# 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 feet of drill pipe pulled to lose certain amount of hydrostatic pressure in well bore.

The calculations below have 2 cases of pulling out of hole, pull dry and pull wet. They are different in calculation because amount of drilling fluid out of hole is different. Please follow and understand each case of calculation.

#1: How many feet of pipe pulled DRY to lose certain amount of hydrostatic pressure

Feet = (hydrostatic pressure loss in psi x (casing cap in bbl/ft – pipe displacement in bbl/ft)) ÷ (mud weight in ppg x 0.052 x pipe displacement in bbl/ft)

Example: Determine the FEET of dry drill pipe that must be pulled to lose the overbalance using the following data:

Hydrostatic pressure loss = 200 psi
Casing capacity = 0.0873 bbl/ft
Pipe displacement = 0.01876 bbl/ft
Mud weight = 12.0 ppg
Ft = 200 psi x (0.0873 – 0.01876) ÷ (12.0 ppg x 0.052 x 0.01876)
Ft = 1171 ft
You need to pull 1171 ft of dry pipe to lose 200 psi hydrostatic pressure.

#2: How many feet of pipe pulled WET to lose certain amount of hydrostatic pressure

Feet = hydrostatic pressure loss in psi x (casing capacity in bbl/ft – drill pipe capacity in bbl/ft – drill pipe displacement in bbl/ft) ÷ {mud wt in ppg x 0.052 x (pipe displacement in bbl/ft + (% of volume in drill pipe out of hole ÷ 100) x pipe capacity in bbl/ft)}

Example: Determine the feet of WET pipe that must be pulled to lose the overbalance using the following data:

% of volume in drill pipe out of hole = 100
Hydrostatic pressure loss = 200 psi
Casing capacity = 0.0873 bbl/ft
Drill pipe capacity = 0.01876 bbl/ft
Drill pipe displacement = 0.0055 bbl/ft
Mud weight = 12.0 ppg

Feet = 200 psi x (0.0873 – 0.01876 – 0.0055 bbl/ft) ÷ {12.0 ppg x 0.052 x (0.0055 + (100÷100) x 0.01876 bbl/ft)}
Feet = 832.9 ft
You need to pull 833 ft of wet pipe to lose 200 psi hydrostatic pressure.

Please find how many feet of drill pipe pulled to lose certain amount of hydrostatic pressure in well bore.

Ref books: Lapeyrouse, N.J., 2002. Formulas and calculations for drilling, production and workover, Boston: Gulf Professional publishing.

Bourgoyne, A.J.T., Chenevert , M.E. & Millheim, K.K., 1986. SPE Textbook Series, Volume 2: Applied Drilling Engineering, Society of Petroleum Engineers.

Mitchell, R.F., Miska, S. & Aadny, B.S., 2011. Fundamentals of drilling engineering, Richardson, TX: Society of Petroleum Engineers.

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### 4 Responses to Drill pipe pulled to lose hydrostatic pressure

1. kev says:

what is pull dry and pull wet?

• Pull dry is when you pull out of hole, there is no mud coming out after breaking the connection.
Pull wet is opposite of pull dry, after breaking the connection, you will see the mud coming out.

2. i am requesting for information on formulars, calculations on density, achimedes principles, bernoulli’s theorem specific weight specific volume pressure in fluid and other related materials

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