Deepwater gas fields require large diameter risers to provide high flowrate. Flexible Risers are limited to about 18", whereas Steel Catenary Risers (SCRs) can go beyond that, for example 20" or 24"OD. Because those SCRs are sensitive to fatigue, they are equipped with Buoyancy Modules (BM) to decouple them from surface dynamics: they form a Lazy Wave configuration and they are therefore called Steel Lazy Wave Risers (SLWR). To solve more stringent fatigue issue, decoupled riser system like SHRs are very efficient. The objective of this article is to present innovative alternatives to conventional development. This paper will present a novel decoupled riser system: the Tethered Catenary Riser (TCR) previously presented at the Offshore Technology Conference (Legras 2013; Legras & Neel 2014). The installation aspects have been further developed and are now only based on field proven and reliable installation procedures. The TCR can be considered as a robust solution for gas development projects, being the most cost efficient decoupled riser system. This paper will also present an alternative solution to install traditional Steel Lazy Wave Riser (SLWR) using a towing solution. By removing the need for a large installation vessel, a towing method can help debottleneck project planning and simplify offshore logistics.

Turret-Moored FPSOs are frequently used for deepwater developments worldwide, with consideration of disconnectable turrets for harsh environment applications. This trend makes the interaction between the FPSO hull, mooring system, and riser systems a vital design parameter for arctic conditions. This paper provides a review of the various riser systems that can be considered for turret-moored FPSOs. These include proven coupled and decoupled systems (flexibles, Steel Catenary Risers, Steel Lazy Wave Risers, and hybrid decoupled riser systems), and also new riser concepts (e.g. the TCR - Tethered Catenary Riser, or the TSLWR - Tethered Steel Lazy Wave Riser). These systems are described in terms of design and functionality. These riser systems are discussed with consideration of the particular challenges of disconnectable turret-moored FPSOs and specificities of arctic conditions.

It has long been recognized that value creation for deepwater projects is predicated based on robust front end engineering and field development planning. Realizing this value requires a multidisciplinary approach that considers early engagement with the SURF execution team and the field development planning specialists, engineering specialists and project execution expertise. This paper presents an overview of recent experience and an illustration of the benefits of this approach. The general principles of field development optimization are presented, with an emphasis on Floater and SURF packages as well as the cost drivers to optimize the interfaces between these packages. This paper plans to explore the benefits of front end engineering design as it relates to early engagement of the SURF and Floater disciplines. The paper will examine through case studies topics such as: subsea production network alternatives, floater and riser conceptual and early phase design, and interfaces between the floater, riser and production system.

Buoyancy modules are widely used ancillary equipment aiming to shape riser systems to resist harsh offshore environments. Due to their thermoset polymeric nature, they are sensitive to the manufacturing parameters as well as subject to water absorption along their service life. To overcome the challenges of polymer-based buoyancy module, this paper explores the design of metallic buoyancy modules that can be 3-D metal printed. An initial material selection is performed to identify suitable material candidates for the optimization algorithm. Steel and aluminum materials are considered and evaluated on a representative case combining density, mechanical stress and buckling criterion. Then a topology optimization algorithm called ‘Adaptative Bone Mineralization’ is applied on the best candidate material, adapting their modulus of elasticity at each iteration according to the current stress distribution, load case definition and boundary conditions. The optimized design incorporates additional requirements related to additive manufacturing processes. Results of the optimization algorithm are presented in a progressive order of complexity starting from the optimization of an angular section of 11.25 degrees opening with symmetrical boundary conditions up to a quarter of half-shell buoyancy module fully optimized in 3D. The optimization process log, capturing the volume fraction and the maximum stress at each iteration, is presented and compared with the selected set of criteria. Impact of the manual reconstruction process of the buoyancy module is assessed and the buckling stability is evaluated as a post-treatment. Two-dimensional and three-dimensional topologically optimized buoyancy modules are presented and comply with the strict mass requirement, stress criterion and buckling stability achieving deep water depth. This novel design approach to create deep water metallic buoyancy modules achieves the tailoring of the buoyancy module's internal structure to maximize the buoyancy performance while ensuring its structural integrity.