high injection rates counteract formation of far reaching fluid migration pathways at the geysers geothermal field deep underground water injections induce seismicity when the seismic fractures coalesce into far reaching pathways for fluid migration the migrating fluid may reach pre existing faults and by de

structural controls on anomalous transport in fractured porous rock anomalous transport is ubiquitous in a wide range of disordered systems notably in fractured porous formations we quantitatively identify the structural controls on anomalous tracer transport in a model of a real fractured geological formation that was mapped in an outcrop the transport determined by a continuum scale mathematical model is characterized by breakthrough curves btcs that document anomalous or non fickian transport which is accounted for by a power law distribution of local transition times t within the framework of a continuous time random walk ctrw we show that the determination of t is related to fractures aligned approximately with the macroscopic direction of flow we establish the dominant role of fracture alignment and assess the statistics of these fractures by determining a concentration visitation weighted residence time histogram we then convert the histogram to a probability density function pdf that coincides with the ctrw t and hence anomalous transport we show that the permeability of the geological formation hosting the fracture network has a limited effect on the anomalous nature of the transport rather it is the fractures transverse to the flow direction that play the major role in forming the long btc tail associated with anomalous transport this is a remarkable result given the complexity of the flow field statistics as captured by concentration transitions this article is protected by copyright all rights reserved

ridge regression algorithm for gravity inversion of fault structures with variable density we derive an analytical expression for gravity anomalies of an inclined fault with density contrast decreasing parabolically with depth the effect of the regional background particularly the interference from neighboring sources of a fault structure is ascribed by a polynomial equation we have developed an inversion technique employing the ridge regression iterative algorithm to infer the shape parameters of the fault structure in addition to the effect of regional background we demonstrate the validity of the proposed technique by inverting a gravity anomaly of a theoretical model both with and without adding a regional background the technique is insensitive to the effect of regional background two density depth models of the godavari subbasin in india are used in our interpretation of the gravity anomalies of the ahiri cherla master fault the interpreted results of a parabolic density model are found to be more geologically reasonable in comparison with the constant density model the variations of the misfit function of the theoretical and observed gravity anomalies the damping factor and the shape parameters of the fault against the iteration number indicate the reliability of the interpretation

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

fracture network analysis of the st eustache quarry quebec canada for groundwater resources management a detailed structural survey has been conducted on a fractured sedimentary rock formation in the st eustache quarry quebec canada to supplement a hydrogeological study the two main types of dis

correlation analysis of fracture arrangement in space abstract we present new techniques that overcome limitations of standard approaches to documenting spatial arrangement the new techniques directly quantify spatial arrangement by normalizing to expected values for randomly arranged fractures the techniques differ in terms of computational intensity robustness of results ability to detect anti correlation and use of fracture size data variation of spatial arrangement across a broad range of length scales facilitates distinguishing clustered and periodic arrangements opposite forms of organization from random arrangements moreover self organized arrangements can be distinguished from arrangements due to extrinsic organization traditional techniques for analysis of fracture spacing are hamstrung because they account neither for the sequence of fracture spacings nor for possible coordination between fracture size and position attributes accounted for by our methods all of the new techniques reveal fractal clustering in a test case of veins or cement filled opening mode fractures in pennsylvanian marble falls limestone the observed arrangement is readily distinguishable from random and periodic arrangements comparison of results that account for fracture size with results that ignore fracture size demonstrates that spatial arrangement is dominated by the sequence of fracture spacings rather than coordination of fracture size with position fracture size and position are not completely independent in this example however because large fractures are more clustered than small fractures both spatial and size organization of veins here probably emerged from fracture interaction during growth the new approaches described here along with freely available software to implement the techniques can be applied with effect to a wide range of structures or indeed many other phenomena such as drilling response where spatial heterogeneity is an issue

the iceland research drilling project this issue of the journal of geophysical research contains the collected results of the initial studies of a 3 km vertical section of icelandic crust the material described in these papers was largely presented at a meeting of the investigators working in this project held in reykjavik iceland from may 13 to may 15 1980 iceland presents a very well exposed example of crust formed at an accretional plate margin the crest of the mid atlantic ridge the desirability of a detailed study of a long vertical section of icelandic crust by deep drilling has been expressed in proposals and recommendations of scientists and international scientific committees since the early 1960 s a formal proposal with descriptions of several alternative drill sites was presented in 1975 working group on deep crustal drilling in iceland 1975 but difficulties in financing a drill hole that would penetrate into crustal layer 3 vp 6 5 km s delayed implementation of the recommendations

modeling complex flow in a karst aquifer abstract carbonate aquifers typically have complex groundwater flow patterns that result from depositional heterogeneities and post lithification fracturing and karstification various sources of information may be used to build a conceptual understanding of flow in the system including drilling data well tests geophysical surveys tracer tests and spring gaging these data were assembled to model flow numerically in germany s malm formation at a site where water disappears from the beds of ephemeral stream valleys flows through conduit systems and discharges to springs along surface water features modeling was performed by using a finite difference approach with drain networks representing the conduit component of flow laced throughout the porous medium along paths inferred on the basis of site data this approach represents an improvement over other karst models that attempt to represent a conduit by a single specialized model node at the spring location or by assigning a computationally problematic extremely high permeability to a zone by handling the conduit portion of this mixed flow system with drains a realistic interpretive flow model was created for this intricate aquifer

