Geological Information Research Articles

Laboratory Studies on Underground H2 Storage: Bibliometric Analysis and Review of Current Knowledge

The global demand for energy and the need to mitigate climate change require a shift from traditional fossil fuels to sustainable and renewable energy alternatives. Hydrogen is recognized as a significant component for achieving a carbon-neutral economy. This comprehensive review examines the underground hydrogen storage and, particularly, laboratory-scale studies related to rock–hydrogen interaction, exploring current knowledge. Using bibliometric analysis of data from the Scopus and Web of Science databases, this study reveals an exponential increase in scientific publications post-2015, which accounts for approximately 85.26% of total research output in this field and the relevance of laboratory experiments to understand the physicochemical interactions of hydrogen with geological formations. Processes in underground hydrogen storage are controlled by a set of multi-scale parameters, including solid properties (permeability, porosity, composition, and geomechanical properties) and fluid properties (liquid and gas density, viscosity, etc.), together with fluid–fluid and solid–fluid interactions (controlled by solubility, wettability, chemical reactions, etc.). Laboratory experiments aim to characterize these parameters and their evolution, simulating real-world storage conditions to enhance the reliability and applicability of findings. The review emphasizes the need to expand research efforts globally to comprehensively address the currently existing issues and knowledge gaps.

Organic modes of occurrence and evolution mechanism of germanium and lithium in coal: Insights from density functional theory

Critical elements in coal, such as Ge and Li, recently have attracted attention due to their economic significance. Modes of occurrence of these critical elements are academically and practically important, because they can not only provide evidence for sources of elements and minerals in coal and regional geological background information, but also help with design of recovery methods. However, conventional analytical methods are unable to observe precisely the organic binding sites of Ge and Li in coal, and this limits the understanding of their enrichment mechanism and the improvements for recovery techniques. In this study, organic modes of occurrence and evolution mechanism of Ge4+ and Li+ were investigated at the atom level by constructing molecular models of Ge- and Li-rich coals combined with density functional theory (DFT) methods. The solid-state 13C nuclear magnetic resonance spectroscopy (NMR), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and helium pycnometry analyses indicate that the molecular formulas of Ge- and Li-rich coals are C166H162N2O32 and C153H174N2O24S, respectively. The DFT analysis reveals that the binding sites for Ge4+ in Ge-rich coal are located near the carboxyl group (-COOH) and the pyrrole ring, while those for Li+ in Li-rich coal are near the carbonyl group (-C=O) and the pyrrole ring. The Ge4+ is immobilized in the Ge-rich coal molecular model through coordination bonds with the O atom in the -COOH and the C atom in the pyrrole ring, while being away from the N atom in the pyrrole ring. Li+ forms a coordination bond with the O atom in the -C=O and additional coordination bond with the nearby hydroxyl group during binding to the pyrrole ring. The impact of coal rank on the organic modes of occurrence of Ge4+ and Li+ was investigated using Wender coals of different ranks, which were one of the earliest proposed coal models. At the lignite stage, oxygen-containing functional groups and aromatic rings show a strong binding ability to Ge4+ and Li+, facilitating their enrichment in coals. Along with coal rank advance to bituminous coal, the reduction of oxygen-containing functional groups (e.g., -COOH and -C=O) and the relatively low condensation of aromatic rings decrease binding sites for Ge4+ and Li+, and the binding ability also decline, resulting in a decrease in their concentration. In anthracite stage, highly condensed aromatic rings provide binding sites for Ge4+ and Li+. The strong binding ability of aromatic rings to Ge4+ indicates that it is probably enriched in anthracite, whereas Li+ is difficult to enrich owing to its relatively weak binding ability to aromatic rings. The low content of oxygen-containing functional groups in anthracite reduces their effect on the organic modes of occurrence of Ge4+ and Li+. This study elucidates the organic modes of occurrence and evolution mechanism of Ge4+ and Li+ from the perspective of coal structure, providing fundamental insights for future research on the interaction between organic and inorganic matter within coal.

