a pseudo genetic stochastic model to generate karstic networks summary in this paper we present a methodology for the stochastic simulation of 3d karstic conduits accounting for conceptual knowledge about the speleogenesis processes and accounting for a wide variety of field measurements the methodology consists of four main steps first a 3d geological model of the region is built the second step consists in the stochastic modeling of the internal heterogeneity of the karst formations e g initial fracturation bedding planes inception horizons etc then a study of the regional hydrology hydrogeology is conducted to identify the potential inlets and outlets of the system the base levels and the possibility of having different phases of karstification the last step consists in generating the conduits in an iterative manner using a fast marching algorithm in most of these steps a probabilistic model can be used to represent the degree of knowledge available and the remaining uncertainty depending on the data at hand the conduits are assumed to follow minimum effort paths in a heterogeneous medium from sinkholes or dolines toward springs the search of the shortest path is performed using a fast marching algorithm this process can be iterative allowing to account for the presence of already simulated conduits and to produce a hierarchical network the final result is a stochastic ensemble of 3d karst reservoir models that are all constrained by the regional geology the local heterogeneities and the regional flow conditions these networks can then be used to simulate flow and transport several levels of uncertainty can be considered large scale geological structures local heterogeneity position of possible inlets and outlets phases of karstification compared to other techniques this method is fast to account for the main factors controlling the 3d geometry of the network and to allow conditioning from available field observations

molecular and isotopic compositions and origin of natural gases from cambrian and carboniferous lower permian reservoirs of the onshore polish baltic region natural gases from middle cambrian and carboniferous lower permian reservoirs of the onshore polish baltic region were studied for their molecular and stable isotope compositions the following gas species were analysed 12 13c in ch4 c2h6 c3h8 n c4h10 i c4h10 and co2 1 2h in ch4 14 15n in n2 and stable isotopes of all noble gases due to significantly different geological settings and genetic types of source rocks of eastern and western pomerania the molecular and isotopic compositions of natural gases of these two regions exhibit distinct differences hydrocarbon gases associated with oil accumulated in the middle cambrian reservoir of eastern pomerania were generated during low temperature thermogenic processes from a single source rock containing type ii kerogen at one phase of petroleum generation non associated hydrocarbon gases accumulated in the carboniferous mississippian and pennsylvanian lower permian rotliegend reservoirs of western pomerania originated during at least two phases of gas generation by thermogenic processes from mainly type iii kerogen and a small component of mixed type iii ii kerogen noble gases are in general heavily enriched in radiogenic and nucleogenic isotopes such as 4he 40ar and 21ne accumulated in the reservoirs weak contributions of mantle derived he and ne are observed radiogenic 4he 40ar ratios are higher than the average production rate ratio of about 5 for radiogenic 4he 40ar in crustal materials which might have been caused by a selective supply of 4he that is lighter than 40ar from crustal rocks or u th k ratio might be higher than the average in crustal block carbon dioxide from gases of both the western and eastern pomerania were mainly generated during thermogenic processes of transformation of organic matter although gases of western pomerania can contain an endogenic component molecular nitrogen from the eastern pomeranian natural gases was mainly generated during low temperature thermal transformation of organic matter and derived from nh3 and nh4 of crustal fluid whereas molecular nitrogen from western pomeranian natural gases contains a significant component from the destruction of organic matter at a higher maturity level which may have been caused by a high heat flux from the volcanic activity during late pennsylvanian early rotliegend ages and has a bigger component release from nh4 rich illites

composition and origin of natural gases accumulated in the polish and ukrainian parts of the carpathian region gaseous hydrocarbons noble gases carbon dioxide and nitrogen abstract ten natural gas samples associated and non associated with oil in the polish and ukrainian flysch carpathians and mesozoic basement of the carpathian foredeep were analysed for molecular and stable isotope compositions as follows 12 13c in ch4 c2h6 c3h8 and co2 1 2h in ch4 14 15n in n2 and 3 4he 20 21 22ne 36 38 40ar 84kr and 132xe in noble gases the gaseous hydrocarbons both in the silesian unit of the outer flysch carpathians and mesozoic basement are generally genetically related to thermogenic processes and occasionally to microbial carbon dioxide reduction these gases were mainly generated from mixed type ii iii kerogen during middle stage of the low temperature thermogenic processes gaseous hydrocarbons from starunia in the boryslav pokuttya unit were generated from type ii kerogen during middle stage of the low temperature thermogenic processes he is generally of crustal origin with more than 99 2 of radiogenic 4he but appreciable amount of 3he is probably derived from the upper mantle the 3he might have been derived from the pieniny klippen belt deep seated fault system or neogene and pleistocene andesitic and basaltic volcanism occurred in the eastern carpathian area nucleogenic 21ne and 22ne were analysed in all the samples the nucleogenic 21ne shows good correlation with radiogenic 4he with the production ratio of 4he 21ne 1 3 107 in the crust these isotopic values indicate a common source for these gases where both the nuclear reactions of decay and n are occurring concentrations of radiogenic 4he and 40ar and excess 21ne in the samples from the mesozoic basement are generally higher and more scattered compared with those in the silesian unit the larger concentrations of radiogenic and nucleogenic isotopes in the natural gases from the mesozoic basement is probably related to older geological formations than younger formations of the silesian unit carbon dioxide was generally generated during the thermal transformation of organic matter and occasionally during microbial processes nitrogen was mainly generated during thermal transformation of organic matter and also originated from atmosphere a least part of carbon dioxide and nitrogen may have been produced in crust

hydraulic tests in highly permeable aquifers 1 a semianalytical solution is presented for a mathematical model describing the flow of groundwater in response to a slug or pumping test in a highly permeable confined aquifer this solution which is appropriate for wells of any degree of penetration and incorporates inertial mechanisms at both the test and observation wells can be used to gain new insights into hydraulic tests in highly permeable settings the oscillatory character of slug and pumping induced responses will vary considerably across a site even in an essentially homogeneous formation when wells of different radii depths and screen lengths are used thus variations in the oscillatory character of responses do not necessarily indicate variations in hydraulic conductivity k existing models for slug tests in partially penetrating wells in high k aquifers neglect the storage properties of the media that assumption however appears reasonable for a wide range of common conditions unlike in less permeable formations drawdown at an observation well in a high k aquifer will be affected by head losses in the pumping well those losses which affect the form of the pumping induced oscillations can be difficult to characterize thus analyses of observation well drawdown should utilize data from the period after the oscillations have dissipated whenever possible although inertial mechanisms can have a large impact on early time drawdown that impact decreases rapidly with duration of pumping and distance to the observation well conventional methods that do not consider inertial mechanisms should therefore be viable options for the analysis of drawdown data at moderate to large times