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

three dimensional interpretation of gravity data from sedimentary basins using an exponential density depth function in mapping the topography of the basement of deep sedimentary basins by gravity modelling the accuracy can be improved by incorporating an exponential increase in density with depth for calculating the gravity effect of a three dimensional 3d structure with such an exponential density depth relation a frequency domain forward algorithm based on series expansion is presented the numerical evaluation of which can be performed efficiently by fast fourier transform the algorithm can be applied in a recursive procedure to give the inverse solution in terms of basement relief the inversion procedure is satisfactorily tested on a 2d synthetic example and a 3d field example of gravity data from the western margin of the pannonian basin in eastern austria where up to 2 2 km of tertiary sediments overlie an igneous or metamorphic basement the results are confirmed by basement intersections in several wells

integrating damage zone heterogeneities based on stochastic realizations of fracture networks for fault stability analysis in the domain of reservoir engineering fault stability assessment is traditionally performed by assimilating fault systems to surfaces however faults are complex and heterogeneous geological systems whose compartmentalized architecture generally corresponds to an inner core surrounded by outer often fractured damage zones dz to date few studies have assessed the potential role of the dz characteristics anisotropy complex spatial distribution etc on the shear behavior of the whole system the main challenge being the proper numerical integration of fracture networks in reservoir simulators the present study was motivated by the stochastically generated fracture networks representative of dz investigated on outcrops cirques de navacelles south of france we propose here a methodology relying on homogenization techniques for deriving the spatial distribution of effective anisotropic hydro poro elastic dz properties from these stochastic fracture networks using them as inputs of 2d finite element coupled hydro mechanical models of a reservoir scale fault zone the key role of the spatially varying dz stiffness and biot s coefficients are highlighted neglecting them might lead to a high over estimation of the maximum sustainable injection pressure by nearly 50 in the considered cases

geometry percolation and transport properties of fracture networks derived from line data summary in most geological instances 2 d or 3 d fracture distributions are not available from field data we show here that when data relative to fractures are collected along a line such as a road or a well estimations can be given to the major geometrical properties of the corresponding fracture networks such as the volumetric density of fractures their percolation character and their macroscopic permeability all these formulae are analytical and can be split into two parts the first one can be derived from the measured data while the second one requires some assumption on the lateral extension of the fractures and on their permeability all these techniques are applied to fractures located in the baget watershed they are also validated on a granite block whose structure is fully known extensions are proposed for networks with variable permeabilities and polydisperse fractures

the relationship of the degree of interconnection to permeability in fracture networks the problem of determining the permeability of a rock mass containing a system of finite fractures is highly dependent on both the degree of interconnection between fractures and the heterogeneity of individual fracture characteristics this paper examines how degree of interconnection affects both magnitude and nature of the fracture permeability the interconnection between given fracture sets is a complex function of 1 fracture density i e the number of fractures per unit volume and 2 the fracture extent or size unfortunately neither the density nor the extent of fractures is easily determined from borehole data however fracture frequency can be directly measured in a borehole because it is simply the number of fractures intersected per unit length of the borehole the frequency is a measure of the product of fracture density and size because the probability of a fracture intersecting a borehole is proportional to this product the effect of the degree of interconnection was investigated by numerically simulating flow in fracture networks where fracture size and density varied inversely while the product of these two parameters was held fixed directional permeabilities of a number of such networks were determined and the hydraulic behavior of each fracture system was compared to that of an ideal porous medium the permeability of the rock matrix between the fractures was assumed to be low enough to be negligible the results show that as fracture length increases the degree of interconnection increases thus for a given fracture frequency as measured in a borehole the permeability of the system increases as fracture length is increased and density is proportionally decreased also fracture systems with shorter but more dense fractures behave less like porous media than do systems with longer but less dense fractures knowledge of fracture frequency and orientation alone is inadequate when determining permeability or deciding the important question of whether a given system behaves like a porous medium for many cases where these parameters can be measured in the borehole it is critical to know fracture length in order to predict the degree of fracture network interconnection however for certain cases where fractures are larger than some critical size it may not be necessary to know fracture lengths exactly

multifractal characteristics of natural fracture apertures using information acquired from microscanner logs in horizontal boreholes fracture apertures are shown to be characterized by multifractal scaling a representative f spectrum can be modeled using a multiplicative cascade based on a two scale cantor set the resulting cascade can be used to simulate fracture aperture distributions at any scale when compared to well data the simulations show good agreement with aperture sizes and reproduce the clustering commonly recognized in fracture networks

stochastic fracture simulation using pixel based multiple point geostatistics by integrating seismic radial anisotropy and well data applications in two hydrology sites we propose a pixel based multiple point simulation algorithm for stochastic simulation of near surface fractures using seismic radial anisotropy as secondary information the method borrows information from the training image of the fracture and anchoring within the secondary radial anisotropy data using wavelet based multiple point simulation framework the simulation was performed sequentially by sampling from the conditional cumulative density function ccdf of fracture conditioning to radial anisotropy for faster computation instead of calculating ccdf at each unknown location a limited number of ccdfs are calculated the patterns of the multiple point representation are extracted from the training image and are classified into multiple classes using the wavelet decomposition analysis each class is represented by a class prototype and ccdf during simulation the conditioning data are compared with the class prototypes and a random sample is generated from the ccdf of the best match class we validated the proposed simulation method using a synthetic fracture dataset a sensitivity analysis was also performed to show the impact of correlation between fracture and radial anisotropy and the resolution of the radial anisotropy results demonstrated that the reproduction of the fracture depends on its correlation with the radial anisotropy it was also observed that fracture reproduction is proportional to the resolution of the radial anisotropy we successfully applied our proposed model to two hydrogeological sites in which seismic radial anisotropy was obtained using the dispersion analysis of the surface wave

stereological analysis of fractures in the roselend tunnel and permeability determination 1 fracture traces and water fluxes have been determined along the 128 m long roselend tunnel french alps fractures can be classified into two families large fractures which intersect the tunnel and small fractures which partially intersect it three different zones in the tunnel are distinguished with mild low and high water fluxes starting from the entrance a stereological analysis of the trace length probability densities of small fractures provides the fracture diameter probability density distribution which is best approximated by a power law large fractures are assumed monodisperse with a 5 m estimated radius the generated fracture networks obtained by combining large and small fractures do percolate while networks consisting of only small fractures do not percolate computed macroscopic permeabilities of the fracture networks are in agreement with the observed water fluxes when the fracture permeability is a power law of its lateral extent with an exponent equal to 3

