https://repositorio.ufu.br/handle/123456789/5468 Mon, 28 Sep 2026 00:00:59 GMT 2026-09-28T00:00:59Z https://repositorio.ufu.br/handle/123456789/50346 Title: Um estudo preliminar sobre o envelhecimento de fluidos de perfuração de poços de petróleo Abstract: Drilling fluids play an essential role in the petroleum industry, being responsible for pressure control, wellbore stability, and cuttings transport. During operations, these fluids may remain stagnant under elevated thermal conditions, which can alter their properties and compromise their performance. In this context, the present study aimed to evaluate the effect of accelerated aging on solids sedimentation and the rheological behavior of water-based drilling fluids, as well as to investigate the influence of thermal aging on the behavior of xanthan gum in isolation. For this purpose, fluids supplied by Petrobras (BRCARB10) were used and subjected to aging at 65 °C for 0, 16, 32, and 48 hours. Sedimentation was monitored using the Gamma-Ray Attenuation Technique (TARG), while physicochemical parameters were subjected to one-way ANOVA statistical analysis (α = 0.05). Concurrently, xanthan gum solutions at concentrations of 0.2% and 0.4% (w/w) were aged at different temperatures for isolated polymer analysis. The results showed that the density of fluid BRCARB10 exhibited a statistically significant variation during aging (p = 0.00833), with a reduction between 0h and 32h and a subsequent increase between 32h and 48h, although initial and final values did not differ statistically. Solids concentration, filtrate volume, and salt content parameters remained stable, evidencing the compositional robustness of the system. Rheological analyses indicated an increase in the consistency index and a decrease in the flow behavior index after 48 hours for the drilling fluid, suggesting structural rearrangements that favor solids suspension, confirmed by the absence of significant sedimentation for up to 150 days. Sedimentation tests revealed high gravitational stability, with no concentration gradients forming along the column over long periods. The xanthan gum study evidenced progressive thermal degradation, especially at higher temperatures, characterized by a reduction in the consistency index, an increase in the flow behavior index, and a decrease in the system's restructuring capacity. Thus, this work contributed to observing that moderate thermal aging primarily affects the rheological behavior of the fluids without compromising their sedimentation stability, highlighting the importance of component interactions in maintaining operational performance. Fri, 29 May 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/50346 2026-05-29T00:00:00Z https://repositorio.ufu.br/handle/123456789/50323 Title: Desenvolvimento de fluido aquoso polimérico de baixa densidade com microesferas ocas de vidro para perfuração de poços de petróleo Abstract: Drilling formations with low pore pressure presents a narrow operating window between the pore and fracture pressures, in which a fluid of inadequate density may cause alterations in the well pressure, resulting in lost circulation and reservoir damage. Under these conditions, reduced-density fluids are necessary that, besides counterbalancing the formation pressure, simultaneously meet filtration, rheology and gel strength criteria. The incorporation of hollow glass microspheres, low-density particles, is an effective strategy for this reduction, but it simultaneously alters these properties, requiring the adjustment among the fluid components. In this work, a study was developed on an aqueous polymeric fluid containing hollow glass microspheres, in two stages. In the first stage, an operational feasibility analysis was carried out with a drill-in fluid, in which the maximum technically sustainable density reduction was 0.50 ppg, with 18 lb/bbl of microspheres; however, field logistics constraints limit this reduction to 0.25 ppg for production volumes between 5,000 and 7,000 bbl. In the second stage, an aqueous polymeric fluid saturated with NaCl was optimized by Central Composite Design (CCD) and Differential Evolution. The CCD was conducted with four independent factors: xanthan gum, HPA, calcium carbonate and hollow glass microspheres; totaling 27 experimental formulations, from which second-order empirical models were fitted for eleven responses: density, filtrate volume, L600, L300, L200, L100, L6, L3, gel strength at 10 seconds, 10 minutes and 30 minutes. For density, the fitted model was linear, with calcium carbonate and microspheres acting independently of each other and as the only significant factors. The shear-rate reading models showed good fit, with xanthan gum as the dominant factor, and the gel strength models reflected the greater complexity and intrinsic variability of this property. The filtrate volume remained below 10 mL in all formulations. From the fitted models, a formulation was identified by optimization that reached a density of 9.10 ppg and a filtrate volume of 1.4 mL, with high- and medium-shear-rate readings within the operational ranges and low-shear readings close to the lower limit. The absence of calcium carbonate in the optimal formulation shows that hollow glass microspheres associated with the xanthan gum polymeric matrix are sufficient to meet the operational criteria of density, rheology and filtration in the investigated domain. Mon, 20 Jul 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/50323 2026-07-20T00:00:00Z https://repositorio.ufu.br/handle/123456789/50304 Title: Caracterização e conversão termoquímica de resíduo de jatobá via pirólise assistida por micro-ondas com e sem catalisadores Abstract: This work investigated the microwave-assisted pyrolysis of jatobá (Hymenaea courbaril) bark, an abundant agro-industrial residue from the Brazilian Cerrado, aiming at the production of bio-oil and biochar. The biomass was characterized regarding proximate and ultimate composition, calorific value, and thermal behavior. The non-catalytic pyrolysis experiments, conducted in a microwave oven (2.45 GHz, 1000 W), followed a central composite design to evaluate the effects of temperature (451–649 °C) and residence time (10.1–34.9 min) on the products. Catalytic pyrolysis was carried out under the optimized condition, using catalysts (CaO, KOH, HZSM-5) in a single bed supported on SiC foam, in an ex situ configuration. The products were analyzed by GC-MS, FTIR, XRF, TGA, and SEM. The characterization of jatobá bark revealed low moisture (8.52%) and ash (1.52%) contents, high volatile matter (77.42%), and a higher heating value of 21.10 MJ/kg. The optimized condition (550 °C, 34.9 min) resulted in a bio-oil yield of 57.77% and a hydrocarbon (HC) content of approximately 50%. The produced bio-oils showed a predominance of aromatic hydrocarbons, with temperature influencing the formation of monocyclic compounds at the expense of polycyclic ones. Catalytic pyrolysis with CaO increased the HC fraction to 66.8% and reduced oxygenates to 28.1%, demonstrating the effectiveness of catalysis in bio-oil deoxygenation. The obtained biochar presented a high fixed carbon content (38.68%), calorific value of up to 22.76 MJ/kg, and a porous surface, with the presence of nutrients (K, Ca, Mg, P). It is concluded that jatobá bark is a promising biomass for the production of bio-oil and biochar via microwave-assisted pyrolysis, with the use of CaO catalyst representing an effective strategy for obtaining hydrocarbon-rich bio-oil, showing this as a sustainable technological route aligned with the principles of the circular economy.; Este trabajo investigó la pirólisis asistida por microondas de la cáscara de jatobá (Hymenaea courbaril), un residuo agroindustrial abundante en el Cerrado brasileño, con el objetivo de producir bioaceite y biocarbón. La biomasa fue caracterizada en cuanto a su composición inmediata, elemental, poder calorífico y comportamiento térmico. Los experimentos de pirólisis no catalítica, realizados en un horno de microondas (2,45 GHz, 1000 W), siguieron un diseño compuesto central para evaluar los efectos de la temperatura (451–649 °C) y del tiempo de residencia (10,1–34,9 min) sobre los productos. La pirólisis catalítica se llevó a cabo en la condición optimizada, utilizando catalizadores (CaO, KOH, HZSM-5) en lecho único soportados en espuma de SiC, en configuración ex situ. Los productos fueron analizados por GC-MS, FTIR, FRX, TGA y SEM. La caracterización de la cáscara de jatobá reveló bajo contenido de humedad (8,52 %) y cenizas (1,52 %), alto contenido de volátiles (77,42 %) y un poder calorífico superior de 21,10 MJ/kg. La condición optimizada (550 °C, 34,9 min) resultó en un rendimiento de bioaceite del 57,77 % y un contenido de hidrocarburos (HC) de aproximadamente el 50 %. Los bioaceites producidos presentaron predominio de hidrocarburos aromáticos, influyendo la temperatura en la formación de compuestos monocíclicos en detrimento de los policíclicos. La pirólisis catalítica con CaO elevó la fracción de HC al 66,8 % y redujo los oxigenados al 28,1 %, demostrando la eficacia de la catálisis en la desoxigenación del bioaceite. El biocarbón obtenido presentó un alto contenido de carbono fijo (38,68 %), poder calorífico de hasta 22,76 MJ/kg y superficie porosa, con presencia de nutrientes (K, Ca, Mg, P). Se concluye que la cáscara de jatobá es una biomasa prometedora para la producción de bioaceite y biocarbón mediante pirólisis asistida por microondas, siendo el uso del catalizador CaO una estrategia eficaz para obtener bioaceite rico en hidrocarburos, mostrando esta como una ruta tecnológica sostenible y alineada con los principios de la economía circular. Fri, 31 Jul 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/50304 2026-07-31T00:00:00Z https://repositorio.ufu.br/handle/123456789/50264 Title: Produção de biomassa de Saccharomyces cerevisiae em meios de cultivo à base de melaço de cana-de-açúcar: avaliação de regimes de alimentação e aeração Abstract: The growing demand for sustainable alternatives for the valorization of agro-industrial by- products has stimulated the development of biotechnological processes aimed at microbial biomass production. In this context, sugarcane molasses stands out as a low-cost and widely available carbon source that can be employed for yeast cultivation, generating biomass with potential applications in animal nutrition. The present study evaluated biomass production by industrial strains of Saccharomyces cerevisiae cultivated on commercial sucrose and sugarcane molasses, with emphasis on the effects of different operational strategies on metabolic regulation and substrate-to-biomass conversion efficiency. Initially, a physiological screening of five industrial strains (Y904, PE-2, PhibroADY, Ethanol Red, and FT858) was performed in batch cultures, leading to the selection of strain FT858 for subsequent experiments. Cultivations were then carried out in a bench-scale bioreactor under different feeding regimes, aeration conditions, and oxygen supply conditions. The results demonstrated that oxygen availability was the most influential factor affecting the physiological performance of the selected strain. Replacing compressed air with pure oxygen increased biomass yield by 301%, from 0.069 to 0.277 g·g−1. In cultures conducted with sugarcane molasses using pure oxygen, increasing the aeration from 0.5 to 1.67 vvm improved biomass yield from 0.157 to 0.255 g·g−1 while reducing ethanol formation. Conversely, fed-batch strategies that promoted residual sugar accumulation intensified the Crabtree effect, decreasing the efficiency of substrate conversion into biomass. Under the selected cultivation conditions, the biomass exhibited a crude protein content of 40.5 ± 1.9% on a dry-weight basis, highlighting its potential for application in animal feed formulations. Overall, the findings demonstrate that the simultaneous control of carbon availability and oxygen supply is essential to maximize biomass production by strain FT858 when cultivated on sugarcane-derived substrates. Thu, 16 Jul 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/50264 2026-07-16T00:00:00Z