composition and stable isotope geochemistry of natural gases from kansas midcontinent u s a abstract more than 28 1012 ft 3 79 1010 m3 of natural gas and 5 3 109 bbl 8 4 108 m3 of oil have been produced in kansas u s a from paleozoic carbonate and sandstone reservoirs on structural uplifts and shallow embayments along the northern margin of the anadarko basin a heavily explored geologically well characterized state kansas is an excellent place to study hydrocarbon migration and to test geochemical models for the origin of natural gases immature to marginally mature rocks of eastern kansas cherokee and forest city basins produce mixed microbial and thermogenic gases gases in this region have wetness 0 03 51 methane 13c 65 to 43 and methane d 260 to 150 gases from central and western kansas nemaha uplift to hugoton embayment are entirely thermogenic and have wetness 4 51 methane 13c 48 to 39 and methane d 195 to 140 ethane and propane 13c values throughout kansas vary from 38 to 28 and from 35 to 24 respectively mature thermogenic gas generated from source rocks in southwestern kansas and the anadarko basin with 1 0 ro 1 4 is recognized throughout the state lateral migration into shallow reservoirs on the central kansas and northern nemaha uplifts and in the cherokee basin probably occurred along basal pennsylvanian conglomerates and weathered lower paleozoic carbonates at the regional sub pennsylvanian unconformity early thermogenic gas generated by local source rocks with ro 0 7 is recognized in isolated fields in the salina and forest city basins in ordovician reservoirs beneath the sub pennsylvanian unconformity in the cherokee basin and in reservoirs generally above the unconformity in the cherokee and sedgwick basins the eastern central kansas uplift and the hugoton embayment

cross borehole slug test analysis in a fractured limestone aquifer summary this work proposes new semi analytical solutions for the interpretation of cross borehole slug tests in fractured media our model is an extension of a previous work by barker barker j a 1988 a generalized radial flow model for hydraulic tests in fractured rock water resources research 24 10 1796 1804 butler jr j j zhan x 2004 hydraulic tests in highly permeable aquifers water resources research 40 w12402 doi 10 1029 2003 wr002998 it includes inertial effects at both test and observation wells and a fractional flow dimension in the aquifer the model has five fitting parameters flow dimension n hydraulic conductivity k specific storage coefficient ss and effective lengths of test well le and of observation well leo the results of a sensitivity analysis show that the most sensitive parameter is the flow dimension n the model sensitivity to other parameters may be ranked as follows k le leo ss the sensitivity to aquifer storage remains one or two orders of magnitude lower than that to other parameters the model has been coupled to an automatic inversion algorithm for facilitating the interpretation of real field data this inversion algorithm is based on a gauss newton optimization procedure conditioned by re scaled sensitivities it has been used to interpret successfully cross borehole slug test data from the hydrogeological experimental site hes of poitiers france consisting of fractured and karstic limestones hes data provide flow dimension values ranging between 1 6 and 2 5 and hydraulic conductivity values ranging between 4 4 10 5 and 7 7 10 4 m s 1 these values are consistent with previous interpretations of single well slug tests the results of the sensitivity analysis are confirmed by calculations of relative errors on parameter estimates which show that accuracy on n and k is below 20 and that on ss is about one order of magnitude the k values interpreted from cross borehole slug tests are one order of magnitude higher than those previously interpreted from interference pumping tests these findings suggest that cross borehole slug tests focus on preferential flowpath networks made by fractures and karstic channels i e the head perturbation induced by a slug test propagates only through those flowpaths with the lowest hydraulic resistance as a result cross borehole slug tests are expected to identify the hydrodynamic properties of karstic channels and fracture flowpaths and may be considered as complementary to pumping tests which more likely provide bulk properties of the whole fracture karstic channel matrix system

modeling the effect of clay drapes on pumping test response in a cross bedded aquifer using multiple point geostatistics this study investigates whether small scale clay d rapes can cause an anisotropic groundwater pumping test response at a much larger scale the measured drawdown values from a pumping test in the cross bedded brussels sands aquifer belgium reveal an elliptical shaped pumping cone the major axis of the pumping ellipse is parallel with the strike of small scale clay drapes that are observed and measured in several outcrops this stu dy investigates 1 whether this large scale anisotropy can be the result of sm all scale clay drapes and 2 whether application of multiple point geostatistics can improve the analysis of pumping tests this study uses the technique of di rect multiple point geostatistical simulation of edge properties which enables simulating thin irregularly shaped surfaces with a smaller cpu and ram demand than the conventional multiple point statistical methods th e proposed method uses model cell edge properties for indicating the presence of thin irregularly shaped surfaces instead of pixel values model cell edge properties such as edge transmissibility indicating the presence of irregularly shaped surfa ces are simulated using the multiple point geostatistical algorithm snesim the modelling strategy of this study consists of the following steps first a tra ining image displaying clay drape occurence is constructed secondly this small grid cell size training image is converted into an upscaled edge training image whic h is used as input training image to perform snesim simulations the resulting simulations indicate at which cell edges horizontal or vertical clay drapes are present this information is incorporated in a local 3d groundwater model of the pumping test site by locally adapting vertical leakance values and by locally in serting horizontal flow barriers all hydraulic parameters including the clay drapes properties are calibrated using the measured drawdown time series in six observatio n wells results show that the anisotropic pumping cone can be attributed to the p resence of the clay drapes

