Page 349 - Practical Well Planning and Drilling Manual

Section 3 revised 11/00/bc 1/17/01 12:00 PM Page 325

Well Control [ ]
3.1.5

Full opening valves or bursting disks should be used. Modifications to
the rig may be needed to ensure straight running lines.
Generally, two lines out of the diverter spool should be available so
that the downwind line can be selected if the well kicks. One may be
used in cases where there is a reliable prevailing wind, or on DP float-
ing rigs that can “weathervane” with the wind. Lines also need to be as
short as possible—just long enough to clear the rig structure (offshore)
or keep away from obstructions (land).

Checklist for selecting a diverter system.

1. The equipment shall be selected to withstand the maximum antici-
pated surface pressures.
2. All connections must be welded or welded flanges must be used.
Lines must be straight, properly anchored, and sloped down to
help avoid cuttings settling.
3. Installation requirements for wellheads and BOPs also apply.
4. A diverter system may be a BOP stack with diverter spool, lines,
valves, and control system—or a specific diverter setup. Closing
speed is very important. Either way, the diverter and mud return
lines should be separate to avoid gas entering the rig mud system.
5. Diverter valves must be full opening with a pneumatic or hydraulic
actuator. (Note: bursting disks have also been successfully used.)
Valve bore shall be the same as the lines.
6. A kill line with NRV must be incorporated for pressure testing and
to allow water to be pumped into the diverter.
7. The control system should preferably be self-contained or it may be
an integral part of the BOP accumulator and controls. It shall be
located in a safe area away from the drillfloor and have control
functions clearly identified.
8. If a surface diverter and subsea BOP are used, two separate control
systems are required. The diverter should be operable with the
minimum of functions, preferably a one-button or one-lever action
required to divert.
9. A 1 1 /2 in hydraulic operating line should be used for diverters with a
1 1 /2 in NPT closing chamber port size. The opening line may be 1 in.
10. All spare lines not in use must be plugged off.
11. The control system must be able to close the diverter or annular

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