Two infiltration experiments using a fractured gneiss core were performed to address the reactivity of this crystalline rock (host rock for the Finnish geological repository for spent nuclear fuel). The core was 5 cm in diameter and 6.2 cm in length, with fracture opening values up to 1.1 mm. Mineralogy and fracture volume were characterized by X-ray diffraction and X-ray computed microtomography, respectively. Groundwater from the site (dominated by Cl-Na-Ca, pH 7.26, ionic strength 0.22 molal) was injected in the first experiment, while milli-Q water (pH 6.05) was used in the second one. Both solutions were at equilibrium with the atmosphere, and the experiments were performed at room temperature. Flow rates were about 0.005 mL/min.
The results (evolution of outlet solution chemistry) were interpreted by 1D and 2D reactive transport modeling using the CrunchFlow code. The 1D model included flow, solute transport and reaction only along the fracture. Very large mineral surface areas, much larger than the exposed areas on the fracture surfaces, were needed to reproduce the experimental results. To address this issue a 2D model was developed, which also included diffusive transport and reactions in the rock matrix. The 2D model did not need the large surface areas in the fracture to match the experimental results. These results show the important role that rock matrix plays in the overall reactivity of the fractured rock, despite the small porosities (of the order of 1%) and effective diffusion coefficients (of the order of 10-13 m2/s). However, the 1D approach could still prove useful for large repository-scale calculations, given appropriate calibration.
How to cite: Soler, J. M., Cama, J., Silva, O., and Lamminmäki, T.: Fracture vs. matrix reactivity in a tight crystalline rock. Modeling of a fractured-gneiss core infiltration experiment., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7947, https://doi.org/10.5194/egusphere-egu25-7947, 2025.
Flow through porous media involving precipitation and dissolution reactions exhibits a unique feedback behavior between the velocity field and solute transport. In this presentation, we report the findings of a study exploring the relationship between a gradually increasing degree of precipitation and the occurrence of anomalous transport (i.e., transport that cannot be quantified by the advection-dispersion equation). Gypsum was precipitated incrementally in 60 cm long, saturated, sand-packed columns, and an inert tracer was injected between precipitation phases, yielding breakthrough curves (BTCs) as functions of an increasing degree of precipitation. Continuous time random walk particle tracking simulations were used to model these BTCs and quantify the evolution of anomalous transport. Results show an increasingly high degree of anomalous transport following precipitation, while the manner in which the increase manifested varied among duplicate experiments. Two major consistent trends were an increase in the overall BTC widths (i.e., elution time windows) and progressively heavier BTC tailing, as indicated by the steepness of the slope from each BTC peak to the point where it drops below a threshold concentration. Under the current experimental conditions, the effects of precipitation were strikingly similar to those found previously for dissolution, including early BTC onset, peak splitting, and heavier BTC tailing. Finally, the range of transport behaviors among heterogeneous natural systems might be significantly greater than that found in our work for three homogeneously-packed columns.
How to cite: Cohen, M., Dror, I., and Berkowitz, B.: Evolution of anomalous transport following precipitation in porous media, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1169, https://doi.org/10.5194/egusphere-egu25-1169, 2025.
Mineral replacement processes often involve coupled dissolution-precipitation reactions, where a primary mineral is replaced by a secondary one. These transformations are governed by strong, nonlinear interactions among chemical reactions at rock surfaces, evolving pore geometries, and the development or closure of flow pathways. Maintaining a steady influx of reactants and efficient removal of products is crucial for sustaining reaction progression, but issues such as passivation layer formation or flow channel blockage by precipitates frequently disrupt this balance. This problem is particularly relevant in the context of mineral trapping of CO₂, where chemical reactions lead to an increase in solid volume. Consequently, determining optimal injection rates becomes crucial for enhancing the efficiency of the process. To address these challenges, we propose a numerical framework designed to simulate hydrochemical transformations within porous media.
In our simulations, we examine a medium infiltrated by a reactive fluid that triggers coupled dissolution-precipitation reactions at pore surfaces. We model the porous medium as a system of interconnected pipes [1], with the diameter of each segment changing depending on the local consumption of reactants. We incorporate nonlinear kinetics of chemical reactions into the model and assess the impact of inlet reactant concentrations on the behavior of the system. During evolution, we also modify the network topology by merging connections when pore distances are comparable to pore sizes and by cutting connections when pores become clogged.