a new method of data inversion for the identification of fractal characteristics and homogenization scale from hydraulic pumping tests in fractured aquifers hydraulic interference pumping tests are widely used for identifying mid to large scale aquifer hydraulic parameters fractured reservoirs often behave as fractal media for which classical interpretations may fail because of the decrease in permeability and fracture porosity or equivalently transmissivity and storage capacity with the pumping time and the extent over which the pumping stress has propagated a solution to hydraulic interference tests in fractal media is developed in dimensional variables which allows for a very rapid and unique fitting to data hydraulic parameters their scale exponents and the fractal dimension of the medium can be determined for each pressure draw down curve without any prior information or other calculation the method is applied to a large series of tests completed on the calcareous fractured aquifer of the experimental site in poitiers france even though data of pressure draw downs are various and show a fractal behavior permeability seems to rapidly homogenize for distances of 100 200 m on the other hand the fracture porosity shows a much progressive decrease with distance and homogenization is reached for scales beyond 300 500 m it is also shown that the classical cooper jacob interpretation of pressure draw downs may yield artifacts in the identification of permeability and fracture porosity orders of magnitude are comparable to that from fractal interpretation but their evolution with respect to time or distance scaling laws may strongly differ

karst aquifer evolution in fractured porous rocks the evolution of flow in a fractured porous karst aquifer is studied by means of the finite element method on a two dimensional mesh of irregularly spaced nodal points flow within the karst aquifer is driven by surface recharge from the entire region simulating a precipitation pattern and is directed toward an entrenched river as a base level during the early phase of karstification both the permeable rock matrix modeled as triangular elements and fractures within the rock matrix modeled as linear elements carry the flow as the fractures are enlarged with time by chemical dissolution within the system calcite carbon dioxide water flow becomes more confined to the fractures this selective enlargement of fractures increases the fracture conductivity by several orders of magnitude during the early phase of karstification thus flow characteristics change from more homogeneous pore controlled flow to strongly heterogeneous fracture controlled flow we study several scenarios for pure limestone aquifers mixed sandstone limestone aquifers and various surface recharge conditions as well as the effect of faulting on the aquifer evolution our results are sensitive to initial fracture width faulting of the region and recharge rate

improving dual porosity medium approaches to account for karstic flow in a fractured limestone application to the automatic inversion of hydraulic interference tests hydrogeological experimental site hes poitiers france a reassessment improvement of a previous work by the authors is proposed on the inversion of hydraulic interference testing by means of dual porosity medium approaches the tests have been performed over a fractured limestone aquifer poitiers france showing a preferential and rapid flow path along open karstic drains all drawdown curves are merged together both in amplitude and time irrespective of their location relative to the single pumped well and classical dual porosity medium approaches are unable to mimic this behavior a pressure wave propagation by advection is added to the classical diffusion equations of dual porosity medium in order to stress the medium almost evenly whatever the distance from the pumped well the problem is set up to keep the continuous dual porosity medium framework with only two state variables i e the heads in fractures and matrix even though the wave velocity is not well conditioned because the ratio of the volume of drains to the total volume of the medium is unknown automatic inversion remains feasible the dual porosity medium without the drains can be homogeneous or fractal having in the latter case hydraulic parameters ruled by scaling power laws in both cases it is shown that adding an advection term allows to invert accurately all experimental drawdown curves statistical fluctuations of the sought hydraulic parameters are quite small and do not show any trend with respect to the distance thus modifying a dual porosity medium approach by adding an advection term allows for the homogenization of a reservoir that combines the general drainage of a fracture matrix system and a rapid drainage through karstic conduits

bayesian inversion with total variation prior for discrete geologic structure identification 1 the characterization of geologic heterogeneity that affects flow and transport phenomena in the subsurface is essential for cost effective and reliable decision making in applications such as groundwater supply and contaminant cleanup in the last decades geostatistical inversion approaches have been widely used to tackle subsurface characterization problems and quantify their corresponding uncertainty some well established geostatistical methods use models that assume gradually varying parameters however in many cases the subsurface can often be better represented as consisting of a few relatively uniform geologic facies or zones with abrupt changes at their boundaries we advance a bayesian inversion approach with the gradient represented not through a gaussian but a laplace prior also known as total variation prior for the case that there are reasons to believe that discrete geologic structures with relatively homogeneous properties predominate in the subsurface but their number locations and shapes are unknown a priori structural parameters or hyperparameters of the inversion scheme are determined in a bayesian framework by maximizing the marginal distribution of these parameters using an expectation maximization approach this allows proper weighting of prior versus data information and produces results with realistic uncertainty quantification we present here three applications of the method a time varying extraction rate estimation at a well a linear cross well seismic tomography and a nonlinear hydraulic tomography these results are compared with those achieved in the classical geostatistical method and it is shown that the bayesian inversion approach with total variation prior can be a useful tool to identify discrete geologic structures

nitrogen in future biosphere studies this article suggests a theme for future nitrogen studies involving the functioning and evolution of the biosphere together with certain aspects of human biology it is hoped that this theme could be developed into a multi authored book at some point in the future although numerous new case studies may be required the biosphere can be considered to be a single interactive system comprised of numerous component parts including the atmosphere rain rivers lakes oceans continental ecosystems marine ecosystems soils and sediments in order to study the internal complexity of each of the components and the relationships that exist between them one can choose a common theme the author believes that nitrogen is a good prospect because of its ubiquitous nature and complex chemistry the burial of sedimentary volatiles in the continental crust has contributed to the long term chemical evolution of the exterior environments of the earth the most marked effects notably the accumulation of atmospheric oxygen have been due to the burial of reduced carbon an understanding of the passage of sedimentary volatiles through the crust will provide important constraints on the evolution of the biosphere and may lead to a more meaningful comparative planetology carbon is difficult to trace through crustal processes because its high temperature form graphite is incompatible with the crystal structures of silicate minerals however the high temperature form of sedimentary nitrogen ammonium readily enters into potassic minerals and it can be easily traced through crustal processes herein the fate of sedimentary nitrogen is traced from wet sediments through metamorphic rocks into granites and other crustal melts without the trapping of nitrogen in the crust and the liberation of oxygen that is a consequence of biological nitrogen fixation the n2 o2 of the atmosphere may have been about 82 9 to 16 3 and the total atmospheric pressure about 1 2 atm most of the changes in the oxygen content is due to dilution by nitrogen with only about 5 of the present atmospheric oxygen being a consequence of nitrogen fixation the ancient continental surfaces would have been volcanic deserts containing little 1 ppm or no nitrogen today nitrogen rich soils support continental ecosystems one can use nitrogen as a window to speculate on the colonisation of the continents by land plants herein nitrogen fixation by legumes is considered in detail and by drawing analogies with the present day the author speculates on the colonisation of the continents by land plants having speculated on the co evolution of the atmosphere soils and continental ecosystems one can place a human being in the centre of a tropical forest and begin to examine how they relate to the modern biosphere the chosen example is the metabolism of plant protein and the roles of glutamate dehydrogenase gdh vitamin b2 and flavin mononucleotide fmn the realisation of this theme would imply numerous new case studies notably those concerning the continental crust where nitrogen studies were linked to mineralogy petrology and other geochemical tracers including sr o al and k and where the short range order of 15n were taken into consideration

