contribution of peat compaction to relative sea level rise within holocene deltas 1 modern and forecasted flooding of deltas is accelerated by subsidence of holocene deposits subsidence caused by tectonics isostasy sediment compaction and anthropogenic processes combined with eustatic sea level rise results in drowning and increased flood risk within densely populated deltas many deltaic sedimentary successions include substantial amounts of peat which is highly compressible compared to clay silt and sand peat compaction therefore may contribute considerably to total delta subsidence existing studies are inadequate for quantifying peat compaction across deltas we present a numerical peat compaction model calibrated with an extensive field dataset the model quantifies spatial and temporal trends in peat compaction within fluvial dominated holocene flood basin sequences of different compositions subsidence due to peat compaction is highly variable in time and space with local rates of up to 15 mm yr depending on sedimentary sequence this is extremely important information for developing sound delta management strategies artificial groundwater table lowering may cause substantial additional subsidence subsidence due to peat compaction might even exceed estimates of relative sea level rise and thus may seriously increase the risk of delta drowning and human vulnerability to flooding

fractured reservoirs with fracture corridors outcrop studies reveal a common occurrence of tabular zones of significantly increased fracture intensity affecting otherwise well lithified rocks these zones called fracture corridors can have a profound effect on multi phase fluid flow in the subsurface using standard geo modelling tools it is possible to generate 3d realizations of reservoirs that contain distributions of such fracture corridors that are consistent with observations including the vertical frequency in pseudo wells inserted into the model at random locations these models can generate the inputs to flow simulation the approach adopted here is to run the flow simulations in a single porosity representation where the flow effects of fractures are upscaled into equivalent cell based properties preserving a clear spatial relationship between the input geology and the resulting cellular model the simulated reservoir performance outcomes are very similar to those seen in real oilfields extreme variability between wells early water breakthrough disappointing recoveries and patchy saturation distributions thus a model based on fracture corridors can provide an explanation for the observed flow performance of a suitable field however the use of seismics to identify fracture corridors is not an easy task new work is needed to predict the seismic responses of fracture corridor systems to be able to judge whether it is likely that we can robustly detect and characterize these flow significant features adequately

practical approaches to identifying sealed and open fractures for one essential ingredient of permeable fracture networks degree of fracture pore space preservation in large fractures i show how the characterization challenge presented by sparse fracture sampling can be overcome by measuring a surrogate the abundance of rock mass cement that precipitated after fractures ceased opening sampling limitations are overcome because the surrogate is readily measured in small rock samples including sidewall cores and cuttings permitting site specific diagnosis of the capacity of fractures to transmit fluid over a wider range of sample depths than conventional methods allow a diverse core database shows that this surrogate correctly predicts where large fractures are sealed information on timing of fracture opening relative to cement sequence can be obtained in two ways first evidence of fracture movement history and cement sequences in sparse large fractures can be extrapolated to areas having only cement data alternately evidence of fracture timing can be acquired from sealed micrometer scale fractures distribution of porosity reducing cement is commonly heterogeneous from bed to bed and location to location in siliciclastic and carbonate rocks however because patterns of sealed or open fractures cannot be delineated using fracture observations alone surrogates have practical value for production fairway mapping and other applications in which identifying open fractures is essential this study highlights the vital interplay among structural and diagenetic processes for fracture porosity preservation or destruction

pervasive dolomitization with subsequent hydrothermal alteration in the clarke lake gas field middle devonian slave point formation british columbia canada the clarke lake gas field in british columbia canada is hosted in pervasively dolomitized middle devonian carbonates of the slave point formation the clarke lake field consists mostly of pervasive matrix dolomite and some saddle dolomite the latter varying in volume from about zero in limestones to normally 20 40 locally up to 80 in dolostones over any given 10 m 33 ft core interval some of the saddle dolomite is replacive some is cement and both varieties are associated with dissolution porosity and recrystallized matrix dolomite the major objective of this study is to identify the causes and timing of matrix and saddle dolomite formation specifically whether these dolomites are hydrothermal a comprehensive petrographic and geochemical examination indicates that pervasive matrix dolomitization was accomplished by long distance migration of halite saturated brines during the late devonian to mississippian fluid inclusion homogenization temperatures suggest about 150 uncorrected to 190c corrected at the time of matrix dolomitization these temperatures differ markedly from most published work on the dolomitized devonian reefs in the alberta basin south of the peace river arch where pervasive matrix dolomitization was accomplished by advection of slightly modified seawater at temperatures of about 60 80c and where no hydrothermal influence was ever present the saddle dolomites at clarke lake are not cogenetic with matrix dolomite and are not the product of hydrothermal dolomitization sensu stricto instead they formed through the hydrothermal alteration of matrix dolomite by way of invasion of a gypsum saturated brine during periods of extremely high heat flow and regional plate margin tectonics in the late devonian to mississippian fluid inclusion homogenization temperatures suggest that hydrothermal alteration occurred between 230 uncorrected and 267c corrected which is significantly higher than the maximum temperature of about 190c attained by the slave point formation during burial the sources of the halite and gypsum saturated brines are middle devonian evaporite depositional environments roughly 200 km 124 mi south and or east of clarke lake near the peace river arch

aapg spe seg hedberg research conference on the geologic occurrence and hydraulic significance of fractures in reservoirs peter hennings received his b s and m s degrees in geology from texas a m university and his ph d in geology from the university of texas he has held various technical and supervisory positions in mobil research company phillips petroleum company and conocophillips his research and application focus in these positions includes structure and tectonics seismic interpretation reservoir description geomechanics and fracture characterization he is the manager of the structure and geomechanics group in conocophillips subsurface technology he is an aapg distinguished lecturer a geological society of america honorary fellow and an adjunct professor at the university of wyoming in july 2008 a hedberg research conference entitled the geologic occurrence and hydraulic significance of fractures in reservoirs was hosted jointly by the aapg society of petroleum engineers spe and society of exploration geophysicists seg and organized by aapg in casper wyoming the original endorsement for the conference was by recommendation from the author and the aapg reservoir deformation research group a standing subcommittee of the aapg research committee the scientific justification for conducting the conference was the rapidly growing recognition by the industry and academia that natural fractures and their geomechanical framework commonly control the hydraulic behavior of reservoirs the sciences of fracture detection characterization and hydraulic modeling must advance if we are to maximize recovery from fractured reservoirs and optimize our exploitation of emerging resources especially in the nonconventional realm success in these areas requires interdisciplinary integration from geophysical acquisition processing and analysis to petrophysics geological interpretation geomechanics and reservoir engineering at scales from pores to fields the last research conference in north america dedicated to the topic was conducted in 1997 therefore the agenda was designed to address fractured reservoirs at a fundamental level to assess progress in the last decade the participants addressed the following questions

a study on the optimal conditions for formation of complex fracture networks in fractured reservoirs abstract hydraulic fracturing is a key technology for unconventional oil reservoirs exploitation and the formation of effective complex fracture networks is an important index to evaluate the effect of hydraulic fracturing pre existing natural fractures will seriously affect the stress distribution in the reservoirs and hydraulic fractures propagation pathways therefore it is very useful to investigate the interactions between hydraulic and natural fractures in this study the mathematical model of stress distribution at fractures intersection and the cohesive zone method czm finite element simulation model are established the effects of different fracture intersecting angles natural fractures dip angles and horizontal stress difference hsd are compared and analyzed from numerical models finite element models and previous scholars laboratory tests the results show that fracture networks are most likely to be formed if the intersecting angle and natural fracture dip angle are between 30 and 60 it can be deduced that the larger the hsd the longer the hydraulic fracture the research provides a reference for the formation of complex fracture networks in fractured reservoirs

