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At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Cryo-based Structural Characterization and Growth Model of Salt Film on Metal

Metal salt films play a critical role in high rate dissolution processes such as within an active pit. However, structural and compositional characterization of salt films is challenging owing to the dynamic nature of the dissolving interface. Here, the salt film formed on SS304 one-dimensional artificial pit surface was directly characterized using flash freezing and cryo-based focused ion beam/scanning electron microscopy. The salt film exhibits a porous structure. Ni is co-located with Fe in the salt film, indicating the formation of co-precipitated salt containing Fe2+ and Ni2+. Additionally, a salt film growth model is presented based on ion transport.

Salt film, Pitting corrosion, Cryogenic, Cryo-FIB/↗
DOE OSTI2021

Environmental degradation of electroplated nickel and copper coated SS316H in molten FLiNaK salt

Corrosion of nickel and copper electroplated coatings on SS316H in molten FLiNaK salt was studied. 500- and 1000-hour static corrosion tests were performed in molten FLiNaK at 700 degrees Celsius. Characterization of the coatings following corrosion indicated that they did not degrade in the molten salt during the corrosion experiment and fully protected the underlying SS316H from chromium dissolution. Interdiffusion between the copper coating and SS316H was extremely limited, interdiffusion between the nickel coating and SS316H. Diffusion modelling revealed that the nickel coatings still significantly reduced chromium dissolution over 60 years despite the interdiffusion.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Corrosion characteristics of Mo and TZM alloy for plasma facing components in molten lithium at 623 K

Here, in this study, the corrosion behaviours of molybdenum (Mo) and a Mo-based alloy (TZM) were investigated using a static immersion corrosion technique. Weight loss, surface microstructure, and corrosion depth of Mo and the TZM alloy were correlated with elements. The compatibility of Mo and the TZM alloy in static liquid Li was suitable. Mo demonstrated uniform corrosion with a homogenous dissolution of free C and Mo, and TZM alloy exhibited a nonuniform corrosion behaviour with a preferential grain boundary attack caused by the selective dissolution of free C, Ti, and Zr. When the surface oxidation layer of the samples was consumed, free C from Mo and TZM diffused into molten Li to form Li 2 C 2 and then was captured by Zr, Ti, and Mo to form thermodynamically stable carbides, which resulted in the enrichment of the C layer near the sample surfaces. In addition, Ti and Zr acted as N-trappers in liquid Li; the formation of Zr and Ti nitrides resulted in the enrichment of N, Ti, and Zr elements on the surface and led to TZM corrosion increase. Thus, Zr and Ti depletion, pitting, and grain boundary corrosion were problematic for TZM under long-term exposure to liquid Li. Reducing the content of free C and nonmetallic N and increasing the amount of Ti and Zr carbides on the surface of and inside the raw TZM alloy helped improve the corrosion resistance of TZM in liquid Li.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Hot corrosion behavior of 304 & P91 graded composite transition joint under molten sulfate salts

A novel graded composite transition joint (GCTJ) between AISI 304 stainless steel and ASTM A335 P91 steel, has been demonstrated remarkablely superior creep performance compared to the conventional dissimilar metal weldment (DMW) under equivalent conditions. However, this advance is challenged by hot corrosion under salt deposition at elevated temperatures. Here, this study investigates the hot corrosion behavior of 304&P91 GCTJ exposed to sulfate salts at 700°C. Compared to the 304 steel, corrosion attacks initiate in the P91 triangle, where the dual-phase microstructure of ferrite and tempered martensite significantly influences pitting initiation. Anodic dissolution mainly occurs within the tempered martensite due to more vulnerable sites within the tempered martensite. With prolonged exposure, corrosion propagates across both phases, and the corrosion depth within the P91 triangle is related to the exposed surface area ratio between 304 and P91. Electrochemical analysis reveals the occurrence of galvanic corrosion between the 304 and P91, with a positive linear relationship between anodic dissolution current density (I a ) and the exposed surface area ratio between 304 and P91 in molten salts, further emphasizing the critical impact of this ratio on the corrosion severity in the P91 triangle. These findings underscore the importance of transition zone design optimization in mitigating localized corrosion.

