Multi-scale Heterogeneity Research Articles

Pore Structure Characterization of Undisturbed Weathered Crust Elution-Deposited Rare Earth Ore Based on X-ray Micro-CT Scanning

As an environmentally compliant hydrometallurgical process, in situ leaching is extensively used by the mining industry to recover rare earth from weathered crust elution-deposited rare earth ore. In the in situ leaching system, the pore structure plays a dominant role in the permeability of the rare earth orebody and is one of the most important factors that influence the leaching performance. To study the pore structure characteristics of the rare earth ore, an undisturbed ore sample was scanned using X-ray micro-computed tomography. Based on the image processing techniques, visualization of the pore structure was realized and several parameters of 2D and 3D pore structures, such as porosity, pore volume, length, width, aspect ratio, and orientation, were obtained and statistically analyzed. The ball-and-stick model of large pore clusters was built by the maximal ball algorithm, and some of their detailed characteristics were obtained. The results indicate that the pore structure of weathered crust elution-deposited rare earth ore exhibits a multi-scale and strong heterogeneity characteristic. The distribution characteristics of pores between the vertical direction and the horizontal direction are obviously different. The small pores are more prevalent in number, but they make only a small contribution to the total pore volume. In addition, the orientation of the pores is anisotropic in both vertical and horizontal directions. Furthermore, the ball-and-stick model reveals that large pore clusters are composed of several interconnected void spaces, and most of them are small and irregular.

Integrated outcrop and subsurface geomodeling of the Turonian Wall Creek Member of the Frontier Formation, Powder River Basin, Wyoming, USA

Inter-well heterogeneities influencing fluid migration in deltaic reservoirs are controlled by lateral lithofacies changes and vertical complexities such as low permeability thin-beds (i.e. mudstones). Subsurface tools cannot adequately predict the spatial and stratigraphic organization of these architectural elements, nor their influence on effective reservoir properties and connectivity. Our outcrop-based geomodeling study of the Turonian Wall Creek Member of the Frontier Formation in the Powder River Basin, Wyoming, USA, integrates subsurface production and flow simulation data to quantify the impact of multi-scale stratigraphic heterogeneity on analogous reservoir behavior and horizontal well design. The upscaled representation of thin-bed complexity in our 500 m × 715 m x 15 m geomodel is derived through flow simulation of internally nested, facies specific, centimeter-scale models (basic depositional element models or BDEMs). These BDEMs are populated with quantitative data of mudstone thin-bed geometries directly derived from digital outcrop measurements and measurements in the field, and aided by subsurface (core) petrophysical properties. Reservoir simulations are performed using various landing zone and completion configurations, and under both single-phase and multi-phase flow conditions history matched to subsurface production data.Results from our workflow demonstrate that, in heterolithic settings, the permeability of mudstone thin-beds impart the most significant impacts toward upscaled reservoir behavior, and deliver unique Kv/Kh flow anisotropies dependent on the governing depositional environment. Thin, laterally continuous and planar mudstone beds in the wave-and river-dominated distal delta front setting have the greatest negative effect on Kv and a minimal impact on Kh, promoting laterally continuous and vertically baffled flow units. Conversely, the more curvilinear and intersecting architectures of mudstone beds in the tidal dune facies maintain better vertical connectivity but decreased Kh compared to the wave-influenced facies. Reservoir flow is only sensitive to changes in engineering design (landing zone, well orientation, completion size) where thin-beds act as complete barriers rather than baffles to flow. Layer cake subsurface models failing to account for high-resolution stratigraphic architectures are likely to overestimate reservoir production where thin-beds act as barriers capable of appreciable reservoir compartmentalization, which in our models is more characteristic of the distal delta front setting. Synthesized results of this study are immediately applicable toward development planning in similar tight sandstone reservoirs.

