3D Quantification of Pore Networks and Anthropogenic Carbon Mineralization in Stacked Basalt Reservoirs.

Basalt formations are promising candidates for the geologic storage of anthropogenic CO2 due to their storage capacity, porosity, permeability, and reactive geochemical trapping ability. The Wallula Basalt Carbon Storage Pilot Project demonstrated that supercritical CO2 injected into >800 m deep Columbia River Basalt Group stacked reservoir flow tops mineralizes to ankerite-siderite-aragonite on month-year time scales, with 60% of the 977 metric tons of CO2 converted within 2 years. The potential impacts of mineral precipitation and consequent changes in the rock porosity, pore structure, pore size, and pore size distributions have likely been underestimated hitherto. Herein, we address these knowledge gaps using X-ray microcomputed tomography (XMT) to evaluate the pore network architecture of sidewall cores recovered 2 years after CO2 injection. In this study, we performed a detailed quantitative analysis of the CO2-reacted basalt cores by XMT imaging. Reconstructed 3D images were analyzed to determine the distribution and volumetric details of porosity and anthropogenic carbonate nodules in the cores. Additional mineralogic quantification provided insight into the overall paragenesis and carbonate growth mechanisms, including mineralogic/chemical zonation. These findings are being used to parametrize multiphase reactive transport models to predict the fate and transport of subsurface CO2, enabling scale-up to commercial-scale geologic carbon storage in basalts and other reactive mafic-ultramafic formations.

Parts-Per-Million Carbonate Mineral Quantification with Thermogravimetric Analysis-Mass Spectrometry.

Mitigating the deleterious effects of climate change requires the development and implementation of carbon capture and storage technologies. To expand the monitoring, verification, and reporting (MRV) capabilities of geologic carbon mineralization projects, we developed a thermogravimetric analysis-mass spectrometry (TGA-MS) methodology to enable quantification of <100 ppm calcite (CaCO3) in complex samples. We extended TGA-MS calcite calibration curves to enable a higher measurement resolution and lower limits of quantification for evolved CO2 from a calcite-corundum mixture. We demonstrated <100 ppm carbonate mineral quantification with TGA-MS for the first time, an outcome applicable across earth, environmental, and materials science fields. We applied this carbonate quantification method to a suite of Columbia River Basalt Group (CRBG) well cuttings recovered in 2009 from Pacific Northwest National Laboratory's Wallula #1 Well. Our execution of this new combined calcite and calcite-corundum calibration curve TGA-MS method on our CRBG sample suite indicated average carbonate contents of 0.050 wt % in flow interiors (caprocks) and 0.400 wt % in interflow zones (reservoirs) in the upper 1250 m of the Wallula #1 Well. By advancing our knowledge of continental flood basalt-hosted carbonates in the mafic subsurface and reaching new TGA-MS quantification limits for carbonate minerals, we expand MRV capabilities and support the commercial-scale deployment of carbon mineralization projects in the Pacific Northwest United States and beyond.

Facile Metal Release from Pore-Lining Phases Enables Unique Carbonate Zonation in a Basalt Carbon Mineralization Demonstration.

Carbon-negative strategies such as geologic carbon sequestration in continental flood basalts offers a promising route to the removal of greenhouse gases, such as CO2, via safe and permanent storage as stable carbonates. This potential has been successfully demonstrated at a field scale at the Wallula Basalt Carbon Storage Pilot Project where supercritical CO2 was injected into the Columbia River Basalt Group (CRBG). Here, we analyze recovered post-injection sidewall core cross-sections containing carbonate nodules using µ-XRF chemical mapping techniques that revealed compositional zonation within the nodules. The unique nature of the subsurface anthropogenic carbonates is highlighted by the near absence of Mg in an ankerite-like composition. Furthermore, a comparison between pre- and post-injection sidewall cores along with an in-depth chemical mapping of basalt pore lining cements provides a better understanding into the source and fate of critical cationic species involved in the precipitation of carbon mineralization products. Collectively, these results provide crucial insights into carbonate growth mechanisms under a time-dependent pore fluid composition. As such, these findings will enable parameterization of predictive models for future CO2 sequestration efforts in reactive reservoirs around the world.

Interlayer Cation Polarizability Affects Supercritical Carbon Dioxide Adsorption by Swelling Clays.

