Page 173 - Introduction to Petroleum Engineering

160 DRILLING

8.9 Suppose a diesel engine rotates a shaft at 1100 rev/min by consuming diesel at
a rate of 28 gal/hr to provide an output torque of 1560 ft·lbf. Assume the
density of diesel is 7.0 lbm/gal with a heating value of 18 000 BTU/lbm.
A. What is the output power P in hp?
sp
B. What is the input power P in hp?
in
C. What is the overall efficiency η of the engine?
sp
8.10 A. Given the following information, calculate the number of joints of pipe
needed to complete the drill string:

Pipe weight 654 lbf each
Pipe length 30 ft each
Length of drill string 6000 ft = 1828.8 m
Number of joints of pipe
Total pipe weight lbf
B. Calculate the total pipe weight for the number of joints of pipe in Part A.
Express your answer in lbf.
C. Calculate the polar moment of inertia of the drill string
4
4
J = (π /2 r ( ) outer − r ) for outer radius = 2.25 in. and inner radius = 1.75 in.
inner
4
Express your answer in m . Hint: first convert inches to m.
D. The rotary torque is 4000 ft∙lbf. What is the rotary torque in N∙m?
e. Calculate the shear stress τ = Tr outer J / . Express your answer in MPa.
F. Assume the elastic modulus E of drill string steel is 200 GPa and its
Poisson’s ratio ν is 0.3. Calculate the shear modulus of elasticity
+
G = /(22ν ). Express your answer in GPa.
E
G. Convert the length of drill string L to meters and use this result to calculate
the angle of twist ϕ in degrees, where φ = TL GJ).
/(
H. What is the angle of twist per joint of pipe? Use result from Part A.