Investigation of pore-type heterogeneity and its control on microscopic remaining oil distribution in deeply buried marine clastic reservoirs

Pore-type heterogeneity is a key factor controlling the distribution of microscopic remaining oil in clastic reservoirs. It is important to quantify the characteristics of pore-type heterogeneity, understand its formation mechanisms, and analyze its impact on remaining oil at microscopic scale. Here we addressed these issues by adopting a new characterization method of flow zone indicator (FZI) with conventional velocity data as input and pore aspect ratio (α) as intermediate parameter, and conducting CT scan imaging on reservoir samples with different pore types, as identified by FZI, at different levels of water injection. The results demonstrate that this method can effectively discern pore-type changes and characterize the variabilities of velocity and permeability. A value of FZI>2.1 is characteristic of lithic quartzarenite with large amount of residual primary intergranular pores, which developed mainly in a shoreface environment. Clay rim cementation prevails in this reservoir type, as it can survive compaction, inhibit quartz overgrowth, and thus preserve intergranular pores with large pore-throat radius and good connectivity. The displacement pressure of this reservoir type is low during water flooding and the water swept area is wide; as a result, the majority of clustered flows are displaced and the remaining oil is present small patches in the form of multiporous flow. Samples with FZI<1.5 represent litharenite with large amount of intragranular dissolved pores, which developed mainly in foreshore and offshore-transition zone facies. This reservoir type underwent intense compaction and dissolution, which resulted in small pore-throat radius, poor connectivity and high displacement pressure. The injected water flows along the preferential pathways with relatively small flow resistance in this reservoir type during oil displacement such that the water swept area is limited; therefore the remaining oil is present continuous characteristics in the form of clustered flow. A transition zone with 1.5 < FZI<2.1 exists between the upper two reservoir types; this contains mixed lithologies and pore types, and exhibits medium pore-throat radius, connectivity and displacement pressure. The remaining oil in this reservoir type is present in the form of clustered flow and a small amount of multiporous flow, displaying continuous characteristics or small patches. Moreover, the water displacement process mainly occurs in relatively large pore-throats, which make a major contribution to permeability in each reservoir type. The heterogeneity of these pore-throats, as indicated by fractal dimension, controls the final oil displacement efficiency. The results of this study can be broadly applied to the characterization of similar clastic reservoirs and for further research in multi-scale heterogeneity.

Size effects in random fiber networks controlled by the use of generalized boundary conditions

Materials with a stochastic fiber network as the main structural constituent are broadly encountered in engineering and in biology. These materials are characterized by multiscale heterogeneity and hence their properties evaluated numerically or experimentally are generally dependent on the size of the sample considered. In this work we evaluate the size effect on the linear and non-linear mechanical response of three-dimensional stochastic fiber networks and determine its dependence on material parameters and on the degree of affinity of network deformation. The size effect is more pronounced in non-affine networks than in affine networks and decreases slowly when the model size increases. In order to eliminate this effect, models lager than can be effectively solved with current computers have to be considered. To address this issue, we propose a method that allows using relatively small models, while accurately predicting the small and large strain behaviors of the network. The method is based on the generalized boundary conditions introduced in (Glüge 2013, Computational Materials Science 79, 408–416), which are being adapted here to the requirements imposed by fibrous materials.

Radiogenomic signatures reveal multiscale intratumour heterogeneity associated with biological functions and survival in breast cancer

Advanced tumours are often heterogeneous, consisting of subclones with various genetic alterations and functional roles. The precise molecular features that characterize the contributions of multiscale intratumour heterogeneity to malignant progression, metastasis, and poor survival are largely unknown. Here, we address these challenges in breast cancer by defining the landscape of heterogeneous tumour subclones and their biological functions using radiogenomic signatures. Molecular heterogeneity is identified by a fully unsupervised deconvolution of gene expression data. Relative prevalence of two subclones associated with cell cycle and primary immunodeficiency pathways identifies patients with significantly different survival outcomes. Radiogenomic signatures of imaging scale heterogeneity are extracted and used to classify patients into groups with distinct subclone compositions. Prognostic value is confirmed by survival analysis accounting for clinical variables. These findings provide insight into how a radiogenomic analysis can identify the biological activities of specific subclones that predict prognosis in a noninvasive and clinically relevant manner.

