Wet Supercritical CO2 Research Articles

Investigation of chemical processes in cement exposed to wet ScCO2 and CO2-saturated brine in geological CO2 storage conditions

In geological CO2 storage conditions, wellbore cement can be exposed to both supercritical CO2 (ScCO2) with water vapor, and CO2 dissolved in water. There is a lack of studies that investigate the effects of reaction environments on the extent of CO2-induced cement carbonation and leaching. In this study, four CO2 exposure experiments were designed with wellbore cement samples exposed to both ScCO2 and CO2 dissolved in water to investigate the impacts of evaporation, capillarity, diffusion, and salt deposition on cement carbonation. Severe cement carbonation after 14 and 28 days of CO2 exposure was observed in a wet ScCO2 phase. When water evaporation into ScCO2 phase was minimized by a steel plate between the brine phase and the ScCO2 phase, a strong cement carbonation in ScCO2 phase was still visible. The reason was that imbibition and diffusion drove water to migrate from the lower section to the upper section of the cement sample to participate in the carbonation reaction. The level of cement carbonation in different CO2 exposure environments was ranked as: wet ScCO2 > CO2 dissolved in water > Pure-ScCO2. The corresponding maximum carbonation area ratios were 90 % and 38 % for the wet ScCO2 scenario and the brine scenario, respectively, compared with a maximum carbonation area ratio of 20 % for the Pure-ScCO2 scenario. This study implies that the most altered region in wellbore cement is at the ScCO2—water interface, and the expansion rate of the altered region is the key to evaluate the potential for CO2 leakage through wellbore cement.

Dissolution and reprecipitation of amorphous silica in silica Rich shales induces Non-Monotonic evolution of porosity in acidic reactive environments

Advances in sustainable subsurface energy technologies are crucial for meeting our energy and resource needs for a climate-resilient future. Novel strategies to harness subsurface shale reservoirs for recovering valuable metals and for enabling CO2 storage are influenced by the morphological and mineralogical heterogeneities of these materials. In this context, delineating the interactions of highly acidic solutions such as wet supercritical CO2 on shales with varying mineralogy is crucial to inform the stability of caprock seal for CO2 storage and enhancements in permeability for fluid transport, reactivity, and storage. The feedback chemical effects associated with the interactions of acidic solutions on the morphologies and mineralogies of shales have not been extensively investigated. These insights are crucial for assessing temporal changes in the reactivity and the fate of the fluids in subsurface environments. In this study, we investigate the effect of 1 M HCl solution on the chemistry and morphology of three different shale samples with varying carbonate, clay and silica contents. An increase in the amorphous content, from 37 % to 41.3 %, of silica-rich and carbonate/clay lean shale is noted due to reactions with an acidic solution which is attributed to the dissolution of Si-bearing phases such as clays, accompanied by SiO2 precipitation. In shales bearing high content of clays and carbonates, significant increase in the pore volumes and surface areas are noted. Non-monotonic changes in the micron-scale porosity of silica rich – carbonate/clay lean (e.g., Mowry shale) are noted using in-situ X-ray microtomography experiments. Due to the initial mobilization of silica and dissolution of carbonate/clay phases, the total porosity slightly increases from 6.7 % to 10.7 % followed by a decrease to ∼4 % caused by SiO2 reprecipitation. These findings suggest that even though silica is less reactive in acidic environments, the changes in the amorphous and crystalline content due to dissolution and reprecipitation alter the porosity and fluid flow paths.

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.

Effect of adding organo-modified montmorillonite nanoclay on the performance of oil-well cement paste in CO2-rich environments

This work studies the influence of incorporating organo-modified montmorillonite (OMMT) nanoclay in class G cement pastes on chemical and mechanical resistance in CO2-rich environments. Cement paste specimens, with and without added nanoclay (0.5%, 1%, 2% in wt.), were submitted to degradation tests in CO2-saturated water and wet supercritical CO2, at 90 °C and 15 MPa. Scanning electron microscopy, X-ray diffraction, computed X-ray microtomography, pycnometry, Vickers microhardness measurements, and compressive strength tests were used to evaluate the effect of the OMMT nanoclay on the cement paste properties. The addition of 0.5% OMMT nanoclay increased the specific density and the compressive strength of hardened cement paste and decreased chemically modified layer as a result of CO2 attack. However, these effects became less evident with increasing OMMT nanoclay content. Additionally, the Vickers microhardness and compressive strength results suggest that OMMT nanoclay can prevent the high precipitation of carbonates that influences the diffusion of CO2 into cement paste.

