Multi-scale Heterogeneity Research Articles

Bringing diversity back to agriculture: Smaller fields and non-crop elements enhance biodiversity in intensively managed arable farmlands

Agricultural intensification has substantially reduced multi-scale habitat heterogeneity, including increased field size and loss of semi-natural structures, thus resulting in large-scale deterioration of farmland biodiversity. Biodiversity conservation in farmland has therefore become a conservation priority on a regional as well as continental scale. The effect of habitat heterogeneity on biodiversity on different trophic and niche levels is poorly understood, particularly in agricultural regions with simple arable patterns, where biodiversity has declined most conspicuously. To investigate the effects of habitat heterogeneity on biodiversity in an intensively managed arable-dominated agricultural landscape, we measured the abundance and species richness of spiders, butterflies, birds and European hares as well as the fine-scale habitat composition on various spatial scales. Additionally, we examined correlations between species richness and abundance among taxonomic groups to investigate if any of the biodiversity parameters provided a good indicator of overall farmland biodiversity. We found that smaller patch sizes and larger areas of non-cropped elements (margins, hedges and grasslands) were related to higher farmland biodiversity of different taxonomic groups but habitat diversity was not. The positive effect of these factors was recorded on both spatial scales and in a separate analysis considering groups with different habitat requirements and dispersal abilities. Biodiversity parameters (i.e. species richness and abundance) of the taxonomic groups were positively correlated with one another. In particular, butterfly species richness correlated with bird, butterfly and spider abundance and with bird species richness, suggesting that it may be a good indicator of general farmland biodiversity in intensively managed arable landscapes. Our results suggest that enhancing the heterogeneity of farmed landscapes by decreasing field size and increasing the availability of non-cropped habitats may be a valuable tool for conserving farmland biodiversity in intensive arable farmlands.

Non-empirical identification of trigger sites in heterogeneous processes using persistent homology

Macroscopic phenomena, such as fracture, corrosion, and degradation of materials, are associated with various reactions which progress heterogeneously. Thus, material properties are generally determined not by their averaged characteristics but by specific features in heterogeneity (or ‘trigger sites’) of phases, chemical states, etc., where the key reactions that dictate macroscopic properties initiate and propagate. Therefore, the identification of trigger sites is crucial for controlling macroscopic properties. However, this is a challenging task. Previous studies have attempted to identify trigger sites based on the knowledge of materials science derived from experimental data (‘empirical approach’). However, this approach becomes impractical when little is known about the reaction or when large multi-dimensional datasets, such as those with multiscale heterogeneities in time and/or space, are considered. Here, we introduce a new persistent homology approach for identifying trigger sites and apply it to the heterogeneous reduction of iron ore sinters. Four types of trigger sites, ‘hourglass’-shaped calcium ferrites and ‘island’- shaped iron oxides, were determined to initiate crack formation using only mapping data depicting the heterogeneities of phases and cracks without prior mechanistic information. The identification of these trigger sites can provide a design rule for reducing mechanical degradation during reduction.

Geologic Modeling of Eagle Ford Facies Continuity Based on Outcrop Images and Depositional Processes

Summary Geologic modeling of mudrock reservoirs is complicated by the presence of multiscale heterogeneities and lithofacies lateral discontinuity. The resolution of wireline logs is also too low to capture many small-scale heterogeneities that affect fluid flow. In addition, the large distance between logged wells results in uncertain long-range correlations. Supplementary to wireline log data, high-resolution outcrop images offer a direct representation of detailed heterogeneities and lithofacies connectivity. We used high-resolution panoramic outcrop images to collect data on lithofacies heterogeneity and the role that depositional processes play in this heterogeneity. We then used these data in different classes of reservoir algorithms—two-point-based, object-based, and higher-order statistics—to build a geologic model. To present our methodology, we used data collected from Eagle Ford outcrops in west Texas. We found the higher-order-statistics method to be especially efficient, capable of reproducing details of heterogeneity and lithofacies connectivity.

