gas and water flow in an excavation induced fracture network around an underground drift a case study for a radioactive waste repository in clay rock summary the excavation damaged zone edz surrounding a drift and in particular its evolution is being studied for the performance assessment of a radioactive waste underground repository a specific experiment called cdz was designed and implemented in the meuse haute marne underground research laboratory url in france to investigate the edz this experiment is dedicated to study the evolution of the edz hydrogeological properties conductivity and specific storage of the callovo oxfordian claystone under mechanical compression and artificial hydration firstly a loading cycle applied on a drift wall was performed to simulate the compression effect from bentonite swelling in a repository drift bentonite is a clay material to be used to seal drifts and shafts for repository closure purpose gas tests permeability tests with nitrogen and tracer tests with helium were conducted during the first phase of the experiment the results showed that the fracture network within the edz was initially interconnected and opened for gas flow particularly along the drift and then progressively closed with the increasing mechanical stress applied on the drift wall moreover the evolution of the edz after unloading indicated a self sealing process secondly the remaining fracture network was resaturated to demonstrate the ability to self seal of the cox claystone without mechanical loading by conducting from 11 to 15 repetitive hydraulic tests with monitoring of the hydraulic parameters during this hydration process the edz effective transmissivity dropped due to the swelling of the clay materials near the fracture network the hydraulic conductivity evolution was relatively fast during the first few days low conductivities ranging at 10 10 m s were observed after four months conversely the specific storage showed an erratic evolution during the first phase of hydration up to 60 days some uncertainty remains on this parameter due to volumetric strain during the sealing of the fractures the hydration was stopped after one year and cross hole hydraulic tests were performed to determine more accurately the specific storage as well as the hydraulic conductivity at a meter scale all hydraulic conductivity values measured at the injection interval and at the observation intervals were all below 10 10 m s moreover the preferential inter connectivity along the drift disappeared specific storage values at the observation and injection intervals were similar furthermore they were in agreement with the value obtained at the injection interval within the second hydration phase 60 days after starting hydration the graphical abstract synthesizes the evolution of the hydraulic gas conductivity for 8 intervals since the beginning of the cdz experiment the conductivity limit of 10 10 m s corresponds to the lower bound hydraulic definition of the edz and it is demonstrated that edz can be sealed this is a significant result in the demonstration of the long term safety of a repository

concretionary methane seep carbonates and associated microbial communities in black sea sediments abstract gas seeps in the euxinic northwestern black sea provide an excellent opportunity to study anaerobic methane based ecosystems with minimum interference from oxygen dependent processes an integrated approach using fluorescence and electron microscopy fluorescence in situ hybridization lipid biomarkers stable isotopes 13c and petrography revealed insight into the anatomy of concretionary methane derived carbonates currently forming within the sediment around seeps some of the carbonate concretions have been found to be surrounded by microbial mats the mats harbour colonies of sulphate reducing bacteria dss group and archaea anme 1 putative players in the anaerobic oxidation of methane isotopically depleted lipid biomarkers indicate an uptake of methane carbon into the biomass of the mat biota microbial metabolism sustains the precipitation of concretionary carbonates significantly depleted in 13c the concretions consist of rectangularly orientated rod to dumbbell shaped crystal aggregates made of fibrous high mg calcite the sulphate reducing bacteria exhibit intracellular storage inclusions and magnetosomes with greigite fe3s4 indicating that iron cycling is involved in the metabolism of the microbial population transfer of fe3 into the cells is apparently mediated by abundant extracellular vesicles resembling known bacterial siderophore vesicles marinobactine in size 20 to 100 nm and structure

microenvironmental constraint on δ13c depletion garudamangalam sandstone cauvery basin india ss acknowledges the centre of advance study cas phase v and university with potential for excellence upe ii programmes of jadavpur university geochemical work was carried out at the national stable isotope facility of iit kharagpur and iiser kolkata

