Stimulating methane generation within coal seam reservoirs

Methane generation by microbial activity or biogenesis is a significant source of coal bed methane (Faiz and Hendry, 2006; Strapoć et al, 2011). Being able to stimulate microbial methane generation in a coal seam reservoir has the potential to add significant value to depleted or undersaturated fields. Several laboratory studies have demonstrated that this process can be stimulated through the addition of inorganic nutrients (Jones et al, 2010; Orem et al, 2010). These studies, performed at atmospheric pressure on crushed coal, provide encouraging support for the concept of inducing in-situ biogenic methanogenesis and increasing gas-in-place in coal bed methane reservoirs. Important questions, however, remain about how laboratory results relate to what occurs in the reservoir. This extended abstract presents the results from a series of core flooding experiments conducted at reservoir pressure and temperature on intact coal core samples. Nutrient consumption is characterised by measuring the nutrient balance between the inflow and outflow waters. Gas content is measured through a helium flood at the end of the experiment, during which the pore pressure is dropped to atmospheric pressure to drive off any adsorbed gas. These experiments confirm that microbial gas generation does occur at reservoir pressure and temperature, and at high enough rates to rapidly increase gas content.