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Given the challenge of definitively discriminating between chemical and nuclear explosions using seismic methods alone, surface detection of signature noble gas radioisotopes is considered a positive identification of underground nuclear explosions (UNEs). However, the migration of signature radionuclide gases between the nuclear cavity and surface is not well understood because complex processes are involved, including the generation of complex fracture networks, reactivation of natural fractures and faults, and thermo-hydro-mechanical-chemical (THMC) coupling of radionuclide gas transport in the subsurface. In this study, we provide an experimental investigation of hydro-mechanical (HM) coupling among gas flow, stress states, rock deformation, and rock damage using a unique multi-physics triaxial direct shear rock testing system. The testing system also features redundant gas pressure and flow rate measurements, well suited for parameter uncertainty quantification. Using porous tuff and tight granite samples that are relevant to historic UNE tests, we measured the Biot effective stress coefficient, rock matrix gas permeability, and fracture gas permeability at a range of pore pressure and stress conditions. The Biot effective stress coefficient varies from 0.69 to 1 for the tuff, whose porosity averages 35.3% ± 0.7%, while this coefficient varies from 0.51 to 0.78 for the tight granite (porosity

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Tight reservoirs are the focus of unconventional oil and gas resource development, but most tight reservoirs exhibit complex pore structures, strong non-homogeneity, and limited water drive development. Fracturing fluid imbibition is a critically important way to improve the recovery of tight reservoirs. In this paper, an NMR experimental device was used to conduct imbibition experiments in tight reservoirs, and the relationship between temperature, pressure, matrix permeability, and imbibition recovery was investigated. Based on the fracturing fluid imbibition recovery curve, the imbibition process is divided into the fast imbibition stage, slow imbibition stage, and imbibition equilibrium. In addition, based on the pore structure division, the recovery changes of each pore under different experimental conditions were quantitatively analyzed. The results indicate that the highest imbibition recovery is achieved at an experimental pressure of 5 MPa within the range of 0 MPa to 15 MPa. Increasing the experimental pressure can increase the imbibition rate but will not increase imbibition recovery. Within the investigated range in this paper, fracturing fluid imbibition increases with rising temperature and matrix permeability. Moreover, the recovery of each pore gradually increases with the experimental pressure ranging from 0 MPa to 5 MPa. The recovery of each pore is positively correlated with matrix permeability and temperature. During the experiment, micropores contributed the most to the recovery, while macropores contributed the least. The study in this paper guides the efficient development of tight reservoirs. [ABSTRACT FROM AUTHOR]

The quantitative analysis of karst spring hydrographs aids in characterizing the hydrodynamic properties of aquifer systems. However, the relationships between spring hydrographs and hydrologic functions of different media lack in‐depth research. This study detected the rainfall‐discharge processes of covered karst systems using two combined discrete‐continuum models (a coupled continuum‐pipe model and a hybrid model) developed based on laboratory experiments. An improved exponential function was used to decompose spring recession hydrographs with a great performance, and the results indicate that the slow drainage controlled by the porous medium dominates the whole recession process. There is a shift in the contribution of the matrix to karst discharge systems with the increase of its hydraulic conductivity. Although spring hydrographs have a great dependency on the hydraulic process of fracture networks, the variation in permeability of the matrix significantly changes the storage capacity of fractured rocks and spring discharge behaviours. The changing process of water storage rate of the matrix and fractures with spring hydrographs reveals three stages: a period of steep rise and fall, a period with slight fluctuations, and a gentle descent stage. The parameter sensitivity analysis in both models shows that the covering porous layer has a strong effect on the patterns of karst spring hydrographs, and the specific yield is more sensitive than hydraulic conductivity. While these simulations were conducted at the laboratory scale, the findings provide insights into practical applications of spring protection and water resources management. [ABSTRACT FROM AUTHOR]

Shale fracture permeability is a key parameter to control the enrichment and high yield of shale gas, and shale matrix permeability determines the stable and economic production of shale gas. It is particularly important to study the anisotropy characteristics of shale fracture and matrix permeability to ensure the long-term production of shale gas. Taking Marine shale in southeastern Chongqing as the research object, the influencing factors of shale fracture and matrix permeability anisotropy were explored. By means of micro computed tomography (micro-CT) and high-pressure mercury injection, the characteristics of shale fractures were analyzed and the shale fractures and matrix were distinguished. The triaxial permeability of shale under formation pressure was measured using cubic samples and 3D printed polymer membrane technology. The relationship between permeability anisotropy of shale fractures and matrix and characteristics of pore structure was revealed by qualitative observation, quantitative analysis and digital core. The results show that shale matrix permeability is mainly controlled by shale microstructure, while shale fracture permeability is mainly determined by fracture morphology and characteristics. The existence of microfractures increases the difference of fracture permeability between horizontal and vertical directions, but has little effect on the ratio of horizontal fracture permeability directions or even decreases. In the horizontal direction, minerals and organic matter are arranged in layers, which are easy to form a connected pore microfracture network, and increase the matrix permeability in the parallel bedding direction of shale, making it 1 ~ 2 orders of magnitude higher than that in the vertical bedding direction. The difference of matrix permeability in horizontal direction is enhanced by sandy bands and laminaries. Morever, the matrix permeability in the three directions of shale has a positive correlation with the pore specific surface area, pore volume and average pore size, and the more developed micropores and mesoporous pores are, the higher matrix permeability of shale is. The research results are of great significance to further understand the theoretical issues of shale heterogeneity and its influence. The research results can provide a reference for shale gas exploration and development and provide a basis for economic exploitation of shale g [ABSTRACT FROM AUTHOR]

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IntroductionPlants confined to island-like habitats are hypothesised to possess a suite of functional traits that promote on-spot persistence and recruitment, but this may come at the cost of broad-based colonising potential. Ecological functions that define this island syndrome are expected to generate a characteristic genetic signature. Here we examine genetic structuring in the orchid Phalaenopsis pulcherrima, a specialist lithophyte of tropical Asian inselbergs, both at the scale of individual outcrops and across much of its range in Indochina and on Hainan Island, to infer patterns of gene flow in the context of an exploration of island syndrome traits.MethodsWe sampled 323 individuals occurring in 20 populations on 15 widely scattered inselbergs, and quantified genetic diversity, isolation-by-distance and genetic structuring using 14 microsatellite markers. To incorporate a temporal dimension, we inferred historical demography and estimated direction of gene flow using Bayesian approaches.ResultsWe uncovered high genotypic diversity, high heterozygosity and low rates of inbreeding, as well as strong evidence for the occurrence of two genetic clusters, one comprising the populations of Hainan Island and the other those of mainland Indochina. Connectivity was greater within, rather than between the two clusters, with the former unequivocally supported as ancestral.DiscussionDespite a strong capacity for on-spot persistence conferred by clonality, incomplete self-sterility and an ability to utilize multiple magnet species for pollination, our data reveal that P. pulcherrima also possesses traits that promote landscape-scale gene flow, including deceptive pollination and wind-borne seed dispersal, generating an ecological profile that neither fully conforms to, nor fully contradicts, a putative island syndrome. A terrestrial matrix is shown to be significantly more permeable than open water, with the direction of historic gene flow indicating that island populations can serve as refugia for postglacial colonisation of continental landmasses by effective dispersers.