Pressurized in situ X-ray diffraction insights into super/subcritical carbonation reaction pathways of steelmaking slags and constituent silicate minerals

This study explores mineral carbonation of industrial stainless steelmaking slags and relevant synthetic constituent minerals via in situ pressurized X-ray diffraction, to clarify carbonation reaction pathways and efficiency for carbon storage and waste valorization. The primary mineral phases of Argon Oxygen Decarburization (AOD) and Continuous Casting (CC) slags, namely, åkermanite, bredigite, cuspidine, merwinite, and β- and γ-C2S, were reacted in a custom-built beryllium-capped XRD reactor filled with either water-saturated (wet) subcritical CO2(g), or wet supercritical CO2(SC), in a series of carbonation experiments. Formation of calcite and aragonite was observed for most Ca-bearing minerals, transient precipitation of metastable vaterite was observed, while carbonation of AOD and CC slags in CO2(SC) resulted in hydrated crystalline calcium carbonates and indirect evidence of amorphous carbonate. Results obtained suggest that low-pressure subcritical carbonation routes are attractive for standalone slag carbonation processes, while high-pressure supercritical carbonation routes are amiable to symbiotic integration with CO2(SC)-generating green technologies.

Impact of wet supercritical CO2 injection on fly ash geopolymer cement under elevated temperatures for well cement applications

An alternative cement system created through geopolymerization of fly ash offers favorable properties such as able to resist acidic fluids and possess high compressive strength. However, the application of fly ash geopolymer as wellbore cement under carbon dioxide (CO2) environment at elevated temperature is not well recorded in the literature. This paper characterizes the fly ash-based geopolymer cement and experimentally investigates its mechanical and microstructure changes after exposed to CO2 under elevated temperature. Microstructure identification on the altered cement paste was conducted by the analysis of XRD and SEM. In this study, fly ash-based alkali-activated cement was made using 8 molal sodium hydroxide and sodium silicate as alkali activators. The results found that crystal-like shape identified as calcium carbonate was formed at the surface of spherical fly ash particle after carbonation formation. The strength of geopolymer cement was found not to be decreased although carbonation process was occurred. Microstructure analysis revealed that zeolite was formed during CO2 acid exposure for geopolymer cement which contributes to the strength development.

Thin-film dawsonite in Jurassic coal measure strata of the Yaojie coalfield, Minhe Basin, China: A natural analogue for mineral carbon storage in wet supercritical CO2

A large amount of thin-film dawsonite has developed in coal cleats and also in fractures within the roof sandstone in Jurassic CO2-rich coal measure strata of the Yaojie coalfield, Minhe Basin, China. The CO2 in these strata has been in a supercritical state since natural emplacement. In this study, the Yaojie coalfield is considered a natural analogue site for CO2 capture, utilization, and storage (CCUS). The thin-film dawsonite in coal measure strata was analyzed to investigate the evolution of carbon in supercritical CO2 after CCUS, as it provides a possible example of the formation of carbonate minerals from a wet supercritical CO2 fluid. The cleat- and fracture-filling dawsonite takes the form of white or silver-white radial thin-film crystals (generally <3.2mm in diameter and <20μm in thickness) and appears in a variety of shapes, with the mineral fibers growing divergently within the plane of the film. The thin-film dawsonite within cleats is readily separated from the coal, and its crystal morphology is controlled by the cleat space. The thin-film dawsonite in the roof sandstone does not completely fill fractures, and the morphological characteristics of the surfaces of the mineral crystals indicate that crystal growth was not constrained by the surrounding rock. The sources of the carbon for the cleat-filling dawsonite were magmatic CO2 and CO2 derived from the decomposition of basement marble, which resulted from dynamic–thermal metamorphism of the F19 fault zone. The carbon isotopic compositions of the cleat-filling dawsonite from different carbon sources are transitional, and the carbon source for all of the sandstone fracture-filling dawsonite is the CO2 released from the decomposed basement marble. The morphological and mineralogical characteristics of the thin-film dawsonite show that it most likely nucleated and grew directly in the liquid-like water film formed by wet supercritical CO2 on solid phase surfaces, rather than by epitaxial growth on the rocks surrounding the cleats and fractures, probably via layer-by-layer crystallization. The sodium and aluminum in the dawsonite were derived from formation water. The formation of dawsonite in the coal measure strata of the Yaojie coalfield indicates that some of the free-state CO2, which increases in content due to desorption of the coal matrix, can ultimately be converted into carbonate minerals during CCUS.

