Lateral Migration Research Articles

Hydrocarbon micro‐migration and differential enrichment mechanism of shale oil in upper Cretaceous Qingshankou Formation in Songliao Basin

Shale reservoir has strong heterogeneity in mineral composition and oil content even at a short distance in the same interval. To better understand the accumulation mechanism of shale oil and hydrocarbon migration tendency in the interval, and explore the main influencing factors of distribution. This paper employed various methods, including thin‐section observation, TOC (total organic matter (OM)) analysis, rock pyrolysis, Soxhlet extraction, group component separation, and GC–MS (gas chromatography mass spectrometry) analysis of saturated hydrocarbons. The shale oil samples were collected from an exploratory well in the Songliao Basin, and the distribution and enrichment characteristics of shale oil interlayers were analysed. The results show that the first member of Qingshankou Formation (K2qn1) could be divided into six small layers. From Q1 to Q6, the lithofacies could be divided into three types: high‐frequency laminar shale, massive shale, and bioclastic shale. The lacustrine matrix shale of K2qn1 in Songliao Basin has medium TOC, and high oil contents, OM conversion rate. The TOC ranges from 1.5 to 4.2 wt%, S1 varies between 1.4 and 4 mg/g, S2 falls within the range of 4 to 10.6 mg/g, Tmax ranges from 351 to 497°C, and the OSI varies between 57 and 115.34 mg HC/g rock. The lower part of the K2qn1, Q1–Q4, characterized by high‐frequency laminar shale, contained residual shale oil, while the upper part of the K2qn1, Q5 and Q6, characterized by bioclastic shale and massive mudstone, and are dominated by in‐situ type shale oil. The crude oil in K2qn1 is homologous, and primarily undergoes micro‐migration. The Q5–Q6 section has the highest light oil content, while other regions with notable light components are located in the middle of Q1, the upper sections of Q2, Q3, and Q4.Q1–Q4 are primarily composed of residual shale oil, whereas Q5–Q6 is primarily composed of in‐situ shale oil, and the primary micro‐migration direction of shale oil occurs laterally within Q1–Q4. The lateral migration of each section mainly occurs at the upper part of Q3 and Q4, the lower part of Q1 and Q2, the bottom of Q5, and the interface between Q6 and the second member of Qingshankou formation (K2qn2). The block mudstone retains in‐situ shale oil, especially light hydrocarbons. Within the high‐frequency laminar shale, there is strong horizontal connectivity, and lateral hydrocarbon expulsion serves as the primary mechanism for micro‐migration in Q1–Q4. This paper can provide reference values for K2qn1 Formation shale oil and the migration and differential reservoir formation of medium and high‐maturity matrix shale oil.

The pace of global river meandering influenced by fluvial sediment supply

Meandering rivers move gradually across the floodplains, and this river movement presents socioeconomic risks along river corridors and regulates terrestrial biogeochemical cycles. Experimental and field studies suggest that fluvial sediment supply can exert a primary control on lateral migration rates of rivers. However, we lack an understanding of the relative importance of environmental boundary conditions, such as floodplain vegetation and sediment supply, in setting the pace of river meandering across different environmental settings. Here, we combine the analysis of satellite imagery and global-in-scale sediment and water discharge models to evaluate the controls on lateral migration rates of 139 meandering rivers that span a wide range in size, climate, and bank vegetation. We show that migration rates normalized by the channel width monotonically increase with the volumetric sediment flux normalized by the characteristic size of the river. This relation is consistent across rivers in vegetated and unvegetated catchments, indicating that enhanced lateral migration rates in unvegetated basins is likely not only facilitated by lower bank mechanical strength, but also by higher normalized sediment supply in ephemeral rivers. Using three case examples, we also demonstrate that width-normalized meander migration rates respond to spatial gradients in sediment supply caused by river impoundments, highlighting the prominent role of sediment supply in setting the pace of meander migration. Our results suggest that sediment-supply variations caused by climate, land-cover and land-use changes can lead to predictable changes in meandering river evolution and ultimately drive architectural changes in sedimentary stratigraphy.