Context: Habitat loss is a major factor influencing declines in landscape connectivity for many species, but forest patch configuration and changes in matrix permeability can also represent important drivers. An evaluation of which of these factors are predominant is key to guiding landscape planning at a regional scale. Objectives: We aimed to quantify the loss of jaguar (Panthera onca) habitat connectivity and to analyse the drivers behind this process in the Atlantic Forest. Methods: We analysed trends in jaguar habitat connectivity between 1973 and 2015 in the Upper Paraná Atlantic Forest and the three countries that comprise the eco-region (Argentina, Brazil, and Paraguay). We used graph-based indices and jaguar movement data to evaluate changes in forest area, forest patch configuration and matrix permeability. Results: Jaguar habitat connectivity decreased throughout the entire period, with a loss of up to 93% of connectivity. Changes in forest patch configuration and forest area loss were the main drivers of this trend, but the effect of decreased matrix permeability was also significant. These processes together largely increased the negative effect of forest area declines on jaguar habitat connectivity. Connectivity trends for the three countries in the study area were negative, with the highest forest decline in Paraguay and Brazil compared to Argentina. Conclusions: Analysing landscape dynamics using metrics that go beyond measuring net forest area is key when assessing landscape connectivity for jaguars. Future studies evaluating landscape connectivity should incorporate habitat patch configuration and matrix permeability in addition to forest loss, aspects that should also be considered when undertaking habitat restoration measures. [ABSTRACT FROM AUTHOR]

Copyright of Grundwasser is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Shale matrix permeability is an important indicator for evaluating gas transport and production. However, the effects of pore connectivity and water saturation on the matrix permeability in deep gas shales have not been adequately studied. In this study, the permeability of deep shales in the Yichang area of the Middle Yangtze was characterized using three methods. These included the determination of apparent permeability in different directions via pulse-decay, also matrix permeability obtained via the Gas Research Institute method, and the connected pore network permeability via the mercury injection capillary pressure technique. The results revealed a significant difference between the horizontal and vertical permeability of deep shales. The smaller the size of the multiple connected pore network, the larger was the effective tortuosity and the lower the permeability. Comparison of the three permeabilities and combined microscopic observations revealed that microfractures and laminae were the dominant gas transport channels. Importantly, the matrix permeability decreased exponentially with increasing water saturation, with water vapor adsorption experiments revealing that water occupation of pores and porethroat spaces smaller than 10 nm in diameter was the main reason for this decrease in matrix permeability. Collectively, proposed method of evaluating effective permeability with an index for shale gas reservoirs is significant for sweet spot selection and production prediction of shale gas reservoirs around the globe. [ABSTRACT FROM AUTHOR]

The relevance of the discussedissue is caused by the fact that the oil fields of the Perm region are determined by the widespread occurrence of fractures in carbonate reservoirs and the influence of fractured rocks on oil filtration in the reservoir. The paper considers the effect of changes in the stressed state of rocks (effective pressure) on the porosity and permeability of core samples in various lithologic-facies zones of Tourne-Famennian carbonate sediments. The Tourne-Famennian carbonate deposits of the Upper Kama Region fields are characterized by a complex geological structure. On these deposits the lithological-facial zones are distinguished with different filtration-capacitive properties due to the geological conditions of sedimentation. The main aim of the study is to assess the dynamics of the fracture and matrix permeability of core samples of carbonate objects depending on the change in effective pressure. Object: Tourne-Famennian carbonate reservoirs of the Gagarinsky and Ozernoe fields. Methods: filter systems with simulation of reservoir conditions UIG-5VG and AFS-300 and installation of microfocus X-ray. Results. A series of experiments analyzed in this work allowed establishing that in carbonate Tourne-Famennian collectors (permeability up to 350 mD), characterized by fracturing, while reducing the load, the permeability of the collector is not fully restored. Accordingly, in the areas of development of fractured reservoirs from the very beginning of the operation of the wells, it is preferable to limit the reduction of their bottomhole pressure. It was also established that in Tourne-Famennian deposits of the Upper Kama Region for various types of seismic waves there is a physical velocity limit associated with the structure of the pore space. At the same time, in perspective, it is possible to isolate the densest parts of the deposits in terms of the wave velocity, which, in their turn, are subject to formation of cracks. The task should be solved on the basis of integrated accounting of core research data, hydrodynamic studies of wells, 3D seismic exploration and analysis of well operation.

Previously, hydrogeologists and petroleum engineers use seepage experiments to measure permeability. This paper develops a novel method to calculate matrix permeability from velocity and attenuation of an ultrasonic S-wave. At first, permeability is derived as a function of frequency when an S-wave scans a fluid-saturated rock. Substituting the permeability into a previous S-wave model gives theoretical velocity and attenuation, in which the nexus parameter is the average distance of aperture representing pores. Fitting the predicted velocity and quality factor against the measured counterparts yields permeability in the full frequency range. For Berea sandstone, the inverted permeability at low frequency (0.0376 Darcy) is comparable to Darcy permeability (0.075 Darcy), confirming that Berea sandstone is homogenous. For Boise sandstone, the inverted permeability at low frequency is 0.0457 Darcy, much lower than Darcy permeability (1 Darcy). When S-wave scans the rocks, its velocity and attenuation are dominated by matrix pore throats and the inverted permeability represents matrix permeability. Unlike Berea sandstone, Boise sandstone has fractures and widely distributed grain diameters. The fractures and the large pores (due to large grain diameter) are preferential pathways that increase Darcy permeability far more than matrix permeability. [ABSTRACT FROM AUTHOR]

