The identification of new oil fields onshore Trinidad and Tobago has become almost impossible. Therefore the possibility of producing by-passed hydrocarbon accumulation from the matured Catshill field was determined through a holistic field development plan using waterflooding. The field development plan involved detailed reservoir characterization study. There were two phases of development plans considered. (1) Injecting water above the bubble point for a new field development (2) Injecting water below the bubble point using existing field data. Effective use of petrel aided the building of all geological maps of the area. Maps generated in Petrel were exported to Computer Modelling Group (CMG) for detailed reservoir simulation study. The estimated oil in place was 27.541MMSTB. Primary production yielded 27.2% recovery factor which was less than half of the oil in place. Implementation of water injection above the bubble point pressure yielded 49.8% recovery factor when produced for 10 years. By injecting water below the bubble point pressure using staggered line drive pattern, the recovery factor was 39.4%. It can be concluded that developing a field using waterflooding is best when pressure is high. However, there could still be significant recovery (39.4%) when field is matured. Economically, production will not be profitable if the oil price goes below 46 US$/bbl.