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The success of oil and gas exploration in carbonate reservoirs demands better strategies. Concerning the step of acid stimulation, the understanding of the nature of the carbonate matrices and their response to the acids can contribute for improvements of this process. We report a study about the reactivity of six different carbonate rocks with aqueous solutions of hydrochloric (HCl) and acetic (HAc) acids. The reactivity of the samples was determined by measuring the mass loss of the carbonate samples during the acid dissolution process. The results demonstrate that the dolomitization of the matrices is the main factor to decrease the kinetic of dissolution. Based on visual inspection, and micro-computed tomography, it was observed that the cylindrical outcrops with low dolomitization present different patterns of morphological dissolution upon HCl or HAc. For HCl, homogenous radial dissolution is observed, producing a smooth surface, while for HAc, the radial structure is practically preserved, but the surface become very rough. Concerning the inner effect of the acids, variations on the pore distributions of the outcrops were investigated by micro-computed tomography and pore distribution were observed during the dissolution cycles with the acids. This is an indication that the reaction occurs homogeneously from the surface, with negligible dissolution of the internal pore walls, since no pressure and flow procedures were employed in this study.

The variations in enthalpy (ΔfHWLM) and critical concentrations associated with the formation of wormlike micelles (WLMs) from combinations of tetradecyltrimethylammonium bromide (C14TAB) and various aromatic co-solutes were determined using isothermal titration calorimetry (ITC). Three groups of aromatic molecules were investigated: neutral (phenol), benzoate derivatives and cinnamate derivatives. In addition, the thermal stabilities of the WLMs (of hexadecyltrimethylammonium bromide, C16TAB) and the aromatic co-solutes of the three groups were investigated by measuring the temperatures at which the WLMs break and lose their ability to produce hydrodynamic drag reduction. A comparison of the results was used to establish correlations between the spontaneity of WLMs formation, their thermal stability and the molecular structure of the aromatic co-solutes. A characteristic thermal pattern with four steps was observed when WLMs are formed, that depended on the co-solute structure. Micellar growth was found to be an exothermic process, related to the fusion of the end caps allied with the incorporation of more co-solutes. The co-solutes that had negative charge and were able to maintain planar configuration demonstrated stronger interactions and also showed higher thermal stability through drag reduction.

The combination of cationic surfactants with some aromatic anions can result in the formation of long aggregates, named as wormlike micelles. Like polymers, they can be used as viscosity controllers. The stabilization of the aromatic anions inserted into the micelles and their position at the surface is central to change the curvature of the aggregates and its consequent growth. Therefore, the affinity between these two components defines the potential to wormlike micelle formation and the understand of the molecular aspects that driven the process is central. In this sense, in this work it was investigated the effect of the presence of F, Cl Br or I at the position 4 of the aromatic ring of halogenbenzoates on the incorporation of the anions into the micelles of C14TAB. By using the isothermal titration calorimetry, the spontaneity of the process was determined by measuring the magnitude of the energy released and the critical concentration for wormlike micelle formation. Wormlike micelles are only formed for Cl, Br and I, and the formation is more pronounced for halogen atom more voluminous. It can be expected that the fitting into the water structure of the anion with a more voluminous halogen is more difficult. Therefore, the hydrophobic effect is an important driven force to the partitioning of the aromatic anion from water to the micellar pseudo-phase. The processes of formation, growth and shortening of the wormlike micelle chains were determined by measuring the hydrodynamic radius of the aggregates and correlated with the enthalpimetric curves. In high concentration regime, the micelles are entangled and the characteristics of the supramolecular gel-like formed were investigated by using linear and non-linear rheology.

Under turbulent flow, wormlike micelles efficiently cause hydrodynamic drag reduction. However, it was demonstrated that beyond specific temperatures, the capacity of the micellar aggregates to produce drag reduction is abruptly lost. This can be associated with the decrease in size of long micellar chains, becoming shorter aggregates, in the sense that small aggregates are not capable to cause hydrodynamic drag reduction anymore. In this paper, we investigate the thermal effect on wormlike micelles under turbulent and quiescent regimes, in order to explore correlations between the size of the wormlike micelles and the hydrodynamic drag reduction phenomenon.

