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Mineralogy Control on CO2 Accessibility on Micropores of Shales for CCUS Application
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 80th EAGE Conference and Exhibition 2018, Jun 2018, Volume 2018, p.1 - 5
Abstract
Shales, which are typical caprocks overlying CO2 injection reservoirs, can provide extra storage capacity due to CO2 adsorption on the mineral surfaces of the rocks. In this case, the storage capacity is proportional to the available specific surface area (SSA). SSA of nanoporous shales is traditionally measured using N2 adsorption at 77 K. Our study shows that N2 measurement underestimates CO2-accessible SSA, due to: i) kinetic restriction of N2 in accessing micropores evidenced by low-pressure hysteresis typically found in natural porous media and ii) fluid-rock interaction, which depends on the mineralogy of the rocks.
We compare N2- and CO2-accessible SSA and pore-size distribution of shales samples with various organic (210% by wt.), carbonate (10–70% by wt.), and clay content (17–55% by wt.). Since storage capacity by sorption is dependent on gas accessibility, we recommend the measurement of SSA using CO2 for the application of CO2 storage/EOR.