geological and hydraulic characterisation of the excavation disturbed zone in the opalinus clay of the mont terri rock laboratory abstract the fracture network in the excavation disturbed zone edz of an argillaceous formation the opalinus clay in the mont terri rock laboratory in northwest switzerland is characterised using structural and hydrogeological techniques sampling of unloading fractures is done by analysing resin injected overcores taken from the edz resulting in a structural data set of fracture orientations frequencies and extent of the edz these parameters are derived in tunnel sections which were excavated by blasting pneumatic hammering and road header techniques pneumatic and hydrogeological tests are subsequently carried out to derive hydraulic parameters such as permeability and transmissivity distributions of the fracture network synthesis of the structural and hydrogeological data led to a conceptual model of the edz in the mont terri rock laboratory which is defined by a 2 m plastically deformed zone around the tunnel this plastic zone is further divided into an inner 1 m zone consisting of an air filled fracture network and an outer zone with mostly saturated and isolated fractures transmissivities in the inner zone are orders of magnitude higher than those of the undisturbed opalinus clay finally a methodology is proposed for the structural and hydrogeological characterisation of the edz this methodology is not site specific and is thus applicable at any argillaceous underground facility

synthesis and model of formation water flow alberta basin canada based on a large amount of publicly available data several studies have previously examined the flow of formation waters in different parts of the alberta basin offering various interpretations as to the causes of the observed pressure regime and flow pattern however there has been no synthesis of these diverse studies on a basin wide basis accordingly these studies are critically reviewed in this paper and synthesized in a new basin scale model of the flow of formation waters in the alberta basin the proposed regional scale model has significant implications for understanding hydrocarbon migration pathways ore genesis the geothermal regime and deep waste disposal in the alberta basin several flow systems each one driven by a different mechanism are identified together with the main processes leading to the nonhydrostatic pressures observed in the basin two megahydrostratigraphic successions and associated flow systems are recognized the first succession corresponds to the pre cretaceous passive margin stage of basin development and consists of thick carbonate dominated aquifer systems separated by shaly aquitards and evaporitic aquicludes a northeastward basin scale flow system is driven by basin topography with recharge in montana and discharge in northeastern alberta southwest to northeast regional scale flow adjacent to the fold and thrust belt is probably the result of past tectonic processes the salinity of formation water in pre cretaceous aquifers is high and generally increases both northward and with depth this variability is the result of increased water rock reactions mineral solubility with increased temperatu e and of incomplete flushing by meteoric water as a result of salinity variations flow retarding buoyancy effects can be important the second megahydrostratigraphic succession corresponds to the post jurassic foreland stage of basin evolution and consists of thick shaly aquitard systems and relatively thin sandstone aquifers in the southwestern part of the basin flow in isolated aquifers is driven southwestward by erosional rebound in the thick intervening shales downdip toward the fold and thrust belt the salinity of formation waters in the post jurassic aquifers is low mixing of waters and interference between the major flow systems takes place along the pre cretaceous unconformity where successively older pre cretaceous aquifers subcrop from west to east flow in shallow lo al systems at the top of the sedimentary succession is driven by local topography

analysis and interpretation of borehole hydraulic tests in deep boreholes principles model development and applications a review of the literature on hydraulic testing and interpretive methods particularly in low permeability media indicates a need for a comprehensive hydraulic testing interpretive capability physical limitations on boreholes such as caving and erosion during continued drilling as well as the high costs associated with deep hole rigs and testing equipment often necessitate testing under nonideal conditions with respect to antecedent pressures and temperatures in these situations which are common in the high level nuclear waste programs throughout the world the interpretive requirements include the ability to quantitatively account for thermally induced pressure responses and borehole pressure history resulting in a time dependent pressure profile around the borehole as well as equipment compliance effects in low permeability intervals a numerical model was developed to provide the capability to handle these antecedent conditions sensitivity studies and practical applications are provided to illustrate the importance of thermal effects and antecedent pressure history it is demonstrated theoretically and with examples from the swiss nationale genossenschaft fur die lagerung radioaktiver abfalle regional hydrogeologic characterization program that pressure changes expressed as hydraulic head of the order of tens to hundreds of meters can result from 1 to 2 c temperature variations during shut in packer isolated tests in low permeability formations misinterpreted formation pressures and hydraulic conductivity can also result from inaccurate antecedent pressure history interpretation of representative formation properties and pressures requires that antecedent pressure information and test period temperature data be included as an integral part of the hydraulic test analyses