Development of a hydrodynamic model and the corresponding virtual software for dual-loop circulating fluidized beds

Dual-loop circulating fluidized bed (CFB) reactors have been widely applied in industry because of their good heat and mass transfer characteristics and continuous handling ability. However, the design of such reactors is notoriously difficult owing to the poor understanding of the underlying mechanisms, meaning it has been heavily based on empiricism and stepwise experiments. Modeling the gas-solid CFB system requires a quantitative description of the multiscale heterogeneity in the sub-reactors and the strong coupling between them. This article proposed a general method for modeling multiloop CFB systems by utilizing the energy minimization multiscale (EMMS) principle. A full-loop modeling scheme was implemented by using the EMMS model and/or its extension models to compute the hydrodynamic parameters of the sub-reactors, to achieve the mass conservation and pressure balance in each circulation loop. Based on the modularization strategy, corresponding interactive simulation software was further developed to facilitate the flexible creation and fast modeling of a customized multi-loop CFB reactor. This research can be expected to provide quantitative references for the design and scale-up of gas-solid CFB reactors and lay a solid foundation for the realization of virtual process engineering.

Continuous Dissolved Gas Tracing of Fracture‐Matrix Exchanges

AbstractTransport in fractured media plays an important role in a range of processes, from rock weathering and microbial processes to contaminant transport, and energy extraction and storage. Diffusive transfer between the fracture fluid and the rock matrix is often a key element in these applications. But the multiscale heterogeneity of fractures renders the field assessment of these processes extremely challenging. This study explores the use of dissolved gases as tracers of fracture‐matrix interactions, which can be measured continuously and highly accurately using mobile mass spectrometers. Since their diffusion coefficients vary significantly, multiple gases are used to probe different scales of fracture‐matrix exchanges. Tracer tests with helium, xenon, and argon were performed in a fractured chalk aquifer, and resulting tracer breakthrough curves are modeled. Results show that continuous dissolved gas tracing with multiple tracers provides key constrains on fracture‐matrix interactions and reveal unexpected scale effects in fracture‐matrix exchange rates.

Flow Channeling in Fracture Networks: Characterizing the Effect of Density on Preferential Flow Path Formation

AbstractFlow channelization is a commonly observed phenomenon in fractured subsurface media where the flow of fluids is restricted primarily to highly transmissive fracture networks surrounded by a low‐permeability rock matrix. The multiscale structural heterogeneity of these networks results in multiscale flow channelization where preferential flow paths form at length scales ranging from the entire system down to the subfracture size. We present an analysis of how one of the largest scales in fractured media, the network density, influences the degree of flow channeling that occurs using an ensemble of semigeneric three‐dimensional discrete fracture network (DFN) simulations. We construct 10 DFNs, whose fracture lengths follow a power law distribution, at four densities for a total of 40 networks. We characterize their structure in terms of the network topology and geometry. Eulerian and Lagrangian observations of the steady‐state flow fields obtained within the networks are used to quantify the degree of flow channelization at the network scale. We introduce a measure for the importance‐ranking/hierarchy of different flow paths in the network using graph‐based analysis of Lagrangian transport by which the degree of flow channeling between networks is compared. These flow observations are then linked to the structural properties of the networks. In general, network‐scale flow channeling decreases as the network density increases. However, at low densities, there is more uniform flow within the entire connected network than in high‐density networks. We also demonstrate how standard transport observables can be used to infer the degree of flow channelization occurring within a fracture network.

Full-scale nanopore system and fractal characteristics of clay-rich lacustrine shale combining FE-SEM, nano-CT, gas adsorption and mercury intrusion porosimetry