Galvanic corrosion↗
DOE OSTI2026

Understanding the high-temperature behavior and corrosion resistance of Cr-Nb coated cladding for BWRs

While Cr-coated Accident Tolerant Fuel has proven successful in Pressurized Water Reactors, its dissolution in high dissolved oxygen Boiling Water Reactor environments represents a major technological barrier. Here, this study presents a comprehensive evaluation of novel Cr-Nb alloys as a coating breakthrough solution for Accident Tolerant Fuel cladding in Boiling Water Reactors. We systematically investigated Physical Vapor Deposited Cr-Nb coatings with 13% and 24 at% Nb content on commercial Zr-based cladding through rigorous testing under both normal and accident conditions. Our results demonstrate Cr-Nb coatings remained completely intact during extended Boiling Water Reactor autoclave testing, while pure Cr coatings failed catastrophically due to oxide dissolution. Under Loss-of-Coolant Accident conditions at 1100°C, Cr-Nb coatings maintained protective capability for 45 min. At 800°C, the alloy coatings matched pure Cr's excellent corrosion resistance. Despite microstructural changes during prolonged high-temperature exposure, no coating delamination occurred, ensuring continued protection of the underlying Zr substrate. These findings establish Cr-Nb coatings as a viable Accident Tolerant Fuel solution for Boiling Water Reactors.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Application of sequential extraction and hydrothermal treatment for characterization and enrichment of rare earth elements from coal fly ash

Rare earth elements (REE) play a critical role in the global economy. The concern about the REE supply challenge has stimulated global interest in recovering REE from alternative non-conventional REE sources such as coal fly ash. In this paper, sequential extraction, physical separations and hydrothermal alkaline treatment were explored for characterization and enrichment of REE from coal fly ash. Seven-step sequential extraction of coal fly ash has demonstrated that 86.1% of total REE were associated with the glassy phase of the fly ash, with the remaining REE mainly distributed in the organic and sulfides phase (8.3%), the exchangeable phase (3.7%), and the carbonates phase (1.5%). A process combining physical separations, namely, particle size separation and magnetic separation, and hydrothermal alkaline treatment was proposed for enrichment of REE from coal fly ash. The optimal hydrothermal alkaline treatment condition was determined. It was demonstrated that NaOH concentration, solid-to-liquid ratio, temperature, and reaction duration had significant influence on ash dissolution in NaOH solution. Grinding could also enhance ash dissolution during subsequent hydrothermal alkaline treatment. Furthermore REE were enriched from coal fly ash from 325 mg/kg to 877 mg/kg via the proposed process under optimal hydrothermal alkaline treatment conditions.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2020

Predicting the potential for mineral scale precipitation in unconventional reservoirs due to fluid-rock and fluid mixing geochemical reactions

Mineral precipitation within hydraulically fractured shale may affect fluid flow pathways and impact longterm hydrocarbon production. The ability to predict geochemical reactions that lead to problematic mineral precipitation will lead to active reservoir management strategies to improve overall production. Using the Marcellus Shale as a case study, a combination of laboratory experiments and reaction path modeling was applied to determine which reactions are likely to occur upon introduction of hydraulic fracturing fluid into the shale reservoir. Experimental results indicate that contact between fracturing fluid and shale will result in dissolution of primary minerals (quartz, feldspars, kaolinite, chlorite, pyrite) and secondary mineral precipitation over time periods of less than one week. Precipitation of barite, Fe-oxides, feldspars, amorphous silica and clay is likely to occur within the reservoir during shut in and early flowback due to mixing between fracturing fluid and reservoir brine as based on modeling saturation indices using experimental fluid data. Reaction path modeling of the experimental scenarios corroborates the specific dissolution and precipitation reactions observed experimentally. Comparison of the results to injected and produced waters from a Marcellus Shale well pad in Greene County, PA, USA, shows that the mineral reactions occur during the hydraulic fracturing, shut in, and early flowback periods. The results presented in this paper demonstrate the value in applying experimental approaches to identify mineral precipitation/dissolution reactions that may significantly impact reservoir performance. The good agreement between geochemical models and experimental results provides confidence that numerical models can be applied to screen the potential fluid-mineral and fluid-mixing reactions in unconventional reservoirs that result in undesired mineral scale precipitation.

