Dissolution Features Research Articles

Gas exposure trials of the Hall Formation, Lehen Field, Austria: Laboratory simulations of gas-caprock-brine interactions in an underground hydrogen storage system

In underground hydrogen storage (UHS) systems a reliable caprock is required to contain the stored hydrogen and prevent it from migrating out of the reservoir formation. Potential chemical reactions, which may occur upon the introduction of hydrogen into the subsurface, may change the sealing capacity of the caprock. To assess the risk of gas-caprock-brine interactions, gas exposure experiments using caprock and brine taken from an UHS site (Lehen Field, Austria) were undertaken at 50 °C and 150 bar pressure for treatment intervals of 3 months, 6 months and 12 months. Three different gas treatments were used: argon, as a non-reactive, experimental control, hydrogen and a gas mix of methane, hydrogen and carbon dioxide. Post-treatment scanning electron microscope imaging shows no significant dissolution features in the samples and the hydrochemistry before and after treatment do not indicate chemical changes attributable to reactions with hydrogen. The variations measured in porosity and mineralogy are interpreted to be due to geologic variation rather than resulting from chemical reactions in the experiments. These results confirm that large scale dissolution should not be expected in the caprock under the conditions of this UHS setting.

Features of loparite dissolution in aluminosilicate melts (experimental investigation)

Features of loparite dissolution in aluminosilicate melts (experimental investigation)

Stable isotopes (O, H) and quartz geochemistry provide insight to melt source and subsolidus fluid:rock interaction in the Cretaceous Little Nahanni LCT Pegmatites (NWT, Canada)

Previous studies of the mid-Cretaceous (ca. 85 Ma) LCT-type Little Nahanni Pegmatite Group (LNPG; Northwest Territories, Canada) document disequilibrium textures and pervasive metasomatism associated with rare-metal (e.g., Ta, Nb, Sn) mineralization. As in other pegmatite settings, the source of the melts and the nature and origin of pervasive metasomatism remain enigmatic. To resolve these latter issues, an integrated study of bulk O and H isotope analysis of mineral separates (quartz, K-feldspar, albite, muscovite, garnet), in situ Secondary Ion Mass Spectrometry (SIMS) isotopic (O) analysis of quartz and albite, and in situ Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) trace element analysis of quartz was done in concert with cathodoluminescence (CL) imaging and petrographic observations. Quartz with elevated δ18O values (δ18Oquartz = 10 to 16.3‰) also have high Ti-in-quartz temperatures (551 ± 17 °C to 603 ± 16 °C). These data along with their pristine nature from CL imaging suggest some localized melt-wall rock (WR) exchange occurred at the time of pegmatite melt emplacement. Furthermore, the elevated δ18O values indicate a crustal source (i.e., S-type granite) for the LNPG parental melt, which also overlaps with δ18Oquartz data for granitoids of the mid- to Late-Cretaceous Selwyn Plutonic Suite of this area. In contrast, the large range for δ18O values for metasomatic minerals, such as albite (−3.0 to +18.3‰) indicate a complex evolution involving multiple oxygen isotopic reservoirs, in particular incursion of meteoric water previously equilibrated with metasedimentary wall rocks. Finally, the large range for mineral pairs (e.g., Δquartz-albite = −5.1 to +14.3‰) and abundance of dissolution features in late-stage assemblages unequivocally indicates that sub-solidus fluid:rock interaction was responsible for such large spreads in δ18O and values δD values, although other processes (e.g., disequilibrium crystallization, thermal gradients, rapid cooling) might have also contributed, but to lesser extents.

Study of celecoxib dissolution process in the mixtures of ethanol and propylene glycol at different temperatures

ABSTRACT Categorised as a nonsteroidal anti-inflammatory drug targeting the COX-2 enzyme over COX-1, celecoxib (CXB) demonstrates high membrane permeability and low aqueous solubility, placing it in class II of the biopharmaceutical classification system. Therefore, comprehension of its solubility behaviour under different configurations is desirable. The current study explores CXB solubility in propylene glycol and ethanol binary mixtures by varying temperature and cosolvent concentration, using the shake-flask method followed by spectroscopy analysis. The results show increased solubility of CXB in this mixture as ethanol mass fraction and temperature increase. Several cosolvency models were used to correlate data, including van't Hoff, Jouyban-Acree, Jouyban-Acree-van't Hoff, and mixture response surface/modified Wilson models. The mathematical models’ accuracy was investigated through mean relative deviation. The Gibbs and van't Hoff equations were employed to establish the thermodynamic features of CXB dissolution.

