You may have dismissed the oil well to quickly. The see is open and flowing. navies and armies float around and people do stuff there. But no one resides in a place in the ocean. The oil well and its platform is attached to the bedrock. The platform has a crew inhabiting rooms on a permanent 24/7 basis. They extract resources and sell them to ships.
Of course the oil and gas are a huge reason why the conflict is happening, however an oil platform isn't a landmass so it can't be used to claim territory.
Build a man a fire and he'll be warm for a day, Set a man on fire and he'll be warm for the rest of his life.