dimensional threshold for fracture linkage and hooking fracture connectivity in rocks depends on spatial properties of the pattern including length abundance and orientation when fractures form a single strike set they hardly cross cut each other and the connectivity is limited linkage probability increases with increasing fracture abundance and length as small fractures connect to each other to form longer ones a process for parallel fracture linkage is the hooking where two converging fracture tips mutually deviate and then converge to connect due to the interaction of their crack tip stresses quantifying the processes and conditions for fracture linkage in single strike fracture sets is crucial to better predicting fluid flow in naturally fractured reservoirs for 1734 fractures in permian shales of the lodeve basin se france we measured geometrical parameters in 2d characterizing three stages of the hooking process underlapping overlapping and linkage we deciphered the threshold values shape ratios and limiting conditions to switch from one stage to another one the hook set up depends on the spacing s and fracture length lh with the relation s 0 15 lh once the hooking is initiated with the fracture deviation length l l 0 4 lh the fractures reaches the linkage stage only when the spacing is reduced to s 0 02 lh and the convergence c is 0 1 l these conditions apply to multi scale fractures with a shape ratio l s 10 and for fracture curvature of 10 20

the southern border of baltica a review of the present state of knowledge abstract the southern border of baltica was for many years drawn along the nw part of the tornquist zone this important boundary between segments of the pre cadomian east european and the palaeozoic west european platforms is now redefined on the basis of geophysical and well data most probably it runs south of the ringkobing fyn high in denmark the transects bornholm rugen and scania holstein are used to discuss its position and tectonic character two main interpretations are possible in model 1 the boundary coincides with a steep fracture zone the jylland mon fault that forms the northern front of the caledonian folded lower palaeozoic in the southern forefield of baltica because of significant differences in the tectonical lithological and thickness development on both sides of this fault it is interpreted as the northern boundary of a caledonian terrane rugen pomorze terrane accreted to and locally overthrusted onto baltica at early devonian times the south adjoining area between this terrane and the northern front of the mid european variscides is thought to represent a mosaic of predominantly cadomian terranes probably with intervening caledonian folded complexes this mosaic of terranes is assumed to have been amalgamated to a north german superterrane during late caledonian diastrophism at the latest in model 2 the boundary is 50 km south of the caledonian front it coincides with the buried trans european fault that has been documented by deep seismic sounding in this model the caledonian deformed complexes south of the ringkobing fyn high are interpreted as nappe structures of a lower palaeozoic marginal belt thrusted onto the southern edge of baltica hence it follows that the area to the north of the mid european variscides is most probably built up of the internal parts of a north german polish caledonide orogen

the origin of the kupferschiefer type mineralization in the richelsdorf hills germany as deduced from stable isotope and organic geochemical studies abstract the kupferschiefer horizon in the richelsdorf section federal republic of germany acted as a geochemical trap by accumulating metals from ascending brines chemical composition of the extracted bitumens reflects a drastic change in the degree of oxidation of the organic matter towards rote faule this alteration pattern corresponds with regular changes in the isotopic composition of organic carbon and carbonate as well as with the base metal zonation around rote faule the enrichment of the organic material in 13c suggests the preferential release of isotopically light hydrogen equivalents through progressive degradation and oxidation of organic matter the opposite tendency towards lower 13c and 18o values of carbonate minerals provides evidence for isotopic reequilibration between carbonate and isotopically light oxidizing solutions the occurrence of isotopically heavy organic carbon together with low 13c and 18o values of carbonate suggests that 12c rich co2 generated due to oxidation of organic material may have been a source of carbonate the results reveal a post sedimentary formation of high grade mineralization and associated rote faule by ascending oxidizing brines they are in agreement with the results of mineralogical and geochemical studies which provided evidence for metal precipitation from basinal brines enriched in na and sulphate s the organic geochemical and isotopic data suggest that metal precipitation was caused by thermochemical sulphate reduction with organic matter acting as a reducing agent and proton donor

scaling and connectivity of joint systems in sandstones from western norway abstract the scaling properties of a joint system in devonian sandstones in western norway have been investigated using seven maps covering areas from 18 to 720 m across which were generated by mapping in the field and from low level aerial photography taken from different heights each map represent a scale window on the fracture population bounded by resolution at small scales and the sample size at large scales a power law relationship between fracture trace length and critical observation height maximum height at which a trace can be identified is derived and used to create a statistical model for the resolution effects the model indicates that a continuous smooth curve without a straight line segment on a log log cumulative frequency distribution plot does not necessarily rule out a power law as the underlying population distribution together the maps indicate a powerlaw trace length distribution with an exponent of 2 1 this power law may be valid over four or more orders of magnitude with natural lower cut off of around 1 m the exponent is significantly different from 2 0 strictly selfsimilar case and is reflected in a decrease in the abundance of fractures with length comparable to map size as map scale decreases the fracture trace length distribution results in a decrease in apparent connectivity with decreasing scale high resolution large scale maps are well connected while the lowest resolution map smallest scale is unconnected fractures in the smallest scale map are however connected by small fractures below the limit of resolution represented by the largest scale map the variation in apparent connectivity with scale has implications for fluid flow when fractures are open to fluid flow the scaling properties of apparent connectivity imply that beyond a certain scale the size of fracture controlling flow will be scale independent in this fracture system this appears to occur in sample areas of around 300 m across

connectivity permeability and channeling in randomly distributed and kinematically defined discrete fracture network models a major use of dfn models for industrial applications is to evaluate permeability and flow structure in hardrock aquifers from geological observations of fracture networks the relationship between the statistical fracture density distributions and permeability has been extensively studied but there has been little interest in the spatial structure of dfn models which is generally assumed to be spatially random i e poisson in this paper we compare the predictions of poisson dfns to new dfn models where fractures result from a growth process defined by simplified kinematic rules for nucleation growth and fracture arrest davy et al 2010 2013 this so called kinematic fracture model is characterized by a large proportion of t intersections and a smaller number of intersections per fracture several kinematic models were tested and compared with poisson dfn models with the same density length and orientation distributions connectivity permeability and flow distribution were calculated for 3d networks with a self similar power law fracture length distribution for the same statistical properties in orientation and density the permeability is systematically and significantly smaller by a factor of 1 5 to 10 for kinematic than for poisson models in both cases the permeability is well described by a linear relationship with the areal density p32 but the threshold of kinematic models is 50 larger than of poisson models flow channeling is also enhanced in kinematic dfn models this analysis demonstrates the importance of choosing an appropriate dfn organization for predicting flow properties from fracture network parameters

a two dimensional seismic velocity model across the transition zone between the baltic shield and the north german basin the eugeno s profile 1 revisited abstract a new p wave velocity model is derived from wide angle data collected in 1984 and 1986 during the european geotraverse egt projects eugeno s and eugemi the data have been thoroughly reinterpreted and modelled with a travel time inversion algorithm we have used model grid nodes approximately every 25 km horizontally with a resulting model that is smoother than previously derived models despite the lack of fine details in the model we clearly image the thickness of the crystalline crust which varies between 25 and 45 km along the 600 km long profile we present the final model together with the velocity parameter resolution which demonstrates more clearly than in previous studies which parts of the model are well constrained by the available data we interpret the crystalline crust below the sediments of the rinkobing fyn high and the norwegian danish basin to be of sveconorwegian type a continuation of the baltic shield southwest of the sorgenfrei tornquist zone a tectonic lineament previously thought of as the boundary between the precambrian and palaeozoic europe the crust is some 10 15 km thinner here than in the shield proper and in our seismic model we find evidence that the crustal thinning occurs almost entirely in the lower crust p wave velocities between 6 5 7 0 km s the observed crustal structure shows clear signs of extension estimated to be at least 20 along the profile

simulation of groundwater flow in fractured rocks using a coupled model based on the method of domain decomposition groundwater flow in fractured rocks is modeled using a coupled model based on the domain decomposition method in the model the fractured porous medium is divided into two non overlapping sub domains one is the rock matrix in which the medium is described using a continuum model the other consists of deep fractures and fissure zones where the medium is described using a discrete fracture network dfn model the two models are coupled through the continuity of the hydraulic heads and fluxes on the common boundaries the coupled model is used to simulate groundwater flow in a hydropower station the results show that the model simulates groundwater levels that are in agreement with the measured groundwater levels furthermore the model s parameters relating to deep fractures and fissure zones are verified by comparing three different models the continuum model coupled model and dfn model the results show that the coupled model can capture and duplicate the hydrogeological conditions in the study domain whereas the continuum model overestimates and the dfn model underestimates the measured hydraulic heads a sensitivity analysis shows that fracture aperture has a considerable effect on the groundwater level so when the fracture aperture is large the coupled model or dfn model is more appropriate than the continuum model in the fracture domain

palaeomagnetism magnetic fabrics and the structural style of the hornelen old red sandstone western norway the old red sandstone of the hornelen district western norway forms part of a major fold terrane and the principal magnetization is associated with the late devonian to early carboniferous svalbardian solundian orogeny the present fault margins of the hornelen massif claimed by various authors to represent subordinate devonian splay faults associated with megashearing in the north atlantic or lateral ramps in a regional extensional tectonic setting are shown to be post devonian structures and the present outline of the hornelen massif is a mesozoic jurassic graben

inter well scale natural fracture geometry and permeability variations in low deformation carbonate rocks regional natural fracture networks often show variations on a scale below that captured by seismic reflection data this variability is not considered in most reservoir models but likely impacts uncertainties in permeability we quantify this uncertainty using a database of 13 000 fractures in nine outcrops digitised in the carbonate jandaira formation potiguar basin brazil distance between outcrops is on average 11 km with a minimum of 300 m which is comparable to the distance between wells in naturally fractured reservoirs in between outcrops significant variations exist in orientation intensity length and topology using discrete fracture matrix flow models we model the permeability of each deterministic pattern and find that small changes in geometry and topology result in permeability variations that are not captured by connectivity based analyses such as percolation probabilities particularly when the matrix is permeable the permeability variations associated with subseismic scale fracture variability are not captured in conventional stochastic models but can be captured using deterministic outcrop models with flow through discrete fractures the deterministic models provide a permeability range associated with subseismic fracture variability that can be assigned to grid cells of fractured reservoir flow models as an alternative to assuming constant permeability in the absence of subseismic scale deformation

improved statistical multi scale analysis of fractured reservoir analogues abstract this paper includes the results of the application of novel methodologies for the statistical analysis of tensile fracture attributes spacing density and aperture the statistical methods have been applied to a fractured lower cretaceous carbonate succession cropping out in the sorrento peninsula naples area italy representing a geological analogue of buried reservoirs of southern apennines major oil fields as fracture networks observable from outcrop to the crystal scale can significantly affect the hydraulic behavior of a fractured reservoir the definition of appropriate models of fracture spacing and aperture probability distribution at various scales represents an important goal of structural analysis in order to achieve such an objective sampling has been carried out at different scales by means of traditional scan lines at outcrop as well as micro scan lines carried out both by a digital micro camera 50 and by the optical microscope 200 fracture spacing and density analysis are mainly aimed at establishing the characteristics of joint spatial distribution over a range of scales aperture analysis is aimed at verifying that the aperture cumulative frequency is described by a power law and in the latter instance to provide an effective method for a more precise determination of the exponent of the power law finally new expressions are provided in closed form in order to calculate the confidence interval of the power law exponent the proposed criteria provide handy and effective methods for a significantly improved statistical analysis of fracture attributes

