A value of Effective porosity change due to the rock compaction under reservoir pressure variation p({\bf r}):
| (1) | \delta \phi_e(\mathbf{r}, \ p) = \phi_{e0}(\mathbf{r}) \left( 1- \exp \left[ \int_{p_i}^p c_r(p) \, dp \right] \right) |
where
c_r(p) | pore compressibility (see also Pore compressibility @model ) |
p_i | initial formation pressure |
Since the pore compressibility is very low (~ cr = 0.5 ÷ 1.5 GPa-1) for all subsurface rocks in petroleum reservoirs the
(1) can be written as:
| (2) | \delta \phi_e(\mathbf{r}, \ p) = \phi_{e0}(\mathbf{r}) \cdot c_r(p) \, (p-p_i) |
See also
Petroleum Industry / Upstream / Subsurface E&P Disciplines / Petrophysics (PP) / Volumetric Rock Model / Effective Porosity (PHIE)