The study of compressibility in deformable porous media is of interest in many industrial processes, such as, filtration, thickening and during oil well drilling processes in the petrochemical sector. In this work the compressibility of porous media was evaluated by the comparison of solid concentration profiles in sediments using fluids with Newtonian and non-Newtonian behavior. For this, consolidation tests in distillated water, solutions of xanthan and glycerol were performed in a vertical column from the gravitational settling of suspensions. The porosity distribution in the formed sediment was obtained after the complete settling of particulate material. The local porosity measurements were performed using the ionizing radiation emitted by americium-241. The gamma-ray attenuation technique used in this study allowed the realization of nondestructive measurements for achieving local concentration of solids. The results showed that the rheological behavior of the fluid does not change significantly the compressibility of the porous matrix.
A adição de carbonato de cálcio nos fluidos de perfuração é uma prática comum durante a etapa de perfuração de poços de petróleo. Estes aditivos usualmente chamados de agentes obturantes auxiliam na formação de uma camada fina e de baixa permeabilidade denominada reboco. A formação do reboco ocorre na superfície das paredes do poço, auxiliando na redução do influxo de fluido de perfuração para o interior do reservatório. Para a descrição do escoamento de fluidos em meios porosos deformáveis, a determinação da equação constitutiva para permeabilidade do meio poroso é imprescindível, tornando possível a simulação da operação. Nesse contexto, este trabalho determinou as relações existentes entre porosidade e permeabilidade de meios porosos constituídos por carbonatos de cálcio 2-44 µm. A distribuição porosidade no sedimento foi determinada com a técnica de atenuação de radiação gama. Os resultados indicaram diferenças significativas, quando comparados com os valores estimados pela correlação proposta por Kozeny-Carman.
The study of the sedimentation of particulate materials is of interest in several industrial processes, such as in the design and optimization of operating conditions of thickeners and during the operational stages of drilling oil wells. In this context, this work aims to study the sedimentation of particles in viscous Newtonian fluids. For the tests, aqueous solutions of glycerol were used in the volumetric concentration of 80% and 92%. The suspensions were prepared using sand with the size range of 150-212 μm. The settling of particles was studied by using a nondestructive technique based upon the measurement of gamma-ray attenuation for achieving the local concentration of solids. The results showed that the sedimentation velocity of particles was changed significantly with increasing fluid viscosity. Moreover, the dynamic behavior of the particles settling in both glycerol solutions showed similar, with two regions of varying concentration of solids very defined: one in which the solids concentration remained constant until the transition from descending clarified interface; and the other in which the concentration remained constant until the formation of sediment.
The study of filtration and thickening of particulate systems are used in many industrial processes involving processes of solid-liquid separation, such as in sedimentation ponds, filters, the drilling of oil wells, among others. This paper aims to advance the empirical mechanisms involved in the processes of solid-liquid separation and obtain constitutive equations relating the pressure in solids and porous media permeability from non-Newtonian fluids. In the experiments used aqueous solutions of xanthan gum concentration of 0.1% in weight basis in order to ensure non-newtonian means. For the preparation of suspensions, was used calcium carbonate as particulate material in the separation process involved an initial concentration of 12% by volume. The concentrated sediment was maintained between 30 and 48% by volume. Settling tests were carried to term and sediments resulting from each test were evaluated by making use of the Gamma Rays Attenuation Technique (GRAT). The results show that GRAT is effective in determining sediment concentration distributions formed from non-Newtonian solutions, allowing the constitutive equations to obtain pressure and the solid porous medium permeability, very important for simulations of solid-liquid separation processes.
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