Numerical experiments on hydrogen storage characterization in porous media using elastic full-waveform inversion

In recent years, underground hydrogen storage (UHS) has garnered significant attention as a concept for large-scale energy storage. Developing hydrogen characterization and monitoring methods specific to each target geologic formation (e.g., salt caverns, reservoirs in depleted oil/gas fields, and saline aquifers in porous media) is crucial for the safe operation of hydrogen storage. However, due to the limited number of actual operations and laboratory experiments (e.g., rock physics for hydrogen) related to UHS in porous media, the specifications required for seismic monitoring (e.g., P-/S-wave velocity and density changes generated by hydrogen injection) are not yet fully understood. A recent study showed the results of laboratory experiments on cyclic UHS in porous media. The experiments demonstrated that P-wave velocity decreases nonlinearly with increasing hydrogen saturation in sandstone specimens, with a reduction of up to 3.5% observed at 36% hydrogen saturation. This study presents hydrogen characterization in porous media with conditions similar to the experiment using elastic full-waveform inversion (FWI) for time-lapse surface seismic data. The shot data are generated by seismic forward modeling for several synthetic subsurface models that incorporate a hydrogen plume. The hydrogen plume assumes four velocity-density scenarios, partially based on the laboratory study results. Numerical experiments are conducted to explore the validity and challenges of hydrogen characterization using elastic FWI.

Crack evolution mechanism of stratified rock mass under different strength ratios and soft layer thickness: Insights from DEM modeling

Research on stratified rock masses, which are common geological formations, has primarily focused on their mechanical properties, while studies on crack evolution and microscopic damage mechanisms remain limited. This study addresses this gap by investigating the combined effects of strength ratios and soft layer thicknesses on the microcrack evolution mechanism of stratified rocks using the discrete element method (DEM). Through FISH language programming in the particle flow code (PFC), this study reveals the acoustic emission (AE) characteristics, crack initiation and propagation, damage degree, and final failure characteristics. The key findings are: (1) Higher strength ratios between the hard and soft components of stratified rocks make specimens more sensitive to increases in soft layer thickness. (2) Three types of AE events were identified: continuous active, intermittent active, and silent. (3) Cracks initiate at the interface between components and propagate along the interface into the rock matrix. The strength ratios determine the crack propagation path and the damage extent of the components. (4) The failure of stratified rocks is primarily controlled by the soft component. Crack connections typically form vertical and sub-vertical tensile failure planes in the hard component, and a shear failure surface with a “V”-shaped intersection in the soft component.

Absorption and diffusion process at the CO[formula omitted]-decane interface considering density fluctuations near the critical CO[formula omitted] point

The injection of CO2 into geological formations for storage and for efficiency enhancement of oil production is considered a promising technology. Fundamental is an understanding of the absorption and diffusion process at the CO2-decane interface and its pressure and temperature dependence when approaching the critical CO2 point (31 °C, 7.38 MPa).Based on a new conceptual model, which considers CO2 density fluctuations in the critical range, we were able to consistently explain the time dependence of the volume increase for the respective thermodynamic state. The experimental results confirm the new conceptual model that volume swelling in the non-critical pressure range (< 6 MPa) is a surface effect with limited penetration depth. In contrast, the volume increase in the critical pressure range (6 - 8 MPa) is caused by mixing of liquid CO2droplets and the oil phase, i.e. to a level increase of the liquid mixed phase. Our experimental contact angles confirm this. The measured minimum miscible pressures (MMP) are 5.6 and 6.5 MPa at 20 °C and 30 °C, respectively.The CO2 absorption process at the CO2-decane interface is studied independently with pressure decay experiments. Our model results show excellent agreement (relative error ≅ 1 %) with the experimental results for both the non-equilibrium and equilibrium model, and the early-time diffusion coefficient is 4.7±1.9×10−7m2/s, confirming a fast CO2 mass transfer process.