magnetic and thermal effects of dike intrusions in iceland oriented core samples were collected from 18 lava dike contacts in iceland in locations of low to moderate 100 c regional hydrothermal alteration alternating field demagnetization of these samples shows that they generally carry a strong and stable remanence magnetic directions in the lavas follow a simple pattern demonstrating that the remanence of the contact zone has only been reset within very short distances from the contact surface on average this distance may be only one tenth of the thickness of a typical dike 4 m other magnetic properties remanence intensity susceptibility curie point of the contact zone are affected to a lesser or a less regular degree than the remanence direction it is concluded that for the crustal depth of this study thermal conduction models do not apply to temperature anomalies set up by dike intrusions or fissure eruptions in iceland presumably because of rapid advection of groundwater into the active fissures these results also indicate that the magnetic anomalies observed over iceland are only to a small extent caused by dikes

identifying fracture zone geometry using simulated annealing and hydraulic connection data a new approach is presented to condition geostatistical simulation of high permeability zones in fractured rock to hydraulic connection data a simulated annealing algorithm generates three dimensional 3 d realizations conditioned to borehole data inferred hydraulic connections between packer isolated borehole intervals and an indicator fracture zone or background k bedrock variogram model of spatial variability we apply the method to data from the u s geological survey mirror lake site in new hampshire where connected high permeability fracture zones exert a strong control on fluid flow at the hundred meter scale single well hydraulic packer tests indicate where permeable fracture zones intersect boreholes and multiple well pumping tests indicate the degree of hydraulic connection between boreholes borehole intervals connected by a fracture zone exhibit similar hydraulic responses whereas intervals not connected by a fracture zone exhibit different responses our approach yields valuable insights into the 3 d geometry of fracture zones at mirror lake statistical analysis of the realizations yields maps of the probabilities of intersecting specific fracture zones with additional wells inverse flow modeling based on the assumption of equivalent porous media is used to estimate hydraulic conductivity and specific storage and to identify those fracture zone geometries that are consistent with hydraulic test data

a dual fracture model to simulate large scale flow through fractured rocks discrete fracture network models can be used to study groundwater flow in fractured rock masses however one may find that it is not easy to apply such models to practical projects as it is diffic

the connectivity of two dimensional networks of spatially correlated fractures 1 continuum percolation thresholds for fracture systems are based on models with random fracture locations resulting in uniformly clustered systems in which all connections are fracture intersections fractures in natural systems can be either clustered or anticlustered and a significant portion of the connectivity is achieved through fracture abutments or splays analytical and numerical methods are combined to define critical properties of isotropic networks of constant length lines as a function of fracture clustering and of the ratio of abutments to intersections a second suite of numerical results indicates that the influence of these parameters varies as a function of the fracture length distribution a preliminary predictor of critical density of anisotropic nonrandom systems with lognormal length distributions is derived and applied to a suite of natural fracture systems predicted connectivities are closer to the observed connectivities when the predictor is used than when connectivity is estimated from the random threshold

early cenozoic crust at the norwegian continental margin and the conjugate jan mayen ridge multichannel seismic profiles at the voring plateau margin off norway and the northern jan mayen ridge have provided a framework for the early tertiary evolutionary history of these areas which were adjacent prior to the opening of the norwegian sea we propose that their paleogene evolution is quite similar and that the two acoustic basement reflectors ee and jo were formed in the early eocene by extrusion of flow basalts from the time of opening to about anomaly 23 time oceanic seafloor was generated by icelandic type spreading during that time the central jan mayen fracture was the main transform the seaward dipping reflector sequences are flow basalts generated by the icelandic spreading the existence of less well developed dipping sequences seaward of the primary ones probably reflects that these regions submerged later because of higher initial elevation during the early eocene subaerial spreading episode which is related to the north atlantic volcanic province basalt flows also covered the adjacent thinned and heavily intruded continental crust it is proposed that the continent ocean boundary is located just landward of anomaly 24b a short distance seaward of the voring plateau escarpment reflector k is only recognized landward of this boundary in a region of transitional crust the escarpment experienced syndepositional faulting and the most elevated parts of the voring marginal high did not subside below shallow water depths before oligocene miocene time we suggest that the voring margin and the jan mayen ridge represent volcanic passive margins the evolution of this margin type may relate to initial uplift due to rifting in previously thinned crust

clay mineral authigenesis in coal and shale from the anthracite region pennsylvania textural chemical and mineralogical analyses of authigenic clays in anthracite rank coal and associated shale from eastern pennsylvania have allowed a better understanding of the parameters controlling diagenesis and perhaps coalification in this region minerals in anthracite occur in distinct assemblages associated with the following microenvironments coal matrix two orthogonal joint sets termed systematic and nonsystematic cleat and a third joint set mineralogical differences among microenvironments allow inferences about clay mineral origins and the parameters that controlled mineral authigenesis kaolinite occurs in the shale and all microenvironments within the coal seam authigenic minerals that replaced preexisting kaolinite during the latest stage ofcoalification anthracitization at t 200 c include nhu rich illite pyrophyllite and the following minerals which are primarily restricted to the systematic cleat set tosudite rl ordered dioctahedral mixed layer chlorite smectite sudoite di trioctahedral chlorite and rectorite rlordered mixedjayer paragonite smectite alteration of smectite to illite may be responsible for formation of authigenic illite and na bearing illite which are present only in the shale and coal matrix and fe al rich chlorite and quartz in the third joint set the chemical components for authigenesis appear to have multiple sources ai and si from preexisting kaolinite and quartz n from local organic matter mg and na for tosudite sudoite and rectorite largely from metasomatic hydrothermal fluids fe and mg for fe al rich chlorite from smectite illitization minerals in the shale the coal matrix and the nonsystematic cleat set are interpreted to represent authigenesis in a low permeability environment closed system alteration however the assemblage sudoite tosudite rectorite in the systematic cleat set is interpreted to be the result ofone or two stages ofhydrothermal alteration open system alteration we suggest hat differences in minerals between the two nearly perpendicular cleat sets are the result of permeability differences which were maintained by an anisotropic lateral stress field created by plate convergence during the alleghanian orogeny hydrothermal alteration may be related to large scale basinal flow induced by alleghanianage uplift such migrating fluids could also have transported heat from depth and thereby significantly increased the rate and rank ofcoalification in this region

