Well-Centric’s range of specialist well clamps help to secure and support unstable wells, providing a cost-effective alternative to conductor replacement
While the integrity of all aspects of oil and gas assets is undoubtedly important, wells are necessarily one of the primary concerns for operators. As many offshore wells age, their integrity is also compromised as a result of harsh marine conditions and years of production. In cases where wells show signs of excessive movement, wellhead clamps are used to secure them.
Damage to well casing itself can cause movement of the wellhead, transferring loads to parts of the wellhead that are not designed to cope with them and causing scoring, fretting and rubbing damage. Remedying this requires the redistribution of those loads to parts of the well that have more strength, and can support and stabilise the well and any additional equipment.
Aberdeen-based well integrity and production technology specialist Well-Centric has developed a range of clamps designed to centralise, stabilise and support wellheads and prolong the life of ageing wells. Each wellhead clamp is designed using load calculations verified to prove the design is fit for purpose. The designs allow for normal expansion and contraction of the well over time as temperatures and production rates vary, whilst preventing excessive movement outside these accepted parameters.
In one recent case, Well-Centric was selected to centralise a well in the North Sea which had been experiencing excessive movement between the 30-inch (762-mm) conductor and the well casing, as a result of a damaged centraliser.
After inspecting the well with cameras, the operator discovered that this movement combined with the loose/damaged centraliser had been scoring into the conductor. An early consideration was to cut the casing, remove the broken centraliser and fit a replacement – at substantial cost. Instead, Well-Centric designed a clamp that centralised the wellhead and limited excessive movement and therefore any further scoring in the conductor.
The team was tasked with designing a purpose-built well centralisation clamp which limited movement to prevent further scoring and damage, and which was capable of withstanding 25 tonnes of lateral force. The clamp also needed to be easily fitted, removed and maintained, avoid interfering with existing wellhead equipment and incorporate removable wear pads to prevent metal-to-metal contact.
Well-Centric produced a design incorporating six load fins, each capable of withstanding a 25-tonne load, along with adjustable and removable wear pads. Each fin had a 4-tonne shackle point for lifting during installation and grease nipples to allow the bolts to be lubricated during maintenance periods.
During deployment, the clamp was assembled in two parts, which were torqued together onto the conductor to prevent any slackening of bolts during rough tidal movement. In this case, speed was of the essence. The clamp was designed, built and deployed within an eight-week period and installed by Well-Centric engineers offshore; installation was carried out in just one day.
One engineer remained on the platform post-installation to ensure the clamp continued to hold as designed and to observe any movement between the conductor and well casing. After three days, it was confirmed that no movement was taking place and that the installation had been a success.
The alternative repair option would have been to remove the conductor pipe surrounding the damaged centraliser and replace both the centraliser and conductor with new – a job worth in excess of GBP500,000 (US$660,000) when factoring in manufacturing, personnel to remove the existing damaged equipment and loss of production.
With 70% of global oil production extracted from mature fields, conductor integrity issues are becoming a more common occurrence. While there is still life left in these fields, it is often not commercially viable to carry out expensive replacement repair operations. The production value from the field must justify the repair and so cost-effective solutions such as those provided by Well-Centric enable production from these brownfield assets to be maintained and prevent early abandonment of wells.