A team of researchers has created a way to quickly and remotely evaluate
fluid flow in subsurface fractures that could impact aquifers, oil and gas
extraction, sequestration of greenhouse gases or nuclear waste and
remediation of leaked contaminants.
Laura Pyrak-Nolte and David Nolte, both professors of physics at
Purdue University, found a nearly universal scaling relationship bet ween
fracture stiffness and fluid flow that applies to low porosity rock, or
roughly more than 50 percent of all rock on Earth.
Through this mathematical relationship the pair created a tool that,
through a fracture’s stiffness and depth, can reveal its potential fluid
flow rate, which can be used to predict flow path and evaluate the
hydraulic integrity of a site.
Remote predictions of
in fractures now possible
It has been difficult to create a universal way to evaluate fractures
because of the wide range of sizes, from microns to kilometers. In addi-
tion, fractures in the Earth are dynamic and subject to frequent changes
in stress, chemistry and fluid pressures, says Pyrak-Nolte, who led the
“When you look at all of these very different fractures, it seems like
each would be different and the rates at which fluid could flow through
them would be different,” she says. “Now we have found the single under-
lying physical principle that explains them all.”
The team also showed that high-frequency wave measurement, in
which seismic waves are used like radar to provide the basic dimensions
of a fracture, can be used to obtain the stiffness of a fracture. When this
technology is paired with the new scaling law, it allows for a remote scan
of a fracture to reveal the potential fluid flow at a particular site and also
to monitor potential changes in fluid flow at a site over time, Pyrak-Nolte
The findings are detailed in a paper in the journal Nature
Communications that is currently available online.
“Through decades of study of fractures and related science, we were
able to pull together all of the threads and see the pattern in the tapes-
try,” says Pyrak-Nolte, who also has courtesy appointments in the Lyles
School of Civil Engineering and the Department of Earth, Atmospheric,
and Planetary Sciences. “I think this is a good example of the importance
of long-term funding. Without the long-term support of the Department
of Energy, I wouldn’t have had the steady exposure in this area necessary
to arrive at the creation of a very useful and practical tool.”
In the future, the team hopes to further validate the methods at a field
site with known fractures and to pursue the creation of a similar frame-
work for the behavior of net works of fractures.
— Elizabeth K. Gardner
A graph of the scaling relationship between fluid flow and fracture
stiffness is shown. The shape of the symbol indicates the fracture
length scale from 0.0625 meter (circles) to 1 meter (triangle) and the
colors correspond to different apertures.
(Image courtesy of Laura Pyrak-Nolte)