This report will explore the hypothesis that an underground cavity in gassy salt will eventually be gas filled as is observed on a small scale in some naturally occurring salt inclusions. First, a summary is presented on what is known about gas occurrences, flow mechanisms, and cavern behavior after abandonment. Then, background information is synthesized into theory on how gas can fill a cavern and simultaneously displace cavern fluids into the surrounding salt. Lastly, two-phase (gas and brine) flow visualization experiments are presented that demonstrate some of the associated flow mechanisms and support the theory and hypothesis that a cavity in salt can become gas filled after plugging and abandonment