Page 396 - Practical Well Planning and Drilling Manual

Section 3 revised 11/00/bc 1/17/01 12:00 PM Page 372

[ ] Practical Wellsite Operations
3.3.5

Sometimes part of the BHA can be deliberately backed off in the
drill collar section after getting stuck and packed off. This is a difficult
fishing job, but it is possible to successfully recover by washing over.
If a decision is made to wash over the string, it is best to washover
and recover in one run without stopping circulation. Otherwise, while
the washover string is being pulled and the fishing string run, solids
will again settle around the fish. Backoff at a convenient depth just
above the stuck point and then run the following fishing assembly:

Washover shoe and pipe, long enough to reach below the bot-
tom stabilizer or just above the bit sub to stab into the top fish
connection - circulating sub with the sleeve already open - drill
collar - safety joint - two drill collars - fishing jar - three drill col-
lars - accelerator - HWDP, etc.

Washover the fish, screw into the fish without interrupting circula-
tion, continue to circulate, and pull/jar free. By having the open circu-
lating sub inside the top of the washover pipe, circulation is maintained
all the time, even if the fish is plugged inside with solids (as is likely).
The washover shoe may have to mill over several stabilizers, which
may take more than one run to achieve.
Fishing BHAs. A fishing assembly will almost always include a jar
and an accelerator. The Bowen “Z” fishing jar is the most commonly
used jar with the matching accelerator. These will jar for many hours
without losing effectiveness and can be torqued up in both directions.
The Z jar jars up and only bumps down.
A fishing bumper sub can be run to allow bumping up or down, or
to apply a specific downhole weight by running the required number
of collars below and working with the bumper sub partially closed.
A drilling assembly will include a number of drill collars to give
weight on bit. Fishing assemblies normally do not need to run much
weight. This would be detrimental because it gives less overpull avail-
able for jarring and more weight below the jar would reduce the jarring
force on the stuck point.
A typical fishing assembly would consist of whichever latching
tool is to be run followed by fishing bumper sub - jar - two to four drill
collars - accelerator - X/Over - HWDP (optional) and DP. A safety joint
could be run above the latching tool as required. Sometimes a circu-

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