Several strategies for mitigating the build-up of atmospheric carbon dioxide (CO2) bring wet supercritical CO2 (scCO2) in contact with phyllosilicates such as illites and smectites. While some work has examined the role of the charge-balancing cation and smectite framework features on CO2/smectite interactions, to our knowledge no one has examined how the polarizability of the charge-balancing cation influences these behaviors. In this paper, the scCO2 adsorption properties of Pb2+, Rb+, and NH4+ saturated smectite clays at variable relative humidity are studied by integrating in situ high-pressure X-ray diffraction (XRD), infrared spectroscopic titrations, and magic angle spinning nuclear magnetic resonance (MAS NMR) methods. The results are combined with previously published data for Na+, Cs+, and Ca2+ saturated versions of the same smectites to isolate the roles of the charge-balancing cations and perform two independent tests of the role of charge-balancing cation polarizability in determining the interlayer fluid properties and smectite expansion. Independent correlations developed for (i) San Bernardino hectorite (SHCa-1) and (ii) Wyoming montmorillonite (SWy-2) both show that cation polarizability is important in predicting the interlayer composition (mol% CO2 in the interlayer fluid and CO2/cation ratio in interlayer) and the expansion behavior for smectites in contact with wet and dry scCO2. In particular, this study shows that the charge-balancing cation polarizability is the most important cation-associated parameter in determining the expansion of the trioctahedral smectite, hectorite, when in contact with dry scCO2. While both independent tests show that cation polarizability is an important factor in smectite-scCO2 systems, the correlations for hectorite are different from those determined for montmorillonite. The root of these differences is likely associated with the roles of the smectite framework on adsorption, warranting follow-up studies with a larger number of unique smectite frameworks. Overall, the results show that the polarizability of the charge-balancing cation should be considered when preparing smectite clays (or industrial processes involving smectites) to capture CO2 and in predicting the behavior of caprocks over time.

Exotic Carbonate Mineralization Recovered from a Deep Basalt Carbon Storage Demonstration.

Mitigating climate change requires transformational advances for carbon dioxide removal, including geologic carbon sequestration in reactive subsurface environments. The Wallula Basalt Carbon Storage Pilot Project demonstrated that CO2 injected into >800 m deep Columbia River Basalt Group flow top reservoirs mineralizes on month-year timescales. Herein, we present new optical petrography, micro-computed X-ray tomography, and electron microscopy results obtained from sidewall cores collected two years after CO2 injection. As no other anthropogenic carbonates from geologic carbon storage field studies have been recovered, this world-unique sample suite provides unparalleled insight for subsurface carbon mineralization products and paragenesis. Chemically zoned nodules with Ca/Mn-rich cores and Fe-dominant outer rims are prominent examples of the neoformed carbonate assemblages with ankerite-siderite compositions and exotic divalent cation correlations. Paragenetic insights for the timing of aragonite, silica, and fibrous zeolites are clarified based on mineral texture and spatial relationships, along with time-resolved downhole fluid sampling. Collectively, these results clarify the mineralogy, chemistry, and paragenesis of carbon mineralization, providing insight into the ultimate fate and transport of CO2 in reactive mafic-ultramafic reservoirs.

Transport of polymer-coated metal-organic framework nanoparticles in porous media.

Injecting fluids into deep underground geologic structures is a critical component to development of long-term strategies for managing greenhouse gas emissions and facilitating energy extraction operations. Recently, we reported that metal-organic frameworks are low-frequency, absorptive-acoustic metamaterial that may be injected into the subsurface to enhance geophysical monitoring tools used to track fluids and map complex structures. A key requirement for this nanotechnology deployment is transportability through porous geologic media without being retained by mineral-fluid interfaces. We used flow-through column studies to estimate transport and retention properties of five different polymer-coated MIL-101(Cr) nanoparticles (NP) in siliceous porous media. When negatively charged polystyrene sulfonate coated nanoparticles (NP-PSS-70K) were transported in 1 M NaCl, only about 8.4% of nanoparticles were retained in the column. Nanoparticles coated with polyethylenimine (NP-PD1) exhibited significant retention (> 50%), emphasizing the importance of complex nanoparticle-fluid-rock interactions for successful use of nanofluid technologies in the subsurface. Nanoparticle transport experiments revealed that nanoparticle surface characteristics play a critical role in nanoparticle colloidal stability and as well the transport.

Porous Colloidal Nanoparticles as Injectable Multimodal Contrast Agents for Enhanced Geophysical Sensing.