fractal dimension lacunarity and succolarity analyses on ct images of reservoir rocks for permeability prediction abstract an explicit relationship between seepage properties and microscopic structure of porous media is being sought for the development of oil and gas resources an effective method to accurately characterize and quantify the microscopic structure of porous media is a key issue fractal geometry can take advantage of several physically based parameters to analyze microstructures of reservoir rocks in this study three fractal structural parameters fractal dimension lacunarity and succolarity were employed to characterize scale invariant complexity heterogeneity and anisotropy of rock microstructures respectively twelve three dimensional digital cores of sandstone reservoir rocks were used to evaluate permeability in terms of fractal dimension lacunarity and succolarity the parameters were utilized to quantitatively characterize differences in core micro structure and predict their effects on permeability due to the confounding influence of porosity the fractal dimension was not an accurate predictor of the variation in permeability on its own instead the results reveal that lacunarity and succolarity were better able to predict differences in structure and permeability succolarity in particular showed an exponential relationship with permeability yielding a coefficient of determination of 0 940 using a combination of fractal structural parameters in the place of pore size distribution can provide a better explanation of the relationship between fluid flow and the heterogeneous structure and anisotropic physical properties of reservoir rocks

flow of variable density formation water in deep sloping aquifers review of methods of representation with case studies abstract distributions of freshwater hydraulic heads have been and continue to be used in the representation and analysis of groundwater flow including the flow of variable properties formation water in deep sloping aquifers because of variations in pressure temperature and salinity the flow of formation waters in sedimentary basins is driven by potential forces resulting from pressure and elevation topography differences by buoyancy resulting from density differences and by osmosis caused by temperature and concentration gradients because of variations in both fluid and rock properties it is not possible to define a flow potential to be used in representing and analysing the flow neither is there a force potential from which a flow driving force can be derived and which could be used in flow representation and analysis even if osmotic effects are neglected buoyancy still plays a role which in certain cases may be important in horizontal or near horizontal aquifers the lateral flow of variable density water is correctly represented by freshwater potentiometric surfaces and the vertical flow may be analysed using environmental hydraulic head distributions however the flow of formation waters in sedimentary basins is mostly along bedding in confined sloping aquifers in this case short of calculating and representing either the velocity or the impelling force distribution freshwater hydraulic heads remain the only tool available for representing and analysing the flow by neglecting buoyancy errors in flow strength and direction are introduced which become significant if a dimensionless driving force ratio exceeds a threshold value estimated to be around 0 5 the review of representation and analysis methods for the flow of variable properties formation water in deep sloping aquifers is illustrated with two case studies from the alberta and llanos sedimentary basins

salinization problems in the negb results from thermohaline simulations the occurrence of salty waters close to the surface is a well known problem in the north east german basin previous numerical simulations showed that near surface brine occurrences are due to the interaction of hydrostatic and thermally induced forces mixed convection the influence of hydraulic permeabilities and thermal conductivities on the observed patterns remained an open question based on a hydro geochemical dataset thermohaline simulations are carried out in order to quantify the impact of these physical parameters on brine migration the results indicate that the salinity and temperature profiles are strongly controlled by hydraulic permeabilities and can locally be influenced by thermal conductivities

geohydromechanical processes in the excavation damaged zone in crystalline rock rock salt and indurated and plastic clays in the context of radioactive waste disposal abstract the creation of an excavation disturbed zone edz or excavation damaged zone edz is expected around all man made openings in geologic formations macro and micro fracturing and in general a redistribution of in situ stresses and rearrangement of rock structures will occur in this zone resulting in drastic changes of permeability to flow mainly through the fractures and cracks induced by excavation the edz may have significant implications for the operation and long term performance of an underground nuclear waste repository various issues of concern need to be evaluated such as processes creating fractures in the edz the degree of permeability increase and the potential for sealing or healing with permeability reduction in the zone in recent years efforts along these lines have been made for a potential repository in four rock types crystalline rock salt indurated clay and plastic clay and these efforts have involved field laboratory and theoretical studies the present work involves a synthesis of the ideas and issues that emerged from presentations and discussions on edz in these four rock types at a cluster conference and workshop held in luxembourg in november 2003 first definitions of excavation disturbed and edzs that may be applicable to all four rock types are proposed then an approach is suggested for the synthesis and intercomparison of geohydromechanical processes in the edz for crystalline rock salt indurated clay and plastic clay comparison tables of relevant processes associated factors and modelling and testing techniques are developed a discussion of the general state of the art and outstanding issues is also presented a substantial bibliography of relevant papers on the subject is supplied at the end of the paper

