1 Job Planning
1.1 BHA Design
1.1.1 Stabilization
All PowerDrive BHA’s should have at least 2 stabilizers. The first stabilizer should be located on
the PD control collar or directly behind it. The 2
nd
should be 30-40 feet behind the first. Proper stabilizer
placement ensures optimal steering response and minimizes shock & vibration damage. Depending
on the BHA design, a 3
rd
stabilizer may be added another 30-40 feet behind the 2
nd
stabilizer. This
may aid in shock & vibration mitigation on the MWD but will have minimal effect on steering.
The first stabilizer should be 1/8” Under-gauge from the hole-size. The additional stabilizers may
be 1/8” or ¼” Under-gauge depending on the application.
Stabilizers should have spiral wrap, short gauge, and long tapers. A good rule of thumb is to aim
for a gauge length that is 50% of the hole-size and 60 degree taper. This design optimizes steerability
while preventing stabilizer jamming.
Roller Reamers may be used in place of stabilizers to reduce torque and stick-slip. Do not use
eccentric reamers or hole-openers in place of stabilizers.
1.1.2 Motor Selection
Bearing sections must be fixed-straight, not adjustable dialed to zero. Adjustable motors, even
when dialed to zero bend, have an offset that can initiate vibration.
Consider the PowerDrive RPM specification (220 for X6, 350 for Orbit) when choosing rev/gallon
of the power section. Exceeding the RPM specification will lead to reduced dogleg and tool damage.
1.1.3 Bit Selection
Extremely aggressive bits can cause stick-slip and whirl. These dynamics may lead to tool
damage, reduced dogleg, and lower ROP.
Tapering or under-cutting the back end of the gauge pad is recommended to maximize dogleg
and prevent excessive torque or stick-slip. This also allows for longer gauge lengths in
tangent/horizontal sections to improve stability.
“Active Gauge” bits should be avoided as the negative effects outweigh any benefits.
Depth of cut management features can aid in minimizing stick-slip but avoid placing them on the
shoulder of the bit as this may reduce dogleg significantly.
1.1.4 Additional Considerations
Flex Ponies and Collars should generally be avoided, especially in tangents or horizontals, as they
increase the odds of shock and vibration damage. A short Flex Pony directly on top of the PD tool will
increase the maximum dogleg by 1-2 degrees but should only be used if truly necessary.
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