Another equation to determine equivalent circulating density is to use yield point.
This formula below is used to calculate the ECD and it is good for mud weight more than to 13.0 ppg
ECD is equivalent circulating density in ppg.
MW is mud weight in ppg.
Hold ID is inside diameter of hole in inch.
Pipe OD is outside diameter of pipe in inch.
YP is mud yield point.
YP can be calculated by these following equations.
YP = Reading at 300 rpm – PV
PV = Reading at 600 rpm – Reading at 300 rpm
AV is annular velocity in ft/min
AV can be determined by the following equation.
AV in ft/min = (24.5 x Q) ÷ (Dh2 – Dp2)
Q = flow rate in gpm
Dh = inside diameter of casing or hole size in inch
Dp = outside diameter of drill pipe, drill collars, or tubing in inch
Determine the ECD with the following information
MW = 13.5 ppg
Reading at 300 = 25
Reading at 600 = 40
Hole diameter = 6.2
Pipe diameter = 4
Flow rate = 200 gpm
AV in ft/min = (24.5 x 200) ÷ (6.22 – 42) = 218.4 ft/min
PV = 40 – 25 = 15
YP = 25- 15 = 10
ECD = 14.2 ppg
If you have mud weight less than 13 ppg, please read this article ” Equivalent Circulating Density (ECD) Using Yield Point for MW less than 13 ppg ”
Additional articles about Equivalent Circulating Density (ECD) are as follows: