Numerical Simulation Research of Coal-Bedded Methane Well Output and the Application Analysis

A numerical simulation of coal-bed gas wells is an effective method to determine the estimation prospects of coal-bed gas ground output, production preferences, and recovery assessments, and follows the model selection, data entry, sensitivity analysis, history matching, and production forecasting simulation steps of conventional numerical simulations regarding oil and gas reservoirs. In the present study, a coal-bed methane non-equilibrium pseudo-steady sorption-diffusion model of a coal-bed gas well output, which was combined with a coal-bed gas flow equation, was used to establish a mathematical model of coal-bed gas migration. Then, based on this model, the #3 coal-bed gas well of the southern Qinshui Basin was set as an example. COMET3 software was used to simulate the numerical simulative solution, and to analyze the air changes and water production. The results showed that, based on the dual porosity in a single permeability model of the coal-bed gas flow mechanism, the unknown variables P_g and S_g in the mathematical model of the gas and water transport were derived. Then, through the history matching of the gas and water data obtained by the COMET3 software, and the coal reservoir P_g and S_g parameter dynamic characteristics analysis, it was concluded that after discharge and the mining of the well for a period of 40 days, the coal-bed gas output began to transition from a single-phase flow of water, to an unsaturated single-phase flow. This accurately described the output process of the #3 coal-bed gas well of the southern Qinshui Basin, and provided theoretical guidance for the reasonable coal-bed gas mining of the next stage.