comparative study of the pleistocene cakmak quarry denizli basin turkey and modern mammoth hot springs deposits yellowstone national park usa this study compares and contrasts the travertine depositional facies of two of the largest sites of travertine formation located in very different geological contexts i e the modern mammoth hot spring mhs system in the active volcanic complex of yellowstone national park usa and the pleistocene cakmak quarry a well exposed example of the ballik travertines in the extensional denizli basin turkey new 2d to 3d facies maps of both travertine systems combined with microscopy assist in proposing an integrated spring depositional model based on the existing mhs facies model understanding general controls on meter to kilometer scale travertine deposit architecture and its preservation and provide quantitative estimates of facies spatial coverage and slope using gis the comparison resulted in the distinction of eight facies grouped in five downstream facies zones from vent to distal slope notwithstanding the different geological context of both travertine systems observations show that several of the facies are strikingly comparable draping apron and channel facies top slope pond facies crystalline proximal slope facies and distal slope facies whereas other facies do not have a precise exposed equivalent vent facies pavement apron and channel facies extended pond facies and phyto proximal slope facies combining observations of active springs at mhs with the cakmak vertical travertine quarry exposures demonstrates that lateral and vertical facies transitions are a sensitive record of changes in the spring dynamics flow intensity and paths that become well preserved in the geological record and can be recognized as prograding aggrading retrograding trends or erosive surfaces traceable over tens to hundreds of meters quantification of facies specific coverage at mhs shows that proximal and distal slope facies deposits cover as much as 90 of the total mapped surface area in addition only 7 of the surface is found to be marked by a waterfilm related to an active flowing spring slope statistics reveal that strong slope breaks can often be related to transgressive apron and channel facies belts and that variable but steep slopes up to 40 are dominated by proximal slope facies in agreement with the cakmak exposures integrating travertine facies and architecture of deposits formed in distinct geological contexts can improve the prediction of general spring facies distributions and controls in other modern and ancient subsurface travertine systems

a scale independent approach to fracture intensity and average spacing measurement fracture intensity the number of fractures per unit length along a sample line is an important attribute of fracture systems that can be problematic to establish in the subsurface lack of adequate constraints on fracture intensity may limit the economic exploitation of fractured reservoirs because intensity describes the abundance of fractures potentially available for fluid flow and the probability of encountering fractures in a borehole traditional methods of fracture intensity measurement are inadequate because they ignore the wide spectrum of fracture sizes found in many fracture systems and the consequent scale dependence of fracture intensity an alternative approach makes use of fracture size distributions which allow more meaningful comparisons between different locations and allow microfractures in subsurface samples to be used for fracture intensity measurement comparisons are more meaningful because sampling artifacts can be recognized and avoided and because common thresholds of fracture size can be enforced for counting in different locations additionally quantification of the fracture size distribution provides a mechanism for evaluation of uncertainties estimates of fracture intensity using this approach for two carbonate beds in the sierra madre oriental mexico illustrate how size cognizant measurements cast new light on widely accepted interpretation of geologic controls of fracture intensity

36cl in chloride rich rainwater israel eleven rainwater samples from israel have been analyzed for their isotopic36cl cl ratios and their soluble salt content the rains display a range of36cl cl ratios between1 8 10 15 and50 10 15 and chloride ion concentrations of between 0 3 and 4 2 meqcl l the ratios between the concentrations of na mg2 and cl in the samples demonstrate a clear marine origin for these ions in the rainwater although the stable35cl isotope in rainwater is marine in origin while the accompanying36cl radioisotope is non marine both are linearly and positively correlated in chloride rich 1meqcl l rains the36clcl seawater solute relationship may be explained as result of a mixing process between two chloride bearing sources a sea spray laden air with a low36cl cl ratio and b a cl rich mineral dust reservoir with a high36cl cl ratio both are introduced and admixed into the atmosphere during storms the possibility of a high36cl cl ratio stratospheric end member is rejected in view of the non marine nature of the chlorine therein

a comparison of groundwater dating with 81kr 36cl and 4he in four wells of the great artesian basin australia the isotopic ratios 81 kr kr and 36 cl cl and the 4 he concentrations measured in groundwater from four artesian wells in the western part of the great artesian basin gab in australia are discussed based on radioactive decay along a water flow path the 81 kr kr ratios are directly converted to groundwater residence times results are in a range of 225 400 kyr with error bars in the order of 15 primarily due to counting statistics in the cyclotron accelerator mass spectrometer measurement additional uncertainties from subsurface production and or exchange with stagnant porewaters in the confining shales appear to be of the same order of magnitude these 81 kr ages are then used to calibrate the 36 cl and the 4 he dating methods based on elemental analyses of rock samples from the sandstone aquifer as well as from the confining bulldog shale the in situ flux of thermal neutrons and the corresponding 3 he 4 he and 36 cl cl ratios are calculated from a comparison of i the 3 he 4 he ratios measured in the groundwater samples with the calculated in situ ratios in rocks and ii the measured n 37 cl ratios with the 4 he concentrations measured in groundwater it is concluded that both helium and chloride are most likely added to the aquifer from sources in the stagnant porewaters of the confining shale by diffusion and or mixing based on this working hypothesis the 36 cl transport equation in groundwater is solved taking into account i radioactive decay ii subsurface production in the sandstone aquifer with an in situ 36 cl cl ratio of 6u10 315 and iii addition of chloride from a source in the confining shale with a 36 cl cl ratio of 13u10 315 lacking better information it is assumed that the chloride concentration increased linearly with time from an unknown initial value ci to its

from fracture analysis to flow simulations in fractured carbonates the case study of the roman valley quarry majella mountain italy abstract this work assesses the impact of the stratigraphic and structural heterogeneities on the fluid distribution and migration within a deformed carbonate reservoir analogue the study was carried out in the abandoned roman valley quarry majella mountain central italy well known for its historical bitumen extraction the studied rocks consist of ramp carbonates of the lower member of the bolognano formation oligocene miocene in age mainly composed of grainstones and secondary packstones and wackestones in the quarry the exposed rocks are crosscut by two high angle oblique slip faults striking wnw ese with up to 40 m of throw with the aim of deciphering the contribution of both matrix and fracture pore space on the fluid storage and migration both laboratory measurements and field based discrete fracture network dfn models cubes with 4 m per side have been carried out the obtained dual porosity permeability model which includes the lithological and the structural heterogeneities observed at the location was used to run flow simulations under different scenarios of well locations the fluid distribution in the matrix resulting from these flow simulations is consistent with field observations where bitumen localizes within the most permeable lithofacies grainstones in the fault zones the fracture network causes an important fluid flow anisotropy enhancing the flow in a direction subparallel to the faults the flow orthogonal to the fault zones is controlled by type and lateral continuity of fault rocks where fault breccias represent conduits and cataclasites localized barriers

