A study of potential occurrence of biogenic methane in coal seams

A significant proportion of the total gas emitted from coal mining, particularly for shallow seams (depth), is believed to have been generated from microbial activities within the coal seams and water filling the pores and fractures in coal. To investigate the potential and extent of gas generation in coal due to microbial activities, we developed a method to culture and monitor the production of biogenic methane in coal. We then applied the method to study the process of biogenic methane generation in coals from a mining region in New South Wales. Fresh coal core samples were collected from an exploration borehole drilled into a sequence of coal seams at a greenfield site where five coal seams were located between the depths of 50 to 250m. The formation water was collected from an adjacent borehole drilled into the same sequence of coals. The coal samples were crushed and mixed with formation water and other solutions in glass vials, and then placed in pre-designed incubator at in-situ temperature to allow the production of methane over the life of the project. The results of measurements show that biogenic activities take place and that methane is generated. Methane continued to be produced throughout the life of the project for the studied coals.