the evolution of the hornelen basin detachment system western norway implications for the style of late orogenic extension in the southern scandinavian caledonides abstract the geology of the devonian hornelen basin and the surrounding western gneiss region wgr western norway has been examined in detail structural clast provenance and geothermobarometric data have been combined to reconstruct the motion history of part of a major late orogenic extensional shear zone in the southern scandinavian caledonides the nordfjord sogn detachment nsd the nsd in the hornelen basin area is a zone of mylonites 4 6 km thick tectonostratigraphically constrained within the lower and middle allochthons lma and the uppermost part of the wgr it separates eclogite bearing gneisses of the wgr from greenschist and amphibolite facies rocks of the middle and upper allochthons marking a profound metamorphic break and indicating major excision of crustal section kinematic indicators give a consistent top to the west shear sense indicating a reversal of the movement sense of the scandian nappes with the ductile strain being distributed through the entire lma section the wgr was exhumed from depths of up to 100 km in the footwall of the shear zone partly aided by pure shear vertical flattening below the nsd and extension and erosion of the hanging wall the majority of the movements on the nsd in the hornelen basin area occurred under amphibolite facies conditions prior to 410 ma subsequent shear caused limited greenschist retrogression along extensional crenulation cleavages depending on interpretation of mica 40 ar 39 ar ages this lower grade shearing may be due to a continuation of movements or renewal of motion associated with opening of the hornelen basin at about 385 ma the lack of clear evidence of penetrative greenschist facies mylonites in the hornelen area may be due to the faulted omission of tectonites of this grade following scandian a subduction and eclogite facies metamorphism at 425 ma the p t t path of the wgr shows very rapid decompression associated with early slip on the extensional detachment horizons unroofing was initially near isothermal followed by a phase of rapid near isobaric cooling after 410 ma decompression and cooling slowed as slip on the nsd slowed or even ceased by the middle devonian the wgr lay at about 10 15 km depth and the crust had almost returned to isostatic equilibrium at this time a brittle fault splaying from the nsd ramped upwards through the upper allochthon opening a scoop shaped west facing half graben the hornelen basin a further 50 km of heave on the nsd occurred during alluvial infilling of the basin subsequently the basin fill was folded by late devonian n s compression and the basin margins were modified by mesozoic faulting these features are consistent with an orogenic collapse model for southern scandinavia that involves large scale backsliding of the scandinavian caledonides within tectonostratigraphic units by this mechanism the baltic shield could have been efficiently unloaded with tectonic translations producing significant metamorphic breaks within a seemingly preserved tectonostratigraphic sequence the model favours orogenic collapse driven by an external pull rather than internal body forces

the trans european fault a critical reassessment abstract new deep seismic pro les in the southern baltic region have failed to image the trans european fault evidence for this structure of suggested pre cadomian age is critically re examined localized geophysical anomalies are present but these cannot be correlated with known structuralfeatures of the region based on the inconclusive evidence for this structure we would therefore pro pose that the term trans european fault should not be used in the future and that to avoid confu sion authors use local names for local structures author for correspondence tmc gfz potsdam de stzcdftefdanishbasinrfh eugemi aelnorthgermanmassif nizu sebasin 9601pq2 9 1 4 13 25 berthelsen 1984eugeno s working group 1988horst flueh borngen 1994krauss 1994franke 1993 0 100 km 12345 i pq2 9pq2 9 3 3 loss 1 70h2 1 90k5 1 88g14 1 86pud 1 86rn 2 67gst 1 73rn 4 64 r u g enusedom 0 30 km figure 1 map showing the main structural features and thelocations of the deep seismic surveys in the region the vari ous trends of the trans european fault are also indicated 1 pozarski brochwicz lewinski tomczyk 1982 buttermed caledonian deformation front berthelsen 1984 babel working group 1993 mona lisa workinggroup 1997 2 eugeno s working group 1988 3 horst flueh borngen 1994 4 krauss 1994 5 franke 1993 inset map shows the locations of wells mentioned inthe text key cdf caledonian deformation front el elbe lineament rfh ringkobing fyn high stz sorgenfrei tornquist zone tef trans european fault

tomographic p wave velocity and vertical velocity gradient structure across the geothermal site gros schonebeck ne german basin relationship to lithology salt tectonics and thermal regime 1 seismic wide angle data were collected along a 40 km long profile centered at the geothermal research well grsk 3 90 in the northeast german basin tomographic inversion of travel time data provided a velocity and a vertical velocity gradient model indicative of cenozoic to pre permian sediments wide angle reflections are modeled and interpreted as top zechstein and top pre permian changes in velocity gradients are interpreted as the transition from mechanical to chemical compaction at 2 3 km depth and localized salt structures are imaged suggesting a previously unknown salt pillow in the southern part of the seismic profile the zechstein salt shows decreased velocities in the adjacent salt pillows compared to the salt lows which is confirmed by sonic log data this decrease in velocity could be explained by the mobilization of less dense salt which moved and formed the salt pillows whereas the denser salt remained in place at the salt lows we interpret a narrow subvertical low velocity zone under the salt pillow at grsk 3 90 as a fault in the deep permian to pre permian this wnw ese trending fault influenced the location of the salt tectonics and led to the formation of a fault bounded graben in the rotliegend sandstones with optimal mechanical conditions for geothermal production thermal modeling showed that salt pillows are related to chimney effects a decrease in temperature and increasing velocity the assumed variations in salt lithology density and strain must thus be even higher to compensate for the temperature effect

petroleum surface oil seeps from a palaeoproterozoic petrified giant oilfield early palaeoproterozoic rocks from the onega basin in russian fennoscandia contain evidence for substantial accumulation and preservation of organic matter up to 75 wt total organic carbon with an estimated original petroleum potential comparable to a modern supergiant oilfield the basin contains a uniquely preserved petrified oilfield including evidence of oil traps and oil migration pathways here we report the discovery of the surface expression of a migration pathway along which petroleum was flowing from the sub surface this surface oil seep the first occurrence ever reported from the palaeoproterozoic appears as original bitumen clasts redeposited in palaeoproterozoic lacustrine turbidites the 13corg of clastic pyrobitumen ranges between 35 4 and 36 0 n 14 which is within the range of interbed and vein trapped fossil oil 46 and 24 suggesting similar source biogenic organic matter whose isotopic composition was modified during thermal maturation is the likely source for the migrated hydrocarbon

scaling of fault displacements from the badajoz cordoba shear zone sw spain faulting occurs over a large range of scale parts of which are sampled by various techniques e g microscopy outcrop measurement mapping seismic reflection and other forms of remote sensing use of a single technique to measure displacement or strain will not sample faults at all scales and hence will give a biased estimate in order to assess this bias a knowledge of the distribution over all scales is needed many samples of fault displacement appear to follow a power law distribution with departures which can be attributed to sampling effects the number of faults with a displacement u is given by n u cu d the power law distribution of displacement is consistent with similar distributions of other fault parameters and earthquake magnitudes when sampling along a line e g a bedding trace on a map or section a self similar fault population would have d 1 whereas self affine geometries yield d 1 displacement and extension are dominated by small faults when d 1 and by large faults when d 1 when sampling over areas or volumes these critical values are 2 and 3 respectively a set of strike slip faults from the badajoz cordoba shear zone spain were sampled at two different scales using 1 50000 maps and outcrop measurements displacement ranges over 6 orders of magnitude these and other fault populations typically have d ranging from 0 6 to 1 5 the power law relationship may be integrated to yield estimates of the displacement or extension for faults which lie beyond the resolution of the sampling system for example a knowledge of d allows the extension measured on a map or seismic section to be corrected for faults whose displacement is below the resolution of the survey based on an overall estimate of d 0 9 for the badajoz cordoba data only some 40 of the extension would be recorded by map scale faults a corrected extension of 41 along the shear zone is estimated which if typical for the entire 300 km zone represents some 87 km of along strike extension thus work suggests that significant displacement occurs on faults which are too small to be interpreted from conventional seismic profiles and geological maps

the geometry of listric growth faults in the devonian basins of sunnfjord w norway thick devonian clastic sequences accumulated in fault bounded basins in w norway at the close of the caledonian orogeny and mark the beginning of a phase of crustal extension traditionally the eastern boundary fault to the devonian basins has been regarded as a thrust but cross sections based on the use of a branch line reveal it to be an extension fault there is clear omission of structural section across the boundary and by matching up metamorphic rocks in the hanging and foot walls of the boundary fault over 40 km of extensional dip slip can be measured at the n end of the fault the boundary fault is a flat lying listric fault with rollover anticlines in the hanging wall the fault also cuts up and down section along strike to form lateral ramps parallel to the movement direction these ramps appear as wrench faults in outcrop the ramp flat geometry of the fault may have been inherited from a precursor caledonian thrust fault which reversed its sense of slip in early middle devonian times to form the basins over 25 km of onlapping sediment accumulated in the largest basin during faulting in 14 ma with an average slip rate on the fault of 3 mm yr 1

background δ 34 s values of kupferschiefer sulphides in poland pyrite marcasite nodules regional background 34s values of pyrite marcasite nodules throughout the zechstein basin in poland have been measured to help estimate the proportion of externally derived sulphur in the kupferschiefer cu ag ores the 34s values of the 17 fes2 nodules measured range widely from 25 2 to 51 9 similar to the previously published 28 to 43 range in disseminated pyrite in the kupferschiefer the wide variation cannot be attributed to pyrite versus marcasite mineralogy amount of contained chalcopyrite or sphalerite carbonate versus shale host rock early versus late formation percent of included calcite or to size shape or texture there is also no relation with proximity to the centres of copper mineralization in southwestern poland where sulphides are typically isotopically heavier the 34s values do however vary directly with percent of host rock fragments included in the nodules repeat samples that were washed with acid or hot water show the same wide variation indicating that contamination by sulphate sulphur in the host rock is not a factor neither is organic sulphur because of its small volume instead the sulphur composition may be fundamentally controlled by the formation mechanism of the nodule whereby 34s rich sulphide is preferentially concentrated possibly replacing anhydrite lenses alternatively a network of host rock inclusions might act as a more accessible conduit for later 34s rich fluids to infiltrate the nodule and add to earlier 34s poor pyrite in the ore deposits higher 34s values of ore nodules suggest less indigenous sulphur in limestone than shale lithologies an isotopic temperature of 61 c from a chalcopyrite galena pair agrees with other estimates of 105 c higher values in ore nodules veinlets than in adjacent disseminations and the calculated 34spy value from a pyrite bornite mixture support the idea that metal bearing 34s rich fluids penetrated the kupfer schiefer through a network of fractures

