Hybrid Riser Foundation Design And Optimisation

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractHybrid risers rely on axial tension, generated by a combination of aircan and distributed buoyancy, to control their static deflection and dynamic response. In deep water, the base tension required to achieve an acceptable response can be significant (70-1000Te). This tension must be reliably reacted into the seabed over the life of the development. Depending on the configuration of the selected foundation there may be, in addition to axial tension, bending moments, shear loads and loads arising from flexure of rigid base jumper spools. The result is a complex set of load conditions, which, when combined with installation issues, can lead to a foundation system that is a significant cost element in the overall riser system. A number of foundation designs have been proposed and used for free standing risers however, the selection and design process is often not clear. This paper presents a review of the potential design solutions depending on water depth and design loads and outlines approaches adopted on existing projects. The key design and installation drivers are discussed, allowing improved understanding of the issues and the impact on the global riser design and installation strategy. The paper also discusses issues and implications of extending free standing risers to ultra deep water, which often have soft seabed conditions, further compounding the foundation design process.

Roncador P-52 Hybrid Riser Review: Key Concepts, Construction and Installation Challenges

“…Petrobras contracted 2H engineering to develop the FEED with closed ends Buoyancy Can using the flexible jumper connection on top of FSHR as in Figure 1; Further, Hatton et al (2005) discussed the foundation adopted by Petrobras with a conventional well construction and grouted pile. Petrobras contracted 2H engineering to develop the FEED with closed ends Buoyancy Can using the flexible jumper connection on top of FSHR as in Figure 1; Further, Hatton et al (2005) discussed the foundation adopted by Petrobras with a conventional well construction and grouted pile.…”

“…Some of the advantages and disadvantages of this type of foundation were also addressed by Hatton (2005) and despite the necessity of bigger piles for this riser foundation, compared with the ones used for pipeline initiation, it can be an effective solution as well. This can be used to have a better understanding and control of the orientation and flexibility of the foundation making it easier to design and minimize the size of stress joints, for example, as well as to lower the number and complexity of the necessary engineering analysis.…”