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Abstract Brown field rejuvenation has been one of the yardsticks of any operator to improve production. Bringing more life to the brownfield generally comes by finding and monetizing the bypassed oil. Identifying bypassed oil in brown fields has always remained a challenge. Critical analysis of the pressure-production data to understand the production fairways and thus identify bypassed areas for potential infills has been a strong requirement by the operator before going into expensive, time taking detailed three-dimensional reservoir modeling. Field X is a 40 year old producing field which is faulted, having multi-stacked reservoirs. Recent studies by the operator indicated no further infill potential. With the challenge of sudden production decline, a relook study was warranted to look for bypassed oil and infill potential. A new approach of change of Sigma flow potential vs Recovery fraction for each reservoir, helped to determine the existence of bypassed oil. A low, base and high estimate of the bypassed volume was calculated based on the slope of the curve trained to the drive mechanism of the reservoir. To further identify the potential area of the bypassed zone, the fault block was divided by decline analysis into dynamic production regions and normalized drainage bubbles. With the results of bypassed oil volume and potential location by this approach, low, base, high infill recovery was estimated based on recovery factor. To verify the results from Sigma analysis, dynamic model was built for the identified reservoir only, history matched, bypassed oil region identified, and infill potential was estimated. Infill reserve estimated by both sigma plot and from model matched closely. Being economic, the operator successively drilled the same and found oil as predicted. Estimated ultimate recovery from this infill currently in production matches closely with that from the Sigma analysis. Thus, the actual data acted as a blind test for the results from this new approach. This process helped to identify infill opportunities quicker, thus mature projects faster. With this success, the new Sigma analysis has been carried out in two more field blocks and helped to identify more infills which are currently being reviewed by dynamic simulation in target reservoir only. This paper provides the details of the new Sigma approach of finding bypassed oil in brown fields with the field examples. It is emerging to be a simple, easy to use valuable approach to find bypassed oil with the recent success of infill production identified by this analysis. Currently, it is being planned to replicate this approach in another field in the region.