Drilling through a loss zone leads to a high probability of poor cement quality and free pipe. If there is a corrosive aquifer, the possibility of external corrosion is increased drastically. It is critical to understand the integrity of the pipe across these areas. Regular logging is recommended to identify when corrosion will migrate from the outer to the inner pipes. This will enable a remedial program such as installing a scab liner to be instigated before a catastrophic failure.
Corrosion Logging Result
One example when corrosion logging was done in a 4 barrier well (strings) and metal loss on the outer casing was detected is shown below:
The well is vertical gas lift oil producer drilled in 1991. The well was completed with a 13 3/8” surface casing, a 9 5/8” intermediate casing and a 7” production liner. A 3.5” gas lift completion string was run.
In 2005 during a workover the 9 5/8” casing was pressure tested in stages. The test indicated that the casing had failured at an interval from surface-37.70 m. A 7” scab liner was run from surface to the top of the 7” production liner. A 3.5” gas lift completion string was run.
In 2020 a subsurface integrity test (SIT) was conducted and the C annulus LOT failed, whereas the B and the A annulus tests were successful.
In 2021 and 2022 the SIT was repeated with the same results.
In 2023 EMDs corrosion logging was run. The log data indicated the presence of an extended interval of severe metal loss in the shallow section of the well in the 13 3/8” casing. The maximum metal loss was almost 100%. In addition the temperature curve showed the existance of crossflow across the corroded interval.
The EMDs tool can accurately pinpoint areas of corrosion and metal loss. From the logging results future well designs should be reviewed to mitigate metal loss in the outer strings e.g. heavier grade pipe, alternative metallurgyto avoid leaks, improved cement placement such as staged cementing.
In addition to performing regular SIT’s it is recommended to increase the frequency of EMDs logging to establish corrosion trends, thus allowing the client to perform timely interventions to maintain well integrity.
All case studies
4th Barrier Metal Loss 1
Drilling through a loss zone leads to a high probability of poor cement quality and free pipe. If there is a corrosive aquifer, the possibility of external corrosion is increased drastically.
Combination of PLT and Acoustic Logging
A PLT is a common logging tool which provides flow profile inside the wellbore only. This type of tool cannot provide the formation flow profiles as well as crossflow above-between-below perforated intervals.
Temperature Monitoring in Steam Injectors
Integrity issues in steam injection wells can have unforeseen impact on adjacent production wells.
Identification of Pipe Accessories 1
Having an accurate knowledge of all casing accessories can be critical for operations such as perforating, window milling for sidetracking and casing milling for final abandonment.
How to accurately measure the injection distribution profile behind the pipe. Some injection wells have been designed to inject via the tubing and the A annulus simultaneously.
Looking for more information?
Get in touch with us and our representative will get back to youContact Us