The demand for a clean energy source from shale is growing day-to-day since it is not harmful to the environment like other fossil fuels. Further, shale reservoirs offer long-term geo-carbon dioxide (CO 2) storage. Innovations in horizontal drilling and multi-stage hydraulic fracturing have made shale gas extraction and geo-CO 2 storage economically viable. A three-dimensional Yanchang shale formation simulation model in Ordos's basin was developed using CMG-GEM, considering adsorption/desorption, diffusion, geomechanics, permeability changes, and non-Darcy flow. Two horizontally drilled wells, each 510 m long, were fractured and positioned 90 m apart. CO 2 gas was injected into Well-2, producing methane (CH 4) in Well-1. After simulation for 30 years, the cumulative mass of CH 4 produced was 1.07×10+5kg, the cumulative mass of CO 2 produced was 2.3×10+4kg, which is 1.14% of the mass injected, the cumulative mass of CO 2 injected was 2.01×10+6kg and cumulative mass of CO 2 gas stored was 1.987×10+6kg which is 98.86% of the injected mass of CO 2 gas. The natural fracture system was the dominant factor of enhanced shale gas recovery and CO 2 injection in the Yanchang shale formation. A sensitivity analysis was conducted with CMG-CMOST, examining the influence of reservoir and hydraulic fracture parameters in the storage of CO 2 and enhancing CH 4 recovery. Natural fracture porosity had the most significant impact on CH 4 production and CO 2 storage, followed by fracture permeability and half-length leading for hydraulic fracture parameters, with fracture conductivity being the least influential parameter. The approach used in this study applies to tight shale oil and gas formations in various sedimentary basins worldwide, enabling a more comprehensive understanding of reservoirs and hydraulic fracture parameters that can enhance oil and natural gas production. [Display omitted] • A multi-component adsorption model for assessing geo-CO 2 storage and CH 4 recovery was developed via CMG-GEM. • The model incorporates molecular diffusion, pressure-dependent permeability, non-darcy flow and geo mechanics comportments. • Petrophysical parameters and experimental fluid properties data assessed the efficiency of CO 2 storage and CH 4 recovery. • The model creates a better complex network for desorption of CH 4 and the adsorption of CO 2 , reducing air pollution. • The study offers an improved solution for the energy sector. [ABSTRACT FROM AUTHOR]

Abstract Shale cuttings and cores recovered from the subsurface and stored for hours to decades tend to dry out and lose moisture and hydrocarbons, leading to an increase in the effective matrix permeability. Moisture loss in shale samples is a fundamental sample preservation problem which can be solved by applying a standard moisture equilibration procedure to restore lost moisture. Our aim was to investigate the relationship between permeability and variable moisture as-received, as-received moisture-equilibrated and saturated moisture-equilibrated samples. Samples were crushed to a series of particle sizes (0.6-2.0) mm and moisture equilibrated at 97% relative humidity. Results show that moisture equilibration in the samples was achieved after 72 h. The permeability of the saturated moisture-equilibrated and as-received moisture-equilibrated samples decreased exponentially with increase in moisture content. The high correlation coefficient between permeability and particle size (r = 0.96 and 0.97) for moisture-equilibrated samples compared to 0.76 for as-received samples indicates that moisture equilibration improves permeability measurements in crushed shale samples. Furthermore, permeability measurements are repeatable for moisture-equilibrated samples compared to samples that were not equilibrated (as-received). We conclude that moisture content affects permeability and moisture equilibration normalizes and improves the repeatability of permeability measurements in crushed shale.

The traditional steady-state method and transient method are unable to measure the permeability in the matrix micropores of low-permeability coal seam, particle coal cannot be used as the object of measuring the matrix permeability under the loading condition, and the conventional theoretical model to describe the gas flow characteristics is unreasonable in the matrix pores of low-permeability coal seam under the loading condition. In order to solve above problems,the unidirectional apparent diffusion model of gas was established, and the analytical solution of the model was derived. Then, according to the principle of mass conservation, the relationship between permeability and diffusion coefficient was derived. An experimental method (apparent diffusion coefficient permeability) and a unidirectional apparent diffusion coefficient-permeability model were established to describe the permeability in the matrix micropores of low-permeability coal seams. In order to verify the rationality of the model, the unidirectional desorption flow experiment of gas under triaxial stress was carried out with a standard cylindrical coal core of Φ50 mm × 100 mm. At the same time, the comparative experiment of radial desorption flow of the same kind of columnar coal was performed. Under the same conditions, the steady-state permeability experiment was conducted. The experimental results of unidirectional desorption flow show that the apparent diffusion coefficient-permeability has a negative exponential relationship with the increase of confining pressure. The analysis indicates that the increase of confining pressure leads to the closure of pores and fractures, which makes the pore radius decrease. Therefore, the pore size and structure directly affect the apparent diffusion coefficient permeability, which results in the decrease of apparent diffusion coefficient permeability. Secondly, through the contrast testing, it was found that the desorption flow amount and desorption flow ratio are far less than those of the unidirectional desorption flow without loading, which indicates that the confining pressure has a great influence on the desorption flow characteristics of gas in coal seam, and the confining pressure conditions should be considered when we study the factors affecting the desorption flow characteristics of gas in coal seam. Under the same conditions, the permeability measured by the new method is at least two orders of magnitude lower than that measured by the steady-state method. Therefore, it is necessary to develop new permeability measurement methods. The verification shows that the unidirectional apparent diffusion coefficient-permeability model can effectively describe the flow characteristics of gas in the matrix pores of coal seams under loading conditions. As a result, the model was able to effectively provide theoretical guidance for measuring the matrix permeability of gas in matrix pores and describing the flow characteristics of gas in matrix pores well. [ABSTRACT FROM AUTHOR]

There are several factors that can determine the pattern of habitat use by species in fragmented habitats. Here we investigated the applicability of the continuum model, which predicts that habitat use varies in a continuous way and not categorically like habitat and not-habitat, for small mammal habitat use. We also investigated if habitat-related guilds of species can change their habitual pattern of habitat use in an extremely altered landscape. This study was conducted in a highly fragmented area of Atlantic Forest in Brazil, where forest fragments are immersed in a pasture matrix. We captured mammals using pitfall traps placed in six sampling sites. In each of these sites, we selected four of five different habitats that were available in the local landscape: high-elevation forests without stream, low-elevation forests with stream, forest edges, pasture matrix without stream, and pasture matrix with stream. This study revealed that the theory of the continuum model can be applied for investigating patterns of use of fragmented forests by small mammals. We also observed, in general, low tolerance of forest species to the most disturbed habitat, the pasture matrix without stream. However, a small increase in the complexity of the vegetation, as observed in riparian pasture matrices, seems to mitigate this negative effect, making the abundance, richness, and diversity of small mammals comparable to forest habitats. These results indicate that the presence of streams may facilitate the use of the pasture matrix, contributing for the maintenance of the original community in the fragmented forest. [ABSTRACT FROM AUTHOR]

Animal movement through agricultural landscapes is critical for population persistence of species within fragmented native vegetation patches. However, perceived habitat quality and the structural changes between differing land uses within such landscapes can reduce an animal's willingness to move. Understanding when animal movement behaviour varies in response to differing habitat types is necessary for identifying barriers to movement between habitat patches. We quantified the homing success and fine‐scale movement behaviour of a patch‐dependent gecko, Gehyra versicolor, in remnant patches, three different matrix types (crop, pasture and linear plantings), and at varying distances from the edge using fluorescent powder tracking, radio‐telemetry and experimental displacement. We found displaced geckos in pasture environments orientated more strongly and moved farther into farmland after being released and, away from their home ranges in remnant patches. In contrast, we found strong homing ability of displaced animals in plantings and crop matrix types, with animals moving towards remnant patches and away from farmland. Importantly, from the 48 individuals radio‐tracked, none moved into farmland, including pastures, despite 16 individuals approaching edge habitat. Because radio‐tracked geckos did not move into pastures, or any other matrix type, movement further into pasture by displaced animals likely represents limited orientation capacity in pasture rather than preference for pasture. We conclude geckos behaviourally avoided the farmland, irrespective of the presence of complex habitat (e.g. linear plantings). Our findings suggest that, despite efforts to improve farmland quality by planting, farmland is not generally preferred compared to remnant native vegetation. Understanding habitat‐specific movement behaviour is crucial to effectively identifying barriers to animal movement and will improve our efforts to conserve regional populations of patch‐dependent species. [ABSTRACT FROM AUTHOR]

