Coal Sorption Time (τ) & Matrix Diffusion Calculator

Model Fickian diffusion of desorbed methane through coal micropores into natural cleats, calculating sorption time (τ in days) and matrix desorption half-life.

Matrix Geometry & Diffusion Properties

Average Cleat Spacing / Block Radius r_m (cm): Half of distance between cleats

Matrix Shape Geometry:

Micropore Diffusion Coeff D (cm²/s): Typical: 1e-10 to 1e-8 cm²/s

Coal Rank:

Sorption Time & Desorption Kinetics

Sorption Time Constant τ:

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Desorption Half-Life t_1/2:

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63.2% Gas Release Time:

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95% Gas Release Time:

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Diffusion Rate Parameter (D / r_m²):

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Transport Kinetic Regime:

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Frequently Asked Questions

What is the practical impact of a long sorption time (e.g., τ = 150 days)?

A long sorption time creates a significant lag between wellbore depressurization and peak gas rate. In reservoir simulations, ignoring non-equilibrium sorption overestimates initial gas rates and underestimates long-term reserves.

How does hydraulic fracturing accelerate sorption time?

Hydraulic fracturing induces complex microfractures that shatter coal blocks into smaller fragments, directly reducing the effective diffusion radius rm and slashing sorption time from years down to weeks.