Surge and Swab Calculation Method 1

This is the first method to determine surge and swab pressure.

Learn more about Surge Pressure and Swab Pressure

Surge is additional pressure due to pipe movement downward and swab is reduction of pressure due to upward movement of drill string.

Bottom hole pressure is reduced due to swabbing effect.

Bottom hole pressure is increased due to surging effect.

 

 

The calculation steps are as follows:

1. Determine pressure around drill pipe

2. Determine pressure loss around drill collar

3. Determine total pressure loss by summation of the figures in the 1st and 2nd step

4. Determine surge and swab pressure

 

 

The First Step: determine pressure loss around drill pipe

 

1. Determine n

Where;

n is the power law exponent.

Θ600 is a value at 600 viscometer dial reading.

Θ300 is a value at 300 viscometer dial reading.

 

2. Determine K

Where;

K is the fluid consistency unit

Θ300 is a value at 300 viscometer dial reading.

n is the power law exponent.

 

3. Determine fluid velocity around drill pipe

 

For closed-ended pipe (plugged flow)

 

For open-ended 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.

Di is inner diameter of drill pipe in inch.

 

4. Maximum pipe velocity

 

Vm = Vdp x 1.5

 

Where;

Vdp is the fluid velocity around drill pipe in ft/min.

Vm is maximum pipe velocity.

 

5. Pressure loss around drill pipe

 

The Second Step: determine pressure loss around drill collar

 

You also need to consider pressure loss around drill collar or BHA as well because they have different OD which sometimes creates significant surge/swab pressure.

 

1. Determine fluid velocity around drill collar

 

For close-ended pipe (plugged flow)

 

For open-ended pipe

 

Where;

Vdc is the fluid velocity around drill collar in ft/min.

Dc is drill collar diameter in inch.

Dh is hole diameter in inch.

Dci is inner diameter of drill collar in inch.

 

2. Maximum pipe velocity

 

Vm = Vdc x 1.5

 

Where;

Vdc is the fluid velocity around drill collar in ft/min.

Vm is maximum pipe velocity.

 

3. Pressure loss around drill collar

 

The Third Step: Total Pressure Loss = Pdp + Pdc

 

The Final Step:

 

For surge pressure, you need to add this figure to hydrostatic pressure of mud.

 

Bottom hole pressure = Hydrostatic pressure + Total Pressure Loss

 

On the other hand, if you want to get swab pressure, the pressure sure must be subtracted from the hydrostatic pressure.

 

Bottom hole pressure = Hydrostatic pressure – Total Pressure Loss

 

Reference book: Drilling Formula BookFormulas and Calculations for Drilling, Production and Workover, Second Edition

Related Post

Cutting Slip Velocity Calculation Method 1 Cutting slip velocity is velocity of cutting that naturally falls down due to its density. In order to effectively clean the hole, effect of mud flow ...
Hydrostatic Pressure Loss Due to Gas Cut Mud When you get gas-cut into your drilling mud, it will reduce mud weight causing hydrostatic pressure decrease. The concept of this calculation is to ca...
Determine how many feet of free pipe without free ... You may sometimes find the table for Free Point Constant for your stuck pipe calculation so you use the formula from the previous post to determine Fr...
Drill pipe pulled to lose hydrostatic pressure You previously learn about hydrostatic pressure lose due to pulling out of hole . This post will use the same concept but we will determine how many f...
Share the joy
  • 14
  •  
  •  
  •  
  •  
  •  
  •  
  •  
  •  
    14
    Shares
Tagged , , , . Bookmark the permalink.

About DrillingFormulas.Com

Working in the oil field and loving to share knowledge.

4 Responses to Surge and Swab Calculation Method 1

  1. Rick Gade says:

    I don’t understand why there is a 0.45 added to the ratio of the drill pipe and hole size ratios.

    Vdp = [0.45 + Dp^2/(Dh^2 – Dp^2)] x Vp

    Why shouldn’t it be:

    Vdp = Dp^2/(Dh^2 – Dp^2) x Vp

    Thanks,
    Rick

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.