Changes

''Annular velocity'' is the average speed at which the drilling fluid is moving back up the annular space as the well is circulated. Although the mud pump output remains constant, annular velocities vary at different points in the wellbore due to changes in pipe, collar, and hole sizes. Annular velocity (AV) can be calculated as

''Annular velocity'' is the average speed at which the drilling fluid is moving back up the annular space as the well is circulated. Although the mud pump output remains constant, annular velocities vary at different points in the wellbore due to changes in pipe, collar, and hole sizes. Annular velocity (AV) can be calculated as

:<math>\mbox{AV} = (24.5 \times \mbox{GPM})/(\mbox{Dh}^{2} - \mbox{od}^{2})</math>

:<math>\mbox{AV} = \frac{24.5 \times \mbox{GPM}}{\mbox{Dh}^{2} - \mbox{od}^2}</math>

'''''Example''''': If mud is circulated at 400 gal/min in an 8.5-in. hole containing a 4.5-in. drill pipe and 6.5-in. collars, the annular velocities are

'''''Example''''': If mud is circulated at 400 gal/min in an 8.5-in. hole containing a 4.5-in. drill pipe and 6.5-in. collars, the annular velocities are

:<math>\mbox{Drill pipe: AV} = (24.5 \times 400)/(8.5^{2} - 4.5^{2}) = 188.5\mbox{ ft/min}</math>

:<math>\mbox{Drill pipe: AV} = \frac{24.5 \times 400}{8.5^2 - 4.5^2} = 188.5\mbox{ ft/min}</math>

:<math>\mbox{Collars: AV}  = (24.5 \times 400)/(8.5^{2} - 6.5^{2}) = 326.7 \mbox{ ft/min}</math>

:<math>\mbox{Collars: AV}  = \frac{24.5 \times 400}{8.5^2 - 6.5^2} = 326.7 \mbox{ ft/min}</math>

===Jet nozzle area===

===Jet nozzle area===