dual porosity mechanism for transient groundwater and gas anomalies induced by external forcing abstract the geochemical response of groundwater to external forcing is studied in a tunnel hosted in fractured gneiss near and above an artificial lake having large water level variations dripping waters have been monitored in two zones characterized by highly different flow rates representing different contributions of water from matrix porosity and fractures transient increases of sulfate and magnesium concentrations observed in both zones are not related to meteorology but associated with radon bursts into the tunnel air this indicates that transient enhancement of conductance with discharges of saline water and radon from the matrix porosity to the fractures is a mechanism able to produce both groundwater and gas anomalies in response to hydrogeological or mechanical processes such as increases in pore pressure or changes in crack geometry besides its applications to environmental issues the proposed discharge mechanism may be relevant for the understanding of geochemical precursors of earthquakes as an alternative to aquifer mixing

developments of the icp linked decrepitation technique for the analysis of fluid inclusions in quartz abstract further developments in the analysis of fluid inclusion decrepitates by inductively coupled plasma emission spectroscopy icp are outlined decrepitates from samples of quartz have been analysed and give useful results as several mechanisms of transfer of material into the plasma are feasible it is important that the temperature of heating should be restricted to the temperature range of decreptiation however contamination by silicate phases in the quartz appears to be of little significance reproducibility in our analyses is usually better than 30 relative standard deviation rsd and most of this appears to be due to heterogeneity in the abundance of fluid inclusions we have been able to estimate the ore metal content of some hydrothermal fluids from sw england and have obtained values in the range one hundred to a few thousand parts per million for some elements cu pb zn sn and b because of the sensitivity of the method we feel that its greatest potential is in the field of routine mineral exploration and we have had considerable success in this application

paleostress and statistical analysis using quartz veins from mineralized and non mineralized zones application for exploration targeting abstract quartz vein orientations thickness and spacing data are analyzed from 10 transects each of mineralized and non mineralized zones of gadag region which is a gold bearing terrain within the dharwar craton southern india paleostress analysis reveals that the veins emplaced when fluid pressure pf varied from pf 2 intermediate principle stress to pf 2 to pf

the importance of small scale faulting in regional extension a recurring observation in many studies of extensional basins has been that the amount of extension visible on normal faults for example on seismic reflection profiles is significantly less than the amount of extension indicated by crustal thickness and thermal subsidence1 5 one mechanism suggested to account for this discrepancy is small scale faulting with offsets too small to be resolved seismically6 7 but earthquake studies8 10 indicate that small faults are responsible for only a small fraction of the total seismic moment in an active area scholz and cowie11 have recently attempted to extend this approach to the total strain at the end of a finite deformation interval by combining scaling laws describing the distributions of fault lengths and displacements here we present fault displacement data that directly conflict with scholz and cowie s conclusions and imply that up to 40 of the extension may be missed by summing fault offsets on basin profiles the fault population at the end of a long deformation interval may differ substantially from that responsible for the earthquake population at any one time

an integrated workflow for fracture characterization in chalk reservoirs applied to the kraka field abstract oil and gas production of tight chalk reservoirs frequently rely on the presence of natural fractures which increases the effective permeability of the reservoirs fracture characterization is therefore imperative in optimizing production schemes and obtaining economically viable recovery factors subsurface fracture characterization is often deemed challenging as the available data is typically of varying age and quality and represents different scales we have developed an integrated workflow for fracture characterization in chalk to address these challenges the workflow is based on data from borehole images cores and seismic these data are typically available for most chalk and hydrocarbon fields the interpreted borehole image dataset contains over 17 000 manual dip picks ensuring a statistically viable base a total of 150 m of core is available from 3 wells the applied 3d seismic cube covers an 8 5 km hydrocarbon chalk field in the danish north sea in this workflow the scale gap between the data sets is bridged by the introduction of two ant tracked attribute volumes which display structural trends below the resolution of amplitude seismic further insight into the intricacy of subsurface fracture systems is obtained from fracture density logs which provide an opportunity to study spatial distribution of fractures as well as a qualitative measure of fracture clustering cumulative density distribution plots and calculation of the variation coefficient of fracture spacing provide a more quantitative analysis of the fracture distribution the workflow presented here in a step by step manner is a general approach applied to data from the kraka field of the danish north sea in the kraka field the usage of this integrated approach shows that the fracture pattern in this region is more complex than previously suggested probably controlled by the regional maximum horizontal stress and salt movements

faults and fractures in the gallery 04 of the mont terri rock laboratory characterization simulation and application this paper deals with the reconstruction of a fracture network observed in an underground gallery of a tunnel buried in clay stones in switzerland below mont terri the trace maps of the gallery 04 and of the ez g niche of this site have first been digitized and used in various ways to characterize the data the traces have been divided into two groups i e the pre existing faults in the gallery and the fractures of the excavated damaged zone edz in the niche each group has been analyzed individually the number of data for the faults has turned out to be statistically significant while it was very limited for the edz fractures for both cases the major statistical characteristics of the traces have been extracted and a reconstruction procedure developed and tested a full example has been worked out a gallery immersed in a reconstructed fractured porous medium has been meshed and the electrical field created by a dipole at the wall calculated by solving the three dimensional laplace equations in the fractures and in the porous medium