Agradecimentos: The authors acknowledge the Brazilian agencies CNPq (grant number: 301016/2015-1), FAPESP (grant numbers: 2015/ 25406-5 and 2015/08541-6), and PETROBRAS (grant number: 2015/00103-0). We also want to thank the lab technician of the Colloids and Interfaces Group of UNICAMP, Victor Augusto Licio Garcia Vilela, for helping to perform experiments (grant number: 301016/2015-1) and Marcelo Alexandre de Farias from the Brazilian Nanotechnology National Laboratory (LNNano) for the help in the CryoTEM analysis and also LNNano to the access to the CryoTEM facilities (research proposal: TEM-24274) Abstract: The energy released when tetradecyltrimethylammonium bromide (C14TAB) is combined with different derivatives of chlorobenzoates in an isothermal titration calorimeter (ITC) allows a direct evaluation of the spontaneity of the threading of the aromatic anions into the micellar palisade. The comparison between the enthalpimetric curves with the ones for viscosity of the solutions, hydrodynamic radii of the aggregates (dynamic light scattering experiments), and the fraction of aromatic anions incorporated (diffusion-ordered spectroscopy experiments) allows the establishment of the variations of enthalpy with formation, growth, and decrease of the wormlike micelles (WLMs). The formation of WLMs with C14TAB is very favored (very exothermic) for titrations of chlorobenzoate derivatives which present the chlorine atom in positions 3 or 4 of the aromatic ring. However, the aggregation is highly unfavorable if chlorine is at position 2 of chlorobenzoate. According to the results, the high potential of the ITC to determine critical concentrations and the energies associated with the aggregation of a cationic surfactant and aromatic anions for the formation of WLMs was demonstrated FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Fechado

Agradecimentos: The authors thank the Brazilian agencies CNPq (Grant Numbers: 140391/2016-9, 01016/2015-1, 301016/2015-1 and 140369/2015-5), FAPESP (Grant Numbers: 2013/16245-2, 2015/25406-5), FAEPEX, INEO and PETROBRAS (Grant Number: 2015/00103-0). This research was supported in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001. We also want to thank the lab technician of the Colloids and Interfaces Group of UNICAMP, Victor Augusto Licio Garcia Vilela, for helping to perform experiments Abstract: When tetradecyltrimethylammonium bromide, TTAB, is added to aqueous solution of sodium salicylate, NaSal, the threading of the aromatic anion into the micellar palisade leads to the formation of wormlike micelles. Based on the calorimetric titration of NaSal with TTAB, and on the lifetime of fluorescence of salicylate, we propose that the aggregation of the two components directly leads to the formation of wormlike micelles, without any pre-aggregation. By using an isothermal titration calorimeter, aliquots of TTAB were added to a dilute solution of NaSal. The energy involved in each addition was then integrated and the variation of enthalpy was determined. In the same range of concentrations and molar ratios, the surface tensiometry and time-resolved emission spectroscopy experiments were performed. A very characteristic calorimetric signal associated with wormlike micelle formation was obtained, being the enthalpy variation of this process, deltaWLMH0_298 < 0. When 1.2 mmol L-1 of NaSal is titrated with 11.0 mmol L-1 of TTAB at 298.15 K, delta fH0_298 = -10.31 kJ per mol of injectant. By adding TTAB to NaSal solution, two fluorescence lifetimes of salicylate were observed solely after wormlike micelle being formed. The correspondent lifetime values of 4.0 ns and 7.2 ns are respectively associated with the free and associated species of salicylate. The new results demonstrated that wormlike micelles are the first aggregate formed when TTAB is added to salicylate. This aspect is relevant for understanding the mechanism of wormlike micelles formation FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Fechado

