experimental study of fluid transport processes in the matrix system of the european organic rich shales i scandinavian alum shale abstract this contribution presents results from a laboratory study investigating the fluid gas water transport properties in the matrix system of the scandinavian alum shale the maturity of the organic matter of the shale samples ranged between 0 5 and 2 4 vitrinite reflectance vr r gas he ar ch 4 and water flow properties were determined at effective stresses ranging between 5 and 30 mpa and a temperature of 45 c the effects of different controlling factors parameters on the fluid conductivity including permeating fluid moisture content anisotropy heterogeneity effective stress pore pressure and load cycling were analyzed and discussed pore volume measurements by helium expansion were conducted under controlled in situ effective stress conditions on a limited number of plugs drilled parallel and perpendicular to bedding for alum shale the intrinsic permeability coefficients measured parallel and perpendicular to bedding 6 10 22 8 10 18 m 2 were within the range previously reported for other shales and mudstones permeability coefficients were strongly dependent on permeating fluid moisture content anisotropy effective stress and other sample to sample variations the intrinsic absolute permeabilities measured with helium were consistently higher up to five times than those measured with argon and methane permeability coefficients he ch 4 measured on a dry sample were up to six times higher than those measured on an as received sample depending on effective stress the effect of moisture on measured permeability coefficients became more significant as effective stress increased permeability coefficients he ch 4 measured parallel to bedding were up to more than one order of magnitude higher than those measured perpendicular to bedding parallel to bedding all samples showed a nonlinear reduction in permeability with increasing effective stress 5 30 mpa the stress dependence of permeability could be well described by an exponential relationship

mechanical properties of shale gas reservoir rocks part 2 ductile creep brittle strength and their relation to the elastic modulus we studied the elastic moduli ductile creep behavior and brittle strength of shale gas reservoir rocks from barnett haynesville eagle ford and fortst john shale in a series of triaxial laboratory experiments we found a strong correlation between the shale compositions in particular the volume of clay plus kerogen and intact rock strength frictional strength and viscoplastic creep viscoplastic creep strain was approximately linear with the applied differential stress the reduction in sample volume during creep suggested that the creep was accommodated by slight pore compaction in a manner similar to instantaneous strain there was more viscoplastic creep in samples deformed perpendicular to the bedding than parallel to the bedding the tendency to creep also correlated well with the static young s modulus we explained this apparent correlation between creep behavior and elastic modulus by appealing to the stress partitioning that occurs between the soft components of the shales clay and kerogen and the stiff components quartz feldspar pyrite and carbonates through a simple 1d analysis we found that a unique relation between the creep compliance and elastic modulus independent of composition and orientation can be established by considering the individual creep behavior of the soft and stiff components that arises from the stress partitioning within the rock this appears to provide a mechanical explanation for why long term ductile deformational properties can appear to correlate with short term elastic properties in shale gas reservoir rocks

pore structure gas storage and matrix transport characteristics of lacustrine newark shale abstract shale gas production in the u s fuelled research activities in unconventional reservoir rock characterization most studies focused on organic rich shales of marine origin while disregarding lacustrine sequences in this study thirteen lacustrine shale samples from the newark basin nj usa are comprehensively characterised in terms of pore structure gas storage and matrix transport characteristics these thermally overmature vrr 1 4 2 7 shales have a na rich heterogeneous mineralogy with toc contents of up to 3 6 methane sorption capacity and pore structure parameters as identified with low pressure n2 physisorption microporosity bet surface area are neither interrelated with each other nor with any shale components e g clay content toc in contrast porosity shows a positive correlation with toc content which is also typical for many thermally overmature marine shale sequences correspondingly porosity and toc positively correlate to bedding parallel matrix permeability coefficients between 2 and 80 nd at 40 mpa effective stress in contrast permeability coefficients perpendicular to bedding are two to three orders of magnitude lower compared to previous studies on marine lithotypes newark shales have rather poor gas storage properties with average he porosities of 2 3 and average methane sorption capacities of 0 047 mmol g 1

continued decrease of ice flow velocity at lewis glacier mount kenya east africa our earlier monitoring program on lewis glacier mount kenya indicated a slow down of the ice flow to january 1982 while based on the numerical modeling of the ice dynamics a further drastic decrease of the ice flow was predicted from the 1978 to the 1985 datum this paper presents velocity measurements over the years 1982 83 1984 and 1985 changes of ice flow conditions from 1978 to the mid 1980s are characterized by a velocity decrease by nearly half a decrease of the maximum mass flux by more than half a flattening and up glacier shift of the velocity and mass flux maxima an up glacier displacement of the transition bet een prevailingly longitudinal crevasses in the lower glacier and transverse crevasses in the upper glacier and a terminus retreat by about 50 m in consequence of the very weak ice flow remaining in lewis glacier thinning and terminus retreat of the glacier are now primarily controlled by the ill situ net balance

