Fishing with OvershotsThe following

Fishing with Overshots
The following guidelines should be considered when fishing with overshots:
 A pack-off should be installed if circulation through the fish is required before POOH.
 If the hole size is larger than the overshot OD, an oversized guide should be considered.
 If the pipe is lying in a recess or against the side of the hole, consider a hook wall guide or bent joint.
 If the fish cannot be engaged, consider an extension sub and a milling guide. A milling guide shall always be run with a basket grapple.
 To catch an upset or box section of a tool joint, a basket grapple with long catch stop shall be considered to be able to disengage the fish for unexpected reasons.
 To catch a coupling with a ruptured piece of pipe engaged in its upper end, a basket grapple with short catch stop, which has a double set of wicker of two different IDs shall be considered.
 The penetration of the fish into the overshot shall be limited in order to facilitate releasing it from the fish.
 An overshot can be used to back off as left hand torque tightens the grapple bite on the fish so right hand rotation can release the grapple.
 Unless an upward strain is maintained, the fishing string shall never be rotated to the right while an overshot is engaged on the fish, other than when attempting to come off the fish.
 Before the start of releasing operations slack off until slight compression at overshot. Release with right hand torque.
 When lowering the overshot over the fish, once a pressure increase is noted, circulation shall be stopped in order to prevent damaging the seal/packer. Bleed off any pressure trapped prior to engaging the fish.
 When the fish has been freed, the well shall be flow checked and circulated bottoms up as required, if circulation is possible through the fish.
 Make up circulating sub on fishing assembly.
 Start to rotate using chain tongs for rotating slowly.
 After fish is engaged, do not turn to the right as this will generally release overshot.
 Top of fish usually needs washing - but beware of washing away pack-off.