Re: create Vp and Vs model using seismic
I want to create Vp and Vs cube from seismic cube in Petrel, let me know how to do it
I don't know about Petrel, but you would normally determine Vp and Vs from pre-stack data, not post stack.
These properties can only be "inverted" from the seismic data of you have a range of angles of incidence present - the variation of the seismic reflection amplitude with the angle of incidence is defined by the Zeoppritz equations : http://en.wikipedia.org/wiki/Zoeppritz_equations
Vp is usually determined from the velocities used in seismic imaging. The accuracy of the Vp measurement depends on the processing techniques employed. The most accurate P-wave velocities will have been determined by anisotropic pre-stack depth migration; prestack time migration will be less accurate, and simple stacking velocities the lowest grade estimate of all.
Vs is then usually defined by looking at how the amplitude of the seismic reflection varies with the angle of incidence (AVA), using an approximation (such as Shuey) to the full Zeoppritz equations. Sometimes you may find that the variation of amplitude with offset (AVO) is used, with the offset being used as an approximation for the angle.
Usually you'd do this work in a specialised piece of software, and then display the results in Petrel - its possible there's a plugin in the "Ocean" framework for doing this kind of thing.
If you want good results, its very important to work with someone who understands seismic processing and can give advice on the underlying accuracy of the velocities determined from the seismic (based on the techniques used); given the number of approximations typically used, this can be the biggest area of uncertainty which if not correctly accounted for can lead to significant errors.