The dominant three-element model of oil and gas accumulation in basement buried hills: A discussion on new exploration frontiers in the deepwater area of the northern South China Sea

Basement buried hill reservoirs represent significant emerging prospects among the newly discovered growth poles in the deepwater areas of the northern South China Sea. Addressing the unclear key factors contributing to their formation, this study dissects successful global exploration cases of basement buried hill reservoirs and analyzes the common characteristics of basement reservoir accumulation under different basin types, structural backgrounds, basement lithologies, and oil and gas geological conditions. A three-element coupling relationship, termed “source-reservoir-cap”, is proposed as the dominant mechanism controlling basement buried hill reservoir formation. The genesis of these reservoirs requires adequate oil and gas supply, appropriately sized accumulation bodies, and effective sealing layers. The optimal configuration of the “source-reservoir-cap” relationship directly influences the efficient charging and preservation of oil and gas within basement buried hill reservoirs. Four configurations are identified, including circumstances such as the source-underlying low-positioned basement buried hill with a “source-reservoir cover docking migration type”, the source-border middle-positioned basement buried hill with a “source-reservoir lateral window docking migration type”, and the source-outside high-positioned basement buried hill with both “source-reservoir short-distance transport and migration type” and “source-reservoir long-distance transport and migration type”. The first to three models present favorable accumulation conditions. Based on the “source-reservoir-cap” three-element coupled model, this study identifies the Yunkai basement buried hill in the Pearl River Mouth Basin, the central depression in the Qiongdongnan Basin, and the northern and southern basement buried hills belts as crucial exploration targets in the deepwater areas of the northern South China Sea.

Evolution of sub-ice-shelf channels reveals changes in ocean-driven melt in West Antarctica

Abstract Basal channels, which are troughs carved into the undersides of ice shelves by buoyant plumes of water, are modulators of ice-shelf basal melt and structural stability. In this study, we track the evolution of 12 large basal channels beneath ice shelves of the Amundsen and Bellingshausen seas region in West Antarctica using the Landsat record since its start in the 1970s through 2020. We observe examples of channel growth, interactions with ice-shelf features, and systematic changes in sinuosity that give insight into the life cycles of basal channels. We use the last two decades of the record, combined with contemporary ice-flow velocity datasets, to separate channel-path evolution into components related to advection by ice flow and those controlled by other forcings, such as ocean melt or surface accumulation. Our results show that ice-flow-independent lateral channel migration is overwhelmingly to the left when viewed down-flow, suggesting that it is dominated by Coriolis-influenced ocean melt. By applying a model of channel-path evolution dominantly controlled by ice flow and ocean melt, we show that the majority of channels surveyed exhibit non-steady behavior that serves as a novel proxy for increased ocean forcing in West Antarctica starting at least in the early 1970s.

Structural control of igneous intrusions on fluid migration in sedimentary basins: the case study of large bitumen seeps at Cerro Alquitrán and Cerro La Paloma, northern Neuquén Basin, Argentina

Abstract Cooling subvolcanic igneous intrusions are known to have a tremendous impact on fluid flow in the shallow Earth's crust. However, the long-term post-cooling legacy of subvolcanic intrusions on fluid flow has received much less attention. Here we describe geological examples in the Andean foothills, Argentina, showing that igneous intrusions have long-term effects on fluid flow after their emplacement and cooling. The case study consists of ∼11 Myr-old eroded andesitic intrusions of Cerro Alquitrán and Cerro La Paloma, northern Neuquén Basin, Argentina, at the rims of which large volumes of bitumen are naturally seeping out at the Earth's surface. The intrusions exhibit laccolithic shapes with steep-sided contacts with the host rock. Near the intrusive contacts, the andesite is intensely broken along concentric breccia bands and fracture bands, interpreted as resulting from syn-emplacement brittle magma deformation, which represent high-permeability pathways for the migrating bitumen. Organic geochemical analyses of the bitumen show that the seeping oils were generated from incipiently mature Vaca Muerta sections located in a regional kitchen to the west, implying a lateral migration of ∼10–20 km. The Cerro Alquitrán and Cerro La Paloma intrusions are demonstrative examples highlighting how extinct subvolcanic intrusions have long-term consequences for subsurface fluid circulations in sedimentary basins.