sources and mechanisms of formation of gaseous hydrocarbons in sedimentary rocks abstract accepted concepts of principal stages of hydrocarbon formation fail to satisfactorily explain the accumulation of supergiant gasfields in west siberia u s s r such as for example urengoy which comprise 30 of the proven gas reserves of the world a new mathematical model has been developed which applies the concept of activation energy distribution to the formation of gases characteristic differences in the molecular structure of humic and sapropelic source organic matter are expressed in different activation energy distributions the model allows the calculation of isotope values for different types of organic matter and their dependence on maturity application of the model to west siberia suggests that the supergiant gas accumulations in urengoy are more likely formed from terrestrial organic matter through thermochemical reactions at moderate depths and are not the result of either deep overmature or bacteriogenic processes the new mathematical model suggests that humic organic matter in general has a high methane generating capacity at comparably low maturities of organic matter equivalent to 0 5 0 7 on the vitrinite reflectance scale

the significance of fixed ammonium in palaeozoic sediments for the generation of nitrogen rich natural gases in the north german basin in contrast to predominantly hydrocarbon rich natural gases in the western part of the central european basin ceb accumulations of natural gases from the eastern part of the north german basin ngb are nitrogen rich with up to 90 n2 this study is focused on the behaviour of fixed ammonium in clay minerals of organic rich palaeozoic sediments in the eastern part of the ngb as a major source of nitrogen rich natural gases carboniferous shales have been investigated for a better understanding of nitrogen fixing during diagenesis storage during burial and release during devolatilization processes or fluid rock interactions the total nitrogen contents in the studied carboniferous shales of the ngb reach up to 2700 ppm with an inorganic fixed portion in the form of nh4 n of more than 60 the results of this study indicate an increasing proportion of the mineralogically fixed ammonium with increasing thermal maturity and storage up to catagenetic conditions the isotopic composition of fixed nh4 is relatively homogeneous in the majority of the shales and ranges from 1 to 3 5 in contrast samples from the basin centre show a significant decrease in ammonium contents down to 460 ppm coupled with a shift in 15n up to 5 6 suggesting a release of nitrogen on a large scale calculation of nitrogen loss and isotopic fractionation indicate that more than 30 of nitrogen was released as ammonium probably as a consequence of fluid rock interaction with highly saline brines

on the use of apparent hydraulic diffusivity as an indicator of connectivity summary connectivity of high permeability paths is recognized as important but has not been properly quantified in the groundwater literature in fact it has been shown that the concept is process dependent and difficult to define so that it applies both to water flow and solute transport phenomena field and numerical evidence from hydraulic tests suggest that the apparent hydraulic diffusivity d a could potentially inform about the phenomena in order to test this conjecture we present a monte carlo analysis based on series of fields that display varying degrees of connectivity our results confirm that d a does indeed indicate the presence of connectivity d a is found to correlate well with early tracer arrival time and also with the product of a flow connectivity indicator cf and a transport connectivity indicator ct this indicates that d a accounts both for connectivity effects controlling the average plume movement through cf and for connectivity effects not linked to the effective medium properties that control the progression of the solute front through ct analysis of seven binary fields suggests that flow connectivity hinges more on the continuity of fast paths whereas transport connectivity seems to be more dependent on the width of connected features forming possibly discontinuous fast paths in conjunction with previous studies our results suggest that hydraulic response arrival times and early arrival times of tracer can be expected to correlate well in most types of hydrogeologic systems

paragenesis of fluids under evaporates in the volga ural basin abstract to unravel the mystery of the relationship between evaporates ca cl brines and accumulations of oil and n 2 in the basins of ancient cratons their n 2 ch 4 and he concentration ratios as well as the isotopic composition 15 n 13 c and 3 he 4 he were compared within the volga ural basin the study allowed subsalt fluids from volga ural basin to divide into two genetic groups the first one is found within the basin s platform area it includes ca cl brines high viscosity heavy oil bitumen and n 2 which has concentrations higher than that of ch 4 and positive values of 15 n the second one is tied to the edge of the platform the ural foredeep and peri caspian depression in this group only the oil and gas reservoirs which have more ch 4 than n 2 and possibly negative values of 15 n were discovered interaction of gas components in compared fluids indicates great role of degassing in the formation of their composition it is suggested that the fluids of the first group n 2 ch 4 is what remains and the second group n 2 4 is what is disappears from the rocks during their metamorphism and degassing

predictive modelling of hydraulic head responses to dipole flow experiments in a fractured karstified limestone aquifer insights from a comparison of five modelling approaches to real field experiments summary five modelling approaches were tested against a well studied limestone aquifer constituting the hydrogeological experimental site hes of poitiers france the modelling exercise consisted of predicting the drawdown responses of a series of observation wells for two dipole pumping injection flow experiments involving two distinct well pairs at the hes the differences between model predictions appear to be mainly related to the hydraulic datasets used for model parameterisation and to a much lesser extent to the conceptual modelling approach equivalent porous medium vs discrete fracture networks the model dimensionality two dimensional vs three dimensional and or the parameterisation approach forward vs inverse despite the abundance and diversity of calibration parameterisation data all of the models failed to predict the drawdowns with a reasonable degree of accuracy only the order of magnitude of the drawdowns was correctly predicted by three of the five models whereas all models failed to predict the drawdown behaviour at both intermediate and late times the primary source of error is attributed to a lack of information in the single well pumping test data which did not capture the multi permeability structure of the aquifer as revealed a posteriori by the responses to dipole flow experiments this highlights the need to develop novel or improved approaches to characterise the hydraulic properties of limestone aquifers

