Abstract: A method of loading and treatment of a gaseous or liquid hydrocarbon mixture produced on an offshore production platform, a production vessel or a well installation when producing oil and gas from a reservoir, wherein the mixture is supplied to a gas treatment vessel (12) via a buoy loading system comprising a buoy (14) of the STL/STP type, and is treated on board the vessel (12) for producing liquefied natural gas (LNG) or an LPG mixture stored in tanks on the vessel. Simultaneously with the supply of the hydrocarbon mixture, oil is also supplied to the vessel (12) via the same buoy (14), the buoy including a multi-course STP connector, the oil being transferred directly from the STP connector via a pipeline (23) and an unloading means (25) on the vessel (12) to a tanker (13) for storage and transport of the supplied oil.