The oil production in "X" field has been decreasing since 1975. Actually, water injection is used to increase the production and to maintain the reservoir pressure. After converting some wells to ESP, we noticed an important and fast liquid production decline in the reservoir with the actual injection scheme. The aim of this study is to establish a new water injection strategy in order to have an adequate pressure support able to maintain a constant liquid production for all wells. Finally, we analyzed the feasibility of adding new side-tracked wells, identified their optimum location with expected oil production profile and optimized the actual water injection scheme with considering the estimated liquid production of new drilled wells. Key words: Water injection, pressure support, liquid production, ESP, reservoir voidage, optimization, reservoir simulation, producer wells, injector wells.