integrating deterministic lithostratigraphic models in stochastic realizations of subsurface heterogeneity impact on predictions of lithology hydraulic heads and groundwater fluxes realistic representations of geological complexity are important to address several engineering and environmental challenges the spatial distribution of properties controlling physical and geochemical processes can be effectively described by the geological structure of the subsurface in this work we present an approach to account for geological structure in geostatistical simulations of categorical variables the approach is based on the extraction of information from a deterministic conceptualization of the subsurface which is then used in the geostatistical analysis for the development of models of spatial correlation and as soft conditioning data the approach was tested to simulate the distribution of four lithofacies in highly heterolithic quaternary deposits a transition probability based stochastic model was implemented using hard borehole data and soft data extracted from a 3 d deterministic lithostratigraphic model simulated lithofacies distributions were also used as input in a flow model for numerical simulation of hydraulic head and groundwater flux the outputs from these models were compared to corresponding values from models based exclusively on borehole data results show that soft lithostratigraphic information increases the accuracy and reduces the uncertainty of these predictions the representation of the geological structure also allows a more precise definition of the spatial distribution of prediction uncertainty here quantified with a metric based on shannon information entropy correlations between prediction uncertainties for lithofacies hydraulic heads and groundwater fluxes were also investigated the results from this analysis provide useful insights about the incorporation of soft geological data into stochastic realizations of subsurface heterogeneity and emphasize the critical importance of this type of information for reducing the uncertainty of simulations considering flux dependent processes

detection of karst conduit patterns via hydraulic tomography a synthetic inverse modeling study abstract karst aquifers are geologic media that consist of enlarged solution conduits the geometry of such conduits is very difficult to delineate and its hydraulic parameters such as hydraulic conductivity k and specific storage ss are difficult to estimate hydraulic tomography ht shown to successfully map the hydraulic heterogeneity of porous and fractured rock aquifers may also be effective in karst aquifers in this study we utilize two synthetic karst aquifers with the branchwork and network conduit patterns bcp and ncp to explore the ability of ht to map conduit patterns and their hydraulic parameters prior to the ht analysis forward models are built to study groundwater flow through synthetic karst aquifers to generate data and to gain insights into flow patterns forward modeling results reveal that 1 flow rates at the outlet of the bcp model is higher than the ncp model even when the same water injection rates are applied at the wells 2 the location of the injection well has a significant impact on the flow rate at the outlet and 3 flow lines mainly follow the conduit pattern these results suggest that the accurate mapping of karst networks is critical next the ht analysis of these data is conducted using a set of six models bcp and ncp to map the heterogeneity of different conduit systems under steady state and transient flow conditions inverse modeling results reveal that the estimated k maps become more reliable as the number of injection tests and the corresponding monitoring data are increased in the ht analysis moreover the results of the bcp model is closer to the original conduit pattern in comparison to the ncp model a comparative study of three inverse models with different number of observation wells and assuming the availability of geological data has shown that a more reliable pattern of the conduits can be mapped by adding geological information even when a small number of observation wells are available overall our results confirm the feasibility of ht in detecting major conduits as well as being able to differentiate between the bcp and ncp network types

interference pumping tests in a fractured limestone poitiers france inversion of data by means of dual medium approaches hydraulic interference pumping tests remain a valuable method for obtaining information on underground flows at a scale compatible with the operation of a reservoir combining a dual medium model with the inversion of interference testing data in fractured rocks is very recent probably because the model is ruled by very contrasted sensitivities to its main parameters it is shown that an accurate and stable inversion requires a specific procedure based on re scaled sensitivities to parameters both homogeneous and fractal dual media have been inverted on two sets of data obtained from the fractured limestone of the experimental site in poitiers france the first data set can be homogenized with both homogeneous and fractal approaches yielding almost constant hydraulic parameters or only weak statistical variations beyond experienced distances of 200 m the second data set collected in a site perturbed by forced flows from the first campaign shows preferential flow paths with a piston like propagation of the pressure depletion only the fractal dual medium is able to partly homogenize the hydrodynamic behavior surprisingly the hydraulic conductivity is constant but the dimensioning constants of the capacity parameters continue to decrease with the size of the system thus the intrinsic decrease of parameters with the size of the system in the fractal approach is not sufficient to mimic the scale effects recorded by interference tests superimposition of piston like effects onto dual media shall be further investigated to better account for the influence of scarce flow paths with very high velocities

characteristics of molecular nitrogen generation from overmature black shales in south china preliminary implications from pyrolysis experiments abstract high content of molecular nitrogen n2 is one of the natural gas exploration risks in petroliferous basins where black shales act as source rocks of either hydrocarbon gas or molecular nitrogen in this study two overmature and one low maturity shale samples and their kerogens were investigated to determine the generation characteristics of molecular nitrogen as well as methane and the differences in the release processes of inorganic nitrogen fixed in ammonium bearing minerals and organic nitrogen bound in kerogen the results illustrate that with increasing pyrolysis temperature the yield of methane first increases and then decreases with an inflection temperature of 650 c eqvro 3 4 whereas the yield of molecular nitrogen shows a continuous increase throughout the pyrolysis experiment the molecular nitrogen during the stage of methane generation i e eqvro 3 4 the results also reveal that at the experimental maxima of thermal maturity eqvro 4 9 the generation potential of inorganic molecular nitrogen mg g ninorg is much lower than that of organic molecular nitrogen mg g norg indicating that in our experiments the organic nitrogen in kerogen is more easily to be converted into molecular nitrogen than the inorganic nitrogen in ammonium bearing minerals all these results indicate that molecular nitrogen content in shale gas may change dramatically during thermal evolution and source rocks with exceptionally high maturity and high abundance of organic nitrogen likely lead to a high molecular nitrogen risk particularly in regions of poor preservation conditions of shale gas which may be the main reasons for the high molecular nitrogen content in the lower cambrian shale gas in south china

identifying discrete geologic structures that produce anomalous hydraulic response an inverse modeling approach 1 subsurface hydraulic response is controlled by discrete geologic structures in a variety of aquifer settings in this work we analyze data from the well studied alluvial fan system that underlies the lawrence livermore national laboratory there subsurface flow and transport behavior is strongly influenced by discrete channel deposits which are embedded within less permeable floodplain deposits we model the distribution of these deposits using a multiple point geostatistical approach that enables simulation of geologically plausible connected permeable bodies consistent with a training image by coupling the geostatistical model with a dynamic flow model in a simulation inversion framework we identify specific channel structures that are consistent with transient aquifer test data at six observation wells we perform shortest path analysis to characterize the geometry of the simulated channels and to locate critical high permeability conduits that control the system s response to pumping in one area all successful inverse solutions identify the same set of stacked channel deposits a geologic feature that provides an explanation for anomalous response behavior observed during the aquifer test

