Pore‐scale imaging of geological carbon dioxide storage under in situ conditions

The electrochemical reduction of carbon dioxide into carbon monoxide, hydrocarbons and formic acid has offered an interesting alternative for a sustainable energy scenario. In this context, Sn-based electrodes have attracted a great deal of attention because they present low price and toxicity, as well as high faradaic efficiency (FE) for formic acid (or formate) production at relatively low overpotentials. In this work, we investigate the role of tin oxide surfaces on Sn-based electrodes for carbon dioxide reduction into formate by means of experimental and theoretical methods. Cyclic voltammetry measurements of Sn-based electrodes, with different initial degree of oxidation, result in similar onset potentials for the CO2 reduction to formate, ca. −0.8 to −0.9 V vs. reversible hydrogen electrode (RHE), with faradaic efficiencies of about 90–92% at −1.25 V (vs. RHE). These results indicate that under in-situ conditions, the electrode surfaces might converge to very similar structures, with partially reduced or metastable Sn oxides, which serve as active sites for the CO2 reduction. The high faradaic efficiencies of the Sn electrodes brought by the etching/air exposition procedure is ascribed to the formation of a Sn oxide layer with optimized thickness, which is persistent under in situ conditions. Such oxide layer enables the CO2 “activation”, also favoring the electron transfer during the CO2 reduction reaction due to its better electric conductivity. In order to elucidate the reaction mechanism, we have performed density functional theory calculations on different slab models starting from the bulk SnO and Sn6O4(OH)4 compounds with focus on the formation of -OH groups at the water-oxide interface. We have found that the insertion of CO2 into the Sn-OH bond is thermodynamically favorable, leading to the stabilization of the tin-carbonate species, which is subsequently reduced to produce formic acid through a proton-coupled electron transfer process. The calculated potential for CO2 reduction (E = −1.09 V vs. RHE) displays good agreement with the experimental findings and, therefore, support the CO2 insertion onto Sn-oxide as a plausible mechanism for the CO2 reduction in the potential domain where metastable oxides are still present on the Sn surface. These results not only rationalize a number of literature divergent reports but also provide a guideline for the design of efficient CO2 reduction electrocatalysts.

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Three-dimensional reconstruction of diagenetic geobodies for geological carbon dioxide storage

International Journal of Greenhouse Gas Control ◽

10.1016/j.ijggc.2015.08.007 ◽

2015 ◽

Vol 42 ◽

pp. 319-328 ◽

Cited By ~ 2

Author(s):

Veerle Vandeginste ◽

Nur Liyana Rafiuddin ◽

Ahron Peskin

Keyword(s):

Carbon Dioxide ◽

Three Dimensional ◽

Carbon Dioxide Storage ◽

Three Dimensional Reconstruction ◽

Dimensional Reconstruction ◽

Geological Carbon Dioxide Storage

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In situ CO2–coal reactions in view of carbon dioxide storage in deep unminable coal seams

Fuel ◽

10.1016/j.fuel.2006.03.007 ◽

2006 ◽

Vol 85 (12-13) ◽

pp. 1904-1912 ◽

Cited By ~ 26

Author(s):

S MAZUMDER ◽

P VANHEMERT ◽

J BRUINING ◽

K WOLF ◽

K DRABE

Keyword(s):

Carbon Dioxide ◽

Carbon Dioxide Storage ◽

Coal Seams

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Carbon dioxide storage in the Captain Sandstone aquifer: determination of in situ stresses and fault-stability analysis

Petroleum Geoscience ◽

10.1144/petgeo2016-036 ◽

2016 ◽

Vol 22 (3) ◽

pp. 211-222 ◽

Cited By ~ 12

Author(s):

John D. O. Williams ◽

Mark W. Fellgett ◽

Martyn F. Quinn

Keyword(s):

Carbon Dioxide ◽

Stability Analysis ◽

Carbon Dioxide Storage ◽

Fault Stability ◽

Sandstone Aquifer ◽

In Situ Stresses

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Real-Time Monitoring of the Effect of CO2 on the Cement Sheath

10.2118/200931-ms ◽

2021 ◽

Author(s):

Paul Wagner ◽

Kris Ravi ◽

Michael Prohaska

Keyword(s):

Carbon Dioxide ◽

Supercritical Carbon Dioxide ◽

Portland Cement ◽

Carbon Dioxide Sequestration ◽

In Situ Monitoring ◽

In Situ Conditions ◽

Cement Sheath ◽

Cement Integrity ◽

Supercritical Carbon

Abstract Global warming is one of the most significant issues the world is facing. Capturing carbon dioxide from the atmosphere or industrial processes and storing it in geological formations (carbon capture and storage, CCS) can help counteract climate change. Nevertheless, the interaction between well barrier elements such as cement, casing, tubulars, packers, and valves can lead to possible leakages. To accomplish successful carbon dioxide sequestration, injecting the carbon dioxide in its supercritical state is necessary. The supercritical carbon dioxide can corrode steel and elastomers and react with the calcium compounds in the cement, dissolving them and forming calcium carbonate and bicarbonate in the process. This carbonation can lead to channels forming on the cement-to-rock interface or cracking due to the carbonate precipitation, resulting in a loss of well integrity. This study focusses on finding ways that enable the continuous monitoring of cement integrity, under in-situ conditions, in a lab setup. The construction of an autoclave, capable of withstanding supercritical conditions of carbon dioxide, facilitates the in-situ monitoring. This autoclave also makes CT-scans of the pressurized sample possible, as well as acoustic measurements, using state-of-the-art piezo elements. The first tests will establish a baseline using neat Class G Portland cement to verify the design and sensors. The set up consists of a rock core in the middle of the autoclave surrounded by a cement sheath. A prepared channel in the center of the core expedites the distribution of the carbon dioxide. Once the ability of the sensors to monitor the integrity is verified, different cement compositions and their interaction with supercritical carbon dioxide can be studied. The experimental setup and the procedure discussed here closely simulate the downhole condition. Hence, the results obtained using this setup and procedure is representative of what could be observed downhole. The direction is not to remove the sample from the autoclave for analysis, as is the current industry practice, but to measure cement integrity under in-situ conditions over an extended period of time. Digitalization is powering the in-situ analysis in these tests. The first two tests of this study, using the afore mentioned autoclave, investigated the carbonation behaviour of two Class G Portland cement slurrys, one with a low and one with a high slurry-density. The low-density slurry showed extensive degradation and even the high-density slurry showed carbonation, but only close to the sandstone core. The results from this study can lead to the prevention of leakage of carbon dioxide to the environment and other formations, which defeats the purpose of carbon dioxide sequestration. These results should improve the economics of these wells as well as the health, safety, and environmental aspects.

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