58 GEOSCIENCES↗
DOE OSTI2018

Large carbon isotope variability during methanogenesis under alkaline conditions

We report that high carbon isotope values (δ 13 C CH4 > -40‰) have widely been used as evidence that methane in alkaline rock-hosted fluids was formed abiotically, particularly in serpentinizing systems. However, isotope fractionation during microbial methanogenesis is relatively understudied at high pH. We isolated a hydrogenotrophic Methanobacterium sp. from hyperalkaline subsurface fluids in the Samail ophiolite to assess how carbon and hydrogen isotope values of CH 4 varied depending upon pH and carbonate mineral source (NaHCO 3 or CaCO 3 ). The hydrogen isotope fractionation α H20/CH4 (1.46–1.66) did not vary across pH. In contrast, the expressed carbon isotope fractionation, α CO2/CH4 , ranged from 1.028 to 1.089. Carbon isotope fractionation increased with pH, reaching a maximum 13 C depletion of -85‰. However, the 13 C depletion significantly diminished at pH ≥ 9 for CaCO 3 -amended experiments, generating δ 13 C CH4 as high as -28‰. To evaluate the large variability in δ 13 C CH4 , we developed a steady-state model to assess how the rates of carbonate dissolution, cellular uptake of CO 2 and irreversible CH 4 production can affect the net isotope fractionation during methanogenesis. Methanobacterium sp. can produce highly depleted δ 13 C CH4 in simulated alkaline serpentinizing fluids when dissolved inorganic carbon levels are high and methanogenesis rates are slow. However, small carbon isotope fractionation occurs when rates of carbonate dissolution are slower than cellular uptake, leading to relatively high δ 13 C CH4 values (>~-35‰) that are traditionally interpreted to be purely “abiotic”. Lastly, microbial CH 4 can be produced in carbon-limited mafic and ultramafic rock-hosted environments on Earth and potentially other planetary bodies, but it may be difficult to isotopically identify biogenic methane when mineral carbonates are the dominant carbon source.

58 GEOSCIENCES↗
DOE OSTI2018

The impact of depth-dependent water content on steady state weathering and eroding systems

Models for weathering and regolith formation are normally built on the assumption of constant rates of water advection in the zone of water-saturated pores, and constant water content of those pores, but it is common that weathering occurs in the water-unsaturated zone where lateral flow occurs. Hence, water content in pores varies with depth. Here we model mineral weathering profiles while accounting for depth-dependent water content. Like previous models, a mineral equilibrates with water over a length ξ that depends on dissolution and advection rates, but a new lengthscale λ is introduced to describe the decrease of water content with depth. Steady states of the regolith thickness can be attained for any finite λ and non-zero velocity v E of erosion at the land surface. The type of mineral depletion profile developed over geological timescales depends on coupling between weathering and erosion: for slow erosion, a completely developed profile (CDP) is observed, in which the mineral-depleted zone at the top of the regolith has thickness of order λ ; as v E increases, there is a transition to an incompletely developed profile (IDP), in which partial mineral depletion at the land surface is constrained to a narrow range of velocities; when v E exceeds the advance rate of weathering under far from equilibrium conditions, the profile transitions to an unstable regime that exposes bedrock. In general, the reaction front (RF) thickness and the velocity where CPD transitions to IDP depend on the interplay of both water infiltration and chemical equilibration over the timescale of water residence in regolith. The RF thickness roughly equals a correlation length χ defined as half the harmonic average of ξ and λ . In cases of limited water infiltration, water-mineral equilibration is achieved within the length λ , so that the RF thickness is controlled by hydrological properties and is independent of dissolution and advection rates. In the opposite endmember, water infiltrates to large depths and the effects of physical and chemical parameters on RF thickness are the same as in previous geochemical models. The relaxation time for reaching a steady state is shown to be ~ χ / v E . We discuss the effects of physical and chemical parameters in CDPs and IDPs in those endmembers and show an application to a CDP in granitic regolith.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Reactivity of Redox Cycled Fe-bearing Subsurface Sediments Towards Hexavalent Chromium Reduction

