Drilling cost per foot is the total drilling cost per footage drilled. This value is used for evaluating drilling projects, bit performance, drilling performance, etc.
The formula for drilling cost per foot as shown below;
CT = (B + CR (t + T)) ÷ F
CT = drilling cost per foot
B = bit cost
t = drilling time
CR = Rig cost per hour. This number must include all fixed daily cost not just only drilling contractor rate.
T = round trip
F = footage drill
Example: Determine the drilling cost per foot (CT) using the following data:
Bit cost (B) = 27,000 $
Drilling time (t) = 50 hours
Rig cost (CR) = $3500/hour
Round trip time (T) = 12 hours
Footage per bit (F) = 5000 ft
CT = (27,000 + 3,500 (50 + 12)) ÷ 5000
CT = 48.8$ per foot
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.