Toward microbially-enhanced shale gas production
Toward microbially-enhanced shale gas production.
The Antrim Shale formation in the Michigan Basin is one of the most productive shale gas formations in the US, and optimal resource recovery strategies must rely on a thorough understanding of the complex biogeochemical, genetic, and physical interdependencies in this and similar systems. With funding through Schlumberger-Doll Research (SDR) my lab genetically profiled the prokaryotic communities present in formation water of three closely spaced gas producing Antrim shale wells. Companion incubation experiments were also established by adding different substrates to aliquots of these waters in an effort to stimulate the microbial methane generation. The three wells exhibited substantial differences in their microbial community structure, which was most likely attributed due their different drilling and fracturing history. The majority of the recovered bacterial phylotypes were related to fermenting bacteria, but sequences closely related to sulfate-, iron- or nitrate reducers were also detected. Sequences identical tomethylotrophic methanogenswere recovered from all three investigated well waters, whereas sequences closely related to the hydrogenotrophic methanogens were recovered from a single well.Addition of methanol and trimethylamine resulted in the greatest increase in direct methane production in the formation waters, while an increase in fermentation triggered by the addition of yeast extract and formate indirectly stimulated hydrogenotrophic methanogens. The addition of sterile powdered shale also stimulated the rate of methane production, potentially a result of an increase in surface area available for biofilm development (Wuchter et al., submitted to Environmental Microbiology).