Subsea system and method for pressurization of a subsea oil reserve by injecting at least one of water and gas

The present invention relates to the injection of water and gas, either simultaneously or alternately, into subsea wells in order to enhance production and the oil recovery level. Thus, the present invention provides a subsea system for pressurization of a subsea oil reserve by injecting at least one of water and gas, comprising (i) at least two subsea injection wells (4, 4'), each subsea injection well (4, 4') being connected to a production unit (5) by means of an individual subsea line (1, 2) which is connected to the respective subsea injection well (4, 4') by a principal injection mandrel (6, 6'), and (ii) at least one jumper (3), each jumper (3) hydraulically connecting two of the at least two adjacent subsea injection wells (4, 4 ') by means of annulus mandrels (7, 7'). The present invention further provides a subsea reserve pressurization method associated with the above-described system.