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AuthorMohamed A.
AuthorAl-Afnan S.
AuthorElkatatny S.
AuthorHussein I.
Available date2022-04-25T10:59:46Z
Publication Date2020
Publication NameSustainability (Switzerland)
AbstractBarite sag is a challenging phenomenon encountered in deep drilling with barite-weighted fluids and associated with fluid stability. It can take place in vertical and directional wells, whether in dynamic or static conditions. In this study, an anti-sagging urea-based additive was evaluated to enhance fluid stability and prevent solids sag in water-based fluids to be used in drilling, completion, and workover operations. A barite-weighted drilling fluid, with a density of 15 ppg, was used with the main drilling fluid additives. The ratio of the urea-based additive was varied in the range 0.25–3.0 vol.% of the total base fluid. The impact of this anti-sagging agent on the sag tendency was evaluated at 250 °F using vertical and inclined sag tests. The optimum concentration of the anti-sagging agent was determined for both vertical and inclined wells. The effect of the urea-additive on the drilling fluid rheology was investigated at low and high temperatures (80 °F and 250 °F). Furthermore, the impact of the urea-additive on the filtration performance of the drilling fluid was studied at 250 °F. Adding the urea-additive to the drilling fluid improved the stability of the drilling fluid, as indicated by a reduction in the sag factor. The optimum concentration of this additive was found to be 0.5–1.0 vol.% of the base fluid. This concentration was enough to prevent barite sag in both vertical and inclined conditions at 250 °F, with a sag factor of around 0.5. For the optimum concentration, the yield point and gel strength (after 10 s) were improved by around 50% and 45%, respectively, while both the plastic viscosity and gel strength (after 10 min) were maintained at the desired levels. Moreover, the anti-sagging agent has no impact on drilling fluid density, pH, or filtration performance
SponsorThis research received no external funding. The authors wish to acknowledge King Fahd University of Petroleum and Minerals (KFUPM) for allowing them to utilize various facilities in carrying out this research. Many thanks are due to the anonymous referees for their detailed and helpful comments.
concentration (composition)
deep drilling
drilling fluid
temperature effect
testing method
TitlePrevention of barite sag in water-based drilling fluids by a urea-based additive for drilling deep formations
Issue Number7
Volume Number12

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