We explore possible dissolution-precipitation regimes in search of parameters optimal for mineral replacement. By varying the flow rate and the concentrations of injected species, we analyze the emergent patterns to construct a morphological diagram. We benchmark the results against experimental data on calcium carbonate dissolution and gypsum precipitation [2]. We are particularly interested in regimes with oscillating permeability, where the reaction is self-limiting—precipitates clog the pores, but the system continually creates new flow pathways, maintaining reaction progress. We quantitatively characterize various evolution regimes, measuring the volume of replaced mineral and assessing the development of flow pathways [3]. Through this analysis, we identify a region in the space of injection parameters that maximizes mineral replacement.
[1] A. Budek and P. Szymczak, Physical Review E, 86, 056318, 2012.
[2] O. Singurindy and B. Berkowitz, Water Resources Research, 39, 1016, 2003.
[3] T. Szawełło, J. D. Hyman, P. K. Kang, and P. Szymczak, Geophysical Research Letters, 51, e2024GL109940, 2024.
How to cite: Szawełło, T. and Szymczak, P.: Optimizing injection parameters in mineral replacement systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-411, https://doi.org/10.5194/egusphere-egu25-411, 2025.
As conventional oil and gas production declines, global exploration and development efforts have shifted towards unconventional oil and gas resources, with tight volcanic reservoirs emerging as a primary focus. The tuffaceous rocks of the Dehui Fault Depression in the Songliao Basin, characterized by fine-grained volcanic ash deposits, have undergone diagenetic modifications, resulting in low porosity and low permeability with complex pore structures. Identifying the main controlling factors of high-quality reservoir formation and understanding the mechanisms behind secondary pore formation are critical areas of research that require urgent attention.
The study provides several key insights: (1) It identifies the main types of diagenetic processes in the reservoir and establishes a diagenetic evolution sequence. The formation of high-quality reservoirs is primarily controlled by "dual phases" (lithofacies and depositional facies), which includes both pore preservation and enhancement. Acidic dissolution is identified as the primary cause of secondary pore development, with the mechanism of acidic dissolution and its three necessary conditions being discussed; (2) An innovative technique combining large-view stitching and human-computer interaction for thin-section identification images has been developed. This technique establishes a face porosity-porosity model, accurately quantifying the impact of various diagenetic processes on reservoir physical property and identifying the main factors controlling these properties. A porosity evolution history map is created using a combination of back-stripping inversion and computer image analysis techniques. Simultaneously combining chemical kinetics models and fluid inclusion identification to determine the reservoir formation period, clarifying the reservoir-diagenesis coupling characteristics; (3) Methods for distinguishing volcanic eruption periods and identifying lithofacies are established, revealing the main lithologies and depositional characteristics of different eruption periods. The advantageous lithofacies, periods and their distribution characteristics are ultimately determined
Figure: Attached Figure Large Visual Field Splicing and Quantitative Characterization of the Dissolution of Huoshiling Formation in Dehui Fault Depression
How to cite: Liu, L. and Li, J.: Study on the genesis and controlling role of deep and dense volcanic reservoirs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2678, https://doi.org/10.5194/egusphere-egu25-2678, 2025.
Abstract: The micro- and nano-pores in organic-rich shale reservoirs significantly impact the exploration potential of unconventional oil and gas. To clarify the heterogeneity of pore size distribution and its influencing factors in organic-rich shales, this study was conducted on shale cores with significant gas logging anomalies from 1600-1680m, collected from a scientific drilling well in the South Yellow Sea Basin that penetrated the Permian strata. Nitrogen adsorption-desorption experiments, total organic carbon (TOC), X-ray diffraction, and scanning electron microscopy tests were carried out. Additionally, fractal theory was employed to characterize the heterogeneity and connectivity features of the pore structure. The results indicate that the average TOC of the selected samples is 5.99%, and the shale lithofacies are predominantly Siliceous shale, Clay shale, and Clay shale-Clay Mixed shale. The clay shale has the highest average specific surface area and pore volume, with averages of 5.54 m2/g and 9.37×10-3 cm3/g, respectively. The fractal dimensions D1 and D2 calculated using the single Frenkel-Halsey-Hill method are relatively independent. The multifractal box-counting method suggests that low-probability measure areas play a key role in the heterogeneity of the full-size pore size distribution. The generalized fractal dimension D(q) decreases with increasing q, and the singularity fractal spectrum exhibits a non-symmetric parabolic shape, indicating that the pores in organic-rich shales possess multifractal characteristics. An increase in TOC and clay mineral content enhances the overall heterogeneity of the pore structure, while an increase in calcareous mineral content improves pore connectivity. The multifractal model demonstrates a significant advantage in quantitatively characterizing the heterogeneity of pore structures in organic-rich shales, providing an important theoretical basis for shale gas exploration and development.
