THE EFFECT OF DRILLPIPE ROTATION ON ANNULAR FRICTIONAL PRESSURE LOSS

Accurate predictions of annular frictional pressure losses (AFPL) are important for optimal hydraulic program design of both vertical and ho rizontal wells. in this study, the effects of drillpipe rotation on AF PL for laminar, helical flow of power law fluids are investigated thro ugh theoretical, experimental, and field data studies. in the theoreti cal study, flow models were developed for concentric and eccentric pip e configurations assuming that pipe rotates about its axis. A hybrid-a nalytical solution is developed for calculating AFPL in eccentric pipe configuration. Computer simulations indicate that the shear-thinning effect induced by pipe rotation results in reduction of AFPL in both c oncentric and eccentric pipe configurations. The pressure reduction is most significant for concentric pipe configuration. For conventional rotary drilling geometry and pipe rotary speeds, the reduction in AFPL is small. A number of laboratory experiments conducted on the full-sc ale TUDRP-flow loop are generally in good agreement with the results o f modeling. Available field data, however, consistently show art incre ase in AFPL. This behavior is explained by pipe lateral movement (swir ling), which causes turbulence and eventually an increase in AFPL.