Fluid rheology and its implications for flow and cuttings transport in horizontal directional drilling (HDD) bores
Fluid rheology and its implications for flow and cuttings transport in horizontal directional drilling (HDD) bores
Common misconceptions about the appropriate fluid properties for horizontal directional drilling (HDD) often lead to inefficient hole cleaning strategies increasing the risk of hydrofractures, ground heave and mud loss, with significant cost and programme implications. This paper explores the fundamentals of flow behaviour in HDD showing that in-bore flow rates and hence fluid shear strain rates are so low that the traditional Bingham fluid model based on 300 and 600 rpm data from a Fann-type direct indicating viscometer is not valid. An example involving HDD bores for cable landfall of an offshore windfarm is discussed to illustrate the practical consequences of the cuttings transport processes. Analysis of rare annular pressure monitoring data has provided valuable insights into the cuttings behaviour in the bore. The importance of fluid property and pressure monitoring, and having a coherent hole cleaning strategy are highlighted. The paper concludes with recommendations to minimise the risks of hydrofracture and bore blockage.
S. P. C. Che; Christopher O. Menkiti; S. A. Jefferis
18th European Conference on Soil Mechanics and Geotechnical Engineering (ECSMGE2024)
D - Current and new construction methods
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