Inversion of large, nearly-homogeneous geobodies via ultra low-dimensional shape representation using orthogonal basis functions

Abstract

A two-stage method for iteratively inverting geophysical data for the purpose of subsurface imaging, including: obtaining at least one geophysical dataset and an initial subsurface model; representing subsurface such that a geometry of a geobody is defined using a set of basis functions, and a number of such basis functions is significantly smaller than the number of cells used in cell-based geobody representations, wherein an order of magnitude reduction is two or more for 2-D domains and 3 or more for 3-D domains; in a first stage, successively updating the initial subsurface model, only for the geobody, by performing iterative low-dimensional geophysical inversion based on minimizing a misfit between simulated geophysical data and the geophysical dataset, wherein the simulated geophysical data is generated from a current subsurface model at each iteration; generating a subsurface image from a final updated subsurface model obtained via the low-dimensional geophysical inversion, wherein the subsurface image includes an inverted geobody; in a second stage, successively updating the subsurface model with the inverted geobody by performing iterative cell-based geophysical inversion based on minimizing a misfit between simulated geophysical data and the geophysical dataset, wherein the simulated geophysical data is generated from a current subsurface model at each iteration.