The National Energy Technology Laboratory (NETL), part of the U.S. Department of Energy, oversaw a project that is expected to bring important knowledge about the behavior of faults as well as other seismic activity when CO2 is injected into geological formations.
The experiment, which happened at the Mont Terri Underground Research Laboratory in Switzerland, included injecting water mixed with carbon dioxide into a fault under the surface for about five hours. This injection caused a controlled carbon-induced fault slip with the aim to establish its impact on the caprock and prevent leakage of carbon.
This experiment was the first in which a mixture of carbon and water was injected into a fault, said James Gardiner, a federal project manager and a part of the NETL Carbon Transport and Storage team.
“This project is important because it will help us understand how CO2 may affect fault activation in caprocks,” he said.
NETL is working on Carbon Capture and Storage (CCS) technologies as a cost-efficient metod to bring down emissions, address climate change and support the U.S. target of achieving net zero by mid-century.
CO2 storage reservoirs are layers of porous rock located under a layer of impermeable rock – or caprock – which serves as a seal. The caprock prevents injected carbon from escaping to the surface or moving to aquifers for drinking water.
During the injection, the researchers collected several terabytes of new geophysical field data. The data will allow for observations about fault slip and strain associated with carbon injections. The collected information will also inform about the effect that carbon-induced fault activation has on the caprocks of storage reservoirs.
The project, named “Changes in Seal Integrity Induced by CO2 Injection and Leakage in a Hydromechanically Reactivated Fault,” aims to evaluate and decrease potential risks that could be brought upon by induced seismicity due to fault slips.
Analysis of the data will provide the researchers with better understanding of fault slip processes, and will offer new information about the leakage potential of complex fault zones, thus allowing the NETL Carbon Storage Program to reach a rate of 99% storage permanence.
The data from the experiment will also offer better understanding of changes in the chemistry of water and fault mineralogy that could happen with a leakage pathway.
The experiment happened at around 1,200 feet underground at the Mont Terri Underground Research Laboratory.