Inversão gravimétrica 3D de bacia sedimentar com variação do contraste de densidade com a profundidade segundo uma lei parabólica

Abstract

We present a gravity inversion method for estimating the 3D basement relief of a sedimentary basin. We assume that the density contrast between the basement and the sediments decreases with depth according to a parabolic law. We discretize the sedimentary section into a grid of 3D vertical, juxtaposed prisms in both horizontal directions. The prisms’ thicknesses represent the depths to the basement relief and are the parameters to be estimated from the gravity data. To produce a stable solution we maximize the smoothness of the estimated relief using the overall smoothness regularization. We apply our method to synthetic data from simulated complex 3D basement relief and the results show well-resolved estimated relief, starting at different initial guesses. These results are obtained if the values defining the parabolic decay of the density contrast with depth are known. We conducted a numerical analysis to investigate the solution sensitivity to the effects caused by: (1) random noise in data, (2) the depth to the true basement relief, and (3) the density-contrast decay with depth according to the parabolic law. We show that, if the density contrast in the deepest portion of the basin is above a threshold, our method retrieves the 3D geometry of the basement relief regardless of the true basement depths and regardless of the pseudorandom noise sequences.