An Experimental Study of the Carbonation of Serpentinite and Partially Serpentinised Peridotites

In situ sequestration of CO2 in mantle peridotites has been proposed as a method to alleviate the amount of anthropogenic CO2 in the atmosphere. This study presents the results of eight-month long laboratory fluid-rock experiments on representative mantle rocks from the Oman-United Arab Emirates ophiolite to investigate this process. Small core samples (3 cm long) were reacted in wet supercritical CO2 and CO2-saturated brine at 100 bar and 70°C. The extent of carbonate formation, and hence the degree of carbon sequestration, varied greatly depending on rock type, with serpentinite (lizardite-dominated) exhibiting the highest capacity, manifested by the precipitation of magnesite MgCO3 and ferroan magnesite (Mg,Fe)CO3. The carbonate precipitation occurred predominantly on the surface of the core and subordinately within cross-cutting fractures. The extent of the CO2 reactions appeared to be principally controlled by the chemical and mineralogical composition of the rock, as well as the rock texture, with all these factors influencing the extent and rate of mineral dissolution and release of Mg and Fe for subsequent reaction with the CO2. It was calculated that ≈ 0.7 g of CO2 was captured by reacting ≈ 23 g of serpentinite, determined by the mass of magnesite formed. This equates to ≈ 30 kg CO2 per tonne of host rock, equivalent to ≈ 3% carbonation in half a year. However, recycling of carbonate present in veins within the original rock sample could mean that the overall amount is around 2%. The increased reactivity of serpentinite was associated with preferential dissolution of more reactive types of serpentine minerals and brucite, that were mainly present in the cross-cutting veins. The bulk of the serpentinite rock was little affected. This study, using relatively short term experiments, suggests that serpentinite might be a good host rock for CO2 sequestration, although long term experiments might prove that dunite and harzburgite could be an effective in an engineered system of CCSM. Wet scCO2 proved to be chemically aggressive than CO2-saturated brine and its ingress along fractures and grain boundaries resulted in greater host rock dissolution and subsequent carbonate precipitation.

Reactivity of micas and cap-rock in wet supercritical CO2 with SO2 and O2 at CO2 storage conditions

Seal or cap-rock integrity is a safety issue during geological carbon dioxide capture and storage (CCS). Industrial impurities such as SO2, O2, and NOx, may be present in CO2 streams from coal combustion sources. SO2 and O2 have been shown recently to influence rock reactivity when dissolved in formation water. Buoyant water-saturated supercritical CO2 fluid may also come into contact with the base of cap-rock after CO2 injection. Supercritical fluid-rock reactions have the potential to result in corrosion of reactive minerals in rock, with impurity gases additionally present there is the potential for enhanced reactivity but also favourable mineral precipitation.The first observation of mineral dissolution and precipitation on phyllosilicates and CO2 storage cap-rock (siliciclastic reservoir) core during water-saturated supercritical CO2 reactions with industrial impurities SO2 and O2 at simulated reservoir conditions is presented. Phyllosilicates (biotite, phlogopite and muscovite) were reacted in contact with a water-saturated supercritical CO2 containing SO2, or SO2 and O2, and were also immersed in the gas-saturated bulk water. Secondary precipitated sulfate minerals were formed on mineral surfaces concentrated at sheet edges. SO2 dissolution and oxidation resulted in solution pH decreasing to 0.74 through sulfuric acid formation. Phyllosilicate dissolution released elements to solution with ∼50% Fe mobilized. Geochemical modelling was in good agreement with experimental water chemistry. New minerals nontronite (smectite), hematite, jarosite and goethite were saturated in models. A cap-rock core siltstone sample from the Surat Basin, Australia, was also reacted in water-saturated supercritical CO2 containing SO2 or in pure supercritical CO2. In the presence of SO2, siderite and ankerite were corroded, and Fe-chlorite altered by the leaching of mainly Fe and Al. Corrosion of micas in the cap-rock was however not observed as the pH was buffered by carbonate dissolution. Ca-sulfate, and Fe-bearing precipitates were observed post SO2-CO2 reaction, mainly centered on surface cracks and an illite rich illite-smectite precipitate quantified. Water saturated impure supercritical CO2 was observed to have reactivity to rock-forming biotite, muscovite and phlogopite mineral separates. In the cap-rock core however carbonates and chlorite were the main reacting minerals showing the importance of assessing actual whole core.

Comparative Study of the Performance of SAE 1010, API K55 and API N80 Steels Regarding to Corrosion Resistance in the Presence of High CO&lt;sub&gt;2&lt;/sub&gt; Pressure

The performance of SAE 1010, API K55 and API N80 steels were evaluated in terms of resistance to corrosion with the use of two CO2-saturated saline solutions (NaCl and CaCl2, both at the concentration of 0.5 M) and wet supercritical CO2 at a temperature of 90°C under 15 MPa for 07 days. Mass loss tests were performed to determine corrosion rates and the films of corrosion product evaluated by scanning electron microscopy and potentiodynamic polarization technique. Lower corrosion rates were obtained in a wet supercritical CO2 medium. The degree of protection offered by corrosion products films depended not only on the steel but also on the corrosive medium and kind of salt present.

