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CHEMICAL engineers at the University of Pittsburgh, US, have launched an ambitious project to produce an economical CO₂ thickener that they say could “significantly” boost the world’s accessible oil reserves.

The research, supported by a US$1.3m grant from the US Department of Energy, is looking to improve the so-called water-alternating-gas (WAG) method of gas extraction, where oil is pushed from porous reservoirs of rock deep underground. As the name suggests, alternating bursts of water and CO₂ are pumped through the stone, carrying trapped hydrocarbons towards the well as they go.

However, the low viscosity of the CO₂ limits the amount of oil it carries with it, as it ‘fingers’ through the liquid rather than pushing it along. This significantly reduces the amount of oil that can be extracted from a given reservoir, leaving much of it stranded underground.

In the late 90s, however, Pittsburgh researchers found that additives could thicken the CO₂ at low concentrations, dramatically improving its ability to push out the oil. Unfortunately, the additives proved to be highly expensive, making it impractical for use on a commercial scale.

“The thickeners we developed years ago were too expensive for wide use,” says engineering professor Eric Beckman. “So, in this proposal, we’re looking at designing candidates that can do the job at a reasonable cost.”

The team aims to develop a thickener able to increase the viscosity of pure CO₂ by a factor of 100, improving on its previous designs. Alongside this, it hopes to keep the cost down to just US$7/lb (US$15.40/kg).

“An affordable CO₂ thickener would represent a transformational advance in enhanced oil recovery,” says chemical engineering professor Robert Enick. “More than 90% of CO₂ injection projects in the US employ the WAG method to hinder the fingering of the CO₂.”

“It’s clear there exists a very wide market for this type of CO₂ thickener,” adds Beckman. “It’s been long recognised as a game-changing transformative technology because it has the potential to increase oil recovery while eliminating water injection altogether.”