Industry Insights | Building Robust Earth Models in One Step

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How have full waveform inversion and data domain least-squares reverse time migration evolved into a methodology that makes it feasible to build robust earth models in one step? What are the benefits of a one-step non-linear density estimation?

In his latest Industry Insights article, Andrew Long discusses a new simultaneous inversion workflow based on a vector reflectivity modeling procedure. The output of the inversion is a high-resolution velocity model and an accurate estimate of earth reflectivity with compensation for incomplete acquisition, poor illumination, and crosstalk from multiples.

The formulation of the ‘PGS Ultima’ solution removes the density term from the modeling and migration engine, so reflectivity changes in the input data are not erroneously mapped as velocity updates. Another natural benefit is that relative density volumes can be directly recovered from the velocity and reflectivity outputs.

The comparison below shows depth slices of relative density at 3550m below MSL. The result in the upper panel was obtained using a traditional 3-term AVA equation and pre-stack time migrated image gathers, and the results in the lower panel were obtained from the output velocity and reflectivity models derived by PGS Ultima. Note how the traditional density result is noisy and difficult to interpret. In contrast, the result derived from the reflectivity and velocity models is highly coherent and interpretable.

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