Exercise
For a drilling assembly that is 12,000 ft in length, where the horizontal departure (HDY)t is 2000 ft, find the maximum hook load during tripping out of the hole (assume zero buoyancy) and the maximum torque while drillin.
Assume an average coefficient of friction equal to 0.25, an average effective drill string unit weight of 15 lb/ft, and an outside pipe diameter of 5 inches.
Solution
Maximum hook load (no buoyancy) = 
Assessment
1. Which of these statements is FALSE?
A .The capstan effect refers the normal force caused by the deformation of an axially loaded member about some obstacle.
B .Drilling rig specifications are one of the determining factors in establishing torque and drag limits.
C .When the angle of inclination from vertical is 45 degrees, the axial and normal components of the unit drill string weight are equal.
D .To transmit bit weight in a horizontal well, the drill string in the lateral section must be in compression.
E .In a horizontal well, the weight stack portion of the drill string is placed in the horizontal section. ✔
F .In a horizontal well, the drill string make-up dictates the maximum length of the bit run.
2. Which of these features are designed to make rolling cutter bits more suitable for horizontal and high-angle directional drilling?
A .High-strength seals and journal bearings
B .Hardened sidecutting elements and inserts
C .Extended jet nozzles
D .A and B ✔
E .A, B and C
3. During axial movement of the drill string, frictional loading manifests itself in the form of __________.
A .increased torque
B .decreased torque
C .a difference in hook load ✔
D .drill string buckling
4. As a borehole’s inclination angle increases, the frictional forces that oppose drill string movement _____.
A .increase ✔
B .decrease
C .are unaffected
D .A, B or C depending on hole diameter
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