determination of the tectonic evolution from fractures faults and calcite twins on the southwestern margin of the indochina block in polyphase tectonic zones integrating a study of fault and fracture with calcite twin analysis can determine the evolving paleostress magnitudes and principle stress directions that affected the area this paper presents the results of the analyses of fractures striated faults and calcite twins collected within the khao khwang fold thrust belt in central thailand se asia here we attempt to reconstruct the orientation of the principal stresses that developed during the tectonic evolution of this highly deformed polyphase orogen tectonic data were collected in the permian carbonates of the khao khad formation of the saraburi group and five successive tectonic stages are determined that are interpreted to have developed before during and after the triassic indosinian orogeny the first three stages predate the main deformation event the first stage is interpreted as a pre indosinian n s extensional stage the second stage described a n s strike slip and compressional regime largely perpendicular to the fold axes of the main structures while the third stage is associated with an e w compressional strike slip phase a further two stages took place after or during the main folding event and correspond to n s compression and to an e w composite strike slip contractional stage the latter which is interpreted to represent cenozoic deformation related to the india asia collision

a variable aperture fracture network model for flow and transport in fractured rocks a three dimensional variable aperture fracture network model for flow and transport in fractured rocks was developed the model generates both the network of fractures and the variable aperture distribution of individual fractures in the network before solving for the flow and transport of the whole network a library of single fracture permeabilities and particle transport residence time spectra is first established the spatially varying aperture field within an individual fracture plane is constructed by geostatistical methods then the flow pattern the fracture transmissivity and the residence times for transport of particles through each fracture are calculated the library of transmissivities and frequency distributions of residence times is used for all fractures in the network by a random selection procedure the solution of flow through the fracture network and the particle tracking calculation of solute transport for the whole network are derived from one side of the network to the other the model thus developed can handle flow and transport from the single fracture scale to the multiple fracture scale the single fracture part of the model is consistent with earlier laboratory tests and field observations the multiple fracture aspect of the model was verified in the constant aperture fracture limit with an earlier code the simulated breakthrough curves obtained from the model display dispersion on two different scales as has been reported from field experiments

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

spatial moments analysis of kinetically sorbing solutes in aquifer with bimodal permeability distribution 1 we analyze the influence of the formation structure upon transport of nonreactive and kinetically sorbing solutes in heterogeneous porous formations formation structure is represented through a bimodal distribution of hydraulic conductivity with two scales of spatial variability which is a simplified yet realistic model of spatial variability kinetic sorption is modeled using a linear reversible rate expression we derive new closed form solutions of the second ergodic spatial moments of a kinetically sorbing solute although these solutions are obtained through a perturbation expansion in term of logconductivity variance they are not limited to any particular model of spatial variability we show that the formation structure as described by the bimodal model has a significant impact on plume moments of a non reactive tracer at moderate contrast between mean hydraulic conductivity of the two hydrofacies when the two scales of variability have comparable weight on the contrary the impact diminishes when bimodality weakens at both low and high contrast as expected the large time asymptotic longitudinal macrodispersion coefficient is influenced by the structure only through the variance and integral scale of log conductivity and thus the result for the bimodal model is identical to that of a unimodal gaussian field sharing the same second order statistics the impact of kinetic sorption depends upon the plume travel time since injection at early times sorption kinetics tends to accentuate the difference between the longitudinal macrodispersivity in bimodal and unimodal fields while at later times the difference is minimal because overall macrodispersivity is dominated by the spreading caused by nonequilibrium sorption in a bimodal formation transverse macrodispersivity peaks later and declines to zero slower than in a gaussian unimodal field with the same second order statistics these results demonstrate that even a very simplified facies model such as the bimodal model relying on a statistical distribution of high and low conductivity zones has important impacts upon global parameters describing the migration of nonreactive and reactive tracers consequently larger effects are expected for quantities such as early arrival times and btc tailing which are more directly influenced by the spatial patterns of high hydraulic conductivity than global parameters such as macrodispersivity furthermore these solutions contribute to bridge the gap between stochastic modeling and applications since bimodal fields can be obtained to honor soft data typically available in applications for example through conditional simulations using stratigraphic information from well logs

gravity interpretation of nonoutcropping sedimentary basins in which the density contrast decreases parabolically with depth the decrease in density contrast of sedimentary rocks with depth in many sedimentary basins can be approximated by a parabolic density function analytical gravity expression of an outcropping two dimensional vertical step along which the density contrast decreases parabolically with depth is derived in the space domain a modification ofbott s 1960 method of gravity interpretation is proposed by considering two outcropping vertical steps on either side of the first and last observation points in addition ton outcropping vertical prisms in order to interpret the gravity anomalies of nonoutcropping basins the thicknesses of the two outcropping vertical steps are made equal to the thicknesses of the two outcropping vertical prisms placed below the first and last observation points the initial depth estimates of the sedimentary basin are calculated by the infinite slab formula ofvisweswara raoet al 1993 the gravity effects of then outcropping prisms and the two outcropping vertical steps are calculated at each anomaly point and the depth to the floor of the basin are adjusted based on the differences between the observed and calculated anomalies a gravity anomaly profile of los angeles basin california is interpreted

