Microbial Dynamics and Control in Shale Gas Production

Abstract

Microorganisms can cause detrimental effects in shale gas production, such as reservoir souring, plugging, equipment corrosion, and a decrease in hydrocarbon production volume and quality, thus representing a multi-billion-dollar problem. Prefracturing fluids, drilling mud, and impoundment water likely introduce deleterious microorganisms into shale gas reservoirs. Conditions within the reservoir generally select for halotolerant anaerobic microorganisms. Microbial abundance and diversity in flowback waters decrease shortly after hydraulic fracturing, with Clostridia, a class that includes spore-forming microorganisms, becoming dominant. The rapid microbial community successions observed suggest biocides are not fully effective, and more targeted treatment strategies are needed. At the impoundment level, microbial control strategies should consider biocide rotation, seasonal loading adjustments, and biocide pulse dosing. In shale plays where souring is common, stable 34 S/ 32 S isotope analysis to identify abiotic H 2 S is recommended to evaluate the merits of biocide application in treating reservoir souring. Overall, an improved understanding of the microbial ecology of shale gas reservoirs is needed to optimize microbial control, maximize well productivity, and reduce environmental and financial burdens associated with the ad hoc misuse and overuse of biocides.

Modified Lipid Extraction Methods for Deep Subsurface Shale

“…Unconventional hydrocarbon production in black shales through hydraulic fracturing (Rogner, 1997; Curtis, 2002; Passey et al, 2010; Chengzao et al, 2012), has bolstered the possibility of introducing exogenous microbes which could alter the microbial community structure of the deep subsurface shale ecosystem. Accordingly, isotopic evidence of potential biogenic gas production in the Marcellus Shale (Sharma et al, 2014) and the presence of microbial signatures in produced fluids from hydraulically fractured wells (Mohan et al, 2013; Cluff et al, 2014; Gaspar et al, 2014) has further intensified the significance of microbial activities in relation to the shale ecosystem and energy applications. While unconventional hydrocarbon production has the potential of altering the deep subsurface shale ecosystem, deep subsurface microbial activity can also influence the hydrocarbon production potential and efficiency.…”

Utilizing Lipid Biomarkers to Understand the Microbial Community Structure of Deep Subsurface Black Shale Formations

“…Unconventional hydrocarbon production in black shales through hydraulic fracturing (Rogner, 1997;Curtis, 2002;Passey et al, 2010;Chengzao et al, 2012), has bolstered the possibility of introducing exogenous microbes which could alter the microbial community structure of the deep subsurface shale ecosystem. Accordingly, isotopic evidence of potential biogenic gas production in the Marcellus Shale and the presence of microbial signatures in produced fluids from hydraulically fractured wells (Mohan et al, 2013;Gaspar et al, 2014) has further intensified the significance of microbial activities in relation to the shale ecosystem and energy applications. While unconventional hydrocarbon production has the potential of altering the deep subsurface shale ecosystem, deep subsurface microbial activity can also influence the hydrocarbon production potential and efficiency.…”

“…Increased interest in energy extraction and environmental applications of deep subsurface shales has further reinforced microbial research in the deep shale ecosystem Hinrichs and Inagaki, 2012;. The recovery of microbial DNA and biogenic natural gas (Sharma et al, 2013), as well as the temporal shifts in microbial communities of produced fluids from unconventional wells (Mohan et al, 2013;Gaspar et al, 2014;Vikram et al, 2014; are also evidence of pre-or post-production microbial life in shale systems.…”

“…It is also difficult to establish whether the microbes detected in the deep subsurface represent environmental conditions at the time of deposition or if they reflect changes that took place after deposition (Fredrickson et al, 1995b;1997;Fichtel et al, 2015;Inagaki et al, 2015). This is further complicated by the fact that drilling and fracturing fluids used during development, introduces large quantities of labile carbon, nutrients, and exogenous organisms into the subsurface Lester et al, 2015;Gaspar et al, 2014;) making it unclear whether indigenous communities exist in these shale formations. These challenges highlight the need for a better understanding of subsurface microbial communities and the microbial role in global biogeochemical processes (Hinrichs and Inagaki, 2012).…”

“…Geologic, hydrologic, and anthropogenic processes operating on a variety of time-scales transport microbes to the subsurface, within the subsurface, and in many cases to the surface ecosystem (Stevens, 1997). For instance, deep subsurface shales host diverse microbial communities (e.g., Hinrichs and Inagaki, 2012;Mohan et al, 2013;Gaspar et al, 2014), some of which are inadvertently brought to the surface during hydrocarbon exploitation through drill cuttings, retrieved cores, and produced fluid.…”