A Quasi Exact Solution Approach for Scheduling Enhanced Coal Bed Methane Production Through CO2 Injection

The purpose of this research is to provide an easily accessible, effective and efficient solution method for the profit-maximization scheduling problem for CO2-enhanced coal bed methane (ECBM) production. ECBM has been a mature technology which can further extend the value of the unminable coal mines. The total profit of the production is based on the revenue generated by the methane produced as well as CO2 credits earned from the carbon market, and the production cost of the methane along with the CO2 operational cost. This scheduling problem is formulated as a nonlinear optimization program which includes bilinear terms in the constraints due to the modeling of physical reactions. In this paper, we use a quasi exact solution technique to solve the problem, where bilinear terms are eliminated by a discretization and linearization procedure. The original problem is then transformed to a mixed integer linear program with binary variables representing the discretization of the continuous fractional variables involved in those nonlinear constraints. This approach is yielding an equivalent program when enough binary variables are used. Numerical experiments show that this method can be easily implemented and yield almost exact solutions in reasonable computational times.