3d lithosphere scale density model of the central european basin system and adjacent areas abstract to analyze the first order structural features characterizing the crust and the lithospheric mantle below the central european basin system and adjacent areas a new lithosphere scale 3d structural density model has been derived that integrates published knowledge with 3d gravity modeling with this study we aim to integrate previous results on sub domains of the study area and regional results of limited resolution in conjunction with 3d gravity analysis to derive the configuration of the lower crust and lithospheric mantle that is consistent with the known density distribution of the sediment fill and with observed deep seismic data as well as with observed gravity the derived 3d density model resolves the internal configuration of the crystalline crust below the central european basin system and adjacent areas at the regional scale and shows that the crystalline crust is characterized by a layered structure the upper to middle crystalline crust is characterized by relatively low seismic p wave velocities and densities it shows strong variations in thickness across the study area that partly correlate spatially with the inherited segmentation in response to crustal amalgamation this upper to middle crystalline crust is underlain by a continuous high density high velocity lower crustal layer locally more than 30 km thick beneath the east european craton and generally decreasing in thickness from the older to the younger tectonic domains though the thickness of this high density lower crust is generally small below the permo cenozoic central european basin system it can reach locally more than 18 km below the northeast german and the norwegian danish basins the derived depth to the lithosphere asthenosphere boundary confirms previously proposed geometries and is up to 230 km deep beneath the precambrian domain but less than 100 km deep beneath the phanerozoic domains implying that the average thermal gradient is higher in the phanerozoic lithosphere than in the precambrian part

the solubility of nickel ni in crude oil at 150 200 and 250 c and its application to ore genesis abstract the very low solubility of ni in saline brines and the correspondingly high concentration of ni in some crude oils raise the possibility that liquid hydrocarbons may be the ore fluids for black shale hosted ni deposits to test the feasibility of this hypothesis ni wires were reacted with three crude oils of differing composition at 150 200 and 250 c for up to 30 days and the concentration of ni in the oil determined at 150 c ni concentrations in the three oils remained relatively low above 200 c however ni concentrations were elevated and correlated positively with the thiol content of the oil our most thiol rich oil dissolved 217 40 4 ppm ni after 30 days at 250 c x ray photoelectron spectroscopic xps analyses performed on the residual oil coating the ni wires after reaction independently corroborate the conclusion that ni has a strong chemical affinity for thiols in crude oil in crude oils with no thiols the ni reacted with other sulfur compounds potentially sulfonic acids to form thiols significantly our xps analyses show that iron fe from the oil was embedded in the ni wire synchronously with the attachment of thiols this suggests that fe has an affinity for ni and that the thiolation of ni by crude oil may depend on the availability of fe in the oil in addition to thiols porphyrins also likely play an important role in the dissolution of ni as shown by the fact that the oil in which ni was most soluble has a high nitrogen content whereas in the other oil which is characterized by a high thiol content the ni solubility was relatively low and the nitrogen content of this oil was below the detection limit immature biodegraded oils that are sourced from carbonate rocks generally tend to be enriched in asphaltenes ni and sulfur nevertheless some mature oils acquire anomalously large thiol contents through thermochemical sulfate reduction tsr a high temperature 100 to 140 c reaction occurring commonly in carbonate reservoirs which involves the abiotic reduction of sulfate minerals at the expense of oil or bitumen thus given the affinity of ni for thiols large volumes of ni poor oil can potentially be altered by tsr to produce smaller volumes of residual oil enriched in thiols and ni

integration of knowledge based seismic inversion and sedimentological investigations for heterogeneous reservoir abstract conventional geological modelling methods are not capable to provide precise and comprehensive model of the subsurface structures when dealing with insufficient data knowledge based methods employing rule bases techniques are found vast applications in geoscience studies these methods are applicable for petroleum reservoir geological modelling and characterizations specifically for geologically complex structures in this study we present a knowledge based seismic acoustic impedance inversion method which employs rule based method for porosity estimation the back propagation algorithm and the fuzzy neural network are also used in the methodology for parameter optimization and definition of nonlinear relationship between seismic attributes and porosity of the reservoir rock the methodology initiates by seismic acoustic impedance inversion followed by conventional porosity estimation subsequently a knowledgebase was designed by investigation on more than 24 published case studies this knowledgebase was used for definition of rules and optimization number of rules and improve efficiency of the inference engine the porosity model obtained by conventional method in previous step would be used for primary evaluation of the rules the extracted rules and optimized number rules then would be used for rule based porosity estimation the methodology was applied on a petroleum field containing two heterogeneous reservoir formations result of application of the proposed approach was evaluated with core analysis thin sections and drilling data consistency of result obtained by the proposed method with geological data has shown its capability to resolve problem of insufficient data in reservoir geological modelling

the elbe fault system in north central europe a basement controlled zone of crustal weakness abstract the elbe fault system efs is a wnw striking zone extending from the southeastern north sea to southwestern poland along the present southern margin of the north german basin and the northern margin of the sudetes mountains although details are still under debate geological and geophysical data reveal that upper crustal deformation along the elbe fault system has taken place repeatedly since late carboniferous times with changing kinematic activity in response to variation in the stress regime in late carboniferous to early permian times the elbe fault system was part of a post variscan wrench fault system and acted as the southern boundary fault during the formation of the permian basins along the trans european suture zone sensu geol mag 134 5 1997 585 the teisseyre tornquist zone ttz most probably provided the northern counterpart in a pull apart scenario at that time further strain localisation took place during late mesozoic transtension when local shear within the elbe fault system caused subsidence and basin formation along and parallel to the fault system the most intense deformation took place along the system during late cretaceous early cenozoic time when the elbe fault system responded to regional compression with up to 4 km of uplift and formation of internal flexural highs compressional deformation continued during early cenozoic time and actually may be ongoing the upper crust of the elbe fault system which itself reacted in a more or less ductile fashion is underlain by a lower crust characterised by low p wave velocities low densities and a weak rheology structural seismic and gravimetric data as well as rheology models support the assumption that a weak stress sensitive zone in the lower crust is the reason for the high mobility of the area and repeated strain localisation along the elbe fault system

multi scale fracture network analysis from an outcrop analogue a case study from the cambro ordovician clastic succession in petra jordan abstract a regional multi scale fracture network is prominently exposed in the cambro ordovician sedimentary succession in south western jordan this succession consists of marine deposits overlain by heterogeneous deltaic sediments culminating in 500 m of massive to cross bedded fluvial sandstones a data set acquired from high resolution satellite imagery and field measurements enables the quantification of the geometry and spatial characteristics of the fracture network in three dimensions five directional fracture sets are identified from the satellite data with mean strikes of 000 040 065 120 and 145 large fracture zones longer than 600 m composed of tightly spaced joints confined in fracture swarms exhibit a log normal trace length distribution and the fracture swarms are regularly spaced the trace length distribution of intermediate fractures 40 600 m long exhibits power law characteristics and the fractures are clustered reflecting different fracture system styles and stratigraphic controls as a function of scale the small scale fracture network is strongly dependent on the distribution of bedding plane discontinuities throughout different parts of the succession the multi scale fracture network is categorized in a three tier hierarchical fracture model that reflects underlying stratigraphic controls in the study area this type of model can be used to improve the representation of fracture networks in fluid flow simulations of fractured reservoirs with hybrid models that combine elements of discrete fracture networks and continuum models

geochemistry of the sinian cambrian gas system in the sichuan basin china abstract based on the outcrops core samples drilling cuttings seismic and geochemical data natural gases of the sinian cambrian gas system were derived from four sets of over mature high quality source rocks the cambrian qiongzhusi source rock is sapropelic with toc of 1 94 ro eq of 1 83 3 90 and a thickness of 140 m on average the sinian 620 541 ma doushantuo source rock is sapropelic with toc of 1 69 ro eq of 2 08 3 83 and a thickness of 11 m on average the 3rd member of the dengying fm is also sapropelic with toc of 1 43 ro eq of 3 16 3 21 and a thickness of 13 m on average the 2nd and 4th members of the dengying fm are dominated by algal dolomite with toc of exhibiting 0 39 ro eq of 1 97 3 46 and a thickness of 246 m on average most of the 13c2 values are lower than 28 and gas dryness is 99 indicating that the natural gas is oil derived with high maturity the high contents of isoparaffins and cycloparaffin suggest that natural gas in the sinian cambrian reservoir was originated from secondary oil cracking the cambrian longwangmiao gas was mainly derived from the cambrian qiongzhusi source rock and the gas within the sinian dengying formation mainly originated from the three sinian source rock layers the area with gas generation intensity superimposed the four sets of source rocks exceeding 6 109 m3 km2 covered 80 of the sichuan basin the proved reserves exceed 1 0 1012 m3 in the sinian cambrian gas system and the accumulated gas resource in the sinian cambrian gas system might exceed 5 1012 m3

seismic structure across the caledonian deformation front along mona lisa profile 1 in the southeastern north sea abstract seismic data from the mona lisa marine and onshore north sea acquisition for lithospheric seismic analysis project in the southeastern north sea image the caledonian deformation front cdf which is the collisional suture between baltica to the north and east and avalonia to the south and west the n s trending mona lisa normal incidence reflection profile 1 was recorded to 26 s twt coincident wide angle data were acquired on nine ocean bottom hydrophones and several onshore mobile seismographs along and off the profile the model of compressional seismic velocity shows three different crustal types a a typical three layered shield type crust below the ringkobing fyn high to the north b a highly complex transitional crust in the central part and c a two layered crust of caledonian origin to the south sharp and strong normal incidence and wide angle reflections from moho were recorded south of the caledonian deformation front in contrast to less distinct reflections further north s dipping crustal reflections from 4 to 11 s twt over 70 km horizontal distance terminate at moho and coincide with a change in the seismic velocity structure this indicates northward obduction of avalonian crust non migrated normal incidence seismic sections show crossing weak n dipping and stronger s dipping reflections to 20 s twt from the uppermost mantle we propose a tectonic model where the closure of the tornquist sea took place along a n dipping subduction zone which was later overprinted by a late or post caledonian s dipping shear zone sub moho velocities are 7 8 7 9 km s under 34 35 km thick baltica crust and 8 1 8 3 km s under 25 26 km thick caledonian crust the sub horizontal moho across the caledonian collision zone implies late or post caledonian re equilibration of the seismological moho we interpret the low velocity upper mantle 7 8 8 1 km s to the north as former baltica lower crust in eclogite facies after pressure induced metamorphism as a result of lithospheric flexure during the caledonian orogeny these rocks today appear as upper mantle that was uplifted to their present position during the middle devonian collapse of the north german polish caledonides

two dimensional simulation of controls of fracture parameters on fracture connectivity two dimensional fracture simulation is conducted to analyze the controls of different fracture parameters variations in fracture orientation density and length on fracture network connectivity three different scenarios which are commonly encountered in natural fracture systems are analyzed 1 a single fracture set 2 two fracture sets with one primary through going set and 3 two fracture sets with approximately equal parameters the modeling reveals that certain parameters are more dominant in controlling the connectivity for each of the settings for a single set of fractures increases in length and dispersion and a decrease in spacing all result in higher fracture parallel connectivity but the decrease in spacing is the most important in increasing fracture normal connectivity especially where the dispersion in fracture strike is very low simulations of two sets of fractures reveal that the density length and angle between the two sets are important factors in producing complete connectivity in cases where one set of fractures is a systematic throughgoing set a critical combination of length of the second set and the angle between the two sets results in complete connectivity where both sets of fractures have varying length and density the influence of increasing density of one set has a great effect on connectivity when the other set is short and a more subtle to insignificant change when the other set is long the network also shows higher connectivity with increasing angles up to 90 between the two sets

