This is another method for calculating surge and swab pressure. With this method, there are 3 assumptions as follows:
• Closed ended pipe (plug flow)
• Laminar flow around drill pipe
• Turbulent flow around drill collar
How to determine surge and swab pressure with this method
1. Determine pressure around drill pipe
2. Determine pressure around drill collar
Note: The calculation methodology is different from the first method because both pressure losses are determined by separate set of equations.
3. Determine total pressure loss by summation of step 1 and step 2
4. Determine surge and swab pressure
Determine pressure loss around drill pipe by following calculations
1. Determine fluid velocity around drill pipe
Where;
Vdp is the fluid velocity around drill pipe in ft/min.
Vp is pipe movement velocity in ft/min.
Dp is drill pipe diameter in inch.
Dh is hole diameter in inch.