Drilling rate, factors affecting

Factors Affecting Drilling Rates 1090. Selection of Weight on Bit, Rotary Speed, and Drilling Time 1091. Selection of Optimal Nozzle Size and Mud Flowrate 1097. 

Marken et al. (110) have given a detailed account of the factors affecting annular pressure losses, including the effects of rotational flow in the annulus. It might be expected that rotational flow in the annulus would decrease the frictional pressure losses as the increased shear rate would lower the viscosity. However, Marken et al. observed an increase in frictional pressure due to the formation of Taylor vortices. McCann et al. (J07) have observed increases in the frictional pressures in slimhole annuli due to annular rotation of the drilling fluid. 

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