from field data to fracture network modeling an example incorporating spatial structure this paper describes a technique for processing field data for a fracture network model which accounts for the observed spatial variability this has been done by generating a network subregion by subregion where the properties of each subregion are predicted through geostatistics once the geometry of a particular realization is specified flow through the network is studied we develop the method for a two dimensional analysis based on data from fanay augeres a uranium mine in france we plan to extend the analysis to three dimensions and compare the results with in situ test results in particular we have focused on the data collected in a long section of a drift where fractures have been mapped and steady state permeability tests have been performed in 10 boreholes in order to generate fractures in a statistically heterogeneous region we first divided the region into statistically homogeneous subregions in each subregion and for each fracture set we must specify the areal fracture density and the orientation length and aperture distributions we divided the fractures into five sets based on tectonic history and observed that for each set fractures spaced close together tended to have similar orientations this was built into the simulation an estimate of the aperture distribution for each set was made by assuming that the hydraulic apertures of the fractures intersecting a well test zone were proportional to the fracture opening observed in the core data input to the geostatistical analysis for each set consisted of 16 values of mean length and density of fractures in each 5 m by 2 m section of the drift wall the results of the simulation are tables of values for mean length and fracture density for each of the five sets the value of density simulated for each subregion was used directly to determine the number of fractures to be generated of that set in the subregion the value of mean length was used as the mean of the length distribution in the subregion the local coefficient of variation for length was the same in every subregion using the data described above we generated a 100 m by 100 m fracture network in a series of 100 statistically homogeneous subregions the fractured region generated has a total of 65 740 fractures a 70 m by 70 m region was isolated for directional permeability testing results show that the system is barely connected about 0 1 of the fractures essentially control permeability in the language of percolation theory this mesh is close to the critical density for which infinite clusters of fractures are found problems remaining include that 1 the analysis should be extended to three dimensions 2 the geostatistical simulation and network simulation should be combined rather than used as two separate operations and 3 the nature of flow through single fractures at fanay augeres should be investigated

influences of secondary oxidation and sulfide formation on several maturity parameters in kupferschiefer vitrinite reflectance and methylphenanthrene indices are important maturity parameters for coal and other sedimentary organic matter they have been widely used for determining the maturity of organic matter in kupferschiefer however during the study of organic matter in kupferschiefer it has been found that vitrinite reflectance and methylphenanthrene indices were influenced by oxidizing fluids and sulfide formation in order to study the influence degree on maturity parameters three kupferschiefer profiles from the konrad polkowice and sangerhausen mines were analysed by microscopic and geochemical methods the results indicate that the kupferschiefer in the studied areas was deposited in normal marine and euxinic environment according to organic facies parameters the kerogen belongs to type ii under the influence of secondary oxidation organic matter was altered from type ii to type iii in the oxidized samples the values of vitrinite reflectance are clearly higher and the values of methylphenanthrene indices are lower than those of non oxidized samples because of the depletion of alkylated phenanthrenes the actual maturity can be calculated by revision of measured vitrinite reflectance and calculated vitrinite reflectance in the oxidized kupferschiefer samples in high mineralized samples hydrogen donation for thermochemical sulfate reduction occurred in alkylated phenanthrenes and resulted in a decrease of methylphenanthrene index values during kupferschiefer mineralization the methylphenanthrene index values in these samples can be calculated empirically

sims u pb zircon ages and ni mo pge geochemistry of the lower cambrian niutitang formation in south china constraints on ni mo pge mineralization and stratigraphic correlations abstract in comparison with previous studies on the ni mo pge ore deposits within the deep water lower cambrian black shales of the niutitang formation around hunan and guizhou provinces this study focused on the shallow water ni mo pge enriched layer of the niutitang formation around hubei province by means of an integrated geochronological pge ree and trace element geochemical study the results suggest the ni mo pge enriched layer has a dominant seawater origin whereas the ni mo pge ore deposits have mixed seawater hydrothermal and terrigenous origins trace metals precipitated from ambient seawater under anoxic suboxic settings at exceedingly slow sedimentation rates with episodic injections of fresh oxidized seawater organic matter played an important role in sourcing transporting and precipitating trace metals however decay of organic material by means of sulfate reducing reactions and or fluid reworking overprinted primary relationships with trace metal contents however the positive linear relationships are clearly shown between organic carbon and trace metal contents new sims u pb ages constrained the depositional age of the ni mo pge enriched layer to be 532 527 ma which argues against previous assumption that the anoxic event recorded in the ni mo pge took place at the ediacaran cambrian boundary furthermore new radiometric ages suggest the shuijingtuo niutitang formation could be correlated with shiyantou formation dahai and upper zhongyicun members whereas yanjiahe formation correlated with daibu and lower zhongyicun members in yunnan province respectively

heat flow and lithospheric thermal regime in the northeast german basin abstract new values of surface heat flow are reported for 13 deep borehole locations in the northeast german basin negb ranging from 68 to 91 mw m 2 with a mean of 77 3 mw m 2 the values are derived from continuous temperature logs measured thermal conductivity and log derived radiogenic heat production the heat flow values are supposed free of effects from surface palaeoclimatic temperature variations from regional as well as local fluid flow and from thermal refraction in the vicinity of salt structures and thus represent unperturbed crustal heat flow two d numerical lithospheric thermal models are developed for a 500 km section along the dekorp basin 9601 deep seismic line across the basin with a north eastward extension across the tornquist zone a detailed conceptual model of crustal structure and composition thermal conductivity and heat production distribution is developed different boundary conditions for the thickness of thermal lithosphere were used to fit surface heat flow the best fit is achieved with a thickness of thermal lithosphere of about 75 km beneath the negb this estimate is corroborated by seismological studies and somewhat less than typical for stabilized phanerozoic lithosphere modelled moho temperatures in the basin are about 800 c heat flow from the mantle is about 35 to 40 mw m 2 in the southernmost part of the section beneath the harz mountains higher moho temperatures up to 900 to 1000 c are shown while the relatively high level of surface heat flow in the negb obviously is of longer wave length and related to lithosphere thickness changes in crustal structure and composition are responsible for short wave length anomalies

deep seismic survey images crustal structure of tornquist zone beneath southern baltic sea the tornquist zone is europe s longest tectonic lineament and bisects the continent in a nw se direction from the north sea off nw denmark to the black sea new deep seismic reflection and coinci

origin of the regional stress in the north german basin results from numerical modelling abstract we use a thin sheet approach to investigate the effects induced by the alpine collision on the deformation and regional stress in northern europe with special emphasis on the ne german basin here new seismic crustal studies indicate a flexural type basin which may have been induced by compressive forces transmitted from the south due to the alpine orogeny finite element techniques are used to solve the equations for the deformation of a continuum described by a linear creep rheology and a spatial resolution of about 0 5 the model has been constrained by stress and seismic data we show that a relatively strong lithosphere below the northern margin of the german basin at the transition with the baltic shield may explain the characteristic regional stress field in particular the fan like pattern which is observed within the region furthermore the predicted strain rate pattern resembles the seismically recognizable undeformed area of the north german basin

chemical and petrographic evidence for thermal cracking and thermochemical sulfate reduction of paleo oil accumulations in the ne sichuan basin china significant extents of heterogeneity are observed in the optical properties reflectance values and s c atomic ratio values of solid bitumens in the carbonate reservoirs of the lower triassic feixianguan and changxing formations in the puguang gas field the largest in marine carbonates in china the chemical and stable carbon isotope compositions of the gaseous alkanes in the produced gases also depend on field location with no clear correlation with the hydrogen sulfate content these data indicate that the gas reservoirs are highly compartmentalized this manuscript describes an integrated chemical and petrographic approach for distinguishing solid bitumens formed by thermal cracking and by thermochemical sulfate reduction tsr the fact that most reservoir bitumens have only been partially affected by tsr suggests that sulfate supply appears to be a major limiting factor for the tsr reactions involving gaseous alkanes

seismic evidence of caledonian deformed crust and uppermost mantle structures in the northern part of the trans european suture zone sw baltic sea abstract collisional structures from the closure of the tornquist ocean and subsequent amalgamation of avalonia and baltica during the caledonian orogeny in the northern part of the trans european suture zone tesz in the sw baltic sea are investigated a grid of marine reflection seismic lines was gathered in 1996 during the dekorp basin 96 campaign shooting with an airgun array of 52 l total volume and recording with a digital streamer of up to 2 1 km length the detailed reflection seismic analysis is mainly based on post stack migrated sections of this survey but one profile has also been processed by a pre stack depth migration algorithm the data provides well constrained images of upper crustal reflectivity and lower crustal uppermost mantle reflections in the area of the caledonian suture a reflection pattern is observed with opposing dips in the upper crust and the uppermost mantle detailed analysis of dipping reflections in the upper crust provides evidence for two different sets of reflections which are separated by the o horizon the main decollement of the caledonian deformation complex s dipping reflections beneath the sub permian discontinuity and above the o horizon are interpreted as caledonian thrust structures beneath the o horizon sw dipping reflections in the upper crust are interpreted as ductile shear zones and crustal deformation features that evolved during the sveconorwegian orogeny the caledonian deformation complex is subdivided into 1 s dipping foreland thrusts in the north 2 the s dipping suture itself that shows increased reflectivity and 3 apparently ne dipping downfaulted sedimentary horizons south of the avalonia baltica suture which may have been reactivated during mesozoic normal faulting the reflection moho at 28 35 km depth appears to truncate a n dipping mantle structure which may represent remnant structures from tornquist ocean closure or late collisional compressional shear planes in the upper mantle a contour map of these mantle reflections indicates a consistent northward dip which is steepest where there is strong bending of the caledonian deformation front the thin skinned character of the caledonian deformation complex and the fact that n dipping mantle reflections do not truncate the moho indicate that the baltica crust was not mechanically involved in the caledonian collision and therefore escaped deformation in this area

giant gas discovery in the precambrian deeply buried reservoirs in the sichuan basin china implications for gas exploration in old cratonic basins abstract an estimated trillions of cubic meters of natural gas have recently been discovered in the sinian dolomite reservoirs in the sichuan basin china the 20 26 m thick reservoirs were found in deep structural lithologic traps of 5000 5500 m deep the sinian gas is thought to have been derived mainly from the sinian source rocks and partly from the cambrian source rocks the gas is thermally matured with a dryness ratio c1 c1 4 of 0 997 0 9998 c2h6 content

the origin of tensile fracture lineaments abstract fracture controlled lineaments commonly seen where brittle basement is exposed at the earth s surface are generally restricted to a small number of sets with angles of 45 90 between sets the length frequency distribution of lineaments in each set follows a truncated poisson function such lineaments usually show almost no shearing offset suggesting a tensile origin a simple mechanical model of tensile fracturing is used to explain the spacing directions and length of lineaments as well as their depth frequency distribution results suggest that the penetration depth of tensile fractures which produce lineaments at the earth s surface is directly related to their length and that the fracture density is inversely proportional to fracture depth finally the angles between lineament sets may be controlled by the ratio of strength of unfractured rock to that of pre existing fractures which might heal with time the most likely source of tension is tectonic uplift fractures due to typical uplifts of 0 5 1 km over distances of 10 100 km may penetrate as brittle fractures to several kilometres into the crust perhaps to the depth at which seismic activity ceases

