On the left of the photograph is the oil platform Brent Alpha being decommisioned at Hartlepool. I have always wondered about how oil rigs are supported. It turns out that this one was built up on a tower from the seabed because the sea is only 140 metres deep at that point. This website has a film about what they decided to do https://www.shell.co.uk/sustainability/decommissioning/brent-field-decommissioning/jacket.html So in Hartlepool they are only recycing the top section. Here is some more information about that oilfield https://en.wikipedia.org/wiki/Brent_oilfield
This page lists the different ways of supporting a rig https://en.wikipedia.org/wiki/Oil_platform#Fixed_platforms