GEOCHEMICAL CHARACTERIZATION OF ORTHO-DERIVED GNEISS AND GRANITOIDS OF THE PAN-AFRICAN PROVINCE OF DAMAGARAM (SOUTH-EAST NIGER)

The Pan-African province of Damagaram, object of this study, corresponds to the north-eastern extension of the Benin-Nigerian Shield. The main geological formations that outcrop in this region consist of migmatitic gneiss, banded gneiss, mylonitic gneiss, porphyritic granites, two-mica granites, biotite granites and alkaline granites. The petrogenesis of ortho-derived gneisses and granitoids of Damagaram province was studied using the methods of geochemistry on total rock (major elements, trace elements and rare earth elements). The chemical composition (major elements and trace elements) shows that the precursor magmas come from the subalkaline series. The analyzed samples are characterized by a high SiO2 content (≥ 65%) and show a calc-alkaline potassium to shoshonitic affinity typical of the subduction zone. The high alkaline content (Na2O + K2O) and the A/CNK and A/NK parameters indicate that these rocks are aluminous to hyperalumino. Enrichment in certain large lithophilic elements (LILEs) (Rb, Ba, Th and Sr) and depletion in certain high field intensity elements (HFS) such as Nb, P and Ti are favorable criteria for the involvement of the crust in the genesis of these rocks. The light rare earth enrichment (LREE) and heavy rare earth depletion (HREE), as well as the negative europium (Eu) anomaly, suggest that these rocks as a whole would come from either fractional crystallization or partial melting of a pre-existing continental crust. The geochemical characteristics indicate that the geodynamic domain of these formations corresponds to the syn-collisional and intraplate volcanic arc geotectonic environments.

Optimizing hydrogen storage in a heterogeneous aquifer considering hysteresis and dissolution

Hydrogen (H2) is a rising solution for carbon-neutral fuel transition. Saline aquifer, ubiquitous underground, is a competitive candidate for large-scale underground hydrogen storage (UHS). This study proposed to use a heterogeneous aquifer formation for probing the functioning of UHS and optimizing its operation. By integrating geological information with lithofacies from the Ordos Basin in China, a heterogeneous triplet aquifer model was built, upon which compositional simulations of UHS operations that consider two-phase flow, relative permeability hysteresis, hydrogen and water phase behavior, rock compressibility, and dissolution mechanisms were conducted. Orthogonal array L25 (56) with mixed levels was designed to optimize the H2 recovery. Results substantiate the feasibility of storing millions of cubic meters of H2 with over 95% recovery. Ignoring dissolution and relative permeability hysteresis will result in an overestimation of the hydrogen recovery factor, with the effect of relative permeability hysteresis being more significant. Provided equal cycle length, a lower injection-withdrawal rate is suitable for long-term operation of hydrogen storage, while a higher rate can achieve a higher recovery factor during the early cycles. Measures of lowering the skin factor and pre-extracting brine could improve storage capacity and reduce water production during injection and withdrawal. The optimized case is expected to achieve an average H2 recovery of 98.8% for 30 operation cycles with moderately low saline water production. These findings provide valuable insights for developing large-scale and cost-effective UHS in saline aquifers.

Chemical composition of natural waters of the eastern rim of the Siberian platform (Predverkhoyansk foredeep)

Relevance. Foothill (foredeep, pericratonic) deflections play a significant role generation and localization of hydrocarbon accumulations and are promising objects of oil and gas exploration. Numerous studies of such structures are focused mainly on the geological structure, formation and prospects of oil and gas potential of these territories. Issues related to the geochemistry of natural waters are either not covered at all, or are presented in an extremely limited form. Studying the chemical composition of the natural waters of the Predverkhoyansk foredeep at the modern analytical level will make it possible to assess the hydrogeochemical background and emphasize the peculiarities of the behavior of the main components of the aquatic environment in conditions of a sharp change in the tectonic situation. Aim. To study and identify the hydrogeochemical features of the composition of natural waters in the area of the eastern framing of the Siberian platform in the region of its junction with the scaly-thrust dislocations of the Verkhoyano-Kolyma folded zone. Methods. Measurements of rapidly changing parameters of natural waters (pH, Eh, temperature) were carried out directly at the sampling site with a portable HQ-40D analyzer from Hach Lange (USA). The analysis of the chemical composition of waters was carried out in the Problematic Research Laboratory of Hydrogeochemistry of Tomsk Polytechnic University using ion chromatography methods on a two-channel reagentless ionochromatographic complex ICS-5000 with conductometric detection manufactured by Dionex-Thegmo Scientific (USA). The content of CO32– and HCO3–anions in the studied waters was determined by the traditional titrimetry method for these indicators. The Si concentration was determined by inductively coupled plasma mass spectrometry on a NeXION 300D device, Perkin Elmer (USA). Results. The paper presents the data on the chemical composition of the natural waters of the Tompo, Lyapiske, Sobolokh-Mayan (Sobopol) river basins in the inner part of the Predverkhoyansk foredeep in front of the cutting edge of the advanced thrust of the western slope of the Verkhoyansk anticlinorium. The patterns of the distribution of basic ions are shown, common features and differences between the studied sites are revealed.

