Over the last ten years, Acergy has gained experience in all types of flowlines (rigid, flexibles, bundles) and risers (SCR's Flexibles, single and bundle Hybrid riser Towers). Acergy has also pioneered the use of Hybrid Riser Towers (HRT) and have completed in 2007 the design and construction of the largest bundle HRT. This paper describes the basis of the design of those towers and how they can be standardized to reduce cost. First are identified the functional requirements of the riser systems including those regarding flow assurance. Then the paper further deals with the impact of the risers on the field layout with due account for the interference of the risers between themselves including the effect of VIV. For the selected concept it successively deals with their architecture, the engineering, the fabrication and the installation.


Decisions to produce from a hydrocarbon bearing reservoir imply a high degree of risk. The overall magnitude of the reservoir may be appreciated fairly well by seismic studies, but the connectivity between those reservoirs is much more difficult to assess at the early stages of the field development. Fig. 1 shows typical geological horizons present in the same geographical area but not interconnected. The relatively recent drive towards "wet" tree solutions can be attributed to several factors among which the better drainage allowed by wells drilled from widely spread locations rather than from a single location. Contractors have to propose production systems that minimize the risk taken by their clients. Acergy after having designed many different types of flowlines and risers is proposing a Minimum Production Riser System (MPRS) tailored to one identified object of the reservoir: it becomes then possible to add one or several such systems as the knowledge of the reservoir progresses.

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