Focus on new faculty: Hiroki Sone, experiments in rock mechanics
Hiroki Sone still remembers his first encounter with the geosciences in elementary school in Houston, Texas—ground zero for the American oil and gas industry.
“Maybe it’s a Texas thing, but I remember in elementary school I learned what crude oil is,” Sone says. “Maybe that’s just because it was in Houston. But I also remember when I heard this word ‘sandstone’ in elementary school; it was weird because sand is sand and I wondered how it could be a stone. Somehow, I had this question when I was in elementary school, so probably I had interest in these things even then.”
After a three-year postdoctoral appointment at the German Research Centre for Geosciences in Potsdam, Sone joined the college as an assistant professor of civil and environmental engineering and geological engineering in fall 2015. It will be Sone’s first appointment in an engineering department, and he’s excited to bring his expertise in rock mechanics to UW-Madison.
Sone’s early interest in the geosciences wasn’t fully realized until his college years in Kyoto, Japan, where his pursuit of physics dovetailed with his interest in the physical world around him and the research of an early mentor.
While at Kyoto, where he completed bachelor's and master's degrees in geology and mineralogy, Sone studied the mechanics of a thrust fault in Taiwan linked to hazardous earthquakes. Later, at Stanford University, Sone continued his research on fault mechanics as a PhD student, but soon he and his advisor began looking focusing their research efforts elsewhere.
At Stanford, Sone began doing lab work on shale gas reservoir rocks. He was characterizing their basic qualities, in particular a quality called “creep deformation.”
Creep deformation is the very slow deformation of rocks such as shale when they are placed under a sustained load. Sone’s lab work on the shale gas reservoirs’ creep deformation characteristics helped identify reservoirs amenable to the extraction method of hydraulic fracturing—better known as “fracking.”
“Rocks flow to some extent,” Sone says. “When they flow, it changes the stress in the earth—stress being the force that’s inside the rocks. When that condition changes, sometimes it favors fracking and sometimes it’s difficult to make fracking happen.”
Understanding how likely shale rocks are to flow gives researchers and companies an idea of what force or stress state a gas reservoir is in, which Sone says influences the outcome of fracking.
“These are called ‘unconventional reservoirs’ because we knew that the gas was there, but we didn’t know how to get it out,” Sone says. “With conventional reservoirs, you poke a hole and oil just comes out, but that doesn’t happen with these shale gas reservoirs because the fluids don’t flow as freely as in conventional reservoirs.”
To allow the fluid gas to flow, companies must fracture the shale that contains it.
“I don’t think there is an alternative way to do that,” Sone says. “It took the industry a while to figure out how to do that.”
Sone acknowledges the less-than-stellar reputation fracking has garnered in some circles over the last several years, with critics concerned about it’s environmental impacts, both on the local and global scales. Locally, critics are concerned that the chemical-laden fluids injected to fracture the shale might contaminate ground water. Globally, concerns center on the new method’s contribution to fossil fuel-based energy systems and their link to climate change.
“I’m not necessarily for or against fracking,” Sone says. “I just really want the discussion to be healthy. That’s one of the things I want to emphasize in the classes I’ll teach, so they can discuss this matter, because energy problems are not just about the environment—they’re also economic and political. It’s just very important to be informed properly.”
This fall, Sone is teaching Geomechanics, a graduate-level course on the mechanics of large-scale geophysical features. Next spring he is offering an undergraduate course in rock mechanics, which applies similar concepts but on a smaller scale limited to rocks.
And while Sone’s research interests continue to include experimental rock mechanics and their application to both the understanding of earthquake-prone faults and of shale gas reservoirs, Sone is also beginning to explore engineering problems like that posed by nuclear waste disposal.
“When I study the slow deformation of shale rocks, which are clay-rich rocks, this directly applies to nuclear waste disposal because governments, especially in Europe, are thinking about building these repositories in clay-rich rock environments,” Sone says.
Some European governments have already selected target sites in such environments, Sone says. “I think in the U.S., since activities in the Yucca Mountain was slowed down, they’re starting to look for other candidates, and shales are one of the types of rocks they’re looking at. My research related to natural gas can actually be directly transferred to such settings.”
Because clay-rich shales are less porous and have the ability to flow slightly, Sone says they have the ability to self-seal if fractured. Those same rocks also tend to adsorb excess moisture and contaminants that might otherwise leak through other rock types.
Sone also plans to be involved in European-led research on reducing fracking’s environmental footprint, and also apply the mechanics of flowing rocks to studies of earthquake statistics. His experimental rock mechanics lab on campus will employ a post-doc and other graduate students. A large portion of the new lab's start-up funding was provided by a donor. Sone used the donation to purchase a new rock deformation apparatus.
"Modern rock mechanics equipment is quite expensive, but I felt the need to introduce one such piece of equipment because I needed to perform long, stable experiments to study creep behavior of rocks, and it also significantly reduces the time for students to learn how to use the specialized equipment," Sone says.
“I’m excited to be at UW-Madison,” Sone adds, “I’m among people and environment I was never exposed to before.”