The hydraulic properties of reservoir matrix and fractures, as well as the production performance of enhanced geothermal systems, can be significantly affected by chemical dissolution and precipitation. Therefore, chemical reaction effects must be considered when exploiting dry hot rock resources. To investigate the impact of chemical effects, this study incorporates the dissolution/precipitation process of silica in the reservoir matrix and fractures and establishes a thermo-hydro-chemical coupling dual-well model that includes a main fracture and multiple secondary fractures. Results indicate that under-saturation injections increase the mechanical aperture of the main fracture by up to 0.066 mm and permeability by up to 217.3 % over a 30-year production period. Oversaturation injections decrease the mechanical aperture by up to 0.035 mm and permeability by up to 66.1 %. Reservoir matrix permeability exhibits a noticeable zonal distribution, with a maximum increase of 22.6 % in the under-saturation injection and a maximum decrease of 4.1 % in the saturation injection over a 30-year production period. Chemical reactions have a significant impact on the average production pressure. Neglecting chemical reactions in the matrix may result in overestimation or underestimation of changes in production pressure. These results provide a reference for the sustainable production of EGS in the long term. • A thermo-hydro-chemical (THC) coupled model is established for the development of enhanced geothermal system. • THC coupled process is simulated in a double well production model with a primary fracture and multiple secondary fractures. • The permeability evolution of both reservoir matrix and fractures affected by silica dissolution/precipitation is analyzed. • The impact of chemical effects on geothermal recovery efficiency is predicted. [ABSTRACT FROM AUTHOR]

The bulk of the world’s biodiversity is found in tropical regions, which are increasingly threatened by the human-led degradation of natural habitats. Yet, little is known about tropical biodiversity responses to habitat loss and fragmentation. Here we review all available literature assessing landscape effects on gene flow in tropical species, aiming to help unravel the factors underpinning functional connectivity in the tropics. We map and classify studies by focus species, the molecular markers employed, statistical approaches to assess landscape effects on gene flow, and the evaluated landscape and environmental variables. We then compare qualitatively and quantitatively landscape effects on gene flow across species and units of analysis. We found 69 articles assessing landscape effects on gene flow in tropical organisms, most of which were published in the last five years, were concentrated in the Americas, and focused on amphibians or mammals. Most studies employed population-level approaches, microsatellites were the preferred type of markers, and Mantel and partial Mantel tests the most common statistical approaches used. While elevation, land cover and forest cover were the most common gene flow predictors assessed, habitat suitability was found to be a common predictor of gene flow. A third of all surveyed studies explicitly assessed the effect of habitat degradation, but only 14 of these detected a reduced gene flow with increasing habitat loss. Elevation was responsible for most significant microsatellite-based isolation by resistance effects and a single study reported significant isolation by non-forested areas in an ant. Our study reveals important knowledge gaps on the study of landscape effects on gene flow in tropical organisms, and provides useful guidelines on how to fill them.

Shale cuttings and cores recovered from the subsurface and stored for hours to decades tend to dry out and lose moisture and hydrocarbons, leading to an increase in the effective matrix permeability. Moisture loss in shale samples is a fundamental sample preservation problem which can be solved by applying a standard moisture equilibration procedure to restore lost moisture. Our aim was to investigate the relationship between permeability and variable moisture as-received, as-received moisture-equilibrated and saturated moisture-equilibrated samples. Samples were crushed to a series of particle sizes (0.6-2.0) mm and moisture equilibrated at 97% relative humidity. Results show that moisture equilibration in the samples was achieved after 72 h. The permeability of the saturated moisture-equilibrated and as-received moisture-equilibrated samples decreased exponentially with increase in moisture content. The high correlation coefficient between permeability and particle size (r = 0.96 and 0.97) for moisture-equilibrated samples compared to 0.76 for as-received samples indicates that moisture equilibration improves permeability measurements in crushed shale samples. Furthermore, permeability measurements are repeatable for moisture-equilibrated samples compared to samples that were not equilibrated (as-received). We conclude that moisture content affects permeability and moisture equilibration normalizes and improves the repeatability of permeability measurements in crushed shale. [ABSTRACT FROM AUTHOR]

ABSTRACT The bulk of the world's biodiversity is found in tropical regions, which are increasingly threatened by the human-led degradation of natural habitats. Yet, little is known about tropical biodiversity responses to habitat loss and fragmentation. Here we review all available literature assessing landscape effects on gene flow in tropical species, aiming to help unravel the factors underpinning functional connectivity in the tropics. We map and classify studies by focus species, the molecular markers employed, statistical approaches to assess landscape effects on gene flow, and the evaluated landscape and environmental variables. We then compare qualitatively and quantitatively landscape effects on gene flow across species and units of analysis. We found 69 articles assessing landscape effects on gene flow in tropical organisms, most of which were published in the last five years, were concentrated in the Americas, and focused on amphibians or mammals. Most studies employed population-level approaches, microsatellites were the preferred type of markers, and Mantel and partial Mantel tests the most common statistical approaches used. While elevation, land cover and forest cover were the most common gene flow predictors assessed, habitat suitability was found to be a common predictor of gene flow. A third of all surveyed studies explicitly assessed the effect of habitat degradation, but only 14 of these detected a reduced gene flow with increasing habitat loss. Elevation was responsible for most significant microsatellitebased isolation by resistance effects and a single study reported significant isolation by non-forested areas in an ant. Our study reveals important knowledge gaps on the study of landscape effects on gene flow in tropical organisms, and provides useful guidelines on how to fill them. [ABSTRACT FROM AUTHOR]

Background Inter-patch movements may lead to genetic mixing, decreasing both inbreeding and population extinction risks, and is hence a crucial aspect of amphibian meta-population dynamics. Traveling through heterogeneous landscapes might be particularly risky for amphibians. Understanding how these species perceive their environment and how they move in heterogeneous habitats is an essential step in explaining metapopulation dynamics and can be important for predicting species’ responses to climate change and for conservation policy and management. Methods Using an experimental approach, the present study focused on the movement behavior (crossing speed and number of stops) on different substrates mimicking landscape components (human-made and natural substrates) in two amphibian species contrasting in locomotion mode: the common toad (Bufo bufo), a hopping and burrowing anuran and the marbled newt (Triturus marmoratus), a walking salamander. We tested the hypothesis that species reaction to substrate is dependent on specific ecological requirements or locomotion modes because of morphological and behavioral differences. Results In both species, substrate type influenced individual crossing speed, with individuals moving faster on soil than on concrete substrate. We also demonstrated that long-legged individuals moved faster than individuals with short legs. In both species, the number of stops was higher in females than in males. In common toads, the number of stops did not vary between substrates tested, whereas in marbled newts the number of stops was higher on concrete than on soil substrate. Discussion We highlighted that concrete substrate (mimicking roads) negatively affect the crossing speed of both studied species, with an effect potentially higher in marbled newts. Our findings corroborate negative effects of such heterogeneous landscapes on movement behavior of two amphibian species, which may have implications for the dynamics of metapopulations.