Key words: Organic-rich shale; Pore structure; Heterogeneity; Monofractal analysis; Multifractal analysis
How to cite: Wei, Z., Liu, H., Pang, Y., and Zhang, J.: The study on fractal theory to characterize the pore structure of organic-rich shale reservoirs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5873, https://doi.org/10.5194/egusphere-egu25-5873, 2025.
We focus on the assessment of spatiotemporal distributions of precipitates in complex porous systems under a variety of sources of uncertainty. Our study specifically targets calcium carbonate (CaCO3) biomineralizing techniques, that are of significant interest across a wide range of engineering applications. In this context, one can note that favoring mineralization can markedly alter the pore space structure as well as hydrodynamic parameters of porous materials. Otherwise, uncertainties surrounding our ability to assess hydraulic and biochemical parameters driving the dynamics of biomineralization treatments can influence the way we quantify the extent of mineral precipitation. Here, we start from a pore scale perspective and rest on a stochastic modeling approach. The latter leverages a combination of (i) a fully coupled biomineralization model based on a pore network model (PNM) and (ii) a surrogate model that enables one to perform numerical Monte Carlo simulations at a reduced computational cost. Our surrogate model relies on a classical polynomial chaos expansion approach. We consider the biomineralization model described by Qin et al. (2016) and perform geochemical speciation through the open-source PHREEQC module. The surrogate model is constructed on the basis of numerical results stemming from the full biomineralization model and is here employed to perform global sensitivity studies and uncertainty quantification analyses. Our results enable one to identify the relative importance of four design (or control) quantities (i.e., (i) injected biomass concentration, (ii) initial biofilm across the pore space, (iii) pressure difference between inlet and outlet of the porous medium, and (iv) injected urea concentration) and of the initial distribution of pore sizes across the domain on (a) volume fraction of precipitates within the host porous medium (in terms of total amount and preferential location within pores of given size) and (b) permeability reduction of the overall porous medium after biomineralization. Global sensitivity analyses reveal that the volume fraction of precipitates is strongly influenced by biomass and urea concentrations. These quantities are associated with a strong positive correlation with precipitate volumes. Our results can form the basis to inform model calibration under uncertainty, thus providing a robust foundation for optimizing biomineralization strategies in engineering applications.
Reference:
Qin, C.-Z., Hassanizadeh, S. M., & Ebigbo, A. (2016). Pore-scale network modeling of microbially induced calcium carbonate precipitation: Insight into scale dependence of biogeochemical reaction rates: pore-scale network modeling of MICP. Water Resources Research, 52(11), 8794–8810. https://doi.org/10.1002/2016WR019128.
How to cite: Yang, Z., Guadagnini, A., Riva, M., Dou, Z., Qin, C., and Wang, J.: Surrogate modeling and global sensitivity analysis for biomineralization in porous media, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6968, https://doi.org/10.5194/egusphere-egu25-6968, 2025.
Subsurface transport takes place in a heterogenous and dynamic network of pores, solids, interfaces, and biota that share a complex topology and create a multitude of migration pathways for fluids and their constituents, i.e., the total mobile inventory (TMI). Owing to the highly variable reactivity of different fractions of the TMI towards biogeochemical interfaces provided by associations of minerals, organic matter and biota, characteristics of the transport regime mainly express in response to the availability and exposition of reactive interfaces. We exploit the rich possibilities of polymer synthesis to design a library of reactive, organic polymers that can represent specific fractions of the TMI regarding their size or reactivity and serve as non-conventional tracers. We show the strong and nearly irreversible adsorption of specific polymers towards unoccupied clay mineral surfaces in column experiments. With that, tailored polymers not only presented as tracers for the transport of organic colloids, but also as sensitive interfacial tracers for the assessment of clay surface exposition that enable the quantification of available reactive surface area accessible to fluids and constituents transported therein. We also use polymers to label potentially mobile clay mineral colloids and follow their mobility in porous media by tracking polymers being co-transported along with the colloids. We further use polymers to introduce a fluorescent label to reactive mineral sites and localize their relative distribution on rock surfaces using fluorescence microscopy. As polymers can also be subjected to other spectroscopic techniques such as infrared spectroscopy, a tailored synthesis of polymers towards adsorption to specific sites might open a novel perspective on the characterization and mapping of (mineral) surfaces and their functional role in general.
How to cite: Ritschel, T., Kwarkye, N., and Totsche, K.: The versatility of tailored polymers in investigating reactive transport in porous media, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15388, https://doi.org/10.5194/egusphere-egu25-15388, 2025.
