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.

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