Page 179 - Practical Well Planning and Drilling Manual

Section 2 revised 11/00/bc 1/17/01 12:04 PM Page 155

Well Control [ ]
2.2.4

if a large-volume kick causes concern over the casing shoe strength
while killing.

Equipment considerations.

1. The entire BOP system must be rated to handle potential kicks.
Elastomer seals (in ram and bag preventers, valves, hoses, etc.)
have to work at the highest temperatures and pressures (for the
duration of the section) likely to be encountered. The system
should also be suitable for H S service.
2
2. The mud-gas separators should be able to handle the large volumes
of gas at surface. Large-diameter vent lines will be needed (10 inch-
es or more).
3. High-pressure flarelines should be connected to the back pressure
manifold, rated to at least 5000 psi flowing pressure. The valves to
the flowlines on the back pressure manifold (BPM) should be oper-
able from the remote control panel as should those to the separators.
4. A facility should be available to measure the temperatures of the
wellhead and also the BPM downstream of the chokes. This will
ensure that temperature ratings are not exceeded and will give
advanced warning of conditions for hydrate formation.
5. Methanol injection under wellhead pressures into the BPM must be
possible to avoid hydrate formation.

2.2.4. Well Control in High-Angle and Horizontal Wells

High-angle and horizontal wells involve extra considerations in
maintaining primary well control and in regaining it if a kick is taken.
The normal kick calculation principles do apply, however, the calcula-
tions are more complicated for maintaining a constant bottom hole
pressure during a balanced method kill. In some circumstances, it is
preferable to use a drillers method kill. Refer to Section 3.1.4, “Well
Killing in a High-Angle Well,” for the calculations for killing a kick in
a high-angle well.
Well planning considerations. With the well profile and casing
points decided, write the well plan to reduce the chances of taking a
kick. Normally in a horizontal well the pressures will be known and a

155