Background: Inter-patch movements may lead to genetic mixing, decreasing both inbreeding and population extinction risks, and is hence a crucial aspect of amphibian meta-population dynamics. Traveling through heterogeneous landscapes might be particularly risky for amphibians. Understanding how these species perceive their environment and how they move in heterogeneous habitats is an essential step in explaining metapopulation dynamics and can be important for predicting species' responses to climate change and for conservation policy and management. Methods: Using an experimental approach, the present study focused on the movement behavior (crossing speed and number of stops) on different substrates mimicking landscape components (human-made and natural substrates) in two amphibian species contrasting in locomotion mode: the common toad (Bufo bufo), a hopping and burrowing anuran and the marbled newt (Triturus marmoratus), a walking salamander. We tested the hypothesis that species reaction to substrate is dependent on specific ecological requirements or locomotion modes because of morphological and behavioral differences. Results: In both species, substrate type influenced individual crossing speed, with individuals moving faster on soil than on concrete substrate. We also demonstrated that long-legged individuals moved faster than individuals with short legs. In both species, the number of stops was higher in females than in males. In common toads, the number of stops did not vary between substrates tested, whereas in marbled newts the number of stops was higher on concrete than on soil substrate. Discussion: We highlighted that concrete substrate (mimicking roads) negatively affect the crossing speed of both studied species, with an effect potentially higher in marbled newts. Our findings corroborate negative effects of such heterogeneous landscapes on movement behavior of two amphibian species, which may have implications for the dynamics of metapopulations. [ABSTRACT FROM AUTHOR]

Context: The umbrella approach applied to landscape connectivity is based on the principle that the conservation or restoration of the dispersal habitats for some species also can facilitate the movement of others. Species traits alone do not seem to be enough to identify good connectivity umbrella species, showing the need to investigate the influence of additional factors on this property.Objectives: We test whether the potential of a species as a connectivity umbrella can be influenced by landscape composition and configuration.Methods: We simulated movement routes for eight hypothetical species in artificial patchy landscapes with different levels of fragmentation, habitat amount and matrix permeability. We determined the effectiveness of the connectivity umbrella of the virtual species using pairwise intersections of important habitats for their movements in all landscapes.Results: The connectivity umbrella performance of all species was affected by the interaction of fragmentation level and habitat amount. In general, species performance increased with decreasing fragmentation and increasing habitat amount. In most landscapes and considering the same dispersal threshold, species able to move more easily through the matrix showed higher umbrella performance than those for which the matrix offered greater resistance.Conclusions: The connectivity umbrella is not a static feature that depends only on the species traits, but rather a dynamic property that also varies according to the landscape attributes. Therefore, we do not recommend spatial transferability of the connectivity umbrella species identified in a landscape to others that have divergent levels of fragmentation and habitat quantity. [ABSTRACT FROM AUTHOR]

Pulse-decay permeability (PDP) measurement is a widely used technique to measure the permeability of tight rocks such as shales. However, the PDP measurement is so sensitive to gas leakage of the system that the leakage would significantly affect the experimental results. To address the impact of the gas leakage, this paper develops an analytical solution of the PDP measurement with gas leakage that applies to both fractured and un-fractured core samples. The PDP measurement on a fractured core sample can be treated as a two-stage pressure transient process that are dominated by gas flow in a fracture and the flow between the fracture and the matrix, respectively. The analytical solution shows that the linearity of curve of logarithm of the normalized pressure difference (between the upstream and downstream reservoirs in the PDP system) versus time in the first-stage would break up when gas leakage occurs, so does the linearity of logarithm of the pressure decline curve in the second-stage. For an un-fractured core sample, the analytical solution for the PDP measurement with gas leakage is similar to the first-stage process for a fractured core sample. Based on these observations, an effective method to detect and correct the impacts of leakage on the PDP measurements is proposed using the analytical solution. The practical usefulness of the method is demonstrated by its successful applications to simulated PDP permeability measurements for several core samples. [ABSTRACT FROM AUTHOR]

Matrix permeability is a key factor in determining long term gas production from shale reservoirs – requiring that it is determined under true reservoir conditions. We suggest a variable pressure gradient (VPG) protocol to measure shale matrix permeability using real reservoir fluids in powdered samples. The VPG method is described and a mathematical protocol for its analysis is developed. The first measures gas fractional production rate history under constant external pressure for each production stage and with a designated pressure gradient. The second establishes the mathematical protocol for analysis using pseudo-pressure to accommodate both the effect of gas pressure-dependent PVT parameters and desorption rate coefficient. The matrix permeability is determined by matching the solution of the model with the experimental data. The model fits the experimental data well when the fractional production is <0.75. Shale matrix permeability is calculated in the order of magnitude of 10 −7 –10 −6 md. Methane permeability decreases with a decrease in both average pore pressure and particle size of the individual component grains. Permeability considerably more sensitive to changes in desorption rate coefficient than flow regimes. Compared with current small pressure gradient (SPG) methods, the VPG method is considerably more applicable to actual gas production and reduces to the SPG method under simplified boundary conditions. Although some approximate treatments are used for establishing the VPG method and some flow mechanisms are not considered, this study still provides an information-rich technique to determine shale matrix permeability at conditions close to reality. [ABSTRACT FROM AUTHOR]

Abstract: Shear‐dilation‐based hydraulic stimulations can enable commercial exploitation of geothermal energy from reservoirs with inadequate initial permeability. While contributing to enhancing the reservoir's permeability, hydraulic stimulation processes may also lead to undesired seismic activity. Here we present a three‐dimensional numerical model aiming to aid increased understanding of shear‐dilation based hydraulic stimulation and its consequences. The fractured reservoir is modeled as a network of explicitly represented large‐scale fractures immersed in a permeable rock matrix. The numerical formulation is constructed by coupling three physical processes: fluid flow, fracture deformation, and rock matrix deformation. For flow simulations, the discrete fracture‐matrix model is used, which allows fluid transport from high‐permeable conductive fractures to rock matrix and vice versa. The mechanical behavior of the fractures is modeled with reversible and irreversible deformations corresponding to elastic deformation and slip. Linear elasticity is assumed for mechanical deformation and stress alteration of the rock matrix. Fractures are modeled as lower‐dimensional surfaces embodied in the domain, subjected to specific governing equations for their deformation along the tangential and normal directions. Both the fluid flow and momentum balance equations are approximated by finite volume discretizations. The new numerical model is demonstrated considering a three‐dimensional fractured formation with a network of 20 explicitly represented fractures. The effects of fluid exchange between fractures and rock matrix on the permeability evolution and the generated seismicity are examined for test cases resembling realistic reservoir conditions. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the impact of elevated temperature exposure in tissue banking on soft tissues. A secondary objective was to determine the relative ability of various assays to detect changes in soft tissues due to temperature deviations. Porcine pulmonary heart valve leaflets exposed to 37 °C were compared with those incubated at 52 and 67 °C for 10, 30 and 100 min. The analytical methods consisted of (1) viability assessment using the resazurin assay, (2) collagen content using the Sircol assay, and (3) permeability assessment using an electrical conductivity assay. Additionally, histology and two photon microscopy were used to reveal mechanisms of cell and tissue damage. Viability, collagen content, and permeability all decreased following heat treatment. In terms of statistical significance with respect to treatment temperature, cell viability was most affected (p < 0.0001), followed by permeability (p < 0.0001), and then collagen content (p = 0.13). After heat treatment, histology indicated increased apoptosis and two photon microscopy revealed a decrease in collagen fiber organization and an increase in elastin density. These results suggest that measures of cell viability would be best for assessing tissues where the cells are alive and that permeability may be best where cell viability is not intentionally maintained. [ABSTRACT FROM AUTHOR]

