Slug Calculation in Barrels for a Length of Dry Pipe

There are 4 steps to take in finding the slug calculation bbls for a Length of DRY Pipe.

Step 1 -

Find the hydrostatic pressure it takes to create a specific drop inside of the drill pipe.

We can find this by using the following formula:

HP psi = Mud Weight ppg x 0.052 x length of DRY pipe in feet

Step 2 -

Find the difference in pressure gradient between the slug weight and mud weight ppg.

We can find this via the following formula:

Pressure Gradient Change psi = (slug weight ppg – mud weight ppg) x 0.052

Step 3 -

Calculate length of the slug in the drill pipe.

We can find this via the following formula:

Slug Length ft = pressure in psi / change in pressure gradient psi-ft

Step 4 -

Calculate the slug volume bbls.

We can find this via the following formula:

slug volume bbls = slug length ft x drill pipe capacity bbl-ft

Now that we know how to find the slug calculation in bbls for a Length of DRY Pipe, let’s do an example give the following data.

- Desired length of dry pipe, 3 stands = 276 ft

- Mud weight = 12.5 ppg

- Drill Pipe Capacity 4.5 in = 0.01422 bbl/ft

- Slug weight = 14.5 ppg

So,

1. HP psi = 12.5 ppg x 0.052 x 276 feet = 179.4 psi

2. Pressure Gradient Change psi = (14.5 ppg – 12.5 ppg) x 0.052 = .104

3. Slug Length ft = 179.4 psi / .104 psi-ft = 1725 ft

4. slug volume bbls = 1725 ft x .01422 bbl-ft = 24.53 bbls