crustal structure along the central segment of the egt from seismic refraction studies abstract the seismic refraction line between the gulf of genova and the baltic sea was carried out in 1986 as part of the european geotraverse egt 86 the central segment of the egt also known as eugemi european geotraverse middle part has a total length of 825 km and runs from the northern margin of the alps to the baltic sea traversing mainly the variscan mountain area of western germany the p wave data of nine shotpoints were interpreted in detail and a two dimensional p velocity model of the crust was developed between the molasse basin and the southern end of the north german basin for the north german basin the data quality justifies only the construction of a simplified model the internal crustal structure is quite complex in the upper crust of the moldanubian and saxothuringian zones of the variscan orogen the velocities are lower than in the rhenohercynian area the velocity of 6 0 km s representing consolidated seismic basement is reached at depths of as much as 10 12 km northern margin of alps and north german basin and of only 3 km under the mid german crystalline rise mid crustal velocities range from 5 8 to 6 1 km s forming weak velocity reversals in some parts in the lower crust velocities as low as 6 2 km s are seen near the alps in contrast to velocities between 6 8 and 7 2 km s in the exposed variscan orogen north of shotpoint e between hannover and the river elbe the velocity of the lower crust is about 6 4 km s north of the elbe line it increases abruptly to 6 9 km s the crust mantle boundary rises from 34 km depth under the northern margin of the alps to 29 km under the swabian jura under the variscan orogen to the north the crustal thickness varies only slightly around an average depth of about 29 1 k but drops to about 30 km under the north german basin between the elbe line and the ringkobing fyn high the moho rises to a depth of about 26 km and the data indicate at least one fault like step of 1 km before the crust thickens toward the basement high the velocities in the uppermost mantle show considerable variation the highest velocity of 8 4 km s is observed beneath the saxothuringian zone and the lowest values of 7 8 7 9 km s are recorded under the hessen depression

microscopic modelling of the hydraulic fracturing process a microscopic perspective is introduced in this study which offers a detailed insight at the inter particle level to the geo mechanical responses caused by fluid injection and the resulting pressure build up this was achieved by employing the discrete element method dem to model the pressure development and the subsequent fracturing and or cavity propagation this technique represents the formation material as an assembly of discrete particles linked to each other through contacts numerical experiments were carried out on two sample materials for the first instance tests were carried out on a bulk material representative of a generic intact rock with the breakage of inter particle bonds indicating the formation of cracks the second series of tests was carried out on granular type materials such as sand where particle separation signified cavity initiation and separation it was observed from the dem modelling results that the intact rock material showed a predominance of mode ii fracturing at high fluid velocities however when the fluid velocity is reduced considerably the fracturing behaviour tended towards more of mode i also records of the pressure development were taken from the numerical results and were used to monitor the fracturing events the outcome of this study highlights important aspects of the hydraulic fracturing process especially at the particle particle scale and thus provides a strong basis for more exhaustive studies involving larger scale reservoir modelling and more complex fracturing scenarios

incorporation of fracture directions into 3d geostatistical methods for a rock fracture system simulating a rock fracture distribution is an important problem common to various fields in geosciences this paper presents geofrac a geostatistical method to simulate a fracture distribution by incorporating the directions strikes and dips of the sampled fracture data into the simulation fracture locations are generated randomly following fracture densities assigned by a sequential gaussian simulation fracture directions are transformed into an indicator set consisting of several binary 0 and 1 variables and the variables are compressed using the principal component analysis ordinary kriging is then employed to estimate the distributions of these principal values and the results are back transformed into the coordinate system of the original indicator set fracture directions are generated randomly using their histograms within the defined directional interval finally facets fracture elements are determined from the simulated locations and directions and the fractures within the angle and distance tolerances are connected to form a fracture plane from a case study of applying geofrac to the fracture data in kikuma granite southwest japan geofrac was shown to be able to depict a plausible fracture system because the simulated directions corresponded well to those measured furthermore the simulated fracture system was available to estimate the hydraulic conductivity of the study site which was roughly in agreement with the average of hydraulic test results

evidence for multiple stages of oil cracking and thermochemical sulfate reduction in the puguang gas field sichuan basin china the puguang gas field is the largest gas field found in marine carbonates in china marine carbonate reservoirs in this field were buried to a depth of about 7000 m 22 966 ft and experienced maximum temperature up to 220c before uplift to the present day depth of 5000 5500 m 16 404 18 045 ft with present day thermal maturity between 2 0 and 3 0 equivalent vitrinite reflectance ro sulfur rich pyrobitumens with reflectance up to 3 5 are widespread in the reservoirs and resulted from thermal cracking of crude oils most likely generated from upper permian source rocks and thermochemical sulfate reduction tsr natural gases in the puguang gas field have wide variations in nonhydrocarbon gas contents with h2s contents between 5 1 and 58 3 and co2 contents between 7 9 and 18 0 the hydrocarbon gases originated mainly from thermal cracking of accumulated oil but were altered by tsr thermochemical sulfate reduction in the study area exerted different effects on the isotope compositions of different hydrocarbon gas components at different tsr stages the differential increase of 13c values for different gas components reflects transformation from a heavy hydrocarbon gas dominated tsr stage to a methane dominated tsr stage this caused a decrease of 13cmethane13cethane values and a corresponding conversion from reversed to normal isotope distributions thermochemical sulfate reduction in the study area appears to have been limited by sulfate concentrations in the reservoirs a successive three stage tsr series namely liquid hydrocarbon involved tsr heavy hydrocarbon gas dominated tsr and methane dominated tsr occurred in reservoirs with sufficient sulfate concentration methane can be the dominant organic reactant for tsr but only at elevated temperature and after most c2 hydrocarbons are exhausted

zinc solubility speciation and deposition a role for liquid hydrocarbons as ore fluids for mississippi valley type zn pb deposits abstract although the ore fluid for mississippi valley type mvt deposits is universally considered to be a basinal brine the common occurrence of liquid hydrocarbons as inclusions in one of the ore minerals sphalerite raises the question of whether liquid hydrocarbons could play a role in metal transport here we explore the potential of liquid hydrocarbons to act as an ore fluid by determining the steady state concentration of zinc in crude oil and evaluating the factors that promote its dissolution to this end zinc wires were reacted with a series of oils labelled oils a b and c at 150 200 and 250 c and the steady state concentration of zn was determined zinc concentrations were observed to increase with temperature and with the total acid number tan of the oils the latter of which is strongly correlated to the carboxylic acid content of crude oil crude oil b the highest tan oil dissolved 1700 0 8 ppm at 250 c which is comparable to the highest zn concentration inferred to have been dissolved in brines interpreted to represent mvt ore fluids x ray photoelectron spectroscopic xps analyses performed on the residual oil coating the zinc wires after the reaction supported the conclusion that zn has a strong chemical affinity for carboxylic acids in crude oil finally an experiment designed to precipitate sphalerite crystals from a zn rich synthetic oil at room temperature showed that sphalerite precipitation from liquid hydrocarbons proceeds efficiently in a carbonate buffered h2s rich environment

fluid velocity fields in 2d heterogeneous porous media empirical measurement and validation of numerical prediction the scale invariance of geological material and the consequent absence of a length scale on which to base the upscaling of measurements made on geological samples represent a serious challenge to the prediction of fluid behaviour in rock at economically interesting scales numerical simulation is an important tool for understanding constraints in this problem and current discrete fluid models in which complex boundary conditions can be represented have the potential for testing many possible upscaling schemes at present however there are no accurate empirical data on the distributions of fluid velocities in complex scale invariant geometries with which to validate such models to address this fluid velocity fields in complex 2d media with fractal heterogeneity were measured digital models of rock geometries were created and translated into physical form using electric discharge machining and stereolithography these physical models were then enclosed between parallel sheets of glass and perspex forming a hele shaw cell which was permeated with water doped with small neutrally buoyant spheres and pumped at accurately steady and reproducible velocities local velocity vectors were estimated by the analysis of sequential images captured using high resolution video precision digital control systems were used to move the cell relative to the camera and repeated measurements allowed the construction of full 2d velocity fields the accuracy of the technique was assessed by comparison between automated and manual measurements confirming the accuracy over approaching three orders of magnitude in velocity the results have been compared to the output of lattice boltzmann lb simulations of flow in identical geometries showing that the correlation between simulated and measured velocity fields is strongly dependent on the viscosity used in the numerical simulation in particular the lb scheme used in these tests is incapable of simulating correct viscosities for complex geometries some important effects are shown to be strongly viscosity dependent and it is concluded that some simulations may be able to predict the behaviour of high viscosity fluids only nonlinear effects between fracture and matrix flow are likely to be more important in these cases

generation and verification of three dimensional network of fractured rock masses stochastic discontinuities based on digitalization accuracy of seepage simulation in rock masses is directly influenced by related geometrical parameters of dfn discrete fracture network models in this paper a well planned investigation of rock mass discontinuities was conducted on well exposed outcrops in beishan gansu province one of the main candidate sites for the chinese high level radioactive waste repository using digital techniques e g global positioning system close range digital photogrammetry and geographical information system this allows for very efficient collection of large volumes of data over 10 000 discontinuities were obtained at the study site jijicao block based on statistical parameters two homogeneities were identified and the dominant sets were also delineated which suggested that two sets exist in homogeneity i while three sets in homogeneity ii in homogeneity i the optimal fracture diameter probability distributions of both sets were lognormal three dimensional stochastic dfn models were established for both homogeneities based on stochastic process as well as statistical parameters the reliability of the model was validated by both graphical and numerical methods results showed that digital techniques used in this study can overcome the problem of sample size and precision restriction posed by traditional methods which leads to a more effective application of dfn model and are thus suitable for tasks such as detailed mapping of rock masses in large area it is believed that this verified dfn model is more appropriate for subsequent calculations of mechanical properties and seepage of fractured rock masses

uraniferous bitumen nodules in the talvivaara ni zn cu co deposit finland influence of metamorphism on uranium mineralization in black shales in the central part of the fennoscandian shield the talvivaara ni zn cu co deposit hosted by palaeoproterozoic metamorphosed black schists contains low uranium concentrations ranging from 10 to 30 ppm the talvivaara black schists were deposited 2 0 1 9 ga ago and underwent subsequent metamorphism during the 1 9 1 79 ga svecofennian orogeny anhedral uraninite crystals rimmed by bitumen constitute the main host of uranium u pb secondary ion mass spectrometry dating indicates that uraninite crystals were formed between 1 878 17 and 1 871 43 ma during peak metamorphism rare earth element patterns and high th content average 6 38 wt in disseminated uraninite crystals indicate that u was concentrated during high temperature metamorphism 400 c the formation of bitumen rims around uraninite may be explained by two distinct scenarios a a transport of u coincident with the migration of hydrocarbons or b post metamorphic formation of bitumen rims through radiolytic polymerization of gaseous hydrocarbons at the contact with uraninite