Application of Tempered-Stable Time Fractional-Derivative Model to Upscale Subdiffusion for Pollutant Transport in Field-Scale Discrete Fracture Networks

Fractional calculus provides efficient physical models to quantify non-Fickian dynamics broadly observed within the Earth system. The potential advantages of using fractional partial differential equations (fPDEs) for real-world problems are often limited by the current lack of understanding of how earth system properties influence observed non-Fickian dynamics. This study explores non-Fickian dynamics for pollutant transport in field-scale discrete fracture networks (DFNs), by investigating how fracture and rock matrix properties influence the leading and tailing edges of pollutant breakthrough curves (BTCs). Fractured reservoirs exhibit erratic internal structures and multi-scale heterogeneity, resulting in complex non-Fickian dynamics. A Monte Carlo approach is used to simulate pollutant transport through DFNs with a systematic variation of system properties, and the resultant non-Fickian transport is upscaled using a tempered-stable fractional in time advection–dispersion equation. Numerical results serve as a basis for determining both qualitative and quantitative relationships between BTC characteristics and model parameters, in addition to the impacts of fracture density, orientation, and rock matrix permeability on non-Fickian dynamics. The observed impacts of medium heterogeneity on tracer transport at late times tend to enhance the applicability of fPDEs that may be parameterized using measurable fracture–matrix characteristics.

Statistical scale-up of 3D particle-tracking simulation for non-Fickian dispersive solute transport modeling

Numerical techniques for subsurface flow and transport modeling are often limited by computational limitations including fine mesh and small time steps to control artificial dispersion. Particle-tracking simulation offers a robust alternative for modeling solute transport in subsurface formations. However, the modeling scale usually differs substantially from the rock measurement scale, and the scale-up of measurements have to be made accounting for the pattern of spatial heterogeneity exhibited at different scales. Therefore, it is important to construct accurate coarse-scale simulations that are capable of capturing the uncertainties in reservoir and transport attributes due to scale-up. A statistical scale-up procedure developed in our previous work is extended by considering the effects of unresolved (residual) heterogeneity below the resolution of the finest modeling scale in 3D. First, a scale-up procedure based on the concept of volume variance is employed to construct realizations of permeability and porosity at the (coarse) transport modeling scale, at which flow or transport simulation is performed. Next, to compute various effective transport parameters, a series of realizations exhibiting detailed heterogeneities at the fine scale, whose domain size is the same as the transport modeling scale, are generated. These realizations are subjected to a hybrid particle-tracking simulation. Probabilistic transition time is considered, borrowing the idea from the continuous time random walk (CTRW) technique to account for any sub-scale heterogeneity at the fine scale level. The approach is validated against analytical solutions and general CTRW formulation. Finally, coarse-scale transport variables (i.e., dispersivities and parameterization of transition time distribution) are calibrated by minimizing the mismatch in effluent history with the equivalent averaged models. Construction of conditional probability distributions of effective parameters is facilitated by integrating the results over the entire suite of realizations. The proposed method is flexible, as it does not invoke any explicit assumption regarding the multivariate distribution of the heterogeneity. In contrast to other hierarchical CTRW formulation for modeling multi-scale heterogeneities, the proposed approach does not impose any length scale requirement regarding sub-grid heterogeneities. In fact, it aims to capture the uncertainty in effective reservoir and transport properties due to the presence of heterogeneity at the intermediate scale, which is larger than the finest resolution of heterogeneity but smaller than the representative elementary volume, but it is often comparable to the transport modeling scale.

Role of multiscale heterogeneity in fault slip from quasi-static numerical simulations

Quasi-static numerical simulations of slip along a fault interface characterized by multiscale heterogeneity (fractal patch model) are carried out under the assumption that the characteristic distance in the slip-dependent frictional law is scale-dependent. We also consider slip-dependent stress accumulation on patches prior to the weakening process. When two patches of different size are superposed, the slip rate of the smaller patch is reduced when the stress is increased on the surrounding large patch. In the case of many patches over a range of scales, the slip rate on the smaller patches becomes significant in terms of both its amplitude and frequency. Peaks in slip rate are controlled by the surrounding larger patches, which may also be responsible for the segmentation of slip sequences. The use of an explicit slip-strengthening-then-weakening frictional behavior highlights that the strengthening process behind small patches weakens their interaction and reduces the peaks in slip rate, while the slip deficit continues to accumulate in the background. Therefore, it may be possible to image the progress of slip deficit at larger scales if the changes in slip activity on small patches are detectable.

