sludge vs goop

sludge and goop both are nouns.

Word	Noun	Adjective	Verb	Adverb
sludge	Yes	No	No	No
goop	Yes	No	No	No

As nouns, sludge and goop are synonyms defined as:

Other synonyms of sludge include goo, gook, guck, gunk, muck, ooze, slime.

sludge (noun)	goop (noun)
any thick, viscous matter	street names for gamma hydroxybutyrate
the precipitate produced by sewage treatment	any thick, viscous matter