A hydrodynamic-based dual-function microfluidic chip for high throughput discriminating tumor cells

A hydrodynamic-based microfluidic chip consisted of two function units that could not only separate tumor cells (TCs) from whole blood but also remove residual blood cells was designed. The separation of TCs was achieved by a straight contraction-expansion array (CEA) microchannel on the front end of the chip. The addition of contractive structure brought a micro-vortex like Dean vortex that promoted cell focusing in the channel, while when cells entered the dilated region, the wall-induced lift force generated by the channel wall gave cells a push away from the wall. As the wall-induced lift force is proportional to the third power of the cell diameter, TCs with larger diameter will have a larger lateral migration under the wall-induced lift force, realizing the separation of TCs from blood sample. Fluorescent particles with diameters of 19.3 μm and 4.5 μm were used to simulate TCs and red blood cells, respectively, to verify the separation capacity of the proposed CEA microchannel for particles with different diameter. And a separation efficiency 98.7% for 19.3 μm particles and a removal rate 96.2% for 4.5 μm particles was observed at sample flow rate of 10 μL min−1 and sheath flow rate of 190 μL min−1. In addition, a separation efficiency about 96.1% for MCF-7 cells (stained with DiI) and removal rates of 96.2% for red blood cells (RBCs) and 98.7% for white blood cells (WBCs) were also obtained under the same condition. However, on account of the large number of blood cells in the blood, there will be a large number of blood cells remained in the isolated TCs, so a purification unit based on hydrodynamic filtration (HDF) was added after the separation microchannel. The purification channel is a size-dictated cell filter that can remove residual blood cells but retain TCs, thus achieving the purification of TCs. Combined the CEA microchannel and the purifier, the microchip facilitates sorting of MCF-7 cells from whole blood with a separation rate about 95.3% and a removal rate over 99.99% for blood cells at a sample flow rate of 10 μL min−1, sheath flow rate of 190 μL min−1 and washing flow rate of 63 μL min−1.

Platform margin belt structure and sedimentation characteristics of Changxing Formation reefs on both sides of the Kaijiang-Liangping trough, eastern Sichuan Basin, China

Abstract This article discusses the types and characteristics of platform margin belts on both sides of the Kaijiang-Liangping trough in the Sichuan Basin during the Late-Permian Changhsingian age combined with the seismic reflection characteristics. The results show that there are four types of platform margin belts on both sides of the Kaijiang-Liangping trough: (1) steep-slope, single-platform margin belts controlled by faults; (2) steep-slope, single-platform margin belts controlled by paleogeomorphology; (3) steep-slope, multiple-platform margin belts controlled by paleogeomorphology; and (4) gentle-slope, multiple-platform margin belts controlled by paleogeomorphology. Reefs developed in the different types of platform margin belts exhibit different morphological characteristics and stacking patterns. Among all the reefs that developed in steep-slope, platform marginal belts are mainly characterized by aggradational accretion and different degrees of lateral migration in different directions. In contrast, the reefs developed in gentle-slope platform margin belts show distinctive characteristics of multiple bandings and lateral extension. Research suggests that the differences in the platform margin belts’ structure and reefs’ development rules are jointly controlled by a combination of syn-sedimentary fault activities, paleogeomorphology, and sea-level fluctuations. These results can be used to explore and predict reef reservoirs on carbonate platform margins.