Positive feedback between permeability and dissolution during the flow of a matrix-dissolving fluid through porous media can create diverse, evolving structures [1]. The dynamics of this hydrochemical instability depend on both flow rate and the geometric properties of the pore space, leading to a wide range of structures: from intricate, cave-like wormholes to simple surface dissolution patterns.
A variety of petroleum engineering applications led to a significant number of industry-oriented studies, and the effects of flow and reaction rates on wormhole formation are well established [2], however mechanisms governing their propagation dynamics remain poorly understood.
This study investigates the dominant wormhole regime, which has applications in various industrial and natural contexts, including carbon capture and storage. Understanding the dynamics of fluid interaction with the porous matrix requires high-resolution temporal and spatial data. We have recently conducted in-situ X-ray microCT imaging of developing wormholes in dissolving limestone cores flooded with hydrochloric acid, achieving high temporal frequencies (50–100 frames per experiment) [3]. To further improve temporal and spatial resolution, we utilized the ID-19 beamline at the European Synchrotron Radiation Facility. A limestone core was confined in a Hassler cell and flooded with hydrochloric acid, while high-frequency 4D tomographic data tracked the evolving 3D shape of the growing wormhole. The time evolution of the wormhole profile has been compared with an analytical model of the growth of the tube-like dissolution structure [4]. As we show, such data, when properly interpreted, allow for a measurement of the mineral dissolution rate constant and the assessment of the impact of diffusive transport on the dissolution process.
[1] Hoefner, M.L. and Fogler, H.S., 1988. Pore evolution and channel formation during flow and reaction in porous media. AIChE J., 34, pp.45-54
[2] Golfier, F., Zarcone, C., Bazin, B., Lenormand, R., Lasseux, D. and Quintard, M., 2002. On the ability of a Darcy-scale model to capture wormhole formation during the dissolution of a porous medium. J. Fluid Mech., 457, pp.213-254
[3] Cooper, M.P., Sharma, R.P., Magni, S., Blach, T.P., Radlinski, A.P., Drabik, K., Tengattini, A. and Szymczak, P., 2023. 4D tomography reveals a complex relationship between wormhole advancement and permeability variation in dissolving rocks. Advances in Water Resources, 175, p.104407
[4] Budek, A. and Szymczak, P., 2012. Network models of dissolution of porous media. Phys. Rev. E 86, 056318.
How to cite: Dzikowski, M., Szymczak, P., Woś, D., Majkut, M., and Kosiński, T.: Insights from high-speed in-situ imaging of wormhole growth in limestone cores., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18392, https://doi.org/10.5194/egusphere-egu25-18392, 2025.
Chemical weathering carves earth surface by elemental mobilisation and supergene enrichment. Laterization is one of such process. Laterites result from intense chemical weathering, dominantly in tropical and subtropical climates. Leaching of mobile elements results concentration of iron (Fe) and aluminum (Al) as oxides or oxyhydroxides. The selective mobilization and retention of immobile elements during extreme weathering provides valuable proxies for paleoenvironmental investigations. The enrichment of immobile elements (Fe and Al) in laterite is a dichotomy needing deeper mechanistic insights to understand the origin. To investigate the mechanism of elemental mobilisation and enrichment near earth surface, multiple sets of experiments have been conducted in this study. The effect of drainage conditions and organic ligands of soil have been investigated. Custom made experimental setup of rock leaching significant amount of iron mobilisation with oxalic acid, reaching upto 0.175 mg per day from 1 gm of basalt. SEM and TEM investigation of solid precipitates from the leachants confirmed amorphous Fe-phases. Deeper investigation from molecular perspective using X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared spectroscopy (FTIR) are under progress to unveil the mineralogical mysteries with implication towards lateritisation. Furthermore, the integration of reactive transport modeling into these experimental frameworks aims to enhance our understanding of the diverse phases and associated complexes formed during weathering, thereby providing critical insights into paleoenvironmental conditions. This approach will also facilitate the simulation, how various factors influence elemental mobility and enrichment in lateritic profiles.
How to cite: Harbola, D. and Mathew, G.: Unraveling the Mechanisms of Elemental Mobilization and Supergene Enrichment in Lateritization: An Experiment Study, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16222, https://doi.org/10.5194/egusphere-egu25-16222, 2025.
Hydration of anhydrite with substitution of strontium (Ca,Sr)SO4 - model experiments
Martyna NAWRACAJ1, Julia RÓŻAŃSKA1, Kacper STASZEL1, Bartosz PUZIO1, Aleksandra PUŁAWSKA1, Maciej MANECKI1
1Department of Mineralogy, Petrography and Geochemistry, AGH University of Kraków, al. Mickiewicza 30, 30-059 Kraków, Poland
Infiltration of fresh water into the clay-anhydrite layers of the salt deposit (Bochnia Salt Mine, UNESCO World Heritage Site in southern Poland) results in the hydration of anhydrite (CaSO₄) to gypsum (CaSO₄·2H₂O) (Pitera and Cyran, 2008). This process is particularly complex and unusual because the parent anhydrite is partially substituted with Sr (0.1-0.2%, Pulawska et al., 2021), and the release of strontium during this transformation remains unclear.