The pressure decay (or gas expansion) test with crushed samples has been used to evaluate the matrix permeability of shale and other low-permeability rock for many years. However, there still exist uncertainties relating to particle size and equilibrium pressure. The existing late-stage curve fitting method has the advantage of easy calculation, but the assumption that gas enters particles with a single permeability value is not generally applicable for shale samples, and late-stage analysis may lead to underestimation. This study proposes an optimization method to determine the equivalent bulk permeability that ensures the smallest sum of squares of errors between the forward-predicted pressure decay curve and the measure one. Both the optimization and curve fitting method are applied to two shale samples from the Ordovician Wufeng Formation of two wells in the Sichuan Basin, China with improved apparatus and testing procedures. The optimization method is superior to the curve fitting method in the repeatability and regularity on the change of apparent permeability with pressure. A strong linear relationship between apparent permeability and coefficient of compressibility is established between 3 and 12 bars. The variation of permeability with particle size is more diverse than that is commonly understood and might be nonmonotonic, depending on the change of pore structure during crushing. Change of apparent permeability with pressure (non-Darcy feature) is proposed as a criterion of whether pore structure has changed significantly. It is suggested to measure the variation of permeability with pressure and particle size to obtain a more comprehensive understanding of matrix permeability and pore structure. • An optimization method that ensures the smallest sum of squared errors is proposed. • The optimization method shows a better repeatability and more obvious regularities. • A linear relationship between permeability and compressibility is established. • Non-Darcy feature is proposed as a criterion of whether pore structure change. • Permeability might vary with particle size non-monotonically. [ABSTRACT FROM AUTHOR]

Maintaining connectivity is one of the main challenges for biodiversity conservation world-wide. Ecological corridors are important to maintain landscape connectivity, but their efficiency depends on landscape patterns and species responses at different spatial extents and landscape contexts., We developed a new ecologically oriented free software package, LandScape Corridors ( lscorridors), to improve ecological corridor design by considering biodiversity responses to landscape attributes at a variety of spatial extents. LandScape Corridors considers stochastic variation, species perception and landscape influence on organisms in the design of ecological corridors. In addition to the least cost path algorithm, we propose four different methods for the simulation of multiple-path functional ecological corridors. One method uses the information for each pixel separately, whereas the three other methods permit corridor simulation considering the landscape context at different spatial extents., LandScape Corridors permits to simulate corridors for species with different requirements and considers that different species perceive and respond to the surrounding landscape in different ways, as many species may choose to move through areas that may not be the most permeable ones in the landscape. Two parameters in lscorridors modulate the stochasticity in corridors simulations. The first parameter is the level of variability added to the input resistance map in each simulation, resulting in more variable and spatially spread-out corridors. The other parameter is the spatial extent that may influence each pixel; larger extents result in larger spatial zones affecting each pixel during corridors simulations. In addition, when considering spatial influence, the simulations may be performed for species highly, medially or less sensitive to habitat quality., Some currently available software are not free or depend on a paid GIS software to work. In addition, some software do not support large matrices in their simulations, limiting their use. LandScape Corridors is designed to deal with large rasters, is based on strictly freeware software, and is freely available online. This allows the users to implement new methods for modelling multi-scale and ecologically based corridors., LandScape Corridors is a potential tool for the identification of protected areas, as corridor simulation considers species movement and landscape connectivity, essential characteristics to aid in large-scale biodiversity conservation, especially in anthropogenic landscapes. LandScape Corridors provides what we may call a zone for conservation, showing a set of connected areas in the landscape which may be ordered according to their potential for ecological corridors or which may be used as an aid for conservation strategies or ecological restoration projects. [ABSTRACT FROM AUTHOR]

Measurement of matrix permeability is essential for predicting, evaluating, and modeling the performance of shale reservoirs. However, the repeatability and accuracy of these measurements can be questioned because procedures have not been standardized. As a result, permeability measurements from the same sample by different laboratories can vary by orders of magnitude. Microfracturing related to changes in stress during core retrieval and crushing during sample preparation is thought to be a significant source of error. Different interpretations of pressure decay curves could also account for inconsistent permeability values. The goals of this research were to analyze relationships among crushed particle size, microfractures, and matrix permeability, as well as to evaluate the ways in which pressure decay curves are interpreted and to determine the sample mass best suited for analysis. Crushed rock pressure-decay measurements of particles of different sizes were obtained using a shale matrix permeameter, and permeability was estimated by curve fitting using Core Laboratories software and by other methods that assess the geometry and evolution of pressure decay curves. Results indicate that the relationships between permeability and particle size vary considerably when determined by different methods. Analysis of pressure decay curves reveals three distinct segments. The early segment is characterized by hyperbolic decay, whereas the late segment is characterized by exponential decay. A third segment records a pseudo-steady state where pressure has declined to the extent that decay can no longer be characterized. Decay was measured for about 2000 s; most decay curves stabilize within 500 s, and data collected beyond 500 s are dominated by noise associated with the pseudo-steady state and are beyond the resolution of the apparatus used. Analysis of early hyperbolic curves yields permeability values one to two orders of magnitude greater than whole curve analysis. The hyperbolic pressure decay segment appears to be influenced by microfractures and other large pores near the surface of samples, whereas the late time segment and whole curve correlate more strongly with the microporous to nanoporous rock matrix. Also, permeability values derived from whole curve analysis are sensitive to measurement duration, and different values are obtained when permeability is determined from different time windows. SEM images of all particle sizes analyzed reveal microfractures with diameters ranging from 60 to 1020 nm, but no correlation was found between microfracture aperture and particle size. The optimal sample mass used in our shale permeameter is 50–100 g, which facilitates resolution of the major elements of the decay curve. Optimal particle sizes are between 1.0 and 1.4 mm. [ABSTRACT FROM AUTHOR]

