Enormous concrete fixed structures
placed on the bottom, typically with oil storage
cells in the “skirt” that rests on the sea bottom.
The large deck receives all parts of the process
and utilities in large modules. Typical for 80s and
90s large fields in 100 to 500 water depth. The
concrete was poured at an at shore location, with
enough air in the storage cells to keep the
structure floating until tow out and lowering onto
the seabed. The picture shows the world’s largest
GBS platform, the Troll A during construction