Abstract

The influence of rotational speed and eccentricity of the drill pipe as well as the effect of fluid flow rate on the accumulation of cuttings in the horizontal annulus are the focus of this study. Computational Fluid Dynamics (CFD) is utilized to model a horizontal annulus section which conveys solid-liquid two-phase flow at different drilling conditions. In this numerical study, the Eulerian multiphase flow model has been adopted for solidliquid characteristics analysis. Here the basic continuity and momentum equations have been considered, which have further been reduced to solve the conservation of mass and momentum equations with appropriate boundary and initial conditions. The study has considered the transient, turbulent model (k-epsilon) with no-slip conditions at pipe walls as well as velocity inlet and pressure outlet at the boundaries. The result indicates the clear impact of rotational speed on the cuttings removal process in the horizontal annulus section. As the rotational speed of the drill pipe increases, the cuttings concentration drops down significantly in the annulus section. Around 20% less accumulation is noticed if the drill pipe rotation is increased from 0 RPM to 120 RPM, which happens due to momentum created by the rotation that does not allow the particles to be accumulated. The eccentricity has a significant impact on solid accumulation as well. However, with increased flow rate and eccentricity, the pressure across the annulus section drops substantially. The difference in pressure drop is noticed as much as around 61 Pa/m with the flow rate change. Consequently, a higher pressure drop per length for the higher velocity of fluid implies higher pumping power consumption. The findings from this study may help to understand the optimum operating conditions for horizontal drilling. The effects of drilling conditions are identified and the complex multiphase flow in the annulus is modeled that could be extended to further related studies.

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