CAS-Climate: EAGER – Preventing Pore Clogging by Aggregated Carbohydrate Nanocrystals during CO2 Sequestration in Deep Saline Aquifers

University Of Texas At San Antonio, San Antonio TX

Investigators

Abstract

Multiple technologies are needed to solve the climate crisis, and underground CO2 storage, with an estimated global capacity of 2,000 Gt CO2, is expected to be a required contributor. Several concerns remain regarding long-term CO2 storage security to limit leakage to the atmosphere or groundwater systems. Sequestered CO2 can seep through faults, fractures, and defective well seals; thus, a significant amount of research has been dedicated to leak monitoring, and modeling of CO2 plume flows. Once a leak is detected, remediation methods include injection shut-off, hydraulic pressure management, removal of injected CO2, biologically active barriers, and sealants or other physical barriers. However, implementation of these methods increases the cost of storage, leads to reduced CO2 capacity, and often results in closure of the injection site. This project seeks to enhance CO2 storage security by trapping the greenhouse gas in a nanocrystal stabilized foam to prevent leakage. Such an approach has never been accomplished in high salinity brines, mostly due to the excessive clogging of rock pores by aggregated nanoparticles that lead to a variety of problems including limited CO2 foam transport, pressure buildup in the reservoir, increased pressure drops, and reduced capacity. The hypothesis of this project is that carbohydrate nanocrystals with functional groups possessing high affinity towards CO2 will adsorb onto the gas/brine interface to prevent pore clogging, thus enhancing nanocrystal transport through reservoir rocks. To support this hypothesis, the project has the following specific objectives: (1) To control the CO2-philicity of carbohydrate nanocrystals by modifying their surface with thermally and chemically resistant functional groups; (2) To prevent pore clogging of sandstone rock cores by enhancing nanocrystal adsorption onto CO2/brine interfaces. The project intends to establish fundamental knowledge required to successfully sequester carbon dioxide underground in a stable foam without using any surfactants. It also seeks to create carbohydrate nanocrystals bearing CO2-philic and hydrophilic groups with adequate thermal and chemical stability to withstand harsh underground conditions. The effect of carbohydrate nanocrystal surface chemistry on CO2 foam and nanocrystal transport will be tested in environments mimicking deep saline aquifers. It is hypothesized that adsorption of the modified nanocrystals at the CO2/brine interface will enhance their transport through porous rocks; this represents a new approach for controlling nanoparticle transport through porous media. Success of this research potentially will enhance the ability of a geological site to safely trap CO2, while filling knowledge gaps in the relatively new research field of nanoparticle stabilized foams. Success on this project may create private investment opportunities in Texas and across the nation near deep saline aquifers. The forestry (cellulose) and sea food (chitin) industries of the United States could also benefit from success of this research program by expanding their potential markets. A sustainability activity that meets the education standards specified in the Texas Essential Knowledge and Skills (TEKS) will be created for middle school students. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.