Digital coal: Generation of fractured cores with microscale features

Coal is highly heterogeneous at multiple scales, such that the characterisation of coal lags behind that of conventional reservoir rocks. This paper demonstrates the capability of a digital coal model that can be used to characterise the multiscale structure of coal as well as its petrophysical properties at the core scale (cm). X-ray micro-computed tomography (micro-CT) is applied to obtain the internal cleat structure of a heterogeneous fractured coal sample, based on which statistics of coal lithotype distributions and cleat geometrical properties are extracted. Digital coal models are constructed stochastically according to the measured statistics. Resulting models preserve the core scale (cm) heterogeneity and pore scale (µm to mm) cleat properties of the imaged coal sample. Furthermore, petrophysical evaluation is performed based on the stochastic digital coal models. We find that the generated digital coal models can provide permeability estimation with errors of 26.7% in comparison to that of the original micro-CT data. Since the presented model is able to preserve the multiscale heterogeneities as well as petrophysical properties of coal, our work provides an alternative to segmented micro-CT images. Therefore, we can avoid the challenges that are inherent to micro-CT images, such as segmentation errors, size and resolution limitations. The digital coal model can also be a tool of linking the rock microstructure to petrophysical properties at the core scale, such that we can predict the permeability of coal based on its geometrical measures rather than expensive laboratory experiments.

Analysis of gold in rock samples using laser-induced breakdown spectroscopy: Matrix and heterogeneity effects

We used the laser-induced breakdown spectroscopy (LIBS) technique to determine the concentration of gold in rock samples. 44 reference materials (mostly compressed fine powders) of various chemical compositions, with a quasi-homogeneous concentration of gold varying from 0 to 1000ppm, were used to establish the calibration curve for the Au I 267.59nm line. A chemometric study based on the principal component analysis (PCA) showed that ~83% of the LIBS spectra variations are attributable to the presence of iron in the samples. Two distinct branches were obtained in the calibration curve: one for Si-rich samples (<5% of iron) and one for Fe-rich samples (>13% of iron) with limits of detection of 0.8ppm and 1.5ppm, respectively. Different normalization schemes of the gold signal were tested in order to reduce the matrix effects. The LIBS analysis was performed on various mineral samples of practical interest, namely two Si-rich uncompressed ore powders, fine and granular, and three bulk drill cores. The fluctuations in the gold concentration measurements appear to be about two times greater in the granular powder (5–10%) than in the fine one (2–5%). A detailed mapping of the gold concentration on a solid drill core was also performed, revealing multiscale heterogeneity of the gold distribution on the surface of the sample.

A review of applications of fractional calculus in Earth system dynamics

Fractional calculus has been used to model various hydrologic processes for 15years. Yet, there are still major gaps between real-world hydrologic dynamics and fractional-order partial differential equations (fPDEs). In addition, the applicability of fPDEs in the broad field of Earth dynamics remains obscure. This study first reviews previous applications and then identifies new research directions for fPDEs simulating non-Fickian transport in both surface and subsurface hydrology. We then explore the applicability of fractional calculus in various anomalous dynamics with a wide range of spatiotemporal scales observed in the solid Earth, including internal dynamics (such as inner core rotation, outer core flow, mantle convection, and crustal deformation), large-scale surface dynamics (in fluvial, Aeolian, and glacial systems), and small vertical-scale surface kinetics (in crystal growth, rock/mineral weathering, and pedogenesis), where driven forces, previous modeling approaches, and the details of anomalous dynamics are analyzed. Results show that the solid Earth can provide an ideal and diverse base for the application of fractional calculus and fPDEs. Complex dynamics within and across spatiotemporal scales, multi-scale intrinsic heterogeneity, and intertwined controlling factors for dynamic processes in the solid Earth can motivate the application of fPDEs. Challenges for the future application of fPDEs in Earth systems are also discussed, including poor parameter predictability, the lack of mathematical specification of bounded fractional diffusion, lack of intermediate-scale geologic information in parsimonious and upscaling models, and a lack of models for multi-phase and coupled processes. Substantial extension of fPDE models is needed for the development of next-generation, solid Earth dynamic models, where potential solutions are discussed based on our experience gained in the development and application of fractional calculus and fPDEs over the last decade. Therefore, the current bottleneck in the application of fractional calculus in hydrologic sciences should not be the end of a promising stochastic approach, but could be the early stage of a decade-long effort filled with multiple new research and application directions in geology. This conclusion may shed light on the bottleneck challenging stochastic hydrogeology, where the advanced stochastic models (with more than 3500 journal publications in the last three decades) have not significantly impacted the practice of groundwater flow and transport modeling.

