Gardners Relation Between Density and Velocity

Reference

Gardners relation estimates rock density from seismic velocity, filling the gap when no density log exists.

The equation

ρ = 0.31 V^0.25
  • ρ is density in grams per cubic centimeter
  • V is P wave velocity in meters per second
  • 0.31 and 0.25 are empirical constants for brine filled sedimentary rock

Worked example

A velocity of 3000 meters per second implies a density near 0.31 × 7.40 = 2.29 grams per cubic centimeter. Feed that into an impedance estimate and you can model reflections from velocity data alone.

When to use it

A sedimentary average that works remarkably well for clastics but misses in salt, coal, and gas bearing sands, exactly the rocks that make interesting reflections. Use logged density wherever you have it.

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