Wellhead Fatigue Mitigation System
Two emerging technical challenges facing the drilling industry today are well fatigue and wellhead strength.
BOPs are increasing in size and weight, and drilling times are getting longer, causing wellhead fatigue issues to emerge as an industry challenge. New well designs must ensure that a high value well is engineered sufficiently to tolerate excessive fatigue caused by the newer and larger BOPs in use today. Legacy wells were mainly drilled with smaller BOPs and with a conductor design that was less robust. When attempting to interface with newer generation BOPs this exacerbates an already tenuous condition. In both cases, there are times when a wellhead fatigue mitigation device can provide substantial risk reduction.
The tethered BOP Wellhead Fatigue Mitigation System alleviates these effects by arresting the motion of the BOP stack above the wellhead, thereby substantially reducing wellhead cyclic stresses and enhancing fatigue life. Depending on the specific riser and wellhead configuration, the increased fatigue life is often seen to indicate, through analysis, an improvement of 25 to 1000 times the original unmitigated wellhead fatigue. No mitigations to the wellhead or casing string need to be performed. All modifications are performed to the BOP outer frame on deck.
An added benefit to the Wellhead Fatigue Mitigation System is the increased limits to the wellhead watch circle this system permits. Bending of the wellhead from lateral offset of the MODU due to drive off/drift off loads are reduced by factors of 3 to 4, enabling safer operations and decreasing position criticality. In shallow water, where watch circles can be very restrictive and approaching the Dynamic Positioning station keeping limits, this allows for a larger watch circle and decreased reliance on the DP’s station keeping performance.
Trendsetter’s Wellhead Fatigue Mitigation System is also available for rent.