The CCI was developed empirically to provide a fast method of determining whether a vertical hole (<35 degrees) was being cleaned sufficiently to avoid trouble. The index should be at or above 1.0 to avoid trouble. The equation for calculating the index is:
CCI = ( MW * AV * K ) / 400,000
MW = Mud Weight, ppg
AV = Annular velocity, fpm
K = Low shear rate viscosity, "equivalent centipoise"
K may be calculated from:
K= 511^(1-n) * ( PV + YP ) .............( ^ denotes raising to the power, * denotes multiplication of 511^(1-n) )
YP= Yield Point, lbf / 100 sq.ft.
PV=Plastic Viscosity, cp
n = 3.322 * Log [ ( 2 * PV + YP ) / ( PV + YP ) ]
Note that the calculation tedium lies in the calculation of K. K is a function of PV and YP only. Hence, a graph can be constructed where K can be read off the Y axis, when given an input of YP (X axis) and PV (families of lines on the cartesian plot below). An Excel spreadsheet is also available...email your request for it below.
For comments or information regarding the origin of the above, please contact Dr. Leon Robinson.
For more information or a fax of the plot above, contact Mark Ramsey. He can be reached at :
Office: voice - 281-320-2999.
Don't even bother with "snail mail".