Drill Strings for High-Angle Drilling
In high-angle drilling (Horizontal and extended-reach wells), getting the required weight to bottom is a primary requirement just as it is with vertical drilling operations, and torque, drag and buckling are critical design parameters.
The approach to drill string design for high-angle wells is fundamentally different from that of vertical wells. The weight on bit (WOB) in high-angle drilling does not come from the weight of drill collars placed between bit and drill pipe as the case for vertical drilling. Instead, an “inverted” configuration is used consisting of, from top to bottom:
- A vertical section, made up of conventional drill pipe run in tension
- A weight stack section, consisting of drill collars or heavy wall drill pipe
- A build section, consisting of compressive service drill pipe (this is the section where maximum bending stress occurs)
- A horizontal load section, consisting of large-diameter or compressive service drill pipe —this section must transmit axial and torsional loads, and it is here that torque and drag are of primary concern and must be kept to a minimum.
- A bottomhole assembly consisting of a bit, downhole motor, subs, non-magnetic drill collars, MWD/LWD tools and rotary steerable systems.
Assessment Bottomhole Assembly Tools
1. Which of these functions is NOT performed by stabilizers?
A .Ensure that weight of drill collars is concentrated on the bit.
B .Provide a gradual change in stiffness between the drill collars and the drill pipe.
C .Reduce torque and bending stresses in the drill string.
D .Build, drop or maintain hole angle.
2. Welded blade stabilizers are particularly effective for use in:
A .Hard formations
B .High-angle drilling
C .Packed bottomhole assemblies
D .Remote drilling locations
E .Soft formations
3. Which of these statements about drilling jars is FALSE?
A .Jars are usually only run as part of a fishing assembly.
B .In general, the smaller the number of drill collars run above a jar, the higher the impact force.
C .In general, the larger the number of drill collars run above a jar, the higher the impulse force.
D .Whenever possible, drilling jars should be run in tension.
4. Three-point string rotary reamers are particularly effective for:
A .Reaming out dog-legs, key seats and ledges
B .Maintaining in-gauge wellbores in hard, abrasive formations.
C .A and B
5. Hole openers can be designed to _____.
A .enlarge previously drilled hole intervals
B .simultaneously enlarge hole intervals as they are being drilled with a smaller diameter bit.
C .enlarge hole sections below casing
D .A, B and C
E .A and B only
6. Where is a float sub usually located in the bottomhole assembly?
A .Near the top of the drill collars.
B .Just above the bit.
C .Above the MWD assembly.
7. In high-angle drilling, compressive service drill pipe is used in ___.
A .the vertical section of the drill string.
B .the build section of the drill string.
C .the horizontal load section of the drill string.
D .A, B and C
E .B and C only
F .A and C only
Recommended for You
Drill String and Bit Considerations in Deviated Wells
Underbalanced Drilling in Directional Wells
