Cuttings transport: On the effect of drill pipe rotation and lateral motion on the cuttings bed

Alexander Busch,Stein Tore Johansen

doi:10.1016/j.petrol.2020.107136

Alexander Busch, Stein Tore Johansen

Open Access

https://doi.org/10.1016/j.petrol.2020.107136

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Abstract

Drill pipe rotation is considered a relevant factor for cuttings transport and hole cleaning. However, in the term “rotation” is often used as a moniker for the combination of plain drill pipe rotation around its own axis and more complex lateral motion, as many laboratory setups feature an unconstrained drill string. Lateral motion is generally considered to benefit the transports of cuttings due to increased bed agitation. By means of Computational Fluid Dynamics, we have investigated the effect of synchronous and asynchronous whirling drill string motion on the cuttings bed and cuttings transport for water and a more viscous, shear-thinning fluid using the Two Fluid Model in conjunction with the Kinetic Theory Of Granular Flows and closures from soil mechanics to rheologically describe granular matter. The dynamic mesh capability of ANSYS Fluent R17.2 is exploited to account for the orbital motion of the drill string. In addition, three base cases (negative eccentric, concentric, and positive eccentric) are investigated for comparison. Whirling motion helps tremendously to disperse the solids into the main flow region and hence improves the quality of cuttings transport and hole cleaning, with synchronous whirl by far outperforming asynchronous whirl due to the cumulative tangential and radial velocities. The effect is much more prominent for water than for the more viscous, shear-thinning fluid because the latter already shows a comparatively good cuttings transport performance. Moreover, in case of the more viscous, shear-thinning fluid, the positive eccentric annulus provides an even better cuttings transport capability, if comparison is made on equivalent pressure gradients. Because of the higher viscosity level, the whirling motion reduces the axial throughput, which despite the increased bed agitation results in worse performance compared to the positive eccentric case.

Highlights

In petroleum drilling, solid particles are generated by the drill bit which is being pushed downhole with a certain rate of pene tration (ROP)
The whirling motion occurs in opposite direction of the drill pipe rotation and the angular velocity of the whirl motion is given by ωw 1⁄4 -dj/doωp, where dj is the diameter of the tool joints
In addition to the cuttings transport ratio (CTR) 1⁄4 f(rpm, dp=dx), we provide the results in the form ROP 1⁄4 f(rpm, dp=dx), where ROP is related to the superficial solid velocity as the nominator of the CTR as follows: In a real field scenario at steady-state, the superficial velocity of the solids Uss is determined by the ROP, the bit diameter Do, and the rock porosity αr as a consequence of mass conservation

Summary

Introduction

Solid particles (cuttings) are generated by the drill bit which is being pushed downhole with a certain rate of pene tration (ROP). Due to the relevance of cuttings transport to the drilling industry, these have been the subject of many experimental studies Han et al, 2010; Larsen, 1990; Sanchez et al, 1999; Tomren et al, 1986) over the last decades as well as numerical, or more precisely Computational Fluid Dynamics (CFD) studies Due to the relevance of cuttings transport to the drilling industry, these have been the subject of many experimental studies (Avila et al, 2008; e.g. Han et al, 2010; Larsen, 1990; Sanchez et al, 1999; Tomren et al, 1986) over the last decades as well as numerical, or more precisely Computational Fluid Dynamics (CFD) studies (e.g. Akhshik et al, 2015; Epelle and Gerogiorgis, 2017; Heydari et al, 2017; Pang et al, 2019, 2018) in recent years

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