Abstract:
Increasing the cuttings transport performance in deviated wells is difficult due to the rolling transport and cuttings settling on the low side of the annulus. Insufficient cuttings transport may lead to some crucial problems such as pipe sticking, increasing in torque and drag, material damage and bed cementing quality. Increasing flow rates and improving mud properties may not be applicable for a proper hole cleaning because of the hydraulic and mechanical limitations. In such cases, additional pressure may be generated, and this causes formation fractures and drilling fluid losses. Under these circumstances, the other major contribution to cuttings transport is provided by drill-pipe rotation for different eccentricity. This project describes the relation between hole eccentricity and rotation during cuttings transport through annular bends.
The present study focused on the development of a computational fluid dynamics model to predict these parameters conveniently and accurately. Two phases—liquid (water) and cuttings (sulfur solid)—were considered. The simulations were conducted using the workbench platform of ANSYS Fluent 2021 R1. The Eulerian model of multiphase flow and the Reynolds stress model of turbulence closure available in Fluent were used for the present study. The average velocities and volumetric concentrations of involved phases were specified as the inlet boundary conditions. The stationary surfaces of the flow channels were hydrodynamically considered as either smooth or rough walls, and the outlets were regarded as being open to the atmosphere. The simulation results of pressure loss showed a good agreement with the predictions of well-established correlations.
From the simulated results, this project concludes that drill cuttings transport efficiency depends on hole eccentricity and drill pipe rotation of the models where pressure and VOF of cuttings are maximum with minimum pressure drop. For eccentricity 0.4 with 200 rpm simulation shows maximum pressure at outlet with maximum cuttings VOF and also shows minimum pressure drop than other models at outlet.
