The ongoing Mature Oilfield Redevelopment (MORE) program in Matzen pursues the goal to increase the Net-Present-Value by implementing new recovery strategies to accelerate the oil production and to realize possible reserves. The research questions of this thesis and the research itself should arise out of, and contribute to, the discussion of optimizing operating costs issues in Redevelopment projects. The major questions posed for the research are: (1) Which are the main cost drivers of Operational Expenditures in Redevelopment Projects? (2) How can OPEX be optimized? (3) Based on the results of (1) and (2) above, which are the potential opportunities and threats for future OPEX development as a consequence of the MORE program? The theoretical background, concerning cost accounting, cost analysis, industry standards to define OPEX & CAPEX, and an overview of the MORE Concept, was elaborated, to build the basis for the practical part of the thesis. This part starts with the evaluation of the cost structure in OMV Austria, a Review of OPEX split applied and an Analysis of the Dependencies between CAPEX and OPEX in Development/Redevelopment projects, to then identify the main cost drivers in redevelopment projects. The investigation of options for OPEX optimization follows next. The OPEX development after initiation of redevelopment projects was demonstrated in case of the Bockfließ Area. Thereby, the main focus laid on the water management and the use of new electric submersible pumps instead of sucker rod pumps. Finally recommendations were placed regarding what has to be implemented to the MORE concepts to optimize OPEX.