New Fluid Could Revolutionize Reservoir Stimulation
PNNL's new geothermal stimulation fluid could make geothermal power production more environmentally friendly. The nontoxic fluid is designed to be used in enhanced geothermal systems, where fluids are injected into drilled wells that lead to underground geothermal reservoirs. The fluid expands when exposed to carbon dioxide underground, which creates tiny, but deep cracks in otherwise impermeable rock.
Borrowing from well-understood polymers used in medicine, researchers at PNNL are developing a new stimulation fluid that could be a boon to tapping both geothermal energy and unconventional oil and gas reserves. The fluid is a solution of water and 1% non-toxic polyallylamine that could lead to more effective, environmentally friendly hydraulic fracturing applications.
PNNL’s unique fluid would be pumped underground into a reservoir and then followed by injection of carbon dioxide. The polyallylamine and carbon dioxide link together, forming a hydrogel that dramatically expands the fluid volume by up to 2.5 times. The swelling gel pushes against the rocks, causing existing cracks to expand, while also creating new ones. The expanding fluid is expected to reduce the amount of water and time needed to stimulate and open reservoir fractures for energy recovery by 50%.
Conventional hydraulic fracturing consists of drilling a well and using water, chemicals, and other additives injected at high pressure to create cracks or fissures in subterranean reservoirs. Hydraulic fracturing fluids are designed to create as many fractures as possible in the targeted rock, and contain proppants—or sand—that hold the fissures open so the desired oil, gas, or geothermal energy resource can be extracted and collected. PNNL’s environmentally friendly fluid has the potential to create more and larger fractures using less water, enabling enhanced recovery of subsurface resources.