mechanical properties of shale gas reservoir rocks part 1 static and dynamic elastic properties and anisotropy abstractunderstanding the controls on the elastic properties of reservoir rocks is crucial for exploration and successful production from hydrocarbon reservoirs we studied the static and dynamic elastic properties of shale gas reservoir rocks from barnett haynesville eagle ford and fort st john shales through laboratory experiments the elastic properties of these rocks vary significantly between reservoirs and within a reservoir due to the wide variety of material composition and microstructures exhibited by these organic rich shales the static young s modulus and dynamic p and s wave moduli elastic parameters generally decrease monotonically with the clay plus kerogen content the variation of the elastic moduli can be explained in terms of the voigt and reuss limits predicted by end member components however the elastic properties of the shales are strongly anisotropic and the degree of anisotropy was found to correlate with the amount of clay and organic content as well as the shale fab

rock glaciers and mountain hydrology a review abstract in mountainous regions climate change threatens cryospheric water resources and understanding all components of the hydrological cycle is necessary for effective water resource management rock glaciers are climatically more resilient than glaciers and contain potentially hydrologically valuable ice volumes and yet have received less attention even though rock glacier hydrological importance may increase under future climate warming in synthesising data from a range of global studies we provide the first comprehensive evaluation of the hydrological role played by rock glaciers we evaluate hydrological significance over a range of temporal and spatial scales alongside the complex multiple hydrological processes with which rock glaciers can interact diurnally seasonally annually decadally and both at local and regional extents we report that although no global extent complete inventory for rock glaciers exists currently recent research efforts have greatly elaborated spatial coverage using these research papers we synthesise information on rock glacier spatial distribution morphometric characteristics surface and subsurface features ice storage and hydrological flow dynamics water chemistry and future resilience from which we provide the first comprehensive evaluation of their hydrological contribution we identify and discuss long intermediate and short term timescales for rock glacier storage allowing a more balanced assessment of the contrasting perspectives regarding the relative significance of rock glacier derived hydrological contributions compared to other water sources we show that further empirical observations are required to gain a deeper hydrological understanding of rock glaciers in terms of i their genesis and geomorphological dynamics ii total ice water volume iii water discharge and iv water quality lastly we hypothesise that at decadal and longer timescales under future climate warming degradation of ice within rock glaciers may represent an increasing hydrological contribution to downstream regions and thus increased hydrological significance while rock glacier water stores persist

tropical climate at the last glacial maximum inferred from glacier mass balance modeling model derived equilibrium line altitudes elas of former tropical glaciers support arguments based on other paleoclimate data for both the magnitude and spatial pattern of terrestrial cooling in the tropics at the last glacial maximum lgm relative to the present lgm elas were maintained by air temperatures that were 3 5 to 6 6 c lower and precipitation that ranged from 63 wetter in hawaii to 25 drier on mt kenya africa our results imply the need for a 3 c cooling of lgm sea surface temperatures in the western pacific warm pool sensitivity tests suggest that lgm elas could have persisted until 16 000 years before the present in the peruvian andes and on papua new guinea

on the relation of net balance ice flow and surface lowering of lewis glacier mount kenya east africa 1982 86 the second 4 year phase of a long term observation program on lewis glacier mount kenya was completed in march 1986 as for the 1978 82 interval net balance results at a stake network and repeated mapping of the ice surface topography allowed assessment of the mass economy by both glaciological and geodetic methods the general findings from the 1978 82 observations are confirmed the vertical flow component is directed downward in the upper glacier and upward in the lower glacier surface lowering and negative net balance increase down glacier ice flow mitigates surface lowering by the negative net balance in the lower glacier but enhances it in the upper glacier however the major difference between the 1982 86 and 1978 82 periods is the progressive slow down of ice flow this entails a reduction of mass re distribution in consequence of which the surface lowering becomes increasingly dependent on the ill situ net halance it is expected that this circumstance will simplify any inference on future glacier behavior i introduction as outlined by hoinkes 1970 the mass economy of glaciers can be determined independe ntly from the glacio logical and geodetic methods in the glaciological approach net balance is monitored at a network of stakes by taping at regular time intervals the distance from a fixed mark on the stake to the glacier surface the geo detic method consists of repeated mapping of the glacier surface topography wh ile at each stake location the net balance may differ from the actual change in surface elevation volume changes obtained from the two techniques should be consistent when integrated over the glacier as a whole concurrent application of these two technique is highly desirable but is not often realized our long term and ongoing field program on lewis glacier mount kenya hastenrath 1984 p 143 284 is designed to use both the glaciological and geodetic approaches in particular the monitoring of net balance at a stake network together with repeated mapping of the ice surface topography allows in sight into the role of the flow dynamics for the actual surface lowering in the upper and lower glacier an earlier paper by hastenrath 1983 discussed the findings from a combination of the two methods for the time span 1978 82 the present paper reports the results for the 1982 86 interval

