Page 395 - Practical Well Planning and Drilling Manual

Section 3 revised 11/00/bc 1/17/01 12:00 PM Page 371

Drilling Problems [ ]
3.3.5

When the grapple is far enough over the fish, stop rotating. Pick
up slowly while watching the weight indicator. If the fish is caught in
the grapple, the harder it is pulled the more it grips. Pull and jar as
required to free the fish. Pull out of the hole without rotating. Set and
pull the slips gently.
The die collar is another tool that catches on the fish OD. This
must be run with a safety joint since it cannot be released downhole. It
is not as strong as the equivalent overshot. Die collars and taper taps
are only run as a last resort, due to their limitations, and also because
they distort the top of fish, making it more difficult to subsequently
run other fishing tools.
Releasing an overshot from the fish. To come off the fish either
downhole or with the fish at surface, first set down some weight. This
releases some of the grip. Start to rotate to the right (with chain tongs
if at surface) and then pick up slowly. As stated previously, turning to
the right opens up the grapple.
Work up slowly until the fish comes out of the grapple. If the fish
can be set in the slips, carefully rotate to the left with the table while
backing up the overshot with the make-up tong and picking up very
slowly with the block. Tie the slips and use a safety clamp, but do not
do this if the fish is long or if it may backoff below the rotary table.
Close the blind rams below the fish first!
Fishing for casings and other tubular items (catching inside). If
for some reason an overshot cannot be used, a releasing spear may be
able to latch the inside diameter. It works very much like an overshot
in reverse and may be released downhole. The releasing spear is most
often used to catch casing, especially during abandoning if the casing
is cut to retrieve it and a slip and seal hanger were used.
The weak point of a releasing spear is the inner mandrel. In large
spears (say for 9 /8 in casing) this is not an issue, but if you are catch-
5
ing a small ID (say a drill collar) then the mandrel could be quite weak.
Another tool that can catch on an inside diameter is a taper tap.
This is stronger than a releasing spear of the same catch size but can-
not be released downhole, therefore, it must be run with a safety joint.
It looks like a long cone with threads on the outside and it is screwed
into the fish ID.
Fishing after backing off. Where the fish can be screwed back into,
a short fishing assembly can be run to try to screw back into the fish
and jar it free.

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