Extracting oil from the Earth in ways that minimize environmental harm is a challenging task. Methods like hydraulic fracturing require the injection of fluids into rock formations to create pressure for oil and natural gas to flow out. However, this process often causes air pollution and water contamination due to the use of toxic chemicals.  

As researchers continue finding new ways to extract oil, distinguished professor in biomedical and chemical engineering, Radhakrishna (Suresh) Sureshkumar has made significant progress in research involving fluid mechanics and soft materials. Supported by the Petroleum Research Fund (PRF) from the American Chemical Society (ACS), he’s exploring the structure and flow behavior (rheology) of polymeric solutions that offer promise in efficient oil extraction.  

“The ACS seeks to promote fundamental petroleum research and my research has received funding from the PRF in the past. They awarded me my very first grant during my tenure at Washington University and I’m looking forward to continuing research supported by the agency” says Sureshkumar.  

With the fund, he and graduate student Senyuan Liu have been analyzing a group of molecules known as copolymers, which fall under the category of polymers, large molecules made of long, repeating chains of smaller molecules. Copolymers are made up of multiple polymers that possess different properties and are chemically bonded together. Most notably, copolymers consist of different blocks that have varying affinities to water. Some blocks are hydrophilic, meaning they like water and others are hydrophobic, which means they like oil. 

Oil and water are known to not mix. However, there is a way they can be made compatible by using a substance called a surfactant. When a surfactant is added to water and oil, it creates an emulsion, the mixture of two or more liquids that don’t naturally mix. Using computational modeling, Sureshkumar and Liu are exploring the thermodynamic patterns underlying the assembly of copolymers in aqueous solutions. Further, they are investigating how molecular assemblies deform under flow conditions. 

“Detergent is a good example of a surfactant. Dirt is oil-like material and when washing clothes, you add detergent to the washing machine because oil and water are not thermodynamically compatible,” Sureshkumar explains. “A surfactant has two parts to its molecular structure: one part is hydrophilic, the other is hydrophobic. So, when water, oil, and detergent are put together, it creates an emulsion allowing water and oil to mix.” 

He and Liu have also been studying how copolymers self-assemble into various shapes such as spheres, cylinders, disks, and vesicles when they’re in water. Since copolymers possess different properties, some being hydrophilic and some hydrophobic, the oil-loving molecules avoid contact with water, leading to self-assembly and the formation of different shapes. 

To further explore fluid dynamics, Sureshkumar and Liu have now developed technology that uses molecular dynamics simulations to study self-assembling molecules and their applications in oil extraction. They experiment with how these shapes self-assemble in different environments and have recently published a paper about their work. 

“The molecular simulation we’ve created contains water and we can adjust the temperature and pressure as well. Adding individual polymer molecules, moving them around and tracking the process allows us to see how the invisible hand of thermodynamics causes them to self-assemble into various shapes,” Sureshkumar says. “We can see how these types of polymers will react in a natural environment, an engineered environment, or even the human body using this simulation.” 

Studying how structures organize into different shapes and the thermodynamic mechanisms behind the creation of polymer structures is crucial, according to Sureshkumar. This research enables new ways to understand how to extract petroleum from the Earth and he believes the oil and natural gas industry can benefit from numerous applications of this research. It can also help unravel the mysteries of nature and answer questions regarding what causes polymers to self-assemble in the first place. 

“Why would nature take a bunch of molecules and assemble them into a particular shape? This is a fundamental question,” he says. “Gaining an understanding of how nature creates nanostructures, we can engineer nanoscopic assemblies of molecules in a smart way and design better technologies to benefit society. The current grant from the Petroleum Research Fund helps us continue such fundamental explorations.”