To investigate this phenomenon, laboratory model experiments were performed. Synthetic analogs of Sr-substituted anhydrite with varying Sr content (0.1%, 1%, as well as 2%) were prepared, along with pure anhydrite and celestine (SrSO₄). All five syntheses were conducted for 3 hr at 120°C (Kamarou et al., 2021) and resulted in formation of Sr-doped anhydrite. A maximum Sr substitution in anhydrite was established at 1–2 wt.%. Synthetic sulfates were hydrated for 70 days in a controlled environment, using 500 mL of redistilled water with 2.5 g of solid material (1:10 solution-to-solid ratio). The solids were analyzed using powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). The phase transformations began as early as 21 days in both pure and 0.1% Sr-substituted anhydrite, forming bassanite (CaSO₄·0.5H₂O). Later on, the hemihydrate sulfate transformed into gypsum. Pure celestine did not undergo any phase transformation during the hydration process.
Model hydration experiments have successfully mirrored the natural phenomenon occurring in the Bochnia Salt Mine, including the release of strontium into solution. These findings leave the room for further research so as to understand the fate and influence of strontium on minerals in salt deposits.
References
- Kamarou, M., Korob, N., Hil, A., Moskovskikh, D., Romanovski, V. (2021). Low-energy technology for producing anhydrite in the CaCO3–H2SO4–H2O system derived from industrial wastes. Journal of Chemical Technology & Biotechnology, Vol 96, issues 7, p. 2065-2071
- Pitera, H., Cyran, K. (2008) Altered anhydrite from Bochnia Salt Mine (Poland). Geologia, Vol 34, issue 1, p. 5–17 (in Polish)
- Puławska, A., Manecki, M., Flasza, M., (2021). Mineralogical and Chemical Tracing of Dust Variation in an Underground Historic Salt Mine. Mineralas, 11, 686
How to cite: Nawracaj, M., Różańska, J., Staszel, K., Puzio, B., Puławska, A., and Manecki, M.: Hydration of anhydrite with substitution of strontium (Ca,Sr)SO4 - model experiments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-702, https://doi.org/10.5194/egusphere-egu25-702, 2025.
Reactive transport is a phenomenon resulting from the interaction and coupling of solute transport and chemical reactions. A new method to solve reactive transport known as Water Mixing Approach (WMA) was introduced by Soler-Sagarra et al. (2022). The idea is to interpret solute transport as water mixing and advection, where diffusion and dispersion are simulated as water exchange instead of Fickian solute flux. The WMA has the advantage of decoupling transport and chemistry. Transport computations are restricted to the evaluation of mixing ratios. This way, reactive transport computations are restricted to reactive mixing calculations, which can be performed separately for every target (node, cell, or particle, depending on the approach adopted to simulate transport). This facilitates parallelisation. However, the original work only considered the explicit case, which is conditionally stable and therefore requires artificial values of the dispersion coefficient to avoid numerical instabilities. We present a formulation of the WMA that is implicit both in transport, to ensure stability, and in chemical reactions to be able to simulate fast reactions. The implicit formulation requires lumping the reactive term. We test the validity of the approach by comparison with analytical solutions and the Direct Substitution Approach (DSA) method in a case with 2 adjacent mineral zones in equilibrium, and in a denitrification case with two redox reactions. We find that the proposed approach is extremely efficient and accurate for small dispersion cases.
How to cite: Petchamé-Guerrero, J., Carrera, J., and Wang, J.: The fully implicit water mixing approach for the efficient simulation of reactive transport, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20380, https://doi.org/10.5194/egusphere-egu25-20380, 2025.
