Seismic modeling and inversion

The seismic method of petroleum exploration has always been an inverse technique. The explorationist has used data from seismic and other sources to derive an indirect description of a potential reservoir. Key to his success has been the use of forward-modeling methods to aid him in relating what he sees in the seismic data to what he expects to see, based on his hypothesized geologic model These forward-modeling methods have developed from simple ray-tracing procedures that determine travel time, to more sophisticated methods that model the total wavefield. These methods include extensions of ray techniques, along with propagator and finite-difference methods. The formation of subsurface images from the seismic data has traditionally involved the use of inversion principles. The operations of deconvolution and migration are inverse methods that aid in the production of enhanced images of the subsurface. In recent years, the development of more direct methods of inversion has been initiated, based on scattering theory. These methods seek to estimate the acoustic or elastic parameters of the earth for ever more general model assumptions. Good progress has already been made using the assumption that the processed seismic data emulate the response of a horizontally stratified earth to a plane-wave excitation. Research is continuing to generalize the assumptions to include point-source excitation and a general scattering model of the subsurface.