The fragmentation of natural habitats is a major threat for biodiversity. However, the impact and spatial scale of natural isolation mechanisms leading to species loss, compared to anthropogenic fragmentation, are not clear, mainly due to differences between fragments and islands, such as matrix permeability. We studied a 500 km2 Mediterranean region in France, including urban habitat fragments, continuous habitat, and continental-shelf islands. On the basis of 295 floristic relevés, we built species-area relationships to compare isolation in fragments after urbanization, with continuous habitat and continental-shelf islands. We assumed either no dispersal, infinite dispersal, or estimated intermediate levels of habitat reachability through graph theory. Isolation mechanisms occurred in fragments but with a lower strength than in near-shore islands, and most importantly affected perennial plants. Annual plants were less affected, probably due to their smaller size and shorter life cycle. Isolation occurred at landscape level in fragments and at patch level in islands. The amount of reachable habitat (accounting for spatial configuration) explained local species richness in both systems, but the amount of habitat (no consideration of spatial configuration) was already a good predictor. These results suggest an important role of habitat amount around fragments in mitigating the isolation effects observed in near-shore islands, and the importance of carefully considering different functional groups. [ABSTRACT FROM AUTHOR]

Conserving global biodiversity requires careful management of production landscapes, especially in this era of rapid environmental change. The habitat filtering framework has been used for predicting species responses to land-use changes. Habitat filters are essentially features that may slow, or limit, species use of certain habitats. We wanted to determine if this framework could identify habitat and landscape filters that predicted bat use of restored forest at the species-specific and trait group levels. We surveyed bat activity, vegetation structure, and landscape characteristics at 64 sites over two years in restored northern jarrah ( Eucalyptus marginata ) forests of south-western Australia. Filters to use of restored forest were present for all bats, other than the open space group. We detected dynamic filters to use of restored forest by the open space edge group and unidirectional filters for the closed space edge and closed space groups. Filters to bat use of restored forests were species-specific and related to habitat, rather than landscape, features. In landscapes with relatively low patch-matrix contrast, such as the northern jarrah forest, management actions to reduce filters should focus on habitat features. To manage for the persistence of specific species within restored forest patches, tree density and midstory cover should aim to be at, or close to, reference forest levels. [ABSTRACT FROM AUTHOR]

• Matrix k was accurately predicted by machine learning models from the NMR T 2 data. • The cumulative T 2 data as inputs provided higher accuracy for k than original bins. • The optimal GBDT model was visualized and interpreted by the game-theory SHAP method. • The classical SDR and Timur-Coates models underestimated k by the fixed constants. • This work provides insight into the predictions of 'from curves to values'. Predicting the matrix permeability of subsurface sandstone aquifers is a formidable challenge. One test showing great promise is nuclear magnetic resonance (NMR), as it is the only advanced hydrogeophysical technique non-invasively measuring subsurface pore structure information and being applied in downhole well-log analysis with core calibration. Unfortunately, the classical NMR-based permeability models suffer from more than two empirical constants that limit prediction accuracy greatly. In this study, a NMR-data-driven method was reported with nine machine learning models. Results indicate that the type of input data strongly influences the machine learning modeling of matrix permeability. Using the cumulative T 2 relaxation data instead of the original T 2 data, a stronger agreement was found between experimental results and NMR estimates of matrix permeability from the gradient boosting decision tree model automatically tuned by GridsearchCV. The correlation coefficient reaches 0.92 with the lowest MSE of 0.12. Due to the nature of "black box" of machine learning model, the visualization and interpretation of the optimal model were performed through the Shapley Additive exPlanations method. The 38th variable of 501 ms in the cumulative T 2 spectrum positively contributes the most to the matrix permeability. However, the 26th variable of 31.6 ms provides the largest negative contribution to the final predicted matrix permeability. This work aims to provide a new idea to the "from curve-to-value" prediction process for a rapid and accurate matrix/bedrock permeability estimation via NMR T 2 data in deep sandstone aquifers and extensive porous rocks. [ABSTRACT FROM AUTHOR]

• Land-use changes and forest fragmentation are major threats to forest plant species. • A unimodal relationship exists between SGS intensity and genetic connectivity. • In fragmented landscapes, SGS is primarily shaped by past gene flows. • A progressive replacement of forest specialists by generalists is likely to occur. • Conserving forest plant diversity implies maintaining a high genetic connectivity. In many rural landscapes, woodland typically consists of small fragments of different habitat quality and age, embedded in a more or less intensively managed agricultural matrix. Genetic consequences on forest plant populations remain largely unknown. Here we explore whether genetic diversity, spatial genetic structure (SGS) and underlying gene flow are influenced by current and past permeability of the matrix in fragmented landscapes. We compare SGS of the generalist Geum urbanum and the forest specialist Primula elatior across three agricultural landscapes differing by their composition and management intensity. We use non-spatial and spatially informed approaches based upon multilocus genotypes to detect SGS and evaluate the respective importance of historical and contemporary gene flow. Results suggest that a low matrix permeability tends to disrupt gene flow, reducing SGS in populations of the two species. This effect is stronger for the forest specialist than for the generalist, as the former exhibits both low fecundity and dispersal limitation, and requires a higher habitat quality to maintain metapopulations. The current and past permeability of the matrix to gene vectors (seed dispersers and pollinators) explains the apparent unimodal relationship between SGS intensity and genetic connectivity. These results show the susceptibility of forest plant specialists to fragmentation and highlight the need for conserving the most ancient forest fragments and restoring a high functional connectivity among forest patches within agricultural landscapes. [ABSTRACT FROM AUTHOR]

Tackling the global threat of habitat fragmentation on biodiversity requires knowledge of how species move within agricultural landscapes. However, the specific mechanisms influencing dispersal within such landscapes remain poorly understood. The objective of our study was to assess how matrix type (improved pasture, native pasture or crop) and structure (grass height) influence fine-scale reptile movement, as well as influences of crop sowing direction and setting-sun position. In an agricultural region of south-eastern Australia, we first released 20 individuals of an arboreal gecko ( Christinus marmoratus ) at set distances from trees to determine the distance at which they could perceive their tree habitat (perceptual range). We then translocated 36 individuals into six matrix environments within their perceptual range of isolated trees to examine how gecko movement was modified by the type and structure of the matrix. We also recorded crop sowing direction and setting-sun position and examined all recorded tracks using angular statistics. We found that geckos exhibited a perceptual range of 40–80m. Short matrix environments promoted direct movements towards trees, irrespective of matrix type. Furthermore, movements were significantly affected by crop sowing direction with individuals following the planted lines. Our study has three significant implications: (i) restoring mature tree spacing to 80 m apart will assist gecko movements, (ii) targeted management for low pasture height, such as by maintaining directional narrow strips of low vegetation among taller pastures, might assist movement and facilitate increased connectivity, (iii) directional sowing of crops between habitat patches presents a simple but potentially effective tool for reconnecting fragmented landscapes. [ABSTRACT FROM AUTHOR]

