NOVELTY - The method involves subjecting streams fed into a distillation column (C) to distillation for recovering a gas stream (1) enriched in methane (2) at a top of the column and a liquid stream enriched in carbon dioxide (3) at a bottom of the column. The gas stream enriched in the methane is partially condensed and introduced into a gas/liquid separator (S1) for recovering gaseous fraction (g1) enriched in the methane and a liquid fraction (l2) enriched in carbon dioxide (5). The liquid fraction enriched in the carbon dioxide is fed into the top of the column as a reflux.    USE - Method for treating a pre-dehydrated feed hydrocarbon gas stream containing carbon dioxide and methane to obtain gas stream enriched in methane and liquid stream enriched in carbon dioxide for oil productions field at liquefied natural gas (LNG) plants.    ADVANTAGE - The method enables treating the hydrocarbon gas stream containing acid contaminants, thus reducing amounts of water and of heavy hydrocarbon components from the gaseous stream during pre-cooling treatment, eliminating the need of severe upstream pretreatments, reducing energy consumption and installation costs. The method enables providing the liquid/gas separator making the gaseous fraction depleted with crystallization-generating components to be passed through the heat exchanger, so that the liquid fraction enriched with the crystallization-generating components is directly fed into the distillation column in a temperature zone in which crystallization cannot occur, thus suppressing risk of plugging the heat exchanger or downstream conduits with paraffinic waxes and hydrates. The method enables prefened heat exchangers to multi-pass plate fin heat exchangers (PFHE) or printed circuit heat exchangers (PCHE), thus allowing more efficient and complete heat recovery than heat exchangers in series while remaining compact.    DETAILED DESCRIPTION - The gas/liquid separators are cyclonic separators or gravity separators. The method enables allowing refrigerant fluid selected from a group consisting of ethane/propane, ethylene/propane or carbondioxide/hydrofluorocarbons. An INDEPENDENT CLAIM is also included for a device for treating a pre-dehydrated feed gas stream.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a structure illustrating a method for treating a pre-dehydrated feed gas stream containing carbon dioxide and methane.    Distillation column (C)    Gas/liquid separators (S1-S3)    Gaseous fractions (g1, g2)    Liquid fractions (l1, l2)    Gas stream (1)    Methane (2, 4)    Carbon dioxide in liquid stream (3)    Carbon dioxide in liquid fraction (5)