That's certainly part of it. However, there are obvious military reasons for being interested in the surface of the desert, too -- advantages that would disappear should we ever decide to kick the Saudis in the chops.
It's a tightrope walk, for sure. But I think we've still got the upper hand, because the precarious position of the Saudi royalty would become untenable if they simply kicked us out. Saudi support for terrorism is probably less a matter of sympathy, than it is a matter of bribing the mullahs to leave them alone.
You've got THAT right. If we pull out of Saudi, and Saudi turns into another 1979-Iran.