115
subsurface sulfate compounds and create hydrogen sulfide gas (H 2 S) as a byproduct.
H 2 S is toxic to humans and also causes the production gas to become “sour” and
corrosive. It must be removed before the gas will meet pipeline specifications and
can be sold. Biocide alternatives, such as disinfection with ultraviolet light, have
been found to be less economical (Kahrilas et al. 2015).
Biocide types are either oxidizing (i.e. bleach, peroxide) or non-oxidizing. Nonoxidizing biocides tend to be gentler on equipment and rock formations, and are
more commonly used in hydraulic fracturing operations. There are two main classes:
lytic biocides attack and dissolve the cell walls of bacteria, while electrophilic biocides bind themselves to bacterial cell walls (Kahrilas et al. 2015).
Biocides are effective at controlling “most” of the downhole microbes. A fraction of a percent with a resistance to the biocide will survive, however, and following Darwin’s Law of Natural Selection the survivors pass that resistance on to their
descendants. A metagenomic analysis compared microbial populations in produced
water from the Marcellus Shale, which may be recycled through a dozen different
fracks, with microbes in Bakken Shale produced water, which is only used once and
then disposed of. The study found that microbial populations in the Marcellus water
were three to four orders of magnitude greater those found in the Bakken water
(Lipus et al. 2017). The biocide-resistant microbes were found to biodegrade some
of the organic frack fluid additives, creating new toxic daughter products that may
impact human and ecological health.
The handling of produced waters from shale gas and tight oil development is a
major production cost and poses huge economic challenges to the industry. These
fluids have also been identified as the primary concern for potential human exposures, because they contain both chemical additives from the hydraulic fracturing
process and the naturally-occurring components of the brines that are produced with
the oil and gas (HEI, 2019). While large spills of produced water are rare (Cozzarelli
et al. 2017) small spills do occur on a somewhat regular basis during storage, transport, and disposal operations (Orem et al. 2017). Improved handling protocols,
monitoring, and training of workers can help reduce the frequency and seriousness
of these incidents.
References
Akob, D. M., Mumford, A. C., Orem, W., Engle, M. A., Klinges, J. G., Kent, D. B., & Cozzarelli,
I. M. (2016). Wastewater disposal from unconventional oil and gas development degrades
stream quality at a West Virginia injection facility. Environmental Science & Technology, 50,
5517–5525.
Bair, E. S., & Tomastik, T. (2012). Geologic and hydrogeologic factors controlling how stray gas
from the English #1 Well Invaded Residential Homes, Geauga County, Ohio, Causing One
In-Home Explosion. Presentation at Stray Gas Incidence and Response Forum, July 24–26,
Cleveland, Ohio, in Veil, J. (2012). A white paper summarizing the stray gas incidence &
response forum, Ground Water Protection Council, 48 p. http://www.gwpc.org/sites/default/
files/files/stray%20gas%20white%20paper-final(2).pdf. Accessed 25 Oct, 2019.
References
subsurface sulfate compounds and create hydrogen sulfide gas (H 2 S) as a byproduct.
H 2 S is toxic to humans and also causes the production gas to become “sour” and
corrosive. It must be removed before the gas will meet pipeline specifications and
can be sold. Biocide alternatives, such as disinfection with ultraviolet light, have
been found to be less economical (Kahrilas et al. 2015).
Biocide types are either oxidizing (i.e. bleach, peroxide) or non-oxidizing. Nonoxidizing biocides tend to be gentler on equipment and rock formations, and are
more commonly used in hydraulic fracturing operations. There are two main classes:
lytic biocides attack and dissolve the cell walls of bacteria, while electrophilic biocides bind themselves to bacterial cell walls (Kahrilas et al. 2015).
Biocides are effective at controlling “most” of the downhole microbes. A fraction of a percent with a resistance to the biocide will survive, however, and following Darwin’s Law of Natural Selection the survivors pass that resistance on to their
descendants. A metagenomic analysis compared microbial populations in produced
water from the Marcellus Shale, which may be recycled through a dozen different
fracks, with microbes in Bakken Shale produced water, which is only used once and
then disposed of. The study found that microbial populations in the Marcellus water
were three to four orders of magnitude greater those found in the Bakken water
(Lipus et al. 2017). The biocide-resistant microbes were found to biodegrade some
of the organic frack fluid additives, creating new toxic daughter products that may
impact human and ecological health.
The handling of produced waters from shale gas and tight oil development is a
major production cost and poses huge economic challenges to the industry. These
fluids have also been identified as the primary concern for potential human exposures, because they contain both chemical additives from the hydraulic fracturing
process and the naturally-occurring components of the brines that are produced with
the oil and gas (HEI, 2019). While large spills of produced water are rare (Cozzarelli
et al. 2017) small spills do occur on a somewhat regular basis during storage, transport, and disposal operations (Orem et al. 2017). Improved handling protocols,
monitoring, and training of workers can help reduce the frequency and seriousness
of these incidents.
References
Akob, D. M., Mumford, A. C., Orem, W., Engle, M. A., Klinges, J. G., Kent, D. B., & Cozzarelli,
I. M. (2016). Wastewater disposal from unconventional oil and gas development degrades
stream quality at a West Virginia injection facility. Environmental Science & Technology, 50,
5517–5525.
Bair, E. S., & Tomastik, T. (2012). Geologic and hydrogeologic factors controlling how stray gas
from the English #1 Well Invaded Residential Homes, Geauga County, Ohio, Causing One
In-Home Explosion. Presentation at Stray Gas Incidence and Response Forum, July 24–26,
Cleveland, Ohio, in Veil, J. (2012). A white paper summarizing the stray gas incidence &
response forum, Ground Water Protection Council, 48 p. http://www.gwpc.org/sites/default/
files/files/stray%20gas%20white%20paper-final(2).pdf. Accessed 25 Oct, 2019.
References