This study addresses water injection in a pilot project of the third biggest reservoir of Matzen Field-the 8th Tortonian Horizon (Production Unit 208-10-15). OMV AG is leading a peripheral water injection program in the anticline structure of the 8th Tortonian Horizon. A water injection program was introduced in 1961 for this production unit. Because geological and technical conditions were not suitable, it was decided to perform this project because of the limited options for primary production in the future. As a direct result of that, the average waterflood in production wells was very high. For this reason and because of reservoir heterogeneity, production well S124 was turned to be an injection well in September 2000. After completing observation of properties such as water cut, salinity, dynamic fluid level, and overall development of production values changes from 26 production wells around the treated area since the start of water injection, wells that were influenced by water injection from S124 were determined. Their production changes were taken into consideration for economical estimation and interpretation.