scaling of fracture connectivity in geological formations a new method to quantify fracture network connectivity is developed and applied to analyze two classical examples of fault and joint networks in natural geological formations the connectivity measure accounts for the scaling properties of fracture networks which are controlled by the power law length distribution exponent a the fractal dimension d and the fracture density the connectivity behavior of fracture patterns depends on the scale of measurement for a d 1 analysis of the san andreas fault system shows that a d 1 and that the connectivity threshold is reached only at a critical length scale in contrast for a typical sandstone joint pattern a d 1 which is on the cusp where the connectivity threshold is highly sensitive to the minimum fracture length in the system

transport and retention from single to multiple fractures in crystalline rock at aspo sweden 2 fracture network simulations and generic retention model hydrogeologic characterization of crystalline rock formations on the field scale is important for many applications but still presents a multitude of challenges neuman 2005 in this work we use

constraints on bed scale fracture chronology with a fem mechanical model of folding the case of split mountain utah usa abstract a technique is presented for improving the structural analysis of natural fractures development in large scale fold structures a 3d restoration of a fold provides the external displacement loading conditions to solve by the finite element method the forward mechanical problem of an idealized rock material with a stress strain relationship based on the activation of pervasive fracture sets in this elasto plasticity constitutive law any activated fracture set contributes to the total plastic strain by either an opening or a sliding mode of rock failure inherited versus syn folding fracture sets development can be studied using this mechanical model the workflow of this methodology was applied to the weber sandstone formation deformed by forced folding at split mountain anticline utah for which the different fracture sets were created and developed successively during the sevier and the syn folding laramide orogenic phases the field observations at the top stratigraphic surface of the weber sandstone lead to classify the fracture sets into a pre fold wnw ese fracture set and a ne sw fracture set post dating the former the development and relative chronology of the fracture sets are discussed based on the geomechanical modeling results starting with a 3d restoration of the split mountain anticline three fold fracture development models were generated alternately assuming that the wnw ese fracture set is either present or absent prior to folding process depending on the initial fracture configuration the calculated fracture patterns are markedly different showing that assuming a wnw ese joint set to predate the fold best correlates with field observations this study is a first step addressing the complex problem of identification of fold related fracturing events using an elementary concept of rock mechanics when tight to complementary field observations including petrography diagenesis and burial history the approach can be used to better constrain fractured reservoir characterization

gravity anomalies of 2 5 d multiple prismatic structures with variable density a marquardt inversion we present an inversion technique based on the marquardt algorithm to estimate the depth of a 2 5 d sedimentary basin in addition to the regional gravity anomaly that is associated with the residual gravity anomaly wherein the density contrast varies parabolically with depth forward modeling is carried out through a derived analytical gravity expression of a 2 5 d vertical prism inversion of a theoretical gravity anomaly with and without a regional gravity anomaly illustrates the procedure that it is found to be insensitive to the regional gravity effect furthermore the algorithm is exemplified with the gravity anomalies of the derived density depth model of the godavari subbasin india with a parabolic density profile resulting in a more consistent geological model rather than a constant density profile the main advantage of this method is that it works well even when the profile of interpretation does not bisect the strike length of the sedimentary basin

fluid storage and migration properties of sheared neptunian dykes abstract neptunian dykes are widely reported along the tethyan carbonate platforms and are commonly considered as subsurface baffles or barriers to fluid flow however the fluid storage and migration properties of sheared neptunian dykes are poorly known for this reason we investigate the inner structure and fluid flow properties of two neptunian dykes which can be characterized by different architectures if involved or not in brittle shearing processes the dykes strike ca wnw ese and crosscutting the tight jurassic limestones exposed at maranfusa mt nw sicily italy the unsheared and sheared neptunian dykes are almost sub vertical and at high angle with respect to the horizontal plane respectively the first one includes a homogeneous pelagic limestone infill whereas the second one includes a heterogeneous marl rich pelagic limestone infill and also thin veneers of tectonic breccias vertically persistent throughout the investigated outcrop the sheared neptunian dyke shows evidences of transtensional faulting which likely occurred during the early jurassic up to middle cretaceous times with throw up to 2 m the amount of fracture porosity and equivalent permeability are computed by integrating geological and structural field data with petrographic data obtained from selected samples and discrete fracture network modelling of geocellular volumes representative of the study outcrops results are consistent with the sheared neptunian dyke forming a combined barrier conduit permeability structure in which the low permeability and low porosity cataclastic core is flanked by a fractured damage zone that enhance the dyke parallel fluid flow in the subsurface accordingly the amount of fluid storage in the fractured damage zone is sensitively higher than in the surrounding limestone host rock data we present highlight that the m offset sheared neptunian dyke due to its inherited sedimentary infill is characterized by a permeability structure that it is often associated to large fault zones made up of cataclastic fault cores that impede the cross fault fluid flow

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

numerical simulation of fracture set formation a fracture mechanics model consistent with experimental observations a physically based model for the evolution of a single set of planar parallel fractures subject to a constant remote stress is presented the model simulates the mechanical interaction between fractures using a recently developed approximation technique for stress analysis in elastic solids with many fractures a comparison between experimental and numerical results shows that the model can accurately simulate the development of experimentally generated fracture sets once the flaw geometry is specified only one parameter controls the geometric evolution of the fracture set this parameter the velocity exponent relates fracture propagation velocity to stress concentration at the fracture tip monte carlo sensitivity analyses suggest that this parameter also controls the extent to which fracture growth is concentrated within zones or clusters similar analyses suggest that the extent of fracture clustering is less sensitive to the flaw density

