A volumetric displacement preservation system for preserving a volume of flowable substance in a vessel. A fluid exchange structure has a stopper, a head portion, and a fluid exchange valve with a first condition where fluid inlet and exhaust pathways in the fluid exchange structure are simultaneously closed and a second condition where the fluid inlet and exhaust pathways are simultaneously opened by conduit joining portions in the fluid exchange valve. A chamber retains a volume of preservative gas and is connected to the fluid inlet pathway externally to the vessel. The preservative gas can be supplied from the chamber into the vessel through the fluid inlet pathway as liquid is exhausted through the fluid exhaust pathway. The chamber can be replenished from preservative gas displaced from the vessel in a reverse volumetric displacement process or from preservative gas supplied by a preservative gas production canister.