DEFLECTION TOOLS
There are a number of tools and techniques which can be used to change the direction in which a bit will drill. These tools and techniques can be used to change the inclination or the azimuthal direction of the wellbore or both. All of these tools and techniques work on one of two basic principles. The first principle is to introduce a bit tilt angle into the axis of the BHA just above the bit and the second is to introduce a sideforce to the bit (See Figure 5). The introduction of a tilt angle or sideforce to the bit will result in the bit drilling off at an angle to the current trajectory.
The major tools currently used for this purpose are:
• Bent Sub and Positive Displacement Motor
• Non-Rotating Steerable Drilling Systems
• Rotary Steering System
• Directional Bottom Hole Assemblies (BHA)
• Whipstocks
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Direction in which bit will drill |
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Side Forcei |
Tilt Angle
Figure 5 Bit tilt angle and Sideforce