Определение скорости электрохимического растворения стали У10А в условиях ЭХРО с неподвижным катодом-инструментом

Introduction. In blank production, when replacing hard alloys with tool steels, difficulties arise in shaping surfaces to ensure the required parameters of productivity, quality and accuracy, due to the presence of incomplete information for assigning electrochemical processing modes for this class of materials. This fact requires additional research to determine rational processing modes that provide the necessary technological parameters (productivity, dimensional accuracy and surface roughness). The purpose of the work is to conduct research to establish the patterns of electrochemical shaping of tool steels and determine the modes of the shaping process. The work investigated the features of anodic dissolution of U10A tool steel in an aqueous NaCl solution of 10 % concentration. The range of potential changes was from 0 to 8 V. Technological performance parameters were determined (current output for the main reaction and the rate of electrochemical dissolution at a voltage of 8 V and an electrolyte pressure of 0.1 MPa). Research methods. For polarization studies, a potentiodynamic research method was chosen. Technological experiments were carried out using the model of piercing holes with a stationary cathode-tool made of stainless steel without insulation. A circular cross-section with outer diameters of 0.908 mm and inner diameters of 0.603 mm was chosen as a cathode tool. Results and discussions: it is revealed that the electrochemical dissolution of U10A tool steel in a 10 % aqueous solution of NaCl is active in the studied potential range from 0 to 8 V. The technological experiments carried out made it possible to establish the dimensions of the resulting holes — an average diameter of 1.433 mm and a depth of 0.574 mm. The current efficiency was 70.83 %. Based on the analysis of the experimental data obtained, it is established that in order to ensure high productivity of the process of electrochemical forming of U10A steel in a solution of 10 % NaCl, the feed of the cathode tool should be 0.2232 mm/min, which corresponds to the rate of electrochemical dissolution under the studied forming conditions.

Diagenetic evolution of Upper Cretaceous carbonate sequences (Sarvak Formation) in the Abadan Plain, Iran: evidence from petrographic, elemental, stable, and strontium isotopic data

ABSTRACT This study investigates the diagenetic evolution and geochemical variations within the Sarvak Formation by integrating the core, thin-section, scanning electron microscopy, X-ray diffraction, trace elements, carbon-oxygen, and strontium isotopic data from three wells in the Abadan Plain. The formation displays diverse diagenetic processes, influenced by multiple exposure surface condition including the Cenomanian-Turonian boundary (CT-ES) and middle Turonian (mT-ES). Meteoric diagenesis, shaped by tectonic activities and eustatic sea level changes, played a pivotal role, leading to dissolution (karstification), brecciation, cementation, and palaeosol formation. Geochemical analysis revealed significant elemental variations across the studied wells. Magnesium (Mg) exhibited peaks at sequence boundaries, responding to facies changes, while iron (Fe) and manganese (Mn) concentrations increased below disconformities, reflecting changes in redox conditions and karstification. Sodium (Na) concentrations varied with facies changes, showing peaks at sequence boundaries, indicative of palaeoexposure events. Strontium (Sr) isotopes aided in delineating stratigraphic positions of palaeoexposure surfaces and absolute dating of sequences. Increases in87Sr/86Sr ratios below disconformities suggested subaerial exposure events, with shorter durations at CT-ES and longer durations at mT-ES, contributing to dissolution features development. The δ13Ccarb and δ18Ocarb values indicated severe meteoric diagenesis below sequence boundaries, characterized by dissolution and reprecipitation of calcium carbonate as low-magnesium calcite (LMC) cements. Cross plots of δ13Ccarb vs. δ18Ocarb displayed inverted-J patterns, indicative of meteoric diagenesis effects. Comparison with previous studies highlighted similar trends in geochemical variations, with notable differences in element concentrations between wells. This study enhances our understanding of diagenetic history of the Sarvak Formation in the Abadan Plain and, in a larger scale, provides insights into diagenetic evolution of palaeoexposure-related carbonate sequences.

