The layer where Tupi was found has more than enough area to harbour a reservoir the size of Ghawar (800Km x 200Km). But Tupi's reservoir is much smaller (if in fact it's only one).

Beyond the seal that holds a deep oil column, Ghawar is even more impressive because of the incredible extent of the reservoir, a cavity almost 300 Km long.

Ghawar is even more impressive because of the incredible extent of the reservoir, a cavity almost 300 Km long.

The reservoir is a cavity? I never realised that.

If you mean an open space filled only with oil, its not.