Summary
A study of cuttings transport at intermediate inclinations using aerated
fluid, to determine the amount of solids that exist in the wellbore and minimum
flow requirements for "clean-hole" condition, is presented. The
experimental program included more than 300 tests, performed with a large-scale
facility [100-ft-long flow loop with 8-in. outer diameter (OD) casing and
4.5-in.-OD drillpipe]. The angles of test section inclination were 30°, 45°,
and 60° from vertical. Four pipe-rotational speeds (0, 40, 80, and 110 rpm)
were used for different liquid-and gas-flow-rate combinations. New correlations
were found to estimate the required critical-gas-flow rates for hole cleaning
at specified liquid-flow rate and drillpipe-rotation combinations, and to
predict volumetric cuttings concentration as a function of air and water flow
rate, drillpipe-rotational speed, and inclination angle.
Introduction
In recent years, two goals of oil and gas production companies have been to
develop new methods to improve hydrocarbon recovery in mature areas and to
exploit new low-pressure/ low-permeability reservoirs. The use of underbalanced
and near-balanced drilling techniques has found applications for these
particular cases.
Cuttings transport is one of the major factors affecting cost, time, and
quality of directional wells. The significant advantages related to drilling
with aerated fluids are reduced by inefficient cuttings transport to the
surface. Specifically, these advantages depend on understanding the interaction
between fluids and the drill cuttings.
Cuttings transport with multiphase fluids is dominated by many variables,
and the interaction of all of these variables adds complexity to this subject.
Because of this, an experimental approach has been selected to accomplish this
investigation.
The understanding of cuttings transport with multiphase fluids is very
limited because the majority of research in cuttings transport has been
conducted with conventional drilling fluids. The study of three-phase flow is
relatively new, and there are not enough studies that consider the transport of
solids with Newtonian gas/liquid mixtures, pipe rotation, and the slip between
phases.
This paper reports on an experimental study of hole cleaning with aerated
fluids at intermediate hole angles considering drillpipe rotation. The main
results of this work are experimental data, empirical correlations, and
observations. It is intended to serve as a guide to the current technology,
explaining how and why the effect of pipe rotation is related to the cuttings
concentration in the wellbore.
© 2008. Society of Petroleum Engineers
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History
- Original manuscript received:
19 August 2004
- Meeting paper published:
2 March 2004
- Revised manuscript received:
16 October 2007
- Manuscript approved:
10 January 2008
- Version of record:
20 June 2008
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