BOP Tethering helps overcome issues with wellhead and conductor loading, and is particularly beneficial when dealing with older wells. Old wells often have 30” conductors, which do not always provide sufficient strength and stability for intervention with modern heavy BOP stacks.
This process involves tethering the BOP to reduce structural loading and results in improved fatigue life and operating limits.
With a lot of interest in BOP Tethering, AS Mosley has put together a case study, based on analysis we did for the abandonment of two weak wellheads. The analysis showed that tethering the BOP stack significantly improved the operability and fatigue life of the weak wellhead and conductor system. Peak wellhead loading was seen to reduce by a factor of 5 and the fatigue life improved by a factor of 200 for the fully tethered system.
The improvements achieved were sufficient to enable the abandonment operations to take place. Based on the support of AS Mosley, the two subsea wells were successfully abandoned in the summer of 2016 with no incidents.
Image credits: Trendsetter Vulcan Offshore