crustal stress determination from boreholes and rock cores fundamental principles abstract obtaining quantitative information on the state of stress in the crust can only be accomplished by accessing the zone of interest by drilling the borehole cavity however disrupts the virgin stress state by concentrating stresses in predictable patterns with a number of consequences at sufficiently low stress magnitudes the concentrated stresses amplify the elastic anisotropy azimuthally around the borehole because the elastic properties of most rocks depend nonlinearly on stress at higher levels the stresses damage then fracture the rock near the wellbore wall or within a growing core stub indeed almost all of the borehole techniques indirectly measure stress through these manifestations of the concentrated stresses this contribution reviews at a fundamental level the concentration of stresses by the borehole the effects on the materials in the borehole s vicinity and how these are used to infer stress states stress concentrations applied to rocks which are generally nonlinear elastic materials induce both radial and azimuthal variations in elastic wave speeds near the borehole that can be used to infer stress directions from advanced acoustic logging methods hydraulic fractures initiate propagate and remain propped open by measured pressures that can be interpreted with knowledge of the stress concentrations to obtain quantitative stress magnitudes at higher stress levels the rock fails producing borehole breakouts or drilling induced tensile fractures both of which are indicative of stress directions and can be used to constrain stress magnitudes similarly the various styles of drilling induced core fractures indicate both stress directions and the faulting environment encountered unfortunately no method currently allows for complete determination of the stress tensor using a number of different but complementary techniques is necessary to best constrain in situ stress states

laboratory measurement of hydrodynamic saline dispersion within a micro fracture network induced in granite we report the first measurements of hydrodynamic dispersion in a microfractured granite using a combination of novel techniques a fracture network was induced in a cylindrical plug of ailsa craig micro granite by thermal stressing to produce an isotropic network of fractures with an average aperture of 0 3 m a density of approximately 4 10 4 fractures mm 3 and a permeability of 5 5 10 17 m 2 after saturating the cores with 0 01 m nacl solution a step in the concentration profile to 1 m was advected into the plug at flow rates of 0 07 to 2 13 cm 3 h 1 the longitudinal electrical impedance of the plug was measured continuously as the solute front advected through its length until the plug was saturated with the concentrated electrolyte analysis of the impedance versus time relationships allows the derivation of the longitudinal dispersion coefficient dl and hydrodynamic retardation rh the peclet number dispersion relationship for the micro fracture network is very similar to that predicted for other radically different fracture networks thus dispersion may be more dependent on fracture connectivity and length than fracture density and display a relationship similar to that shown by particle beds and clastic sandstones the high retardation values observed 2 2 4 9 reflect flow behaviour within a fracture network with a proportion of blind sections and demonstrates how such networks can slow the advance of conservative solute components 2007 elsevier b v all rights reserved

earthquake faulting as a structural process abstract structural geology is concerned with the history of movement in the earth s crust and the processes by which displacements occur in the upper one third to one half of deforming continental crust displacement is accommodated largely by seismic slip increments on existing faults it follows that earthquakes and related processes are an integral part of structural geology traditionally structural geologists have been preoccupied with the complexity of the finite deformation within fault zones and with the stress states prevailing at the initiation of faults in intact crust future structural work should be directed more towards understanding the dynamic character of fault reactivation during incremental slip and related effects questions of interest include rheological and geometrical controls on the initiation perturbation and termination of ruptures directivity effects associated with rupture propagation the recognition of structures resulting from repeated stress cycling within seismogenic crust and identification of structural features diagnostic of shear stress levels during faulting structures arising from the inter relationships between slip episodes and induced fluid flow are of special importance because these dynamic fault processes appear influential in the development of much fault hosted mineralization mesothermal gold quartz lodes hosted in high angle reverse shear zones of mixed brittle ductile character form illustrative examples of structures that arguably can only be interpreted by seismo structural analysis embodying the concepts listed above

three dimensional characterization of a fractured granite and transport properties a three dimensional fracture network in a granite block is reconstructed from a series of experimental serial sections it is visualized and its most important geometrical characteristics are studied namely the orientation of the fractures the connectivity of the fractures the number of cycles per unit volume the distributions of surface areas and of the intersection lengths and the number of finite solid blocks isolated in the solid matrix by the network though the network mostly consists of two families of fractures it is interesting to note that a simple model of randomly oriented monodisperse hexagons often yields a good order of magnitude for the various geometrical properties which have been measured on the real block the flow properties are then studied examples of velocity field are provided as well as histograms of velocities the permeability tensor is determined and is found to be in good agreement with snow s formula finally dispersion is analyzed by means of a random walk method histograms of arrival times are provided and interpreted in terms of dispersion tensor

the effect of sample disturbance on laboratory properties of lac du bonnet granite laboratory properties of lac du bonnet granite samples collected at depths ranging from near surface to 1000 m were established the laboratory properties indicated that either the in situ properties were changing with depth or the samples were changing with depth comparison of p wave velocities in the samples and in situ confirmed the latter i e sample disturbance was affecting the laboratory properties the strength of the damaged samples indicated that sample disturbance affected the cohesion of the material not the frictional properties and that the cohesion loss cannot be accounted for by applying a confining stress sample disturbance started to affect the laboratory properties of lac du bonnet granite when the maximum far field in situ stress exceeded about 10 of the unconfined compression strength key words sample disturbance core discing cohesion brittle rocks damage microcracks stress dependent young s modulus

a k feldspar breccia from the mo cu stock work deposit in the galway granite west of ireland a k feldspar breccia spatially associated with the mo cu mineralization of a stockwork in the late caledonian galway granite at mace head is described for the first time detailed mapping reveals a network of breccia pods and veins over an area of approximately 6000 m 2 the breccia is clast supported and is composed of sub angular fragments of perthitic k feldspar megacrysts 2 rich fluids the residue of these fluids crystallized to form the breccia matrix the formation of the breccia predates the mineralized quartz veins of the mo cu stockwork it is concluded that the breccia formation is genetically related to ore forming processes in the galway granite

study of the effects of feldspar and mica contamination upon the analysis of fluid inclusions by the decrepitation icp method abstract the effects of feldspar and mica contamination on the analyses of fluid inclusion contents in quartz from granitic rocks are evaluated when the fluid inclusions are analysed by the decrepitation inductively coupled plasma emission spectroscopy d icp method

