Abstract: A method and an apparatus (100) for reducing the pressure of a natural gas (2) at a wellhead of a natural gas field. The method provides prearranging an energy recovery expansion device (20), which comprises a stator and a rotor mechanically connected with a power generator (29), and a gas passageway between the rotor and the stator, and conveying the natural gas into the passageway of the energy recovery expansion device (24) to cause a rotation of the rotor and the expansion of the gas, the pressure being reduced from the extraction pressure (P1) to the use pressure (P2), which makes it possible to obtain an electric power (W) during the expansion, adapted to satisfy the energy requirements of the gas extraction unit, in particular of an offshore platform, without installing local electric generators.

Abstract: A method for separating methane from at least one hydrocarbon with two or more carbon atoms in a substantially gaseous fluid, containing more than 3 ppm of water, in particular a natural gas coming from a natural gas field or from a natural gas pipeline, or a refinery gas or another gas available at an extraction pressure set between 15 and 300 bar, and an apparatus. The method provides prearranging an expansion device having at least one first expansion equipment, selected from the group comprised of: a radial expansion device and a static expansion device, in which a first expansion takes place with a cooling effect down to a temperature that is higher than the solid formation temperature that may be formed starting from water and/or hydrocarbons present in said gas, and further having at least one second expansion equipment which is arranged downstream of the first expansion equipment.

Abstract: A method and an apparatus (100) for reducing the pressure of a natural gas (2) at a wellhead of a natural gas field. The method provides prearranging an energy recovery expansion device (20), which comprises a stator and a rotor mechanically connected with a power generator (29), and a gas passageway between the rotor and the stator, and conveying the natural gas into the passageway of the energy recovery expansion device (24) to cause a rotation of the rotor and the expansion of the gas, the pressure being reduced from the extraction pressure (P1) to the use pressure (P2), which makes it possible to obtain an electric power (W) during the expansion, adapted to satisfy the energy requirements of the gas extraction unit, in particular of an offshore platform, without installing local electric generators.