effects of rock mineralogy and pore structure on stress dependent permeability of shale samples 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 adsorbin

rock glacier dynamics stick slip motion coupled to hydrology 1 we demonstrate an approach to simulate rock glacier dynamics based on a three dimensional stick slip model coupled to a simple model of melt water dispersion simulation results account for observed kinematic discontinuities and exhibit a distribution of slip event sizes that is characterized by large fluctuations following a power law the model presents a feedback loop of dynamics and internal structure 1 the evolution of shear horizons which are correlated to melt water occurrence can be seen and 2 melt water distribution narrows to regions of maximum slip although this approach is promising improvements in some details must be made the solution for stress transfer accompanying slip has been taken from a model of a sheared body that is vertically constrained in future models the boundary conditions must be modified to that of a body confined only at its base additionally a heuristic treatment of hydrology currently used must be further quantified

analyses of uav and gnss based flow velocity variations of the rock glacier lazaun otztal alps south tyrol italy abstract flow velocities were measured on the active rock glacier lazaun by eleven gnns 2006 2018 and six uav campaigns 2016 2018 to better understand the flow pattern and its possible causes this medium sized active rock glacier is located w of kurzras maso corto in the schnals senales valley in the southern otztal alps south tyrol northern italy the uav data were used to generate displacement maps by image correlation techniques to analyse surface lowering and accumulation processes and to interpret the geomorphology base on shaded relief images the spatial information from uav contributes much more to the understanding of the rock glacier flow patterns as the point based gnss measurements even when the uav based horizontal displacement analyses are less precise the level of detection lod for the absolute horizontal displacements derived by image correlation from uav data ranges between 0 05 and 0 15 m a comparison of the displacement lengths shows that the uav derived displacement vectors deviate in average about 0 05 m from the gnss measured displacement lengths the deviation in the displacement directions is smaller when the absolute displacement is higher and ranges in zones with an absolute displacement higher than 0 3 m in dependence to the data quality between 0 and 4 consequently when planning a uav based rock glacier monitoring the achievable data accuracy rock glacier flow velocity and the time span must be considered analyses of the rock glacier velocities from gnss and uva data show that the calculated horizontal mean velocity increased significantly from 2 mm day in 2006 up to 6 mm day in the period 2012 to 2016 and then decreased to values of 3 4 mm day until 2018 we assume that internal structures and hydrogeology are essential parameters that control the flow mechanism of rock glacier lazaun particularly the shear horizon composed of debris and banded ice that is present at the base of the permafrost body and the unfrozen groundwater bearing sediment layer between the shear horizon and the bedrock we conclude that climate warming caused increased infiltration of meltwater into the shear horizon and that this is the main driving force for the movement of the rock glacier increased meltwater infiltration as result of climate warming caused an increase of flow velocity until 2016 the observed thickness loss near the front of the rock glacier indicates increased melting of permafrost ice resulting in a significant loss of permafrost ice during the last years this process that particularly occurs in the lower part of the rock glacier is believed to be responsible for the decrease in flow velocity since 2017

variation of ice velocity at lewis glacier mount kenya kenya verification midway into a forecast le ralentissement du glacier lewis avait ete prevu a 50 entre 1978 et 1985 a mi parcours en 1982 une reduction de 20 a ete constatee en accord avec ces previsions le flux de matiere a diminue d au moins 25 les valeurs relativement rapides se situent durant la saison seche de janvier fevrier

water controls the seasonal rhythm of rock glacier flow abstract rock glaciers are creeping periglacial landforms experiencing strong acceleration during recent atmospheric warming and raising concerns with regard to their future behaviour and stability high resolution kinematic observations show strong seasonal and multi annual variations in rock glacier creep but the linking mechanisms to environmental forcing remain poorly understood and lack quantitative models here we investigate the interaction between rock glacier creep and climatic forcing temperature and precipitation by developing a novel conceptual and numerical modelling approach the model is constrained and the results are compared with data from the dirru rock glacier vallis ch we are able to reproduce the observed velocity variations both in magnitude and phase on seasonal and inter annual time scales we find that water from liquid precipitation and snow melt rather than air temperature is the main driver of variations in rock glacier creep our results imply that the influence of water on rock glacier creep is fundamental and must be considered when investigating the historic and future evolution of rock glaciers

