Mobile foundations for subsea infrastructure
This study investigates novel foundation solutions for supporting subsea infrastructure in deep water. Deepwater developments typically comprise a series of subsea wells tied back to a central processing facility (CPF). The wells are connected to the CPF by a network of in-field flowlines across the seabed. The flowlines merge or terminate at subsea structures such as pipe-line end terminations or manifolds (PLETs or PLEMs) that are usually supported on shallow foundations, commonly called ‘mudmats’. These structures are installed not only to provide support for bearing capacity but also to facilitate controlled lateral pipe buckling or pipe-walking during operational shut-in and start-up cycles.
A current design challenge is to provide mudmats that are capable of withstanding the required loads and which can be installed with currently available installation vessels. In many cases the required size of mudmats are too large or too heavy to be installed when designed by conventional bearing capacity methods. Currently, the alternative is to provide deeper foundations to support the structures, but this has logistical and economic downsides.
This project will advance understanding about the foundation-soil interaction around subsea mudmat foundations to optimise their design. The study will involve a series of centrifuge tests implemented by numerical modelling.
Mudmats are employed extensively as in-line support for pipelines in deep sea water installations. Current methods of design are increasingly unable to meet the needs for deepwater offshore development. This project will contribute towards developing an optimised foundation solution to support deepwater subsea infrastructure.