on the use of multiple point statistics to improve groundwater flow modeling in karst aquifers a case study from the hydrogeological experimental site of poitiers france abstract limestone aquifers often exhibit complex groundwater flow behaviors resulting from depositional heterogeneities and post lithification fracturing and karstification in this study multiple point statistics mps was applied to reproduce karst features and to improve groundwater flow modeling for this purpose mps realizations were used in a numerical flow model to simulate the responses to pumping test experiments observed at the hydrogeological experimental site of poitiers france the main flow behaviors evident in the field data were simulated particularly i the early time inflection of the drawdown signal at certain observation wells and ii the convex behavior of the drawdown curves at intermediate times in addition it was shown that the spatial structure of the karst features at various scales is critical with regard to the propagation of the depletion wave induced by pumping indeed i the spatial shape of the cone of depression is significantly affected by the karst proportion in the vicinity of the pumping well and ii early time inflection of the drawdown signal occurs only at observation wells crossing locally well developed karst features

the isotopic compositions of molecular nitrogen implications on their origins in natural gas accumulations abstract the isotopic compositions of n2 15 n atm imply the geochemical origins of molecular nitrogen in natural gas accumulations but the irregular variation of 15 n n 2 for most petroliferous basins puzzles scientists we believe that this is due to multiple origins of n2 which are often mixed together and leads to the irregularities in gas pools the four petroliferous basins the west siberian basins in russia the yinggehai basin of china the californian great valley basin of usa and the mid european basin have significantly different isotope characteristics of n2 which may provide insight into the isotope geochemical implications of n2 in natural gas accumulations n2 with 19 15 n n 2 10 may be from sedimentary organic matter at the immature and the early mature stage ro 0 6 values of 10 15 n n 2 2 may indicate that n2 originates from mature including high mature sedimentary organic matter ro 0 6 2 0 values of 2 15 n n 2 15 n n 2 0 and n2 ar 38 84 suggest that the atmosphere is the origin values of 1 15 n n 2 15 n n 2 4 is the feature of n2 from saltpeter in evaporites values of 4 15 n n 2 18 indicate that n2 maybe derived from post mature sedimentary organic matter ro 2 0

origin and migration of oil and natural gas in the central part of the ukrainian outer carpathians geochemical and geological approach the generation and migration processes as well as the influence of secondary processes on oil and natural gas accumulated in lower cretaceous lower miocene strata of the central part of the ukrainian outer carpathians are discussed type ii and ii iii kerogens from the oligocene lower menilite beds of the boryslav pokuttya nappe generated oil and natural gas mainly during the middle stage of the oil window these hydrocarbons accumulated in the fields of the boryslav pokuttya and skiba nappes water washing is the dominant secondary process occurring in many accumulations regardless of reservoir rock whereas biodegradation is insignificant and is clearly evident only in natural gas from one seep in the abandoned starunia ozocerite mine all hydrocarbon gases are thermogenic and were generated from mixed organic matter containing various proportions of type ii and iii kerogens only one natural gas accumulation in the pivnichna dolyna field contains some microbial hydrocarbon contribution carbon dioxide mainly originated from thermogenic kerogen decarboxylation and sporadically from microbial processes molecular nitrogen was mainly generated during low temperature thermal transformation of organic matter and could also partly originate from nh4 rich illites of the clayey facies of the oligocene lower miocene menilite beds the integration of the geochemical data with geological setting and maturation history of source rocks enabled us to reconstruct hydrocarbon migration paths revealing the complicated trap filling process

pore water profiles and authigenic mineralization in shallow marine sediments above the methane charged system on umitaka spur japan sea umitaka spur situated on an unusual collisional plate boundary along the eastern margin of the japan sea hosts gas seeps pock marks collapse structures and gas hydrates piston cores were recovered from this ridge to understand carbon cycling pore fluid gradients and authigenic mineralization above a methane charged system we present the chemistry of fluids and solids from three cores adjacent to seep locations high fluxes of ch4 and alkalinity transport carbon from a deep zone of methanogenesis toward the seafloor methane however reacts with so42 across a shallow sulfate methane transition smt which generates additional alkalinity and hs a fraction of these ch4 oxidation products form authigenic carbonate and pyrite these minerals are not readily apparent from visual inspection of split cores because they exist as micritic coatings on microfossils or as framboidal pyrite they are however readily observed in chemical analyses as peaks of labile ca sr ba or s in sediment at or near the smt carbon inputs and outputs nicely balance across the smt in all three cores if one considers four relevant fluxes loss of alkalinity to the seafloor addition of methane from below addition of alkalinity from below and carbonate precipitation importantly in all cores the magnitude of the fluxes decreases in this order although some carbon rising from depth forms authigenic carbonate most 80 escapes to the ocean as alkalinity nonetheless authigenic fronts in sediment on umitaka spur are a significant reservoir of inorganic carbon given calculated pore fluid fluxes for ca and sr the fronts require tens of thousands of years to form suggesting that the present state and loss of carbon represent long lived processes

stable carbon isotope ratios of ch4 rich gas inclusions in shale hosted fracture fill mineralization a tool for tracing hydrocarbon generation and migration in shale plays for oil and gas abstract fluid inclusion gases in minerals from shale hosted fracture fill mineralization have been analyzed for stable carbon isotopic ratios of ch 4 using a crushing device interfaced to an isotope ratio mass spectrometer irms the samples of paleozoic strata under study originate from outcrops and wells in the rhenish massif and campine basin harz mountains and the upper slope of the southern permian basin fracture fill mineralization hosted by mesozoic strata was sampled from drill cores in the lower saxony basin some studied sites are candidates for shale gas exploration in germany samples of mesozoic strata are characterized by abundant calcite filled horizontal fractures which preferentially occur in toc rich sections of the drilled sediments only rarely are vertical fractures filled with carbonates and or quartz in drill cores from mesozoic strata but in paleozoic shale they occur frequently the 13 c ch 4 values of fluid inclusions in calcite from horizontal fractures hosted by mesozoic strata suggest that gaseous hydrocarbons were generated during the oil early gas window and that the formation of horizontal fractures seems to be related to hydraulic expulsion fracturing the calculated maturity of the source rocks at the time of gas generation lies below the maturity derived from measured vitrinite reflectance thus the formation of horizontal fractures and trapping of gas that was generated in the oil and or early gas window obviously occurred prior to maximal burial rapidly increasing vitrinite reflectance data seen locally can be explained by hydrothermal alteration as indicated by increasing 13 c ch 4 co 2 values in fluid inclusions the formation of vertical fractures in studied mesozoic sediments is related to stages of post burial inversion gas rich inclusions in fracture filling minerals recorded the migration of gas that had probably been generated instantaneously rather than cumulatively from high to overmature source rocks since no evidence is given for the presence of early generated gas in studied paleozoic shale it appears likely that major gas loss from shales occurred due to deformation and uplift of these sediments in response to the variscan orogeny

