Estudo da sedimentação e acomodação de partículas em sistemas submetidos a gradientes de temperaturas

Abstract

Sedimentation is a widely used process in industry, encompassing various sectors. Among the factors that influence its efficiency, temperature plays a decisive role in solid-liquid separation. A notable example occurs in oil well drilling, where the drilling fluid is subjected to heating due to geothermal conditions, with a temperature increase as the well depth increases. During interruptions in drilling fluid circulation, suspended particles tend to settle, which can compromise well integrity. In this context, this work investigated the behavior of sedimentation and particle arrangement in systems subjected to different thermal conditions, with emphasis on the formation and structure of the sediment bed. The main objective was to evaluate the behavior of the sediment bed as a function of the sedimentation temperature, considering both isothermal conditions and scenarios with thermal gradients, in systems containing only water as well as more complex fluids, such as drilling fluids. For this purpose, systems containing calcium carbonate suspensions in water and drilling fluids with different solid concentrations were prepared. The analyses included sedimentation tests under isothermal conditions and with horizontal and vertical temperature gradients. The solid concentration profile was determined using the gamma-ray attenuation technique, a non-destructive method that allows the assessment of the solids concentration distribution in the sediment bed. The results indicate that increasing the temperature accelerates the sedimentation process, reduces fluid viscosity, and alters the structure of the sediment bed by promoting sediment expansion. In systems with thermal gradients, particle migration towards heated regions and the formation of asymmetric beds with concentration variations along the horizontal axis were observed. In drilling fluids, temperature directly influenced rheology and resistance to sedimentation, with significant differences observed between the samples analyzed. This research contributes to the understanding of thermal effects on sedimentation, providing insights for the design and operation of industrial systems where temperature variations are relevant, such as in oil well drilling.