Fluidic Drag Estimation in Horizontal Directional Drilling Based on Flow Equations

Abstract

Horizontal directional drilling (HDD) is a trenchless technology used to install underground utilities. The force required to pull a pipe through the borehole during installation is crucial to design engineers. Various methods have been proposed to estimate the pullback load, each dealing with fluidic drag in a different way. Limitations in fluidic drag estimation by current design procedures have revealed the significance of having a reliable method for calculation. This paper proposes a new method to calculate fluidic drag based on annular flow equations. This method is used to calculate viscous drag for two HDD case studies, and the results are compared to the estimations by current methods, such as PRCI and ASTM F1962. Pullback load estimation based on the new method agrees well with the actual installation loads. This paper also investigates the impact of design factors on fluidic drag by presenting a sensitivity analysis over a practical range of related parameters. The ratio of pipe radius to borehole radius is observed to have the most influence on fluidic drag.