After effort has been put into freeing the pipe the decision has to be made whether to back off or continue. There are two options to consider:
1. Back off above the free point and run in with a fishing assembly.
2. Back off above the free point, plugback and side-track
The decision to back off and run in with a fishing string is based on the experience of the personnel involved and the local situation. The option of plugging back and side-tracking should be taken on economic grounds, unless safety or legislative reasons would override a financially based decision.
Economic Assesment
An economic assessment shall be made prior to suspending fishing operations, during which, consideration should be given to the:
- value of the string left in the hole
- cost of backing-off, free point indicator and back off shot.
- cost of setting a kick off plug.
- cost of side-tracking and re-drilling to the original depth.
The total of these elements gives an estimate of the cost of side-tracking. This can be used in the following equation to determine the length of time for which it is cost effective to fish:
Economic fishing time = (Cost of sidetrack) x (Probability of fishing success)
(Daily cost while fishing)
The probability of a successful fishing job shall be based on local experience as far as is possible.