You can determine how much slug weight required in order to achieve desired length of dry pipe with certain slug volume that you will use.

Please follow these steps of calculation below;

**Step 1 Determine Length of slug in drill pipe in ft:**

Length of slug in drill pipe in ft = slug volume in bbl ÷ drill pipe capacity in bbl/ft

**Step 2 Determine hydrostatic pressure required to give desired dry pipe drill pipe:**

Hydrostatic Pressure in psi = mud weight in ppg x 0.052 x desired length of dry pipe

**Step 3 Determine slug weight needed in ppg:**

Slug weight in ppg = (Hydrostatic Prssure (from step 2) ÷ 0.052 ÷ Length of slug in ft (step1)) + mud weight, ppg, in hole

**Example: Determine slug weight required for the following data:**

Desired length of dry pipe = 200 ft

Mud weight in hole = 12.0 ppg

Drill pipe capacity = 0.016 bbl/ft

Volume of slug = 20 bbl

**Step 1 – Determine Length of slug inside drill pipe in ft:**

Slug length = 20 bbl ÷ 0.016

Slug length = 1250 ft

**Step 2 – Determine hydrostatic pressure required to give desired dry pipe drill pipe**

Hydrostatic Pressure in psi = 12.0 x 0.052 x 200

Hydrostatic Pressure in psi = 124.8 psi

**Step 3 – Determine slug weight needed in ppg:**

Slug weight in ppg = (124.8 ÷ 0.052 ÷ 1250) + 12.0

**Slug weight in ppg = 13.92 ppg**

**Ref book: ** **Formulas and Calculations for Drilling, Production and Workover, Second Edition**

Thank you very much for these useful formulas and ideas