The relative amount of space left between objects that are packed together; gap.(noun)
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Use "voidage" in a sentence
"So I'm not sure that answers your questions, but we are successfully replacing a significant portion of our voidage, with the balance being from the water column."
"Are you able to talk about voidage replacement and some of the metrics you've seen with regard to your waterflood, or water injection, I mean?"
"So that doesn't match our voidage, but we're seeing very good pressure response or recovery from this injection."