Multiscale Gilbert-type delta lobe architecture and heterogeneities: The case of the Roda Sandstone Member

ABSTRACT The Roda Sandstone Member (Lower Eocene, Tremp-Graus Basin, Spanish Pyrenees) is interpreted as a well-exposed multiscale Gilbert-type delta. It is formed by multiple prograding lobate-shaped sandstone bodies up to 5 km (3 mi) long and 2–3 km (1–2 mi) wide, each constructed by a number of smaller scale (hunderds of meters) lobes that stack in a compensational mode responding to relative base level changes. In general, the proximal part of each lobe is dominated by trough cross stratification, the medial part by impressive clinoforms, and the distal part by more tabular cross stratification. Well-developed tidal bundles occur abundantly in delta lobe-front attached and detached tidal bars; the latter are up to 5 km (3 mi) long and 2 km (1 mi) wide. Cemented layers cover both the individual lobes as well as the lobate-shaped sandstone bodies. The three-dimensional (3-D) architecture of small-scale (decimeter to meter) heterogeneities at lithofacies scale formed by millimeter- to centimeter-thick mud layers in the tidal bars have been studied to better understand hydrocarbon flow through heterolithic tide-dominated successions. The Roda Sandstone has been used as an analog to many oil and gas fields with a particular focus on 3-D lobe geometry, compartmentalization, stacking patterns, and associated correlation concepts.

A fully subordinated linear flow model for hillslope subsurface stormflow

AbstractHillslope subsurface stormflow exhibits complex patterns when natural soils with multiscale heterogeneity impart a spatiotemporally nonlocal memory on flow dynamics. To efficiently quantify such nonlocal flow responses, this technical note proposes a fully subordinated flow (FSF) equation where the time‐ and flow‐subordination capture the temporal and spatial memory, respectively. Results show that the time‐subordination component of the FSF model captures a wide range of delayed flow response due to various degrees of soil heterogeneity (especially for low‐conductivity zones), while the model's flow‐subordination term accounts for the rapid flow responses along preferential flow paths. In the FSF model, parameters defining spatiotemporal memory functions may be related to soil properties, while other parameters such as scalar factors controlling the overall advection and diffusion are difficult to predict and can be estimated from subsurface stormflow hydrographs. These parameters can be constants at the hillslope scale because the spatiotemporal subordination, an upscaling technique, can capture the impact of system heterogeneity on flow dynamics, leading to a linear FSF model that might be applicable for various slopes. Valid scale, limitation and extension of the FSF model, and modification of the model for other complex hydrological dynamics are also discussed.

Image-based multiscale mechanical modeling shows the importance of structural heterogeneity in the human lumbar facet capsular ligament.

The lumbar facet capsular ligament (FCL) primarily consists of aligned type I collagen fibers that are mainly oriented across the joint. The aim of this study was to characterize and incorporate in-plane local fiber structure into a multiscale finite element model to predict the mechanical response of the FCL during in vitro mechanical tests, accounting for the heterogeneity in different scales. Characterization was accomplished by using entire-domain polarization-sensitive optical coherence tomography to measure the fiber structure of cadaveric lumbar FCLs ([Formula: see text]). Our imaging results showed that fibers in the lumbar FCL have a highly heterogeneous distribution and are neither isotropic nor completely aligned. The averaged fiber orientation was [Formula: see text] ([Formula: see text] in the inferior region and [Formula: see text] in the middle and superior regions), with respect to lateral-medial direction (superior-medial to inferior-lateral). These imaging data were used to construct heterogeneous structural models, which were then used to predict experimental gross force-strain behavior and the strain distribution during equibiaxial and strip biaxial tests. For equibiaxial loading, the structural model fit the experimental data well but underestimated the lateral-medial forces by [Formula: see text]16% on average. We also observed pronounced heterogeneity in the strain field, with stretch ratios for different elements along the lateral-medial axis of sample typically ranging from about 0.95 to 1.25 during a 12% strip biaxial stretch in the lateral-medial direction. This work highlights the multiscale structural and mechanical heterogeneity of the lumbar FCL, which is significant both in terms of injury prediction and microstructural constituents' (e.g., neurons) behavior.

