Page 203 - Practical Well Planning and Drilling Manual

Section 2 revised 11/00/bc 1/17/01 12:04 PM Page 179

2.3.5
Directional Planning [ ]

WOB up somewhat. This will improve ROP and may also increase the
drop rate a little as it forces the drill collars to buckle outward due to
the bend in the hole between the bit and second stabilizer.
Reaming once or twice before each connection can also help in soft
to medium hardness formations.
If using a fixed cutter bit, choose one with a short-gauge length,
flatter face profile, and side cutters. With a roller cone bit, avoid pads
welded on to the shirttails. In abrasive formations with insert bits, use
diamond-enhanced heel and gauge cutters but again avoid shirttail
pads that effectively increase the gauge length.
Maximizing hydraulic impact force may help to erode formation at
the bit face that could help to drop angle.
There are only two occasions in general when a pendulum assem-
bly is justified; when you actually want to drop angle and when drilling
1
large diameter surface hole with large, heavy drill collars (17 /2 in hole
with 9 /2 in drill collars). Do not use a pendulum assembly if already
1
vertical and you intend to drill a vertical well. Any sideforce at the bit
(e.g., a hard streak) will cause the bit to kickoff, causing a potential
problem later on with a ledge, apart from the effect on directional per-
formance, which may cause you to miss the target.

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