Velocity to Density / Density to Velocity Conversion

A suite of GM-SYS 3D Tools enable you to convert Vp to density or density to Vp, using one of several published methods. Velocity to Density conversions are implemented as 5th order polynomial approximations of the published relationships. The method names, coefficients, and appropriate velocity ranges are stored in the vel_density.csv file in the Oasis montaj distribution. The reverse conversion is implemented using a zbrent algorithm.

Coefficients for Nafe-Drake, Christensen & Mooney, and Godfrey et al. methods are adapted from Brocher (2005)2. "Gardner" methods use coefficients derived from the tables in Gardner et al., 19741.

For more details on the underlying GXs: in the Oasis montaj Help menu, select Application Help, and in the Oasis montaj Help search for the Velocity and Density Conversions topics.

File Format

You may add your own methods and coefficients to the velocity-density conversion table, by editing the copy of the file: %USERPROFILE%\Documents\Geosoft\Desktop Applications \csv\vel_density.csv.

The format of the file is as follows:

METHOD_NAME,A0,A1,A2,A3,A4,A5,LOWER_LIMIT,UPPER_LIMIT

Method Name

A unique name for the method

A0,A1,A2,A3,A4,A5

The zero-th through 5th coefficients of the polynomial.

Lower Limit

The minimum velocity, in meters per second, for which this method is valid. For no limit, use zero.

Upper Limit

The maximum velocity, in meters per second, for which this method is valid. For no limit, use 50000.

References

  • [1] G. H. F. Gardner, L. W. Gardner, and A. R. Gregory, 1974, "Formation velocity and density - The diagnostic basics for stratigraphic traps", Geophysics, vol. 39 (6), pp. 770-780.
  • [2] Thomas M. Brocher, 2005, "Empirical relations between elastic wavespeeds and density in the Earth's crust", Bulletin of the Seismological Society of America, vol. 95 (6), pp. 2081-2092.

See Also: