Retrieval of an Electrical Submersible Pump (ESP) requires similar precautions to those taken during installation and some additional points should also be considered when retrieving ESPs.
Analysis of the reasons for ESP failure may not be possible if additional damage is sustained by the equipment during retrieval from a well, or during subsequent storage and transport. This may result in a repetition of design errors, and may jeopardise warranty claims.
The same handling procedures and precautions taken with new equipment should be applied to used equipment. In many cases equipment retrieved from a well can be repaired and re-used with considerable cost savings in comparison to the use of new equipment. To minimise repair costs the same care is required when handling, lifting and packing used equipment as is required for new equipment.
Pulling out of the well
It is desirable to have a vendor engineer on site during the pulling of a failed completion. A full "pull" report should be filled out by the engineer as an aid in diagnosing reasons for failure. Cable should be inspected for armour damage (such as wear or explosive decompression) and damage noted on the pull report. The bands should be cut off with a cutting tool. The condition of the bands should be noted. If bands show signs of corrosion, a different metal should be used for future banding material. Rig personnel should note whether bands are missing as the tubing is pulled. If a large number of bands are found to be missing, it may be necessary to retrieve the bands from the well prior to installation of a new Electrical Submersible Pump. Cable protectors should be recovered, cleaned, and oiled.
All accessories should be examined and damage noted. Obvious pump/motor damage should be noted. This will include an estimate of potential bearing wear in rotary gas separators, a check on the ability of the Electrical Submersible Pump and motor to turn freely, recording of obvious overheating (such as discoloured motor housing), recording of condition of motor oil and seal protector oil, etc.
As a minimum the following checks should be made and the information recorded prior to and during a pulling operation:
- data gathering of Electrical Submersible Pump information prior to failure (including rates, pressures and ammeter charts);
- visual inspection of surface controller with a check on protective and monitoring devices and input voltage values;
- electrical check of cable prior to pulling and visual inspection during pulling;
- electrical check of cable after disconnection from motor;
- external damage check of Electrical Submersible Pump, seal and motor (physical damage and signs of overheating);
- pump intake check for plugging;
- pump and motor check for shaft rotation and side play;
- check on condition of motor oil (discolouring/water content);
- condition of seal section oil;
- check on resistive values of motor.