In March this year, students from the University of Texas Jackson School of Geosciences presented research at the annual meeting of the UT-Austin EDGER Forum, an industry consortium that sponsors education and research in exploration geophysics. Research carried out by the group spans laboratory experiments, numerical simulations and field data analysis, a combination that is virtually unheard of among geophysics consortia and frequently leads to applications in industry.
We met with students from each of the consortium’s three research tracks: numerical simulations, theoretical rock physics and laboratory experiments. Michael McCann, Omar Alamoudi and Ziqi Jin are members of Dr. Nicola Tisato’s rock physics research group and conduct research using the Jackson School’s new Rock Deformation Lab. EDGER Forum Co-Investigator, Nicola Tisato, is assistant professor at the Department of Geological Sciences, Jackson School of Geosciences.
As an undergraduate geology student at Purdue, Michael McCann realized he really liked the math side of his field, so for his master’s he decided to switch to geophysics. He chose UT because the Jackson School is ranked number one in geological sciences and because the degree offered excellent job prospects.
Michael graduated in May this year with a master’s in geophysics. During his time here, Michael worked as a research assistant conducting experiments in Nicola Tisato’s rock deformation lab. The research he conducted here is cutting edge science and has direct industry applications.
“In experimental rock physics what we do is study the properties of rocks,” explains Michael. “In the past, people made high frequency measurements using, for example, ultrasound, because it’s quick and easy.”
Michael’s approach, however, was different and instead focused on making measurements at much lower frequencies, like seismic waves.
“What I actually do is measure fluids, in particular fracking fluids,” he says, “people have made low frequency measurements on rocks but no one’s ever done this on fluids.”
The reason Michael studies fracking fluids is so that companies can use seismic waves to estimate the size and permeability of fractures created during hydraulic fracturing, or fracking. During fracking, special fluids are pumped into a hydrocarbon reservoir at a high enough pressure to crack the surrounding rock, allowing oil and gas trapped in the rock’s pores to channel into the oil well before being extracted. Being able to accurately estimate the size of fractures increases efficiency.
To be able to ‘see’ underground using seismic waves it is necessary to understand how these waves change as they pass through certain materials, in this case fracking fluid. To do this, Michael and his colleagues in Dr. Tisato’s research group designed and built a machine specifically to conduct low frequency measurements on fluids.
“The machine compresses and relaxes the fluid that’s inside at very low frequencies, very slowly, over about ten hours,” he explains. “What we’re looking for is to measure the pressure change and how much it deforms.”
The group found that there is a small delay from when a sample is compressed to when it actually shrinks. By measuring that delay, Michael says he is able to calculate attenuation, in other words how much energy a seismic wave will lose when it passes through that fluid at a particular frequency.
“We are learning that the high frequency values people have been using in the past could be significantly different from measurements at low frequency,” adds Michael. “That will ultimately help create more accurate rock physics models to solve other problems.”
Michael says that the group’s ability to develop this machine and conduct these experiments owes a great deal to the resources they have access to through the UT EDGER Forum. His time with the UT EDGER Forum, however, has offered more than just access to high tech equipment. He has also gained unique insights into how the industry works and their research interests. Now that he’s graduated, he knows it’s time to think about what he’s learned during his master’s before deciding on his next step.
“I’d definitely like to stay in geosciences,” he says, “and maybe work in industry.”
Before coming to UT, Omar Alamoudi was an industry scientist working in his native Saudi Arabia. He chose to study a PhD at UT because the world class facilities available at the Jackson School were a unique opportunity to advance his career.
“UT and Dr. Tisato have facilities, expertise and capabilities in experimental rock physics I’d never seen anywhere else,” he adds. “When I finally visited, the enthusiasm of the group really was a convincing factor in my decision to do a PhD at UT.”
Another unexpected benefit of working with Dr. Tisato’s research group was discovering their specialization with micro-CT imaging of rocks, which has formed the main focus of Omar’s research. This technique utilizes X-ray sources and detectors to study the interiors of rocks, not unlike how a doctor examines a patient with a suspected broken bone.
“When doctors look at CT images of a patient they can pinpoint breakages in bones and assess how they will heal,” he says. “In my case I actually want to break the rocks, because when they break, channels are created through which fluids can flow.”
A common application for rock fracturing is of course oil extraction.
“It’s important to understand that oil in the ground is not found in great underground lakes,” he explains, “but rather it is stored in very small voids, or pores, within rocks.”
