Optimal scheduling for enhanced coal bed methane production through CO₂ injection

Enhanced coal bed methane production with CO₂ injection (CO₂-ECBM) is an effective technology for accessing the natural gas embedded in the traditionally unmineable coal seams. The revenue via this production process is generated not only by the sales of coal bed methane, but also by trading CO₂ credits in the carbon market. As the technology of CO₂-ECBM becomes mature, its commercialization opportunities are also springing up. This paper proposes applicable mathematical models for CO₂-ECBM production and compares the impacts of their production schedules on the total profit. A novel basic deterministic model for CO₂-ECBM production including the technical and chemical details is proposed and then a multistage stochastic programming model is formulated in order to address uncertainties of natural gas price and CO₂ credit. Both models are nonlinear programming problems, which are solved by commercial nonlinear programming software BARON via GAMS. Numerical experiments show the benefits (e.g., expected profit gain) of using stochastic models versus deterministic models.