Abstract The Santos Basin, with an area of about 350.000 km 2 , is the largest salt basin of the South Atlantic, and due to its high economic hydrocarbon potential, it is a recurrent theme in scientific studies. The salt structures over the region present great importance for hydrocarbon accumulation and the geological/geophysical studies are performed from seismic reflection data, which requires time and efforts for acquisition and data processing. We identify salt structures using a new workflow based on inversion of residual gravity anomalies, where we use the Moho and basement depths obtained from gravity inversion, followed by the calculation of the gravity residual anomaly, assumed to be representative of the salt structures. This workflow is tested for a geological profile in the Santos Basin, and the results are evaluated along a 2D seismic section tied to well markers. The geometry of the stratified salt obtained from gravity inversion correlates with the seismic interpretation, with the advantage of estimating the entire salt package, including halite and stratified salt. With only seismic data, sometimes the stratified salt can be misinterpreted as sediments. The procedure can be applied to identify salt in sedimentary basins where seismic data is unavailable or of low quality.

Abstract: Seismic is one of the main methods used for the identification of structures and stratigraphic studies in sedimentary basins. In the Santos Basin, numerous 2D and 3D seismic surveys are being conducted in order to get a better image of the geological section to depths beyond the base of salt layer. Crustal modelling studies that make joint interpretation of seismic and gravity data are found in the literature, however there are few studies that relate gravity anomalies directly to salt structures. This work aims to associate gravity anomalies with salt structures from seismic and gravimetric interpretation. For studies aimed to model the crustal structure from gravity field data, the knowledge of two major discontinuities is required, the basement and the Moho. Such interfaces are often not easily seen by seismic and so, during this study, they were found by different methods involving analysis of gravity anomalies. The other interfaces involving density contrasts were analyzed based on seismic interpretation. The results showed that the obtained seismic geological interpretations may provide additional information when compared to gravity anomaly data. In all the modelled profiles, some geological information of the Santos Basin that are not visible in the seismic, could be interpreted according to the geological model and the adjustment of gravity anomaly curves. As a final conclusion of this work, it is suggested that the combined analysis of the two cited geophysical methods, can provide important information about the crustal structure and to assist in modelling the salt layer.

Resumen: El método sísmico es uno de los muchos usados para la identificación de estructuras y en estudios estratigráficos en cuencas sedimentarías. En la cuenca de Santos, numerosos estudios sísmicos han sido llevados a cabo con el propósito de obtener una mejor imagen de la sección geológica a profundidades más allá de la base de la capa de sal. En la literatura, se encuentran estudios de modelado de la corteza que hacen interpretación conjunta de datos sísmicos y de gravedad, sin embargo, hay pocos estudios que relacionan directamente anomalías de gravedad a estructuras de sal. Este trabajo busca asociar anomalías de gravedad con estructuras de sal interpretadas a partir de datos sísmicos y gravimétricos. Para los estudios encaminados a modelar la corteza a partir de datos de campo de gravedad de la corteza, se requiere el conocimiento de las dos mayores discontinuidades, basamento y Moho. Estas interfaces a menudo no son fáciles de ver mediante sísmica y por esto durante este estudio, ellas fueron encontradas por diferentes métodos envolviendo análisis de anomalías de gravedad. Las otras interfaces que involucran contrastes de densidad se analizaron mediante interpretación sísmica. Los resultados mostraron que las interpretaciones sísmicas y geológicas obtenidas podrían proporcionar información adicional al compararlas con los datos de anomalía de gravedad. En todos los perfiles modelados, alguna información geológica de la cuenca de Santos que no es visible en la sísmica, podría ser interpretada de acuerdo a el modelo geológico y al ajuste de las curvas de anomalía de gravedad. Como una conclusión final de este trabajo, es sugerido que el análisis combinado de los dos métodos geofísicos citados, puede proveer información importante acerca de la estructura de la corteza y ayudar en el modelado de la capa de sal.