FINITE DIFFERENCE MODELING OF FRACTURE FILLED GAS HYDRATES TO STUDY ITS ANISOTROPIC BEHAVIOR

Abstract

Thin isotropic elastic layering in the earth is one cause of seismic VTI anisotropy, along with intrinsic anisotropy and fractures. In K.G. Basin the anisotropy in the medium has been seen and it was an important task to estimate the accurate anisotropic parameters so that subsurface mapping could be done with greater confidence. As in that area Gas Hydrates occurs in veins so there is a possibility of exhibiting anisotropy in the medium. In our case it is Gas-Hydrates which exist in small fractures in shale and the whole medium behaves as Horizontally Transversely Isotropic (HTI) medium. So this study has been carried out for a better understanding of anisotropic behavior of concerned area. This study verifies the implication of Backus average for calculation of anisotropic parameters of a particular transversely isotropic medium knowing the velocity, density and thicknesses of individual constituent layers obtained from well log data. With the successful establishment of Backus average for Gas Hydrate scenarios too,, it is possible to talk about velocities of medium in lateral and oblique direction by measuring the properties only in vertical direction.