The Potential of Clay Poultices as Sorbents for Medieval Plaster: A Comparative Study Using the Pressure Plate Method and Dye

ABSTRACT Five clay poultices used in built heritage, stone, and wall painting conservation were examined for their potential to extract impurities from medieval lime-rich wall painting plaster. Since the most efficient extraction is achieved by capillary advection, this evaluation compared the pore size distribution of the clay poultices with that of medieval plaster. The pore size distribution was measured using the pressure plate method, a method with a long history of use in soil and building science. The present study demonstrates for the first time a successful application of this method in the evaluation of clay poultices for conservation. In addition, the retentive capacities of the five poultices were examined by measuring lateral migration and penetration depths as a function of time, using customised plaster samples and a blue dye to facilitate migration measurements. Of the five poultices, bentonite showed the least promising pore size range and was estimated to have little or no effect as a drying poultice for medieval wall painting plaster. The remaining four poultices showed promising results, although with various shortcomings that might influence the results of the intervention, as the best fit is dependent on the aim of the poulticing. For a cleaning poultice, where dirt is to be extracted solely from the surface of the plaster, attapulgite and PANGEL® S1500 seemed to be best suited due to their high retention. The pore size distribution and migration pattern of PANGEL® S9 and sepiolite indicated that they could be suitable as poultices for desalination.

Lateral migration of methane at a cold seep: Evidence from U–Th dating of methane-derived authigenic carbonate in the Middle Okinawa Trough

Submarine methane seepages constitute an important part of global carbon cycle and may be promoted by the dissociation of gas hydrate. The migration pattern of a seepage is commonly dominated by vertical transport of methane-rich pore fluids, and then lateral migration of these fluids probably occurred due to self-sealing effect of carbonate crust above vertical migration conduit. Some studies found the evidence of this lateral migration, but the one from the record of seep carbonate in nature is very rare. In this study, we present the results of mineralogical, isotopic, and dating analyses of a core containing seep carbonates obtained from seafloor drilling site D5 in the Middle Okinawa Trough. The core contains 0.98-m-long carbonate interval that predominantly consists of aragonite, with an average content of ∼86.6%. The carbonate exhibits moderate depletion in 13C (δ13C values: −37.2‰ to −16.3‰ Vienna Pee Dee Belemnite; VPDB) and enrichment in 18O (δ18O values: 4.3‰–5.8‰ VPDB), with relatively constant 87Sr/86Sr values (0.709167–0.709197). These results suggest that the precipitation of the seep carbonate was induced by the sulfate-driven anaerobic oxidation of methane close to the seabed and this methane could be from the dissociation of gas hydrates. U–Th age–depth profile shows that two carbonate intervals grew downwards coevally to coalesce into a thicker crust, and its upper segment also grew upwards. We interpret that lateral migration of the fluid flows at two levels are responsible for the formation of upper and lower segments of carbonate intervals because they have (a) the distinct clustering of δ13C and δ18O values and (b) a coeval period of fast growth. It is likely that upward migration of methane was redirected by self-sealing of overlying carbonate crust, leading to lateral migration at the flank of seabed mound Db4 during 6.2–4.6 ka. Our findings highlight the interaction between fluid flows and authigenic carbonates during Late Quaternary, which implies that more methane could be consumed by oxidation because it takes longer time for methane to bypass self-sealing of carbonate to escape into the ocean.

Enhanced Rectification Performance in Bipolar Janus Graphene Oxide Channels by Lateral Electric Fields.

Improving the ionic rectification in nanochannels enables versatile applications such as biosensors, energy harvesting, and fluidic diodes. While previous work mostly focused on the effect of channel geometry and surface charge, in this work via a series of molecular dynamics simulations, we find a striking phenomenon that the ionic current rectification (ICR) ratio in Janus graphene oxide (GO) channels can be tremendously promoted by lateral electric fields. First, under a given axial electric field, an additional lateral electric field can improve the ICR ratio by several times to an order, depending on the channel symmetry. The symmetric channel has an obviously greater ICR ratio because it maintains a more pronounced ion transport disparity at opposite axial fields. The underlying mechanism for the function of the lateral electric field is that it promotes the lateral migration of ions and thus amplifies the ion-residue electrostatic interaction at opposite axial fields, enlarging the ion dynamical difference. Furthermore, for different axial electric fields, the ICR ratio can always be improved by lateral electric fields (up to two orders), suggesting that the ICR improvement is universal. Our results demonstrate that applying a lateral electric field could be a new method to improve the rectification performance of nanochannels, providing valuable guidance for the design of efficient ionic diode devices.

