LINEARIZED TARGET-ORIENTED INVERSION - APPLICATION TO REAL DATA

We have developed a procedure for target-oriented linearized inversion in the k-omega domain, exploiting the weak scatter hypothesis. The te chnique is successfully demonstrated on the Mobil AVO data set, on a t arget zone located at a depth of 2 km and centered on a well location. The first step of the technique is the description and compensation o f propagation effects through the overburden (datuming), which ideally brings sources and receivers from the surface to the target level. Ou r datuming code uses plane-wave transfer functions of the overburden, computed by tracing Gaussian beams through the macro-model. The proces s resembles an amplitude-consistent, prestack downward continuation, i n laterally varying media. The macro-model of the overburden is obtain ed from standard seismic processing using well data to constrain the v elocity analysis. The second step is the linearized inversion of the t arget. Operating within the linear approximation in the k-omega domain , we gain the advantage of the simplicity of the theory. We are also c apable of controlling the negative effects of acquisition geometry and limited bandwidth on resolution. Ambiguities are carefully avoided by inverting only well-conditioned components. We obtain an image of the target that has tendencially minimum contributions of errors from lac k of experimental resolution. This ''seismic'' image can be used as in itial macro-model for interpretation, techniques of lateral continuati on of well information, petrophysical and geostatistical analysis and 4-D surveys. The general agreement with well data is excellent for an unusually long depth interval of 500m. This validates our global proce dure including datuming and inversion.