use of clay mineral alteration patterns to define syntectonic permeability of joints cleat in pennsylvania anthracite coal abstract joints cleat in pennsylvania anthracite contain two distinct clay mineral assemblages both of which formed by alteration of preexisting kaolinite at peak metamorphic conditions during the alleghanian orogeny the first assemblage nh4 illite or pyrophyllite quartz formed by reaction of kaolinite with methane rich fluids derived from within the coal the second assemblage sudoite tosudite rectorite berthierine formed by the reaction of kaolinite with ferromagnesian bearing hydrothermal fluids which must have come from outside the coal in an earlier paper we suggested that the first assemblage indicated clay diagenesis in low permeability environments and that the second assemblage indicated clay diagenesis in high permeability environments if this premise is correct then the distribution of clay mineral alteration assemblages serves to define syntectonic permeability variations in coal cleat the first assemblage dominates in the coal matrix itself in isolated cleat in cleat that parallel the regional trend of alleghanian folds and in the mirror portions of cleat oriented perpendicular to the fold trends suggesting that these regions are low permeability environments the second assemblage dominates in the hackle fringe of interconnected cleat that trend perpendicular to the strike of the appalachian orogen suggesting that these regions are high permeability environments our results emphasize that syntectonic cleat permeability is a function of cleat orientation macroscopic cleat interconnectivity and orientation as well as microscopic cleat surface morphology

laser scanning and digital outcrop geology in the petroleum industry a review abstract the use of lidar light detection and ranging systems for modelling petroleum reservoir analogues has become increasingly popular over the past few years and there has been a proliferation of articles on the subject both on techniques and applications a review of the literature of recent years has been conducted focussing on the use of lidar data not only in petroleum geology related projects but also looking to the wider field of lidar usage to examine what other approaches may be of use to the petroleum geologist benefits of digital data acquisition are considered as well as a basic overview of data collection approaches use of a variety of attributes intensity colour dip azimuth co linearity co planarity among others is discussed as an aid to both manual and automated interpretation approaches integration of lidar data with other data types from traditional field data sedimentary logs for example and other digital data types such as multispectral and hyperspectral imagery and ground penetrating radar are discussed as a way of increasing the amount of information in the digital dataset the application of artificial intelligence approaches such as smart swarms and neural networks are considered as well as current developments in both hardware and software a variety of examples are given where lidar has been used in an innovative or interesting way showing the strength of this data acquisition approach when combined with appropriate interpretation and modelling techniques

modelling of heat transfer with the random walk method part 1 application to thermal energy storage in porous aquifers abstract this study examines the application of the random walk method of resolution in the modelling of thermal energy storage in fractured aquifers the media under consideration have a high degree of fracturing but a low porosity the aperture of the fracture is small in relation to its overall extent the customary method of resolution developed to investigate the transport phenomenon in such fractured media is first presented briefly next the stochastic equations of the energy displacement in fractured aquifers are developed depending on the statistical location of the energy particles in the media a stochastic approach is used to determine the flow velocity field the method is applied to different configurations of fracture networks for a single well system of aquifer thermal energy storage the temperature fields corresponding to a fractured aquifer and its equivalent porous configuration are compared an equivalent porous medium is not an adequate substitute for a fractured aquifer in such modelling the effect of the porosity on the energy storage is obvious the temperature of the extracted water and the energy recovery factor increase with the fracture porosity except in a highly anisotropic medium the orientation distribution of the fractures has little effect on the heat transfer in an aquifer without regional flow in the presence of a natural hydraulic gradient the energy recovery factor tends towards zero and the production temperature towards the original ambient temperature of the aquifer in this case a charge and discharge well pair proves to be a suitable alternative to the single well system

rock mass rating spatial estimation by geostatistical analysis abstract this work aims to estimate the rock mass rating of 200 km 2 area of the italian central alps along san giacomo valley province of sondrio the regional geological setting is related to the pennidic nappe arrangement which is characterized by the emplacement of sub horizontal gneissic bodies separated by meta sedimentary cover units the resulting rmr map can be a useful tool to forecast the quality of outcropping rock masses as well as to derive their geomechanical behaviour almost 100 geomechanical field surveys have been carried out in the research area in order to characterize the outcropping rock masses afterwards rock mass quality indexes have been evaluated in each surveyed site in order to estimate the rock mass rating values in un sampled locations different geostatistical techniques kriging and simulations have been applied using both bi dimensional and almost three dimensional approaches the validation process shows that kriging tends to produce smoothened distributions while conditional simulations allow respecting local extreme values although geostatistical analysis reveals that geomechanical properties show spatial correlations it is to remind that rock mass quality is strongly related to its geological and structural history

benefits of maximum likelihood estimators for fracture attribute analysis implications for permeability and up scaling abstract the success of any predictive model is largely dependent on the accuracy with which its parameters are known when characterising fracture networks in rocks one of the main issues is accurately scaling the parameters governing the distribution of fracture attributes optimal characterisation and analysis of fracture lengths and apertures are fundamental to estimate bulk permeability and therefore fluid flow especially for rocks with low primary porosity where most of the flow takes place within fractures we collected outcrop data from a fractured upper miocene biosiliceous mudstone formation california usa which exhibits seepage of bitumen rich fluids through the fractures the dataset was analysed using maximum likelihood estimators to extract the underlying scaling parameters and we found a log normal distribution to be the best representative statistic for both fracture lengths and apertures in the study area by applying maximum likelihood estimators on outcrop fracture data we generate fracture network models with the same statistical attributes to the ones observed on outcrop from which we can achieve more robust predictions of bulk permeability

origin of seaward dipping reflectors in oceanic crust off the norwegian margin by subaerial sea floor spreading a remarkable layered acoustic stratification is observed in the upper oceanic crust adjacent to the norwegian continental margin it comprises a seaward dipping complex of reflectors in the form of a wedge we suggest that it is a layered igneous sequence that results when crustal accretion occurs at a subaerial spreading axis and that this phenomenon may commonly occur during the earliest phase of ocean basin genesis

marquardt optimization of gravity anomalies of anticlinal and synclinal structures with prescribed depth dependent density an inversion technique using the marquardt optimization is developed to interpret the gravity anomalies due to anticlinal and synclinal structures with density contrast varying continuously with depth the algorithm simultaneously estimates the parameters of the respective models in addition to the regional gravity background that is invariably associated with the residual gravity anomaly forward modelling is realized through analytically derived gravity expressions for the respective models in the space domain the efficacy of the inversion is demonstrated with the gravity anomaly due to a theoretical model in each case with and without the regional background in addition the applicability is illustrated using the gravity anomalies of the pays de bray anticline situated north west of paris france the interpreted depth of the pays de bray anticline using the present inversion compares well with the drilling depth

