Characterization of channelized turbiditic reservoirs using elastic properties modeling: An application in the Sergipe-Alagoas basin, Brazil

Abstract

Sandy channelized reservoirs in deep water environments are significant for oil exploration and production. The 3D nature of the outcrops described in the literature and the local limitation of the information acquired through drilled wells are limiting factors for the reliable subsurface characterization of this type of sedimentary environment and its related heterogeneities. Aiming to overcome the information absence between the sampled well points in hydrocarbon reservoir studies, the 3D seismic data is a conventional approach adopted. However, due to the intrinsically low seismic resolution aspect, the usage of inverted seismic volumes enhances the confidence rock properties spatial distribution into the geological models, even though the uncertainties are not eliminated. This study presents a methodology of synthetic elastic properties modeling in association with measured physical properties, velocity, density and thickness to assess and optimize the geostatistical built model using real turbiditic reservoirs data of a Maastrichtian section of Calumbi Formation, in the Sergipe sub-basin, Brazil. It was successively tested geomorphological and geological features, as described in the previous work as well as similar Alagoas Sub-basin outcrops, associating their responses in terms of compressional and shear velocities, densities, and thicknesses, reducing uncertainties in the spatial distribution of them, which are present in high vertical-resolution well data. The obtained results show that compressional and shear waves variations are the main influences for the seismic signal and the related attributes rather than the intrinsically geometrical features. It was built a specific equation intending to model the effects of these attributes over the measured seismic data to identify paths to implement needed corrections in the geometric and faciological characteristics of the evaluated reservoir-rocks. They confirm the importance for better understanding of subsurface geological characterization using the seismic data as conditioning, even below the intrinsically data resolution, especially when dealing with seismic inversion. Additionally, the 1D synthetic model acts to do deal with tuning effect and to control the elastic property distribution avoiding misinterpretations that may suggest unfavorable portions for new well locations, enhancing the hydrocarbon production because it provides feasible elements for project decision-making.