a new workflow for carbonate reservoir modelling based on mps shoal bodies in outcrop analogues triassic sw germany this study presents a workflow for 3d modelling of carbonate reservoirs using multiple point statistics mps in the framework of a pre existing model it consists of the follow ing steps 1 applying a hierarchical classification scheme for carbonate geobodies 2 based on this classification retrieval of relevant data from carbdb a novel software to manage a database of analogue studies 3 construction of training images based on the retrieved data from carbdb and 4 using the training images when building a 3d reservoir model with mps mps makes use of training images to capture depositional patterns which will then be reproduced during the stochas tic simulations carbdb provides a library of quantitative data such as dimensions geometries and the distribution pattern of geobody analogues necessary for building training images the mps workflow was applied to carbonate shoal bodies from a reservoir analogue the muschelkalk in swgermany present dayshoalbodiesfromthearabiangulfwereretrievedfromcarbdbasposs iblemodernanaloguestogeneratetrainingimages therealizations ofthismpsapproachare com pared with a previously established 3d geocellular model that was built deterministically by interactive facies modelling the mps simulationsproduced geologically more realistic facies dis tributions with higher facies heterogeneity similar to the depositional patterns observed in modern analogues

structural framework of the edwards aquifer recharge zone in south central texas the edwards aquifer the major source of water for many communities in central texas is threatened by population growth and development over its recharge zone the location of the recharge and confined zones and the flow paths of the aquifer are controlled by the structure of and deformation processes within the balcones fault system a major system of predominantly down to the southeast normal faults we investigate the geologic structure of the edwards aquifer to assess the large scale aquifer architecture analyze fault offset and stratigraphic juxtaposition relationships evaluate fault zone deformation and dissolution and fault system architecture and investigate fault block deformation and scaling of small scale intrablock normal faults characterization of fault displacement shows a pattern of aquifer thinning that is likely to influence fault block communication and flow paths flow path constriction may be exacerbated by increased fault segment connectivity associated with large fault displacements also increased fault zone deformation associated with larger displacement faults is likely to further influence hydrologic properties overall faulting is expected to produce strong permeability anisotropy such that maximum permeability is subhorizontal and parallel to fault bedding intersections at all scales aquifer permeability is either unchanged or enhanced parallel to faults and in many cases decreased perpendicular to faults

fracture characteristics in cretaceous platform and overlying ramp carbonates an outcrop study from maiella mountain central italy abstract this article focuses on field and laboratory based characterization of vertically persistent fractures that are part of oblique slip normal fault zones and crosscut the cretaceous platform and overlaying ramp carbonates outcropping at maiella mountain central italy the achieved results show that i fault damage zones are wider and more densely fractured in the platform carbonates than in the ramp ones ii joints and sheared joints composing the fault damage zones are taller better connected and less spaced within the former rocks than in the ramp carbonates the aforementioned structural differences are interpreted to be a consequence of the different mechanical properties of the platform and ramp carbonates during failure at maiella mountain platform carbonates are indeed made up of overall stiffer higher uniaxial compressive strength values and less porous rocks due to more abundant intergranular void filling cement and presence of matrix in terms of hydrocarbon flow and recovery geometric and dimensional attributes of fractures suggest that the well connected network of closely spaced fractures cutting across the platform carbonates may form efficient pathways for both vertical and horizontal hydrocarbon flow in contrast the relatively poorly connected and low density fracture network affecting the ramp carbonates is likely less efficient in providing fairways for flowing hydrocarbons

advances in carbonate exploration and reservoir analysis carbonate reservoirs contain an increasingly important percentage of the world s hydrocarbon reserves this volume presents key recent advances in carbonate exploration and reservoir analysis as well as a comprehensive overview of the trends in carbonate over the years the volume focuses on four key areas 1 emerging plays and techniques with special reference to lacustrine plays in syn rift basins and development of super giant heavy oil plays 2 improved reservoir characterization with examples from the middle east and europe and case studies of how outcrop analogues can provide key data for input to geological models 3 impact of fractures and faults in carbonates contributors highlight the need for integrated structural and diagenetic approaches in order to understand how fractures evolve as fluid flow conduits 4 advances in geomodelling of carbonate reservoirs several papers discuss the application of new and innovative geomodelling and geostatistical techniques to carbonate reservoirs

present day stress control on fluid migration pathways case study of the zechstein fractured carbonates nw germany abstract understanding the orientation and connectivity of fracture systems in tight reservoirs is essential to reduce uncertainties in reservoir development and production however the actual flow potential of the fractures can be controlled by the present day stress field dilation and slip tendency analyses can improve fracture permeability evaluations and thus aid in estimating the hydrocarbon recovery of a field this study focuses on a naturally fractured relatively tight matrix permeabilities of 0 01 1 md and gas producing late permian zechstein reservoir in the southern permian basin northern germany fracture data are obtained from resistivity image log data of a 775 m long horizontal well and show principal ne sw orientation with main dip angles steeper than 70 to quantify the potential of those fractures that contribute to the flow within the reservoir dilation td and slip ts tendencies are calculated two different stress scenarios are defined based on known variations in the orientation of the horizontal stresses between formations below and above the zechstein salt in an offset field approximately 5 km away results of td and ts strongly depend on the strike and dip angle of the fractures with sub vertical fractures showing highest potential to dilate while fractures with dip angles of 60 are favorably oriented for slip fractures with orientations parallel to the principal horizontal stress have highest slip and dilation tendencies adding this information to the calculation of fracture permeability results in a significant reduction of the calculated flow potential due to the influence of the stress field thus incorporating stress field data helps reducing risks in field development planning

interplay between fracturing and hydrothermal fluid flow in the ason valley hydrothermal dolomites basque cantabrian basin spain in ason valley hydrothermal dolomite area basque cantabrian basin northern spain an overlapping stepover area between two major basement faults the cabuerniga and ruahermosa transtensional faults was the location for different scales and types of extensive frac tures this fracture mesh affected the albian ranero limestone and was formed in a dilational jog a regional fluid throughflow area it acted as pathway for overpressured fluids that controlled the dolomite mineralization in the ranero massif area the study of synchronous structural features fluid flow channelling and dolomitization processes indicated their tectonic control the fluid cir culated and concentrated preferentially in more fractured areas with increased permeability such as extensional chimneys creating dolomite bodies repeated extensive tectonic activity enhanced fracture porosity promoting overpressured fluid migration and cyclical dolomitization events the studied fracture pattern suggests the presence of sinistral transtension during the formation of extensional joint sets that channellized the mineralizing fluid flow a gradation in structural fea tures and dolomite facies and textures is visible from the main pozalagua fault dolomite body to peripheral dolomite bodies as the breccia body and ranero megajoints these differences could reflect a proximal distal trend from the main fluid flow area along the pozalagua fault to the ranero megajoints

carbonate rocks and petroleum reservoirs a geological perspective from the industry abstract carbonate oil reservoirs are sometimes regarded with apprehension in the petroleum industry since it can be difficult to predict the quality of and ensure high recovery factors from this rock family particular problems are the complex and heterogeneous nature of porosity in carbonate rocks often leading to large ranges in permeability for any given porosity and the organization of carbonate successions most commonly as vertically heterogeneous but laterally persistent layers important issues that arise time and again in carbonate reservoir description include a predicting reservoir quality at inter well scales and in uncored wells b recognizing problematic high permeability layers c determining the permeability component to allocate to fractures and connected vug systems and d populating reservoir models with representative physical parameters because porosity in carbonate rocks generally presents as diverse and heterogeneous conventional core plugs are seldom representative of large rock volumes and significant issues remain in terms of the scale compatibility of the various datasets for measured physical parameters that are used in carbonate reservoir description many of the world9s largest carbonate reservoirs were discovered and developed shortly after the second world war and are now showing signs of maturity expressed variously as poor pressure support water or gas breakthrough and stranded resources the proportion of the world9s conventional petroleum that is reservoired in carbonate rocks is commonly estimated at around 50 60 and many large carbonate reservoirs are likely to have a production lifetime beyond 50 years it is no coincidence then that the petroleum industry has been the primary source of funding of and promotion of research into carbonate rocks and depositional systems often with impacts extending well beyond oil and gas exploitation

