Langmuir Isotherm & CBM Gas Content Calculator

Model pressure-dependent methane adsorption storage on coal micropore surfaces, calculate in-situ gas content (scf/ton), and quantify undersaturation.

Coal Adsorption & Reservoir Parameters

Langmuir Volume V_L (scf/ton dmmf): Asymptotic max adsorption capacity

Langmuir Pressure P_L (psi): Pressure at 50% max storage

Initial Reservoir Pressure P_i (psi):

Actual Initial Gas Content G_i (scf/ton): From canister desorption test

Ash Content (% dry weight):

Moisture Content (% weight):

Drainage Area A (acres):

Net Coal Seam Thickness h (ft):

Gas In Place & Saturation State

Saturated Gas Capacity G_s(P_i):

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Critical Desorption Pressure P_des:

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Gas Saturation Degree:

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Dewatering Pressure Drawdown:

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Total In-Place Coal Mass:

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Original Gas In Place (OGIP):

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Frequently Asked Questions

Why do CBM wells produce 100% water during their early production life?

Coal seams are naturally water-saturated aquifers. To liberate adsorbed methane, hydrostatic head must be lowered below the critical desorption pressure (Pdes) by continuous artificial lift pumping. Until pressure reaches Pdes, no gas breaks out.

What is the physical meaning of Langmuir pressure (PL)?

PL indicates how tightly gas is bonded to the coal. A low PL means the adsorption isotherm is very steep: gas desorbs easily at high pressures. A high PL means significant pressure depletion is required before large gas volumes desorb.