Arguably the most technically and economically challenging subsea component, risers are a key focus for DEEPSEA’s advanced engineering services. Continually improving design methods to control design conservatism one assumption at a time, DEEPSEA is reducing riser system cost whilst increasing the technical certainty of the design.

Examples of the application areas for such advanced engineering services are:

• SCR fatigue analysis with interaction of the riser and soil in the touchdown zone (TDZ)
• Pipe-in-pipe SCRs
• Time domain VIV using coupled FE-CFD
• VIV of multi-pipe non-cylindrical risers, e.g. completion workover risers, bare or finned drilling riser joints
• Riser tower global dynamics including all lines, interaction mechanisms & operational loads (temperature & pressure)
• VIV of riser towers particularly those with external lines

Typical Soil Response behaviour
used for advanced SCR-seabed
interaction analysis

Advanced SCR Fatigue Analysis with Riser-Seabed Interaction

SCRs can offer the cheapest riser solution depending on specific field, environmental and load constraints but the deeper the water the greater the challenge fatigue poses to the design. Detailed soil modeling of the riser-seabed interaction in the TDZ (see diagram below) provides the capability to more accurately represent these critical aspects of the system, thus improving the operability of the design.

Time domain VIV using coupled FE-CFD

DEEPSEA’s approach has been developed to more closely model the physical situation through:

• Use of advanced computational fluid dynamics (CFD) techniques for the hydrodynamic modelling
• Application of CFD generated hydrodynamic data with conventional VIV analysis tools such as Shear7
• Implementation of both the hydrodynamic and structural dynamic modeling in the time domain as opposed to the traditional modal calculations

These modelling and analysis techniques are being applied to a variety of riser design issues often in a complementary role to traditional model testing such as defining the experimental testing scope. They also provide a more cost-effective and faster means to understand system response.

Through DEEPSEA’s understanding of complex structural behaviour and available analysis techniques, many of which are numerical, new design and analysis processes have been developed to suit client requirements and make full use of test or operational monitoring data.