drill rig vs oil rig

drill rig and oil rig both are nouns.

Word	Noun	Adjective	Verb	Adverb
drill rig	Yes	No	No	No
oil rig	Yes	No	No	No

As nouns, drill rig and oil rig are synonyms defined as:

Other synonyms of drill rig include drilling rig, oilrig.

drill rig (noun)	oil rig (noun)
rig used in drilling for oil or gas	rig used in drilling for oil or gas