Gravity and Gravity Gradients Joint Inversion in Salt Basins through an Integrated Workflow

We introduce a workflow for a constrained joint inversion of gravity and gravity gradients. Our scope is to perform a reliable multi-source modelling with focus on salt basins. This task is still a central issue in exploration, with rising interest for underground gas storage. Geological settings of this type include tricky and relatively deep targets (e.g.: the base of salt and the autochthonous salt also called mother salt). These sources produce anomalies with different wavelength-content. In this framework, the interpretation and modelling of gravity and gravity gradients data could assume great significance, as these datasets are characterized by different wavelength-content. The proposed workflow incorporates a sequential joint inversion via cross-gradient constraint. Following this scheme, we can decouple and then minimize the three terms of the combined objective function: gravity data and gravity gradient data objective functions and cross-gradient term. We perform the separate inversion modifying the focusing algorithm to exploit different types of "a priori information" such as the top of salt and its density from seismic interpretation and the inhomogeneous model-weighting function estimated by the MHODE method. We applied our method on the Seg Advanced Modeling Phase I model, and we obtained a reliable modelling for both shallow and deep sources. Results are substantiated the by the analysis of the cross-gradient term and by the linearization and clustering of the retrieved density models.