Economic success is the most important issue (after HSE) in today´s oil and gas industry (exploration and production business). This issue is becoming more significant for all sizes of companies working in this industry. The era of major exploration success with the discovery of huge fields is over. Additionally challenges to field developments are increasing rapidly, due to geology, politics and finance. These challenges can be cushioned somewhat by price development; nevertheless companies are forced to improve their operations and business development strategies. There are three possibilities to improve economic success and guarantee continuation of business: •Exploration for new fields. •Expenditure reduction. •Production increase. The development of mature reservoirs is a possibility to increase the economic success. International oil companies often sell mature fields to smaller independent national companies. Whereas the international companies usually generate marginal profits, the smaller companies foresee a longer economic production period. Application and investment in new technologies provides a great opportunity to improve economic success, especially in mature field operations. Today approximately 40 % of world hydrocarbon production is generated from mature fields. These mature fields are very sensitive to poor decisions, because most of them are already managed close to their economic limit. Younger fields are much easier to produce and margins are much higher, but massive investment is required. Furthermore the risk associated with exploration is much higher. If knowhow and proven new technology are available, mature fields provide great opportunities for small companies. With the correct implementation of proven new technologies several positive impacts on overall mature field operation can be achieved. In the first instance failures of downhole systems can be reduced, through protection of given equipment and selection of more suitable materials and equipment. The result is a reduction of expenditure related to workover operations and replacement of failed equipment. A further outcome of new technology implementation is an increase in oil and gas production through improvements in inflow performance and increase in run time of wells. Thus two of three possibilities mentioned above can be achieved by the consequent implementation of new and proven technology (expenditure reduction and production increase). Implementation of new technology is associated with investment. The amount of investment required can be generated out of a given budget, without the need for any additional funding. Furthermore after a certain period of time the expenditure level can be reduced and additional cash flow for the company is generated. This is only possible with a well thought out plan for the implementation and monitoring of the application of new and proven technology in the field. This thesis presents technologies used at RAG E&P Company to operate their mature fields and proves the economic value and success with detailed analysis of workover operations, equipment failures, availability of producing wells, marginal cost, production decline, expenditure and income.