The giant oil field Matzen, located in the Vienna Basin, Austria is subject to a modern geological and geophysical re-examination. Almost 50 years of production make this field a mature asset in traditional terms. 3D seismic and applied sequence stratigraphy are being used to re-assess the geological architecture and the depositional setting of the field. An integrated project approach (quick review-early results, Integrated Petroleum Engineering Studies and a Field Development Plan) is taken to identify and quantify the remaining oil and gas reserves and to assess the most economic and cost-effective production of these reserves. First results reveal a more complex geology than previously recognized--both structurally and stratigraphically--which, in combination with existing production data, will lead to new exploitation opportunities. The future implementation phase--drilling, re-completions, etc--will be based on the findings of the ongoing project.