The density porosity is usually abbreviated DPHI or PHID on log panels and denoted as   in equations.

The key measurement is the bulk rock density  (log name RHOB) from Litho-Density Tool.

The key model parameters are:

The values of  and  are calibrated for each lithofacies individually and can be assessed as vertical axis cut-off on  cross-plot against the lab core porosity  and shaliness . 

The model also accounts for saturating rock fluids with fluid density .

In overbalance drilling across permeable rocks the saturating fluid is usually mud filtrate. 

In underbalance drilling the saturating fluid is identified from resistivity logs.  

The total density porosity  equation is:

\phi_d = \frac{\rho_B - \rho_m}{\rho_{fl}-\rho_m}

The effective density porosity  equation is:

\phi_{ed} = \phi_d -  \frac{\rho_{sh}-\rho_m}{\rho_{fl}-\rho_m} \cdot V_{sh}

The fluid density  is calculated in-situ using the following equation:

\rho_f = s_{xo} \rho_{mf} + (1-s_{xo}) ( s_w \rho_w + s_o \rho_o + s_g \rho_g )

The matrix density is calculated from the following equation:

\rho_m = \sum_i V_{m,i} \rho_{m,i}

where 

 – volume share of the i-th matrix component,

 – density of the i-th matrix component,

.