Research on fault-controlled hydrocarbon accumulation in rifted lacustrine basins based on structural geological modeling: a case study of the Banqiao area in Bohai Bay Basin, China

The Banqiao area in the Bohai Bay Basin has experienced three stages of extensional deformation, leading to the formation of numerous fault-bound traps. Faults, acting as boundary conditions for these traps, play a crucial role in hydrocarbon accumulation. In this study, we conducted a 3D structural modeling of the area using high-resolution 3D seismic data and established a fault-reservoir database based on previous research. Our findings reveal four levels of faults in the Banqiao area: basin-controlling faults, boundary faults, derivative master faults, and secondary adjusting faults. The structural units can be categorized into subsag areas, slope areas, stress tran-sition zones, bifurcation and main incised fault zones, and southern block areas. The segmented growth of the main boundary faults controls the evolution of the subsags, with the subsidence center gradually shifting eastward from Rift Phase I to Rift Phase II, aligning with the distribution of source rocks. Fault-bound traps in the Banqiao area include single faults, intersecting faults, and side faults. Faults primarily act as barriers to lateral hydrocarbon migration during the process of hydrocarbon accumulation, while also providing pathways to a lesser extent. By integrating the fault-reservoir database with the fault system classification, we identified four types of fault-controlled hydro-carbon accumulation models: like-dipping fault barrier model, oppositely-dipping fault barrier model, intersecting fault barrier model, and reactivation-controlled secondary hydrocarbon ac-cumulation model. This structural geological model effectively demonstrates the spatial configura-tion of faults and their role in hydrocarbon accumulation in the Banqiao area. The fault control mechanisms presented in the model can also be applied to other blocks in the Bohai Bay Basin, laying a foundation for future petroleum exploration in continental rifted basins and facilitating the ap-plication of big data algorithms in various geoscientific research fields.

The Magmatic Patterns Formed by the Interaction of the Hainan Mantle Plume and Lei–Qiong Crust Revealed through Seismic Ambient Noise Imaging

Magmatism on continental lithospheres induced by mantle plumes is more complex compared to oceanic intraplate volcanism owing to the heterogeneous nature of continental crustal and lithospheric structures. Substantial evidence points to the deep-oriented Hainan mantle plume beneath the Lei–Qiong region, the southernmost of the South China block. In this study, we present a detailed shear wave velocity model of the crust and uppermost mantle in the Lei–Qiong volcanic region, derived from 3-year seismic data (2016–2018) from 34 stations and the use of the ambient noise tomography method. An evident columnar low-velocity anomaly was imaged in the crust and uppermost mantle beneath the Wushi Sag (WSS), Beibu Gulf, potentially suggesting that the center of either one branch or the entirety of the Hainan mantle plume impacts the crust here. This low-velocity anomaly is overlaid by a local Moho deepening, indicative of underplating beneath the existing crust. The Maanling–Leihuling Volcanic Field (MLVF) in northern Hainan Island, previously considered the center of the hotspot, does not exhibit such distinct velocity anomalies. Instead, subtle lower crustal anomalies beneath the MLVF are linked with the upper mantle low-velocity zone beneath the WSS. Additionally, the high-conductivity bodies beneath the MLVF indicate lateral magma transport. Earthquake swarms and deep-seated seismic events beneath the WSS further support the presence of magmatic processes. This study indicates that in the Lei–Qiong region, the interaction of the continental crust with the mantle plume centered in the WSS results in magma exhibiting both vertical ascent and lateral migration, leading to a dual low-velocity shear wave pattern in the upper crust, which significantly influences the surface volcanic activity.