experimental investigation of matrix permeability of gas shales predicting long term production from gas shale reservoirs has been a major challenge for the petroleum industry to better understand how production profiles are likely to evolve with time we have conducted laboratory experiments examining the effects of confining stress and pore pressure on permeability experiments were conducted on intact core samples from the barnett eagle ford marcellus and montney shale reservoirs the methodology used to measure permeability allows us to separate the reduction of permeability with depletion because of the resultant increase in effective confining stress and the increase in permeability associated with knudsen diffusion and molecular slippage also known as klinkenberg effects at very low pore pressure by separating these effects we are able to estimate the relative contribution of both darcy and diffusive fluxes to total flow in depleted reservoirs our data show that the effective permeability of the rock is significantly enhanced at very low pore pressures because of the slippage effects we use the magnitude of the klinkenberg effect to estimate the effective aperture of the flow paths within the samples and compare these estimates to scanning electron microscopy image observations our results suggest effective flow paths to be on the order from tens of nanometers in most samples to 100 200 nm in a relatively high permeability eagle ford sample finally to gain insight on the scale dependence of permeability measurements the same core plugs were crushed and permeability was again measured at the particle scale using the so called gas research institute method the results show much lower permeability than the intact core samples with very little correlation to the measurements on the larger scale cores

geological controls on matrix permeability of devonian gas shales in the horn river and liard basins northeastern british columbia canada abstract controls of matrix permeability are investigated for devonian gas shales from the horn river and liard basins in northeastern british columbia canada mineralogy is varied with high carbonate high quartz and moderate quartz carbonate and clay rich strata quartz content varies between 2 and 73 carbonate varies between 1 and 93 and clay varies between 3 and 33 the toc content ranges between 0 3 and 6 wt and porosity varies between about 1 and 7 for horn river basin samples quartz is mainly biogenic in origin derived from radiolarians toc content increases with the quartz content suggesting the toc and quartz both are derived from siliceous phytoplankton a positive relationship between porosity and quartz content is due to the positive relationship between quartz and toc matrix permeability parallel to bedding varies between 7 5e 02 and 7 1e 07 md at an effective stress of 15 mpa variation in permeability is due to a complex combination of factors that includes origin and distribution of minerals pore size distribution and fabric mercury intrusion capillary curves indicate that the higher matrix permeability values 2e 03 md occurs in samples that contain interconnected pore apertures greater than 16 m even when these samples may contain less macropores than low permeability samples the fabric of high permeability samples can be either isotropic or anisotropic however permeability of anisotropic samples is more sensitive to changes in effective stress than isotropic samples more highly anisotropic samples contain moderate amounts of quartz carbonate and in some clay high permeability samples that contain a more balanced ratio between micro meso and macroporosity would not only have faster flow rates but also greater access to sorbed gas within the microporosity compared to samples that lack mesopores several muskwa samples compared to evie and besa river samples contain higher quartz moderate clay and high toc content coupled with high permeability less sensitivity to effective stress and balanced ratios between micro meso and macroporosity would be a lower exploration risk due a greater propensity to fracture the ability to produce and store hydrocarbons due to higher toc contents and greater communication between macropores and micropores in the organic and clay fractions

net balance surface lowering and ice flow pattern in the interior of lewis glacier mount kenya kenya analyse des bilans glaciaires et des vitesses du glacier lewis 1978 82 et cartographie aerienne

ice flow and mass changes of lewis glacier mount kenya east africa observations 1974 86 modelling and predictions to the year 2000 ad

introduction energy and the subsurface this theme issue covers topics at the forefront of scientific research on energy and the subsurface ranging from carbon dioxide co2 sequestration to the recovery of unconventional shale oil and gas resources through hydraulic fracturing as such the goal of this theme issue is to have an impact on the scientific community broadly by providing a self contained collection of articles contributing to and reviewing the state of the art of the field this collection of articles could be used for example to set the next generation of research directions while also being useful as a self study guide for those interested in entering the field review articles are included on the topics of hydraulic fracturing as a multiscale problem numerical modelling of hydraulic fracture propagation the role of computational sciences in the upstream oil and gas industry and chemohydrodynamic patterns in porous media complementing the reviews is a set of original research papers covering growth models for branched hydraulic crack systems fluid driven crack propagation in elastic matrices elastic and inelastic deformation of fluid saturated rock reaction front propagation in fracture matrices the effects of rock mineralogy and pore structure on stress dependent permeability of shales topographic viscous fingering and plume dynamics in porous media convection this article is part of the themed issue energy and the subsurface