We conducted pulse-decay permeability experiments on Utica and Permian shale samples to investigate the effect of rock mineralogy and pore structure on the transport mechanisms using a non-adsorbing gas (argon). The mineralogy of the shale samples varied from clay rich to calcite rich (i.e. clay poor). Our permeability measurements and scanning electron microscopy images revealed that the permeability of the shale samples whose pores resided in the kerogen positively correlated with organic content. Our results showed that the absolute value of permeability was not affected by the mineral composition of the shale samples. Additionally, our results indicated that clay content played a significant role in the stressdependent permeability. For clay-rich samples, we observed higher pore throat compressibility, which led to higher permeability reduction at increasing effective stress than with calcite-rich samples. Our findings highlight the importance of considering permeability to be stress dependent to achieve more accurate reservoir simulations especially for clay-rich shale reservoirs. [ABSTRACT FROM AUTHOR]

Greywacke of the Waipapa and Torlesse (Composite) Terrane form the basement of the Taupo Volcanic Zone (TVZ), New Zealand. Together with inferred buried lavas, domes and igneous complexes they are likely to be the dominant rock type prevailing at depths > 4 km beneath the TVZ. A fundamental understanding of the rock properties of the deep formations is of utmost importance for the exploration of deep unconventional geothermal resources. An outcrop analogue study was conducted to improve the understanding of the thermo-physical rock properties of likely deep buried rock formations beneath the TVZ. A total of 145 core samples were taken at 10 locations inside and outside the TVZ and their grain and bulk density, porosity, matrix permeability, bulk thermal conductivity and specific heat capacity, and the compressional and shear wave velocities measured on oven-dry samples. Additional tests of the unconfined compressive strength were conducted for selected greywacke samples to quantify their mechanical rock strength. The obtained data indicates that the thermo-physical rock properties are mainly controlled by porosity, and minor by mineralogy, texture and grain size. Samples from Waipapa-type and Torlesse-type greywacke exhibit minor rheological differences, with Waipapa-type greywacke having lowest porosity (about 1% vs. 3%) and highest bulk thermal conductivity (2.5 W m − 1 K − 1 vs. 1.7 W m − 1 K − 1 ) and specific heat capacity (0.8 kJ kg − 1 K − 1 vs. 0.7 kJ kg − 1 K − 1 ). Matrix permeability is < 1E-16 m 2 for all greywacke samples. Tested lavas exhibit heterogeneous rock properties due to their wide range of porosity (< 1% up to 32%). The thermo-physical rock properties were tested at laboratory conditions (ambient temperature and pressure), which do not reflect the in situ conditions at greater depth. With depth, thermal conductivity and acoustic wave velocity are likely to decrease caused by micro fractures resulting from thermal cracking of the rock, while specific heat capacity increases. The data presented in this paper are expected to improve the statistical confidence on input data to geophysical and thermo-hydro-mechanical numeric models, and the ability to forecast rock properties at greater depths of the TVZ. [ABSTRACT FROM AUTHOR]

In regard to evaluating tissue banking methods used to preserve or otherwise treat (process) soft allograft tissue, current tests may not be sufficiently sensitive to detect potential damage inflicted before, during, and after processing. Using controlled parameters, we aim to examine the sensitivity of specific biomechanical, electrical, and biological tests in detecting mild damage to collagen. Fresh porcine pulmonary heart valves were treated with an enzyme, collagenase, and incubated using various times. Controls received no incubation. All valves were cryopreserved and stored at -135 °C until being rewarmed for evaluation using biomechanical, permeability, and cell viability tests. Statistically significant time dependent changes in leaflet ultimate stress, (p = 0.006), permeability (p = 0.01), and viability (p ≤ 0.02, four different days of culture) were found between heart valves subjected to 0-15 min of collagenase treatment (ANOVA). However, no statistical significance was found between the tensile modulus of treated and untreated valves (p = 0.07). Furthermore, the trends of decreasing and increasing ultimate stress and viability, respectively, were somewhat inconsistent across treatment times. These results suggest that permeability tests may offer a sensitive, quantitative assay to complement traditional biomechanical and viability tests in evaluating processing methods used for soft tissue allografts, or when making changes to current validated methods. Multiple test evaluation may also offer insight into the mechanism of potential tissue damage such as, as is the case here, reduced collagen content and increased tissue porosity. [ABSTRACT FROM AUTHOR]

The Lower Silurian Longmaxi shale and the Lower Cambrian Niutitang shale are typical marine shales in China, promising for shale gas production, whereas the gas production from these two formations vary considerably because of the different flow properties determined by geology and lithology conditions. Matrix permeability, compared with fracture permeability, is an important factor controlling the long-term gas production from shale gas reservoirs. However, matrix permeability is difficult to measure at field due to the constrained measuring conditions. In this study, the Pressure-decay method was applied to measure the matrix permeability of the relatively high permeability Longmaxi and low permeability Niutitang shales. Moreover, controls of geochemical and geological factors on the matrix permeability were investigated for these two gas shales, differing in buried depth, porosity, Total Organic Carbon (TOC) contents and thermal maturity. Furthermore, the effects of dominant controlling factors on the matrix fluid conductivity were analyzed. Results show that matrix permeability increases with TOC content at different rates for Longmaxi and Niutitang shales. The difference in pore structure and pore-size distribution between the two shales is the main reason for the different matrix permeability and gas production. In addition, the development of organic nano pores with the partial fill-in of the minerals in the Niutitang shale was observed through the Scanning Electron Microscope (SEM), accounting for the contradiction of high porosity and low matrix permeability in the Niutitang shale. The precise determination of intermediate parameter in the Pressure-decay method is the key control for the accuracy of matrix permeability measurement and our study improves the understanding of the importance of pore-size distribution on flow properties in the matrix of shale gas reservoirs. [ABSTRACT FROM AUTHOR]

The dynamics of fluids and their interaction with surfaces in Unconventional Gas Reservoirs (UGRs) are very different from those in conventional systems. The physics of flow through the matrices of these reservoirs are not well understood. The small size of flow conduits which is comparable to the gas mean free path results in a deviation from Darcy to slip, transition and free molecular flow regimes. Solving Navier–Stokes (N–S) equations with modified boundary conditions has so far been the best practical approach to describe these flow behaviours. In this paper, a study of slip flow in shale gas reservoirs is presented. Several permeability measurements were performed using three shale rock samples to study the slip permeability. The Maxwellian type slip boundary conditions were used in N–S equations to obtain the slip coefficients and tangential momentum accommodation coefficient (TMAC) in porous media from the experimental data. Our results show that slip coefficients in porous media are higher than those in non-porous systems. In addition, it is found that the TMAC is smaller in porous media in comparison to flow in non-porous materials. These observations, which are attributed to greater surface area and roughness, are in agreement with literature data, which are limited to flow through individual micro conduits. The outcomes of this study will be useful for accurate prediction of gas flow rate in shale/tight gas reservoirs when using slip boundary conditions. [ABSTRACT FROM AUTHOR]