A term “C” represents the general coefficient for annulus around drill pipe and drill collar and the equation is as follow:
Dh = hole diameter, inch
Do = Outside diameter of drill pipe or drill collar, inch
B = a parameter which takes into account the difference between Q1.86 and Q2
This term does not consider the different between size of tool joint and pipe which affect pressure drop in the annulus. This topic will demonstrate equations to get more accurate coefficient.
Coefficient of Annulus around Drill Pipe and Tool Joint
In order to get an accurate annulus pressure drop around a drill string, the coefficient for the annulus around tool joint must be taken in to account.