Abstract

In ultra-deep and large well sections, high collapse stresses and diminished annular return velocity present significant challenges to wellbore cleaning. With increasing depth, rising temperature and pressure constrain the regulation of displacement and drilling fluid rheology, impairing the fluid’s capacity to transport cuttings effectively. A precise understanding of cuttings settlement behavior and terminal velocity is therefore essential for optimizing their removal. This study accounts for variations in wellbore temperature and pressure, incorporates non-spherical cuttings and wellbore diameter parameters, and develops accordingly a simplified model to predict terminal settlement velocity. The cuttings carrying ratio is introduced as a metric for evaluating wellbore cleanliness. Findings reveal that temperature and pressure fluctuations can alter terminal velocity by up to 3.4%. Cuttings shape plays a crucial role, with block-shaped cuttings requiring higher annular return velocity than flake-shaped ones at the same carrying ratio. As wellbore size increases, the minimum required carrying flow rate rises nonlinearly, though the rate of increase gradually declines. For a Φ444.5 mm wellbore, a carrying ratio of at least 0.6 is recommended. Terminal velocity decreases with increasing consistency coefficient, particularly in high-viscosity regimes. The proposed carrying ratio offers a more accurate and practical assessment of wellbore cleanliness.

Details

Title
Hole Cleaning and Critical Transport Rate in Ultra-Deep, Oversized Wellbores
Author
Li, Yuyao; He, Mingmin; Cai, Mingjie; Xu, Shiqian
Pages
799-817
Section
ARTICLE
Publication year
2025
Publication date
2025
Publisher
Tech Science Press
ISSN
1555-256X
e-ISSN
1555-2578
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
3203294309
Copyright
© 2025. This work is licensed under https://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.