Shale pore structures and irregularities are significant for gas adsorption and interstifial flow. High complexity and nonuniformity, wide pore scales, and multiple morphology hinder the thorough characterization of multi-scale pore structure and heterogeneity in shales. In this work, the geochemistry, pore structure and fractal characteristics of the Upper Cretaceous Nenjiang shale in the Songliao Basin of NE China were investigated, combining geochemistry experiments, physical property analysis, FE-SEM and nano-CT image observation, CO2/N2 gas adsorption, mercury intrusion porosimetry, and methane methane sorption analysis. The results show that the Nenjiang shales are low-mature (Ro of 0.55%–0.93%) and rich in organic matters (OMs) and clays. The size diameters of shale pores are generally distributed in sizes of 0.3–0.8, 1.4–4.5, 80–600 nm and 10–80 μm. Shale pores have strong heterogeneity and complexity, good connectivity and openness, mainly with inkbottle- and slit-shapes. Total pore volume (PV) is positive correlate with specific surface area (SSA), porosity and permeability, but negative correlate with the average pore size. The development of micro-, meso-, and macro-pores were dominated by the contents of OM, clays, and quartz, respectively. Positive correlations were found among fractal dimension, contents of OMs and clays, total PV, SSA, and methane adsorption capacity, which would provides better understanding on reservoir assessment and shale gas storage capacity.

Heterogeneous Behavior of Lithium Plating during Extreme Fast Charging

Summary Broad use of global or spatially averaging measurements over a cell to characterize highly localized Li plating phenomena in lithium-ion batteries during fast charging has created a disconnect between measurements and the underlying causes. Consequently, the field is missing a clear path to implementing fast charging as well as to expand into extreme fast charging (XFC). Aiming to bridge these gaps, we present a detailed look into local detection of Li plating and the consequent cycle life implications for electrodes and cells under XFC by utilizing electrochemistry and high-energy X-ray diffraction. Significant heterogeneity in Li plating during XFC results in accelerated and non-uniform cycle life losses, in contrast to the prevailing acceptance that C rate is correlated to Li plating for XFC. This behavior is triggered by local electrode heterogeneity, which has yet to be identified and is not apparent in volume-averaged quantifications. A better understanding of these multiscale local electrode heterogeneities is crucial for identifying pathways to enable XFC.

Short- and Long-Term Effects of X-ray Synchrotron Radiation on Cotton Paper.

X-ray analytical techniques are increasingly being used to study manuscripts and works of art on paper, whether with laboratory equipment or synchrotron sources. However, it is difficult to anticipate the impact of X-ray photons on paper- and cellulose-based artifacts, particularly due to the large variety of their constituents and degradation levels, and the subsequent material multiscale heterogeneity. In this context, this work aims at developing an analytical approach to study the modifications in paper upon synchrotron radiation (SR) X-ray radiation using analytical techniques, which are fully complementary and highly sensitive, yet not frequently used together. At the molecular scale, cellulose chain scissions and hydroxyl free radicals were measured using chromatographic separation techniques (size-exclusion chromatography-multiangle laser light scattering-differential refractive index (SEC-MALS-DRI) and reversed-phase high-performance liquid chromatography-fluorescence detector-diode array detector (RP-HPLC-FLD-DAD)), while the optical properties of paper were characterized using spectroscopy (UV luminescence and diffuse reflectance). These techniques showed different sensitivities toward the detection of changes. The modifications in the cellulosic material were monitored in real time, within a few days, and up to 2 years following the irradiation to define a lowest observed adverse effect dose (LOAED). As paper is a hygroscopic material, the impact of the humidity in the environment was studied using this approach. Three levels of moisture content in the paper, achieved by conditioning the samples and irradiating them at different relative humidities (RHs), were studied (0, 50, 80% RH). It was shown that very low moisture content accelerated molecular and optical modifications.

Multi-scale spatial heterogeneity enhances particle clearance in airway ciliary arrays.

Mucus clearance constitutes the primary defence of the respiratory system against viruses, bacteria and environmental insults [1]. This transport across the entire airway emerges from the integrated activity of thousands of multiciliated cells, each containing hundreds of cilia, which together must coordinate their spatial arrangement, alignment and motility [2, 3]. The mechanisms of fluid transport have been studied extensively at the level of an individual cilium [4, 5], collectively moving metachronal waves [6-10], and more generally the hydrodynamics of active matter [11, 12]. However, the connection between local cilia architecture and the topology of the flows they generate remains largely unexplored. Here, we image the mouse airway from the sub-cellular (nm) to the organ scales (mm), characterising quantitatively its ciliary arrangement and the generated flows. Locally we measure heterogeneity in both cilia organisation and flow structure, but across the trachea fluid transport is coherent. To examine this result, a hydrodynamic model was developed for a systematic exploration of different tissue architectures. Surprisingly, we find that disorder enhances particle clearance, whether it originates from fluctuations, heterogeneity in multiciliated cell arrangement or ciliary misalignment. This resembles elements of 'stochastic resonance' [13-15], in the sense that noise can improve the function of the system. Taken together, our results shed light on how the microstructure of an active carpet [16, 17] determines its emergent dynamics. Furthermore, this work is also directly applicable to human airway pathologies [1], which are the third leading cause of deaths worldwide [18].

