Subsea 7 first adopted the Hyperflow Hybrid Riser Tower on the Total Girassol Deepwater Development Project in Angola during 1999, connecting three free-standing riser towers to the FPSO by flexible jumpers
Hybrid riser towers have now become one of the most investigated solutions at bid stage for ultra deepwater field developments, due to their capability to accommodate large diameter risers, reduced load on FPSOs and demanding flow assurance requirements. They allow a robust layout with a large flexibility for future expansions of the field.
Based on its experience and the lessons learned along the Girassol development and more recently the Greater Plutonio project, also in Angola, Subsea 7 has developed a “preferred” architecture of the hybrid riser tower. The preferred architecture was subjected to a failure mode, effects and criticality analysis (FMECA), covering its design, fabrication, installation and in-service life. This thorough review provided:
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a technical hierarchy of system/sub-system/unit-equipment/part that sets in perspective all the elements of the riser tower; this is the common basis for the standardization of both engineering and procurement in view of reduction of cost and delivery.
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A semi-quantitative method of failure assessment to ensure that any risk associated with the design or construction was adequately mitigated
As a typical example, large heat losses generated by convection heat transfer is mitigated by using separate material for insulation and buoyancy.
Hyperflow is a trademark of Subsea 7, patents and patents pending.
The Hyperflow Hybrid riser tower consists of a bundle of risers of varying diameter and function (production, water and gas injection, service line, gas lift riser) bundled together.
The bottom of the riser tower is anchored by a flexible joint to a locking device which anchors the tower firmly to the seabed. The top of the riser tower bundle is connected to a buoyancy tank which maintains it in tension. The tops of the risers are in turn connected with flexible jumpers to the FPSO.
The hybrid riser tower ensures efficient project delivery, providing a fast route to first oil. The system can be installed prior to the arrival of the FPSO on-site and quickly connected.