impact of heterogeneous permeability distribution on the groundwater flow systems of a small sedimentary basin summary ground water flow systems of shallow sedimentary basins are studied in general by analyzing the fluid dynamics at the real world example of the thuringian basin the impact of the permeability distribution and density differences on the flow velocity pattern the salt concentration and the temperature distribution is quantified by means of transient coupled simulations of fluid flow heat and mass transport processes simulations are performed with different permeabilities in the sedimentary layering and heterogeneous permeability distributions as well as with a non constant fluid density three characteristic numbers are useful to describe the effects of permeability on the development of flow systems and subsurface transport the relation of permeability between aquiclude and aquifer the variance and the correlation length of the log normal permeability distribution density dependent flow due to temperature or concentration gradients is of minor importance for the distribution of the flow systems but can lead to increased mixing dissolution of salt thermal convection is in general not present the dominant driver of groundwater flow is the topography in combination with the permeability distribution the results obtained for the thuringian basin give general insights into the dynamics of a small sedimentary basin due to the representative character of the basin structure as well as the transferability of the settings to other small sedimentary basins

the distribution of methane in the upper waters of the southern california bight profiles of dissolved methane in the upper 300 m of a 190 000 km2 area of southern californian waters were determined during november 1989 and march 1990 methane in near surface waters ranged from 1 to 1416 nmol l 1 the lowest concentrations were at depths 200 m the highest levels were found along the coast especially in the region extending from point conception to santa barbara vertical profiles of methane are characterized by maxima in supersaturation within a narrow density band located within the pycnocline this layer is continuous over a large geographic area offshore stations exhibiting elevated levels of methane are spatially coincident with mesoscale eddies of the california current system interpretation of hydrographic and chemical data suggests that ch4 rich waters are upwelled from relatively shallow areas that are characterized by numerous hydrocarbon seeps the data are consistent with a nearshore source of methane presumably submarine seeps subsurface maxima in offshore waters are likely maintained by lateral transport of allochthonous ch4 along density surfaces from coastal waters and autochthonous microbial production

numerical analysis of the groundwater regime in the western dead sea escarpment israel west bank water is scarce in the semi arid to arid regions around the dead sea where water supply mostly relies on restricted groundwater resources due to increasing population in this region the regional aquifer system is exposed to additional stress this results in the continuous decrease in water level of the adjacent dead sea the interaction of an increasing demand for water due to population growth and the decrease of groundwater resources will intensify in the near future thus the water supply situation could worsen significantly unless sustainable water resource management is conducted in this study we develop a regional groundwater flow model of the eastern and southern judea group aquifer to investigate the groundwater regime in the western dead sea drainage basin of israel and the west bank an extensive geological database was developed and consequently a high resolution structural model was derived this structural model was the basis for various groundwater flow scenarios the objective was to capture the spatial heterogeneity of the aquifer system and to apply these results to the southern part of the study area which has not been studied in detail until now as a result we analyzed quantitatively the flow regime the groundwater mass balance and the hydraulic characteristics hydraulic conductivity and hydraulic head of the cretaceous aquifer system and calibrated them with pest the calibrated groundwater flow model can be used for integrated groundwater water management purposes in the dead sea area especially within the framework of the sumar project

anaerobic methane oxidation in low organic content methane seep sediments abstract sulfate dependent anaerobic oxidation of methane aom is the key sedimentary microbial process limiting methane emissions from marine sediments and methane seeps in this study we investigate how the presence of low organic content sediment influences the capacity and efficiency of aom at bullseye vent a gas hydrate bearing cold seep offshore of vancouver island canada the upper 8 m of sediment contains