Structural Fe(II) in clay minerals and natural sediments is known to reduce Cr(VI) to Cr(III), but the effect of redox-cycled Febearing natural sediments on Cr(VI) reduction kinetics is poorly understood. The objective of this study was to understand the kinetics and mechanisms of Cr(VI) reduction by Fe(II) in redox cycled natural sediment. Fe-bearing sediment was collected from the Ringold formation in the 300 area of Hanford, Washington, United States. Fe redox cycling of the sediment was accomplished via four cycles of bioreduction of structural Fe(III) in Hanford sediment and air oxidation of the resulting Fe(II). Bio-produced Fe(II) in Hanford sediment from each redox cycle was utilized to reduce Cr(VI) at three temperatures (10, 20 and 30° C). The initial rate of Cr(VI) reduction generally increased with each redox cycle, which was more pronounced at high temperatures. The amount of Fe(II) oxidized to the amount of Cr(VI) reduced was close to the expected stoichiometric ratio of 3. Aqueous concentrations of Si, Al, and Fe revealed some dissolution of the sediment after reaction with Cr(VI). Xray diffraction (XRD) and scanning electron microscopy (SEM) detected secondary mineral formation. Mössbauer data showed that the oxidation of Fe(II) was coupled with the reduction of Cr(VI) but no Feoxides/ oxyhydroxides formed. Transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), XANES, and EXAFS were performed for representative reduced Cr solids that formed from reduction of Cr(VI) by sediment-associated Fe(II) at 30oC. TEM revealed that the d-spacing of Cr-reacted montmorillonite at 30° C, a dominant Fe-bearing mineral in Hanford sediment, expanded from 10 Å to 13 Å. This layer expansion was likely due to intercalation of reduced Cr(III) into the interlayer space of the montmorillonite structure. EELS exhibited an L2 absorption peak at 586.0 eV and an L3 absorption peak at 577.0 eV, suggestive of Cr(III) in a hydroxide mineral phase. Similarly, XANES and EXAFS analyses confirmed Cr(VI) reduction to Cr(OH)3 at 30° C and indicated an edge-sharing coordination of the Cr(III) octahedra to 2-3 other Cr or metal ions. This study has important implications for understanding the reactivity of clay-rich sediment towards Cr(VI) reduction at contaminated sites and the stability of the reduced Cr(III).

Bishop, Michael E.↗
DOE OSTI2022

Mineralogical, magnetic and geochemical data constrain the pathways and extent of weathering of mineralized sedimentary rocks