In Vivo Multiscale and Spatially-Dependent Biomechanics Reveals Differential Strain Transfer Hierarchy in Skeletal Muscle.

Biological tissues have a complex hierarchical architecture that spans organ to subcellular scales and comprises interconnected biophysical and biochemical machinery. Mechanotransduction, gene regulation, gene protection, and structure-function relationships in tissues depend on how force and strain are modulated from macro to micro scales, and vice versa. Traditionally, computational and experimental techniques have been used in common model systems (e.g., embryos) and simple strain measures were applied. But the hierarchical transfer of mechanical parameters like strain in mammalian systems is largely unexplored in vivo. Here, we experimentally probed complex strain transfer processes in mammalian skeletal muscle tissue over multiple biological scales using complementary in vivo ultrasound and optical imaging approaches. An iterative hyperelastic warping technique quantified the spatially-dependent strain distributions in tissue, matrix, and subcellular (nuclear) structures, and revealed a surprising increase in strain magnitude and heterogeneity in active muscle as the spatial scale also increased. The multiscale strain heterogeneity indicates tight regulation of mechanical signals to the nuclei of individual cells in active muscle, and an emergent behavior appearing at larger (e.g. tissue) scales characterized by dramatically increased strain complexity.

Fracture capture of organic pores in shales

AbstractShales are heterogeneous media with porosity at many scales and in many microtextural positions, including within organic matter and clay aggregates. Because these materials have contrasting mechanical properties, it remains unclear how induced fractures manage to connect with this porosity whether during hydrocarbon production, wastewater injection, or carbon‐capture‐and‐storage efforts. To explore porosity changes related to fracturing, we experimentally failed shale samples in a triaxial load apparatus and observed changes in microstructure through scanning electron microscopy, low‐pressure nitrogen sorption, and nuclear magnetic resonance. We observed a system of microcracks, many of which were likely experimentally induced and localized on grain boundaries. In some cases these fractures propagated into regions of natural porosity in organic matter. In the subsurface this “fracture capture” likely enhances pore connectivity, but only selectively depending upon mechanical conditions. Fracture capture is one possible mechanism by which multiscale compositional heterogeneity in shales may affect rheological heterogeneity.

Reservoir characterization and multiscale heterogeneity modeling of inclined heterolithic strata for bitumen-production forecasting, McMurray Formation, Corner, Alberta, Canada

Bitumen reservoirs dominated by inclined heterolithic stratification (IHS) formed in large point bars of the Aptian (Lower Cretaceous) McMurray Formation in the northwestern part of the Corner oil sand lease (Alberta, Canada) were investigated to establish their value. Hybrid production technologies were applied to thin pay, typified by homogeneous reservoir sand units thicker than 5 m at the base overlain by IHS (so-called ‘thin pay’), as well as IHS-dominated reservoirs in which the IHS extends down to the base of the reservoir. High-resolution seismic data and well data (core, dipmeter, HMI) were used to map four facies associations, comprising a total of 16 sedimentary facies, as well as various fluid contacts to assist in reservoir characterization and risk assessment. The conceptual depositional model was based on the analysis of the migration and re-orientation history of the IHS-dominated point bars reflecting lateral accretion, downstream migration, rotation and relocation of the bars. Multiple reactivation events, which control the heterolithic nature and reservoir quality of the deposits, create developable “pools”.Seven electrofacies (with generally increasing mud content) were defined and used as input to construct vertical proportion curves that relate the electrofacies distribution to geomodel statistics in the main reservoir zone. At the electrofacies scale, numerical effective porosity-permeability models were created using micromodeling and minimodeling concepts. The geometrical shape of the electrofacies in the geomodel was investigated using non-stationary Truncated Gaussian (TG) facies simulation to enforce the stacking patterns. Each geomodel area was characterized using one variogram to efficiently compute the horizontal and vertical variogram ranges and average azimuths. Sequential Gaussian simulation (SGS) was used to map the distribution of key petrophysical parameters such as effective porosity, effective water saturation and Vshale. Empirically derived saturation versus elevation profiles for each electrofacies were included in the modeling. The distributions from the micro- and mini-modeling were introduced using probability field (P-field) simulation. To investigate the amount of connected resources (the degree of connectivity of good sand as well as IHS) were extractable flow simulation studies were performed at the pad scale. In preparation for reservoir simulation, connectivity calculations within the local pool geomodel realizations were tailored for the reservoir heterogeneities (i.e., IHS) that are expected to have a major impact on the specific thermal and gravity drainage extraction processes. The geomodel realizations were ranked by expected pseudo-dynamic behaviour with connected exploitable pay as a critical parameter.

