapt to environments (aquatic or geological) with high levels of salinity and this property can be used as a tool for removing salts/metals from industrial contaminated soils and effluents.

Caracterização físico-química de sistemas micelares

The process of adsorption and micellization of the surfactants sodium dodecyl sulfate, dodecylammonium chloride and hexaethylene glycol mono-n-dodecyl ether in water-air interface has been studied using measurements of surface tension in aqueous media and NaCl 0.1 mol/L in temperatures of 25, 33 and 40 °C. From these data, critical micelle concentrations and thermodynamic parameters of micellization and adsorption were determined in order to elucidate the behaviors of micellization and adsorption for these surfactants in the proposed medium. For the determination of the thermodynamic parameters of adsorption we utilized the equations of isotherms of Langmuir and Gibbs. Γmáx values determined by the different equations were correlated to the explanation of results. Temperature and salinity were analyzed in terms of their influence on the micellization and adsorption process, and the results were explained based on intermolecular interactions. The values of Gmic have confirmed that the micelle formation for the surfactants studied occurs spontaneously

Aplicação de tecnologias eletroquímicas (oxidação via radicais hidroxila, oxidação mediada via cloro ativo e eletrocoagulação) para o tratamento de efluentes reais ou sintéticos

In this work the degradation of real and synthetic wastewater was studied using electrochemical processes such as oxidation via hydroxyl radicals, mediated oxidation via active chlorine and electrocoagulation. The real effluent used was collected in the decanter tank of the Federal University of Rio Grande do Norte (ETE-UFRN) of Effluent Treatment Plant and the other a textile effluent dye Ácido Blue 113 (AB 113) was synthesized in the laboratory. In the electrochemical process, the effects of anode material, current density, the presence and concentration of chloride as well as the active chlorine species on site generated were evaluated. Electrodes of different compositions, Ti/Pt, Ti/Ru0,3Ti0,7O2, BDD, Pb/PbO2 and Ti/TiO2-nanotubes/PbO2 were used as anodes. These electrodes were subjected to electroanalytical analysis with the goal of checking how happen the anodic and cathodic processes across the concentrations of NaCl and supporting electrolyte used. The potential of oxygen evolution reaction were also checked. The effect of active chlorine species formed under the process efficiency was evaluated by removing the organic matter in the effluent-ETE UFRN. The wastewater treatment ETE-UFRN using Ti/Pt, DDB and Ti/Ru0,3Ti0,7O2 electrodes was evaluated, obtaining good performances. The electrochemical degradation of effluent-UFRN was able to promote the reduction of the concentration of TOC and COD in all tested anodes. However, Ti/Ru0,3Ti0,7O2 showed a considerable degradation due to active chlorine species generated on site. The results obtained from the electrochemical process in the presence of chloride were more satisfactory than those obtained in the absence. The addition of 0.021 M NaCl resulted in a faster removal of organic matter. Secondly, was prepared and characterized the electrode Ti/TiO2-nanotubes/PbO2 according to what the literature reports, however their preparation was to disk (10 cm diameter) with surface area and higher than that described by the same authors, aiming at application to textile effluent AB 113 dye. SEM images were taken to observe the growth of TiO2 nanotubes and confirm the electrodeposition of PbO2. Atomic Force Microscope was also used to confirm the formation of these nanotubes. Furthermore, was tested and found a high electrochemical stability of the electrode Ti/TiO2-nanotubes/PbO2 for applications such as long-term indicating a good electrocatalytic material. The electrochemical oxidation of AB 113 using Ti/Pt, Pb/PbO2 and Ti/TiO2-nanotubes/PbO2 and Al/Al (electrocoagulation) was also studied. However, the best color removal and COD decay were obtained when Ti/TiO2-nanotubes/PbO2 was used as the anode, removing up to 98% of color and 92,5% of COD decay. Analysis of GC/MS were performed in order to identify possible intermediates formed in the degradation of AB 113.

