[Happy2BMe]

Not for at least 300 years.

[RightWhale]

Depends how the devices are deployed. Could be as little as three days.

[Bon mots]

Not for at least 300 years.

Not true.
The oil would be unaffected.
Just like if nuclear fallout were to land on packaged food. It would be exposed, but not contaminated.

The oil is so far underground as to not be affected by the radiation.

The part about the kill zone being uninhabitable for 300 years is also hyperbole. Look at Las Vegas. Right beside major nuclear test zones - in fact the USA tested some 1030 nuclear weapons - most of them near Las Vegas. Yet it's less than 60 years after the first blast and Las Vegas is inhabitable. No problemo.

Now if we used neutron weapons, it would be immediately inhabitable to boot.
Just sweep up the ashes and Mecca would make a great bowling alley.