New fluid may be a boon for enhanced geothermal power systems

April 17, 2015 0 By Amanda Giasson

A new nontoxic liquid may tap into unreachable geothermal areas.

According to a paper recently published in Green Chemistry, a new reservoir stimulation fluid features a polymer that can not only expand the volume of the fluid and create minuscule cracks in deep underground rocks, which increases geothermal power production and may be beneficial to enhanced geothermal systems, but it is environmentally friendly, too.

More homes in America could be powered by the Earth’s natural underground renewable energy source.

This would be made possible with enhanced geothermal systems, which are systems that pump fluids beneath the Earth’s surface, a process known as “reservoir stimulation.” These systems are used to tap into geothermal hot spots that would be otherwise unreachable. In other words, it allows for power generation where traditional geothermal does not work.

However, what makes this new reservoir stimulation fluid notable is it is nontoxic and is anticipated to use half as much water compared to other fluids used in enhanced systems. Thus, it could substantially lower the amount of water used, as well as the expense of enhanced geothermal systems.

Carlos Fernandez, the lead fluid developer and a chemist at the U.S. Department of Energy’s (DOE) Pacific Northwest National Laboratory (PNNL), explained that the “new fluid can make enhanced geothermal power production more viable.” Fernandez added that though the team of researcher “initially designed the fluid for geothermal energy, it could also make unconventional oil and gas recovery more environmentally friendly.”

The new fluid has recycling potential and could cut the cost of enhanced geothermal power systems.

The new liquid has the potential to be recycled by injecting acid or lowering or stopping the fluid pumped underground. Either option has shown this would cause the hydrogel to break apart and return to its initial stages: carbon dioxide and the water-polyallylamine solution. After being separated, the fluids would be retrieved and used again. However, this recycling theory still needs to be tested.

PNNL’s fluid may also cut costs due to the fact that the solution is comprised of water and 1% polyallylamine. When the Polyallylamine is pumped underground and carbon dioxide is added, they quickly form a hydrogel that expands the liquid by as much as 25 times its initial size. The existing cracks within the underground rocks expand from the swelling gel and new cracks are also formed. The rapid expansion is anticipated to reduce the amount of time and water required to open an enhanced geothermal reservoir, which would lower the cost of energy generation.

That said, additional studies are required to further evaluate the effectiveness of the fluid for enhanced geothermal power systems