PPP Solution‐Based Model of Absolute Vertical Movements of the Earth's Crust in Poland With Consideration of Geological, Tectonic, Hydrological and Mineral Information

PPP Solution‐Based Model of Absolute Vertical Movements of the Earth's Crust in Poland With Consideration of Geological, Tectonic, Hydrological and Mineral Information

Comprehensive Comparative Review of the Cement Experimental Testing Under CO2 Conditions

Global warming is presently one of the most pressing issues the planet faces, with the emission of greenhouse gasses being a primary concern. Among these gasses, CO2 is the most detrimental because, among all the greenhouse gasses resulting from anthropogenic sources, CO2 currently contributes the largest share to global warming. Therefore, to reduce the adverse effects of climate change, many countries have signed the Paris Agreement, according to which net zero emissions of CO2 will be achieved by 2050. In this respect, Carbon Capture and Sequestration (CCS) is a critical technology that will play a vital role in achieving the net zero goal. It allows CO2 from emission sources to be injected into suitable subsurface geological formations, aiming to confine CO2 underground for hundreds of years. Therefore, the confinement of CO2 is crucial, and the success of CCS projects depends on it. One of the main components on which the confinement of the CO2 relies is the integrity of the cement. As it acts as the barrier that restricts the movement of the sequestrated CO2 to the surface. However, in a CO2-rich environment, cement reacts with CO2, leading to the deterioration of its physical, chemical, transfer, morphological, and mechanical properties. This degradation can create flow paths that enable the leakage of sequestered CO2 to the surface, posing risks to humans, animals, and the environment. To address this issue, numerous studies have investigated the use of various additives in cement to reduce carbonation, thus enhancing the cement’s resistance to supercritical (sc) CO2 and maintaining its integrity. This paper provides a comprehensive review of current research on cement carbonation tests conducted by different authors. It includes detailed descriptions of the additives used, testing setups, curing conditions, methodologies employed, and experimental outcomes. This study will help to provide a better understanding of the carbonation process of the cement sample exposed to a CO2-rich environment, along with the pros and cons of the additives used in the cement. A significant challenge identified in this research is the lack of a standardized procedure for conducting carbonation tests, as each study reviewed employed a unique methodology, making direct comparisons difficult. Nonetheless, the paper provides an overview of the most commonly used temperatures, pressures, curing durations, and carbonation periods in the studies reviewed.

GENERALIZED DATASET OF GEOLOGICAL AND GEOPHYSICAL INFORMATION ON THE EASTERN SECTOR OF THE RUSSIAN ARCTIC FOR MACHINE LEARNING – BASED ANALYSIS