The conversion of ferrous iron to ferric iron during water-rock interaction generates molecular hydrogen, a process well-documented in the serpentinization of ultramafic rocks. However, the hydrogen production potential of basaltic rocks remains underexplored, despite their wide distribution and high iron and magnesium content. This study evaluated the hydrogen generation capacity of basaltic rocks through laboratory-scale water-rock interaction experiments using basaltic specimens from the Korean Peninsula. Experiments were conducted in a titanium autoclave at 280°C for up to 14 days. Molecular hydrogen production was measured using gas chromatography equipped with thermal conductivity detector (GC-TCD, FOCUS GC, Thermo Fisher Scientific), and whole-rock chemistry was analyzed using inductively coupled plasma optical emission spectroscopy (ICP-OES, Optima 7000DV, PerkinElmer), both installed at the Integrated Analytical Center for Earth and Environmental Sciences of Pukyong National University, while mineralogical changes were examined using scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). Hydrogen production varied significantly across samples. OSB-1A showed delayed hydrogen generation, reaching 51.22 mmol/kgrock at 336 hours. In contrast, OSB-1B exhibited rapid and sustained hydrogen production, peaking at 115.04 mmol/kgrock. ULD-2 demonstrated the highest hydrogen yield (182.54 mmol/kgrock at 336 hours), while other samples such as YI-1 and EI-1 produced lower amounts with delayed onset. SEM-EDS analysis confirmed the dissolution of Fe-bearing minerals associated with abiotic hydrogen production, but no secondary Fe-bearing minerals like magnetite or brucite were detected. Instead, nanoscale amorphous precipitates were observed, likely due to the preferential involvement of fine-grained particles with high surface areas in hydrogen production. These findings enhance our understanding of abiotic hydrogen production in basaltic rocks and its implications for geochemical processes and potential energy resources.
How to cite: Jeong, S., Ko, K., Kim, M. G., and Yang, M.: Experimental Investigation of Hydrogen Generation and Mineralogical Changes in Basaltic Rocks , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7963, https://doi.org/10.5194/egusphere-egu25-7963, 2025.
Solution pipes—vertical, cylindrical voids in karst terrains—are enigmatic geomorphic features whose formation mechanisms remain poorly understood. These structures exhibit spatial distributions suggesting self-organization processes. To test this hypothesis, we analyzed the spatial arrangements of solution pipes from Australia and the Mediterranean region. We quantified spatial patterns through metrics such as the radial correlation function, angular order parameter, and Voronoi tessellation. The results reveal non-random distributions consistent with self-organization, driven by feedback mechanisms involving dissolution dynamics and localized groundwater flow. These findings support the idea that self-organization plays a critical role in the development of solution pipes and offer new insights into the processes driving karst landscape evolution on a global scale.
How to cite: Waligórska, M., Kurek, M., Woś, D., Lipar, M., and Szymczak, P.: Self-Organization in Solution Pipe Patterns: A Comparative Study from Australia and the Mediterranean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-317, https://doi.org/10.5194/egusphere-egu25-317, 2025.
The Upper Rhine Graben in Germany is characterized by a heat anomaly and numerous normal faults crossing permeable sedimentary formations. These complex geothermal and hydrogeological conditions present both risks and opportunities for the geothermal exploration and development. Within the DEKAPALATIN-BERTHA project, located in the city of Wörth, Germany, we focus in the first phase on the understanding the controls on the thermal anomaly through dynamic numerical modelling. Besides, highly saline brines are well known to interact with the host rock in operating geothermal projects in the Upper Rhine Graben. However, this rock-fluid interaction during geothermal operation in not well elucidated quantitatively.
Thermo-hydro-chemical (THC) coupling in geothermal reservoirs refers to the interrelated processes of heat transfer, fluid flow, and chemical reactions within the subsurface environment. This coupling has a significant impact on the hydrodynamic properties of the reservoir, as temperature changes can alter fluid viscosity and density. At the same time, chemical reactions can alter porosity and permeability through mineral dissolution and precipitation. Understanding and modelling THC interactions is critical for predicting reservoir behavior, optimizing energy recovery, and ensuring the long-term sustainability of geothermal operations. Incorporating THC processes into simulations improves the accuracy of predictions of fluid movement and heat distribution within geothermal systems.
Based on the 3D regional, structural GeORG model, we have built a 3D dynamic model capable of simulating coupled processes. Based on published data on the local hydrogeological stratification, we have resolved target formations such as the Muschelkalk and Middle Buntsandstein in detail. In addition, a gradual complication approach is adopted to investigate the key controlling factors on the heat anomaly. A series of THC numerical models at different scales have been developed prior to the laboratory experiments (µ-CT 3D scan and core flooding) for the optimal experimental setup. In this work we present our latest results.
How to cite: Meneses Rioseco, E., Abdelmoula, M. O. I., Lee Exuzian, G., and Moeck, I.: Thermo-hydro-chemical modelling at the field- and lab-scales for a sustainable geothermal energy production in the Upper Rhine Graben – Geothermal project DEKAPALATIN-BERTHA, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16314, https://doi.org/10.5194/egusphere-egu25-16314, 2025.