Investigating the Acid Erosion Characteristics of Carbonate Rocks under Hydrodynamic Action.

In carbonate areas, the unique dissolution features bring a lot of resistance to engineering constructions. The acidic filtrate will definitely cause accelerated dissolution of the surrounding rocks, and the mechanism of accelerated dissolution of such rocks in acid is not clear. In order to explore the dissolution pattern of carbonate rocks after the alteration of their primary environments, a self-made rotating reaction device was used to conduct laboratory dissolution experiments on carbonate cores under three conditions. The mass loss, the change of pH, the molar concentration of Ca2+ and Mg2+, and the morphological changes before and after acid erosion were obtained. The results of correlation analysis show that the dissolution characteristics of carbonate are significantly related to dissolution time, composition of rocks, liquid flow rate, and acid concentration. Segmented characteristics were recorded between CaO/MgO and the reaction sequence (m). When 2 < CaO/MgO < 30, the increase of CaO/MgO has a significant contribution to the chemical dissolution rate; however, when 30 < CaO/MgO < 66, the increase of CaO/MgO does not contribute significantly to the chemical dissolution rate. The dissolution rate is positively correlated with the liquid flow rate. Also, liquid flow rate changes affect dolomite more than they do limestone. The mass loss rate (Rc) order of the rocks of the five carbonate formations was Maocaopu > Qingyan > Falang > Anshun > Dengying. Differences in dissolution induced by the acidic fluids in different formations will eventually form complex dissolution channels.

Groundwater‐surface water interaction, dissolved organic carbon oxidation and dissolution in carbonate aquifers

AbstractThe high primary porosity and permeability of eogenetic karst aquifers permit water recharged through secondary dissolution features to be temporarily stored in aquifer matrix porosity. The recharged water contains elevated dissolved organic carbon (DOC) concentrations that, when oxidized, enhance limestone dissolution and impact carbon cycling. We evaluate the relationship between DOC oxidation and limestone dissolution using observations at a stream sink‐rise system and reversing spring in the Floridan aquifer, north‐central Florida, USA, where subsurface residence times of recharged water are days and months, respectively. We estimate water chemical compositions during surface water‐groundwater interactions at these two systems with mixing models of surface water and groundwater compositions and compare them with measured DOC, dissolved inorganic carbon (DIC), Ca2+ and dissolved organic nitrogen (DON) concentrations. Differences between measured and modelled concentrations represent net changes that can be attributed to calcite dissolution and redox reactions, including DOC oxidation. DOC losses and Ca2+ gains exhibit significant (p &lt; 0.01) inverse linear correlations at both the reversing spring (slope = −0.9, r2 = 0.99) and the sink‐rise system (slope = −0.4, r2 = 0.72). DOC oxidation in both systems was associated with decreases in the molar C:N ratio (DOC:DON). Significant (p &lt; 0.01) positive linear correlations between increases in Ca2+ and DIC concentrations after correcting for DIC derived from calcite dissolution occurred at both the reversing spring (slope = 1.3, r2 = 0.99) and the sink‐rise system (slope = 1.61, r2 = 0.75). Greater deviations from the expected slope of −1 or +1 at the sink‐rise system than at the reversing spring indicate DOC oxidation contributes less dissolution at the sink‐rise system than at the reversing spring, likely from shorter storage in the subsurface. A portion of the deviation from expected slope values can be explained by the dissolution of Mg‐rich carbonate or dolomite rather than pure calcite dissolution. Despite this, slope values reflect kinetic effects controlling incomplete consumption of carbonic acid during dissolution reactions.

