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Gravity Inversion Using a Binary Formulation

When a nil zone is present in the subsurface salt structure, it effectively creates an annihilator of density contrast that gives rise to zero gravity response on the surface. As a result, part of the salt structure is invisible to the surface data and inversion algorithms often have difficulties in recovering the salt structure correctly. We develop a binary inversion technique in which the density contrast is restricted to being one of the two possibilities: either zero or the value expected at a given depth. The binary condition places a strong restriction on the admissible models so that the non-uniqueness caused by nil zones can be resolved. In this presentation, we will outline the formulation, discuss the solution strategy, and illustrate it with numerical examples.