Small deviations of ambient pressure
from initial pressure formation
lead to the exponential changes in porosity:
LaTeX Math Block |
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|
k=k_0 \, e^{n_k \cdot c_r (p-p_0)} |
where
| formation compressibility |
LaTeX Math Inline |
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body | n_k = \frac{\ln (k/k_0)}{\ln(\phi/\phi_0)} |
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| power degree of permeability-porosity correlation |
| permeability at reference pressure
|
| porosity at reference pressure |
| reference pressure, usually picked up at initial reservoir pressure |
The substantial reduction of formation pressure leads to shrinking of numerous pore throats and massive reduction in permeability deviating from exponential.
The substantial increase of formation pressure leads to microfracturing and massive increase in permeability deviating from exponential.