ezygeo-ai/fluid-substitution

Calculate Gassman Fluid Substitution using Python.

Fluid-Substitution

The purpose of this repository is to reconstruct Fluid-Substitution using Python and Jupyter Notebook IDE.

Fluid Substitution : Predict P Wave Velocity

Reference:

Batzle, M. L., and Wang, Z., 1992, Seismic properties of porefluids: Geophysics, 64, 1396-1408.

Berryman, J. G., 1999, Origin of Gassmann’s equation:Geophysics, 64, 1627-1629.

Gassmann, F., 1951, Über die elastizität poröser medien:Vierteljahrss-chrift der Naturforschenden Gesellschaft inZurich, 96, 1-23. The English translation of this paper isavailable at http://sepwww.stanford.edu/sep/berryman/PS/gassmann.pdf.

Han, De-hua, and Batzle, M. L., 2004, Gassmann’s equation andfluid-saturation effects on seismic velocities: Geophysics,69, 398-405.

Hill, R., 1952, The elastic behavior of a crystalline aggregate: Proc.Phys. Soc. London Ser. A, 65, 349-354.

Mavko, G., Mukerji, T., and Dvorkin, J., 1998, The rock physicshandbook: Tools for seismic analysis in porous media:Cambridge Univ. Press.

Get the Fluid Substitution software on https://ezygeo.com

fluid-substitution's Issues

Error in Vp formula

This is a nice notebook - and the accompanying blog post is cool too. It's good to see Python and rock physics on the web - good work!

I believe there is an error in your final calculation of Vp. You pass the initial value of Vs in to this calculation, but Vs changes with the fluid substitution, along with Rho. It is the shear modulus, μ, that is invariant under changes in fluid, so you need to send that into the vp function, instead of computing μ using Vs and Rhosat.

You might like to know that there's a lot of rock physics, including all of these equations, in bruges (repo here), which is open source. It has both Per Avseth's and Tad Smith's formulations, and both of those come out with the following substituted properties (in SI units):

FluidSubResult(Vp=3427.244195668794, Vs=1818.1619642311286, rho=2172.0)

Last thing: I strongly suggest not rounding values before returning them from functions, you could easily end up with rounding errors accumulating. Just return the values at full precision and only round them in your app when you show them in the result (or let the user do it).