News
Pitt Researchers Undertake $1.06 Million Federal Project to Curtail,
Reuse Harmful Wastewater From Marcellus Shale Drilling
PITTSBURGH—The U.S. Department of Energy recently
selected the University of Pittsburgh as one of nine national partners
that will develop techniques for curtailing the possible environmental
and health hazards associated with tapping the massive natural gas
reserves lying beneath Pennsylvania and surrounding states. Roughly
70 percent of Pennsylvania sits atop the Marcellus Shale formation,
which experts estimate contains up to 500 trillion cubic feet of
natural gas with about $500 billion worth of recoverable gas.
Researchers in Pitt’s Swanson School of Engineering will lead
a three-year, $1.06 million project to better manage the wastewater
generated by the extraction process used on the Marcellus Shale.
Difficult to treat, the wastewater usually languishes in reservoirs
or the environment. The Pitt approach calls for a new method that
would allow the water to be safely reused in gas wells that would
contain extraction costs, limit the byproducts flowing into the
environment, and reduce the strain on freshwater sources currently
tapped during extraction. Furthermore, the researchers seek to tackle
the problem of acid mine drainage—the environmentally damaging
water flowing from old mines—by using it as a sanitizer and
supplemental water source.
“Our approach is to not only reuse the wastewater, but also
reduce the level of treatment it requires prior to being reused,
which should be a much more economical approach,” said Radisav
Vidic, chair of the Swanson School’s Department of Civil
and Environmental Engineering and a William Kepler Whiteford professor.
“And by reusing the acid mine drainage readily available at
many gas drilling locations, we can manage acid mine drainage from
older mines and wastewater from current drilling operations, both
of which are serious environmental concerns.”
Vidic heads the project with Eric Beckman, codirector of
Pitt’s Mascaro Center for Sustainable Innovation and the George
M. Bevier professor of chemical and petroleum engineering. They
will work with Carnegie Mellon University assistant professor Kelvin
Gregory. The National Energy Technology Laboratory (NETL)—the
lead research and development office for the U.S. energy department’s
Office of Fossil Energy—will contribute more than $794,000
to the effort, and Pitt will provide around $269,000.
The technique for mining the Marcellus Shale is known as hydraulic
fracturing. A high-pressure mix of local-source freshwater, sand,
and various chemicals known as “slicking agents” fractures
the rock formation and allows trapped gas to escape. One gas well
can consume 2 million to 5 million gallons of fluid with 25 to 100
percent of it returning to the surface as wastewater, or “flowback.”
Flowback contains varying levels of hydrocarbons, heavy metals,
natural radioactive materials, and very high levels of total dissolved
solids (TDS). TDS includes such substances as calcium, potassium,
sodium, chloride, and carbonate; Marcellus Shale flowback tends
to have much higher concentrations of TDS than wastewater from other
hydraulic fractured sites.
In Pennsylvania, flowback—which can have five times the salinity
of seawater—is typically stored in reservoirs or trucked to
a brine treatment plant. But current treatment processes cannot
remove the majority of TDS, so many of these substances typically
end up in surface water. In their project proposal, the Pitt team
refers to a 2008 incident when treated flowback released into the
Monongahela River resulted in TDS levels exceeding safety limits
set by the Pennsylvania Department of Environmental Protection.
The department restricted the amount of flowback treatment plants
could receive, which halted some drilling operations in Western
Pennsylvania.
To contain flowback pollution and freshwater consumption, Vidic
and Beckman will first develop new slicking agents that would be
stable in high-salinity water. These chemicals would allow for the
flowback to be reused in adjacent gas wells without extensive off-site
purification. Then, they will study the use of locally available
acid mine drainage to further treat the flowback and simultaneously
supplement the freshwater supply. Finally, the cleaner flowback
would be pumped back into the gas well, reducing the strain on freshwater
sources and curtailing costs of shipping and storing wastewater.
The project will consist of a research phase and a subsequent field-demonstration
phase.
Pitt is the only Pennsylvania institution granted a project. The
eight other projects include ALL Consulting in Tulsa, Okla.; General
Electrical Company; West Virginia University; the University of
Arkansas; the Ground Water Protection Research Foundation in Oklahoma
City; the Geological Survey of Alabama; Altela Inc. in Albuquerque;
and the Texas Engineering Experiment Station.
More information on the projects is available on the U.S. energy
department Web site at www.fossil.energy.gov/news/techlines/2009/09058-DOE_Selects_Natural_Gas_Projects.html