Understanding the long-term evolution of groundwater in high-level radioactive waste (HLW) disposal sites is crucial for identifying radionuclide migration pathways, assessing environmental impacts, and ensuring long-term stability. This study evaluates the applicability of non-conventional methods, such as metal isotope analysis, in understanding the geochemical long-term evolution of groundwater. Groundwater and rock core samples were collected from boreholes at the Korea Atomic Energy Research Institute’s Underground Research Tunnel (KURT) site. To evaluate the geochemical characteristics and changes in lithium isotope (δ⁷Li) composition in the samples, the lithium isotope analysis was performed alongside the principal component analysis (a traditional method). The extent and intensity of chemical weathering were revealed through comparative analysis of the δ⁷Li content changes in groundwater and rock cores, which could ultimately be interpreted in connection with the groundwater residence time. It was revealed that primary mineral dissolution during the early stages of weathering did not significantly affect the δ⁷Li values in the groundwater but secondary mineral formation resulting from prolonged weathering was a factor in increasing the δ⁷Li values in the groundwater and decreasing the δ⁷Li values in the rock cores. Therefore, the δ⁷Li analysis is believed a useful tool to provide insights into primary mineral dissolution, secondary mineral formation, and subsequent re-dissolution processes driven by water-rock interactions. δ⁷Li analysis could be utilized for understanding the geochemical evolution characteristics of disposal environments and for evaluating the safety of deep geological disposal.
Acknowledgements
This research was supported by the National Research Foundation of Korea(NRF) under the project 'Development of Core Technologies for the Safety of Used Nuclear Fuel Storage and Disposal; NRF-2022M2E1A1052570'.
How to cite: Ahn, J., Lee, I., Park, J., and Yi, M.: Study on Geochemical Characteristics Evaluation Through Lithium Isotope Analysis for Long-Term Evolution of Groundwater in High-Level Radioactive Waste Disposal Sites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16342, https://doi.org/10.5194/egusphere-egu25-16342, 2025.
Carbon capture and storage (CCS) has emerged as a key strategy in mitigating anthropogenic greenhouse gas emissions. By capturing CO₂ from industrial sources and storing it in deep geological formations, CCS offers a pathway to reduce atmospheric CO₂ concentrations. The success of CCS relies on understanding fluid-mineral interactions, reactive transport processes, and the long-term stability of geological storage systems. This study investigates mineral dissolution in acidic environments using numerical simulations as a foundation for reactive transport modeling in geological systems. The research focuses on developing and validating computational methods that can accurately predict the behavior of minerals exposed to acidic conditions, similar to those encountered in CO2 storage scenarios. In this study, ANSYS Fluent was employed to simulate the dissolution of calcite (CaCO3), serving as a representative mineral for the methodology due to its abundance in potential storage formations and well-documented reaction kinetics. The numerical setup comprises a rectangular domain with a centrally positioned circular mineral sample, allowing detailed observation of dissolution patterns and fluid flow characteristics. The fluid enters the domain with a defined H⁺ ion concentration, triggering a chemical reaction, CaCO3(s) + H⁺ → Ca²⁺ + HCO3-. The simulation incorporates multiple physical and chemical processes, including advection, diffusion, and surface reactions. A comprehensive mesh sensitivity analysis ensures numerical accuracy and solution independence. The study evaluates the spatial and temporal evolution of ion concentration distributions and reaction rates. The numerical results are verified and validated against numerical and experimental data from the literature. The developed methodology includes a detailed consideration of boundary conditions, numerical schemes, and convergence criteria. While focused on calcite, the framework is adaptable to other minerals and reaction systems. The research addresses common challenges in numerical modeling of dissolution processes, such as handling moving boundaries and accurately representing reaction kinetics. The results provide insights into the fundamental mechanisms controlling mineral dissolution under acidic conditions. Analyzing concentration profiles and reaction rates helps identify rate-limiting steps and optimal conditions for dissolution processes. These findings directly impact understanding the porosity and permeability evolution in geological formations exposed to CO₂ rich fluids. This study establishes a foundation for more complex investigations involving multiphase systems and geological storage scenarios. The methodology can be extended to study various aspects of CCS implementation, from reservoir-scale simulations to detailed analysis of wellbore integrity. By advancing our understanding of fluid-mineral interactions and providing validated numerical tools, this research contributes to developing effective storage systems and risk minimization strategies, ultimately supporting CCS's role in global greenhouse gas reduction efforts.
How to cite: Nascimento Telöken, K., Klunk, M. A., Augustin, A. H., Serrat, H., Girelli, T. J., and Chemale Jr, F.: Numerical Modeling of Mineral Dissolution in Acidic Environments: A Step Towards Advancing CCS Applications , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20876, https://doi.org/10.5194/egusphere-egu25-20876, 2025.