Orientador: Edvaldo Sabadini Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química Resumo: Neste trabalho avaliou-se a capacidade de redução de atrito hidrodinâmico de soluções contendo micelas gigantes formadas por brometo de tetradeciltrimetilamônio e salicilato de sódio ou com 3,4-diclorobenzoato de sódio. O estudo foi realizado em um reômetro, utilizado como um torquímetro operando em elevadas rotações, de forma a manter as soluções em regime turbulento. Mediu-se então, o torque necessário para manter a rotação constante desejada, aumentando linearmente a temperatura do sistema. Determinou-se a temperatura crítica para cada sistema, sendo esta a temperatura em que os sistemas perdem sua capacidade de reduzir o atrito hidrodinâmico. Considera-se que na temperatura crítica, as micelas gigantes sofrem intensa fragmentação. Estudou-se a influência da rotação da geometria de dupla parede nesse tipo de experimento. Foi observado que a eficiência em reduzir o atrito hidrodinâmico diminui em rotações mais reduzidas. Observou-se diferentes perfis de curvas de torque em função da temperatura para experimentos realizados de maneira idêntica e com a mesma solução estoque, sugerindo processos de reorganização estrutural das micelas gigantes, uma vez que a temperatura crítica foi sistematicamente alterada para os diferentes perfis. Além disso, em um experimento semelhante, investigou-se a importância de um cisalhamento prévio, em uma tentativa de isolar os efeitos mecânicos dos efeitos térmicos. Finalmente, ainda no regime turbulento, estudou-se a influência da temperatura inicial e consequente tamanho do agregado para as curvas de redução de atrito. O sistema foi investigado através de experimentos calorimétricos, de tempo de vida fluorescência e de espalhamento de luz, realizados no estado quiescente, ou seja, regime Browniano. Neste regime, não foi possível observar nenhuma transição térmica abrupta como a observada no regime turbulento, caracterizado pela temperatura crítica. Os resultados obtidos pelo espalhamento de luz são condizentes com os modelos que preveem um decréscimo da dimensão das micelas gigantes com a temperatura e concordam com os resultados obtidos pelas demais técnicas. Com base na comparação dos resultados obtidos nos dois regimes, investigou-se neste projeto os efeitos da turbulência sobre a estruturação do agregado micelar Abstract: In this work, we evaluated the drag reduction ability of wormlike micelles formed by TTAB and sodium salicylate or 3,4-dichlorebenzoate. The study was carried using a rheometer, used as a torquimeter operating in high rotational speed, so that turbulent flow was maintained. So, it was measured the torque required to maintain a specific rotation as constant, while increasing the temperature linearly. It was determined the critical temperature for each system, being this temperature in which the drag reducers agents lose their ability to produce such effect. It is considered that the wormlike micelles suffer an intense fragmentation. It was studied the influence of the rotation in this kind of experiment. It was observed that the efficiency to reduce the drag decreases at lower rotational speed. We observed different profiles for the curves of torque as function of temperature, even for experiments carried at the very same way with the same stock solution. Perhaps, it suggests structural variations of the wormlike micelles, since the critical temperature was systematically dependent of the profile. Besides, trying to separate the mechanical effects of the thermal effects, it was investigated the importance of a previous shearing. Finally, we studied the role of the initial temperature, and consequentially the role of the size of the aggregate for the hydrodynamic drag reduction experiments. The system was also investigated by calorimetric experiments, lifetime of fluorescence and dynamic light scattering, being all those techniques done on the quiescent state. In this regime, it was not possible to observe any sudden thermal transition as it was noticed under turbulent flow, characterized by the critical temperature. The results obtained by the DLS technique agrees with the model that describes a decrease in the wormlike micelles as function of the temperature. Also, the DLS results agree with the other results based on the quiescent state. In this work, we investigated comparing the results of both regimes, the role of the turbulent flow on the structural variations of the wormlike micelles Mestrado Físico-Química Mestre em Química CNPQ 134661/2015-0 PETROBRAS