A buoyancy fluid is sealed in an interior central bore of a completion liner with a plug assembly in the interior central bore. The buoyancy fluid has a lower density than the fluid contained in the wellbore. The buoyancy fluid reduces the force, and thus friction, at the interface between the liner and the bottom of the wellbore while the completion liner is being run to final depth. When the buoyancy fluid is no longer needed, the plug assembly can be withdrawn uphole from the completion liner and to the surface.