The article presents a practical approach to the geological and geophysical spatial data collection and preliminary processing to use in machine learning models for geophysical applications. According to the established principles for estimating efforts in data analysis, which are confirmed by the results of surveys among specialists, this stage is viewed as major time and resource-consuming, amounting up to 80% in total volume of data analysis for a hypothesis testing project. The paper focuses on creating a consistent data set that integrates geological and geophysical information on a given region. We consider problems of different sources in the geodata representation to be related to their format (vector/raster), scale, type of attribute information (quantitative/qualitative) and their availability. The algorithm formalization and synthesis for combining geospatial data and converting them into quantitative vectors is a critical aspect. Combining various data draws on the concept of neighborhood fitting in with the data selection techniques and data consolidation strategy. The paper presents the general architecture of the software and hardware complex which includes a module for data collection and transformation in Python using the Pandas library, a data storage system based on the PostgreSQL DBMS (Database Management System) with the PostGIS extension. It is shown that for the considered class of problems in geophysics, it is sufficient to use a relational DBMS for data storing and processing. If the problem dimension increases, it is proposed to use the Big Data technology based on Apache Hadoop for scaling the system. A practical application of the proposed approach is demonstrated as results of data collection for the Caucasus region and eastern sector of the Russian Arctic. Based on the prepared data, experiments were carried out using machine learning models for recognition of locations of potential strong earthquakes and for sensitivity estimation of several geophysical features of these regions. The article presents the experimental results and evaluation of their efficiency.

A pore-scale resolved direct numerical simulation study for scaling analysis of the solutal convection in porous media

Understanding the solutal convection is a crucial step towards accurate prediction of CO $_2$ sequestration in deep saline aquifers. In this study, pore-scale resolved direct numerical simulations (DNS) are performed to analyse the scaling laws of the solutal convection in porous media. The porous media studied are composed of uniformly distributed square or circular elements. The Rayleigh numbers in the range $426 \le Ra \le 80\,000$ , the Darcy numbers in the range $1.7\times 10^{-8} \le Da \le 8.8\times 10^{-6}$ and the Schmidt numbers in the range $250 \le Sc \le 10^4$ are considered in the DNS. The main time, length and velocity scales affecting the solutal convection are classified as the diffusive scales ( $t_I$ , $l_I$ and $u_I$ ), the convective scales ( $t_{II}$ , $l_{II}$ and $u_{II}$ ) and the shut-down scales ( $t_{III}$ , $l_{III}$ and $u_{III}$ ). These scales determine the pore-scale Rayleigh number $Ra_K$ and the Rayleigh number $Ra$ . Based on the DNS results, the scaling laws for the transient dissolution flux are proposed in the different regimes of convection. It is found that the onset time of convection ( $t_{oc}$ ) and the period of the flux-growth regime ( $\Delta t_{fg}$ ) vary linearly with the convective time scale $t_{II}$ . The merging of the original plumes and the re-initiation of the new plumes start in the same period, resulting in the merging re-initiation regime. Horizontal dispersion plays an important role in plume merging. The dissolution flux $F$ and the time since the onset of convection $t^{\ast }$ have an $F / u_{II} \sim (t^{\ast }/ t_{II})^{-0.2}$ scaling in the later stage of the merging re-initiation regime. This scaling is caused by the merging of the low-wavenumber plumes. It becomes more pronounced with decreasing porosity and leads to the nonlinear relationship between the Sherwood number $Sh$ and $Ra$ when the domain is not high enough for the plumes to fully develop. According to the DNS results, a regime is expected that is independent of both $Ra$ and $Ra_K$ , while the dimensionless constant flux $F_{cf}/u_{II}$ in this regime decreases with decreasing porosity. When the mean solute concentration reaches approximately 30 %, convection enters the shut-down regime. For large $Ra$ , the dimensionless flux in the shut-down regime follows the scaling law $F/u_{III}\sim (t/t_{III})^{-1.2}$ at large porosity ( $\phi =0.56$ ) and $F/u_{III}\sim (t/t_{III})^{-1.5}$ at small porosity ( $\phi =0.36$ or $0.32$ ). The study shows the significant pore-scale effect on the convection. The DNS cases in this study are mainly for simplified geometries and large $Ra_K$ . This can lead to uncertainties of the obtained scaling coefficients. It is important to determine the scaling coefficients for real geological formations to predict a real CO $_2$ sequestration process.

