A first-of-its-kind NETL research project involving the Bakken Shale has shown that a one-size-fits-all approach to understanding the subsurface and overcoming well site operational and water management challenges doesn’t necessarily apply. This is due to the often variable chemical and biological dynamics present at fossil fuel well sites.

The Bakken Shale and underlying Three Forks Formation in the U.S. and Canada are important reservoirs of hydrocarbons that can be recovered using unconventional oil and gas extraction methods, including horizontal drilling and hydraulic fracturing. Although the geochemistry and microbiology of this region are not well understood, they are known to have major implications for well site productivity and water management.

A better understanding of the geochemistry and microbiology in the subsurface might lead to more efficient recovery operations with a reduced environmental footprint. NETL’s research can also set a precedent for studying other formations. It showed that great variations can occur not only among different shale formations but also among different well sites located within the same formation.

NETL researchers analyzed the produced water from 14 unconventional wells in the Bakken Shale using geochemical measurements and quantitative gene sequencing methods. The overarching goal was to acquire a better understanding of the complex geochemistry and geobiology dynamics present in hydraulically fractured wells. Researchers found that Bakken Shale waters have high values of total dissolved solids (TDS) when compared to other shale plays such as the Marcellus and Barnett in Appalachia and Texas, respectively. High values of TDS typically inhibit microbial growth, and several of the sampled wells indicate this is the case in the Bakken Shale.

However, some wells also contained a sulfate concentration trend that suggests a higher occurrence of sulfate reduction. Two wells also had a low TDS concentration, compared to the other wells. Contrary to the other wells, these two wells had a high microbial population. The unique geochemistry and microbial loads recorded for these two wells suggest that the heterogeneous nature of the producing formation can provide environmental niches with conditions conducive for microbial growth.

NETL’s findings suggest that the Bakken Shale well water samples exhibit a localized trend. This means the dynamics behind the corrosion of well components in some locations may not be universal. With this knowledge, extraction and environmental management operations can be re-examined and optimized for maximum efficiency. NETL’s work represents the first study that coupled geochemical trend analysis with microbial data for oil and gas systems and demonstrates geochemical parameters have the potential to shape the microbial community present in the Bakken Shale.

“Ultimately, better understanding of the microbiology and geochemistry of hydraulically fractured wells will help the nation’s industries continue to use our natural resources safely and efficiently,” said Djuna Gulliver, principal investigator in microbiology studies at NETL. “This work is an example of the Lab using cross-cutting research for real-world energy application.”

NETL’s research aims to identify mechanistic links between the produced water microbiota and chemistry. It is anticipated that a meta-analysis of all hydraulically fractured well chemical and microbial data may help identify broader trends present in all unconventional reservoirs.

NETL is a U.S. Department of Energy (DOE) national laboratory dedicated to advancing the nation's energy future by creating innovative solutions that strengthen the security, affordability and reliability of energy systems and natural resources. With laboratories in Albany, Oregon; Morgantown, West Virginia; and Pittsburgh, Pennsylvania, NETL creates advanced energy technologies that support DOE’s mission while fostering collaborations that will lead to a resilient and abundant energy future for the nation.