[RightWhale]

Could crude oil be seeping to the ground surface due to the heavy rains?

Certainly, happens all over the planet. OTOH, it could be somebody buried a barrel of oily waste some years back.

[spokeshave]

Check your property deeds.

If you don't own the mineral rights you could wind up with a drilling rig in the back yard.

Suggest you trade the SUV for a diesel....will run on raw oil with some modifications.