This thesis supports the re-development work of a Libyan oil field in the Sirte Basin, which is producing since 1966. Pressure decreased rapidly after production was started, therefore a line-drive waterflooding scheme was implemented in the early 1970s to provide pressure support. Within the next few years, a re-development will take place to improve the sweep of the waterflood, as there are some areas of the field, where the production performance is insufficient. The objective is to analyze the injection scheme and recommend modifications to improve the flood efficiency. Finally, possible drilling locations for new injection and production wells should be provided to significantly enhance the oil recovery. The suggested re-development actions should be underpinned by an economic evaluation. To gain a first insight and indications analytical analysis were performed. Pressure, water-oil-ratio, water cut, areal and vertical sweep efficiency calculations and a Buckley-Leverett-calculation were conducted. Afterwards material balance calculations were performed using MBAL, regarding the results of the analytical methods. A MBAL-model was built in a way that it is able to reproduce historical behavior of the field in a sufficient way. Based on the analytical pressure analysis and the MBAL model three pressure regions were identified that show characteristic pressure trends: “Low”, “High” and “Increasing”. To further transfer those results into a numerical model, simple box models were created using PETREL. The locations of those blocks within the field were chosen such, that each block represents one pressure region. To optimize the waterflood performance, simulations on the blocks were performed using ECLIPSE with different pattern configurations. The additional recovery was evaluated to find an optimum well arrangement with the most favorable spacing and to decide whether or not to modify the injection scheme. It was determined that two regions of the field should be converted to a 5-spot-pattern flood instead of the currently installed line drive. Cumulative oil production could be enhanced significantly by re-arranging the injector/producer setting.