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

a fractal relationship between vein thickness and gold grade in drill core from la codosera spain analysis of quartz vein thicknesses and gold grades in drill core from western spain indicates that both approximate a power law distribution suggesting an underlying fractal relationship log log plots of cumulative frequency n against vein thickness t show systematic changes in relation to gold grade the exponent d in a power law of the form n c t super d is lower for higher gold grades indicating that a greater proportion of the dilation is taking place on the thicker veins which are interpreted as providing interconnected conduits for gold bearing fluids thus monitoring the vein thickness distribution may provide a means of discriminating mineralized and barren structures in vein hosted mineral deposits

fractal geometries of vein systems and the variation of scalingrelationships with mechanism abstract investigation of vein geometries has identified empirical relationships which allow extrapolation of outcrop scale observation to larger scales measurements of vein shapes and aspect ratios in a number of different environments demonstrate that veins follow similar empirical scaling laws to those of faults geometries of veins are easier to characterise accurately than faults because their thickness is related to the variation in displacement from zero at their tips to a maximum at their thickest point vein sizes obey the empirical relationship l kta where l length in mm t thickness in mm 20 1 this suggests that veins amplify initially by inflation and subsequently by elongation

trace analysis for fracture networks of any convex shape 1 statistical properties of traces of fracture networks are related to the fracture volumetric density and to the average fracture surface and perimeter these relations which hold whatever the fracture shapes provided that they are convex can be extended to anisotropic networks these relations can be used to check the statistical consistency of field data and to obtain macroscopic quantities such as the dimensionless density which controls the geometric and transport properties of fractured media a field example of anisotropic subvertical fractures whose sizes obey a power law is analyzed along these lines

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

structural control of low sulfidation epithermal gold mineralization in the rosario bunawan district east mindanao ridge philippines the rosario bunawan district is situated about 200 km north of davao city the capital of the mindanao island southern philippines gold is produced from the co o mine containing about 2 034 000 t of ore at 10 9 g t au and in numerous small scale operations by local miners epithermal gold mineralization in the rosario bunawan district and the co o mine is confined to narrow 0 2 4 m low sulfidation quartz chalcedony calcite veins in volcanic and volcaniclastic wall rocks three major vein orientations are distinguished 1 the nnw sse trending set with a sinistral strike slip sense of deformation philippine fault trend 2 the ene wsw trending dextral strike slip set palawan trend and associated veins in the riedel geometry and 3 the wnw ese trending conjugate set co o trend three structural stages are defined 1 extensional shear or shear veins formed in the co o the philippine fault and palawan trends during regional nw se compression and near vertical vein opening d1 2 reactivation of veins in the philippine fault veins associated with the palawan and to a lesser extent the co o trends during e w compression and near horizontal n s oriented vein opening d2 new d2 extensional shear or shear veins formed in the philippine fault and structures associated with the palawan and associated riedel trends 3 the d3 stage block faulting subsequently displaced all of the auriferous veins the auriferous rosario bunawan district is situated between two splays of the philippine fault which acted as a lateral ramp system during the oblique convergence of the philippine sea plate and the eurasian plate the oblique convergence resulted in a change from a compressional d1 to a transpressional d2 regime which was a prerequisite for the two stage vein opening and hydrothermal mineralization leading to an economic gold enrichment d1 compressional tectonics may have caused an elevated geothermal gradient in shallow crustal levels forming the heat source for the fluid plumbing system which is at variance to typical epithermal deposits formed in extensional zones d2 thrusting of a limestone nappe together with syn tectonic diorite intrusions may have further increased the geothermal gradient maintaining the fluid plumbing system the limestone nappe may at the same time have represented an aquitard forcing the hydrothermal fluids into the volcanic and volcaniclastic wall rocks which is regarded as critical for the two stage gold mineralization in the rosario bunawan district

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

fractal vein distributions within a fault fracture mesh in an exhumed accretionary melange chrystalls beach complex new zealand a well developed fault fracture mesh is observed in the chrystalls beach complex an accretionary melange within the otago schist on the south island of new zealand in this study an analysis of vein thicknesses and clustering of veins is presented both shear and extension veins have a power law thickness distribution measures of vein spacing best fit a power law distribution but a small data set limits this interpretation to a small fractal range vein clustering varies from random to moderately clustered between outcrops and is the greatest where a large proportion of relatively competent blocks occurs within the melange fractures are distributed within the melange matrix and this localized deformation requires heterogeneity in rheology and or fluid pressure distribution whereas pervasive distributed deformation occurs in relatively homogeneous rock the overall trend of this deformation being mainly accommodated by thin veins required that new fractures formed preferentially over refracturing existing veins which highlights the distributed nature of deformation within a fault fracture mesh the predominance of new fractures may result from vein material being stronger than the cleaved wall rock such that wall rock failure occurred instead of reopening of pre existing shear and extension veins

fracture size estimation using data from multiple boreholes abstract the size of a fracture within a rock mass can be obtained using data sampled from boreholes or exposed surfaces in this study fracture sizes are estimated using data from multiple boreholes the fractures are assumed to be elliptical all having the same aspect ratio but not necessarily occurring parallel to each other formulae for estimating the mean and standard deviation of the characteristic fracture size are developed by considering the number of intersections between the fractures and the boreholes a method is proposed to infer the probability density function of the fracture size from the number of fractures which is obtained by random sampling of fractures in adjacent boreholes the fracture distribution is assumed to follow the form of a fractal exponential or lognormal distribution the performance of the method is validated using monte carlo simulations with different inputs of size distribution fracture density orientation and mean fracture size

hoek brown parameters for predicting the depth of brittle failure around tunnels a review of underground openings excavated in varying rock masstypes and conditions indicates that the initiation of brittlefailure occurs when the damage index di expressed as theratio of the maximum tangential boundary stress to the laboratoryunconfined compressive strength exceeds approx0 4 when thedamage index exceeds this value the depth of brittle failure around a tunnel can be estimated by using a strengthenvelope based solely on cohesion which in terms of thehoek brown parameters implies that m 0 it is proposed that inthe brittle failure process peak cohesion and friction are notmobilized together and that around underground openings thebrittle failure process is dominated by a loss of the intrinsiccohesion of the rock mass such that the frictional strengthcomponent can be ignored for estimating the depth of brittlefailure an essential component in designing support for theopening case histories were analyzed using the hoek brownfailure criterion with traditional frictional parameter

geometrical and fractal analysis of a three dimensional hydrothermal vein network in a fractured granite abstract a three dimensional study of a fracture network has been performed on a 0 66 m 3 block of fine grained granite from la peyratte deux sevres france the block was sawn in nine parallel plates the fractures associated with altered haloes were mapped for each plate using a photographic method the nine fracture sets were subjected to an analysis of the percolated network based on a measurement of the width of altered haloes developed around fractures hydrothermal alteration is created by circulation of a certain amount of fluid flow in the rock we assume that the alteration zone width is proportional to fluid mass flow the width of alteration zones will give a good idea of the path preferentially followed by fluids the relation between fracture length and width of the alteration zone shows that the total fracture network consists in fact of two sorts the largest fractures surface 0 1 m 2 create a loose and poorly interconnected pattern in the block however they have developed wide alteration zones 3 mm and have then had a great role in fluid conduction they represent only 10 of the fractures but are responsible for 47 of alteration in volume approximately 80 of these fractures with wide alteration zones are oriented in the same direction this main network is linked to a more dense highly interconnected system made of shorter fractures with narrower altered zones fractal analysis has also been performed on pictures of the fracture patterns using the linear cantor s dust method fractal dimension values d indicate an anisotropy of fracture distribution on each plane moreover when the planes are compared to one another in succession variations of d values can be noticed indicating an inhomogeneity in the third dimension the study of such a three dimensional fracture set shows that fluids follow preferential paths within a fracture network and helps the understanding of fracture distribution

fractal relations for the diameter and trace length of disc shaped fractures analytic relations are developed between the fractal parameters of a random isotropic population of disc shaped fractures and the parameters of the corresponding population of fracture traces expressed in outcrop these relations indicate that a fractal distribution of fracture diameters translates to a fractal distribution of trace lengths and that the parameters for diameter may be uniquely determined from the parameters for trace length probabilistic results demonstrate the accuracy of the analytic relations and identify nonideal behaviors at the limits of the computed trace length data it is expected that these relations will be useful in the three dimensional characterization of fracture systems in rock from in situ trace length data

fracture size and transmissivity correlations implications for transport simulations in sparse three dimensional discrete fracture networks following a truncated power law distribution of fracture size we characterize how different fracture size transmissivity relationships influence flow and transport simulations through sparse three dimensional discrete fracture networks although it is generally accepted that there is a positive correlation between a fracture s size and its transmissivity aperture the functional form of that relationship remains a matter of debate relationships that assume perfect correlation semi correlation and non correlation between the two have been proposed to study the impact that adopting one of these relationships has on transport properties we generate multiple sparse fracture networks composed of circular fractures whose radii follow a truncated power law distribution the distribution of transmissivities are selected so that the mean transmissivity of the fracture networks are the same and the distributions of aperture and transmissivity in models that include a stochastic term are also the same we observe that adopting a correlation between a fracture size and its transmissivity leads to earlier breakthrough times and higher effective permeability when compared to networks where no correlation is used while fracture network geometry plays the principal role in determining where transport occurs within the network the relationship between size and transmissivity controls the flow speed these observations indicate dfn modelers should be aware that breakthrough times and effective permeabilities can be strongly influenced by such a relationship in addition to fracture and network statistics this article is protected by copyright all rights reserved

a note on the angular correction applied to fracture intensity profiles along drill core we derive the angular correction that has to be applied to borehole fracture intensities to recover the actual three dimensional distribution when the fracture networks have a length distribution we assume that the fracture intensity is calculated from the fractures that fully transect the core because of the length distribution the classical terzaghi correction which involves the cosine of fracture dip is no longer valid solutions have been calculated in the specific case of fractal fracture networks with power law length distribution we show that the terzaghi correction may significantly overestimate the frequency of fractures subparallel to the borehole the correction procedure proposed here was tested on a fracture database recorded at a study site for a repository of spent nuclear fuel located in se sweden with three outcrop maps and three boreholes a consistency between the dip distributions of outcrops and boreholes was achieved when applying the angular correcting term calculated with the power law length distribution deduced from outcrop maps