Error analysis and visualization of 3D geological models of mineral deposits

The accuracy of 3D geological models of mineral deposits has a significant impact on the precision and reliability of mining production decisions. High-precision 3D geological models can provide more accurate geological information of mineral deposits. A scientific error analysis method is proposed to quantify the errors in geological models and visualize these errors by assigning them to geological model entities. The errors in 3D geological models of mineral deposits mainly originate from modeling data and interpolation methods. By analyzing the generation and processing of modeling data, an error model for the modeling data is established. The Kriging interpolation method is used to quantitatively describe the errors in the modeling methods, and these errors are integrated into the 3D geological model. By using Boolean operations, the 3D geological model is combined with the open-pit mine entity model to generate an error-containing mining site model and mined rock model, and to calculate their mining and stripping volumes and errors, achieving error visualization. Using an open-pit coal mine in Inner Mongolia as a case study, the construction of its 3D mineral deposit and mining field models demonstrates the effectiveness and superiority of the proposed method in practical applications, highlighting its importance in improving the accuracy and reliability of mining production decisions.

Earthquake risks assessment and urban vulnerability: Case of Nador city, northeast Morocco

This study introduces an innovative approach to assessing seismic risks and urban vulnerabilities in Nador, a coastal city in northeastern Morocco at the convergence of the African and Eurasian tectonic plates. By integrating advanced spatial datasets, including Landsat 8–9 OLI imagery, Digital Elevation Models (DEM), and seismic intensity metrics, the research develops a robust urban vulnerability index model. This model incorporates urban land cover dynamics, topography, and seismic activity to identify high-risk zones. The application of Landsat 8–9 OLI data enables precise monitoring of urban expansion and environmental changes, while DEM analysis reveals critical topographical factors, such as slope instability, contributing to landslide susceptibility. Seismic intensity metrics further enhance the model by quantifying earthquake risk based on historical event frequency and magnitude. The calculation based on higher density in urban areas, allowing for a more accurate representation of seismic vulnerability in densely populated areas. The modeling of seismic intensity reveals that the most susceptible impact area is located in the southern part of Nador, where approximately 50% of the urban surface covering 1780.5 hectares is at significant risk of earthquake disaster due to vulnerable geological formations, such as unconsolidated sediments. While the findings provide valuable insights into urban vulnerabilities, some uncertainties remain, particularly due to the reliance on historical seismic data and the resolution of spatial datasets, which may limit the precision of risk estimations in less densely populated areas. Additionally, future urban expansion and environmental changes could alter vulnerability patterns, underscoring the need for continuous monitoring and model refinement. Nonetheless, this research offers actionable recommendations for local policymakers to enhance urban planning, enforce earthquake-resistant building codes, and establish early warning systems. The methodology also contributes to the global discourse on urban resilience in seismically active regions, offering a transferable framework for assessing vulnerability in other coastal cities with similar tectonic risks.

Physical and chemical properties of soils from different geological formations affecting Tuber melanosporum plantations: a case study in Acqualagna area (central Italy)

