US Patent 11255155 Downhole apparatus with removable plugs

A downhole tool includes a casing string with a fluid barrier connected therein defining a lower end of a buoyancy chamber. A plug assembly connected in the casing string defines an upper end of the buoyancy chamber. The plug assembly has an outer case with a rupture disc positioned therein configured to block flow and to burst at a predetermined pressure. The rupture disk is removable from a flow path through the outer case upon the flow of fluid therethrough.