Comparative reactivity study of forsterite and antigorite in wet supercritical CO2 by in situ infrared spectroscopy

The carbonation reactions of forsterite (Mg2SiO4) and antigorite [Mg3Si2O5(OH)4], representatives of olivine and serpentine minerals, in dry and wet supercritical carbon dioxide (scCO2) at conditions relevant to geologic carbon sequestration (35°C and 100bar) were studied by in situ Fourier transform infrared (FT-IR) spectroscopy. Our results confirm that water plays a critical role in the reactions between metal silicate minerals and scCO2. For neat scCO2, no reaction was observed in 24hr for either mineral. When water was added to the scCO2, a thin water film formed on the minerals’ surfaces, and the reaction rates and extents increased as the water saturation level was raised from 54% to 116% (excess water). For the first time, the presence of bicarbonate, a key reaction intermediate for metal silicate reactions with scCO2, was observed in a heterogeneous system where mineral solids, an adsorbed water film, and bulk scCO2 co-exist. In excess-water experiments, approximately 4% of forsterite and less than 2% of antigorite transformed into hydrated Mg-carbonates. A precipitate similar to nesquehonite (MgCO3·3H2O) was observed for forsterite within 6hr of reaction time, but no such precipitate was formed from antigorite until after water was removed from the scCO2 following a 24-hr reaction period. The reduced reactivity and carbonate-precipitation behavior of antigorite was attributed to slower, incongruent dissolution of the mineral and lower concentrations of Mg2+ and HCO3− in the water film. The in situ measurements employed in this work make it possible to quantify metal carbonate precipitates and key reaction intermediates such as bicarbonate for the investigation of carbonation reaction mechanisms relevant to geologic carbon sequestration.

Experimental study of potential wellbore cement carbonation by various phases of carbon dioxide during geologic carbon sequestration

Hydrated Portland cement was reacted with CO2 in supercritical, gaseous and aqueous phases to understand the potential cement alteration processes along the length of a wellbore, extending from a deep CO2 storage reservoir to the shallow subsurface during geologic carbon sequestration. The 3-D X-ray microtomography (XMT) images showed that the cement alteration was significantly more extensive with CO2-saturated synthetic groundwater than dry or wet supercritical CO2 at high P (10MPa)-T (50°C) conditions. Scanning electron microscopy with energy dispersive spectroscopy (SEM–EDS) analysis also exhibited a systematic Ca depletion and C enrichment in cement matrix exposed to CO2-saturated groundwater. Integrated XMT, XRD and SEM–EDS analyses identified the formation of an extensive carbonated zone filled with CaCO3(s), as well as a porous degradation front and an outermost silica-rich zone in cement after exposure to CO2-saturated groundwater. Cement alteration by CO2-saturated groundwater for 2–8months overall decreased the porosity from 31% to 22% and the permeability by an order of magnitude. Cement alteration by dry or wet supercritical CO2 was slow and minor compared to CO2-saturated groundwater. A thin single carbonation zone was formed in cement after exposure to wet supercritical CO2 for 8months or dry supercritical CO2 for 15months. An extensive calcite coating was formed on the outside surface of a cement sample after exposure to wet gaseous CO2 for 1–3months. The chemical–physical characterization of hydrated Portland cement after exposure to various phases of CO2 indicates that the extent of cement carbonation can be significantly heterogeneous depending on the CO2 phase present in the wellbore environment. Both experimental and geochemical modeling results suggest that wellbore cement exposure to supercritical, gaseous and aqueous phases of CO2 during geologic C sequestration is unlikely to damage the wellbore integrity because cement alteration by all phases of CO2 is dominated by carbonation reactions. This is consistent with previous field studies of wellbore cement with extensive carbonation after exposure to CO2 for three decades. However, XMT imaging indicates that preferential cement alteration by supercritical CO2 or CO2-saturated groundwater can occur along the cement–steel or cement–rock interfaces. This highlights the importance of further investigation of cement degradation along the interfaces of wellbore materials to ensure permanent geologic carbon storage.

