Anisotropic Tomography Using Rock Physics Contraints

Anisotropic model building is a well-known challenging problem for its non-linear, ambiguous nature. To reduce the null-space and stabilize the inversion, we propose a new preconditioning scheme in the linearized tomography to include the rock physics prior information. The rock physics information in terms of covariance among P-wave vertical velocity (v0), epsilon and delta is generated by stochastic realizations of a compacting shale model. We design a VSP synthetic survey with the common industry geometry on two different examples to study the effect of applying prior rock physics prior information on proper and improper media, respectively. The results show that by utilizing the proper prior rock physics information, tomography can better resolve the anisotropy parameters, especially in the area where inversion is poorly constrained by the data. However, cautions should be taken when the lithology of the subsurface is unknown. Finally, a posterior uncertainty analysis is performed to evaluate the contribution of the rock physics prior information. The results show that the null-space is greatly reduced by introducing the prior information.