characterization of reservoirs fluids and productions from the ordovician carbonate condensate field in the tarim basin northwestern china the tz no1 gas field in the tarim basin is the largest condensate field in china however it has not developed efficiently because of low and unpredictable production during the past 20 yr cores logging interpretation seismic descriptions fluid properties and production data indicate that this ordovician carbonate field is different from conventional stratigraphic oil and gas fields as follows 1 the hydrocarbon bearing area covers a large region of 2000 km2 2 matrix reservoirs have low porosity 20 per year an examination of the carbonate reservoir and hydrocarbon accumulation history suggests that this large scale stratigraphic accumulation formed during hydrocarbon emplacement in the early paleozoic with the reservoirs gradually evolving into tight reservoirs as a result of intense diagenesis variable amounts of neogene gas charged the tight carbonate reservoirs and formed unconventional accumulations the tz no1 gas field is characterized by a strongly heterogeneous tight matrix reservoir with a superimposed fracture cave reservoir and a complicated unconventional fluid distribution which provides insights into the exploitation challenges of unconventional carbonate resources

sedimentology of coexisting travertine and tufa deposits in a mounded geothermal spring carbonate system obruktepe turkey the recent discoveries of deeply buried cretaceous reservoir bodies in the atlantic ocean revealed that relationships between the distribution of spring carbonate deposits and faults are poorly understood the well exposed quaternary deposits at obruktepe denizli basin turkey provide an opportunity to reconstruct the three dimensional sedimentary architecture of such a system integration of sedimentological lithofacies and geochemical analyses reveals complexity in the lateral relationships between sedimentary environments faults and geothermal spring carbonates five environmental systems are distinguished based on the lithofacies analysis i vent ii smooth slope iii travertine terrace iv tufa barrage and v flood systems encrusting baffling and settling sedimentary processes are reflected in data acquired at several scales from lithofacies observations to the morphology and arrangement of geobodies together with microfabrics and stable carbon and oxygen isotope data mean values of 4 9 parts per thousand delta c 13 and 8 74 parts per thousand delta o 18 vienna peedee belemnite reflect geothermal circulation of springwaters the environmental distribution and lithofacies indicate a lateral continuum between travertine and tufa deposits within this hot spring system this finding supports two depositional models in which water flow variation is the main control on both caco3 precipitation and the resulting formation of travertine and tufa the proposed models address the factors responsible for the development of these complex mound shaped carbonate spring deposits and how they are related to fluid circulation at depth and in association with faults

fracture networks and strike slip deformation along reactivated normal faults in quaternary travertine deposits denizli basin western turkey abstract the denizli basin in the west anatolian extensional province in western turkey is known for its numerous quaternary travertine occurrences travertine morphology is often dependant on the relative position of the deposition with respect to basin bounding faults the travertine occurrences examined in this study are situated at the intersection of the locally e w oriented denizli basin and the adjacent ne sw oriented baklan graben in the ne based on an extensive field campaign including lidar scanning several high resolution fault fracture maps of five large quarries 300 m in length and 60 m in height are constructed in which this world class travertine deposit is currently excavated a structural analysis is performed in order to determine the tectonic overprinting of the travertine body and to derive the stress states of the basin after travertine deposition the mostly open non stratabound joints are several tens of metres long and often bifurcate creating a dense fracture network minor infill of the joints resulted in the presence of a few colour banded calcite veins based on the e w ne sw and nw se orientation of three dominant joint sets it is concluded that the joint network is caused by local n s extension alternated by nw se and ne sw extension exemplifying the presence of stress permutations in the quaternary high angle e w to wnw ese faults cross cut the quarries faults are filled with travertine debris and clastic infill of above lying sedimentary units indicative of the open nature of the faults the specific e w fault orientation in the locally e w trending denizli basin indicates that they initiated as normal faults a paleostress inversion analysis performed on kinematic indicators such as striations on the clayey fault infill and the sinistral displacement of paleosols shows that some of the normal faults were reactivated causing left lateral deformation in a transient strike slip stress field with a ne sw oriented 1

evidence for chlorine recycling hydrosphere biosphere atmosphere in a forested wet zone on the canadian shield abstract the ability to measure environmental levels of 36 cl by accelerator mass spectrometry and 3 h by 3 he ingrowth mass spectrometry has made it possible to use the pulses of these two isotopes released into the atmosphere during nuclear weapons testing as tracers of cl and water movement in soils and groundwater the authors have investigated the movement of these tracers below a forested wet zone and have found that both are retarded to a differing extent in the near surface because of vegetative uptake and recycling adsorption by clay particles followed by slow release to the groundwater may also be significant the data accumulated in this region of near vertical recharge have gone a considerable distance towards explaining the anomalously low concentrations of 36 cl measured in the 5 laurentian great lakes as well as indicating possible mechanisms for large scale cl recycling in the atmosphere and biosphere identification of the near term non conservative behaviour of the cl is significant since such a phenomenon could introduce errors in many watershed calculations e g water residence times evaporation rates and mixing calculations

the distribution of meteoric cl 36 in precipitation across europe in spring 2007 abstract the cosmogenic isotope 36 cl is a valuable tool for understanding many earth system processes but an improved knowledge of its spatial distribution at the earth s surface is critical for several applications meteoric 36 cl fallout reflects complex interactions between atmospheric production transport and deposition processes and predictive models require experimental validation this study investigates for the first time in a systematic way the spatial distribution of meteoric 36 cl on a continental scale within the european landmass using precipitation samples collected during spring 2007 36 cl cl ratios increase with distance inland and the new data exhibit a strong exponential relationship with 18 o values of precipitation r s 0 75 yielding a useful predictive framework for future studies precipitation events in central european regions are characterised by high 36 cl cl ratios with a maximum measured in lyon france of 746 134 10 15 the new data confirm models for the dependence of 36 cl fallout on latitude with the highest mean springtime fallout 53 6 atoms m 2 s 1 occurring in the 40 50 n latitudinal band with sharp decreases in fallout in high latitude regions and more gradual decreases towards the lower latitudes the 36 cl bomb pulse introduced by thermonuclear weapon testing predominantly in the 1950 s has persisted in the environment for c 50 years but the new data indicate that 36 cl fallout has now essentially returned to natural pre bomb values