application of the discrete fracture network concept with field data possibilities of model calibration and validation the uneven flow distribution observed in a migration experiment in the stripa research mine is analyzed with a discrete fracture network model data on the measured inflow distribution and trace geometry in the experimental drift are the basic sources for estimation of the model parameters direct estimates cannot provide a unique definition of input data to the model thus different combinations of input data need to be analyzed in the network model detailed measurements of the inflow distribution in the experimental drift provided an opportunity to determine the model parameters through calibration in the network model calibration was performed on the mean inflow distribution of flow and trace geometry observed in the roof of the experimental drift the simulation results show that the model can be calibrated to produce an areal flow distribution that is consistent with the measured one the uncertainties in the input parameters are thus reduced but different combinations of input data are still possible the calibration simulations show that the length of conductive fractures per area might be used as a calibration parameter simulations based on different combinations of fracture size and density but with the same length of conductive fracture traces produced similar flow distributions the validity of the calibrated model is explored by predicting the flow into the boreholes at the experimental site the resulting inflow distributions accord well with those measured in two of the three boreholes the properties of the third borehole which differ substantially from the other two could not be explained by the simulation results

directional semivariogram analysis to identify and rank controls on the spatial variability of fracture networks abstract in this study the directional semivariogram is deployed to investigate the spatial variability of map scale fracture network attributes in the paradox basin utah the relative variability ratio r is introduced as the ratio of integrated anisotropic semivariogram models and r is shown to be an effective metric for quantifying the magnitude of spatial variability for any two azimuthal directions r is applied to a gis based data set comprising roughly 1200 fractures in an area which is bounded by a map scale anticline and a km scale normal fault this analysis reveals that proximity to the fault strongly influences the magnitude of spatial variability for both fracture intensity and intersection density within 1 2 km additionally there is significant anisotropy in the spatial variability which is correlated with trends of the anticline and fault the direction of minimum spatial correlation is normal to the fault at proximal distances and gradually rotates and becomes subparallel to the fold axis over the same 1 2 km distance away from the fault we interpret these changes to reflect varying scales of influence of the fault and the fold on fracture network development the fault locally influences the magnitude and variability of fracture network attributes whereas the fold sets the background level and structure of directional variability

some aspects of the late tertiary geomagnetic field in iceland summary in 1972 78 the late n d watkins and others carried out ajoint field programme of geological mapping in the mio pliocene flood basalts of iceland including sampling for k ar dating and palaeomagnetic research the major part of the palaeomagnetic sampling is represented by 2462 lavas in five long composite sections through the lava pile this paper deals with various statistical properties of this data set it is concluded that geomagnetic reversals occur more frequently than is assumed in the current ocean floor polarity time scale there is no evidence for significant asymmetries between normal and reverse polarity states of the field neither as regards chron lengths secular variation or virtual dipole moment magnitude intensities of remanence in these lavas are shown to be well approximated in terms of a hyperbolic distribution the latitude distribution of virtual magnetic poles can be fitted with a bingham function having k 4 5 and low latitude poles do not occur preferentially in any particular longitude interval

groundwater flow system inferred from hydraulic stresses and heads at an underground lpg storage cavern site underground liquefied petroleum gas lpg storage caverns were constructed below the groundwater table to contain pressurized gas by groundwater pressure continuous and regular groundwater monitoring data were used to analyze whether the gas containment condition was satisfied or not the monitoring data included time series analysis of hydraulic heads gas and groundwater pressures and groundwater chemistry through cross correlation analyses of the time series data the major factors causing hydraulic head fluctuation were found to be groundwater recharge from precipitation and cavern gas pressures hydraulic head and hydrochemical data indicate that a fault zone acts as the groundwater recharge zone and water curtain tunnels reduce head fluctuations

hydrological modeling in the karst area rižana spring catchment slovenia karst aquifers are known for their heterogeneity and irregular complex flow patterns which make them more difficult to model and demand specific modeling approaches this paper presents one such approach which is based on a conceptual model the model was applied in a karst area of the catchment of ri ana spring 200 km it is based on the mike she code and incorporates the main hydrological processes and geological features of the karst aquifer diffuse and concentrated infiltration allogenic recharge quick and slow groundwater flow shifting groundwater divides and groundwater outflow from the catchment area modeling of evapotranspiration and flow in the upper part of the unsaturated zone is more detailed for the modeling of groundwater flow in the karst aquifer a conceptual model was applied which uses drainage function for the simulation of groundwater flow through large conduits karst channels and large fissures the model was calibrated and validated against the observed ri ana spring discharge which represents a measured response of the aquifer the results of validation show that the model is able to adequately simulate temporal evolution of the spring discharge measured by nash sutcliffe coefficient 0 82 as well as overall water balance

a geostatistical framework for incorporating seismic tomography auxiliary data into hydraulic conductivity estimation abstract a geostatistical approach is presented for the inclusion of seismic tomography data and sonic log data into the estimation of hydraulic conductivity the procedure accounts for the errors in seismic tomography inversion and for the correlation of such errors the proposed methodology consists of two steps 1 the cross variogram inference is carried out using only the data at the wellbore both hydraulic and seismic 2 a co kriging procedure takes the cross well data into account to interpolate between boreholes no postulated a priori relationship is needed in order to illustrate the methodology a synthetic data set is generated on the basis of evidence from published case studies and simplified physical considerations the numerical experiments show that the choice of the excitation frequency is critical a trade off exists between the need for a high resolution survey asking for higher frequencies and the need for a good correlation between hydraulic conductivity and seismic properties asking for frequencies below the squirt frequency of the medium in the simulation using seismic data with the best excitation frequency 1 khz in this case the mean squared error of the hydraulic conductivity estimate is two thirds lower than using hydraulic data alone it is important to note also that only a part of the interwell region is adequately sampled by the tomographic experiment such a region can be readily identified by calculating the energy of the quasi null space through singular value decomposition of the tomographic matrix in planning this type of experiments it is necessary to carefully verify case by case whether the adopted range of high frequencies does not prevent the seismic energy from propagating effectively from sources to receivers

