Escolamento laminar de líquidos não-newtonianos em seções anulares: estudos de CFD e abordagem experimental

Abstract

The annular flow has great importance in the oil industry, in drilling operations with cuttings removal by drilling mud and also in petroleum artificial lifting, with progressive cavity pumping systems. The constant concern about operation costs and the more frequent necessity of raising the production capacity implies in larger flow through oil wells. In this way the pressure drop through the annular region started to represent a significant amount of the overall energy to be supplied, consequently its prediction assumed an important role in the dimensioning of these units. In the present study, the flow field analysis was based on experimental approach and also applying numeric techniques of computational fluid dynamics (CFD). In the experimental part, a pilot unit was assembled to investigate the horizontal flow of non-Newtonian liquids though the annular space formed by two tubes with concentric and eccentric layouts. The planned experimental assays were conduced to evaluate the effect of the main variables over the pressure drop, such as: system geometry (e=0,00; e=0,75), shaft rotation (0 < W < 600 RPM), polymeric concentration (0,25 < CP < 0,55 %) and fluid flow (0,2 < Q < 2,2 m3/h). This work also contemplates, through commercial CFD codes simulations, the investigation of experimental conditions by analyzing the profiles: of pressure drop, entrance length, axial and tangential velocities and flow trajectories. Considering that these variables are relevant to the whole understanding of drilling mud flow and cuttings transport. The comparison between the results obtained by the two techniques showed good agreement, allowing a satisfactory performance valuation of the numeric technique. The prediction capacity was also observed considering some experimental results reported in the literature, in order to verify the adopted mathematical models, the coupling algorithms and the computational grid used.