recession of yanamarey glacier in cordillera blanca peru during the 20th century for yanamarey glacier in cordillera blanca peru mostly situated between about 5000 and 4600 m maps of the surface topography at a scale of 1 5000 obtained by terrestrial triangulation for 1973 1982 and 1988 and by aerial photogrammetry for 1948 and 1962 are compared with the glacier boundaries from a 1939 map and an undated maximum extent inferred from moraine morphology the glacier length decreased from the maximum 2800 m to 1600 m in 1948 and to 1250 m in 1988 with an accompanying decrease in area from 17 10 5 to 10 10 5 and thence to 8 10 5 m 2 the shrinkage of ice volume was 35 10 6 m 3 from the maximum to 1948 and 29 10 6 m 3 from 1948 to 1988 compared to a total remaining icevolume of about 25 10 6 m 3 in 1988 this quantitative assessment of mass loss rates creates the observational basis for sensitivity studies of the climatic forcing

relationships among composition porosity and permeability of longmaxi shale reservoir in the weiyuan block sichuan basin china abstract shale composition might influence the petrophysical properties of shale reservoirs the relationships among composition porosity and permeability of longmaxi shale in weiyuan area sichuan basin china were systematically investigated by the integration of geochemical mineralogical and petrophysical data the cumulative pore volume of the organic rich longmaxi shale is mainly contributed of pores with diameter of 2 nm 100 nm the total organic carbon toc content is the main control on porosity as the percentage of organic porosity is 60 for the organic rich shales the clay content is positively correlated with porosity partly due to the clay associated interparticle pores and pores developed in organo clay complex carbonate and quartz content dilute the toc and clay content which accounts for their negative relationships with porosity in terms of shale composition the clay content exerts the strongest influence on permeability at low clay contents 30 the clay content exhibits a negative impact on permeability because abundant clay minerals block pore throats reduce the resistance to mechanical compaction and result in low permeability the influence of the pore network on permeability is evident from a positive correlation between the pore volume percentage of meso pores volmes and permeability which is due to a fine and coarse meso pores including a large fraction of organic pores which have better connectedness than other interparticle mostly 50 nm and intraparticle mainly isolated pores and b large quantities of fine and coarse meso pores increasing the capacity to access other pores which form the dominated pathways for gas flows according to the above illustrated relationships appropriate porosity and permeability indicating fine storage capacity and favorable flow capacity occur in the longmaxi shale in weiyuan block which implies good reservoir quality and excellent exploration prospects in this region

mapping and quantifying sediment transfer between the front of rapidly moving rock glaciers and torrential gullies abstract the sedimentary connection which may occur between the front of active rock glaciers and torrential channels is not well understood despite its potential impact on the torrential activity characterizing the concerned catchments in this study dems of difference dods covering various time intervals between 2013 and 2016 were obtained from lidar derived multitemporal dems for three rapidly moving rock glaciers located in the western swiss alps the dods were used to map and quantify sediment transfer activity between the front of these rock glaciers and the corresponding underlying torrential gullies sediment transfer rates ranging between 1500 m3 y and 7800 m3 y have been calculated depending on the sites sediment eroded from the fronts generally accumulated in the upper sectors of the torrential gullies where they were occasionally mobilized within small to medium sized debris flow events a clear relation between the motion rates of the rock glaciers and the sediment transfer rates calculated at their fronts could be highlighted along with the size of the frontal areas rock glacier creep rates influence thus directly sediment availability in the headwaters of the studied torrents the frequency magnitude of debris flow events varied between sites and was mainly related to the concordance of local factors such as topography water availability sediment availability or sediment type

petrographical and petrophysical characterization of the late cretaceous naparima hill formation central range trinidad west indies abstract the late cretaceous naparima hill formation in the south trinidad basin southeast caribbean is a prolific source rock with a potential for unconventional hydrocarbon exploration it is exposed across the central range and extends to the city of san fernando this study characterized the naparima hill source rock using petrographic analysis techniques x ray diffraction and thin section analysis and petrophysical techniques these techniques were applied to outcrop samples that were collected from 11 locations firstly petrographic analysis was used to determine the mineral composition and lithofacies secondly plugs were taken perpendicular to bedding and the bulk density was determined in dry conditions thirdly porosity and grain density were determined using a porosimeter at ambient conditions finally permeability measurements were obtained at 10 mpa to 130 mpa effective pressures using the transient pulse decay technique the results show that the source rock is dominated by silica with carbonate as secondary minerals four lithofacies were identified a siliceous calcareous mudstone b calcareous mudstones interbedded with black chert c carbonate rich mudstone with nodular chert and d siliceous mudstone ranges of 5 9 to 30 8 2362 to 2668 kg m3 and 1804 to 2350 kg m3 were determined for porosity grain density and bulk density respectively the permeability ranges from 3 96 10 20 to 5 94 10 18 m2 and shows very little dependence on the effective pressure permeability and porosity are moderately correlated r2 0 6 there is no relationship between permeability and mineralogical composition the observed microfractures diagenetic processes and grain sorting are factors that have affected the permeability porosity relationship to varying degrees however none of these factors can be considered as the main intrinsic factor controlling the permeability of the samples overall it is difficult to predict the permeability of the naparima hill formation with any of the proxies density mineralogy and porosity determined in this study

