Filling Wellhead Voids with Sealants
Among the most common Well integrity failures faced by Well operators are those related to annuli communication through Wellhead Seals. Through a combination of ageing equipment, harsh environments and corrosive fluids, these Seals lose integrity and fail. At KCI we have developed two products to combat this: Mac-Seal and MS-Sealant.
Unlike some other sealant options, both Mac-Seal and MS-Sealant are time-activated and deployed in a liquid state to avoid unnecessary stress or damage to the already compromised Wellhead.
These sealants are self-bonding, pressure-energised, flexible materials when they reach the appropriate area of the Wellhead and cure. This results in the creation of robust, static isolations to re-establish Well integrity.
Other basic methods for repairing Wellhead voids include pumping solid plastic filler into the void to re-establish integrity. However, this can create an unreliable, brittle seal that blocks the flow path without repairing the issue. This could lead to costly workovers to replace components.
Using innovative time-activated leak sealing technology, deploying a liquid sealant into Wellhead Voids and Pack-Offs offers a quick, safe, reliable, robust and cost-effective solution for rigless, onsite Wellhead Integrity repairs.
Having a large stock of Wells in mature fields means that equipment comes closer to failure more regularly, especially in extreme climate conditions experienced in the Middle East. Often, solutions proposed to restore and maintain Well integrity involve invasive workovers. However, KCI offer more cost-effective and quicker to the market.
Mac-Seal vs MS-Sealant
The two sealant options developed by KCI have numerous similarities in their application methodology and the way they are used, however, the situations in which they should be used are different.
Both are time activated; they are deployed in their liquid state into the Wellhead voids.
The sealants can be deployed under very low pressures to protect already fragile Wellhead components.
They are two-part products, changing from a liquid to a solid, flexible, robust, self-bonding material once cured.
The two Sealants can be supplied in various viscosities depending on the specific situation and the size of the leak path.
MS-Sealant has been formulated for use in hotter environments where it provides a longer working time.
Pressure vs Time-Activated Sealants
KCI’s sealant repairs are classed as ‘temporary’ however this term can mean different things to different operators. With regular testing, a sealant isolation can last to the end of the Well’s life.
The main reason the isolations are classed as temporary is that a permanent repair would involve replacing the seals or components with the Original Equipment Manufacturers’ parts, which are uneconomical in most cases.
The use of this temporary repair using time-activated sealants to fill wellhead voids is preferable as it allows for a fix to be made with less Well downtime until a more permanent solution can be implemented. This extends the safe operation of the Well until a repair or Well abandonment can be carried out.
Pressure-activated sealants can be used to fill Wellhead voids, with the option to undertake pressure testing within the Void area. However, these Pressure-activated sealants require high pressures to activate, meaning they are unsuitable for larger leak rates or fragile equipment.
These types of sealants leave the voids filled with thin fluids, where they can expand due to thermal effects, creating a scenario where an overpressure could displace the isolation and cause further damage to equipment and increase the leak.
Pressure-activated sealants do not create a solid isolation to stop leaks or protect the wider pressure-retaining envelope, instead, they create a small local scab, which can easily break, become washed out or can unintentionally be popped out under differential pressure. This restricts their use in situations where there is a larger leak with a requirement for differential pressure.
Time-activated sealants, on the other hand, can stop leaks by creating a solid, flexible seal that can be deployed up to 5k psi pressure, allowing for pre-energisation while the sealant is curing.
Products such as Mac-Seal and MS-Sealant are available in several viscosities depending on the leak rate and leak path, making them appropriate for use in various situations.
Utilising time-activated sealants allows for the permanent plugging of Control Lines, Chemical Injection Lines and Capillary strings with a robust seal where integrity has been lost. To isolate and seal larger leak paths, it is possible to use lower pressure time-activated sealant options, giving these more versatility as solutions. It is also possible to layer these sealants over each other to plug larger leaks as they bond together to create a single piece isolation.
High viscosity, time-activated sealants can be applied to gasket seal faces, sealing and filling any corroded areas or scores.
It is recommended not to carry out pressure testing against some of these isolations depending on the port location, as it is possible to disturb the sealant and create new leaks.
When testing a Time-activated sealant such as MS-Sealant or Mac-Seal, it is recommended to undertake Leak Off testing in the direction of flow. This allows for Well barriers to maintain integrity without the seals being pushed and flexed in the opposite direction which may lead to failures.
Filling Wellhead Voids
In instances where the Wellhead sections have Voids and Cavities which require regular testing, KCI undertakes extensive investigation and evaluation from multiple points to verify Well integrity. This allows for specific Voids and Cavities to be filled with sealant to create pre-energised isolation masses.
Some operators prefer to keep leaking Voids clear of sealants, allowing for easier monitoring and testing. However, dangerous hydrocarbon gases and liquids can gather and become trapped in these areas, causing dangerous build-ups of pressure. If the Void is full of cured time-activated sealant there is nowhere for the build-up to occur, leading to a safer operation.
MS-Sealant and Mac-Seal can be left to cure under pressure in some cases, creating a pre-energised isolation that remains stable in temperatures ranging from -54℃ to 204℃. This wide temperature range allows for successful applications in changing and varied conditions.
Since 2013, KCI has completed over 500 jobs utilising MS-Sealant for in-situ seal repairs. This has resulted in more than $60 million US in cost savings for deferments and workovers due to downtime. These jobs have been completed with a 99% success rate.
To see numerous Case Studies showing the versatility of Mac-Seal and MS-Sealant in the filling of Wellhead Voids and Wellhead Seal Isolations for clients across the globe, download information packs from KCI’s Wellhead Seal Isolations page
Contact KCI to request the most up to date SDS and Technical Specifications and find out if Mac-Seal and MS-Sealant are the right options for you.