Thermal core profiling as a novel and accurate method for efficient characterization of oil reservoirs

The paper describes a new approach for obtaining detailed experimental data on the thermal properties of hydrocarbon reservoirs using continuous non-contact non-destructive high-resolution thermal conductivity and volumetric heat capacity profiling throughout the borehole core samples. The approach can offer representative experimental data on multi-scale heterogeneity of reservoirs and their anisotropy. Combination of the new approach with traditional well-logging methods offers more detailed data on variations of porosity and density of rock, its mineral composition, elastic wave velocity, and physical properties of the rock matrix. The work illustrates a case study of the new method application: continuous non-destructive non-contact high-resolution profiling of thermal properties was carried out for approximately 3000 core samples from two boreholes drilled through Carboniferous-Permian strata of the Usinskoye heavy oil field. The profiling provided detailed data on the thermal conductivity zoning, volumetric heat capacity, the coefficient of thermal anisotropy and heterogeneity factor of the rock. The knowledge of these properties is essential for hydrodynamic simulation of the heat and mass transfer processes in the reservoir when conducting thermal enhanced oil recovery. The experimental results revealed considerable variations in the set of thermal properties along boreholes on micro and macro scales. This suggests new opportunities for in-depth analysis of reservoir heterogeneity when studying the geological structure of the oil field. The work shows that application of thermal core profiling can provide details (unreachable for standard well logging techniques) of porosity variations and establish new correlations between thermal conductivity, on the one hand, and density and elastic wave velocity, on the other. That promises to improve the quality of geo-mechanical and geothermal investigations.

Spatial Heterogeneity of Socioeconomic Data: Multiscale Approach and Generalization

The paper discusses the features of applying multiscale approach in studies of spatial heterogeneity. We analyze socioeconomic indicators for different scales of spatial organization in Russia: municipalities, regions (federal subjects), and economic areas (‘economicheskiy rayon’). It is established that more discrete levels of subdivisions, in accordance with statistics theory, have higher levels of heterogeneity. Based on our calculations, we demonstrate that the evaluation of heterogeneity indices for the same territories when applying different grids is combined with partial distortion of these indices. Such errors are explained by the continuity of the geographical space and the failure tos unambiguously determine the true geographical boundaries. We propose a generalization coefficient, a proportion of heterogeneity indices at different scale levels, which enables to assess multiscale spatial heterogeneity. The coefficient provides a means of distinguishing scale levels with the greatest diversity of territories. In addition, this coefficient can be used to differentiate between ‘statistical’ heterogeneity, which is explained by the number of elements in a system, and ‘actual’ (geographical) heterogeneity. A case study of estimating heterogeneity for E.E. Leizerovich’s microzoning grid revealed that the ‘actual’ heterogeneity level can be significantly lower than the one, evaluated using traditional calculations. We provide examples of practical use for the coefficient, e.g., it enables to assess the validity of typologies and elaborate more detailed projections for discrete grids (so called ‘small areas’).

