North Sea, UK

Tunisia

Nigeria

Denmark

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www.tendeka.com

BackgroundClient had a damaged SCSSSV, existing isolation system was damaged and could not stop the leak through the valve. A more robust sealing solution was required to ensure long-term production of the well. The challenge was to design a seal system strong enough to hold 5000psi differential pressure in a damaged seal bore with possible corrosion. The system also had to be flexible to be retrieved from the safety valve when required.

Project ResultsWithin 24 hours, the SwellStack was installed, activated and was holding the required pressure of 350 bar / 5000psi. By installing the SwellStack system, it extended the life of the safety valve and avoided the alternative of an expensive workover that would have involved pulling the completion to replace the entire system. Well integrity was regained and was placed back on production without the requirement for a workover.

Damaged Chevron Stack Replacement SwellStack system

SwellStackTM Sealing System

The Challenge

Tendeka’s Solution

Downhole safety valves can become corroded or damaged due to wireline activity. Standard chevron stacks commonly provided with safety valves are unable to effectively seal in this damage. This results in a leak path for hydrocarbons to migrate up the control line. Prior to Tendeka’s development of the SwellStack, a patented technology, the only option of a leaking safety valve was to perform a straddle or workover, and replace the damaged valve. This proved to be costly and time consuming.

In 2013, Tendeka developed and released SwellStack, a swellable sealing solution which can be installed in place of an existing chevron stack and seal in damage up to 0.060” within the bore of a safety valve. The SwellStack solution has since been utilised with multiple operators globally to regain well integrity via the safety valve. Comprising of a swellable seal element, and multiple chevron seals, the swellable element seals damage in the seal bore and activates the chevron seals, effectively providing a seal.

Example of Wireline Damage

Example of SwellStack Configuration

1. Swellable Element - Oil or Water Swell2. Inner V-Seal3. Centre V-Seal4. Stainless Steel End Ring

Due to valve size, further chevron seals may be added.

SwellStack extends life of surface control sub-surface safety valve (SCSSSV)

SwellStack regains well integrity without requirement for workover

BackgroundThe challenge was to design a seal system strong enough to hold 5000psi differential pressure to deal with an estimated 0.060” deep wireline cut in the seal bores and possible corrosion. The system also had to be flexible to be retrieved from the safety valve when required.

Project ResultsThe resulting SwellStack (right) clearly shows deformation in the seal where the compound had adapted to the damaged seal bore profile. Well integrity was regained and put back on production. The well was flowed briefly to increase the surrounding temperature at setting depth, increasing swell performance and reducing time before the valve held pressure. By installing the SwellStack system, it extended the life of the safety valve and avoided the alternative of an expensive workover that would have involved pulling the completion to replace the entire system.

SwellStack showing deformation

Extending the life of damaged safety valves

Gabon

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20Tendeka has successfully installed 163 SwellStack Sealing Systems globally.

Features & Benefits

– Cost-effective solution to extend the life of the existing DHSV

– Provides maximum reliability for the most severelydamaged and corroded sealbores, maintaining well integrity

– Removes requirement to workover– Supplied ready to run for installing on valve– Less than 3000lbs to retrieve seal from a DHSV

– Can be designed to seal in oil and water-based control line fluid

Well Data

North Sea, UKLocation:

Gas WellWell Type:

June 2016Installation Date:

Safety Valve: 5.963” SCSSSV

Well Data

North Sea, UKLocation:

Oil ProducerWell Type:

May 2014Installation Date:

Safety Valve: Dual bore 4.625”/4.562” SCSSSV