The oxidative weathering of sulfidic rock can profoundly impact watersheds through the resulting export of acidity and metals. Weathering leaves a record of mineral transformation, particularly involving minor redox-sensitive phases, that can inform the development of conceptual and quantitative models. In sulfidic sedimentary rocks, however, variations in depositional history, diagenesis and mineralization can change or overprint the distributions of these trace minerals, complicating the interpretation of weathering signatures. Here we show that a combination of bulk mineralogical and geochemical techniques, micrometer-resolution X-ray fluorescence microprobe analysis and rock magnetic measurements, applied to drill core samples and single weathered fractures, can provide data that enable the development of a geochemically consistent weathering model. This work focused on one watershed in the Upper Colorado River Basin sitting within the Mesaverde Formation, a sedimentary sandstone bedrock with disseminated sulfide minerals, including pyrite and sphalerite, that were introduced during diagenesis and subsequent magmatic-hydrothermal mineralization. Combined analytical methods revealed the pathways of iron (Fe), carbonate and silicate mineral weathering and showed how pH controls element retention or release from the actively weathering fractured sandstone. Drill core logging, whole rock X-ray diffraction, and geochemical measurements document the progression from unweathered rock at depth to weathered rock at the surface. X-ray microprobe analyses of a 1-cm size weathering profile along a fracture surface are consistent with the mobilization of Fe(II) and Fe(III) into acidic pore water from the dissolution of primary pyrite, Fe-sphalerite, chlorite, and minor siderite and pyrrhotite. These reactions are followed by the precipitation of secondary minerals such as of goethite and jarosite, a Fe-(oxyhydr)oxide and hydrous Fe(III) sulfate, respectively. Microscale analyses also helped explain the weathering reactions responsible for the mineralogical transformations observed in the top and most weathered section of the drill core. For example, dissolution of feldspar and chlorite neutralizes the acidity generated by Fe and sulfide mineral oxidation, oversaturating the solution in both Fe-oxides. The combination of X-ray spectromicroscopy and magnetic measurements show that the Fe(III) product is goethite, mainly present either as a coating on fracture surfaces in the actively weathering region of the core or more homogeneously contained within the unconsolidated regolith at the top of the core. Low-temperature magnetic data reveal the presence of ferromagnetic Fe-sulfide pyrrhotite that, although it occurs at trace concentrations, could provide a qualitative proxy for unweathered sulfide minerals because the loss of pyrrhotite is associated with the onset of oxidative weathering. Pyrrhotite loss and goethite formation are detectable through room-temperature magnetic coercivity changes, suggesting that rock magnetic measurements can determine weathering intensity in rock samples at many scales. In conclusion, this work contributes evidence that the weathering of sulfidic sedimentary rocks follows a geochemical pattern in which the abundance of sulfide minerals controls the generation of acidity and dissolved elements, and the pH-dependent mobility of these elements controls their export to the ground- and surface-water.

58 GEOSCIENCES↗
DOE OSTI2026

The solubility and speciation of REE phosphate endmembers (CePO 4 and YPO 4 ) in Cl-rich aqueous fluids from 350 to 450 °C and implications for natural systems

The rare earth elements (REE) are important metals used increasingly in advanced technologies. Within the crust, the elements Ce and Y are commonly more abundant compared to other lanthanides and comprise important end-member constituents of REE-bearing minerals. Specifically, Ce is part of the light (L) REE which have larger ionic radii than the heavy (H) REE, which are grouped together with Y. These differences in ionic radius can lead to important physico-chemical trends within the lanthanide group. Despite a recent increase in experimental and thermodynamic data for the REE at high temperature and pressure, there is still a significant lack of these data at supercritical conditions. In this study we conducted batch-type experiments to measure the solubility of REE phosphates (CePO 4 and YPO 4 ) at varying starting pH (1.5–10), and salinity (0.01–1.4 mol/kg NaCl) at 350 and P sat , and from 400 to 450 °C at 700 bar. Results show that the solubility of Ce (33–0.14 ppb) is generally higher than Y (13–0.13 ppb) and that Ce complexes more strongly with both chloride and hydroxyl ligands compared to Y. The solubilities of both REE phosphates are highly pH-dependent and, to a lesser extent, depend on salinity at the studied conditions. The solubility data from this study were implemented into the GEMSFITS program to optimize the thermodynamic properties of Ce and Y hydroxyl and chloride species. The updated standard partial molal Gibbs energies of formation (Δ f G 0 T,P ) are used within the experimental temperature and pressure range to accurately predict the CePO 4 and YPO 4 solubility and Ce and Y speciation behavior. Based on the updated thermodynamic properties we also provide formation constants (log β n Cl,OH ) for Ce and Y hydroxyl and chloride species. Updated thermodynamic properties are applied to model REE-apatite dissolution and REE mobility based on the Pea Ridge iron oxide apatite deposit in Missouri, USA. The apatite dissolution model replicates natural observations including the replacement of monazite and xenotime after apatite and is an example of the utility of the new thermodynamic constants applied to supercritical crustal fluids. Furthermore, the findings of this study advance the predictive capabilities of geochemical models, our understanding of the behavior of individual REE, and permit modeling the overarching fractionation trends between LREE and HREE in supercritical crustal fluids.