Reservoir Characterization and Multiscale Heterogeneity Analysis of Cretaceous Reservoir in Punjab Platform of Middle Indus Basin, Pakistan

The reservoir character of Cretaceous prolific clastic rocks, widely distributed in different sedimentary basins of Pakistan, is poorly established due to its heterogeneous behavior. In this study, electrofacies classification, principal component analysis, cluster analysis, and petrophysical analysis were performed to establish reservoir character of the Lumshiwal Formation. The electrofacies analysis reveals that the Lumshiwal Formation contains: clean sands with blocky log behavior, shaly sands with intercalated shale beds, sandy shales, and shale. Petrophysical analysis was accomplished by using standard practices with the help of wireline logs of fifteen wells drilled in the study area. After wireline logs and core sample calibration, the Lumshiwal Formation was divided into A, B, and C zones with an effective porosity 5–32% in zone A, 12–17% in zone B, and 13–27% in zone C with high permeability and very low volume of shale. The results revealed that Lumshiwal Formation represents relatively a vertically and laterally heterogeneous sedimentary unit with good quality reservoir facies, which were deposited in shallow marine environment with upward coarsening grain size.

Linking the morphology and ecology of subtidal soft-bottom marine benthic habitats: A novel multiscale approach

High-resolution surveying techniques of subtidal soft-bottom seafloor habitats show higher small-scale variation in topography and sediment type than previously thought, but the ecological relevance of this variation remains unclear. In addition, high-resolution surveys of benthic fauna show a large spatial variability in community composition, but this has yet poorly been linked to seafloor morphology and sediment composition. For instance, on soft-bottom coastal shelves, hydrodynamic forces from winds and tidal currents can cause nested multiscale morphological features ranging from metre-scale (mega)ripples, to sand waves and kilometre-scale linear sandbanks. This multiscale habitat heterogeneity is generally disregarded in the ecological assessments of benthic habitats. We therefore developed and tested a novel multiscale assessment toolbox that combines standard bathymetry, multibeam backscatter classification, video surveying of epibenthos and box core samples of sediment and macrobenthos. In a study on the Brown Bank, a sandbank in the southern North Sea, we found that these methods are greatly complementary and allow for more detail in the interpretation of benthic surveys. Acoustic and video data characterised the seafloor surface and subsurface, and macrobenthos communities were found to be structured by both sandbank and sand wave topography. We found indications that acoustic techniques can be used to determine the location of epibenthic reefs. The multiscale assessment toolbox furthermore allows formulating recommendations for conservation management related to the impact of sea floor disturbances through dredging and trawling.

Experimental investigation of multi-scale strain-field heterogeneity in rocks

Rocks have inherently heterogeneous micro-structures. The mechanical response of these heterogeneous micro-structures primarily governs the overall macroscopic behavior of intact rocks, as these features cause heterogeneity in the distribution of stress and strain within a rock volume. These attributes have generally been studied through numerical tools, but in this study, the stress-induced multi-scale spatial heterogeneity in the strain-field of three types of rocks was analyzed experimentally. The full-field non-contact strain measurement approach of 2D Digital Image Correlation (DIC) was employed for real-time evaluation of the progression of strain-field heterogeneity across the surface of the rock specimens when subjected to uniaxial compression. The results show that the strain-field heterogeneity is a characteristic of the inherent heterogeneity of the rock specimens, and that it amplifies with the magnitude of stress applied on the rock specimens. The changes in the strain-field heterogeneity with loading were consistent with established microcrack evolution processes in the rock specimens. The statistical fluctuation in the strain-field heterogeneity of the three rocks at varying gauge lengths (GL) was then analyzed for the determination of the Representative Volume Element (RVE) length-scale at increasing load levels. The evolution of the RVE length-scale with loading facilitates an objective way of determination of the stress at which the strain-field heterogeneity increases and begins to influence the overall global response of the material. The RVE length-scale variation with loading showed that at the RVE length-scale reaches the specimen-scale at load levels well below the peak strength.

Deformation-Enhanced Hierarchical Multiscale Structure Heterogeneity in a Pd-Si Bulk Metallic Glass

The multiscale structures in a Pd82Si18 binary bulk metallic glass before and after bending were studied using electron microscopy, high-energy synchrotron X-ray diffraction, and small-angle X-ray scattering. The experimental results revealed the enhancement of hierarchical structure heterogeneities on multiple length scales after deformation. Hierarchical multiple shear bands of high number density can be observed after bending, introducing complex but periodically distributed residual strain. Pair distribution function analysis revealed that the connectivity of the short-range cluster on the medium-range scale determines the packing density difference between the tension side and the compression side in the sample after bending. The electron density fluctuations on the nanoscale observed in the deformed part of the sample are indicative of a nanoscale amorphous phase separation induced by plastic deformation. Our findings will deepen the understanding of the plastic deformation mechanism of metallic glasses and shed light on designing glassy alloys of excellent plasticity and toughness through hierarchical multiscale structure heterogeneities.

