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 Free Point Constant and apply it into free pipe formula to determine where the depth of stuck pipe is.

The steps of calculation are as follows:

**1 ) Determine the free point constant (FPC) by this following formula:**

**FPC = As x 2500**

where: As = pipe wall cross sectional area, sq in.

**As = (OD ^{2}-ID^{2}) x 0.7854**

OD and ID are inch unit

**2) Determine depth of stuck pipe by this following formula:**

**Depth of stuck pipe = (Pipe stretch in inch x free point constant (FPC)) ÷ Pull force in thousands of pounds**

Please see the example below to demonstrate you how to apply those 2 formulas above into real drilling operation.

Example#2: Determine the free point constant (FPC) and the depth the pipe is stuck using the following information:

3-1/2” tubing # 9.5 lb/ft

3-1/2” tubing ID = 2.992 inch

20 inch of stretch with 25 Klb of pulling force

**a) Determine free point constant (FPC):**

FPC = (3.5^{2} – 2.992^{2}) x 0.7854 x 2500

FPC = 6475.5

**b) Determine the depth of stuck pipe:**

Feet of free pipe (ft) = (20 inch x 6475.5) ÷ 25

** 25 is the kilo-force to pull to 20 inch **

Feet of free pipe (ft) = 5,180 ft

**Please find the Excel sheet used for calculating depth of stuck pipe.**

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