Palmer-Mansoori CBM Cleat Permeability Evolution Calculator

Model dynamic coal permeability changes as a function of depletion pressure, balancing cleat compaction against matrix shrinkage rebound using the Palmer-Mansoori (PM) equation.

Geomechanical & Shrinkage Properties

Initial Reservoir Pressure P_0 (psi):

Current Depletion Pressure P (psi):

Initial Cleat Porosity φ_0 (%): Face & butt cleat network porosity

Initial Permeability k_0 (mD):

Young's Modulus E (psi):

Poisson's Ratio ν:

Max Volumetric Strain ε_L (dimensionless): Matrix shrinkage strain constant

Langmuir Pressure P_L (psi):

Cleat Permeability & Porosity Output

Dynamic Permeability k(P):

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Permeability Ratio k / k_0:

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Current Cleat Porosity φ:

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Matrix Shrinkage Strain ε_m:

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Cleat Compaction Term:

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Net Permeability Trend:

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Frequently Asked Questions

Why do CBM wells often see rising production years into their life?

Unlike conventional wells that decline continuously, CBM wells exhibit a "negative decline" curve. As deep reservoir depressurization triggers massive coal matrix shrinkage, cleat permeability rebounds by 5× to 10×, allowing gas production to ramp up for several years.

What is the Palmer-Mansoori inflection point?

The inflection point is the reservoir pressure where cleat compaction reaches its maximum detriment and matrix shrinkage takes over. Beyond this pressure, further drawdown causes exponential permeability increases.