Soil properties play a pivotal role in the fructification of the Périgord black truffle (Tuber melanosporum Vittad.). However, the precise manner in which soil composition influences truffle production remains unclear. This study considered three plantation sites located in Acqualagna (central Italy), an important area for the cultivation of black truffles. The sites differed in terms of productivity and geological terrains. Site 1, which produced 4 kg yr−1, was on Schlier sediments (marls and clayey marls; Miocene age), site 2, which yielded 12 kg yr−1, was on alluvial deposits (heterogeneous, mainly sandy gravels and gravels; Holocene age), and site 3 produced 40 kg yr−1 was on Scaglia variegata (alternating marly limestones, calcareous marls, and marls; Eocene age). A total of 62 soil samples were collected and analyzed for their physical, chemical, organic, and mineralogical composition. Among the samples a control area without the presence of truffle was included. The soils composition differed for the content in phyllosilicates and calcite which ranged from 124 to 398 g kg−1 and 98 to 450 g kg−1, respectively. Principal component analysis extracted three factors, accounting for 82% of the total variance. Factor 1 (46.2% of the variance) was strongly and positively correlated with sheet silicates, smectite, clay and negatively with skeleton (fraction > 2 mm). The soils from Scaglia variegata and Schlier clustered around the active carbonate content which was 266 g kg−1 in Scaglia and 250 g kg−1 in Schlier. These soils clustered also for the clay fraction (389 g kg−1 and 428 g kg−1, respectively) as well as for the smectite (268 g kg−1 and 307 g kg−1, respectively). In spite, the soils from alluvial deposits clustered per skeleton (638 g kg−1). In terms of soil productivity, it can be posited that the contribution of the skeleton was always dominant. The carbonate contents allow for the differentiation between intermediate soils (alluvial deposits) and low-productivity soils (Schlier). Additionally, the clay component was found to be high in both low (428 g kg−1) and high productivity soils (389 g kg−1). Conversely, it was low in medium productivity soils (125 g kg−1). The automatic linear modelling (ALM) indicated that among all of the variables considered in this study, six of them were included in the equation and explained 94.3% of the variation in soil classified as suitable for black truffle production. In particular, calcite was identified as the most important predictor variable, followed by available P and K. Regarding the influence of functional groups of humic substances, amide I (1641 cm−1) exerted a positive effect while lignin residues (1510 cm−1) had a negative one. The findings of this study may assist in the selection of optimal soils for black truffle cultivation.

Experimental Study on Fluid Dissipation Effects in Core Samples by NMR Measurement

Laboratory core nuclear magnetic resonance (NMR) relaxation measurements offer geological information, including rock porosity and oil saturation, relevant to logging. When core samples drilled from wells are exposed to air, the fluids within their pores inevitably dissipate. This phenomenon may lead to discrepancies between the results of nuclear magnetic resonance relaxation experiments and the actual situation underground. To deeply explore the impact of fluid dissipation on NMR core analysis experimental results, a series of simulated dissipation experiments were designed under constant temperature and humidity conditions. Variations in one-dimensional and two-dimensional NMR measurement results of oil-saturated samples were examined under varying crude oil viscosities and dissipation times. The experimental results indicate that as exposure time increases, the T2 distribution of oil-saturated cores decreases, and the amplitude of the T2 distribution peaks decreases. Both oil and water relaxation components show a decreasing trend; however, the dissipation rate of the bounding water component significantly exceeds that of the crude oil component. By employing two-dimensional NMR relaxation time distribution fluid quantitative analysis technology, the relationship between the dissipation rates of various phase fluids and exposure time during the stable dissipation stage was analyzed. This offers a reference for adjusting the oil saturation of exposed cores based on NMR measurements.

A mechanistic model for the complex conductivity of clay materials. I. Theory

Summary Clay materials are ubiquitous in the Earth's continental and oceanic crusts. They are characterized by a large specific surface area, and, in contact with water, they have remarkable adsorption, catalytic and containment properties. Clay materials also exhibit a high electrical conductivity response associated with their large surface. However, sedimentary clay minerals have a complex microstructure and electrochemistry that are not fully understood and make the quantitative petrophysical interpretation of geoelectrical measurements difficult. In this study, we have developed a new mechanistic model to better understand and predict the complex conductivity of clay materials from their microstructure and electrical double layer properties. For the conductive component, our model considers ion electromigration in bulk water, clay electrical diffuse layer, and interlayer space, if any. Concerning polarisation, it takes into account ion back-diffusion in the Stern layer and in the interlayer space, if any, and also Maxwell-Wagner effect. Water and clay surface conductivities, formation factor, cementation exponent and sample electrically connected porosity can be extracted from the comparison of the model to experimental data. This study is a step forward to better understand and quantify the complex conductivity of clays observed during electrical and electromagnetic measurements, from laboratory to geological formation scales.