Injecting fluids into underground geologic structures is crucial for the development of long-term strategies for managing captured carbon and facilitating sustainable energy extraction operations. We have previously reported that the injection of metal-organic frameworks (MOFs) into the subsurface can enhance seismic monitoring tools to track fluids and map complex structures, reduce risk, and verify containment in carbon storage reservoirs because of their absorption capacity of low-frequency seismic waves. Here, we demonstrate that water-based Cr/Zn/Zr MOF colloidal suspensions (nanofluids) are multimodal geophysical contrast agents that enhance near-wellbore logging tools. Based on experimental fluid-only measurements, MIL-101(Cr), ZIF-8, and UiO-66 nanofluids have distinct complex conductivity and/or low-field nuclear magnetic resonance (NMR) signatures that are relevant to field-deployed technologies, implying the potential to enhance near-wellbore monitoring of CO2 injection and associated processes with downhole logging tools. Small- and wide-angle X-ray scattering characterization of ∼0.5 wt % MIL-101(Cr) suspensions confirmed phase stability and provided insight into the fractal nature of colloidal nanoparticles. Finally, low-field (2 MHz) NMR measurements of MIL-101(Cr) nanofluid injection into a prototypical Berea sandstone demonstrate how paramagnetic high-surface area MOFs may dominate the relaxation times of hydrogen-bearing fluids in porous geologic matrices, enhancing the mapping of near-surface and near-wellbore transport pathways and advancing sustainable subsurface energy technologies.

Molecular Intermediate in the Directed Formation of a Zeolitic Metal-Organic Framework.

Directed synthesis promises control over architecture and function of framework materials. In practice, however, designing such syntheses requires a detailed understanding of the multistep pathways of framework formations, which remain elusive. By identifying intermediate coordination complexes, this study provides insights into the complex role of a structure-directing agent (SDA) in the synthetic realization of a promising material. Specifically, a novel molecular intermediate was observed in the formation of an indium zeolitic metal-organic framework (ZMOF) with a sodalite topology. The role of the imidazole SDA was revealed by time-resolved in situ powder X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS).

Quantification of CO2 Mineralization at the Wallula Basalt Pilot Project.

In 2013, the Pacific Northwest National Laboratory led a geologic carbon sequestration field demonstration where ∼1000 tonnes of CO2 was injected into several deep Columbia River Basalt zones near Wallula, Washington. Rock core samples extracted from the injection zone two years after CO2 injection revealed nascent carbonate mineralization that was qualitatively consistent with expectations from laboratory experiments and reactive transport modeling. Here, we report on a new detailed analysis of the 2012 pre-injection and 2015 post-injection hydrologic tests that capitalizes on the difference in fluid properties between scCO2 and water to assess changes in near-field, wellbore, and reservoir conditions that are apparent approximately two years following the end of injection. This comparative hydrologic test analysis method provides a new way to quantify the amount of injected CO2 that was mineralized in the field test. Modeling results indicate that approximately 60% of the injected CO2 was sequestered via mineralization within two years, with the resulting carbonates occupying ∼4% of the available reservoir pore space. The method presented here provides a new monitoring tool to assess the fate of CO2 injected into chemically reactive basalt formations but could also be adapted for long-term monitoring and verification within more traditional subsurface carbon storage reservoirs.

Microporous and Flexible Framework Acoustic Metamaterials for Sound Attenuation and Contrast Agent Applications.

The low-frequency (100-1250 Hz) acoustic properties of metal-organic framework (MOF) materials were examined in impedance tube experiments. The anomalously high sound transmission loss of HKUST-1, FeBTC, and MIL-53(Al) quantitatively demonstrated that these prototypical MOFs are absorptive acoustic metamaterials. To the best of our knowledge, this is the first example of MOFs that have been demonstrated to be acoustic metamaterials. Low-frequency acoustic dampening by subwavelength MOF metamaterials is likely due to sound dissipation and absorption facilitated by multiple internal reflections within the microporous framework structure. Modification of MIL-53(Al) with flexible organic linkers clarified that acoustic signatures of the MOFs may be tailored to add or alter certain diagnostic acoustic signatures. These results may be applied to the rational design of lightweight sound-insulating construction materials and acoustic contrast agents for subsurface mapping and monitoring applications at low frequency (100-1250 Hz).