Caracterização físico-química e química do fruto do juazeiro (Ziziphus joazeiro Mart) e avaliação da sua conservação por fermentação láctica

Considering the plant biodiversity in the Brazilian Northeast, whose components can be inserted into sustainable production systems, the jujube (Ziziphus joazeiro Mart.) emerges as to recovery of its fruit. The present study has as objective to characterize the fruit of the jujube under the physical, physicochemical and chemical approach and assess its conservation by spontaneous lactic fermentation under the influence of chloride, sodium, calcium and potassium. According to the legislation, vegetable acidified by fermentation that is subjected to lactic acid fermentation in order to achieve a final product pH less than or equal to 4.5. The results of the physical, chemical and physico-chemistry of ripe fruit jujube showed the potential of this species for agro-processing. The yield of edible portion (91.83%), soluble solids content (18,98º Brix), titratable acidity (0.14% citric acid), pH (5.30) and its composition, divided in moisture (79.01%), protein (2.01%), lipids (0.52%), carbohydrate (17.59%), fiber, ash (0.76%) and its minerals were consistent with the characteristic profile fruits, thus favoring the development of spontaneous lactic fermentation. The minimum pH and titratable acidity observed maximum in the fermentation process under the influence of mixtures of salts (NaCl and KCl NaCl2) values ranged from 3.4 to 3.7 and from 0.54 to 0.95 (% lactic acid), respectively. The profile of the lactic fermentation of fruit of jujube in brine, fermented microbiological quality and the result of analysis of primary sensory prepared preserved, the application of endorsed by the consumer sensory evaluation, more particularly, derived from fermented fruit preserved in the presence of chloride sodium, in accordance with the traditional techniques of lactic fermentation of vegetables. The results of sensory evaluation conducted with 100 consumers (tasters) revealed an acceptance rate equal to 78% of the preserve. Despite restrictions on the sensory acceptability of fermented under the influence of salts (KCl and CaCl2) substitutes sodium chloride, preserved these perspectives presented to balance the optimization of mixtures, health product safety and consumer awareness towards prefer a more healthy product with reduced sodium content.

Avaliação da influência do nacl em pastas de cimento portland para cimentação de poços de petróleo em zonas evaporíticas

One of the major current challenges for oilwell companies is the extraction of oil from evaporitic zones, also known as pre-salt basins. Deep reservoirs are found under thick salt layers formed from the evaporation of sea water. Salt layers seal the flow of oil from underneath rock formations, which store hydrocarbons and increase the probability of success in oil and gas exploration. Oilwells are cemented using Portland-based slurries to promote mechanical stability and zonal isolation. For pre-salt oilwells, NaCl must be added to saturate the cement slurries, however, the presence of salt in the composition of slurries affects their overall behavior. Therefore, the objective of the present study was to evaluate the effect of the addition of 5 to 25% NaCl on selected properties of Portland-based slurries. A series of tests were carried out to assess the rheological behavior, thickening time, free water and ultrassonic compressive strength. In addition, the slurries were also characterized by thermal analysis, X ray diffraction and scanning electron microscopy. The results showed that the addition of NaCl affected the thickening time of the slurries. NaCl contents up to 10% shortened the thickening time of the slurries. On the other hand, concentrations in excess of 20% not only extended the thickening time, but also reduced the strength of hardened slurries. The addition of NaCl resulted in the formation of a different crystalline phase called Friedel´s salt, where free chlorine is bonded to tricalcium aluminate

Influência da adição do NaCl e KCl em sistemas de pastas contendo sílica para poços de petróleo em zonas evaporíticas e carbonáticas

One of the major challenges faced nowadays by oil companies is the exploration of pre-salt basins. Thick salt layers were formed in remote ages as a consequence of the evaporation of sea water containing high concentrations of NaCl and KCl. Deep reservoirs can be found below salt formations that prevent the outflow of oil, thus improving the success in oil prospection. The slurries used in the cement operations of salt layers must be adequate to the properties of those specific formations. At the same time, their resulting properties are highly affected by the contamination of salt in the fresh state. It is t herefore important to address the effects of the presence of salt in the cement slurries in order to assure that the well sheath is able to fulfill its main role to provide zonal isolation and mechanical stability. In this scenario, the objective of the present thesis work was to evaluate the effect of the presence of NaCl and KCl premixed with cement and 40% silica flour on the behavior of cement slurries. Their effect in the presence of CO2 was also investigated. The rheological behavior of slurries containing NaCl and KCl was evaluated along with their mechanical strength. Thermal and microstructural tests were also carried out. The results revealed that the presence of NaCl and KCl affected the pozzolanic activity of silica flour, reducing the strength of the hardened slurries containing salt. Friedel´s salt was formed as a result of the bonding between free Cl- and tricalcium aluminate. The presence of CO2 also contributed to the degradation of the slurries as a result of a process of carbonation/bicarbonataion