Results of incorporating the stratigraphy within the evaporitic sequence into the velocity field for reservoir characterization

Abstract

There are many ways to build velocity models for seismic migration purposes, either by using inversion algorithms, approximations by constant or variables velocities, including or not including anisotropic parameters, etc. The key aim of these alternatives is to generate a seismic image with better definition and more resolution and therefore, the possibility of obtaining better amplitude responses. However, a good velocity model must be built for further applications derived from seismic data, such as acoustic and elastic inversions, uncertainty analysis of reservoir properties, studies concerning also quality and depth positioning, geomechanical studies, pore pressure estimation regarding drilling risks, among other applications. Amplitude response, as well as other derivative seismic attributes, such as acoustic and elastic impedance, or its associated elastic parameters (coefficient of rigidity, shear modulus, etc) are important parameters for reservoir properties distribution which allied to well data, could ensure a robust distribution of the velocity variations for each geologic unit. Consequently, it’s important to take into account the uncertainties and refinements described before to obtain a reliable velocity model. In this article, we propose a methodology to build seismic velocity models for the evaporitic section considering the presence and variability among different types of salts within it, which strongly influence the reservoir response in the pre-salt section of Santos and Campos Basins. This method considers the workflows integration developed to construct velocity models for the evaporitic section, besides allowing uncertainties analysis and emphasizing where seismic amplitudes can be adequately used for reservoir characterization.