In the Baiyun Sag of the Pearl River Mouth Basin (PRMB), the oil and gas exploration targets have graduallyshifted from the conventional reservoirs in the shallow to moderately deep Hanjiang-Zhujiang formations to the lowpermeability, tight reservoirs in the deep to ultra-deep Zhuhai-Enping formations. Due to their distinct geological setting of highly variable geothermal gradients, the low-permeability, tight reservoirs exhibit significantly different diagenesis and tightening mechanisms from the conventional reservoirs. Using techniques such as casting thin section observation, scanning electron microscopy (SEM), physical property tests, diagenetic reconstruction, and physical property restoration, we systematically analyze the diagenetic processes of the Paleogene sandstone reservoirs from the Zhuhai Formation’s lower member to the Enping Formation in the area from the northwestern low uplift to the central sub-sag zone in the Baiyun Sag and their disparities. Considering the tectonic evolution setting, stratigraphic burial history, and current physical property data, we investigate the major factors influencing the relationships among the reservoirs’ physical properties and explore their tightening processes and mechanisms. The results suggest that the reservoirs from the Zhuhai Formation’s lower member to the Enping Formation have experienced intense compaction, two-stage carbonate cementation, three-stage siliceous cementation, and three-stage feldspar dissolution. During their diagenetic processes, the reservoirs exhibited varying compaction rates due to changes in geothermal gradients and underwent water-rock interactions in different open-closed systems. These are major reasons for the different physical properties of the reservoirs across various tectonic zones in the Baiyun Sag. Compaction emerged as the primary factor leading to the reservoir tightness, which was further enhanced by siliceous and carbonate cementation. In contrast, dissolution improved the physical properties of the reservoirs. From the lowuplift to the sub-sag zone, strata from the Zhuhai Formation’s lower member to the Enping Formation exhibited increasing geothermal gradients and burial depths. Accordingly, their reservoirs in the low uplift, slope zone, and sub-sag zone are in the middle diagenetic stage A2, middle diagenetic stage B, and late diagenetic stage, respectively, with diagenetic intensity gradually increasing. The diagenetic variations significantly impacted the evolution of the reservoirs’physical properties. Specifically, the reservoirs in the sub-sag zone had become tight prior to the late-stage hydrocarbon charging, while those in the slope zone underwent a gradually tightening process during this period.
How to cite: Zhao, X., Yuan, G., and Peng, G.: Mechanisms of Rock-Fluid Interactions on Reservoir Low-Permeability and tightening in the Paleogene of the Baiyun Sag, Pearl River Mouth Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1500, https://doi.org/10.5194/egusphere-egu25-1500, 2025.
The hyporheic zone (HZ), a critical interface between surface water and groundwater, plays a key role in controlling water quality, nutrient cycling, and ecosystem resilience. This study quantitatively investigates the depth and hydrochemical stability of the HZ in contrasting geological settings—a limestone-dominated upstream and a gneiss-dominated downstream region—using hydraulic gradient measurements, temperature profiles, and hydrochemical data collected across four seasons (spring, summer, fall, winter) between 2021 and 2022. Key parameters, including hydraulic gradients (dh/dl), temperature, and Saturation Index (SI), were collected seasonally from a representative streambed. The study incorporated δ18O, δD and δ13C isotopic data to determine mixing ratios between surface and groundwater and their effects on the HZ boundary dynamics. Advanced numerical modeling, including Darcy’s law and heat transfer equations, was employed to delineate the spatial and temporal variability of the HZ. Our results reveal a significant correlation between seasonal shifts in hydroclimatic factors (precipitation, evaporation, and temperature variability) and HZ, demonstrating its dynamic nature. Increased precipitation during the wet season enhanced mixing processes, resulting in elevated SI values and potential carbonate mineral saturation, while the dry season exhibited reduced mixing and undersaturation conditions. These findings suggest that seasonal hydroclimatic factors profoundly influence the chemical and physical stability of the HZ, impacting water resource management and ecosystem resilience.
This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (grant numbers 2019R1A6A1A03033167). This subject is supported by Korea Ministry of Environment as "The SS(Surface Soil conservation and management) projects; 2019002820004.
How to cite: Kim, H., Ryu, H.-S., Yang, J.-E., Moon, J., Khant, N. A., Lumongsod, R. M., San, A., and Lee, M.: Quantifying Hyporheic Zone and Hydrochemical Stability under Seasonal Variability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3044, https://doi.org/10.5194/egusphere-egu25-3044, 2025.
