Page 390 - Practical Well Planning and Drilling Manual

Section 3 revised 11/00/bc 1/17/01 12:00 PM Page 366

[ ] Practical Wellsite Operations
3.3.4

one is to approach the table with the slips set until the driller has
released the rotary brake and picked up the string slightly.
3. Whenever working the pipe in tension and torsion, no one should be
on the floor other than the driller on the brake. Only when setting or
pulling the slips or tongs will anyone be needed on the floor.
4. All entries to the drillfloor, except past the driller, should be barri-
ered off with breakable tape. Rope or other solid barriers are not to
be used because they will impede escape off the floor. Place notices
and barriers at the bottom of any stairs that directly access the drill-
floor (V-door, from mud pits, etc.). The deck crew must be informed
that access to the drillfloor is restricted.
5. If working with explosive primer cord, keep unnecessary personnel
clear and follow the instructions of the driller and logging engineer.

Procedure. Ideally the backoff is done in such a way that damage to
the connection is minimized and it is possible to run in with a fishing
assembly and make up to the backed off top of the fish.
Backing off can be done mechanically or with a downhole explosive
charge. Where a charge is not used, the backoff cannot be controlled
well enough to break at a specific connection. Even when a charge is
used, a different connection will sometimes backoff instead, or several
connections may become loosened.
First determine the stuck point depth, either by using stretch data
or by running a wireline tool to measure stretch in the string (such as
the Schlumberger Free Point Indicator Tool [FPIT]).
The logging engineer will determine how much explosive primer
cord to run, given the depth, mud weight in use, and connection size.
Run this in the string through a kelly cock with a cut-out protector to
cover the thread to the planned breakout connection; a slimhole casing
collar locator (CCL) is used to correlate depth. Meanwhile put the tong
line sensator on the breakout tong where the breakout and backup lines
attach to the tong. This allows torque to be monitored both while work-
ing the pipe up and down and also when putting in left-hand (LH)
torque with the breakout cathead. If the kelly or top drive is still on the
string, the backoff charge may be run through a removable plug on the
gooseneck top. Do not forget to protect the thread on this from cutting
out by fabricating a small protector to cover the thread.

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