drilling rig vs oilrig

drilling rig and oilrig both are nouns.

Word	Noun	Adjective	Verb	Adverb
drilling rig	Yes	No	No	No
oilrig	Yes	No	No	No

As nouns, drilling rig and oilrig are synonyms defined as:

Other synonyms of drilling rig include drill rig, oil rig.

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