structurally controlled hydrothermal dolomite reservoir facies an overview structurally controlled hydrothermal dolomite htd reservoir facies and associated productive leached limestones are major hydrocarbon producers in north america and are receiving increased exploration attention globally they include multiple trends in the ordovician locally silurian and devonian of the michigan appalachian and other basins of eastern canada and the united states and in the devonian and mississippian of the western canada sedimentary basin they also occur in jurassic hosts along rifted atlantic margins in the jurassic cretaceous of the arabian gulf region and elsewhere hydrothermal dolomitization is defined as dolomitization occurring under burial conditions commonly at shallow depths by fluids typically very saline with temperature and pressure t and p higher than the ambient t and p of the host formation the latter commonly is limestone proof of a hydrothermal origin for htd reservoir facies requires integration of burial thermal history plots fluid inclusion temperature data and constraints on timing of emplacement hydrothermal dolomite reservoir facies are part of a spectrum of hydrothermal mineral deposits that include sedimentary exhalative lead zinc ore bodies and htd hosted mississippi valley type sulfide deposits all three hydrothermal deposits show a strong structural control by extensional and or strike slip wrench faults with fluid flow typically focused at transtensional and dilational structural sites and in the hanging wall transtensional sags above negative flower structures on wrench faults are favored drilling sites for htd reservoir facies saddle dolomite in both replacive and void filling modes is characteristic of htd facies for many reservoirs matrix replacive dolomite and saddle dolomite appear to have formed near contemporaneously and from the same fluid and temperature conditions the original host facies exerts a major influence on the lateral extent of dolomitization resultant textures pore type and pore volume breccias zebra fabrics shear microfractures and other rock characteristics record short term shear stress and pore fluid pressure transients particularly proximal to active faults high temperature hydrothermal pulses may alter kerogen in host limestones a process designated forced maturation basement highs underlying sandstone and or carbonate aquifers probably overpressured and overlying and internal shale seals and aquitards also may constrain or influence htd emplacement although many questions and uncertainties remain particularly in terms of mg and brine source and mass balance recognition and active exploration of the htd play continues to expand increasing use of three dimensional seismic imagery and seismic anomaly mapping combined with horizontal drilling oblique to linear trends defined by structural sags helps to reduce risk

solar activity during the last 1000 yr inferred from radionuclide records identification of the causes of past climate change requires detailed knowledge of one of the most important natural factors solar forcing prior to the period of direct solar observations radionuclide abundances in natural archives provide the best known proxies for changes in solar activity here we present two independent reconstructions of changes in solar activity during the last 1000 yr which are inferred from be 10 and c 14 records we analyse the tree ring c 14 data shcal intca104 from 1000 to 1510 ad and annual data from 1511 to 1950 ad and four be 10 records from greenland ice cores camp century grip milcent and dye3 together with two be 10 records from antarctic ice cores dome concordia and south pole in general the be 10 and c 14 records exhibit good agreement that allows us to obtain reliable estimates of past solar magnetic modulation of the radionuclide production rates differences between be 10 records from antarctica and greenland indicate that climatic changes have influenced the deposition of be 10 during some periods of the last 1000 yr the radionuclide based reconstructions of past changes in solar activity do not always agree with the sunspot record which indicates that the coupling between those proxies is not as close as has been sometimes assumed the tree ring c 14 record and be 10 from antarctica indicate that recent solar activity is high but not exceptional with respect to the last 1000 yr c 2006 elsevier ltd all rights reserved less

an algorithm for 3d simulation of branchwork karst networks using horton parameters and application to a synthetic case this paper presents a method to stochastically simulate 3d karstic networks and more specifically branchwork pattern cave systems considering that they can be compared with 3d fluvial networks the topological classification of strahler and the corresponding ratios of horton are used to define three morphometric parameters these parameters are integrated in an algorithm that computes branches hierarchically to obtain a final network organized around the main observed inlet and outlet with a branching complexity controlled by the user each branch corresponds to a low cost path between two points calculated with the a graph search algorithm speleogenetic information on inception horizons palaeo water tables and fractures is accounted for by adapted definitions of the searching functions of a the method is demonstrated on a 3d synthetic case with discrete fractures networks inception horizons and a palaeo water table the simulated karsts have a realistic geometry and are geologically consistent simulation

36cl in modern groundwater dated by a multi tracer approach 3h 3he sf6 cfc 12 and 85kr a case study in quaternary sand aquifers in the odense pilot river basin denmark abstract 36 cl produced by thermonuclear bomb testing has been proposed as an additional tool to date or at least to identify recent groundwater components in order to investigate the behaviour of 36 cl in shallow groundwater a multi tracer approach 3 h 3 he sf 6 cfc 12 and 85 kr was used to characterise and date the groundwater of a quaternary sands aquifer which is located on the island of funen near the city of odense denmark recharge to the semi confined shallow aquifer occurs through permeable sand windows and fractured tills at the surface locally however mixing with older pre bomb water from the underlying limestone aquifer may occur the integrated analyses of the available tracer data allowed a well constrained age structure determination of the investigated water system the 36 cl cl ratios measured in groundwater were used to reconstruct the fallout rates for radioactive 36 cl at odense the calculated fallout values exceeded the fallout estimated based on data from the dye 3 ice core in greenland recycling of the bomb peak fallout seems to be the most probable reason of the high values measured the local extent of this process is difficult to quantify which impedes the use of 36 cl for dating

dating rupture events on alluvial fault scarps using cosmogenic nuclides and scarp morphology scarp morphology evolution has commonly been used to estimate the timing of fault scarp rupture events however rates of scarp degradation depend strongly on the geomorphic diffusivity a parameter that is difficult to constrain independently this difficulty may lead to large uncertainties in the estimated ages of rupture events in this study we have coupled the accumulation of the cosmogenic nuclide 36cl to a model for scarp morphology in order to constrain the value of the geomorphic diffusivity and thus determine a more accurate rupture chronology than a rupture history based solely on scarp morphology we measured depth profiles of 36cl accumulated in situ within alluvial sediments beneath the surface of the socorro canyon fault scarp in central new mexico the material analyzed consisted of 150 individual gravel clasts from each depth interval amalgamated into a single sample the alluvium was sampled in three vertical profiles 4 m deep the first profile was 1 5 m downslope of the fault plane on the hanging wall the second 1 5 m upslope of the fault plane on the footwall and the third 27 m upslope of the fault plane on the footwall the third profile which served as a control and which soil geomorphic evidence indicated was beneath a stable surface showed a simple exponential 36cl profile from which a depositional age of 122 18 ka was calculated the second profile on the footwall showed a 36cl deficit relative to the control profile indicating net erosion the first profile on the hanging wall showed a 36cl excess relative to the control profile indicating net deposition stratigraphic evidence in the hanging wall indicated two rupture events prior to the late holocene we modeled the accumulation of 36cl in the vicinity of the scarp simulating erosional redistribution using a diffusion equation for scarp morphology the model accounted for redistribution of 36cl along with the sediment and the effects of the changing fault scarp morphology on the 36cl production by matching both the observed hanging wall and footwall 36cl profiles to profiles calculated by the model as well as the observed topographic profile we obtained ages of 92 16 13 and 28 18 23 ka for the two ruptures the results of our study indicate that cosmogenic nuclides can be useful in constraining rupture chronologies of fault scarps in alluvium

