Enhancing coal bed methane recovery: using injection of nitrogen and carbon dioxide mixture

Nitrogen (N-2) and carbon dioxide (CO2) gases injection yield substantially various recovery ways. Here, a one-dimensional mathematical model is applied comprising of mass balances for explaining gas sorption and flow, and a geomechanical relationship to describe the permeability changes during gas injection. That's why numerical simulations for investigating the performance of injecting flue gas mixture in enhanced coal bed methane (ECBM) recovery are represented. Significant intuitive features are found regarding the gas flow dynamics at the time of displacement and influences of sorption on ECBM operation. The study revealed that the injection of pure CO(2)causes much reduction in cleat permeability, but pure N(2)is injected to increase the permeability without any loss of injectivity. Therefore, pure CO(2)causes more efficient displacement in terms of total CH(4)recovery, while the addition of N(2)to the mixture assists to make quicker the initial methane recovery.

Automated summary

The study uses a mathematical model to explain the effects of gas injection on gas sorption, flow, and permeability, finding that pure N2 injection can increase permeability without losing injectivity, while pure CO2 injection significantly reduces permeability.