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Initiatives on improved hydrocarbon gas recovery are usually facing challenges which are directly related to representative understanding of reservoir and fluid flow characterization as well as the depletion strategies. A field case study has been used as a platform to explain such challenges and the adopted integrated methodologies toward improving the hydrocarbon recovery from the field. Reliable water saturation modeling, validation of the production allocation, reevaluation of the trapped/residual gas saturation (Sgr), modeling of regional aquifer behavior and its support, connectivity and pressure communication among the fields, fluid contact movement, gas expantion, smeared oil rim and condensate drop-out within the reservoir and appropriate production scenarios (i.e., off take rate, strategy, etc.) are among the challenges. This paper presents on methodologies how to manage the challenges in improving the hydrocarbon gas recovery (i.e., IGR) through an integrated subsurface-surface study for the evaluation of giving a gas reservoir second life i.e. field rejuvenation. The adopted methodology integrates both simple analytical approaches including the the material balance and volumetric assessment as well as the 3D simulation modeling to evaluate the reservoir performance and examine some of these uncertainties and challenges and subsequently identify the value of the field second life through the optimum prediction and production strategies. As the studied field is in pressure communication with neighboring fields in a mega platform carbonate build-up through a stronge regional aquifer, the results from an isolated model for the field showed to be unrealistic and, therefore, an integrated mega platform model is constructed for the purpose of the study. The study integrates the 4D seismic results, regional aquifer and trapped gas saturation modeling, reservoir performance monitoring, and its application to obtain a better history matching results and reliable prediction strategy for recovery factor improvement. By incorporating the 4D seismic results and representative water saturation and residual gas saturation modelling, the resulting history matched model is significantly improved with less degree of uncertainty and it is believed to be more reliable to produce optimum prediction scenarios, which focused on recovery factor enhancement. Various prediction scenarios together with advanced modeling of the regional aquifer effect in a merged mega platform model have been examined using the final history matched model. By doing this, the field recovery factor is improved by 16% and thus giving the field the second live to continue its production. |
