Skip to main content
eScholarship
Open Access Publications from the University of California

UC Berkeley

UC Berkeley Electronic Theses and Dissertations bannerUC Berkeley

Mineralization of carbon dioxide sequestered in volcanogenic sandstone reservoir rocks

Abstract

We proposed to use volcanogenic sandstones for CO2 sequestration. Such sandstones with a relatively high percentage of volcanic rock fragments (VRF) could be a promising target for CO2 sequestration in that they have a sufficient percentage of reactive minerals to allow substantial mineralization of injected scCO2, which provides the most secure form of CO2 storage, but can also be porous and permeable enough to allow injection at acceptable rates. The limitation in using volcanogenic sandstones as CO2 reservoir rocks is that porosity and permeability tend to decrease with increase of volcanic rock fragments (VRF) and with the length and complexity of the diagenetic history. Decreased porosity limits the rate at which CO2 can be injected. We evaluated these tradeoffs to assess the feasibility of using volcanogenic sandstone to achieve highly secure CO2 storage. Using relationships between VRF percent, porosity and permeability from available geological data, the reactive transport code TOUGHREACT was used to estimate the rate and extent of CO2 mineralization over 1000 years, and the trade-off between higher reactivity and lower porosity and permeability. For the parameter set that we believe is defensible, the optimal VRF percent for the largest amount of mineralized CO2 is around 10-20%. The results show that as much as 80% CO2 mineralization could occur in 1000 years and still allow sufficient injectivity so that ca. 1 megaton of CO2 can be injected per year per well. The key to estimating how much CO2 can be injected and mineralized is the relationship between permeability (or injectivity), reactive mineral content, mineral dissolution rates and reactive surface areas. We have sampled examples of volcanogenic sandstones from the Miocene Etchegoin Formation, central California to examine these parameters. Characterizations of these samples by SEM, XRF and XRD show that they are very rich in reactive minerals with around 32% plagioclase, 10% orthopyroxene, 2% clinopyroxene, and 1% ilmenite. Porosities range from 10% to 20%, and permeabilities range from 10 mD to 1000 mD. Batch experiments are also conducted to measure dissolution rates of one of the common minerals in volcanic sandstones, i.e. chlorite. Results show that the released Mg from chlorite in such sandstones could provide enough cations to potentially mineralize about half the stored CO2 in the pore space within 1000 years. The last chapter presents an extension of the TOUGHREACT code to include carbon 13 isotope into reactive transport modeling. 13C isotope proves to be a great tracer for monitering subsurface flow of CO2.

Main Content
For improved accessibility of PDF content, download the file to your device.
Current View