hydrothermal dolomite a product of poor definition and imagination abstract the latest dolomite bandwagon is the hydrothermal dolomite model in its present form this bandwagon is doomed or at least very much overstated for at least two reasons 1 there are several definitions of hydrothermal and hardly any author specifies which one s he is using 2 very few of the dolomites hitherto called hydrothermal have been demonstrated to be hydrothermal according to any definition except the worst as presently applied the term hydrothermal dolomite is confusing and or meaningless we suggest to use white s geol soc amer bull 68 1957 1637 time honored definition of hydrothermal as aqueous solutions that are warm or hot relative to its surrounding environment with no genetic implications regarding the fluid source hence a dolomite should be called hydrothermal only if it can be demonstrated to have formed at a higher than ambient temperature regardless of fluid source or drive furthermore this definition does not carry a lower or upper temperature limit even a dolomite formed at 40 c could be hydrothermal by extension dolomites formed at temperatures lower than ambient are not hydrothermal even if they formed at a rather high temperature for example groundwater may penetrate a rock sequence through a highly permeable pathway such that it is heated to 150 c at a depth where the surrounding rock has a temperature of 250 c we suggest to call dolomite formed from this water hydrofrigid dolomite formed in or near thermal equilibrium with the surrounding rocks may be called geothermal furthermore not all saddle dolomite formation requires advection fluid flow to transport mg saddle dolomite can be formed in at least three ways i e from advection local redistribution of older dolomite during stylolitization and as a by product of thermochemical sulfate reduction in a closed or semi closed system only the first and the last of these three possibilities have a chance of being hydrothermal almost all dolomites and dolostones in the western canada sedimentary basin have recently been re interpreted as hydrothermal applying the rationale outlined above reveals however that this basin contains very little hydrothermal dolomite rather most dolomites in this basin and almost all dolostones south of the peace river arch are geothermal and or the proof of a hydrothermal origin has not been made this has important implications beyond the various case studies at hand as attempts to tie dolomitization to orogenic events become moot at least in the southern part of the basin

three dimensional facies modeling of carbonate sand bodies outcrop analog study in an epicontinental basin triassic southwest germany this article is the first part of an integrated study to characterize the anatomy and geometries of carbonate shoal reservoir bodies in epicontinental settings it is based on outcrop analog data from triassic layer cake carbonates in the south german basin which were deposited along an epicontinental very gently inclined carbonate ramp the database of this study consists of 56 measured sections supplemented by six shallow cores and wireline logs covering an area of 25 by 36 km 15 by 22 mi the potential reservoir bodies consist generally of midramp shoal and shoal fringe facies types which are composed of skeletal and oolitic carbonate packstones and grainstones with significant amounts of porosity the upper muschelkalk is composed of a lower transgressive and an upper regressive interval within these shoal bodies show not only similarities but also major differences in character geometry and distribution these reflect the conditions of an epeiric system which reacts strongly to small changes in accommodation the accommodation seems to be mainly triggered by the interaction of hierarchically organized large medium and small scale relative sea level changes and a subtle paleorelief at the level of medium scale cycles distinct two dimensional cyclicity styles can be differentiated which record the lateral facies distribution along the depositional gradient different styles of medium scale cycles include different types of shoal bodies 1 transgressive crinoidal shoal style shoal bodies mean width 21 km 13 mi mean length 37 km 23 mi mean thickness 4 2 m 13 7 ft with low facies differentiation deposited on top of subtle paleohighs 2 skeletal sheets style thin reservoir sheets mean width 5 1 km 3 1 mi mean length 11 1 km 6 8 mi mean thickness 0 3 m 0 9 ft of reservoir facies on top of the paleohighs 3 regressive oolitic shoal style shoal bodies mean width 14 6 km 9 0 mi mean length 20 8 km 12 9 mi mean thickness 0 69 m 2 2 ft with high facies differentiation on the flanks of paleohighs and 4 low accommodation style patchy and mosaic distribution of shoal bodies mean width 11 2 km 6 9 mi mean length 26 km 16 mi mean thickness 0 69 m 2 2 ft all data were loaded into three dimensional 3 d modeling software to distribute 14 facies types and model the 3 d stratigraphic architecture the resulting facies distribution implies that volume and dimensions of the shoal bodies are mainly controlled by the combination of stratigraphic cycles and a subtle paleorelief which is indicated by overall thickness changes of succession high energy shoal facies types occur only in and around areas with a reduced overall thickness whereas areas with a thicker development are dominated by low energy muddy facies types all observations combined point to the presence of a subtle paleorelief which could be induced by slight differential subsidence of inherited paleotectonic basement blocks on the kilometer to regional scale previous studies suggest simple layer cake stratal patterns however in the full 3 d view the apparent layer cake stratigraphy turned out to be a pseudolayer cake with very gentle 0 01 0 001 dip clinoform geometries these very subtle offlapping pinch out geometries may have been overlooked in epeiric reservoir systems elsewhere

cosmogenic 36cl in karst waters quantifying contributions from atmospheric and bedrock sources improved reconstructions of cosmogenic isotope production through time are crucial to understand past solar variability as a preliminary step to derive atmospheric 36 cl cl solar proxy time series from speleothems we quantify 36 cl sources in cave dripwaters atmospheric 36 cl fallout rates are a potential proxy for solar output however extraneous 36 cl derived from in situ production in cave hostrocks could complicate the solar signal results from numerical modeling and preliminary geochemical data presented here show that the atmospheric 36 cl source dominates in many but not all cave dripwaters at favorable low elevation mid latitude sites 36 cl based speleothem solar irradiance reconstructions could extend back to 500 ka with a possible centennial scale temporal resolution this would represent a marginal improvement in resolution compared with existing polar ice core records with the added advantages of a wider geographic range independent u series constrained chronology and the potential for contemporaneous climate signals within the same speleothem material

loading paths to joint propagation during a tectonic cycle an example from the appalachian plateau u s a abstract based on the timing of joint propagation during the history of burial lithification deformation and denudation of clastic rocks within sedimentary basins four types of joints may be distinguished tectonic hydraulic unloading and release tectonic and hydraulic joints form at depth prior to uplift in response to abnormal fluid pressures whereas unloading and release joints form near the surface in response to thermal elastic contraction accompanying erosion and uplift tectonic joints are distinguished from hydraulic joints in that tectonic compaction is a mechanism for achieving abnormal pore pressures leading to the propagation of the former whereas compaction by overburden loading leads to the abnormal pore pressures in the latter case the orientation of unloading joints is controlled by either a residual or contemporary tectonic stress whereas the orientation of release joints is controlled by a rock fabric examples of some of these joints are found within the devonian catskill delta of the appalachian plateau new york during the alleghanian orogeny tectonic joints cross fold joints formed under abnormal pore pressure as indicated by the observation that joints propagated in the siltstones before they developed in shales and by the cross cutting relationships of folds cleavage and joints this sequence is compatible with oil company hydraulic fracture data which show that the least principal stress within sandstone layers is less than that in the intercalated shale layers plumose structures indicate that the joints within siltstones propagated as discontinuous rupture events each of which affected less than a meter of bed length the discontinuous rupturing is compatible with models for natural hydraulic fracturing release joints strike joints post date the alleghanian orogeny as indicated by abutting relationships within the deeper parts of the devonian clastic section unloading joints are orthogonal to the contemporary tectonic stress field

cosmogenic 36cl in karst waters from bunker cave north western germany a tool to derive local evapotranspiration abstract monthly rain and drip waters were collected over a period of 10 months at bunker cave germany the concentration of 36 cl and the 36 cl cl ratios were determined by accelerator mass spectrometry ams while stable 35 37 cl concentrations were measured with both ion chromatography ic and ams the measured 36 cl fluxes of 0 97 0 57 10 4 atoms cm 2 month 1 0 97 atoms m 2 month 1 in precipitation were on average twice as high as the global mean atmospheric production rate this observation is consistent with the local fallout pattern which is characterized by a maximum at mid latitudes the stable chloride concentration in drip waters ranging from 13 2 to 20 9 mg l and the 36 cl concentrations ranging from 16 9 10 6 to 35 3 10 6 atoms l are a factor of 7 and 10 above the values expected from empirical evapotranspiration formulas and the rain water concentrations respectively most likely the additional stable cl is due to human impact from a nearby urban conglomeration the large 36 cl enrichment is attributed to the local evapotranspiration effect which appears to be higher than the calculated values and to additional bomb derived 36 cl from nuclear weapons tests in the 1950s and 60s stored in the soil above the cave in the densely vegetated soil above bunker cave 36 cl seems not to behave as a completely conservative tracer the bomb derived 36 cl might be retained in the soil due to uptake by minerals and organic material and is still being released now based on our data the residence time of 36 cl in the soil is estimated to be about 75 85 years

