The emission of carbon dioxide (CO2) and the accumulation of this green-house gas in the atmosphere, leading to global warming, is considered one of the most serious threats mankind is facing. CO2 emissions result from the combustion of oil and gas, for example by cars and industries. Many new cars are now electric, and industries are looking for green solutions to replace their gas combustion and reduce their production of carbon dioxide, but the development is far too slow. According to the Intergovernmental Panel for Climate Change (IPCC), capturing the carbon dioxide at the source and storing it in abandoned oil and gas reservoirs is considered one of the most viable solutions. The technology is already quite advanced with on-going full-scale industrial pilot test plants like Longship One of the challenges that needs to be better understood, is the tendency of clogging by salt formation during injection into the reservoir, including how it can be mitigated. The huge, abandoned oil and gas reservoirs are porous rocks filled with brine (salt water), and when injecting CO2, water is absorbed by the dry gas, and the brine salt concentration increases, leading to salt precipitation. This solidification might clog the porous rock and reduce the amount of CO2 that can be stored in a specific reservoir. Through advanced X-ray imaging methods like quantitative computed tomography (CT) at high temperature and pressure, combined with thermodynamical measurements, the SaltyPore project headed by Dr. Elvia Chavez aims to reach a better scientific understanding of this specific phenomenon, as a key applied example of phase transitions in porous media. In collaboration with in-operando imaging beamlines at the synchrotron ESRF, national X-ray and CO2 expertise, and industry through the Centre for Environment-Friendly Energy Research (FME) of NCCS led by SINTEF, SaltyPore aims to indirectly contribute also to the technical solutions to this challenge.
CO2 Capture and Storage (CCS) in abandoned oil reservoirs is considered a promising solution to mitigate climate change. A known problem of CCS is salt precipitation, which can severely reduce CO2 injectivity by pore clogging. NaCl is abundant on Earth, and of huge importance to climate and life. Despite perhaps appearing simplistic, the nucleation of salt is a nontrivial problem in itself – and with the added complications of being out of thermodynamical equilibrium, embedded in porous rocks, and under reservoir conditions, the scientific case is highly complex.
The young research talent Dr. Elvia Chavez is a researcher at NTNU, having extensive experience with CO2 interactions, thermodynamics, and X-ray physics. She has gathered an exceptional international team covering nucleation, physics, thermodynamics and CCS – perfectly pitched to reach a deeper understanding of the salt clogging phenomenon.
CO2/brine measurements of wetting and solubility in and out of equilibrium, using state-of-the-art imaging and microfluidics are the principal methods. Whilst porous materials can be studied with high resolution, observing phase fronts and mineral nucleation inside the pores remains challenging. We will explore systematic contrast variation offered by neutrons and specialized CT to mitigate this limitation. We expect to be able to quantitatively characterize microscopic salt particles under realistic reservoir conditions, allowing existing theories to be challenged.
In summary, SaltyPore aims for a better understanding of salt precipitation from brine during CCS injection, facilitated by laboratory experiments with CO2 in contact with brine under reservoir conditions. The societal relevance is high, both as applied to CCS, but also fundamentally with the many strong links between CO2, salt and the environment. Being a subject of profound scientific and societal importance, CCS and salt precipitation is also well suited for dissemination and public outreach.