CFD Calculations of Cuttings Transport through Drilling Annuli at Various Angles

摘要

Efficient transportation of cuttings is a vital factor for a good drilling program. Cutting transport in annulus is a complex problem that is affected by numerous parameters. Predicting effective cuttings transport requires all of these parameters to be considered simultaneously. To better understand the effects of some of the parameters affecting the cutting transportation, Reynolds-Averaged Navier-Stokes or k-epsilon turbulent model, the Navier-Stokes equations, the continuity equation and the power law of non-Newtonian viscosity model were adopted to establish the mathematical model of the cutting transport process in the annulus of the well. The constants of the power law model were evaluated experimentally for three different mud types. The CFD simulation to solve the governing equations was carried out by using ANSYS (FLUEN T) commercial code. A combination of hole-drill pipe annulus section was simulated and a model called "Discrete phase model" was used to observe the transportation of cuttings in the annulus. CFD computations were conducted to determine the effects of annular flow behavior, drilling fluid shear thinning behavior, cutting size and shape on cutting transportation in various orientation of a well bore. In directional drilling, where an eccentric annulus is often used, there is tendency for the cuttings to accumulate in the narrowest gap where the velocity is lowest. Since turbulence tends to suppress such accumulation, knowledge of the velocity profiles in the annulus are essential in the design and operation of these drills. This work evaluates the performance of the numerical method used, comparing the results obtained with those in other reported works, aiming to validate the simulation strategy by the interpolation routines as well as the couplings algorithms adopted.