Exact Zoeppritz-inversion of Vp/Vs ratio - Application to a Barents Sea Gas Reservoir

We have introduced a method for probabilistic calculation of the Vp/Vs2 ratio from the intercept, PP-reflection coefficient at a given angle and assumed Vp/Vs1 ratio. The method opens up the possibility to create uncertainty maps, such as a standard deviation and Shannon’s information entropy maps. By a quick scanning over the maps, we can quickly identify zones where the calculations give unstable or erroneous results. Another novelty of the approach is avoiding extraction of the gradient from uncalibrated seismic data. Instead, we find (only) one scaler by dividing the uncalibrated intercept by the intercept from synthetic seismogram and apply it to each gather at the target zone. We tested the methodology on a gas discovery in the Barents Sea.