Abstract
Abstract The Papagayos formation in the Cuyana Basin, Argentina is one of the most prolific and mature reservoirs in the YPF portfolio. Currently it has a 98% water cut with an estimated recovery factor of 56%. The challenge was to determine if there was untapped oil in the field and subsequently how to economically extract it. To identify the source of the current oil production and potential new oil, well logs on infill wells were analysed. We also constructed a full field dynamic model that was history matched to production rates, RFT’s, gradient surveys and compared to historical water saturations identified on infill wells. To reduce uncertainty and to confirm the mechanism by which oil remained in the subsurface, we cross referenced the results of the simulation model against lab 2D visual cells filled with glass spheres to reproduce any trapped oil seen in the simulation. Well logs saw oil at the top of the reservoir; however it was not known if this oil was mobile. With the parameters history matched, the simulation showed the presence of mobile attic oil underlain by a water saturated zone swept by the aquifer. The simulation also demonstrated that the reservoir has multidarcy permeability; hence water coning would be a major issue to consider. The simulation model enabled an estimation of the aquifer strength and demonstrated that it would have a major impact on any recovery process. Simulations were made to determine if the aquifer could be either used to assist any new recovery process or otherwise if it could be subdued. Multiple EOR options were considered to exploit this remaining attic oil, however the most economic option was to augment the aquifer by injecting water on the flanks. Lab results corroborated the simulation and showed that attic oil could be a result of both coning and the structure of the reservoir. Also it was seen that increasing water injection rate into the 2D visual cells (augmenting the aquifer at high water cuts) lead to an increase in oil recovery. Despite a strong aquifer and both high water cuts and recovery factor, it was possible to identify and develop economic oil by applying an integrated modeling methodology. The model demonstrated that augmenting the aquifer is easier than fighting it by applying an EOR approach that requires massive injection to overpower the aquifer. Linking simulated reservoir response to 2D visual cell displacements demonstrated the effectiveness of flank water injection in increasing oil recovered.
Published Version
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