The following provides information based on past experience of the retrievability of packers, which provides general trends and guidelines for the execution of such activities. However, every well is different and as such hard and fast rules are not possible to giive. (KW: packer, retrievability, completion, production, well engineering, construction)
·The four biggest influences on packer retrievability are:
- the type of packer, hole angle, and packer depth;
- length of time the packer has been in the hole;
- the type of packer fluid (Mud or clear fluid);
- whether the well has had sand problems (i.e. trace of sand/sand/excessive sand).
·Of 20 dual packers retrieved 10 of these dual packers had to be milled and burned over.
·Of 45 single retrievable packers recovered, 14 had to be milled and burned over.
·Of 18 drillable (permanent) packers retrieved, milling and finishing time averaged 25 days per packer.
·The burning shoes that were the most effective were the "thin" shoes that shaved the packer without damaging the inner mandrel.
·According to these statistics, for packer retrievability a minimum of ± 4 days is required to recover dual packers and there is a 50% chance of having to mill or burn over a dual packer. To mill a dual packer 8 days should be allotted for fishing. A minimum of 3 days is required to recover single retrievable packers and there is a 69% chance of pulling the packer and not having to burn over it. (These fishing time estimates include time for fishing on the packer only and do not include time to remove production tubing before fishing on packer or contingencies. A good rule of thumb would be to give 2 days for recovering tubing on a single and 4 days to recover tubing on a dual. But again this depends on different parameters on each well and these numbers are subject to change).
These are only guidelines, and the Operations Engineer should use his or her judgement and expertise for each particular well.
·Experience indicates that certain types of packers from a specific vendor require less time to retrieve than other packers from a different vendor. Therefore, if there is a strong chance of a recompletion or workover in the future that requires retrieving a packer, then every effort should be made to run the packer that is easiest to remove (providing everything else is equal).
·When fishing a packer, attempt to pull the packer free. In most cases this is not successful and requires the tubing to be cut below and above the packer, removal of the production tubing, and jarring the packer free. If milling is required a thin wall burning shoe should be used. An average of 6 shoes is usually required.