Reactive Flex Joint

Subsea wells are increasingly seeing higher dynamical loadings on the wellheads (WH) and upper parts of the well construction. This is due to two factors: a. Wells are drilled with larger and heavier mobile offshore drilling units (MODU). With their higher ratings for water depth capacity and pressure, these [deep water] rigs also have taller and heavier subsea blow-out preventer (BOP) stacks. The marine riser system connected to the BOP is tensioned from the rig, and dynamical forces are exerted on the WH. When the MODU moves laterally about a "center" in the prevailing sea states, and also due to hydrodynamic forces exerted on the riser system from waves and currents, the forces on the WH can become both substantial as well as cyclic in nature. b. For several reasons, the time to drill and complete subsea wells has increased over the years. Due to maintenance and efforts to increase oil recovery (IOR) activities, more time is spent doing well service work like workover and other remedial work. In total, the number of days with MODU and well control system connected to the well has increased. FMC Technologies together with Statoil seeks to significantly reduce the bending moments acting on the WH by introducing a technology - a Reactive Flex-Joint (RFJ)- as a part of the marine riser system. The mitigation of the bending moments will decrease the impact of fatigue on the WH with the following benefits: - Increase lifetime of WH systems thereby reducing cost of future oil production. - Increase operation weather and sea state windows for well operations while reducing bending moments and fatigue. A RFJ pilot has been designed and built by FMC Technologies for use on the rig Deepsea Bergen for operations on the Åsgard field. An extensive qualification program has been completed by Statoil and FMC Technologies, comprising both onshore and offshore tests and global/local analysis. The objective of the Qualification is to qualify the RFJ to an acceptable technology readiness level in both Statoil and FMC Technologies organizations. The qualification has been subjected to independent review by DNV GL and will be certified through a DNV GL ?Technology Certificate?. The subsea test has been performed through drilling one new well. 290 m dept. Using Odfjells rig Deepsea Bergen. Deepsea Bergen has a monitoring system on the BOP that can measure the bending moment just above the wellhead connector. By measuring the bending moment with and without the RFJ active we can calculate the efficiency of RFJ. Testing was conducted in the period 08.03 ? 08.04.2016 during drilling operations (no X-tree) on well G-2 H and in the period 14 - 15.04 during completion operations (with X-tree). The tests confirms that RFJ are reducing the average bending moment with more than 50%. This gives a lifetime extension of a factor 10 according to DNV GL?s SN curve. The objective of the project was to reduce the bending moment on the wellhead connector by 50%.

Subsea wells are increasingly seeing higher mechanical loadings on the wellheads (WH) and upper parts of the well construction. This is due to two factors: a. Wells are drilled with ever larger and heavier mobile offshore drilling units (MODU). With their higher ratings for water depth capacity and pressure, these [deepwater] rigs also have taller and heavier subsea blow-out preventer (BOP) stacks. The marine riser system connected to the BOP is tensioned from the rig, and forces are exerted on the WH. When the MODU moves laterally about a "centre" in the prevailing sea states, and also due to hydrodynamic forces exerted on the riser system from waves and currents, the forces on the WH can become both substantial as well as cyclic in nature. b. For several reasons, the time to drill and complete subsea wells has increased over the years. Due to maintenance and efforts to increase oil recovery (IOR) activities, more time is spent doing well service work like workover and other remedial work. In total, the number of days with MODU and well control system connected to the well has increased. FMC Technologies seeks to significantly reduce the bending moments acting on the WH by introducing a mechanism - a reactive flex joint - as a part of the workover system. The mitigation of the bending moments will decrease the impact of fatigue on the WH with the following benefits: - Increase lifetime of WH systems thereby reducing cost of future oil production. - Increase operation weather and sea state windows for well operations while reducing bending moments and fatigue.