Data-driven surrogates for rapid simulation and optimization of WAG injection in fractured carbonate reservoirs

Conventional simulation of fractured carbonate reservoirs is computationally expensive because of the multiscale heterogeneities and fracture–matrix transfer mechanisms that must be taken into account using numerical transfer functions and/or detailed models with a large number of simulation grid cells. The computational requirement increases significantly when multiple simulation runs are required for sensitivity analysis, uncertainty quantification and optimization. This can be prohibitive, especially for giant carbonate reservoirs. Yet, sensitivity analysis, uncertainty quantification and optimization are particularly important to analyse, determine and rank the impact of geological and engineering parameters on the economics and sustainability of different Enhanced Oil Recovery (EOR) techniques. We use experimental design to set up multiple simulations of a high-resolution model of a Jurassic carbonate ramp, which is an analogue for the highly prolific reservoirs of the Arab D Formation in Qatar. We consider CO 2 water-alternating-gas (WAG) injection, which is a successful EOR method for carbonate reservoirs. The simulations are employed as a basis for generating data-driven surrogate models using polynomial regression and polynomial chaos expansion. Furthermore, the surrogates are validated by comparing surrogate predictions with results from numerical simulation and estimating goodness-of-fit measures. In the current work, parameter uncertainties affecting WAG modelling in fractured carbonates are evaluated, including fracture network properties, wettability and fault transmissibility. The results enable us to adequately explore the parameter space, and to quantify and rank the interrelated effect of uncertain model parameters on CO 2 WAG efficiency. The results highlight the first-order impact of the fracture network properties and wettability on hydrocarbon recovery and CO 2 utilization during WAG injection. In addition, the surrogate models enable us to calculate quick estimates of probabilistic uncertainty and to rapidly optimize WAG injection, while achieving significant computational speed-up compared with the conventional simulation framework.

Effects of multi-scale landscape heterogeneity on soil meso- and microfaunal communities in typical regions of the lower reaches of the Yellow River

The development of intensive agriculture has caused a decline in habitat variability and loss of biodiversity in the agro-landscapes of the world. To explore the relationships between landscape heterogeneity and soil meso- and microfaunal communities in typical agricultural landscapes, we established a study area in Fengqiu County, Henan Province, which is a typical agricultural region in the lower reaches of the Yellow River. We established different buffer radii (25m, 50m, 100m, 150m, 200m, and 250m) at the plot scale, based on a multi-scale (plot, habitat, and field) approach. We combined soil faunal diversity data from 31 sampling plots in the study area. We used the landscape index of CONTAJ as a priori landscape index to determine landscape heterogeneity levels, including high, medium and low landscape heterogeneity. Moreover, at the habitat scale, we selected farmland and woodland in each plot as habitats. At the field scale, soil sampling rings and Tullgren funnels were used to obtain soil meso- and microfauna from the center and edge of the farmland and woodland habitats. In addition, the effects of scale on the diversity of soil meso- and microfauna were analyzed using a multivariable ANOVA at plot, habitat, and field scales. A total of 2300 soil faunal individuals belonging to 27 classes were identified. The dominant groups included Oribatida, Actinedida, and Formicidae. Hypogastruridae, Isotomidae, Poduridae, Diptera larvae, and Coleoptera larvae were common groups. The results indicated that different habitats and fields contained different species abundances of soil meso- and microfauna. For example, the center of farmland had the greatest species abundance of soil fauna, whereas the lowest abundance occurred in the center of the woodland. Furthermore, species diversity indices including species richness, Shannon index, and Simpson index were the highest at the edge of the farmland, but the lowest in the center of the woodland. Animal diversity in the soil indicated that, except for species richness, there were no significant differences among other diversity indices. The effects of habitat scale on the soil faunal communities were most significant among the three scales (plot, habitat, and field). Although there was no significant effect among different landscape heterogeneity levels at the plot scale, the effect of landscape heterogeneity index on the soil fauna was significant at the 25m buffer radius. We concluded that although woodlands did not maintain soil meso- and microfauna diversity in study area, this habitat has important ecological values that require further study. Compared with farmland, woodland could provide better habitats for soil meso- and microfauna in the future. Therefore, it is important to reinforce the protection of woodlands in agricultural landscapes.

