Estimation of Hydrokinetic Pressure and Fluidic Drag Changes during Pipe Installations via HOD Based on Identifying Slurry-Flow Pattern Change within a Borehole
This paper proposes a new method for hydrokinetic pressure and fluidic drag evaluation of non-Newtonian power-law slurries flowing within a borehole during horizontal directional drilling (HDD) pipe installation operations. The method divides the bore path into three segments, each associated with a different st.age of slurry flow pattern. For each stage, assuming the product pipe and drill rod to be placed concentrically within the borehole, a set of coupled equations governing slurry flow within the borehole is derived. Then, to obtain the hydrokinetic pressure and fluidic drag history, the equations are solved at the desired product pipe leading head locations within a given segment For two actual HDD installations completed in Alberta, Canada, the pullback forces have been collected and are compared against those estimated by the new proposed method and Pipeline Research Council International (PRCI) method. It is demonstrated that the new method can more accurately estimate the pullback forces.