Features of Loparite Dissolution in Aluminosilicate Melts (Experimental Investigation)

Features of Loparite Dissolution in Aluminosilicate Melts (Experimental Investigation)

Seismic expression of shallow-water carbonate structures through geologic time

Shallow-water carbonate structures are characterized by different shapes, sizes, and identifying features, which depend, among other factors, on the age of deposition and on the carbonate factory associated with a specific geologic period. These variations have a significant impact on the imaging of these structures in reflection seismic data. This study aims at providing an overall, albeit incomplete, picture of how the seismic expression of shallow-water carbonate structures has evolved through deep time. Here, 297 shallow-water carbonate systems of different ages, spanning from Precambrian to present, with a worldwide distribution of 159 sedimentary basins, have been studied. For each epoch, representative seismic examples of shallow-water carbonate structures are described through the assessment of a selection of discriminating seismic criteria or parameters. The thinnest structures, commonly represented by ramp systems, usually occurred after mass extinction events and are mainly recognizable in seismic data through prograding clinoform reflectors. The main diagnostic seismic features of most of the thickest structures, which are found to be Precambrian, Late Devonian, Middle-Late Triassic, Middle-Late Jurassic, some Early Cretaceous presalt systems, “middle” and Late Cretaceous, Middle-Late Miocene, and Plio-Pleistocene, are steep slopes and reefal facies. Slope-basinal resedimented seismic facies are mostly observed in thick steep-slope platforms, and they are more common, except for megabreccias, in post-Triassic structures. Seismic-scale early karst-related dissolution features are mostly observed in icehouse platform deposits. Pinnacle structures and the thickest margin rims are concentrated in a few epochs, such as Middle-Late Silurian, Middle-Late Devonian, earliest Permian, Late Triassic, Late Jurassic, Late Paleocene, Middle-Upper Miocene, and Plio-Pleistocene, which are all characterized by high-efficiency reef builders.

Fracture analysis in borehole images from BM-C-33 area, outer Campos Basin, Brazil

In the BM-C-33 area, divided into the Raia Manta and Raia Pintada development areas, reservoirs are arranged into three structural highs: Gávea, Seat, and Pão de Açúcar. These reservoirs consist of pre-salt limestones deposited on volcanic sequences and underwent complex diagenetic evolution. Successive post-depositional processes, including silicification, affected original mineral assemblage, modified pore textures, and caused intense fracturing. Based on borehole image logs (BHI), wireline data from four wells, and 2D and 3D seismic data, this study details natural fracture acoustic and resistivity properties. It also discusses the relationship of faults, fractures, and vugs with diagenetic and tectonic processes. The authors used the data to divide the pre-salt section (Cabiúnas and Macabu formations) into three informal stratigraphic units. The analysis of interpreted fractures within these units suggests that major fracturing occurred due to regional tectonic stress, with local aspects like structural positioning interfering. The results of the fracture analysis imply a direct relationship between fracturing and silicification. Additionally, fracture density, vug volume distribution, and the presence of dissolution features like enlarged fractures limited to specific units imply stratigraphic control on fluid percolation. Finally, the study examines structural particularities in BM-C-33 area that potentially impacted intensity and extension of diagenetic alterations.

Natural responses of Neoproterozoic dynamic karst springs to rainfall events, São Miguel Watershed, Minas Gerais, Brazil

AbstractKarst aquifers consist of complex networks of conduits in which groundwater flows and recharge/discharge processes are generally more dynamic than in other types of aquifers. Due to their intrinsic heterogeneity and anisotropy, monitoring, quantifying, and analysing natural responses of karst springs is an efficient tool. Unlike Cenozoic and Mesozoic rocks, in Neoproterozoic karst systems, groundwater circulates and stores generally in dissolution features known as tertiary porosity, as the rock's primary porosity is recrystallized, considered negligible. This article studies the hydrodynamics of a karst portion of the São Miguel River basin, southwest of the state of Minas Gerais, Brazil. The region is predominantly composed of Neoproterozoic carbonate rocks, dating from about 570 to 540 million years ago. During a hydrological year (2019–2020), three karst springs (S1, S2, and S3) were daily monitored through their natural responses (variations of electrical conductivity, EC, temperature, T, and discharge, Q) to rainfall episodes. The data were interpreted based on the analysis of spring hydrographs, time series, recession curves (seasonal and intra‐annual), and statistics of EC, T, and Q variations. The results show the three springs generally exhibit quick flow, typically karstic, in the case of hydrosystems with a well‐structured and functional underground drainage network. The time series indicate the hydrosystem drained by S1 presents slower circulation and a lower degree of linearity, resulting from the higher sinuosity of the system, while the hydrosystems of S2 and S3 have similar behaviours, of quick water circulations immediately after a rainy episode. The degrees of karstification classify S1 and S2 as complex and extensive karst systems consisting of several subsystems, and S3 as a system in which the conduit network is more developed at the upper epiphreatic zone than near the outlet.