Dynamic Adsorption of CO2/N2 on Cation-Exchanged Chabazite SSZ-13: A Breakthrough Analysis.

Alkali-exchanged SSZ-13 adsorbents were investigated for their applicability in separating N2 from CO2 in flue gas streams using a dynamic breakthrough method. In contrast to IAST calculations based on equilibrium isotherms, K+ exchanged SSZ-13 was found to yield the best N2 productivity, comparable to Ni-MOF-74, under dynamic conditions where diffusion properties play a significant role. This was attributed to the selective, partial blockage of access to the chabazite cavities, enhancing the separation potential in a 15/85 CO2/N2 binary gas mixture.

Fluorocarbon adsorption in hierarchical porous frameworks.

Metal-organic frameworks comprise an important class of solid-state materials and have potential for many emerging applications such as energy storage, separation, catalysis and bio-medical. Here we report the adsorption behaviour of a series of fluorocarbon derivatives on a set of microporous and hierarchical mesoporous frameworks. The microporous frameworks show a saturation uptake capacity for dichlorodifluoromethane of >4 mmol g(-1) at a very low relative saturation pressure (P/Po) of 0.02. In contrast, the mesoporous framework shows an exceptionally high uptake capacity reaching >14 mmol g(-1) at P/Po of 0.4. Adsorption affinity in terms of mass loading and isosteric heats of adsorption is found to generally correlate with the polarizability and boiling point of the refrigerant, with dichlorodifluoromethane > chlorodifluoromethane > chlorotrifluoromethane > tetrafluoromethane > methane. These results suggest the possibility of exploiting these sorbents for separation of azeotropic mixtures of fluorocarbons and use in eco-friendly fluorocarbon-based adsorption cooling.

In situ X-ray diffraction study of Na+ saturated montmorillonite exposed to variably wet super critical CO2.

Reactions involving variably hydrated super critical CO(2) (scCO(2)) and a Na saturated dioctahedral smectite (Na-STX-1) were examined by in situ high-pressure X-ray diffraction at 50 °C and 90 bar, conditions that are relevant to long-term geologic storage of CO(2). Both hydration and dehydration reactions were rapid with appreciable reaction occurring in minutes and near steady state occurring within an hour. Hydration occurred stepwise as a function of increasing H(2)O in the system; 1W, 2W-3W, and >3W clay hydration states were stable from ~2-30%, ~31-55 < 64%, and ≥ ~71% H(2)O saturation in scCO(2), respectively. Exposure of sub 1W clay to anhydrous scCO(2) caused interlayer expansion, not contraction as expected for dehydration, suggesting that CO(2) intercalated the interlayer region of the sub 1W clay, which might provide a secondary trapping mechanism for CO(2). In contrast, control experiments using pressurized N(2) and similar initial conditions as in the scCO(2) study, showed little to no change in the d(001) spacing, or hydration states, of the clay. A salient implication for cap rock integrity is that clays can dehydrate when exposed to wet scCO(2). For example, a clay in the ~3W hydration state could collapse by ~3 Å in the c* direction, or ~15%, if exposed to scCO(2) at less than or equal to about 64% H(2)O saturation.

In situ infrared spectroscopic study of forsterite carbonation in wet supercritical CO2.

Carbonation reactions are central to the prospect of CO(2) trapping by mineralization in geologic reservoirs. In contrast to the relevant aqueous-mediated reactions, little is known about the propensity for carbonation in the key partner fluid: supercritical carbon dioxide containing dissolved water ("wet" scCO(2)). We employed in situ mid-infrared spectroscopy to follow the reaction of a model silicate mineral (forsterite, Mg(2)SiO(4)) for 24 h with wet scCO(2) at 50 °C and 180 atm. The results show a dramatic dependence of reactivity on water concentration and the presence of liquid water on the forsterite particles. Exposure to neat scCO(2) showed no detectable carbonation reaction. At 47% and 81% water saturation, an Ångstrom-thick liquid-like water film was detected on the forsterite particles and less than 1% of the forsterite transformed. Most of the reaction occurred within the first 3 h of exposure to the fluid. In experiments at 95% saturation and with an excess of water (36% above water saturation), a nanometer-thick water film was detected, and the carbonation reaction proceeded continuously with approximately 2% and 10% conversion, respectively. Our collective results suggest constitutive links between water concentration, water film formation, reaction rate and extent, and reaction products in wet scCO(2).