origin of nitrogen rich natural gases in the california great valley evidence from helium carbon and nitrogen isotope ratios abstract dry natural gases produced from the sacramento and northern san joaquin basins contain up to 87 nitrogen 15n measurements for gases with n2 8 vary from 0 9 to 3 5 methane 13c values vary from 61 to 15 3 he 4 he ratios indicate the presence of mantle derived helium in addition to radiogenic crustal helium and suggest that the gases may originate from mixing between three principal components a hydrocarbon rich gas with 3 he 4 he 0 1r a derived from the microbial and thermogenic alteration of sedimentary organic matter a hydrocarbonrich gas with 3 he 4 he 2 75r a derived from the localized pyrolysis of sediments by magmatic volatiles and a nitrogenrich gas with 3 he 4 he 1r a the nitrogen rich component is characterized by methane 13c less negative than 25 and n 2 ar ratios as high as 22 000 nitrogen concentrations tend to increase towards the basement along the shallow eastern margin of the valley suggesting that the nitrogen rich component is derived from metasedimentary rocks deep within the crust the coast ranges fraciscan complex which was thrust well beneath the great valley during late mesozoic and early cenozoic subduction appears to be the most likely source

stable isotope geochemistry of coal bed and shale gas and related production waters a review coal bed and shale gas can be of thermogenic microbial or of mixed origin with the distinction made primarily on the basis of the molecular and stable isotope compositions of the gases and production waters methane ethane carbon dioxide and nitrogen are the main constituents of coal bed and shale gases with a general lack of c2 hydrocarbon species in gases produced from shallow levels and more mature coals and shales evidence for the presence of microbial gas include 13c ch4 values less than 50 covariation of the isotope compositions of gases and production water carbon and hydrogen isotope fractionations consistent with microbial processes and positive 13c values of dissolved inorganic carbon in production waters the co2 reduction pathway is distinguished from acetate methyl type fermentation by somewhat lower 13c ch4 and higher d ch4 but can also have overlapping values depending on the openness of the microbial system and the extent of substrate depletion crossplots of 13c ch4 versus 13c co2 and d ch4 versus 13c h2o may provide a better indication of the origin of the gases and the dominant metabolic pathway than the absolute carbon and hydrogen isotope compositions of methane in the majority of cases microbial coal bed and shale gases have carbon and hydrogen isotope fractionations close to those expected for co2 reduction primary thermogenic gases have 13c ch4 values greater than 50 and 13c values that systematically increase from c1 to c4 and define a relatively straight line when plotted against reciprocal carbon number although coals and disseminated organic matter in shales represent a continuum as hydrocarbon source rocks current data suggest a divergence between these two rock types at the high maturity end in deep basin shale gas reversals or rollovers in molecular and isotopic compositions are increasingly reported in what is effectively a closed shale system as opposed to the relative openness in coal measure environments detailed geochemical studies of coal bed and shale gas and related production waters are essential to determine not only gas origins but also the dominant methanogenic pathway in the case of microbial gases

cosmic ray constancy and cosmogenic production rates in short lived chondrites abstract five chondrites with short cosmic ray exposure ages 26al and 53mn saturation values deduced from short lived chondrites alone agree within 20 with those deduced from all chondrites values of 21p based on 53mn and 26al are 0 30 0 03 and 0 46 0 05 respectively in h chondrites possible causes for the difference include half life errors data selection and a recent 2 5myr increase in the cosmic ray intensity

generation of nitrogen and methane from sedimentary organic matter implications on the dynamics of natural gas accumulations nitrogen n2 contents of natural gases in rotliegend and buntsandstein reservoirs of the north german basin regionally approach 100 a review is given of the various hypotheses primordial origin volcanic or magmatic origin radiogenic origin atmospheric origin organic origin inorganic nitrogen in sedimentary rocks presented to account for nitrogen anomalies in this area and other parts of the world the objective of the present study was to investigate sedimentary organic matter in particular coals as a potential source of molecular nitrogen in the subsurface comparison of reservoir sizes and gas generation potentials indicates that carboniferous coal measures which are considered as the source of the natural gas in the north german basin can readily account for the nitrogen quantities found in present day reservoirs laboratory pyrolysis experiments were carried out to investigate the kinetics of generation of methane and molecular nitrogen from coals of different type and rank under experimental conditions nitrogen is formed at higher temperatures than methane supporting the concept of a fractional generation of methane and nitrogen in natural systems based on the kinetic parameters derived from laboratory experiments methane and nitrogen generation rates from coals were calculated for geologic heating rates gas containing more than 50 nitrogen is generated under these conditions at temperatures in excess of 300 c nitrogen rich gases are thus formed only in the final stage of gas generation after methane generation has practically ceased it is concluded that the amounts of gas encountered in nitrogen rich gas accumulations represent only a small fraction possibly 1 of the total gas generation potential of this area while the bulk of the generated gas has escaped to the atmosphere the present day composition of the reservoir gases reflects the composition of only the most recently generated gas on a geologic time scale

