Energy Geosciences Division Research Scientist Julia Correa has some advice to share: Be curious, and take chances.
Following her own guidance, Correa has studied geophysics in locations and environments all around the world, from the Atlantic Ocean to Egypt, Australia, Utah, North Dakota, and more.
“This was exactly what I always wanted to do,” Correa said. “Experience an adventure.”
And science is often the ultimate adventure. Correa has dedicated her career to bringing Earth’s deep, invisible subsurface to light using seismic monitoring, which records movements and vibrations underground. She mainly uses fiber-optic sensing: a method of seismic monitoring that obtains information about geologic systems thousands of feet deep, such as their characteristics (for example, rock type), and how they move or change–all from aboveground. This technology can be a game-changer for developing and accelerating geologic energy solutions, painting a picture of where these innovations can be implemented and how they might impact Earth’s surface.
Correa came to EESA as a Postdoc in 2019 to continue living out her adventure. Now a Research Scientist leading her own team, she is studying how to make this sensing technology cost effective for geological carbon storage and geothermal energy systems.
From college to the Atlantic
“Since I was a kid, I have always been really curious about everything,” Correa said. “How things work, why things happen. Being curious is critical to being a scientist.”
Correa driving the research vessel she worked on to conduct seismic surveys and monitoring of geology deep beneath the ocean. Courtesy of Julia Correa.
Correa’s innate curiosity and interest in Earth sciences led her to pursue a Bachelor’s degree in geophysics at Universidade Federal Fluminense in Rio de Janeiro, Brazil, near her hometown. After graduation, she worked as a geophysicist for Schlumberger, a geophysical services company. Correa lived aboard a research vessel, where she and her team collected data that helped them understand the structure and movement of Earth’s crust deep below the ocean. They were monitoring how reservoirs change due to oil and gas extraction.
“My first trip was two months on the boat, off the coast of West Africa’s Cape Verde, in the absolute middle of nowhere,” Correa described. “You couldn’t see any land. And I worked 12-hour days. It was a very specific lifestyle–and I liked it.”
The vessel carried six-mile long streamers with hydrophones, devices that monitor sound waves throughout the ocean. The boat also carried air guns that would generate a bubble in the ocean, creating waves that travel through the ocean and interact with geologic structures. Different structures interact differently with the waves created by the air gun, each sending back signature waves to the hydrophones, which helps scientists identify and monitor changes in geology deep beneath the ocean.
To explain what they were listening for, Correa knocked on the table where she was seated, and then her chair. “The sound of a knock on the table sounds different than the sound of a knock on the chair, meaning that waves propagate differently in different materials,” she said.
This is the principle of what her team was collecting. Because different types of materials have different densities, they reflect acoustic waves at different velocities that are recorded at the surface with special microphones (hydrophones in water, geophones on land). The recorded waves can be linked to specific structures, like a certain rock type. By analyzing these wave velocities and their travel time, they can infer the characteristics and depths of structures. This is how they paint a picture of the subsurface.
A new application of seismic monitoring: fiber-optic sensing
After working on the research vessel, Correa was ready for a new challenge, a new application of seismic monitoring, and an on-shore landing. She traveled to Western Australia to pursue a PhD at Curtin University working on the Otway project, which studies how to store carbon dioxide safely in the subsurface.
Correa showing the blue cord and the tiny fibers that make up fiber-optic sensing technology. The cord protects the fibers, which collect the seismic data. Photo credit: Jeremy Snyder
Geologic carbon storage is a technique that stores carbon dioxide deep underground in rocks. To study how to do this safely and effectively on a large scale, fiber-optic cables can be important monitoring tools for informing scientists how CO2 injection could affect the subsurface.
Fiber-optic sensing is a relatively new method for recording seismic waves, comparable to the hydrophones and geophones, but collects the same type of data: seismic waves that help scientists monitor and identify what’s deep below Earth’s surface. The difference, however, is that in fiber-optic sensing, light pulses are sent down hundreds-of-feet-long cables. By monitoring the changes in the backscatter of the light as it travels through the fiber-optic cable and experiences different movements, interacts with incoming waves, and interacts with various structures, scientists can identify and track the movement of rocks and fluids underground.
“Before we can inject fluid into the subsurface,” Correa explained, “we have to know what’s there, so we record a baseline survey. After we inject fluid underground, we want to know how this affects the subsurface. This information captured from fiber-optic sensing is used to monitor the movement of the injected CO2, as well as any potential issues, such as CO2 leakage and seismicity. Fiber-optic sensing can be helpful to answering all of these questions, tracking the location and movement of the CO2, and driving this solution forward.”
Correa with a surface orbital vibrator, a machine that generates vibration patterns. These vibrations interact with the light running through fiber-optic sensing cords to help scientists understand how movement underground affects geologic systems. Photo Credit: Jeremy Snyder
Correa focused her PhD and Berkeley Lab research specifically on developing cost-effective fiber optic sensing applied to long-term monitoring. Once fiber optic sensing cables are installed, they can stay in place for continuous data collection, eliminating setup costs and reducing the labor needed for maintenance and replacement. Correa works on optimizing the fiber optic sensing for long-term placement, and also studies how to develop the technology so it can collect and transmit data straight to the laptops of researchers, without the need to collect data in the field.
As she reflected on shifting from collecting seismic data from geologic structures in the ocean to land, Correa expressed the importance of taking chances as a scientist–how, especially as an early-career researcher, no one knows everything that exists in their field or related fields.
“Sometimes, opportunities are presented to you, and you have to be able to identify them and take advantage of them. And certain opportunities can be life-changing.”
From “wiggles” to images of the subsurface
Correa came to Berkeley Lab to continue studying seismic monitoring as a Postdoctoral Researcher. Now a Research Scientist, she studies and uses fiber-optic sensing for many different applications, including geothermal energy. She is particularly interested in studying geological systems in the long term to understand how they continuously respond to and are affected by artificial seismicity.
Correa works closely with other geophysicists, including David Alumbaugh and Yves Guglielmi, and collaborates on geothermal projects such as Utah FORGE. This field-scale effort allows scientists to explore developing and monitoring enhanced geothermal systems, which work by injecting fluid into drilled holes in rock deep underground to artificially create areas where geothermal energy can be produced. Just as it is in geologic carbon storage, fiber-optic cables are critical to monitoring where the fluid goes and any impacts it causes underground.
“We have a few field sites where we study and use seismic monitoring, like the Utah FORGE site,” Correa said. “I’m in the field a lot to help collect data, but a lot of my time is also spent processing it. The data we receive is essentially a bunch of wiggles. It’s my job to take all that and turn it into a clear image of the subsurface.”
The importance of exploring the unknown
Correa’s journey from a curious student to a geophysicist at Berkeley Lab is a testament to the power of asking questions and taking chances. Her work advancing our understanding of geologic systems and creating more clear images of the subsurface has contributed to developing innovative solutions to energy challenges. Whether aboard research vessels, at field sites, or closer to home, Correa embraces science as the ultimate adventure, reminding us that the courage to explore the unknown is often where great innovation can happen.
