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Acquiring Geometries and Heterogeneities of Blowout Dunes Using GPR (Ground Penetrating Radar)


The production of oil and gas from aeolian reservoirs in Paleozoic and Mesozoic sedimentary basins in Brazil has increased in the last 10 years. Most of these reservoirs occur in thin sedimentary units with complex geometries. Thus, the energy industry is interested in the characterization of recent and old aeolian deposits, mainly those related to coastal systems. In this work, still in progress, blowout dunes geometries are being parameterized to contribute to the construction of a database that subsidizes 3D reservoir modeling. Another objective of the present study is to characterize the main depositional heterogeneities on macroscopic and megascopic scales. These heterogeneities are responsible for the development of high permeability zones and/or barriers to fluid flow in aeolian reservoirs. For this purpose, Ground Penetrating Radar (GPR) data were acquired parallel and perpendicular to the sedimentary flow in blowout dunes using 200 MHz antennae. The survey comprised more than 2 km of geophysical profiles, which were visualized in a 3D environment. The maximum depth of GPR penetration was 30 m. The GPR method allowed the identification of first, second and third order bounding surfaces, which represent dune-basement interface, overlapping of dune generations and episodes of erosion/aeolian reactivation, respectively. The study also identified details of the interactions between the four radarfacies and estimated structure distribution, such as grainfall, grainflow, and wind-ripple strata. The geometries obtained in this study may be used for comparison with other analog deposits and petroleum reservoirs and for stochastic simulations. The present study could provide a more accurate model and allow a more effective exploitation of oil reservoirs of aeolian origin.