58 GEOSCIENCES↗
DOE OSTI2019

Reservoir scale reactive-transport modeling of a buoyancy-controlled CO 2 plume with impurities (SO 2 , NO 2 , O 2 )

We present that a demonstration project for the geological storage of CO 2 is currently being considered in the deep Precipice Sandstone formation of the Surat Basin, Queensland, Australia. Because of the presence of potential fresh water resources in this formation, a reservoir-scale two-dimensional reactive-transport model was developed to assess temporal and spatial changes in water quality imposed by co-injecting CO 2 with SO 2 , NO 2 , and O 2 at this location. The model shows that because the injection rate is relatively low (60,000 tons/year), flow is buoyancy-dominated and under these conditions the predicted CO 2 flow pattern is quite sensitive to fine-scale heterogeneities and the resolution of the numerical mesh. The model also shows that SO 2 and NO 2 readily partition into the aqueous phase in close vicinity of their injection point, lowering pH somewhat beyond the acidification from CO 2 dissolution. Only O 2 under redox disequilibrium conditions is modeled to persist in the CO 2 plume away from the injection point, however at sub-ppm levels. In conclusion, this modeling effort demonstrates acidification near the wellbore due to the preferential stripping of gas impurities, and accumulation of CO 2 around a lithostratigraphic boundary above the target formation, where relatively rapid mineral dissolution (muscovite, chlorite and calcite) and precipitation (ankerite, kaolinite and chalcedony) occur.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Impacts on mechanical strength of chemical reactions induced by hydrous supercritical CO2 in Boise Sandstone

Geomechanics experiments were used to assess mechanical alteration of Boise Sandstone promoted by reactions with supercritical carbon dioxide (scCO 2 ) and water vapor. During geologic carbon storage, scCO 2 is injected into subsurface reservoirs, forming buoyant plumes. At brine-plume interfaces, scCO 2 can dissolve into native brines, and water from brines can partition into scCO 2 , forming hydrous scCO 2 . This study investigates the effect of hydrous scCO 2 on the strength of Boise Sandstone. Samples are first exposed to recirculating hydrous scCO 2 for 24 h at 70 °C and 13.8 MPa scCO 2 pressure. Samples are reacted with scCO 2 with added water contents up to 500 mL. After scCO 2 exposure, samples are deformed at room temperature under confining pressures of 3.4, 6.9, and 10.3 MPa. The results demonstrate that hydrous scCO 2 induces chemical reactions in Boise Sandstone, with ions migrating from the solid into the hydrous scCO 2 phase. At the longer time-scales, these reactions could lead to mechanical weakening in the samples; however, on the scale of our experiments, the strength changes are within sample variability. Because the solubility of water in scCO 2 is extremely low (0.008 mol H 2 O per 1 mol CO 2 ), the mineral dissolution of Boise Sandstone was under 0.002 wt.%. Additionally, mineral grains and pore throats in Boise Sandstone are cemented with quartz, which is not susceptible to dissolution at these conditions. Our results indicate that humidity in scCO 2 plumes is unlikely to sustain chemical reactions and induce long term strength changes in quartz cemented sandstones due to resistant mineralogies and low water solubility.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Influence of geochemical reactions on the creep behavior of Mt. Simon sandstone

