This master thesis presents the application of the Target Pressure Method (TPM) and the material balance method to the Sabah field. The applicability of the TPM is proved and the advantages of this method compared to other techniques are demonstrated. Improvements to the TPM have been suggested and also applied in this thesis. The Sabah field, a naturally fractured reservoir, is located in the south-western part of the Sirte Basin in Libya. The reservoir is situated on a local high within the Zella graben and has been discovered in 1964 by the Alwerath Oil Company. Since then seventy wells have been drilled into this reservoir. Both, the material balance method and the TPM, use field data to match the pressure history by determining the water influx requirements. In the TPM water influx occurs through defined boundaries of the productive area. Both methods give the possibility to determine aquifer pressure support and the parameters of analytical aquifer models at a very early stage of the dynamic modeling process. The TPM facilitates the recognition of deficiencies in the geological reservoir model and can be used to provide feedback to the geological modeler. It also allows for the determination of outer (surrounding the productive area) aquifer parameters, an area of the hydrodynamic system that is usually without any direct measurements. Using both methods analytical aquifer parameters have been determined. The correctness of the analytical aquifer parameters calculated with the TPM was proved by successfully recalculating the history in prediction mode. The main water influx was found to be occurring from the south of the Sabah field. The five target regions could be excellently matched with the TPM. Discrepancies between measured and calculated pressures for the central region - a control region- indicate potential improvements of the geological model.