PNGE 216 – DRILLING ENGINEERING I
2021/2022 SPRING
Homework #5
1. (70 pts) A drillstring is composed of 9,000 ft of 5-in. 19.5-lbm/ft drillpipe and 1,000 ft of
drill collars having a 3.0-in. ID. Compute these items:
a) (5 pts) Capacity of the drillpipe in barrels.
b) (5 pts) Capacity of the drill collars in barrels.
c) (10 pts) Number of pump cycles required to pump surface mud to the bit. The pump is a
duplex double-acting pump with 6-in. liners, 2.5-in. rods, 16-in strokes, and operates at a
volumetric efficiency of 85%.
d) (10 pts) Displacement of the drillpipe in bbl/ft.
e) (10 pts) Displacement of the drill collars in bbl/ft.
f) (10 pts) Loss in fluid level in the well if 10 stands (Thribbles) of drillpipe are pulled
without filling the hole. The ID of the casing in the hole is 10.05 in.
g) (10 pts) Loss in fluid level in the well if one stand of drill collars is pulled without
filling the hole.
h) (5 pts) Change in fluid level in the pit if the pit is 8 ft wide and 20 ft long, assuming that
the hole is filled after pulling 10 stands of drillpipe.
i) (5 pts) Change in fluid level in a 3- x 3-ft trip tank assuming that the hole is filled from
the trip tank after pulling 10 stands of drillpipe.
2. (30 pts) Pipe being recovered from an interval of borehole has a value of $30/ft. On the
average, 20 hours of rig time must be expended to recover 200 ft of pipe. The cost per foot
to sidetrack the well and redrill the junked interval of borehole would be about $150/ft. Do
the fishing operations appear profitable if the average operating cost is $500/hr and the cost
of abandoning the junked hole would be approximately $5/ft?