a 10 300 year old permafrost core from the active rock glacier lazaun southern otztal alps south tyrol northern italy two cores were drilled on rock glacier lazaun in the southern otztal alps n italy the average ice content of core lazaun i is 43 vol and of core lazaun ii is 22 vol radiocarbon dating of plant macrofossil remains of core lazaun i yielded ages ranging from 8960 cal yr bp at a depth of ca 23 5 m to 2240 cal yr bp at a depth of 2 8 m indicating that the ice near the base is approximately 10 300 yr old the rock glacier was intact since that time and the ice persisted even during warm periods of the holocene an ice free debris layer between 16 8 and 14 7 m separates the rock glacier into two frozen bodies inclinometer measurements indicate that both frozen bodies are active and that deformation occurs within a shear horizon at a depth of 20 25 m at the base of the lower frozen body and to a minor extent at a depth of approximately 14 m at the base of the upper frozen body the ice free debris layer in the middle of the lazaun rock glacier indicates a more than five centennial long drought period which dates to about 4300 3740 cal yr bp

element release and reaction induced porosity alteration during shale hydraulic fracturing fluid interactions the use of hydraulic fracturing techniques to extract oil and gas from low permeability shale reservoirs has increased significantly in recent years during hydraulic fracturing large volumes of water often acidic and oxic are injected into shale formations this drives fluid rock interaction that can release metal contaminants e g u pb and alter the permeability of the rock impacting the transport and recovery of water hydrocarbons and contaminants to identify the key geochemical processes that occur upon exposure of shales to hydraulic fracturing fluid we investigated the chemical interaction of hydraulic fracturing fluids with a variety of shales of different mineralogical texture and composition batch reactor experiments revealed that the dissolution of both pyrite and carbonate minerals occurred rapidly releasing metal contaminants and generating porosity oxidation of pyrite and aqueous fe drove precipitation of fe iii oxy hydroxides that attenuated the release of these contaminants via co precipitation and or adsorption the precipitation of these oxy hydroxides appeared to limit the extent of pyrite reaction enhanced removal of metals and contaminants in reactors with higher fluid ph was inferred to reflect increased fe oxy hydroxide precipitation associated with more rapid aqueous fe ii oxidation the precipitation of both al and fe bearing phases revealed the potential for the occlusion of pores and fracture apertures whereas the selective dissolution of calcite generated porosity these pore scale alterations of shale texture and the cycling of contaminants indicate that chemical interactions between shales and hydraulic fracturing fluids may exert an important control on the efficiency of hydraulic fracturing operations and the quality of water recovered at the surface

effect of tortuosity on the stress dependent permeability of tight sandstones analytical modelling and experimentation abstract accurately modelling stress dependent permeability is of great significance to predicting the oil gas production of unconventional tight sandstone reservoirs with time dependent pressure depletion the classic theory indicates that the porosity exponents of the capillary tube model and the fracture model are 2 and 3 respectively however experimental results demonstrate that the value of the porosity exponent usually varies greatly the effect of the nonuniform distribution of tortuosity on stress dependent permeability is rarely studied assuming that tight sandstones with natural microfractures can be represented by a bundle of tortuous capillary tubes and parallel plate fractures a new stress dependent permeability model of tight sandstones is proposed based on fractal theory considering the tortuosity effect the research results show that the porosity exponents of the tortuous capillary tube model and the tortuous plate fracture model are 3 d t 2 and 2 d t respectively here d t is the tortuosity fractal dimension for the capillary tube model and the plate fracture model without tortuosity d t 1 their porosity exponents can be simplified to 2 and 3 respectively the tortuosity fractal dimension is one of the reasons causing the porosity exponent to deviate from the classic theoretical value the newly developed stress dependent permeability model is verified with experimental data determined using tight sandstone core samples from the yanchang formation in the ordos basin china the average error of the permeability prediction under different effective stresses is only 3 78 thus the newly developed model can accurately predict the stress dependent permeability of tight sandstones