origin of hydrocarbon and noble gases carbon dioxide and molecular nitrogen in devonian pennsylvanian and miocene strata of the polish lublin and ukrainian lviv basins southern part of the upper silesian coal basin and western part of the carpathian foredeep poland abstract sixteen natural gas samples were collected from devonian pennsylvanian and miocene strata of the polish lublin and ukrainian lviv basins from the southern area of the upper silesian coal basin uscb and western part of the carpathian foredeep cf in poland the samples were analysed for the molecular composition and stable isotope compositions of gaseous hydrocarbons ch4 c2h6 and c3h8 and co2 n2 and noble gases he ne ar kr and xe in order to reveal the origin and migration pathways of these gases hydrocarbon gases and the majority of the of co2 were generated during two stages of thermogenic processes from type ii and ii iii kerogens in the lublin basin and during both thermogenic and microbial processes in the lviv basin the thermogenic component was generated from type ii kerogen coal bed hydrocarbon gases accumulated in the pennsylvanian strata of the southern part of the uscb originated from both thermogenic and microbial processes isotopically light microbial methane may have migrated from miocene upper badenian skawina formation of the cf to carboniferous coal bearing strata and or might result from diffusion and adsorption desorption processes during the migration of thermogenic gases from deeper lying coal seams through the microporous coal structure hydrocarbon gases and carbon dioxide which accumulated in the sandstone reservoirs of upper badenian skawina formation of the western part of the cf most probably were generated from dispersed organic matter within the claystones and mudstones of these strata and at least partly migrated from the carboniferous coal bearing strata of the uscb n2 could have been produced as a result of various biogenic and abiogenic processes and contributed to the atmospheric component characteristic radiogenic 4he composition of the analysed gases suggest the accumulation of particles formed from u and th radioactive decay in the crustal gas reservoirs radiogenic 40ar and nucleogenic 21ne with abundance ratios characteristic of crustal reservoirs were also observed addition of mantle derived he to the gases from miocene strata is evident from elevated 3he 4he ratios ranging between 0 2 and 1 6 10 6 a small contribution of ne from the mantle along with he is also suggested by the slightly elevated 20ne 22ne ratios relative to atmosphere the mantle component is most likely to have migrated from the upper mantle to the gas reservoirs through the deep seated bzie czechowice fault zone

evidence of inception horizons in karst conduit networks this paper outlines the conclusion from an analysis of 18 large cave systems around the world comprising more than 1500 km of conduits the 3d geometry of complex cave systems have been analysed in relation to their geological context as well as their hydrogeological boundary conditions the methodology allowed for the first time statistical evidence of the inception horizon concept thereby it confirms that the development of karst conduits under phreatic conditions is strongly related to a restricted number of so called inception horizons an inception horizon is a part of a rock succession that is particularly susceptible to the development of karst conduits because of physical lithological or chemical deviation from the predominant carbonate facies within the limestone sequence it passively or actively favours the localisation of dissolutional voids

molecular nitrogen in natural gas accumulations generation from sedimentary organic matter at high temperatures the occurrence of natural gas accumulations with high percentages up to 100 of molecular nitrogen in various hydrocarbon provinces represents a largely unresolved problem and a serious exploration risk in this context a geochemical and basin modeling study was performed to evaluate the potential of sedimentary organic matter to generate molecular nitrogen the masses of nitrogen present in coals if converted into molecular nitrogen are sufficient to fill commercial gas reservoirs a calculation for gas accumulations in northern germany where percentages of molecular nitrogen range from less than 5 to greater than 90 reveals that the molecular nitrogen generated in underlying coal bearing strata is sufficient to account for the nitrogen gas even in the largest fi lds in addition much of the total nitrogen in clay rich rock types such as shales and mudstones is fixed in sedimentary organic matter and may add to the nitrogen generation capacity of the coals a kinetic interpretation of the nitrogen and methane generation characteristics of humic coals during laboratory pyrolysis indicates that nitrogen is generated from organic matter in sedimentary basins at higher temperatures than methane minimum temperatures for preferential nitrogen generation are in excess of 300 c for extremely low heating rates or isothermal conditions lasting over 300 m y thus nitrogen rich gases are mainly formed in the final stage of gas generation when sedimentary rocks grade into metamorphic rocks applications of the kinetic parameters for the generation of nitrogen and methane from coaly organic matter in carboniferous sedimentary rocks are presented for part of the northwest german basin in this area immense volumes of the methane rich gas gener ted during the late paleozoic and mesozoic were lost to the atmosphere the present gas composition mainly reflects the latest cenozoic gas generation this cenozoic gas is nitrogen rich where the carboniferous source rock sequences are highly mature and deeply buried

extreme methane deuterium nitrogen and helium enrichment in natural gas from the homorod seep romania abstract methane ch 4 in terrestrial environments whether microbial thermogenic or abiogenic exhibits a large variance in c and h stable isotope ratios due to primary processes of formation isotopic variability can be broadened through secondary post genetic processes such as mixing and isotopic fractionation by oxidation the highest and lowest 13 c and 2 h or d deuterium concentrations in ch 4 found in various geologic environments to date are defined as natural terrestrial extremes we have discovered a new extreme in a natural gas seep with values of deuterium concentrations d ch4 up to 124 that far exceed those reported for any terrestrial gas the gas seeping from the small homorod mud volcano in transylvania romania also has extremely high concentrations of nitrogen 92 vol and helium up to 1 4 vol carbon isotopes in ch 4 c 2 h 6 and co 2 and nitrogen isotopes in n 2 indicate a primary organic sedimentary origin for the gas a minor mantle component is suggested by the 3 he 4 he ratio r ra 0 39 both thermogenic gas formation modeling and rayleigh fractionation modeling suggest that the extreme deuterium enrichment could be explained by an oxidation process characterised by a d ch4 and 13 c ch4 enrichment ratio h c of about 20 and may be accounted for by abiogenic oxidation mediated by metal oxides all favourable conditions for such a process exist in the homorod area where increased heat flow during pliocene quaternary volcanism may have played a key role finally we observed rapid variations within 1 h in c and h isotope ratios of ch 4 and in the h 2 s concentrations which are likely caused by mixing of the deep oxidized ch 4 n 2 h 2 s he rich gas with a microbial methane generated in the mud pool of one of the seeps we hypothesize that the unusual features of homorod gas can be the result of a rare combination of factors induced by the proximity of sedimentary organic matter mafic metal rich volcanic rocks and salt diapirs leading to the following processes a primary thermogenic generation of gas at temperatures between 130 and 175 c b secondary alteration through abiogenic oxidation likely triggered by the neogene quaternary volcanism of the eastern transylvanian margin and c mixing at the surface with microbial methane that formed through fermentation in the mud volcano water pool the homorod gas seep is a rare example that demonstrates how post genetic processes can produce extreme gas isotope signatures thus far only theorized and that extremely positive d ch4 values cannot be used to unambiguously distinguish between biotic and abiotic origin