investigation of the permeability anisotropy of 2d fractured rock masses abstract a hydro geometric anisotropy factor is derived for better correlation with the permeability anisotropy of field scale fractured rock masses the hydro geometric anisotropy factor considers the orientation length spacing and hydraulic aperture properties of a discrete fracture network numerical simulations are carried out by using a pipe network method which simulates the fractures as connected and directed pipes obeying darcy s law to validate the correlation between the hydro geometric anisotropy factor and the permeability anisotropy of fracture networks fracture patterns from simple to complex with a scale of 10 m by 10 m are generated to study the effects of different fracture distributions on the hydro geometric anisotropy of fracture networks and thus on the permeability anisotropy it is found that the aperture size and distribution have a significant effect on the permeability anisotropy that affects the main permeable direction of the fracture networks the permeability anisotropy varies following a power relation with the change of the intersection angle between two fracture sets varying the number and length ratio of the fracture sets also alters the permeability anisotropy in all fracture patterns the hydro geometric anisotropy factor gives an accurate correlation with the permeability anisotropy an anisotropic conductivity index is further defined to evaluate the directional hydraulic connectivity of the fracture system based on this approach the permeability anisotropy of a fracture network system can be quickly assessed through the correlation with the hydro geometric anisotropy factor and the anisotropic conductivity index

integrated investigations of karst phenomena in urban environments abstract theories that describe karst systems are often limited to conceptual models however engineering projects within complex karst systems demand the development of tools that allow site specific descriptions of the hydrogeologic settings and calibrating the processes of karst evolution subsidence of a river dam and an adjacent highway both constructed on gypsum containing rock southeast of basel switzerland required remedial construction measures a monitoring network was set up to safeguard surface and subsurface water resources during the construction measures the primary project goal was to develop tools that enable a continuous characterization of the groundwater flow regime and that facilitate the evaluation of the long term performance of the infrastructures investigative methods included high resolution 3d hydrogeological modeling and the integration of geological hydrometrical and hydrogeophysical field data of varying quality particular focus was placed on the hydraulic behavior of the complex conduit system results help to understand the evolution of distinct karst features and zones of preferential flow the location of fracture zones and parts of the old meandering river course playing a major role in the karst evolution process could be identified together with the hydrometrical investigations and hydrogeological modeling the evolution of the karst system and its dynamics can be interpreted in relation to the groundwater flow regime

a new method of characterizing fissured media by pumping tests with observation wells abstract an analogy has been defined between the relation s r t at n and the elementary solution derived from the general flow equation describing fluid flow in fissured media assuming a non integer flow dimension that analogy can be used to characterize a fissured medium by parameters that are similar to those describing a porous reservoir if at least two observation wells are available and if flow involves a sufficient number of fractures the flow system behaves as a fractal object with observation wells located along axes in several directions anisotropy can be characterized two field applications illustrate the proposed method

using the continuum approach to model unsaturated flow in fractured rock the appropriateness of using the continuum approach for simulations of unsaturated flow through fractured rock is examined in a numerical study of water seepage into an underground opening a continuum model is calibrated against data generated with a high resolution model that created discrete flow and seepage behavior probabilistic predictions of injection data and seepage rates are then compared to the values from the discrete model the study shows that reasonable results can be obtained with a calibrated continuum model even for fractured systems in which the underlying flow processes are discrete calibration is a crucial step in this approach because it yields effective model related and process specific parameters the impact of discretization on the estimated parameters is discussed prediction uncertainty is evaluated by means of monte carlo simulations including both the impact of parameter uncertainties and the effect of local heterogeneity in this paper the advantages and limitations of the continuum approach are discussed from a practical perspective which includes a critical examination of project objectives data needs robustness of assumptions and prediction uncertainty

a three dimensional model to simulate jointnetworks in layered rocks modelling the discontinuity network of fractured reservoirs may be addressed 1 by purely stochastic means 2 with a fractal approach or 3 using mechanical parameters describing the spatial organisation of fracture systems our paper presents an approach where the geometrical properties of the fracture networks are incorporated in the form of both statistical and mechanical rules this type of approach is particularly suitable to model stratified fractured rock masses comprising two orthogonal families of joints and a family of sedimentary discontinuities their geometrical arrangement is governed by two kinds of rules based on 1 statistical parameters such as the mean standard deviation of joint length and of bed thickness both determined by field observations and 2 geometrical parameters that result from genetic processes inferred from field observations and analogue experiments on the nucleation and propagation mechanisms of joints using these parameters we generate realistic networks in

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

utilisation d un modele stochastique de reseaux de fractures pour etudier les proprietes hydrauliques d un massif fissure this study of the hydraulic properties of a fractured rock mass is based on data from field injection tests and fracture measurements and on simulations of the fracture system in the bedrock upstream from the daniel johnson dam at manic 5 analysis of water injection tests indicates that the bedrock can be divided into two zones with respect to the permeability the more permeable zone which is the object of this study shows a log normal distribution of the hydraulic conductivities using several stochastic simulations of fracture networks the fracture aperture has been adjusted gradually to reproduce the rock mass permeability estimated from injection tests the results show that the fracture system geometry as well as the fracture porosity and the fracture lengths and densities influences widely the hydraulic properties of a fractured medium and particularly the fracture porosity also the estimation of the fracture porosity is sensitive to a number of other factors including the assumed hydrauli