High-Throughput Microfluidic Extraction of Platelet-free Plasma for MicroRNA and Extracellular Vesicle Analysis.

Cell-free RNAs and extracellular vesicles (EVs) are valuable biomarkers in liquid biopsies, but they are prone to preanalytical variabilities such as nonstandardized centrifugation or ex vivo blood degradation. Herein, we report a high-throughput and label-free inertial microfluidic device (ExoArc) for isolation of platelet-free plasma from blood for RNA and EV analysis. Unlike conventional inertial microfluidic devices widely used for cell sorting, a submicrometer size cutoff (500 nm) was achieved which completely removed all leukocytes, RBCs, platelets, and cellular debris based on differential lateral migration induced by Dean vortices. The single-step operation also reduced platelet-associated miRNAs (∼2-fold) compared to centrifugation. We clinically validated ExoArc for plasma miRNA profiling (39 samples) and identified a 7-miRNA panel that detects non-small cell lung cancer with ∼90% sensitivity. ExoArc was also coupled with size exclusion chromatography (SEC) to isolate EVs within 50 min with ∼10-fold higher yield than ultracentrifugation. As a proof-of-concept for EV-based transcriptomics analysis, we performed miRNA analysis in healthy and type 2 diabetes mellitus (T2DM) subjects (n = 3 per group) by coupling ExoArc and ExoArc+SEC with quantitative polymerase chain reaction (RT-qPCR) assay. Among 293 miRNAs detected, plasmas and EVs showed distinct differentially expressed miRNAs in T2DM subjects. We further demonstrated automated in-line EV sorting from low volume culture media for continuous EV monitoring. Overall, the developed ExoArc offers a convenient centrifugation-free workflow to automate plasma and EV isolation for point-of-care diagnostics and quality control in EV manufacturing.

Magnetophoresis-Enhanced Elasto-Inertial Migration of Microparticles and Cells in Microfluidics.

Microfluidic particle and cell manipulation techniques possess many potentials for biomedicine and healthcare. Many techniques have been developed based on active (e.g., electrical, magnetic, acoustic, and thermal) force fields and passive hydrodynamic forces (e.g., inertial and elastic lift forces). However, techniques based on a single active or passive manipulating physics cannot always meet the demands, and combining multiple physics becomes a promising strategy to promote technique flexibility and versatility. In this work, we explored the physical coupling of magnetophoresis with the elastic and inertial (i.e., elasto-inertial) lift forces for the manipulation of microparticles. Particle lateral migration was studied in a coflowing configuration of viscoelastic ferrofluid/water (sample/sheath). The particles were suspended in the viscoelastic ferrofluid and confined near the channel sidewall by a sheath flow. The coordination of magnetophoresis and elasto-inertial lift forces promoted the cross-stream migration of particles. Besides, we investigated the effect of the flow rate ratio and total flow rate on the migration of particles. Furthermore, we also investigated the effects of fluid elasticity in sample and sheath flows on particle migration using different combinations of sample and sheath flows, including Newtonian ferrofluid/water, Newtonian ferrofluid/viscoelastic fluid, and viscoelastic ferrofluid/viscoelastic coflows. Experimental results demonstrated and ascertained the promoted particle lateral migration in the PEO-based ferrofluid/water coflow. Finally, we demonstrate the proof-of-concept application of the physical coupling strategy for cell cross-stream migration and solution exchange. We envisage that this novel multiphysical coupling scheme has great potential for the flexible and versatile manipulation of microparticles and cells.

Sensitivity of a meandering lowland river to intensive landscape management: Lateral migration rates before and after watershed-scale agricultural development

Agricultural development has transformed the vegetation cover of many landscapes around the world, thereby altering water and sediment fluxes to river systems. Past work in the upper midwestern United States, particularly in areas of moderate relief, has shown that increases in water and sediment fluxes associated with agricultural development have dramatically altered river dynamics. Less is known about how agriculture has affected river dynamics, particularly rates of lateral migration, in relatively low relief landscapes of the Midwest shaped by glaciation during the Wisconsin Episode. This research examines rates of lateral migration of a channel bend along a lowland meandering river in Illinois, USA before and after agricultural development. The rate of lateral migration prior to agricultural development is estimated through dating of carbonaceous material within lateral-accretion deposits underlying distinct meander scrolls. The rate of lateral migration after agricultural development is determined from analysis of changes in river-channel position determined from survey records, aerial imagery, and digital elevation data. Average rates of migration before and after agricultural development are similar, suggesting that agricultural development has not substantially affected rates of lateral migration of the river. Some accelerated movement occurred locally following agricultural development, but this movement cannot be definitively tied to landscape transformation. Possible factors responsible for the lack of sensitivity of the river system to agricultural development include high resistance of the cohesive, tree-lined riverbanks to erosion and the low bankfull stream power per unit area of the modern river. From a management perspective, the study highlights the importance of bank vegetation in maintaining channel stability in low-relief agricultural landscapes.

Assessment of Bank Erosion, Accretion and Lateral Migration Using Remote Sensing and GIS: A Study on the Sankosh River of Himalayan Foothills

Assessment of Bank Erosion, Accretion and Lateral Migration Using Remote Sensing and GIS: A Study on the Sankosh River of Himalayan Foothills

Timescale of the Morphodynamic Feedback Between Planform Geometry and Lateral Migration of Meandering Rivers

AbstractAcross varied environments, meandering channels evolve through a common morphodynamic feedback: the sinuous channel shape causes spatial variations in boundary shear stress, which cause lateral migration rates to vary along a meander bend and change the shape of the channel. This feedback is embedded in all conceptual models of meandering channel migration, and in numerical models, it occurs over an explicit timescale (i.e., the model time step). However, the sensitivity of modeled channel trajectory to the time step is unknown. In numerical experiments using a curvature‐driven model of channel migration, we find that channel trajectories are consistent over time if the channel migrates ≤10% of the channel width over the feedback timescale. In contrast, channel trajectories diverge if the time step causes migration to exceed this threshold, due to the instability in the co‐evolution of channel curvature and migration rate. The divergence of channel trajectories accumulates with the total run time. Application to hindcasting of channel migration for 10 natural rivers from the continental US and the Amazon River basin shows that the sensitivity of modeled channel trajectories to the time step is greatest at low (near‐unity) channel sinuosity. A time step exceeding the criterion causes over‐prediction of the width of the channel belt developed over millennial timescales. These findings establish a geometric constraint for predicting channel migration in landscape evolution models for lowland alluvial rivers, upland channels coupled to hillslopes and submarine channels shaped by turbidity currents, over timescales from years to millennia.

Exploring CO2 storage with impurities in deep saline aquifers through computational experiments

This research delves into understanding how injecting gas mixtures affects the movement and destiny of CO2 components over time and space using computational experiments. The study starts by examining the thermodynamic properties of the fluids, integrating them into a reservoir model. A detailed workflow based on this model explores how various gas mixture components, alongside reservoir and engineering factors, influence CO2 migration and its behavior. Results from computational experiments reveal that N2 promotes the radial spread of CO2, yet its dissolution weakens CO2 solubility. When considering different impurity gases, H2 leads to the farthest lateral migration of CO2, followed by N2. H2S results in the shortest lateral migration due to its higher solubility. Moreover, a sensitivity analysis highlights key parameters like the ratio of injection gas mixtures (e.g., CO2: N2 = 0.25:0.75, 0.5:0.5, and 0.75:0.25), reservoir permeability (ranging from 5 mD to 500 mD), and injection rates (ranging from 10000 m3/day to 100000 m3/day) that need consideration to optimize gas mixture injection strategies in these environments. These findings contribute to a better understanding of injecting gas mixtures into deep saline aquifers, aiding in the development of more effective strategies for CO2 storage.

