Mechpro

UCS = 2.27e – 10 ´ M² ´ [(1 + n)/(1 – n)]²(1 – 2n)(1 + 0.78Vclay)

where

2.27 is a non-dimensional constant.

10 is in psi.

1 is a non-dimensional constant.

2 is a non-dimensional constant.

0.78 is a non-dimensional constant.

M is P-wave modulus in psi; n is Poisson's ratio; and Vclay is clay volume.

Mechpro is the Schlumberger mechanical properties program. The above equation is the Mechpro empirical equation for UCS applicable to sandstones with UCS > 4,000 psi. The equation requires shear velocity data (Dts) to calculate n, as well as density, acoustic, and GR (or NPHI) logs to derive M and Vclay. This equation often yields high values for UCS, which prompted Schlumberger to develop new relationships.