Ann: Project Icewine Operations Update, page-372

With the greatest of respect to other opinions, that is not correct. Firstly there has been no gas flow reported only some hydrates which are a form of hydro carbon crystal formed in hydrocarbon water mixes, a bit like a snow flake, when the temperature is low enough. Tiny quantities of hydro carbon do dissolve into water.
But taking the scenario the poster describes where a gas cap forms in the top of the well bore, it is still the pressure from the reservoir pushing the liquid column above that creates the squeeze of that gas cap. The gas will have displaced a section of the water in the wellbore making the hydrostatic head lighter, so enabling more pressure at the top. Well head pressure when shut in is always going to be exactly reservoir pressure minus the static head weighing on it. Reservoir pushes up, hydrostatic pushes down