This section will show to how to use the formula from the previous topic, surge and swab pressure calculation 2nd method , to determine surge and swab pressure. I still use the same parameters as I used for the first method of surge and swab pressure calculation so you can compare the result between method#1 and method#2.
The well information is listed below:
θ300 = 85
θ600 = 130
Hole diameter = 9 inch
Drill Collar = 6.25 inch
ID of drill collar = 2.5 inch
Drillpipe diameter = 5 inch
ID of drill pipe = 3.5 inch
Average pipe running or pulling speed = 250 ft/min
Drill Pipe Length = 12000 ft
Drill Collar Length = 800 ft
Current Mud Weight = 12.5 ppg
Well TVD = 9000 ft
Determine pressure loss around drill pipe
1. Determine fluid velocity around drill pipe
Vdp = 224.1 ft/min
2. Maximum pipe velocity
Vm = 224.1 x 1.5 = 336 ft/min
3. Determine n
n= 0.613
4. Determine K
K=1.863
5. Determine shear rate of drilling mud moving around drill pipe
Ym = 201.7
6. Determine shear stress of drilling mud moving around drill pipe
T= 1.863(201.7)0.613
T=48.1
7. Determine pressure loss around drill pipe
Pdp = 480.5 psi.
Determine pressure loss around drill collar
1. Determine fluid velocity around drill collar
Vdc = 345.4 ft/min
2. Maximum pipe velocity
Vm = 345.4 x 1.5 = 518 ft/min
3. Determine equivalent flow rate in gpm due to pipe movement
Q=886.8 gpm
4. Determine pressure loss around drill collar
Pdc = 71.8 psi
Note: PV = θ600 – θ300
The summation of pressure loss around drill pipe and drill collar is total pressure loss.
Total pressure loss = 480.5 + 71.8 = 552.2 psi
Determine surge and swab pressure with following equations:
Surge
Surge pressure = Hydrostatic pressure + Total pressure loss
Surge pressure = (0.052 x 9000 x 12.5) + 552.2 = 6402.2 psi
Swab
Swab pressure = Hydrostatic pressure – Total pressure loss
Swab pressure = (0.052 x 9000 x 12.5) – 552.2 = 5297.8 psi
Since we use the same parameters, you compare the result to the first method, surge and swab pressure for close-ended pipe, surge pressure is 6476 psi and swab pressure is 5223 psi. As you can see, both methods figures within less than 2% different.
Reference book: 
Formulas and Calculations for Drilling, Production and Workover, Second Edition