Evaluation of factors causing lateral migration of light non-aqueous phase liquids (LNAPLs) in onshore oil spill accidents.

Contamination of groundwater by harmful substances poses significant risks to both drinking water sources and aquatic ecosystems, making it a critical environmental concern. Most on-land spill events release organic molecules known as light non-aqueous phase liquids (LNAPLs), which then seep into the ground. Due to their low density and organic composition, they tend to float as they reach the water table. LNAPLs encompass a wide range of non-aqueous phase liquids, including various petroleum products, and can, over time, develop carcinogenic chemicals in water. However, due to frequent changes in hydraulic head, the confinement may fail to contain them, causing them to extend outward. When it contaminates water wells, people cannot reliably consume the water. The removal of dangerous contaminants from groundwater aquifers is made more challenging by LNAPLs. It is imperative to analyze the mechanisms governing LNAPL migration. As a response to this need and the associated dispersion of contaminants into adjacent aquifers, we have conducted a comprehensive qualitative literature review encompassing the years 2000-2022. Groundwater variability, soil structure, and precipitation have been identified as the three primary influential factors, ranked in the following order of significance. The rate of migration is shown to rise dramatically in response to changes in groundwater levels. Different saturation zones and confinement have a major effect on the lateral migration velocity. When the various saturation zones reach a balance, LNAPLs will stop moving. Although higher confinement slows the rate of lateral migration, it speeds up vertical migration. Beyond this, the lateral or vertical movement is also influenced by differences in the permeability of soil strata. Reduced mobility and tighter containment are the outcomes of migrating through fine-grained, low-porosity sand. The gaseous and liquid phases of LNAPLs move more quickly through coarse-grained soils. Due to the complexities and uncertainties associated with LNAPL behavior, accurately foreseeing the future spread of LNAPLs can be challenging. Although studies have utilized modeling techniques to simulate and predict LNAPL migration, the inherent complexities and uncertainties in the subsurface environment make it difficult to precisely predict the extent of LNAPL spread in the future. The granular soil structure considerably affects the porosity and pore pressure.

Exceptional preservation of three-dimensional dunes on an ancient deep-marine seafloor: implications for sedimentary processes and depositional environments

Depositional and erosional bedforms can be used to reconstruct sedimentary processes and aid palaeoenvironmental interpretations. Using exhumed deep-marine strata in the Eocene Aínsa Basin, Spain, we document a 3-dimensional package of dunes, a rarely identified bedform in deep-marine environments. Our analysis shows that the dunes have curvilinear crests in planform, with smaller superimposed oblique dunes and ripples across the stoss sides. Beds containing these dunes have two main internal divisions: a lower inversely-graded (fine-to-coarse sandstone) and predominantly structureless division, and an upper coarse-grained sandstone division with well-developed cross-stratification, which is scoured and mantled with mudclasts and coarse-grains on the stoss-side. The rugose remnant relief of the bedforms controls the location of subsequent bedforms. Following recently reported direct measurements of natural turbidity currents, we interpret the basal division as recording deposition from the dense basal head of a high-velocity turbidity current, followed by the development of dunes beneath the more sustained but relatively high-velocity and unsteady flow body that reworked the initial sandy deposit into downstream migrating dunes and scours. These dune-forming beds have been identified in different deep-water environments in the Aínsa Basin stratigraphy, including channel overbank and channel mouth settings and scour-fills. These locations suggest that the dunes were intimately tied to high-velocity flows that bypassed through channel axes before expanded and depositing in less confined channel overbank or channel mouth settings. Preservation of these dunes in the Aínsa Basin was likely enhanced by tectonically-forced lateral migration of channels, which prevented cannibalisation of bypass-zones, in combination with high aggradation rates due to confinement, or periodic supply of flows from a particularly clay-poor source area. Where identified these dune-like bedforms are considered diagnostic of substantial sediment bypass downslope to deep-water basins.