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

a method for estimating subsurface fracture density in core quantitative information on fracture density may be used to delineate areas structures or lithologies that have a relatively high density of subsurface fractures a quantitative estimate of subsurface fracture density can be obtained from core data previously no unequivocal technique existed for estimating the degree of subsurface fracturing from oil well core data the spacing of joints at outcrops is commonly observed to be a direct linear function of the thickness of the jointed bed our method for estimating subsurface fracture density is a statistical estimate based on this empirical relation the probability of a given number of core fracture intersections is determined for a range of possible fracture densities after accounting for core diameter variations bed thickness geometric corrections necessitated by bedding dip and variations in fracture pitch the true fracture density is then estimated by finding the fracture density value that yields a calculated number of fractured beds equal to the observed number of fractured beds the technique was tested by measuring fracture density in the field at 2 outcrops hypothetical cores were constructed on photographs of the outcrops and estimates of fracture density from the core data yielded values in agreement with those obtained by field measurement the core data required for estimation of fracture density are core diameter bed thickness number of beds fractured and unfractured and the angles between core axis bedding and fractures the mathematics should be programmed on a computer for ease of use

predicting variability in joint frequencies from boreholes abstract joints in rock are not evenly spaced but commonly show clustering this suggests that boreholes that are a short distance apart can intersect very different numbers of joints a simple 1d model is used to illustrate variability in joint frequencies from vertical wells intersecting steeply dipping joints the model indicates that raw joint frequencies logged from core or borehole images can give unreliable inputs into reservoir models especially when the joints are clustered and variations occur over scales that are much smaller than the resolution of seismic surveys or the grid blocks used in reservoir simulations variability in joint frequencies from deviated or horizontal wells can be used however to test the variability in joint frequencies from vertical wells

high silver content of fluid inclusions in quartz from guadalcazar granite san luis potosi mexico a contribution to ore genesis theory besides sodium and potassium manganese and iron were found in significant amounts the results confirm that the base metal and silver transporting capability of some early magmatic fluids is considerable chloride complexes were the most favorable species for transporting silver and base metals an electron probe in the energy dispersive mode was used to analyze the precipitates formed upon the decrepitation of fluid inclusions modified journal abstract

antitaxial crack seal vein microstructures and their relationship to displacement paths abstract the microstructures developed in an example of a syntectonic crack seal vein indicate that antitaxial fibres do not necessarily track the incremental opening history during crack seal vein growth this observation serves as a caution against the uncritical use of fibrous microstructures to make inferences about displacement histories during fibre formation it is demonstrated that crack seal processes can lead to the development of both irregular and laminated vein microstructures as well as fibrous microstructures the types of microstructures which develop in crack seal veins and the extent to which they reflect the opening paths of veins depend on a range of factors the most important of these include the nucleation and growth kinetics of phases precipitated from fluids in opening fractures and the location of sites of material accretion during successive crack seal increments

detectability and significance of 12 hr barometric tide in radon 222 signal dripwater flow rate air temperature and carbon dioxide concentration in an underground tunnel summary searching for small periodic signals such as the 12 hr s2 barometric tide and monitoring their amplitude as a function of time can provide important clues on the complex processes affecting fluid transport in unsaturated fractured media under multiple influences here first we show that a modified spectrogram analysis msa is more efficient than simple fourier transform to reveal weak periodic signals secondly we show how transient periodic signals can be monitored as a function of time using spectrograms these methods are applied to time series of radon and carbon dioxide concentration dripwater flow rates and air temperature measured during several years in the roselend dead end tunnel located in the french alps near an artificial lake a weak s2 line is evidenced in radon concentration with enhanced amplitude during transient radon bursts similarly the s2 line is observed using msa in dripwater flow rates which sample mainly fracture flow as suggested by a hydrochemical analysis while it is not seen in dripwater flow rates sampling matrix flow in the absence of a strong 24 hr line the presence of a s2 line suggests sensitivity to barometric pressure and thus a significant advective contribution in radon and some dripwater transport no s2 line is observed in the carbon dioxide time series the temporal structure of the s2 component however is not similar in the radon concentration and the dripwater flow rates suggesting in particular that dripwater does not play a significant role in the generation of radon bursts temperature time series exhibit a significant s2 contribution induced by atmospheric pressure spatially organised in the tunnel decreasing vertically upwards a remarkable transient temperature inversion during radon bursts suggests that the additional advective air contributions responsible for the radon bursts occur from the non saturated rocks below the tunnel

core disking and its relationship with stress magnitude for lac du bonnet granite abstract core disking is an indicator of elevated stress magnitudes disked cores from boreholes drilled from underground excavations in massive unfractured granite where the stress magnitudes are known with confidence were used to establish a relationship between core disk thickness and the stress magnitude relationships were established for three disk thickness categories 1 thin t d 0 2 2 medium 0 2 t d 0 4 and 3 thick 0 4 t d 2 2 and partial disking the data suggests that core disking initiates when the maximum principal stress normalized to the tensile strength is 6 5

structural heritage reactivation and distribution of fault and fracture network in a rifting context case study of the western shoulder of the upper rhine graben abstract in fractured reservoirs in the basement of extensional basins fault and fracture parameters like density spacing and length distribution are key properties for modelling and prediction of reservoir properties and fluids flow as only large faults are detectable using basin scale geophysical investigations these fine scale parameters need to be inferred from faults and fractures in analogous rocks at the outcrop in this study we use the western shoulder of the upper rhine graben as an outcropping analogue of several deep borehole projects in the basement of the graben geological regional data dtm digital terrain model mapping and outcrop studies with scanlines are used to determine the spatial arrangement of the faults from the regional to the reservoir scale the data shows that 1 the fault network can be hierarchized in three different orders of scale and structural blocks with a characteristic structuration this is consistent with other basement rocks studies in other rifting system allowing the extrapolation of the important parameters for modelling 2 in the structural blocks the fracture network linked to the faults is linked to the interplay between rock facies variation linked to the rock emplacement and the rifting event

