Microscopic saltwater droplets enhance oil recovery

Rice University researchers have found microscopic saltwater droplets emulsify crude oil when each has the right composition, which can enhance oil recovery.

By Mike Williams March 5, 2020

Scientists at Rice University’s Brown School of Engineering show that microscopic saltwater droplets emulsify crude oil when each has the right composition. Understanding how they combine is important to enhanced oil recovery.

Rice chemical and biological engineer Sibani Lisa Biswal and her colleagues went to great lengths to characterize the three elements most important to oil recovery: rock, water and the crude itself.

They confirmed wells are more productive when water with the right salt concentration is carefully matched to both the oil and the rock, carbonate or sandstone formation. If the low-salinity brine can create emulsion droplets in a specific crude, the brine appears to also alter the wettability of the rock. The wettability determines how easily the rock will release oil.

Co-lead author Jin Song said the first hints of seawater’s effect came from wells in the North Sea. “Oil companies found that when they injected seawater, which has relatively low salinity, oil recovery was surprisingly good,” he said.

Even with that understanding, he said research has been limited. “Usually in the oil and gas industry, when they’re looking into low-salinity water, they tend to focus on the effect of the brine and ignore the effect of the oil,” said Song, who earned his Ph.D. at Rice and is now a researcher at Shell.

Rice University engineers studied the mechanism that allows low-salinity brine to emulsify with oil. The effect could aid enhanced oil recovery from reservoirs. Clockwise from left: Wenhua Guo, George Hirasaki, Jin Song, Sibani Lisa Biswal and Maura Puerto. Courtesy: Rice University[/caption]

The images revealed droplets varying in size from 70 to just over 700 nanometers. Biswal said chemical surfactants — aka soap — are also good at loosening oil in a reservoir, but are prohibitively expensive. “You can change the salt concentration to modify the composition of the brine and get the same effect as in including the detergent,” she said. “So it’s basically a low-cost technique trying to achieve the same goal as detergent.”

Original content can be found at Oil and Gas Engineering.

Author Bio: Mike Williams is a senior media relations specialist in Rice University's Office of Public Affairs.