the finne fault zone central germany structural analysis of a partially inverted extensional fault zone by balanced cross sections the finne fault zone located in central germany to the southwest of the harz mountains was studied by means of detailed map analysis investigations of fault displacement and balanced cross sections for the most strongly deformed area in the center of the fault zone ca 50 of total fault zone length the system of the finne fault zone shows a nearly 100 km long straight flexure that symbolizes the morphological and geological northeastern border of the thuringian basin in the central part which should be surveyed here the fault zone corresponds to a distinctive narrow band of highly deformed triassic sedimentary rocks the northwestern and especially the southeastern parts of the research area are developed as several parallel branch faults in the southeastern elongation of the fault zone which is not part of our survey the sedimentary cover is missing here it is possible to gain insight to the fact that the basement is also involved to the kinematics of the fault zone based on our results we propose a subdivision of the fault zone into four sectors from the northwest to the southeast we interpret the structure of these sectors to reflect 1 a compressional flexure 2 an overthrust graben and 3 a partially inverted and folded half graben in the extreme southeast 4 the fault zone is characterized by an anticline with some strike slip movement parallel to the fold axis this segmentation is caused by a thrust fault system whose strike direction deviates slightly from that of the earlier formed graben system the structural configuration can be explained by a two phase deformation in which the contractional strain exceeded the preceding extensional deformation in the investigated area the horizontal shortening attains a maximum of ca 1 km the present study confirms many earlier hypotheses presents new results on the deformation history of the fault zone and attempts to evaluate the deformation in a regional geological context the results of earlier studies were refined and revised using modern methods and a unified structural and kinematic model of the finne fault zone was created

sequence surfaces and paleobathymetric trends in albian to maastrichtian sediments of ariyalur area cauvery basin india abstract exposed late cretaceous albian maastrichtian marine rocks of the ariyalur area in the cauvery basin have been extensively studied based on biostratigraphy and paleobathymetry with paleobathymetric interpretation carried out using vertical and lateral relationships of rock facies macro and microfossil assemblages textural characteristics and diagenetic changes of the lithologic units the integration of these data reveals four transgressive regressive t r cycles viz dalmiapuram garudamangalam sillakkudi and kallankurichchi in stratigraphic order these t r cycles have been compared with global published relative sea level curves of the study area the major sea level changes during the late turonian and late maastrichtian in the study area correlate well with global sea level changes of vail et al 1977 haq et al 1987 and miller et al 2005 based on biostratigraphy stratal patterns and their relationship the late cretaceous succession of the ariyalur area is thus subdivided into four 2nd 3rd order sequences

fluid dynamics driving saline water in the north east german basin in several areas of the north german basin saline water comes close to or even reaches the surface available data from wells indicate that brine stratification is under unstable conditions in the deeper underground in order to analyse the possible transport mechanisms 3d thermohaline simulations have been carried out for two different scenarios the 3d regional model 230 330 km indicates that salty water is driven to the surface by hydrostatical forces from the surrounding highlands in addition a smaller scale model 10 10 km has been constructed with a grid resolution accounting for possible convective flow the results indicate that convective flow may play a dominant role in areas with minor topography in summary the complex pattern of near surface occurrences of saline water probably results from the interaction of hydrostatic and thermal forces

homogenization and effective parameters for the henry problem in heterogeneous formations 1 general upscaling of density dependent flow is investigated for the classical two dimensional henry problem of saltwater intrusion in coastal aquifers combined theoretical and numerical results are here presented effective flow and transport parameters for saline intrusions could be derived for statistically isotropic and anisotropic heterogeneous permeability fields by use of homogenization theory applying also to the preasymptotic regime our numerical results indicate that heterogeneities in permeability affect foremost the transient evolution of saltwater intrusion whereas the steady state saltwater distribution is less sensitive to spatially varying permeabilities and longitudinal dispersion for the isotropic media the effective permeability is found to correspond to the geometric mean as under conditions without fluid density contrast the extension of results to anisotropic media requires nontrivial corrections for the effective permeability which include the variance of log k and the directional correlation lengths the appropriate dispersion coefficients for the problem correspond to the local dispersion coefficients rather than macrodispersion coefficients these results are discussed in light of the specific flow configuration posed in the henry problem

