Surfactants extract embedded oil from high-salt reservoirs

Researchers in the US have developed surfactants that can help extract up to 70 per cent of the oil still embedded in high-salt oil reservoirs.

With controversy surrounding advance recovery methods such as hydraulic fracturing — or fracking — Jeff Harwell, Ben Shiau and Bruce Roberts from the University of Oklahoma’s (OU) Institute for Applied Surfactant Research have formulated an environmentally sound compound that increases oil flow in previously pumped reservoirs.

By using a surfactant that decreases the surface tension, oil is released from the rock so it can move with the injected water and be pushed to the production wells.

Secondary recovery methods, such as water flooding and fracking, are used to recover oil left behind by previously pumped reservoirs. The methods drive trapped oil toward the drill hole, but when the injected water reaches the production wells, most of the oil remains trapped in the rock.

‘Our surfactants replace the crude oil within the rock with harmless compounds such as brine that maintain the integrity of the rock formation,’ Harwell said in a statement. ‘The ingredients we use are in things that people use every day to bathe, brush their teeth and wash their car. The chemicals we inject are not near the threat or hazard level of the compounds in the oil we are removing from the reservoir.’

The OU team’s surfactant increases flooding efficiency even at concentrated levels of salinity.

‘Most research focuses on salinity around a three to five per cent threshold,’ Harwell said. ‘We recently successfully formulated a surfactant system for up to 26 per cent salinity.’

The OU research currently is focused on oil in Oklahoma’s Pennsylvanian aged sands that span much of the state and typically contain high concentrations of salt, ranging from 15 to 25 per cent.

‘That means there is a huge area with a tremendous amount of oil trapped in these formations,’ Harwell said. ‘The Oklahoma Geological Survey estimates there were 84 billion barrels of original oil in these reservoirs and we have only extracted about 15 billion.’

The research team has successfully tested its surfactant formulations in several single-well operations and is now moving to small, multiple-well testing.

If successful, the surfactant would enable small oil producers to recover more oil efficiently and cost-effectively, while leaving the formations environmentally sound.