A semi-analytical model for drainage and desorption area expansion during coal-bed methane production

The proposed semi-analytical model is verified by numerical simulation with excellent agreement with the simulation data. Results show that the drainage area expands much faster at early production stage than that at late stage when desorption area starts expanding in the coal-bed reservoir. In addition, the production system of CBM well is found to play a significant role in the expansion characteristics of desorption area. Considering these characteristics of CBM, we shed light on the production system optimization in different production stages and apply the developed production system to a CBM well in Qinshui field, China. In summary, this method only requires BHP, gas and water production, and turns out to be simple, reliable and powerful in application.