Theoretical Analysis of Drilling Fluid Flow for Maxi-Horizontal Directional Drilling

Accurately determining the flow direction of drilling fluid in maxi-horizontal directional drilling (maxi-HDD) is essential for the precise calculation of parameters such as the minimum pressure required for drilling fluid circulation, volume of return drilling fluid, drag force of the drilling fluid, and borehole pressure. We propose a novel method for determining the flow direction and computing these physical parameters in maxi-HDD using the Bingham plastic model. An engineering case study was conducted to validate the applicability of the method. We analyzed the variation patterns of the minimum pressure required for drilling fluid circulation, flow rate, the drag force of the drilling fluid, and borehole pressure during the pipeline installation process. Furthermore, a parametric study was conducted to assess the influence of factors such as reaming, reaming differential, bentonite concentration, and the elevation difference between the bore entry and exit points on drilling fluid flow. The proposed method considers a wide range of parameters, including flow direction, elevation difference, and other relevant parameters. It offers a comprehensive tool for analyzing drilling fluid flow in maxi-HDD.