Mechanisms controlling albite dissolution/precipitation kinetics as a function of chemical affinity: New insights from experiments in 29Si spiked solutions at 150 and 180 °C

Knowledge of the rates of dissolution of rock-forming minerals close to equilibrium and their dependence on ΔGr, the Gibbs free energy of reaction, is essential for describing the temporal and spatial evolution of many environmental and engineering processes involving solid/fluid interactions. In the present study we used the isotope-doping method to quantify albite forward and net dissolution rates. Batch experiments were performed at 150, 180 °C and pH = 9 at near equilibrium and equilibrium conditions (-25 ≤ ΔGr ≤ + 8.2 kJ/mol) in 29Si spiked solutions which were undersaturated with the secondary Al-Si solid phases likely to precipitate.The forward dissolution rates normalized to the initial BET surface area were found to decrease continuously and monotonically with increasing time and ΔGr, achieving values 1.3 to 2.4 orders of magnitude lower at chemical equilibrium than initial far from equilibrium values, with the highest rate decrease for the highest solid to fluid ratio. These rate drops were accompanied by an increase in BET specific surface areas associated with the formation of widespread dissolution features. A decrease of albite forward dissolution rate together with an increase of its BET surface area was also observed as a function of reaction time at far from equilibrium conditions (ΔGr ≤ − 65 kJ/mol). These observations are consistent with a continuous decrease with time and increasing ΔGr of albite effective surface area linked to the formation of unreactive negative crystal facets, in addition to etch pits stopping nucleating above a critical value of ΔGr. Thus, the observed decrease in albite dissolution rate as equilibrium is approached is not linked primarily to the increase in the contribution of the backward reaction but rather to the decrease of the forward reaction rate in conjunction with the decrease in the density of reactive sites at the mineral surface.The results of this study show that the characterization of the effective surface area and its evolution with reaction time and chemical affinity is crucial to deriving robust dissolution rates of well-crystallized minerals like feldspars. Dissolution experiments in 29Si spiked solutions of samples with different history and well-characterized effective surface area and surface morphology should help to better quantify the rate laws controlling silicate minerals weathering.

Mass transfer fundamentals in pervaporation, perstraction and sorption: A unified approach

The high affinity between an organic solute and a polymeric sorbent or membrane is the basis for separating organic contaminants from water via sorption, pervaporation and perstraction. These processes all share the same features of dissolution and diffusion, and thus their mass transfer characteristics can be correlated. However, they are often dealt with independently, and the research findings from one process are rarely applied to the other. The permeability coefficient in perstraction (for liquid permeation) based on concentration gradient as the driving force for mass transfer and the permeability coefficient for pervaporative transport expressed customarily in analog to vapor permeation can hardly be compared directly, and sometimes seemingly contradictive trends in temperature dependencies of the permeability coefficients for the two process modes may result. Looking into the mass transfer fundamentals pertaining to sorption, pervaporation and perstraction, this work attempted to provide a unified approach to the mass transfer in all these processes. While the permeability coefficient in pervaporation uses equivalent vapor pressure gradient across the membrane as the driving force, this work provided a generalized treatment by taking into account the sorption constants embedded in the permeability coefficients of the different processes so that the performance parameter for one process could be applied to another, which would be especially useful for screening and developing appropriate membrane/sorbent materials. In addition, the relationships among the selectivities of these separation processes were elucidated, which allowed for an intuitive illustration of how the process selectivity changed due to the process mode. Aniline removal from water via pervaporation, perstraction and sorption using a poly(ether-b-amide) membrane/sorbent was used as an example to illustrate and validate the approach.