the moho depth map of the european plate summary the european plate has a 4 5 gy long and complex tectonic history this is reflected in the present day large scale crustal structures a new digital moho depth map is compiled from more than 250 data sets of individual seismic profiles 3 d models obtained by body and surface waves receiver function results and maps of seismic and or gravity data compilations we have compiled the first digital high resolution map of the moho depth for the whole european plate extending from the mid atlantic ridge in the west to the ural mountains in the east and from the mediterranean sea in the south to the barents sea and spitsbergen in the arctic in the north in general three large domains within the european plate crust are visible the oldest archean and proterozoic crust has a thickness of 40 60 km the continental variscan and alpine crust has a thickness of 20 40 km and the youngest oceanic atlantic crust has a thickness of 10 20 km

reactions of hydrothermal solutions with organic matter in paleoproterozoic black shales at talvivaara finland evidence from multiple sulfur isotopes abstract stable isotopic studies of archean paleoproterozoic sedimentary rocks older than 2 4 ga have documented large mass anomalous fractionations of sulfur isotopes 33 s 0 0 2 while younger rocks record little to no anomalous fractionation of sulfur isotopes this change from large anomalous fractionations to sulfur isotope values that fall on the terrestrial fractionation line has been proposed to represent the transition from an essentially anoxic archean atmosphere to an oxygenated atmosphere here we present 34 s and 33 s data for 28 core samples from paleoproterozoic 2 1 1 9 ga metamorphosed black shales and associated sulfide ores in eastern finland previous 34 s of studies of the talvivaara and outokumpu deposits of eastern finland focused on single grain analyses of sulfides while this study presents data from sequentially extracted sulfur fractions e g acid soluble sulfides chrome reducible sulfides elemental sulfur the sulfur isotope results range between 16 6 and 11 6 for 34 s 8 6 and 6 0 for 33 s and 1 25 and 0 55 for 33 s the anomalously fractionated samples are not consistent with previous findings that large anomalous fractionations of sulfur isotopes are absent in sedimentary metasedimentary rocks younger than 2 4 ga it is unlikely that talvivaara sulfides are the products of ultraviolet photolysis of volcanic so 2 in an oxygen poor atmosphere alternatively these sulfides could in part be the products of diagenetic reactions between sediments enriched in organic matter c org and hydrothermal solutions rich in sulfate i e thermochemical sulfate reduction laboratory experiments on thermochemical sulfate reduction have shown that mass anomalous fractionations of sulfur isotopes can be recorded in reduced sulfur products from reactions between simple amino acids and sulfate at 150 300 c a thermochemical sulfate reduction pathway for the mass anomalous signatures in talvivaara samples is consistent with previous genetic models proposed for the origin of the sulfur and organic carbon rich black shales now schists associated with the talvivaara and outokumpu ore deposits at talvivaara metalliferous black shales apparently were deposited under an anoxic to sulfidic marine water column the reported multiple sulfur isotopic data are key geological evidence for mass anomalous fractionations of sulfur isotopes during hydrothermal alteration of fine grained organic rich sediments approximately 20 of samples in this study show large offsets in 33 s values between different extracted sulfur fractions from the same sample which can be explained by classical isotope effects associated with the formation of hydrothermal alteration products that predominantly are retained within the precursor fine grained organic rich units

geochemical investigation of the lower cambrian mineralised black shales of south china and the late devonian nick deposit canada abstract lower cambrian tommotian black shales of the niutitang formation south china host a thin accumulation 5 20 cm of ni mo platinum group elements pge au ni as zn cu v and rare earth elements ree of all known deposits the late devonian ni mo pge sulphide horizon in black shales of the nick deposit selwyn basin in canadian yukon presents the strongest similarity with the niutitang formation polymetallic layer in the present study samples of the mineralised layer and host shales in south china from two mine sites zunyi and sancha were investigated in order to further characterise the prevailing redox conditions and mechanisms involved in the metal concentration process at both sites additional comparison with the nick deposit mineralised layer was also undertaken bulk geochemical analysis including pge analysis were conducted on all samples along with m scale investigation of metal distributions and associations by x ray fluorescence xrf mapping and synchrotron xrf mapping the comparison of the two sites from south china highlights strong similarities in metal enrichment factors pge and ree distribution patterns are also highly similar and suggest a source from seawater strong variations in elemental distributions at m scale were observed at both sites most likely related to intense variations in redox conditions in the sediment the comparison with the nick deposit highlights a stronger enrichment in ni and zn in the nick deposit and a greater variety of minerals in the niutitang shales the pge and ree distributions of both the nick deposit and the niutitang shales however present highly similar patterns and support an origin from seawater the present study provides further insight into mineralisation style and processes in these mineralised black shales highlighting the importance of redox conditions and re emphasizing the role of organic matter in the formation of these mineralised layers

kerogen asphaltene sulfur relationships in sulfur rich monterey oils abstract monterey oils in the santa maria basin onshore and offshore are generally low maturity oils because of low thermal exposure relatively shallow burial for short times they are generated as heavy high sulfur oils because of the composition of the unusual type ii source kerogens which are exceptionally rich in organic sulfur 8 14 these high sulfur kerogens which we designate type ii s appear to generate oil at significantly lower thermal exposures than ordinary type ii kerogens with less than 6 s in contrast to common type ii kerogens which generate oil largely by cleavage at oxygen bridge groups and carbon carbon bonds eliminating co2 h2o and hydrocarbon fragments type ii s kerogens have an additional complement of weak bonds associated with bound sulfur the preferential cleavage at weak sulfur linkages tends to produce larger fragments leading to high initial amounts of asphaltenes resins and sulfur rich aromatics together with smaller amounts of saturated hydrocarbons elemental analyses of monterey kerogens and asphaltenes clearly support the concept that the asphaltenes are essentially fragments of kerogen cleaved sufficiently to be soluble or peptized in this heavy oil system solubilization of asphaltenes is attributed to their interactions with the abundant resins and aromatics this sysstem is sufficiently stable under source and reservoir conditions to allow expulsion and migration for reasonable distance without significant fractionation or changes in gross properties initial asphaltenes have essentially the same atomic h c ratios as the source kerogen but have significantlyy lower o c ratios and slightly lower s c ratios the n c ratios are nearly the same for kerogens and their derived asphaltenes with increasing maturity the h c ratios in asphaltenes decrease much like maturation changes in kerogen the s c ratio also decreases significantly however the o c ratios initially low in asphaltenes and n c ratios increase slightly due to material balance caused by other losses these element composition and atomic ratio relationships allow some important inferences concerning source kerogen composition from analysis of asphaltenes alone this can be useful when potential source rock samples are not available for analysis and or when a choice between alternate source rock possibilities must be made

the solubility of palladium pd in crude oil at 150 200 and 250 c and its application to ore genesis abstract although most economic palladium deposits occur in mafic igneous rocks and are the products of magmatic processes there are a number of polymetallic deposits hosted by organic rich bituminous black shales in which the palladium reaches exploitable concentrations considering that palladium is rarely concentrated by hydrothermal processes and as organic rich black shales are the source beds for the production of hydrocarbons and bitumen commonly records the path taken by these hydrocarbons it is reasonable to entertain the possibility that liquid hydrocarbons may act as an ore fluid for palladium in order to test the potential of liquid hydrocarbons to act as ore fluids pd 0 metal wires were reacted with three crude oils a b and c a being the lightest and c being the heaviest crude oil at temperatures of 150 200 and 250 c after reaction at 150 c the pd concentrations in crude oils a b and c were 60 20 ppb 19 4 ppb and 128 29 ppb respectively the corresponding concentrations at 200 c were 18 6 ppb 17 6 ppb and 50 15 ppb respectively and at 250 c were 16 2 ppb 11 1 ppb and 26 2 ppb respectively n 3 the measured solubility of pd was highest in the heaviest crude oil c all three oils reached their maximum pd concentration at 150 c with pd concentration decreasing progressively as temperature increased to 250 c to gain insights into the mechanism controlling the dissolution of pd in crude oil we analysed the reacted pd wires using x ray photoelectron spectroscopy xps the xps spectrum displays a well defined thiol r sh peak at a binding energy of 163ev which indicates that pd has an affinity for reduced organosulfur compounds moreover pd concentrations were observed to increase with the total thiol content of the oil thereby corroborating the results of the xps analyses our results clearly show that pd solubility in crude oil is promoted by the presence of thiols as thiol rich hydrocarbons usually develop in deep high temperature 100 140 c carbonate sequences containing abundant sulfate mineralization it is thought that the thiols are the products of thermochemical sulfate reduction tsr machel 2001 we therefore propose that liquid hydrocarbons which have interacted with sulfate at relatively high temperature may serve as effective ore fluids for palladium

methane dominated thermochemical sulphate reduction in the triassic feixianguan formation east sichuan basin china towards prediction of fatal h2s concentrations abstract new sour pools have recently found in the lower triassic feixianguan fm carbonate reservoirs in the east sichuan basin in china with h 2 s up to 17 4 by volume a recent blowout from a well drilled into this formation killed hundreds of people as a result of the percentage concentrations of h 2 s in order to assess the origin of fatal h 2 s as well as the cause of petroleum alteration h 2 s concentrations and the isotopes 34 s and 13 c have been collected and measured in gas samples from reservoirs anhydrite pyrite and elemental sulphur 34 s values have been measured for comparison the high concentrations of h 2 s gas are found to occur at depths 3000 m temperature now at 100 c in evaporated platform facies oolitic dolomite or limestone that contains anhydrite nodule occurrence within the reservoirs where h 2 s concentrations are greater than 10 its 34 s values lie between 12 0 and 13 2 cdt this is within the range of anhydrite 34 s values found within the feixianguan fm 11 0 to 21 7 average 15 5 3 5 cdt thus h 2 s must have been generated by thermochemical sulphate reduction tsr locally within the reservoirs burial history analysis and fluid inclusion data reveal that the temperature at which tsr occurred was greater than about 130 140 c suggesting that the present depth temperature minimum is an artifact of post tsr uplift both methane and ethane were actively involved in tsr since the petroleum became almost totally dry no alkanes except methane and methane 13 c values become significantly heavier as tsr proceeded methane 13 c difference thus reflects the extent of tsr while it is tempting to use a present day depth control 3000 m to predict the distribution of h 2 s in the feixianguan fm this is an invalid approach since tsr occurred when the formation was buried some 1000 2000 m deeper than it is at present the likelihood of differential uplift across the basin means that it is important to develop a basinal understanding of the thermal history of the feixianguan fm so that it is possible to determine which parts of the basin have been hotter than 130 140 c

structural controls of fracture orientations intensity and connectivity teton anticline sawtooth range montana the teton anticline is a multiple hinge anticline containing fractured mississippian devonian carbonates in the frontal part of the sawtooth range in montana the structure serves as a good surface analog for fracture patterns and connectivities within subsurface folded carbonate reservoirs the primary fracture sets are longitudinal and transverse relative to the axis of the fold although two additional oblique sets are also present the length and density of the longitudinal fracture sets are strongly controlled by position relative to multiple hinges the transverse fractures are related to changes in fold plunge and exhibit less variation in fracture density fracture connectivity is dependent on the number of fracture sets their orientations and dispersions and the densities of the fracture sets the connectivity is measured using two parameters the fractional connected area fca which represents the fraction of the total sample area that is connected by fractures and the distribution of clusters of different sizes in any given area because the longitudinal fractures represent the dominant fracture set and also show the most variation with structural position the fracture connectivity as measured by both the fcas and the distribution of cluster sizes is greater in the vicinity of the fold hinges the results and approaches used in the study have some important implications for subsurface folded fractured carbonate reservoirs the analysis of sparsely distributed fracture data from wells must be integrated with an understanding of the controls of the macroscopic structure on fracture parameters to effectively simulate fracture patterns and connectivities around subsurface structures