diffuse faulting in the machu picchu granitoid pluton eastern cordillera peru abstract a series of batholiths forming part of the roots of a permo liassic rift system are exposed in the high eastern cordillera of central peru as a result of tectonic inversion shortening of the machu picchu granitoid pluton was accommodated by widespread shear reactivation of primary joints by a process termed here diffuse faulting fault like reactivation of precursor joint surfaces marked by chlorite epidote and quartz shear fibres is locally evidenced by few centimetres offsets within apparently undeformed granite analysis of fault slip data indicates that shear reactivation of different joint sets was kinematically consistent with ene oriented shortening less frequent mylonitic shear zones appear to have evolved from the common brittle precursors apart from rare phyllonitic shear zones fluid rock interaction along the brittle precursors was generally limited and pluton deformation appears to be mainly controlled by the geometry and distribution of primary joints three main sets of reactivated joints can be recognized characterized by oblique slip kinematics with variable reverse and strike slip components of motion theoretical modelling based on quantitative fracture analysis scan line data and different displacement length relationships applied to the main reactivated joint sets yield first order estimates of pluton finite strain the results suggest that bulk finite strain is oblate and essentially coaxial and is characterized by horizontal shortening not exceeding 10 relatively small finite strains integrated over the size of the pluton still result in a few kilometres of crustal shortening

fluid inclusion composition of baltic shield quartz associated with mineralization sweden abstract fluid inclusions in quartz from seven ore districts in sweden have been analyzed by the decrepitation icp method the geological setting of the deposits varies from a sedimentary sandstone environment to highly metamorphosed rocks in the amphibolite facies major components na k and ca give variable but interpretable information about fluids involved in ore disposition and subsequent metamorphism the k na and ca na ratios are very consistent even at low salt concentrations in the fluids and may be used to distinguish the origin of the involved mineralizing brine solutions feldspar contamination does not effect the ratios decrepitation icp data in the present study are consistent with the microthermometry and geochemistry of the deposits the base metals cu fe and zn give significant results agreeing with the mineralogy of the deposit

porosity of natural fracture networks volumetric imaging is used to determine the three dimensional topology of natural fracture networks in coal subjected to reservoir conditions computerized x ray tomographic data and bulk porosity measurements are combined with image processing techniques to quantify the porosity distribution of three dimensional fracture networks in two coal cores under in situ conditions the porosity of the fracture networks in the cores is less than one tenth of a percent in addition the porosity varies by 10 over depth intervals of approximately 16 mm 11 refs 4 figs 3 tabs

fractal analysis of fracturing in two african regions from satellite imagery to ground scale abstract in two test areas of africa the fractal character of fracture fields was analyzed at very different scales on fracture maps from satellite images and from interpretation of drainage networks on topographical maps aerial photographs and ground photographs three different methods were used and the results criticized it was generally found that the area studied in western africa displays more fractal features than the area examined in central africa this might be related to the number and mechanism of fracturing phases in each region

strain and scaling of faults in the chalk at flamborough head u k analysis has been made of the orientations displacements and spacings of 1340 extensional faults with displacements of up to 6 m along an almost completely exposed 6 km length of cliff this data set has been used to study how fault populations account for strain in a region and to study relationships between different scales of fault strains have been estimated the maximum and intermediate extensions are sub horizontal with approximately equal extension e 0 01 in all horizontal directions it can be inferred that the minimum extension maximum compression was sub vertical but that the wide variety of fault orientations and cross cutting relationships resulted from variable horizontal extensions some faults have oblique slip slickenside lineations which imply a period of later dominantly nnw sse extension which possibly developed as the exposure scale faults linked up e w striking larger scale normal faults effectively forming a single wide fault zone graphs of displacement per unit distance are used to illustrate variations in displacement the scaling of fault displacement appears to follow a power law relationship the differences in orientation between the small scale and large scale faults precludes a simple estimation of the total strain over all scales

stereological analysis of fracture network structure in geological formations relationships between three dimensional fracture networks consisting of poly disperse disks and the corresponding two dimensional trace maps are systematically analyzed bulk densities of disks and disk intersections are related to surface densities of traces and trace intersections this results in a new relation for the average length of disk intersections the probability densities of trace lengths and disk intersections are studied for several disk diameter distributions the inverse problem of deriving the disk distribution from the trace distribution is then solved assuming only that the disks have uniformly random locations and orientations these results are applied to a variety of synthetically generated data as well as to several sets of field data analysis of the field data suggests that fracture diameter distributions follow a power law in agreement with previous conclusions based on trace length histograms with exponents varying from 1 3 to 2 1

