Drill String

Question 1

Equation for Total Weight?

Answer 1

Weight of drill pipe in mud + Weight of drill collar in mud = ((LdpWdp) + (LdcWdc))*BF

Question 2

Equation for drill pipe strength expressed in terms of yield strength?

Answer 2

Pa = Pt * 0.9
(Pa = maximum tensile load
Pt = drill pipe yield strength)

Question 3

Equation for Ldp

Answer 3

Ldp = (Pt * 0.9) / (SF * Wdp * BF) - (Wdc / Wdp)Ldc
OR
(Pt * 0.9 - MOP) / ( Wdp * BF) - (Wdc / Wdp)Ldc

Question 4

Equation governing elastic torsional behaviour in a cylinder

Answer 4

T/J = shear modulus/r = G*angle/L = Gw