coupled molybdenum iron and uranium stable isotopes as oceanic paleoredox proxies during the paleoproterozoic shunga event the paleoproterozoic era was a time of remarkable importance in the redox evolution of earth s atmosphere and oceans here we present a multi proxy study of mo u and fe isotopes together with fe speciation of black shales and siltstones from the upper zaonega formation of the onega basin in karelia we attempt to better understand oceanic redox conditions during the 2 05 ga shunga event as the next step following the great oxidation event goe and the lomagundi carbon isotope excursion event a cautious examination of the fe speciation data shows that the studied section was deposited under dominantly euxinic conditions anoxic and sulfidic and that the lower part of the section experienced metamorphism through which pyrite was altered to pyrrhotite during this episode the system was closed with respect to fe but not sulfur the mo and u isotopic compositions corrected for detrital input were not affected by the metamorphism and loss of s and are fairly uniform throughout the entire section the fe isotope compositions are exceptionally heavy in the lower part of the section up to 56 fe irmm 14 0 83 and become lighter towards the upper intervals which also show significant mo and u enrichments we suggest that this pattern reflects changes in the position of the deposition site relative to the redox structure of the water column the upper part was deposited within a locally euxinic portion of the basin where h 2s availability was highest removal of mo and u was more efficient and precipitated pyrite captured relatively non fractionated dissolved fe in other words quantitative uptake of fe was favored in contrast the lower interval was deposited on the lower margin of a euxinic wedge where h 2s availability was lower and removal of mo and u was less efficient pyrite precipitation in this part of the water column reflected a more fractionated dissolved fe reservoir due to more protracted non quantitative fe uptake because of less efficient pyrite formation under lower sulfide conditions and greater access to the large oceanic pool of fe the u isotopic signal was corrected for detrital contribution giving compositions similar to the riverine input and suggesting that co precipitation into carbonates was the main process of u removal at this time we estimate the mo isotope composition of the contemporaneous ocean to be 98 mo sw 0 85 0 21 this is the lowest value yet reported for the proterozoic ocean suggesting that the oceanic mo cycle was dominated by euxinic and anoxic sinks with negligible mo removal into oxic environments recent studies have proposed a sharp increase in ocean atmosphere oxygen levels during the lomagundi event followed by a dramatic crash our results from black shales of the 2 05 ga shunga event are consistent with a post lomagundi decrease in biospheric oxygen levels

hydraulic fracturing in unconventional gas reservoirs risks in the geological system part 2 hydraulic fracturing is a method used for the production of unconventional gas resources huge amounts of so called fracturing fluid 10 000 20 000 m3 are injected into a gas reservoir to create fractures in solid rock formations upon which mobilised methane fills the pore space and the fracturing fluid is withdrawn hydraulic fracturing may pose a threat to groundwater resources if fracturing fluid or brine can migrate through fault zones into shallow aquifers diffuse methane emissions from the gas reservoir may not only contaminate shallow groundwater aquifers but also escape into the atmosphere where methane acts as a greenhouse gas the working group risks in the geological system as part of exxonmobil s hydrofracking dialogue and information dissemination processes was tasked with the assessment of possible hazards posed by migrating fluids as a result of hydraulic fracturing activities in this work several flow paths for fracturing fluid brine and methane are identified and scenarios are set up to qualitatively estimate under what circumstances these fluids would leak into shallower layers the parametrisation for potential hydraulic fracturing sites in north rhine westphalia and lower saxony both in germany is derived from literature using upper and lower bounds of hydraulic parameters the results show that a significant fluid migration is only possible if a combination of several conservative assumptions is met by a scenario

caledonian deformation upon southwest baltica and its tectonic implications alternatives and consequences the continuation of the basement of the southwestern baltic shield toward the sw is of major interest for the caledonian evolution in the southwestern baltic sea and northern germany a reinterpretation of various marine seismic data suggests a reconsideration of the caledonian collision pattern the sorgenfrei tornquist zone forming the northwestern extension of the tornquist zone is regarded as the northeasterly boundary fault and the elbe lineament is regarded as the southwestern limit of an area which suffered from the docking of east avalonia to baltica it shows many northwestsoutheast striking structures anomalies and fault patterns from our studies two alternative models emerge one which considers the caledonian deformation front as the northeastern limit of east avalonia and a zone of major transpression collision and subduction of the tornquist sea another model considers the elbe lineament in schleswig holstein nw germany as a major dextral strike slip fault which is interpreted as the northeasterly limit of east avalonia and the southwest boundary of the baltic shield along the elbe lineament the tornquist sea plus rotating avalonia were displaced to the northwest a large part of the area to be studied might have developed into a passive margin toward the upper ordovician a decision which of the two models is to be prefered has to be the major goal of future geophysical experiments

statistical mechanics and scaling of fault populations with increasing strain in the corinth rift scaling properties of fracture fault systems are studied in order to characterize the mechanical properties of rocks and to provide insight into the mechanisms that govern fault growth a comprehensive image of the fault network in the corinth rift greece obtained through numerous field studies and marine geophysical surveys allows for the first time such a study over the entire area of the rift we compile a detailed fault map of the area and analyze the scaling properties of fault trace lengths by using a statistical mechanics model derived in the framework of generalized statistical mechanics and associated maximum entropy principle by using this framework a range of asymptotic power law to exponential like distributions are derived that can well describe the observed scaling patterns of fault trace lengths in the rift systematic variations and in particular a transition from asymptotic power law to exponential like scaling are observed to be a function of increasing strain in distinct strain regimes in the rift providing quantitative evidence for such crustal processes in a single tectonic setting these results indicate the organization of the fault system as a function of brittle strain in the earth s crust and suggest there are different mechanisms for fault growth in the distinct parts of the rift in addition other factors such as fault interactions and the thickness of the brittle layer affect how the fault system evolves in time the results suggest that regional strain fault interactions and the boundary condition of the brittle layer may control fault growth and the fault network evolution in the corinth rift

the influence of pressure on petroleum generation and maturation as suggested by aqueous pyrolysis because fluid pressures are transient in sedimentary basins over geologic time the effect of increasing fluid pressure on organic matter metamorphism is difficult to determine and conflicting opinions exist concerning its influence properly performed aqueous pyrolysis experiments can closely simulate hydrocarbon generation and maturation in nature and thus offer an excellent way to study the influence of pressure such experiments carried out on the retort phosphatic shale member of the lower permian phosphoria formation type ii s organic matter at different constant temperatures demonstrated that increasing pressure significantly retards all aspects of organic matter metamorphism including hydrocarbon generation maturation and thermal destruction this conclusion results from detailed quantitative and qualitative analyses of all products from hydrocarbon generation from the c1 to c4 hydrocarbon gases to the asphaltenes and also from analyses of the reacted rocks we have documented that our aqueous pyrolysis experiments closely simulated natural hydrocarbon generation and maturation thus the data taken as a function of pressure have relevance to the influence of normal and abnormal fluid pressures as related to 1 depths and temperatures of mainstage hydrocarbon generation 2 the thermal destruction of deposits of gas or light oil or their preservation to unexpectedly high maturation ranks and 3 the persistence of measurable to moderate concentrations of c15 hydrocarbons in fine grained rocks even to ultra high maturation ranks

numerical experiments on permeability tensor and its application to jointed granite at stripa mine sweden rock masses containing a large number of geological discontinuities called joints are treated as homogeneous anisotropic porous media a permeability tensor hydraulically equivalent to a flow network formed by joints is formulated in terms of two tensors and a nondimensional scalar both depending only on the geometrical aspects of joints such as the spacing size orientation and aperture two dimensional numerical analyses on seepage flow through the networks support the validity of the present theory the information about the geometry of joints which is obtained from the ventilation drift at stripa mine sweden is interpreted to give the corresponding permeability tensor the permeability tensor is compared with the result of the large scale hydraulic conductivity test with the conclusion that it provides a reasonable prediction for the hydraulic properties of stripa jointed granite

study on three dimensional fracture network connectivity path of rock mass and seepage characteristics based on equivalent pipe network nuclear waste repositories have extremely stringent requirements for geological environment however natural fractures in rock mass can be potential channels for nuclide migration therefore the influence of fractures on the permeability of rock mass must be assessed in this paper a well research was conducted on well exposed granite outcrops in the xinchang site the chinese high level radioactive waste repository the high precision three dimensional model of a typical outcrop is built to obtain fracture information combined with field measurement and then the three dimensional fracture network model is generated using the relevant parameters by monte carlo method to obtain more comprehensive fracture connectivity while avoiding the traditional method of searching the connectivity path in the complicated 3d fracture model taking up a lot of storage space and costing a lot of time this paper presents an approach using matlab cell array instead of traditional adjacency matrix to search and store fracture network connectivity paths in dfn model the fracture disc with certain thickness is equivalent to three dimensional pipe network model epnm with variable diameter and the equivalent path permeability coefficient epc is proposed to objectively study the permeability characteristics of the seepage path in fractured rock mass based on that especially noteworthy is that some fractures in a certain strike range belong to open type while those in another range belong to cemented closed fractures when fresh fractures were exposed by cutting off the surface rock to a certain depth the calculation of epc under different conditions shows that the order of magnitude of epc mean value is 1e 7m s and 1e 3m s respectively when fractures are cemented and not partly on this basis the size of the representative elementary volume rev of the fractured rock mass in the study area is determined to be about 25 m by rotating the matrix in model the spatial permeability tensor of the region including permeability principal value and main direction is obtained which is within the range of borehole data the predicted results may provide some reference for the related projects in the future

arctic sea ice leads from advanced very high resolution radiometer images a large number of advanced very high resolution radiometer avhrr images from throughout 1989 are analyzed to determine lead characteristics the units of analysis are square 200 km cells and there are 270 such cells in the data set clouds are masked manually leads are determined from images of the potential open water a scaled version of the surface temperature or albedo that weights thin ice by its thermal or brightness impact the lead fraction is determined as the mean the monthly mean lead fraction ranges from 0 02 in winter to 0 06 in summer in the central arctic and is near 0 08 in the winter in the peripheral seas a method of accounting for lead width sampling errors due to the finite sample areas is introduced in the central arctic the observed mean lead width for a threshold of 0 1 ranges from 2 or 3 km near the resolution of the instrument in the winter to 6 km in the summer in the peripheral seas it is about 5 km in the winter width distributions are often more heavily weighted in the tail than exponential distributions and are well approximated by a power law the along track number density power law n aw b has a mean exponent of b 1 60 standard deviation 0 18 and shows some seasonal variability mean floe widths in the central arctic are 40 to 50 km in the winter dropping to about 10 km in the summer for floes the power law has a mean exponent of 0 93 and exhibits a clearer annual cycle lead orientation is determined with a method based on the direction of maximum extent