terminus response of lewis glacier mount kenya kenya to sinusoidal net balance forcing on a calcule la reponse de la langue terminale du lewis glacier a une fluctuation sinusoidale du bilan de masse le profil des bilans en fonction de l altitude est transcrit separement suivant des axes orthogonaux bilan altitude on a couvert des amplitudes de bilans de 0 1 a 0 5 m a 1 de glace et d altitudes de 10 a 50 m respectivement sur des periodes allant de 20 a 1000 ans la prise en compte de la reponse du lewis glacier en comparaison avec des resultats analogues pour d autres glaciers alpins permet de caracteriser les traits generaux de la reponse des langues

diagnosing the imbalance of glaciar santa rosa cordillera raura peru for glaciar santa rosa in the cordillera raura peru the extent and volume are determined for 1980 and 1961 from topographic mapping and for two undated earlier stages lme and max from moraines the regime of the glacier in terms of ice flow and mass balance is evaluated for the 1977 83 period more than half of the water discharge from the glacier is not renewed by precipitation but supplied by the ice thinning the rate of surface lowering of 2 m a 1 liquid water equivalent corresponds to an energy amount for melting of 22 w m 2 sensitivity analyses of glaciar yanamarey in the nearby cordillera blanca show that such a decrease of energy available for melting could be produced by a cloudiness increase of one tenth an air temperature decrease of more than 2 c a decrease in specific humidity of 1 g kg 1 or some combination of heat budget processes such changes in the atmospheric environment would be required to stabilize the glacier at its recent volume as another indication of the recent imbalance the maximum volume flux is found about 100 m below the equilibrium line altitude under continuation of recent climatic conditions the glacier may disappear within a few decades these inferences corroborate a recent assessment for the neighboring cordillera blanca

experimental study of fluid transport processes in the matrix system of the european organic rich shales ii posidonia shale lower toarcian northern germany abstract a laboratory study has been conducted to investigate the transport of gases he ar ch 4 and water in the matrix of lower toarcian posidonia shale samples from three shallow boreholes in northern germany the maturity of the organic matter of the shale samples ranged between 0 53 and 1 45 vitrinite reflectance vr r the measurements were performed at effective stresses ranging between 6 and 37 mpa and a temperature of 45 c the effects of different controlling factors including permeating fluid maturity anisotropy moisture content and effective stress on the fluid conductivity were analyzed and discussed permeability coefficients measured perpendicular and parallel to bedding 3 10 22 to 9 7 10 17 m 2 were within the range previously reported for other shales and mudstones they exhibited a strong dependence on permeating fluid maturity anisotropy moisture content and effective stress the permeability coefficients measured with helium as permeate were consistently higher up to two times than those measured with argon and methane permeability coefficients measured with water were up to three orders of magnitude lower than klinkenberg corrected gas permeability coefficients measured with helium and methane under similar experimental conditions among the samples studied the lowest porosity and permeability coefficients were measured on samples of intermediate thermal maturity 0 88 vr r oil window permeability coefficients he ch 4 measured parallel to bedding were up to more than one order of magnitude higher than those measured perpendicular to bedding permeability coefficients measured with he and ch 4 on a dry sample were up to two times higher than those measured on a sample with the as received moisture content all samples showed a nonlinear reduction in permeability parallel to bedding with increasing effective stress 6 37 mpa the permeability anisotropy and stress dependence of permeability were controlled by the mineralogy

diagnosing the imbalance of yanamarey glacier in the cordillera blanca of peru a detailed glaciological observation program was conducted on the yanamarey glacier in the cordillera blanca of peru including the monitoring of net balance and ice flow velocity during 1977 1988 and mappings of the surface topography in 1973 1982 and 1988 these observations are here evaluated to combine net balance surface lowering and ice flow into a consistent picture of the mode of operation of a tropical glacier on the scale of a decade the glacier extends between 5100 and 4500 m with a total area of 9 105 m2 and length of about 1 3 km maximum flow velocity is 17 4 m yr 1 and maximum volume flux 336 103 m3 yr 1 in the ablation area net balance is about 6 m yr 1 and surface lowering 3 m yr 1 about half of the mean annual water discharge from the glacier of 80 l s 1 is not renewed by precipitation but supplied by the ice thinning the rate of surface lowering of 1 5 m yr 1 liquid water equivalent translates to a glacier average departure heat supply for melting of 16 w m 2 sensitivity analyses indicate that this could be produced by a cloudiness increase of less than one tenth an air temperature decrease of 2 c an increment in specific humidity of less than 1 g kg 1 or some combination of heat budget processes such changes in the atmospheric environment would be required to stabilize the glacier at its recent volume as another indication of the recent imbalance the maximum volume flux is found some 100 m below the equilibrium line altitude under continuation of the recent climatic conditions the glacier may survive for more than half a century

