Well intervention aimed at maintaining production rates is a critical aspect of managing mature oil and gas fields. Over time, the productivity of wells can decline due to a variety of subsurface conditions. Intervention techniques are employed to either slow down this decline or to boost production rates back to more desirable levels.
Wireline and slickline intervention in aging wells present unique challenges due to the deteriorated condition of the well structures and the increased risk of intervention complications.
Common wellbore issues include:
Structural Integrity of the Wellbore: Aging wells may have compromised structural integrity, including weakened casing, tubular deformation, or corrosion. These conditions can complicate the movement of wireline tools down the wellbore and increase the risk of tools becoming stuck.
Debris and Scale Buildup: Over time, scale, sand, and other debris can accumulate within the wellbore. This buildup can obstruct the path of wireline tools, making it difficult to perform interventions effectively, also increasing the risk of equipment becoming stuck downhole.
Deep and Tortuous Wells: Well depth, deviation, and the well tortuosity also all increase the risk of a tool becoming stuck in the well.
In wireline operations well tension profiling determines the value of which mechanical weak point should be installed in the cable head, to allow for cable retrieval in the event of a tool becoming stuck, while remaining within the safe working load of the cable.
There were however some issues with the use of “Spider” weak points, that are still used by some vendors today. The building of these weak points is technique sensitive and values can vary between those who build them. To remove these variations some vendors have replaced the spider weak point with a re-engineered solution that has a more reliable and consistent breaking value.
Note: Engineered weak points can be flexible or rigid and have specific applications depending on operational requirements.
Figure 1 Spider Weak Point
If a tool becomes stuck the removal of the cable, from the cable head, requires that sufficient tension is transmitted form surface to break the mechanical weak point. With wells becoming more deviated and deeper, this becomes more challenging with other methods being used to remove the cable. This situation led to the introduction of electronic release devices, installed in the cable head, or a separate tool, and these are in common service for operations. These tools are successful when the integrity of the electrical wireline is intact, that would allow an on-demand activation. All too often, when a tool becomes stuck, the cable is cycled at high tensions which often leads to loss of its electrical integrity and consequently the ability to command the electrical release from surface is lost.
Nowadays there is a choice of electrical and ballistic release devices available to mitigate the issues that can be face while performing well interventions.
Wireline
Wireline electrical release devices, commonly referred to as electric release subs or electro-mechanical disconnects, are critical components used in wireline operations, particularly during complex and higher risk interventions in oil and gas wells. These devices provide a controlled method to detach the wireline tool string from the cable in case of an emergency or if the tool becomes stuck in the wellbore, in addition to this many have safety features to prevent accidental release at surface and if communication to surface is lost, activate on a preset timer and battery. As these devices are addressable it is common to have more than one device in a tool string. This applies to tractor conveyed tools and associated remedial services.
Below are some links to some examples of available electronic release devices.
Welltec® Release Device
Inline Release Device – Wireline Conveyance | SLB
Addressable downhole release ADR cased-hole tool suite | Baker Hughes
Release Sub System (altusintervention.com)
Note: During an operation the release timer has to be managed and reset on a regular basis. Communication from surface to the device is needed to reset the tool, otherwise the timer will countdown to release. Some devices also require a minimum overpull to fully release.
Slickline
With the introduction of real-time slickline, on demand/timed release subs are also available.
DCR Digital Controlled Release Tool | SLB
Note: During an operation this release timer must be managed and reset on a regular basis.
Perforation
Ballistic release devices are available as an option. These offer the ability to drop off the perforation gun string in the event of an issue. These use commercially available firing systems and require communication between surface and the perforating tool string to release. These devices are activated using a Radio Frequency safe detonator.
Hunting | Hunting Release Tool – Electronic (huntingplc.com)
SPITFIRE™ Release tool (impactselector.com)
Technical Advisory
Use of Spider Weak Points
Mechanical weak points, such as the traditional “Spider” weak point, have been commonly used in wireline operations to ensure the cable can be retrieved if the tool string gets stuck. However, they have their limitations and when this is the only release method to be used in the tool deployment. This is due to variability and inconsistency that can lead to unreliable performance. An engineered weak point would always be preferred over a spider weak point.
Use of Electronic Release Devices
Due to the limitations of mechanical weak points, particularly in complex well scenarios, the industry has seen a shift towards electronic release devices:
Functionality: These devices allow for controlled detachment of the tool string from the cable via an electric signal from surface. They are particularly useful where mechanical weak points might be unsuitable due to the complexities of well architecture or operational demands.
Features: Many electronic devices include safety mechanisms to prevent accidental release at the surface and can activate on a preset timer if communication is lost.
Multiple Devices in Tool Strings: It’s common to include multiple release devices in tool strings, especially in tractor-conveyed operations, to ensure redundancy.
Management: These devices typically require regular communication from the surface to reset timers. If communication is lost, the device will activate based on its countdown and battery power.
Conclusion
To ensure that any well intervention operation is successful requires proper planning and the ability to recover from issues that may occur during the deployment of the downhole tools. In any scenario, where tools become stuck in the well, the remedial work is made easier with the complete removal of the logging cable.
Electronic release devices not only ensure that this can occur but leaves a clean fishing profile for the recovery of the tool left downhole. Having more than one of these devices, or combination, adds redundancy and improves reliability.
While ballistic release devices may have a specific application it may be useful to have the ability to release perforating gun system in the event of an issue.
If you have upcoming operations and are unsure of what release system the best fit for your well, get in touch