best practice stochastic facies modeling from a channel fill turbidite sandstone analog the quarry outcrop eocene ainsa basin northeast spain using data from an outcrop characterization of a sandstone rich turbidite channel fill the so called quarry outcrop in the ainsa basin several stochastic facies models were constructed at bed scale resolution cells 2 5 m 8 ft wide and 0 05 m 2 in thick several industry standard reservoir modeling algorithms were employed truncated gaussian simulation sequential indicator simulation multiple point geostatistics and object based methods with varying degrees of complexity the degree of similarity i e realism between realizations and the outcrop characterization was quantified through the use of several responses 1 static connectivity 2 effective permeability and 3 recovery efficiency from waterflood simulations differences in the responses measured from the outcrop and facies models were observed these are mostly algorithm related instead of caused by soft data or different stochastic realizations differences increase greatly when the permeability of the heterolithic packages and mudstone beds ht m decreases and reflect the methods ability to model the inclined and undulating ht m packages and beds that occur in the outcrop these packages and beds can drape scours and sandstone beds with depositional topography and pinch outs producing sandstone thinning and dead ends object based methods capable of introducing highly undulating ht m beds provided the most realistic models variogram based and simple object based methods failed to capture and reproduce the whole length of undulating beds multiple point geostatistics provided realizations with responses intermediate between variogram based and simple object based methods and the more successful advanced object based methods the conditioning to hard data capabilities of multiple point geostatistics are higher than those of the object based methods which give them an added advantage

modeling fracture porosity evolution in dolostone abstract opening mode fractures in dolostones buried to depths of 1 5 km contain synkinematic dolomite cement the amount and internal structure of which has a systematic relationship to fracture size narrow fractures we developed a geometric crystal growth model for synkinematic dolomite fracture fill in fractured dolostones where periodic incremental fracture opening events are introduced with concurrent cement growth we assumed constant temperature and supersaturation with respect to dolomite a key assumption in the model is that rapid dolomite accumulation within bridges is governed by high cement growth rates on repeatedly broken grain surfaces during the process of crack seal slower cement growth rates occur on euhedral crystals this assumption is made on the basis of a comparison with quartz cement growth in fractured sandstones simulations with different fracture opening rates mimic bridge and lining cement morphologies including characteristic rhombic shapes of dolomite bridges

geological significance of seismic reflections and imaging of the reservoir architecture in the malampaya gas field philippines the integration of petrographic analyses of cores and thin sections petrophysical measurements and well logs demonstrates that variations in acoustic impedance in the malampaya buildup upper eocene to lower miocene offshore northwest palawan are related to vertical changes in porosity and pore type which are dominantly controlled by diagenetic processes the nido limestone was subdivided into 10 50 m 30 150 ft thick units characterized by specific diagenetic patterns and petrophysical properties diagenetic units the alternation between tight and porous diagenetic units is mainly controlled by meteoric diagenesis leaching and pedogenesis and by late burial cementation and leaching well to seismic ties show that the main seismic reflectors within the buildup interior reflect the boundaries between diagenetic units most of the negative amplitude reflectors are related to unconformities whereas positive amplitude reflectors have a more questionable chronostratigraphic value and may represent the bases of cemented lenses that can crosscut time lines comparison with other southeast asian tertiary buildups indicates different origins of seismic reflections related to distinct patterns of diagenetic evolution the identification of such seismodiagenetic units and of their controlling factors is of paramount importance for the architecture and the petrophysical characterization of carbonate reservoirs

cosmogenic nuclides during isotope stages 2 and 3 abstract changes in the concentration of cosmogenic nuclides measured in natural archives are related mainly to changes in the cosmic ray induced production rate in the atmosphere but also to the subsequent transport and deposition processes which depend on the geochemical properties of the nuclides a comparison of 10 be and 36 cl data from ice cores from greenland ice cores and 14 c data from tree rings and other archives provides the following information for the isotope stages 2 and 3 1 changes in the cosmogenic nuclide production rate on time scales longer than approximately 2 kyr agree well with paleomagnetic data derived from deep sea sediments in particular the geomagnetic excursions leading to weak fields around 40 kyr bp laschamp and 32 kyr bp mono lake can be clearly seen 2 production variations on shorter time scales contain information on solar variability as an example the 205 yr devries cycle already known from the analysis of 14 c tree ring data during the holocene is also present in the 10 be data of the time period 25 55 kyr bp 3 a comparison of 14 c calculated using 10 be data with the measured 14 c record points to a reduction of the global deep water formation during the younger dryas cold event 4 using information available on the production rates of cosmogenic nuclides in the past derived from paleomagnetic data the paleoprecipitation rate can be calculated this is crucial for establishing precise time scales

mechanical stratigraphy and palaeo karstification of the murge area apulia southern italy the cretaceous apulia platform exposed in the murge area southern italy suffered intense palaeo karstification this study focuses on the controlling factors of karstification with emphasis on fracturing mechanical stratigraphy was used to calculate the fracture density withindifferent sedimentarysequences several mechanical unitswere defined and a characteristic relationship was found between unit thicknesses and fracture density that is fracture density increases if layer thickness decreases in some of the quarries studied sedimentary cycles are clearly present that are also reflected in the fracture density logs the degree of karstification withina mechanical unit is proportional to the mean fracture spacing based on fracture orientation data extracted from lidar scans different orientation clusters were observed between fractures thatarekarstifiedandfracturesthatarenotkarstified post datingkarstification theclustersofkar stified fractures are related to the compression of the southern apennines the fractures became dissolution enlarged during the pleistocene uplift caused by bulging of the apulia platform this main karstification phase occurred prior to late pleistocene deposition and before the for mation of orthogonal fracture sets

the nature and origins of decametre scale porosity in ordovician carbonate rocks halahatang oilfield tarim basin china at 7 km depths in the tarim basin hydrocarbon reservoirs in ordovician rocks of the yijianfang formation contain large cavities c 10 m or more vugs fractures and porous fault rocks although some yijianfang formation outcrops contain shallow formed near surface palaeokarst features cores from the halahatang oilfield lack penetrative palaeokarst evidence outcrop palaeokarst cavities and opening mode fractures are mostly mineral filled but some show evidence of secondary dissolution and fault rocks are locally highly c 30 porous cores contain textural evidence of repeated formation of dissolution cavities and subsequent filling by cement calcite isotopic analyses indicate depths between c 220 and 2000 m correlation of core and image logs shows abundant cement filled vugs associated with decametre scale fractured zones with open cavities that host hydrocarbons a sm nd isochron age of 400 37 ma for fracture filling fluorite indicates that cavities in core formed and were partially cemented prior to the carboniferous predating permian oil emplacement repeated creation and filling of vugs timing constraints and the association of vugs with large cavities suggest dissolution related to fractures and faults in the current high strain rate regime corroborated by velocity gradient tensor analysis of global positioning system gps data rapid horizontal extension could promote connection of porous and or solution enlarged fault rock fractures and cavities supplementary material stable isotopic analyses and the velocity gradient tensor and principal direction and magnitude calculation are available at https doi org 10 6084 m9 figshare c 4946046 thematic collection this article is part of the the geology of fractured reservoirs collection available at https www lyellcollection org cc the geology of fractured reservoirs

