Abstract: The full reservoir under study is Mishrif reservoir of Y oil field which is an Iraqi giant carbonate reservoir mainly consists of limestone rocks that belong to Late Cenomanian age with average total thickness around 400 mand OIIP close to 10MMMSTB. Mishrif reservoir started to produce since, May, 2005 by primary recovery but the reservoir pressure is significantly declined over the past 5 years due to sharply increasing of oil production and the current reservoir pressure around many wells is slightly exceeded saturation pressure, although, pilot water injection program had been executed since, May, 2015. Due to the limitation of available water for injection around Y field, there’s a necessity to optimize the use of this limited water resource through a proper water flooding design and an efficient development scenario to achieve the maximum oil recovery and the longest life cycle of this of carbonate reservoir. In this study, based on three dimensional simulation model matched, a full-field development plan under water flooding secondary recovery was designed by using conventional reservoir simulation for around 23 years of prediction for meeting with the field operator’s strategic production requirements. One strategy of pattern water flood has been proposed with modified staggered line drive pattern to achieve a field production plateau rate of 300 MSTB/D by progressively adding 124 new producers and 96 injectors. For providing an additional support to pattern water flooding for maximizing oil recovery from the reservoir under study, another strategy is planned with adding 40 new peripheral injectors along reservoir periphery to pattern flood strategy with maintaining of field production plateau rate and number of producers of pattern flood strategy. The results of feasibility analysis showed that the addition of peripheral wells is an unfeasible choice because of gaining a comparatively small profit in final oil recovery, around 0.77%, through exploiting a great amount of water injected in these new wells which required more additional expenditures and further water resources for injection purposes that have not available around the field under study.