Monitoring the Effect of Mineral Precursor, Fluid Phase CO2–H2O Composition, and Stirring on CaCO3 Crystallization in a Supercritical—Ultrasound Carbonation Process

This study focuses on the evaluation of the different factors that affect the particle size distribution of precipitated calcium carbonate formed in a wet supercritical CO2 carbonation process and on the conversion rate from two different Ca2+ precursors (Ca(OH)2 or CaO). The operating factors investigated include the composition of the fluid phase (CO2/H2O) in contact with the solid precursor, the calcium cation source, and the stirring mode (no agitation, vertical mechanical, and ultrasound). The calcium carbonate particles were fabricated in batch mode in a stainless steel reactor filled with the solid precursor, water, and scCO2 at 130 bar and 40 °C. The particle size was estimated using scanning electron microscopy, while the precipitated solid phase composition was determined by a quantitative characterization method based on X-ray diffraction. The conversion of CaO or Ca(OH)2 to CaCO3 varied from 50 to >90 wt % depending on the reactor fill level and the existence of a rich-water phase in equilibrium with the scCO2-rich fluid. It was found that micrometric particles were precipitated in systems containing a large quantity of water in the fluid phase, while nanometric calcite was formed when using a reduced water percentage. The use of ultrasound stirring accelerated the kinetics of the carbonation process, thus increasing the calcium carbonate yield. The highest conversion rates were obtained using CaO as the solid precursor.

Evolution of the Petrophysical and Mineralogical Properties of Two Reservoir Rocks Under Thermodynamic Conditions Relevant for CO2Geological Storage at 3 km Depth

Injection of carbon dioxide (CO2 ) underground, for long-term geological storage purposes, is considered as an economically viable option to reduce greenhouse gas emissions in the atmosphere. The chemical interactions between supercritical CO2 and the potential reservoir rock need to be thoroughly investigated under thermodynamic conditions relevant for geological storage. In the present study, 40 samples of Lavoux limestone and Adamswiller sandstone, both collected from reservoir rocks in the Paris basin, were experimentally exposed to CO2 in laboratory autoclaves specially built to simulate CO2 -storage-reservoir conditions. The two types of rock were exposed to wet supercritical CO2 and CO2 -saturated water for one month, at 28 MPa and 90°C, corresponding to conditions for a burial depth approximating 3 km. The changes in mineralogy and microtexture of the samples were measured using X-ray diffraction analyses, Raman spectroscopy, scanning-electron microscopy, and energy-dispersionspectroscopy microanalysis. The petrophysical properties were monitored by measuring the weight, density, mechanical properties, permeability, global porosity, and local porosity gradients through the samples. Both rocks maintained their mechanical and mineralogical properties after CO2 exposure despite an increase of porosity and permeability. Microscopic zones of calcite dissolution observed in the limestone are more likely to be responsible for such increase. In the sandstone, an alteration of the petrofabric is assumed to have occurred due to clay minerals reacting with CO2 . All samples of Lavoux limestone and Adamswiller sandstone showed a measurable alteration when immersed either in wet supercritical CO2 or in CO2 -saturated water. These batch experiments were performed using distilled water and thus simulate more severe conditions than using formation water (brine).

耐ＣＯ２セメントテクノロジー

CO2 resistant cement-zonal isolation technology dedicated to CO2 geological storage-provides an enduring solution to reducing well leakage risks in carbon capture and storage (CCS) and CO2 enhanced oil recovery (EOR) projects.CCS involves capturing CO2 from the major sources of concentrated emissions and injecting it into selected geological formations such as saline aquifers, depleted hydrocarbon reservoirs and unminable coal beds. CCS has the potential to make a critical contribution to reducing the amount of greenhouse gas released into the atmosphere as the most effective, safe, and low-cost long-term CO2 storage technology.One of the key requirements in CCS is long-term zonal isolation. Subsurface pressure and temperature changes can compromise the stability and integrity of the cement sheath around a CO2 injection well. Compromising well integrity can quickly lead to CO2 leakage at the surface, putting containment at risk. That's why the cement sheath used in the wellbore must be exceptionally durable and able to maintain its integrity for hundreds of years.Portland cement has been used successfully for decades in oil and gas well cementing. However, such cements are thermodynamically unstable in CO2-rich environments and degrade once exposed to CO2 in the presence of water. For this reason, compromised well integrity has been identified as the greatest risk factor for leakage from underground storage sites.CO2-resistant cement ensures lasting zonal isolation. In laboratory tests, the system proved highly resistant to CO2 attack, maintaining stable mechanical properties after exposure to simulated extreme injection/storage downhole conditions, including wet supercritical CO2 and water saturated with CO2. This cement system is 100% compatible with Portland cement and can be blended, mixed, and pumped using standard field equipment. It can be used for zonal isolation in new CO2 injection wells, or to plug and abandon existing CO2 injection/production wells at the end of a project.