Design and Implementation of a Coalbed Methane Extraction Device Using Microwave Radiation

Abstract The continuous growth of the population and the global economy increases the need for sustainable energy. To this end, the recovery factor of hydrocarbon resources in the world should be maximized. One of the main sources of natural gas is coalbed methane, a gas accumulated in pores inside coal. On the other hand, methane gas explosion is a potential hazard in coal mines, which causes many casualties every year in coal mines worldwide. Mine ventilation alone cannot create a safe environment for coal mining due to the high volume of gas released in some coal seams. Therefore, Methane gas extraction can turn one of the major hazards in coal mining into a clean energy source and have dual benefits. Unfortunately, the permeability of most coal seams is very low, and this low permeability limits the development and production of commercial coalbed methane. Therefore, coalbed methane reservoir stimulation is an attractive option because the relative permeability of natural fractures in the coal seam and the surrounding rock greatly affects the amount of extractable gas. Microwave radiation is one of the new methods to increase the permeability of coal. In this research, we design, simulate and implement a small, lightweight, portable microwave gun that uses a conical horn with an aperture of 28 cm with a working frequency of 2.45 GHz to evaporate the moisture in the circle with a diameter of 40 cm from a coal wall and increases the permeability of the wall due to microwave radiation. Because in previous studies, the tests were performed only on large and small capacity devices without any control over the amount of microwave radiation and by replacing the gas inside the chamber with argon or nitrogen gases, which does not represent the real conditions in the mines. Therefore, by building a small device, we have overcome the limit of coal size and amount. By considering the coal ignition temperature, we have provided the challenges related to removing oxygen from the air and the possibility of working in real conditions in mines with larger volumes of coal, which is very similar to the mining environment. Also, the proposed small and portable device in this paper allows us to use it in different environments.