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Small deviations of ambient pressure
from initial pressure
fromarion formation lead to the exponential changes in
permeabilityporosity:
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k=k_0 \, e^{\beta_pn_k \cdot c_r (p-p_0)} |
where
is formation compressibility, is permeability at reference pressure (usually picked up at initial reservoir pressure ), is power degree of permeability-porosity correlation:| LaTeX Math Block |
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k = k_0 \left( \frac{\phi}{\phi_0} \right)^{n_k} |
The above correlation assumes constant reservoir compressibility which in most practical applications holds true in a wide range of pressure variations all the way down to porosity cut-off and all the way up to the fracture point.
The substantial reduction of formation pressure leads to shrinking a lot of pore throats and massive reduction in permeability deviating from exponential.
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