The role of plants in ironstone evolution: iron and aluminium cycling in the rhizosphere

The Carajás plateaus in Brazil host endemic epilithic vegetation (“campo rupestre”) on top of ironstone duricrusts, known as canga. This capping rock is primarily composed of iron(III) oxide minerals and forms a physically resistant horizon. Field observations reveal an intimate interaction between canga's surface and two native sedges (Rhynchospora barbata and Bulbostylis cangae). These observations suggest that certain plants contribute to the biogeochemical cycling of iron. Iron dissolution features at the root-rock interface were characterised using synchrotron-based techniques, Raman spectroscopy and scanning electron microscopy. These microscale characterisations indicate that iron is preferentially leached in the rhizosphere, enriching the comparatively insoluble aluminium around root channels. Oxalic acid and other exudates were detected in active root channels, signifying ligand-controlled iron oxide dissolution, likely driven by the plants' requirements for goethite-associated nutrients such as phosphorus. The excess iron not uptaken by the plant can reprecipitate in and around roots, line root channels and cement detrital fragments in the soil crust at the base of the plants. The reprecipitation of iron is significant as it provides a continuously forming cement, which makes canga horizons a ‘self-healing’ cover and contributes to them being the world's most stable continuously exposed land surfaces. Aluminium hydroxide precipitates (“gibbsite cutans”) were also detected, coating some of the root cavities, often in alternating layers with goethite. This alternating pattern may correspond with oscillating oxygen concentrations in the rhizosphere. Microbial lineages known to contain iron-reducing bacteria were identified in the sedge rhizospheric microbiome and likely contribute to the reductive dissolution of iron(III) oxides within canga. Drying or percolation of oxygenated water to these anaerobic niches have led to iron mineralisation of biofilms, detected in many root channels. This study sheds light on plants' direct and indirect involvement in canga evolution, with possible implications for revegetation and surface restoration of iron mine sites.

Multi-population dissolution in confined active fluids.

Autonomous out-of-equilibrium agents or cells in suspension are ubiquitous in biology and engineering. Turning chemical energy into mechanical stress, they generate activity in their environment, which may trigger spontaneous large-scale dynamics. Often, these systems are composed of multiple populations that may reflect the coexistence of multiple species, differing phenotypes, or chemically varying agents in engineered settings. Here, we present a new method for modeling such multi-population active fluids subject to confinement. We use a continuum multi-scale mean-field approach to represent each phase by its first three orientational moments and couple their evolution with those of the suspending fluid. The resulting coupled system is solved using a parallel adaptive level-set-based solver for high computational efficiency and maximal flexibility in the confinement geometry. Motivated by recent experimental work, we employ our method to study the spatiotemporal dynamics of confined bacterial suspensions and swarms dominated by fluid hydrodynamic effects. Our in silico explorations reproduce observed emergent collective patterns, including features of active dissolution in two-population active-passive swarms, with results clearly suggesting that hydrodynamic effects dominate dissolution dynamics. Our work lays the foundation for a systematic characterization and study of collective phenomena in natural or synthetic multi-population systems such as bacteria colonies, bird flocks, fish schools, colloid swimmers, or programmable active matter.

Control of brine composition over reactive transport processes in calcium carbonate rock dissolution: Time-lapse imaging of evolving dissolution patterns

This study investigates the impact of brine composition—specifically calcium ions and NaCl-based salinity—on the development of dissolution features in Ketton, a porous calcium carbonate rock. Utilizing a laboratory XMT (X-ray microtomography) scanner, we captured time-lapse in situ images of Ketton samples throughout various dissolution experiments, conducting four distinct flow-through experiments with differing brine solutions at a flow rate of 0.26 ml min⁻1. The scans yielded a voxel size of 6 μm, enabling the assessment of the temporal evolution of porosity and pore structure through image analysis and permeability evaluations via single-phase fluid flow simulations employing direct numerical solutions and network modeling, as opposed to direct measurement.Time-lapse imaging technique has delineated the extent to which the concentrations of CaCl₂ and NaCl in the injecting solution control the structural evolution of dissolution patterns, subsequently triggering the development of characteristic dissolution pattern. The inflow solution with no Ca2+ ions and with the minimal salt content manifested maximum dissolution near the sample inlet, coupled with the formation of numerous dissolution channels, i.e., wormholes. Conversely, solutions with a trace amount of Ca2⁺ ions induced focused dissolution, resulting in the formation of sparsely located channels. Inflow solutions with high concentrations of both Ca2⁺ ions and salt facilitated uniformly dispersed dissolution, primarily within microporous domains, initiating particle detachment and displacement and leading to localized pore-clogging. The relative increase in permeability, in each experiment, was correlated with the developed dissolution pattern. It was discerned that varying ratios of salt and calcium concentrations in the injected solution systematically influenced image-based permeability simulations and porosity, allowing for the depiction of an empirical porosity-permeability relationship.