The influence of multiscale heterogeneity on recrystallization in nickel processed by accumulative roll bonding

Microscopic and sample-scale heterogeneities have been characterized in nickel processed by accumulative roll bonding (ARB) to a von Mises strain of 4.8, and their influence on recrystallization have been analyzed. The microscopic deformation heterogeneities in this material are mostly associated with regions near the bonding interface, which are more refined and thus possess a higher stored energy than other regions. These regions also contain characteristic particle deformation zones around fragments of the steel wire brush used to prepare the surface for bonding. The sample-scale heterogeneities are seen as variations in the distribution of different texture components and in the fractions of high misorientation regions between the subsurface, intermediate, and central layers. Each of these heterogeneities affects the progress of recrystallization. Regions near bonding interfaces and particle deformation zones are found to act as preferential nucleation sites. Preferential nucleation is also observed at shear bands and within cube-oriented lamellae. On the sample scale, recrystallization proceeds faster in the intermediate layer than in the central and subsurface layers.

On observation of local strong heterogeneity in the Earth’s inner core below southeastern Asia

The dimensions and nature of multi-scale structural heterogeneities in the Earth’s inner core (IC) provide important constraints on its mineralogy and formation history. Teleseismic body waves with turn points close to the inner core boundary (ICB) provide a unique tool for imaging the fine structure of the upper IC. In this study, we invoke differential travel times and amplitudes of PKPBC and PKPDF waveforms observed in crossing polar and equatorial paths to provide more constraints on the heterogeneity previously located in the quasi-eastern hemisphere of the IC (Kaazik et al., 2015; Krasnoshchekov et al., 2016). A more refined analysis of quasi-polar PKPBC/PKPDF amplitude ratios measured within the heterogeneity indicates that seismic attenuation is both frequency and depth dependent, and its relatively low Q-factor at 1Hz of approximately 118 tends to grow with depth. Outside the heterogeneity, no pronounced polar-equatorial differences are observed; the estimated Q factor is about twice as large and not directionally dependent. We also analyse new differential travel times of rays that enable sampling of the anomaly at greater depths. The analysis exhibits the polar – equatorial contrasts observed in the heterogeneity terminate at approximately 520km below the ICB, which we interpret to be its bottom. The earlier interpretation of the heterogeneity in terms of strong anisotropic volume amidst the almost isotropic eastern hemisphere of the IC can be retained, and the lower bound of anisotropy strength within the anomaly is determined to be 2%.

The impact of fine-scale reservoir geometries on streamline flow patterns in submarine lobe deposits using outcrop analogues from the Karoo Basin

Improved prediction of the recovery of oil-in-place in basin-floor fan reservoirs requires accurate characterization and modelling of multiscale heterogeneities. The use of outcrop analogues is a key tool to augment this process by documenting and quantifying sedimentary architecture, hierarchy and sedimentary facies relationships. A 3D geological modelling workflow is presented that tests the impact of fine-scale heterogeneities within basin-floor lobe complexes on reservoir connectivity. Construction of geological models of a basin-floor lobe complex allows realistic depositional architecture and facies distributions to be captured. In addition, detailed models are constructed from channelized areas within a basin-floor lobe complex. Petrophysical modelling and streamline analysis are employed to test the impact on reservoir connectivity between lobe models with: (i) vertically stacked facies with coarsening- and thickening-upwards trends in all locations; and (ii) lateral facies changes with dimensions and distributions constrained from outcrop data. The findings show that differences in facies architecture and, in particular, lobe-on-lobe amalgamation have a significant impact on connectivity and macroscopic sweep efficiency, which influence the production results. Channelized lobe areas are less predictable reservoir targets owing to uncertainties associated with channel-fill heterogeneities. The use of deterministic sedimentary architecture concepts and facies relationships have proven vital in the accurate modelling of reservoir heterogeneities.