Gas Solubility in Coalbed Methane Reservoirs formula |
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| \( R_s \;=\; \dfrac{ 0.17525 \cdot \rho_b }{ \phi_m \cdot S_o } \cdot V \) | ||
| Symbol | English | Metric |
| \( R_g \) = Equiivalent Gas Stability | \(dimensionless\) | - |
| \( \rho_b \) (Greek Symbol rho) = Bulk Coal Steam Density | \(g\;/\;cc\) | - |
| \( \phi_m \) = Actual Coalbed Cleat Porosity | \(dimensionless\) | - |
| \( S_o \) = Initial Oil Saturation | \(dimensionless\) | - |
| \( V \) = Gas Content | \(SCF \;/\; STB\) | - |
Reservoir gas solubility in coalbed methane (CBM) reservoirs is the ability of methane gas (\(CH_4\)) to dissolve into the water or fluids present within the coal seams. Unlike conventional gas reservoirs, where gas is primarily stored in a free state within pore spaces, coalbed methane reservoirs store gas in a unique way. In CBM systems, methane is predominantly adsorbed onto the surface of the coal matrix, but a portion can also dissolve into the water that saturates the coal's fractures (cleats) and pores.
The solubility of methane in this context depends on factors like pressure, temperature, and the salinity of the water. Higher pressures increase gas solubility, as more methane can dissolve into the water under elevated conditions, while higher temperatures tend to decrease solubility. In coalbed methane reservoirs, the dissolved gas is typically a smaller fraction of the total gas content compared to the adsorbed gas, but it still plays a role in the overall production dynamics.
