# Direct probabilistic inversion

Qeye has developed a direct probabilistic seismic inversion approach where the seismic reflections are directly inverted for the facies within the constraints of geological prior statements.

The input data for the prior statements are expressed as probability density functions. The prior statement is extremely smooth and consists of thickness distributions for the facies and transition rules for facies to be placed in neighboring cells. Both thickness distributions and transition rules can be drawn from wells in the area of interest and can be informed by geological interpretation of the area of interest.

Because the prior statements contain geological information about facies (i.e. shales, gas sands, oil sands and water bearing sands) below tuning thickness these will be considered by the inversion as plausible solutions, however implausible transitions (such as an older shale over a younger shale) are rejected. This also means that elastically very similar (or identical) facies that are separated stratigraphically are discriminated in the inversion results.

This approach allows a robust handling of uncertainty and non-uniqueness and avoids making pointwise rather than local or global assumptions.