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

fracture distribution along an upper jurassic carbonate ramp ne spain abstract understanding the distribution of natural fractures in sedimentary systems is of high relevance for the exploration and production of fluids in the subsurface this study focuses on a kimmeridgian mixed siliciclastic carbonate ramp system which is part of the jurassic limestones outcropping in the northeastern iberian chain the study area is located north of the ricla village fifty kilometers southwest of zaragoza the outcrop stretches over six kilometers in length it allows for recording detailed fracture patterns and facies variations a gis based software package digifract is used to measure and digitize fractures in vertical outcrops fracture orientation measurements obtained from vertical and horizontal outcrops are used to create a conceptual three dimensional image of the fracture distribution of the mixed ramp system the fracture data are processed by integrating outcrop logs and sample data obtained from thin sections and rock property analysis the continuous facies belts of the shallow low angle ramp system show limited lateral variations the studied sediments are subdivided in four main facies tracts ft s ft 1 bioclastic siltstones ft 2 alternating sandy limestones and marls ft 3 cross bedded and channelled oolitic bioclastic sand and grainstones and ft 4 coralgal float to mudstones with eventites measured fracture orientations of the vertical and horizontal outcrops are identical throughout the entire exposure two main fracture sets are identified the first set set 1 has a n s direction and the second set set 2 has a ne sw direction the lateral homogeneity of the sedimentary system thus facies layer thickness and slope angle can be translated to the observed fracture patterns within one single facies belt fractures tend to behave the same in the proximal middle and distal part of the ramp system however vertical facies variations are an important factor for the measured vertical fracture heterogeneity fine grained mud supported facies correspond to periods of a sea level highstand coarse grained cemented facies on the other hand are related to a sea level lowstand the physical contrast of the sediments caused by sea level fluctuations forces fractures to solely concentrate in the brittle layers fracture density and termination patterns observed on this ramp stand in contrast to fracture geometries observed in flat topped carbonate platforms lateral facies heterogeneity and platform anatomy of flat topped carbonate platforms are key parameters for the eventual fracture distribution for the studied mixed ramp type system the vertical facies variations are key parameter

terrane amalgamation in the clew bay region west of ireland the caledonides of the west of ireland provide a well exposed and well mapped example of an oblique collision zone the east northeast trending deer park and achill beg fault system is a crustal scale ductile sinistral strike slip duplex of late ordovician age imbricating late precambrian granulite facies lower crustal rocks near eclogite facies supracrustal rocks up to amphibolite facies dalradian metasedimentary rocks and greenschist facies cambro ordovician rocks this fault system is correlated with a pre devonian component of the highland boundary fault system in southern scotland in the clew bay area the high pressure low temperature facies metamorphic rocks in tectonic contact with greenschist facies cambro ordovician rocks are together interpreted as an accretionary prism complex related to northwestward directed subduction both of these are allocthonous terrains with respect to the dalradian terrane to the north north west mayo to the south the cambro ordovician rocks docked with a probable dalradian block containing ultramafic intrusives deer park complex during the late ordovician the deer park complex and south mayo trough linked earlier during the arenig silurian and lower middle devonian redbed successions sit unconformably on the metamorphic rocks deposition and deformation of these cover rocks was controlled by oblique strike slip movements on the leek fault whose strike swings from west northwest to north northeast following earlier basement trends as it is traced eastwards from clew bay the leek fault system may be correlated with the leannan fault of northwest donegal a splay of the great glen fault system of central scotland east of clew bay this sinistral shear generated local dilation on the more northerly trending bend of the leek fault lower and middle old red sandstone redbeds were developed here the west northwest trend of the leek fault in clew bay acted as a compressional bend during these sinistral movements and transpressional southwest directed thrusting developed in silurian rocks post middle old red sandstone pre late tournaisian dextral displacement on the leek fault reversed this pattern with transtension in clew bay allowing intrusion of small carbonated peridotite bodies into silurian rocks and easterly directed thrusting of middle old red sandstone rocks east of the bay on the transpressional north south bend a tectonic model for the region is presented here this model involves a northwestward directed subduction system 150 to 750 km of arenig sinistral strike slip movement and eastwards insertion of the connemara block with formation of the ordovician south mayo trough as a pull apart basin subsequently a further 130 to 650 km eastward displacement of rocks took place south of the deer park fault in later ordovician times the magnitudes of these estimates are directly proportional to an assumed maximum wavelength of 1500 km for promontories on the original laurentian margin and using the current juxtaposition of terranes a minimum wavelength of 300 km is inferred

thickness and spatial distribution of veins in a porphyry copper deposit rosia poieni romania abstract a statistical analysis of the vein thickness distributions of veins in the rosia poieni porphyry copper deposit romania indicates that vein thickness data conform to a power law distribution whereas the spatial distribution of veins follows a negative exponential law a high clustering of the veins is indicated by both the spacing distribution and the cv values the similar vein densities observed at the open pit scale are representative of a saturation level of vein nucleation differences in the spacing distribution and in the mean vein thickness are explained by different initial nucleation rates in the deepest and the lowest parts of the porphyry copper the highly clustered organization of the system is explained by vein linkage processes during their growth and modification of the fluid pressure and local stress during the hydrofracturing

barometric pumping of a fractured porous medium barometric pumping plays a crucial role in the release of trace gases from fractured porous media to the atmosphere and it requires a rigorous and complete modeling in order to go beyond the approximate schemes available in the literature therefore a coupled set of convection and convection diffusion equations for a slightly compressible fluid in unsteady conditions should be solved the numerical methodology is presented and it is applied to conditions close to the ones of the roselend natural laboratory france the precision of the code is assessed and the mechanism of barometric pumping is explained the usual schematization by simple vertical fractures is shown to be only qualitative finally barometric pumping is shown to be efficient in a narrow range of parameter values its efficiency is a decreasing function of the matrix porosity and of the fracture density

use of curved scanlines and boreholes to predict fracture frequencies abstract we advance the method of hudson and priest journal of rock mechanics and mining sciences geomechanics abstracts 20 1983 73 89 to develop a method for a curved scanline to be used to predict the numbers of fractures that would be observed in any direction when sampling along a scanline the probability of intersecting a fracture is influenced by the relative orientations of the fracture and of the scanline at that location this sampling bias can be minimised by the use of the terzaghi correction w cos 1 where is the angle between the scanline and the normal to the fracture these corrected frequencies are used to simulate fracture frequencies for all other orientations by doubly correcting the data modelled fracture frequency is contoured on a graph of simulated scanline plunge against simulated scanline azimuth this method is based upon the assumption that the data collected along the scanline is representative of the fracture population when the terzaghi correction has been applied a graph of cumulative frequency of fractures against distance along a scanline provides a simple method for determining whether the scanline crosses differently fractured areas frequencies are corrected for dip strike and both dip and strike with data from homogeneously fractured areas plotting as straight lines these frequencies can be normalised for ease of comparison

