Success Story | Mariner Jacket Detailed Design


SNC - Lavalin UK Limited

Scotland, United Kingdom

SNC-Lavalin Mariner Jacket Design


As part of the USD 7 billion Mariner oil field development project, Statoil selected SNC-Lavalin to perform front-end engineering of a 22,000-ton steel jacket with 50 active well slots. The jacket will have an 88-by-62 meter footprint on the seabed and will rise to a height of 120 meters. It will support production, drilling, and quarters in topside facilities weighing 54,000 tons. The jacket’s weight and barge-launched installation were significant design challenges.


SNC-Lavalin built an integrated model to evaluate storm, seismic, and dynamic response of topsides, jacket, and foundations. Bentley’s SACS software enabled the team to perform the complex analysis of interrelated factors, such as wave loading under-storm conditions, fatigue, sea transportation, and accidental impacts. SACS allowed the team to model multiple design conditions that would conform to U.K. Health and Safety Executive safety requirements for the highly regulated North Sea.


SACS made it possible to model 19 different cases of dynamic and static loads during construction, transportation, installation, and in-place operation. Changes to the jacket design were implemented quickly. Working with the same software as the topsides designer allowed the interfaces between jacket and topsides to be modeled efficiently. Accomplishing all this in a short period of time allowed the project to be delivered within the tight time schedule dictated by the client, and at less cost.


SNC-Lavalin used SACS to effectively communicate technical elements of the jacket design to various contractors working in geographically dispersed offices. Analysis models were easily exchanged, enabling simultaneous work to proceed on different aspects of the design. During construction, SACS models were transferred to the fabricator when changes had to be made to the structure. STAAD.Pro was used for detailed design of secondary steel. These models were easily modified.

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  • Using SACS as a core software enabled SNC-Lavalin to complete jacket design in a tight time schedule.

  • Ease of use in making design changes reduced engineering hours.

  • Risk was reduced by performing redundancy analysis for scenarios in which elements of the structure were damaged without causing the overall structure to fail.

  • SACS delivered a design that complied with required UK offshore regulatory requirements.

  • SACS also minimized material waste, thus reducing overall project cost.


“Statoil awarded us the FEED for its massive 22,000-ton barge-launched jacket at the Mariner development in the U.K. sector of the North Sea. This was followed by a similar mandate for Statoil's Bressay development, also in the North Sea. When we secured these projects, it was clear that Statoil had recognized our ability to perform the specialized work needed for massive, complex structures. SACS played a key part in achieving our project goals.”

David Maclaren - Head of Structural Offshore, Oil & Gas

SNC-Lavalin UK Limited