quantitative validation of pore structure characterization using gas slippage measurements by comparison with predictions from bundle of capillaries models abstract the use of gas slippage measurements as a tool for quantitative pore structure geometry characterization was investigated by comparing pore sizes estimated from gas slippage measurements to pore sizes predicted by bundle of capillaries models a large data set of gas slippage measurements was generated for the study by combining measurements made in our laboratory with measurements from seven previously published studies pore size was estimated from the gas slippage measurements using two models one assuming a circular cross sectional pore geometry and the other slot shaped when using a porosity function generated for the data set using experimental data and a theoretically derived tortuosity function pore sizes estimated from bundle of capillaries models yielded a good match to the pore sizes independently estimated from gas slippage data better agreement between the models exists when pores in high permeability rocks are modelled as having slot shaped cross sectional geometry and pores in low permeability rocks circular cross sectional geometry suggesting a systematic shift in pore morphology with changing permeability

an enhanced temperature index glacier melt model including the shortwave radiation balance development and testing for haut glacier d arolla switzerland an enhanced temperature index glacier melt model incorporating incoming shortwave radiation and albedo is presented the model is an attempt to combine the high temporal resolution and accuracy of physically based melt models with the lower data requirements and computational simplicity of empirical melt models represented by the degree day method and its variants the model is run with both measured and modelled radiation data to test its applicability to glaciers with differing data availability five automatic weather stations were established on haut glacier d arolla switzerland between may and september 2001 reference surface melt rates were calculated using a physically based energy balance melt model the performance of the enhanced temperature index model was tested at each of the four validation stations by comparing predicted hourly melt rates with reference melt rates predictions made with three other temperature index models were evaluated in the same way for comparison the enhanced temperature index model offers significant improvements over the other temperature index models and accounts for 90 95 of the variation in the reference melt rate the improvement is lower but still significant when the model is forced by modelled shortwave radiation data thus offering a better alternative to existing models that require only temperature data input

morphology genesis and distribution of nanometer scale pores in siliceous mudstones of the mississippian barnett shale research on mudrock attributes has increased dramatically since shale gas systems have become commercial hydrocarbon production targets one of the most significant research questions now being asked focuses on the nature of the pore system in these mudrocks our work on siliceous mudstones from the mississippian barnett shale of the fort worth basin texas shows that the pores in these rocks are dominantly nanometer in scale nanopores we used scanning electron microscopy to characterize barnett pores from a number of cores and have imaged pores as small as 5 nm key to our success in imaging these nanopores is the use of ar ion beam milling this methodology provides flat surfaces that lack topography related to differential hardness and are fundamental for high magnification imaging nanopores are observed in three main modes of occurrence most pores are found in grains of organic matter as intraparticle pores many of these grains contain hundreds of pores intraparticle organic nanopores most commonly have irregular bubblelike elliptical cross sections and range between 5 and 750 nm with the median nanopore size for all grains being approximately 100 nm internal porosities of up to 20 2 have been measured for whole grains of organic matter based on point count data from scanning electron microscopy analysis these nanopores in the organic matter are the predominant pore type in the barnett mudstones and they are related to thermal maturation nanopores are also found in bedding parallel wispy organic rich laminae as intraparticle pores in organic grains and as interparticle pores between organic matter but this mode is not common although less abundant nanopores are also locally present in fine grained matrix areas unassociated with organic matter and as nano to microintercrystalline pores in pyrite framboids intraparticle organic nanopores and pyrite framboid intercrystalline pores contribute to gas storage in barnett mudstones we postulate that permeability pathways within the barnett mudstones are along bedding parallel layers of organic matter or a mesh network of organic matter flakes because this material contains the most pores

fast deformation of perennially frozen debris in a warm rock glacier in the swiss alps an effect of liquid water 1 surface movement internal deformation and temperature were monitored over 5 years on buz north rock glacier a small rock glacier located at the lower limit of the permafrost belt in the swiss alps the permafrost in the rock glacier mainly consists of pebbles and cobbles filled with interstitial ice two inclinometers installed at 4 and 5 m depths showed fast deformation with large seasonal and interannual variations while the permafrost temperatures remained almost at the melting point the movement of the inclinometers coincided with changes in the surface velocities the deformation rapidly accelerated during snowmelt periods whereas it gradually decelerated below a dry snow cover in winter the frozen debris was more deformable than typical glacier ice at the melting point these phenomena suggest that the frozen debris is permeable to snowmelt water the fast deformation should result from significant annual relocation of debris particles which probably creates a network of air voids in the frozen debris that eventually allows water infiltration the meltwater infiltration accelerates the deformation by reducing effective stress resulting in the reduced strength of the frozen debris the refreezing of the pore water which depends on the cooling intensity in winter decelerates the deformation the combination of these processes controls the temporal variations in the deformation