New insights into hypogenic non-matrix dissolution mega features driving subsurface fluid movement within the Arab Formation, Saudi Arabia

This paper reports the results of a large integrated study into the classification, distribution and significance of hypogenic non-matrix large-scale dissolution features present in the Arab Formation of Saudi Arabia. The investigation of these features was based primarily on extensive core, wireline caliper, wireline/log while drilling resistivity borehole image logs supported by encountered total lost circulation of drilling fluids and production log data. Dissolution features observed by this study were classified into three main categories: touching vugs, ramiform voids, and cavities. This study is the first to successfully quantify the presence and extent of these non-matrix intervals in this formation, which has greatly improved the 3D modelling efforts. Over 8100 feet of large-scale dissolution features were intersected in both vertical and horizontal wells. The hypogenic genesis of the large-scale dissolution features pre-dates replacement dolomitization in the area. Given the extensive data reviewed, the presented results give insight into the importance of the large-scale dissolution mega features as they are strongly related to total loss of mud circulation during drilling, and will have implications for well-to-well short-cutting during production and impact oil storage capacity.

Fluorinated Benzimidazole-Linked Highly Conjugated Polymer Enabling Covalent Polysulfide Anchoring for Stable Sulfur Batteries.

Sulfur is one of the most abundant and economical elements in the p-block family and highly redox active, potentially utilizable as a charge-storing electrode with high theoretical capacities. However, its inherent good solubility in many electrolytes inhibits its accessibility as an electrode material in typical metal-sulfur batteries. In this work, the synthetically designed fluorinated porous polymer, when treated with elemental sulfur through a well-known nucleophilic aromatic substitution mechanism (SN Ar), allows for the covalent integration of polysulfides into a highly conjugated benzimidazole polymer by replacing the fluorine atoms. Chemically robust benzimidazole linkages allow such harsh post-synthetic treatment and facilitate the electronic activation of the anchored polysulfides for redox reactions under applied potential. The electrode amalgamated with sulfurized polymer mitigates the so-called polysulfide shuttle effect in the lithium-sulfur (Li-S) battery and also enables a reversible, more environmentally friendly, and more economical aluminum-sulfur (Al-S) battery that is configured with mostly p-block elements as cathode, anode, and electrolytes. The improved cycling stabilities and reduction of the overpotential in both cases pave the way for future sustainable energy storage solutions.

Dissolution feature differences of carbonate rock within hydro-fluctuation belt located in the Three Gorges Reservoir Area

The stability of geological environment in the Three Gorges Reservoir Area (TGRA) has experienced severe challenges due to the 30 m hydro-fluctuation belt (HFB). The vertical dissolution features vary with the mechanism of water and rock interaction. Although dissolution features have been adequately explained by physical and mechanical parameters, the characterization of chemical changes in dissolution is vital but frequently neglected information. For this purpose, the hyperspectral characteristics and mineralogical composition variation of rock HFB in different areas of the Triassic Daye Formation are tested to elucidate the dissolution behaviors. Then, the deterioration degree of dissolution is quantified by a multi-objective data integration based on Random Forest Regression (RFR) model. The spatial distribution of dissolution and the seasonal deterioration characteristics are identified depending on the spectral response of carbonate. Specifically, the dissolution degree is proportional to elevation, and inverse to the bedding angle at 0–40° in the investigated stratum. Combined with the hydrological characteristics of study area, the corresponding regional phenomena can be distinguished as reservoir water dominated, rainfall dominated, and coupled action. Affected by reservoir water and acid rainfall, the HFB may deteriorate most severely from January to April. In addition, the contribution of RFR model integrated spectral and geometric data to the deterioration evaluation of the HFB is discussed, which can effectively enhance the identification of rock mass boundary in a single spectral data model. Thus, these results are conducive to the rapid evaluation of regional geomorphological characteristics and the monitoring of geological disasters in the TGRA.