polonaise 97 an international seismic experiment between precambrian and variscan europe in poland abstract the trans european suture zone tesz comprises a series of sutures that developed by palaeozoic amalgamation of the phanerozoic central europe onto the proterozoic baltica and east european plate during the formation of pangea within tesz the permian basin in poland forms the easternmost part of the permian central european basin which is bordered on the east by the east european craton eec and on the southwest by the bohemian massif the axis of the basin the mid polish trough parallels the edge of the eec the teisseyre tornquist zone ttz is a geological inversion zone in the polish trough a large seismic experiment the polonaise 97 project was conducted in poland during may of 1997 and targeted the deep structure of the tesz and the complex series of upper crustal features associated with it it included contributions from the geophysical communities in poland denmark the usa lithuania germany finland sweden and canada this large lithospheric seismic experiment deployed 613 instruments to record 64 shots along five profiles with a total length of about 2000 km moreover five multichannel seismic reflection stations 90 and 120 channels recorded all signals from shots two dimensional velocity models were derived by p wave tomographic inversion these models provide an initial interpretation of this massive data set and allow us to present a few significant seismic and tectonic observations one of the most important is a very distinct asymmetry between the maximum thickness of the sedimentary cover in the polish trough 16 20 km and the crustal root 50 km associated with tesz ttz

scaling relationships of joint and vein arrays from the burren co clare ireland abstract we present a study of the systematics of veins and joints in carboniferous limestones of the burren ireland scaling relationships were established for fracture arrays mapped from low elevation aerial photographs that image fractures on numerous limestone pavements for areas up to ca 1 km2 the veins and joints occur in the same sequence but have contrasting scaling properties the veins strike north south and cut many beds to form vertically persistent non stratabound arrays they are strongly clustered and have scale invariant geometric properties vein geometries suggest they grew sub critically under relatively high differential stresses during north south directed variscan compression the joints form stratabound arrays with regular spacings that scale with bed thickness they show greater strike variation than the veins and have lognormal length distributions the joints formed during uplift under low differential stress conditions the contrasting scaling properties of the joints and veins are attributed to different overburden stresses at the time of formation the veins formed at greater depths than the joints in conditions that favoured fracture propagation across mechanical discontinuities resulting in the development of non stratabound scaling properties

scaling and geometric properties of extensional fracture systems in the proterozoic basement of yemen tectonic interpretation and fluid flow implications abstract multi scale mappings of fracture systems in the crystalline basement of yemen are presented fracture datasets are described through statistical analyses of direction length spacing density and spatial distribution results are combined with field observations and can be directly used to model the geometry of the fracture networks in analog basement rocks from multi kilometric to decametric scales the fractured reservoir analog is defined with a dual porosity model in which tectonic and joint systems correspond to the basement reservoir backbone and matrix respectively these two end members reveal contrasting geometrical reservoir and scaling properties in tectonic systems multi scale geometries are self similar the fracture network shows fractal behavior power law length distribution and clustered spacing and fault zones show hierarchical organization of geometrical parameters such as length thickness and spacing in joint systems the fracture network is scale dependent with exponential length distribution and shows anti clustered spacing however these two end members have both well connected properties with fault zones acting as main drain and joint systems acting as the fluid supply

inversion related features along the southeastern margin of the north german basin elbe fault system abstract a seismostratigraphic approach constrained by well data is used for the interpretation of the deformation style along the central elbe fault system efs within the sedimentary succession structural analysis allows to qualify to quantify and to date tectonic events the stratigraphic interpretation is complicated by the mobilized upper permian zechstein salt and by erosional events a first order quantification of the inversion related uplift is estimated from vertical fault offsets that reach up to 4 km the main uplift occurred during the maastrichtian paleocene amounts of erosion inferred from comparing the strata thickness on top of the flechtingen high with the surrounding basinal areas range from 3 to 4 km the data indicate a changing deformation style thick skinned deformation with southwest dipping thrusts that vertically offset the pre permian basement is observed along the flechtingen high in the central part of the efs thin skinned deformation occurs in the north german basin where salt detaches the post permian cover from the barely faulted basement it is concluded that during the late cretaceous early tertiary inversion the efs responded to regional compression with uplift and formation of an internal high the flechtingen high a stress sensitive crustal weak zone beneath the efs could be the reason for the repeated strain localization in the area

the southern margin of the east european craton new results from seismic sounding and potential fields between the north sea and poland abstract the extension of eastern avalonia from britain through the ne german basin into poland is in some sense a virtual structure it is covered almost everywhere by late paleozoic and younger sediments evidence for this terrane is only gathered from geophysical data and age information derived from magmatic rocks during the last two decades much geophysical and geological information has been gathered since the european geotraverse egt which was followed by the babel lt 7 mona lisa dekorp basin 96 and polonaise 97 deep seismic experiments based on seismic lines a remarkable feature has been observed between the north sea and poland north of the elbe line el the lower crust is characterised by high velocities 6 8 7 0 km s a feature which seems to be characteristic for at least a major part of eastern avalonia far eastern avalonia in addition the seismic lines indicate that a wedge of the east european craton eec or baltica continues to the south below the southern permian basin spb a structure which resembles a passive continental margin the observed pattern may either indicate an extension of the baltic crust much farther south than earlier expected or oceanic crust of the tornquist sea trapped during the caledonian collision in either case the data require a reinterpretation of the docking mechanism of eastern avalonia and the elbe odra line eol as well as the elbe fault system together with the intra sudedic faults appear to be related to major changes in the deeper crustal structures separating the east european crust from the paleozoic agglomeration of middle european terranes

moho topography and lower crustal wide angle reflectivity around the tesz in southern scandinavia and northeastern europe abstract the moho topography is strongly undulating in southern scandinavia and northeastern europe a map of the depth to moho shows similarities between the areas of the teisseyre tornquist zone ttz in poland and the fennoscandian border zone fbz which is partly coinciding with the sorgenfrei tornquist zone stz in denmark the moho is steeply dipping at these zones from a crustal thickness of approximately 32 km in the young palaeozoic platform and basin areas to approximately 45 km in the old precambrian platform and baltic shield the moho reflectivity pmp waveform in the polonaise 97 refraction wide angle seismic data from poland and lithuania is variable ranging from sharp to strongly reverberating signals of up to 2 s duration there is little or no lower crustal wide angle reflectivity in the thick precambrian platform whereas lower crustal reflectivity in the thin palaeozoic platform is strongly reverberating suggesting that the reflective lower crust and upper mantle is a young phenomena from stochastic reflectivity modelling we conclude that alternating high and low velocity layers with average thicknesses of 50 300 m and p wave velocity variations of 3 4 of the background velocity can explain the lower crustal reflectivity sedimentary layering affects the reflectivity of deeper layers significantly and must be considered in reflectivity studies although the reverberations from the deeper crust cannot be explained by the sedimentary layering only the reflective lower crust and upper mantle may correspond to a zone that has been intruded by mafic melts from the mantle during crustal extension and volcanism

deep seismic expression of an ancient plate boundary in europe seismological results on the structure of the upper mantle below europe reveal a marked contrast in seismic properties between precambrian and younger parts of europe the precambrian craton in eastern europe is characterized by high shear wave velocities which can be explained by low temperatures the transition to low seismic velocities below phanerozoic europe coincides with the crustal boundary zone of the craton and exists to depths of at least 140 kilometers despite the long and complex tectonic history of the plate boundary zone the transition is remarkably sharp which rules out any significant lateral transport of asthenospheric material across the suture zone

development of framboidal pyrite during diagenesis low grade regional metamorphism and hydrothermal alteration distribution patterns microstructural relationships and compositional variations for framboidal pyrite in the paleozoic sedimentary host rocks to gold deposits on the northern carlin trend nevada and at fosterville in central victoria collectively demonstrate that it is not all of synsedimentary early diagenetic origin framboidal pyrite also nucleated in hydrothermal veins formed at several kilometers depth and along dissolution surfaces stylolites and crenulation cleavages formed during metamorphism at up to anchizonal grade i e prehnitepumpellyite facies there are no obvious differences in either the size range or internal morphology of framboids formed in these various settings suggesting that a single relatively simple crystallization path may operate over a wide depth range in the upper crust at fosterville anomalously metal rich including au framboidal pyrite is most abundant adjacent to laminated shear veins that developed by slip along bedding surfaces during folding of the sedimentary host rocks microstructural relationships and pb isotope compositions for the framboidal pyrite and other similarly distributed early formed sulfides support development in response to the localized episodic influx of metal enriched h 2s bearing hydrothermal fluids during regional deformation between 440 and 400 ma these findings may have implications for other similarly deformed metasedimentary successions where the discovery of au bearing framboidal pyrite has recently been cited as evidence for significant au enrichment during sedimentation 2009 society of economic geologists inc

evolution of permeability in sand injectite systems abstract sand injectite complexes comprise kilometer scale clastic intrusion networks that act as effective conduits for the migration accumulation and then recovery of hydrocarbons and other fluids an equivalent continuum model is constructed to represent a sand injectite reservoir coupling stress and fluid flow in fractured rock using the continuum simulator toughreact coupled with flac3d to follow deformation and fluid flow a permeability model which uses staged percolation models is proposed to improve permeability estimation of fracture networks by accommodating four different levels of fracture connectivity this permeability model is confirmed against field and laboratory data corresponding to the different connectivities of fracture networks the new constitutive permeability model is incorporated into the coupled hydro mechanical simulator framework and applied to sand injectites with the analysis of permeability evolution mechanisms and mechanical sensitivity the results indicate that when the magnitudes of principal stresses increase in a constant ratio normal closure is the dominant mechanism in reducing fracture aperture and thereby permeability conversely the evolution of stress difference can accentuate aperture and permeability due to an increase in shear dilation for critically or near critically oriented fractures also the evolution of aperture and related permeability of fractured rock are more sensitive at lower stress states than at higher stress states due to the hyperbolic relationship between normal stress and normal closure of the fractures

a seismic velocity model for the sw baltic sea derived from basin 96 refraction seismic data abstract within the basin 96 project basin analysis and seismic investigation in north germany 1996 a marine survey gathered seismic data in the southwest baltic sea to study the caledonian collisional zone between baltica to the north and avalonia to the south additionally the airgun pulses have been observed by several land stations special attention was paid to record good quality data on rugen island aiming at linking offshore and land seismic wide angle observations therefore a complex geophone array the star of rugen was designed to enhance the signal quality the star of rugen data and other onshore observations in ne germany and on bornholm an island in the baltic sea have been used for p wave velocity modelling important structures of the transition zone from palaeozoic western europe to the precambrian baltic shield are imaged in the resulting three dimensional velocity model a pronounced basement high north of rugen island indicates the location of the caledonian deformation front cdf velocities also reflect other prominent features such as the ronne graben a pull apart structure of the tornquist zone and the basement outcrops around bornholm island in the investigated area the moho depth varies between 27 and 33 km a high velocity layer in the lower crust below the ne german mainland may indicate genetic relations to baltica the structural continuity however is disturbed by a velocity decrease in an area north of the cdf sporadic but strong reflections from the upper mantle below the cdf seem to be consistent with the reflection seismic data dekorp basin research group 1999 geology 27 1 55 58