Synergy of CO2 Mineralization in Produced Water with Enhanced Oil Recovery: An Experimental Study

Addressing climate change necessitates innovative strategies to reduce atmospheric carbon dioxide (CO2) levels, significantly contributing to global warming. While traditional CO2 sequestration in geological formations is a viable mitigation method, it often presents high costs and logistical challenges. This study proposes a novel, cost-effective approach integrating CO2 mineralization with produced water treatment to enhance oil recovery (EOR). By mixing CO2 into produced water and subsequently adding sodium hydroxide (NaOH), we facilitate the precipitation of valuable minerals, specifically brucite (Mg(OH)2) as a surface process, which is then filtered out, improving water quality and making it efficient for EOR. Our findings demonstrate that the resulting treated water, referred to as “smart water,” increases oil recovery by 22.2% compared to conventional water flooding, highlighting the dual benefits of this mineralization process. Comprehensive analyses employing zeta potential measurements, X-ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDS), interfacial tension (IFT) measurements, and contact angle assessments elucidate significant alterations in wettability and interfacial properties due to brucite precipitation. This innovative method not only enhances oil recovery and produces valuable minerals but also plays a crucial role in reducing CO2 emissions by transforming produced water into a resource for carbon mineralization. By utilizing this approach, we mitigate the environmental impact of CO2 while demonstrating the potential to turn produced water into a sustainable solution for EOR. The novelty of our study lies in its integrated benefits, which combine mineralization, enhanced oil recovery, and CO2 emission reduction, offering a cost-effective and environmentally responsible strategy for the oil and gas industry.

Estimating soil strength using ultra high resolution seismic: A case study from a shallow water windfarm

The increasing global reliance on offshore wind farms as a sustainable energy source necessitates precise soil assessment for foundation design, due to their high foundation costs and complex integration into marine environments. This study explores the utilization of ultra-high-resolution seismic data in conjunction with cone penetration test data for soil strength estimation in offshore wind farm development. We propose a convolutional neural network-based approach that leverages ultra-high-resolution seismic data for direct soil strength estimation, aiming to address the challenges of limited cone penetration test measurements and potential overfitting in complex geological settings. Our methodology involves preprocessing ultra-high-resolution seismic and cone penetration test data, interpreting and integrating geological unit information, and applying repeated k-fold cross-validation to evaluate model performance. The field data results demonstrate the model's efficacy in accurately predicting cone penetration test curve trends, albeit with some amplitude discrepancies. We highlight the significance of geological interpretation in predicting soil strength and identify the dependency on valid data within each geological unit as a limitation.

Interdisciplinary Research for the Delimitation of Catchment Areas of Large Deep Karstic Aquifers: Origin of the Thermal Springs of Alhama de Aragon and Jaraba (Spain)

The integration of different sources of geological and hydrogeological information and the application of interdisciplinary methods have informed the origin of the thermal springs of Alhama de Aragón and Jaraba, as well as other associated semi thermal springs (1200 L/s of combined flow, 711 L/s at over 30 °C), which is the main objective of this article. These springs come mainly from the autogenous recharge that occurs in the Cretaceous calcareous outcrops that border the Almazán Basin to the north, both in the Ebro Basin (Jalón Valley) and in the Duero Basin. The aquifer, shaped by upper Cretaceous limestones under the Palaeogene and Neogene rocks of the Almazán Basin, has extensive depths of more than 4000 m in the NE sector. This hydrostratigraphic unit has been affected by a generalized pre-Paleogene karstification that provides the main porosity to the aquifer. The underground flow moves in a NW–SE direction, crossing the Duero–Ebro divide, favoured by the topographic difference in elevation between the two basins. The regional flow is coherent with the progressive increase in temperature, infiltrating recharge water age (about 20–25 years in the semi-thermal springs, and more than 60 years in the Alhama and Jaraba springs), mineralization, and flow of the springs through which the system discharges. This issue is key to being able to design any sustainable conservation strategy in terms of quantity and quality of resources within the recharge area of the most important thermal springs in Spain. The Jaraba and Alhama de Aragón hot springs share the same or similar temperature, chemical composition, and geological contact of the spring. Their tritium isotopic composition and its evolution over time are practically the same. Their isotopic composition in D and 18O is also very similar. Both springs share the same recharge zone of similar altitude and constitute the end of flow tubes of similar length and flow rate.