Challenges with effective representations of heterogeneity in soil hydrology based on local water content measurements

AbstractThe description of soil water movement at the field scale requires soil hydraulic material properties. These cannot be measured directly and exhibit an intrinsic multiscale heterogeneity. The estimation of soil hydraulic properties through inverse modeling or data assimilation requires measurements of the state of the system. However, these measurements are typically scarce and do not resolve soil heterogeneity leading to effective material properties with limited predictive capabilities. In a synthetic study at the scale of soil profiles, we explore the possibility to estimate an effective reduced one‐dimensional representation based on only four local water content measurements in a vertical profile located in one‐ and two‐dimensional heterogeneous media. We allow the effective material properties to deviate locally to consider the impact of the small‐scale heterogeneity on the water content measurements. In the synthetic experiments, the estimated reduced one‐dimensional representations predict soil water content and fluxes sufficiently well but can fail to predict the accurate timing and magnitude of infiltration fronts. Cumulative fluxes below the water content measurements were predicted correctly even on short time scales, if evaporation was estimated accurately. However, this proved to be challenging if the local evaporation fluxes above the measurement profile deviated strongly from the average evaporation fluxes of the heterogeneous medium. The one‐dimensional estimation leads to soil hydraulic parameters describing effective material properties that differ from the true material properties to compensate the missing representation of heterogeneity and two‐dimensional flow.

Multiscale petrographic heterogeneity and their implications for the nanoporous system of the Wufeng-Longmaxi shales in Jiaoshiba area, Southeast China: Response to depositional-diagenetic process

Abstract The organic matter-rich shales in Wufeng-Longmaxi Formation, Jiaoshiba area, Southeast China, are showing a notable petrographic heterogeneity characteristic within the isochronous stratigraphic framework, which lead to vast differences in the mineral composition and organic matter abundance in the adjacent sections of the shale reservoir. The studied shale has been divided into three systems tracts: a transgressive systems tract (TST), an early highstand systems tract (EHST), and a late highstand systems tract (LHST). Multiple-scale petrographic observation and detailed mineralogical and geochemical analyses were combined to investigate the manifestation, origin, and the ways by which the shale heterogeneity is affected. The results indicate that polytropic depositional environments lead to different components in sediment. Subsequently, these differences among shale sections become more apparent through different diagenetic pathways. During the deposition of the section TST, the Hirnantian glaciation and regional volcanism played a crucial role, contributing to the abundant accumulation of fine-grained intrabasinal silica and organic matter. In diagenesis stage, authigenic quartz aggregates derived from siliceous organisms are formed. They filled in primary interparticle pores, forming a rigid particle-bracing structure that provide effective resistivity against the compaction and spaces for organic matter migration and occlusion. Finally, the migrated organic matter left plenty of newly created pore spaces that constituted a great portion of the total porosity of shale reservoir. The depositional process of section EHST is strongly influenced by contour current, which brings about more extrabasinal influx and impoverishes organic matter. In diagenesis stage, the rigid particle-bracing structure could only be preserved in limited areas, since insufficient siliceous supply could not produce enough authigenic quartz. Primary interparticle pores are significantly reduced owing to compaction, leaving less space for later organic matter migration and occlusion. As a result, the total porosity of shale reservoir declines in this section. In a rapid tectonic-uplifting background, the deposition of section LHST is associated with a rapid increase in terrigenous clay minerals, which further dilutes organic matter. Ductile clay experienced strong compaction and then occupies most of the primary interparticle space. Rigid particles are wrapped by a large number of clays, which has destroyed the particle-bracing structure. As a result, the nanoporous system in the shale could not be well preserved.