concepts for the sustainable management of multi scale flow systems the groundwater system within the laufen basin switzerland many groundwater systems consist of multi scale aquifer units the exchange processes and rates between these aquifer units are complex in order to manage such complex systems a subdivision into different catchments sub catchments or groundwater bodies as manageable units is required the sustainable management of water resources requires a comprehensive view of water quality and water quantity aspects not only for water supply issues but generally also for flood protection and riverine ecosystem functions such transformations require an improved understanding of recharge and exchange processes between different aquifer units as well as aquifer surface water interaction processes at different spatiotemporal scales the main objective of this study is to illustrate concepts by defining the geometry and scales of different aquifer units within a sedimentary basin the laufen basin in the jura mountains represents a sub catchment of the river birs switzerland its structure is characterized by a pronounced local relief and a series of aquifer units which are typical for many complex groundwater systems in front of mountain chains such as the alpine foreland and the jura mountains of central europe a combination of different concepts is required to understand multi scale flow systems and to describe the various hydrogeological processes three concepts are proposed for the laufen basin including 1 a regional flow system analysis based on the concept of hierarchical groundwater flow systems 2 the river corridor concept for understanding aquifer surface water interaction processes and 3 the calculation of the dynamic vulnerability index and the aquifer base gradient approach for karst flow and fractured flow systems

characterization of main heat transport processes in the northeast german basin constraints from 3 d numerical models to investigate and quantify main physical heat driving processes affecting the present day subsurface thermal field we study a complex geological setting the northeast german basin negb the internal geological structure of the negb is characterized by the presence of a relatively thick layer of permian zechstein salt up to 5000 m which forms many salt diapirs and pillows locally reaching nearly the surface by means of three dimensional numerical simulations we explore the role of heat conduction pressure and density driven groundwater flow as well as fluid viscosity related effects our results suggest that the regional temperature distribution within the basin results from interactions between regional pressure forces as driven by topographic gradients and thermal diffusion locally enhanced by thermal conductivity contrasts between the different sedimentary rocks with the highly conductive salt playing a prominent role in contrast buoyancy forces triggered by temperature dependent fluid density variations are demonstrated to affect only locally the internal thermal configuration locations geometry and wavelengths of convective thermal anomalies are mainly controlled by the permeability field and thickness values of the respective geological layers

excavation induced damage studies at the underground research laboratory the underground research laboratory url is situated in the lac du bonnet granite batholith in southeastern manitoba canada the url was developed to study issues related to the deep geologic disposal of used fuel from nuclear reactors and has developed into an international atomic energy agency recognized geotechnical center of excellence extensive rock mechanics research has been conducted including work to understand the character and extent of excavation damage experience at the url has shown that damage exists around underground openings and that the damage develops from the energy imparted to the rock by the excavation method and by redistribution of the in situ stress field around the excavated openings subsequent near by excavations removal of loose material from the existing tunnel thermal loads and pore pressure changes will all influence the development and extent of rock damage as does the rock type and its fabric studies at the url have shown that in highly stressed rock damage will develop around underground openings even when a low energy excavation method is used and that properly designing the excavation geometry and orientation plays a major role in constructing stable openings two zones of excavation affected rock have been shown to exist from studies at the url 1 a zone of irreversibly damaged rock surrounding the excavation which may include failed zones inner and outer damage zones and 2 a zone of excavation disturbance where the in situ stresses are influence by the excavation no damage is measurable measurements of the properties of the damaged rock ultrasonic velocity transmissivity using a variety of instruments have shown that a less intensively damaged outer zone surrounds a more highly damaged inner zone the inner damage zone may have zones of failed rock depending on stress concentrations relative to rock strength and damage imparted by excavation method the inner damage zone is attributed to the effects of the excavation method and stress redistribution and the outer damage zone is attributed to the effects of stress redistribution alone in lower stressed rock the extent of the outer zone is much less than for an opening in highly stressed rock with the same excavation shape and orientation relative to in situ stresses the excavation disturbed zone describes the volume of rock surrounding the damage zone where the stress redistribution is too small to permanently change rock properties unless some other stress increase such as thermal loading is added and it is also characterized non permanent but potentially long term changes in hydraulic head

quantitative characterization of the excavation damaged zone fracture network in the meuse haute marne underground research laboratory in situ experiment and numerical interpretation of helium injection test