crack seal fibre growth mechanisms and their significance in the development of oriented layer silicate microstructures abstract an analysis of crack seal fibre growth mechanisms has shown two important implications of the crack seal process for the interpretation of microstructures in low grade metamorphic rocks 1 1 the ability of fibre growth to track the incremental separation history of crack walls depends on details of the nucleation and growth mechanisms 2 2 fibrous crystals may develop cristallographic preferred orientations in certain crack seal situations the microstructures of layer silicates and associated phases developed in several examples of syntectonic intragranular microfracture sites and veins indicates that layer silicate 001 and grain shape preferred orientation can develop during crack seal deformation by oriented growth mechanisms during successive crack seal increments preferred orientation may develop in response to an interaction between anisotropic growth kinetics and the displacement history resulting in preferential rejoining by syntaxial overgrowth of pulled apart grains having fast growth directions parallel to the incremental displacement direction across a microcrack preferred orientation may also be developed and enhanced in crack seal growth sites by overgrowth of previously oriented layer silicates in the microcrack walls in this case the crystallographic preferred orientation need not be simply related to the displacement history during crack seal fibre growth since crack seal processes may operate on all scales down to the minimum size of a microfracture in a deforming rock such mechanisms of layer silicate preferred orientation development are expected to be very significant in developing and enhancing foliation during deformation involving microfracture and solution transfer processes

investigation of the effects of fractured porous media on hydraulic tests an experimental study at laboratory scale using single well methods abstract in this paper a study of detailed pneumatic tests at laboratory scale is presented the study comprises two different test methods which were conducted on an unsaturated fractured sandstone block of about 1 m 3 volume first a steady state flow field with constant gas injection pressure and consequently constant gas flow rates was applied to the fractured sandstone block via a vertical borehole the discharge of the injected gas was measured at the block surface second a constant gas pressure was injected over the borehole and the transient pressure buildup was recorded at the block surface it was the objective of the study to investigate the effects of the fractured porous system on pneumatic measurements and to provide an insight into processes occurring during flow and pressure buildup in fractured porous media this is an essential prerequisite for a reliable validation of different modeling approaches and it can further assist to improve techniques for the determination of the heterogeneity of hydraulic parameters in fractured porous media the analysis of the distribution of the flow field and the temporal and spatial evolution of pressure buildup during the hydraulic tests shows that the direction and contribution of the flow field is highly depending on the spatial distribution and the characteristics of the fracture network as well as on the position of the observation points with respect to highly conductive structures finally the introduced test methods are suitable tools for the characterization of the heterogeneous nature of fractured porous media and for the interpretation of the effects of the heterogeneous system on hydraulic tests

a large scale flow and tracer experiment in granite 1 experimental design and flow distribution this paper describes the stripa three dimensional experiment where water and tracer flow has been monitored in a specially excavated drift in the stripa mine several new experimental techniques and equipment were developed and used the experiment was performed in a specially excavated drift 100 m long at the 360 m level in granite the whole ceiling and the upper part of the walls were covered with 375 individual plastic sheets where the water flow into the drift could be collected eleven different tracers were injected at distances between 11 and 50 m from the ceiling of the drift the flow rate and tracer monitoring was kept up for more than 2 years the tracer breakthrough curves and flow rate distributions were used to study the flow paths velocities hydraulic conductivities dispersivities and channeling effects in the rock this paper describes the experimental techniques the fracture mapping the tracer and flow rate measurements and the results of the flow rate measurements the detailed observations made possible by the plastic sheeting technique have given some qualitative as well as quantitative information on flow rate distribution in fractured rock which previously has not been available these observations may be of importance for assessing the transport of dissolved species such as radionuclides through fractured rock

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

characterization and impact on reservoir quality of fractures in the cretaceous qamchuqa formation zagros folded belt abstract reservoir quality in tight fractured carbonate rocks is controlled by the fracture properties the tectonic origin of fractures the relationship of fractures to other sedimentary features within the rockmass and diagenesis in this study fracture analysis porosity and permeability of the qamchuqa formation in the miran west block of the zagros folded belt in kurdistan has been studied this was undertaken using core analysis micro resistivity image logs drill stem tests dst mud logging data repeat formation test rft drilled cutting samples and wireline log data the integrated analysis shows that the qamchuqa formation is characterized by heterogeneous sedimentary and tectonic features the sedimentary features include burial stylolites dissolution seams and some fractures which formed at early stages of burial and diagenesis phase 1 open fractures partially open mineralized fractures veins and tectonic stylolites were formed by later tectonic activity phase 2 the finding of this study highlight that the fracture properties including aperture length frequency and origin play an important role in controlling the reservoir s quality the open fractures and partially open mineralized fractures enhance permeability providing an inter connected fracture network leading to a high fracture permeability that controls fluid flow in this tight carbonate reservoir rock the fracture network had little impact on the volume of hydrocarbon storage which is controlled by the pore matrix in contrast structures including stylolites dissolution seams and veins generally have a negative impact on the reservoir quality by blocking the fluid flow this work emphasizes the importance of understanding the regional geological history and the role of sedimentary and tectonic features when investigating in tight carbonate reservoirs