The capture and subsurface storage of carbon dioxide is a sustainable option that is currently pursued worldwide to mitigate greenhouse gas effect. However, predicting the long-term mechanical integrity of CO 2 underground storage systems remains a challenge. To address that question, it is essential to understand the influence of fluid-rock chemo-mechanical interactions on the long-term and on the time-dependent mechanical properties. In turn, the long-term mechanical response and the time-dependent mechanical behavior can be represented by the creep response. We investigate the impact of CO 2 -induced geochemical reaction on the creep response of Mt. Simon sandstone with a 50–400 micron grain size. We perform static and dynamic flow experiments on Mt. Simon sandstone specimens under geological conditions, at a temperature of T = 50 - 53 °C and for CO 2 pressures of P = 8:62; 17:2 MPa under both static flow and dynamic flow-through conditions. After aging, we employ creep indentation testing, high-resolution SEM-EDS, computer vision, machine learning, and micromechanics modeling to probe changes on the microstructure and mechanical properties. Following both static and dynamic flow-through experiments, we observe a 10–22% decrease in quartz volume fraction and an increase in both the microporosity (7–28%) and nanoporosity (60–65%). Additional CO 2 -induced microstructural changes include an enlargement of pore throats and the formation of channels. These observations point to the presence of CO 2 -induced K-feldspar dissolution and clay dissolution reactions. Here, the macroscopic creep behavior is logarithmic and the macroscopic creep modulus varies depending on the microporosity and the relative quartz and feldspar content. As a result of these geochemical reactions and of the related microstructural changes, a 55-60% decrease in the macroscopic logarithmic creep modulus is predicted.

58 GEOSCIENCES↗
DOE OSTI2026

Basin-scale analysis of Mokelumne River Formation for multi-well CO 2 injection

Large-scale carbon sequestration will likely require multiple projects injecting CO 2 into the same subsurface formation, raising concerns about safe operation and efficient use of storage capacity. This study evaluates the long-term response of the Mokelumne River Formation in California’s Sacramento Basin to multi-megaton CO 2 injection using three geologic models of the formation and the open-source simulator GEOS. The analysis focuses on three aspects of reservoir performance: (1) average pressure increase and dissolved CO 2 mass after 30 years for varying well counts and injection rates, (2) pressure interference in a multi-well configuration, and (3) dynamic storage capacity with identification of overpressure-prone regions. The results show that average formation pressure increases linearly with injected mass, while CO 2 dissolution exhibits mixed scaling: approximately linear with the number of wells but sublinear with injection rate, indicating that distributing injection across more wells enhances dissolution more effectively than increasing per-well rates. Pressure-interference effects are significant, with lower-permeability conditions delaying their onset but amplifying their magnitude at later times. Dynamic capacity, defined by the first occurrence of pressure exceeding the local overburden-based limit anywhere in the formation, varies across geologic models and assumed overburden pressure gradients. A lower fidelity geologic model predicts nearly twice the storage capacity of the two higher fidelity models, which consistently estimate approximately 1 Gt under the upper-bound overburden pressure gradient considered for the Sacramento Basin. In all model scenarios, overpressure develops away from injection wells, particularly in higher-elevation regions, highlighting the importance of basin-scale modelling for identifying risks beyond the immediate well vicinity.

Basin-scale↗
DOE OSTI2022

Optimization of screw design for continuous wet granulation: A case study of metoprolol succinate ER tablets

This study aimed at understanding the effect of screw design on the critical characteristics of granules and tablets of an extended-release (ER) formulation for twin screw granulation process. The screw design parameters assessed included number of kneading elements (KEs) per kneading zone, distance separating kneading zones, staggering angle (SA) of kneading elements and number of sizing elements (SEs). These input variables were varied using a design of experiment (DoE) approach to manufacture granules. Particle size distribution (PSD), flow and bulk properties of the granules, breaking strength and dissolution of tablets manufactured using these granules were characterized. The results of least square fitting showed that KEs, SA, and SEs of the screws significantly (p -values < 0.05) affected the PSD, cohesion, compressibility (CPS), conditioned bulk density (CBD) and permeability of the granules. The KEs and SEs significantly (p -value < 0.05) affected the dissolution, which was attributed to their effects on CPS and CBD of the granules. The distance between kneading zones had no significant effect on granules and tablet characteristics. Finally, these results may be used to further study the interaction of the identified critical screw design parameters with other processing parameters for continuous manufacturing of this ER matrix-based tablet formulation.

60 APPLIED LIFE SCIENCES↗