When rocks fracture, channels are created which allow fluids to flow much faster through the rock than they would through its pores. The same is true for ground water and any other fluid.
Omar says that although their group focuses on oil reservoirs, the applications of their work are by no means limited to oil and gas.
“Hydrocarbons are only a particular choice of material,” he says. “It could also be carbon dioxide, for example. Storing carbon dioxide underground is becoming quite common and will be increasingly important for environmental reasons.”
Omar explains that whether storing carbon dioxide or nuclear waste, it is important to understand how rocks react to pressure and stress to ensure such operations are conducted safely.
“If the rock fails it could lead to catastrophic disaster,” he says, “you could inadvertently contaminate drinking water from an aquifer. That’s why this work is so important.”
The Jackson School’s rock deformation lab allows Omar to study how rocks behave in the extreme conditions where they are found deep underground. At the same time, being part of the UT EDGER Forum offers important industry perspective and a breadth of knowledge that means his research efforts have much greater impact.
“The EDGER Forum integrates three important applications of geophysics really well,” he says. “In such an environment, doing experimental work doesn’t leave me isolated, rather it integrates me into the entire workflow and I think that’s very valuable and important.”
Besides working on his PhD, much of Omar’s life is now focused on his ten-month old child.
“I used to enjoy travel and photography,” he says, “but with grad school and having a kid it’s very challenging to dedicate any time to either of those hobbies.”
Still, now that they are becoming accustomed to the demands of parenthood, he and his wife are hoping that at least one hobby is making a return.
“We like taking pictures of him, so I guess photography in the house is making a comeback!”
Ziqi Jin is a visiting PhD student from the China University of Petroleum-Beijing. He is currently conducting experiments with Nicola Tisato at the Jackson School’s new rock deformation laboratory. Ziqi says that coming to UT has been an enormously rewarding experience.
“The lab measurements I perform here I have never done before,” he says. “Working with Nicola and the UT EDGER Forum has helped me study better geophysics and learn many new techniques. I’ve really learned a lot here.”
The main focus of Ziqi’s research is measuring how seismic waves attenuate as they pass through rocks containing fluids and gases. Seismic attenuation is the loss of energy by seismic waves as they move through a medium, for example the Earth’s interior. What’s particularly interesting about Ziqi’s research is the level of detail in his study. As a seismic wave passes through liquid saturated rock, such as that found in an oil or water reservoir, the seismic wave creates pressure changes in the liquids found within the rock’s pores. Bubbles in the liquid shrink and expand, leaking energy in the form of heat.
Scientists have long theorized the effect of microscopic bubbles on seismic waves but it wasn’t until recent pioneering work by Dr. Tisato that the effect was definitively observed. Collaborating with Dr. Tisato has been a good match for Ziqi because they both work on the same theoretical models.
“Dr. Tisato has made some important contributions to this field,” explains Ziqi, “I go through his work about a kind of attenuation called wave-induced-gas-exsolution-dissolution (WIGED). We set up experiments to measure attenuation in bubbly water to prove the WIGED theory. I also match these results with my previous work modeling attenuated seismic waves and combine these to estimate attenuation.”
Combined with the right theoretical understanding, these results can be used to infer what the seismic waves ‘see’ underground. The technique is used to create 3D seismic interpretations of subsurface oil and gas reservoirs, which in turn is used by exploration companies to find reservoirs.
Working at UT has been invaluable for Ziqi because it has given him access to large seismic datasets through the UT EDGER Forum and offered unique opportunities to test his ideas directly with the Jackson School’s rock deformation lab.
“This is very important because I learn how to set up experiments and do measurements in the lab,” says Ziqi. “With the rock deformation lab here at the Jackson School I am setting up my experiments and can make measurements to see how they fit with my theory.”
Remarkably, Ziqi is the third generation of geoscientists in his family.
“I grew up in a family who are into geophysics,” he explains, “my mother and father worked in the oil industry, and so did my grandparents.”
Following in his family’s footsteps made sense to Ziqi. He was always curious about what goes on underground and decided he wanted to work in a field connected to his family’s history. When the time came to choose a college major, geophysics was the natural choice.
Ziqi has enjoyed his time so far at UT, and not just for the opportunity to pursue his research with prominent experts in world leading facilities. Becoming immersed in a culture quite different to his own has been reward in itself.
“UT is a very nice place!” he says. “The campus and buildings are very beautiful and people in Texas are very kind.”