STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

826 Drilling and Well Completions
WEAR PAD
BOTTOM HOLE
RWP" STABILIZER
L4
A
Figure 4-1 81. Replaceable-blades stabilizers. (Courtesy Smith International, Inc.)
ahead. Reamers can be used as near-bit stabilizers in the bottomhole assembly
or higher up in the string. There are basically three types of reamer body:
Three-point bottom hole reamer. This type of reamer is usually run between
the drill collars and the bit to ensure less reaming back to bottom with a
new bit.
Three-point string reamer. The reamer is run in the drill collar string. This
reamer provides stabilization of the drill collars to drill a straighter hole
in crooked hole country. When run in the string, the reamer is effective
in reaming out dog-legs, keyseats and ledges in the hole.
Six-point bottom hole reamer. This type of reamer is run between the drill
collars and the bit when more stabilization or greater reaming capacity is
required. Drilling in crooked hole areas with a six-point reamer has proven
to be very successful in preventing sharp changes in hole angles.
Application of Stabilizers. Figure 4-184 [ 161 illustrates three applications
of stabilizers, pendulum, fulcrum, and lock-in (stiffl hook-up.
The stiff hookup consists of three or more stabilizers placed in the bottom
50 to 60 ft of drill collar string. In mild crooked hole conditions, the stiff
hookup will hold the deviation to a minimum. In most cases, deviation will be
held below the maximum acceptable angle. In severe conditions, this hookup
will slow the rate of angle buildup, allowing more weight to be run for a longer
time. This method prevents sudden increases or decreases of deviation, making
dog-legs less severe and decreasing the probability of subsequent keyseats and
other undesirable hole conditions. The stiff hookup is beneficial only until the
maximum acceptable angle is reached. The pendulum principle should then
be used.