origin and reservoir characteristics of upper ordovician trenton black river hydrothermal dolomite reservoirs in new york in the past decade more than 20 new natural gas fields have been discovered in laterally discontinuous dolomites of the upper ordovician black river group in south central new york the dolomites form around basement rooted wrench faults that are detectable on seismic data most fields occur in and around elongate fault bounded structural lows interpreted to be negative flower structures away from these faults the formation is composed of impermeable limestone and forms the lateral seal for the reservoirs in most cases the faults die out within the overlying trenton limestone and utica shale most porosity occurs in saddle dolomite coated vugs breccias and fractured zones matrix porosity is uncommon in the black river cores described for this study the patchy distribution around basement rooted faults and geochemical and fluid inclusion analyses supports a fault related hydrothermal origin for the saddle and matrix dolomites this play went for many years without detection because of its unconventional structural setting i e structural lows versus highs using the appropriate integrated structural stratigraphic diagenetic model more hydrothermal dolomite natural gas reservoirs are likely to be discovered in the black river of new york and in carbonates around the world

tectonic setting and stratigraphic architecture of an early cretaceous lacustrine carbonate platform sugar loaf high santos basin brazil abstract the sugar loaf high is an extensive basement structure within the santos basin offshore brazil in which all of the elements of the pre salt hydrocarbon play are present following a clastic dominated early synrift phase the later synrift and sag phases are characterized by an extensive non marine carbonate platform over the basement high the study area within this new 3d seismic dataset contains carbonates stratigraphically equivalent to the reservoirs within the lula and sapinhoa fields analysis of the 3d seismic data shows that the pre salt carbonates onlap the basement of the sugar loaf high and form aggradational geometries on a platform that has a proximal to distal width of about 100 km and an interpreted relief of some 900 m the carbonate platform has an aggradational and mounded basinward facing gullied margin with slope deposits progradational units are imaged on the platform top that may be either carbonate or clastic in composition the platform is preserved beneath evaporites that form the regional seal within the santos basin platforms of this size are previously unknown from lacustrine settings outside the pre salt stratigraphy of the santos and campos basins brazil

mechanical and fracture stratigraphy using examples from core studies this article shows that separate identification of mechanical stratigraphy and fracture stratigraphy leads to a clearer understanding of fracture patterns and more accurate prediction of fracture attributes away from the wellbore mechanical stratigraphy subdivides stratified rock into discrete mechanical units defined by properties such as tensile strength elastic stiffness brittleness and fracture mechanics properties fracture stratigraphy subdivides rock into fracture units according to extent intensity or some other observed fracture attribute mechanical stratigraphy is the by product of depositional composition and structure and chemical and mechanical changes superimposed on rock composition texture and interfaces after deposition fracture stratigraphy reflects a specific loading history and mechanical stratigraphy during failure because mechanical property changes reflect diagenesis and fractures evolve with loading history mechanical stratigraphy and fracture stratigraphy need not coincide in subsurface studies current mechanical stratigraphy is generally measurable but because of inherent limitations of sampling fracture stratigraphy is commonly incompletely known to accurately predict fractures in diagenetically and structurally complex settings we need to use evidence of loading and mechanical property history as well as current mechanical states

holocene sea level database for the atlantic coast of the united states we have constructed a database of holocene relative sea level rsl observations for the atlantic coast of the united states the database contains 492 index points which locate the position of rsl in time and space and 344 limiting dates which constrain the minimum or maximum limit of former sea level the majority of the index points in the database are from 6 ka bp to present with only 7 older than 6 ka bp spatially index points are distributed between maine and south carolina but there is an absence of data from georgia and the atlantic coast of florida the database is sub divided into 16 regions based on the distance from the former laurentide ice sheet and are classified depending upon their susceptibility to compaction the index points and limiting data demonstrate that rsl did not exceed present 0 m during the holocene except potentially in regions 1 and 2 eastern maine and southern maine rates of rsl change were highest during the early holocene and have decreased over time due to the diminishing response of the earth s mantle to glacial isostatic adjustment and reduction of ice equivalent meltwater input along the atlantic coast of the united states the linear rate of rsl rise prior to 4 ka bp ranged from 0 5 to 4 5 mm a 1 compared to 0 6 1 8 mm a 1 from 4 ka bp to ad 1900 the database suggests minimal 0 3 mm yr changes in these rates of rsl rise during the late holocene deglaciation of the laurentide ice sheet caused the spatial variability captured by the database the maximum rate of late holocene and ongoing rsl rise occurred in mid atlantic regions new jersey and inner delaware because of collapse of the peripheral forebulge

holocene relative sea level changes and glacial isostatic adjustment of the u s atlantic coast the first quality controlled holocene sea level database for the u s atlantic coast has been constructed from 686 sea level indicators the database documents a decreasing rate of relative sea level rsl rise through time with no evidence of sea level being above present in the middle to late holocene the highest rates of rsl rise are found in the mid atlantic region we employ the database to constrain an ensemble of glacial isostatic adjustment models using two ice ice 5g ice 6g global ice sheet reconstructions and two mantle viscosity models vm5a vm5b vm radial variation of viscosity in the sublithospheric mantle variations to assess whether the spherically symmetric viscoelastic models are able to survive intercomparison with a more refined database of postglacial rsl history we identify significant misfits between observations and predictions using ice 5g with the vm5a viscosity profile ice 6g provides some improvement for the northern atlantic region but misfits remain elsewhere decreasing the upper mantle and transition zone viscosity by a factor of 2 to 0 25 10 21 pa s vm5b removes significant discrepancies between observations and predictions along the mid atlantic coastline although misfits remain in the southern atlantic region these may be an indication of the importance of laterally heterogeneous viscosity in the upper mantle

evidence for temporally changing mechanical stratigraphy and effects on joint network architecture previous studies of jointing in sedimentary rocks have shown that joint network archi tecture is controlled by mechanical stratigraphy which is described by 1 the thickness and rigidity of stratigraphic units and 2 the nature of interfaces between beds using joint pattern to infer rigidity contrast between beds is complicated by the possibility that material properties of the beds may change between fracturing events observation of both an early bed contained joint set and a differently oriented late throughgoing joint set in the same beds of growth strata in the oliana anticline in the spanish pyrenees may reflect changing mechanical properties i e via diagenesis during the folding process using a schmidt hammer we assess the rigidity contrast between the individual units and show that the present day contrast is not great enough to terminate joints at interfaces this result is consistent with an interpretation that the late stage throughgoing joints formed in strata with conditions similar to those of the present day and that the early bed contained joints formed when the rigidity contrast between beds was significantly greater than that of the present day for example differential diagenesis rates between layers of differing grain size would produce temporally changing mechanical stratigraphy we propose that changes in mechanical stratigraphy may have previously been unrec ognized in other stratigraphic sections and that these changes affect joint network archi tecture and subsequent fluid flow pathways

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