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Seismic Reservoir Characterization to Delineate Areas for Early Development, Vaca Muerta Formation, Argentina


Over the last years, there was the necessity to carry out seismic reservoir characterization projects for the Upper Jurassic Lower Cretaceous Quintuco Vaca Muerta mixed carbonate siliciclastic system in the Neuquén basin to infer petrophysical properties from seismic data with the aim to distinguish or recognize upside zones for early development. The successful use of seismic inversion as a 3D predictive tool to estimate subsurface elastic parameters that can be linked to petrophysical variables by rock physics models requires detailed calibration among seismic, wells, and outcrops along with the awareness of the methodology´s uncertainty. Several preceding projects demonstrated the value and benefit of seismic reservoir characterization and rock physics models for Vaca Muerta (Sharma et al. 2015, Santana et al. 2016, Convers et al. 2017, Acevedo et al. 2018). In the current work, the evaluation of over twenty 3D seismic inversion projects calibrated with around 120 wells is presented, sectorized in areas (north, central and south) based on the geological characteristics of Vaca Muerta and its stage of development. The “soft sediment/friable shale” rock physic model, a modified version of Dvorkin and Nur Friable sand model (Dvorkin and Nur, 1996), was regionally calibrated to well data to relate critical petrophysical parameters with the elastic response for Vaca Muerta reservoirs. Self-similarity between porosity and kerogen content is observed, therefore it is not clear whether their influence on the elastic response can be separated. Additionally, uncertainty analysis for seismic elastic inversion indicates that the inversion errors are much lower than the expected variation in acoustic impedance, higher or comparable for Vp/Vs, and always higher for density for seismic data qualities comparable to the available in the study area (Kautyian et al. 2017). As a result, mostly acoustic impedance inversion projects (75%) were completed for Vaca Muerta regionally. Low acoustic impedance intervals, indicative of higher porosities zones, constitute main regions to be identified as one of the fundamental multi components required for the play. Examples across the basin to describe the impact of seismic reservoir characterization to delineate areas for early development for Vaca Muerta will be described.