critically stressed fractures analysis of the shaikan field kurdistan region of iraq the shaikan field is a large producing oil field in the kurdistan region of iraq it consists of multiple fractured reservoirs consisting of limestones calcareous sandstones and mudstones the surrounding tectonic terrane is situated in the seismically active zagros taurus orogenic zone where present day stresses are high the regional stresses are found to impose conditions that satisfy failure along reservoir bound fractures suggesting that a significant proportion of fractures are likely to be critically stressed the in situ maximum principal stress magnitudes are estimated using three methods namely the tensile and compressive strengths of reservoir rock and leak off test lot data stress field orientations are determined from wellbore image log data which are used to interpret wellbore breakouts and the associated induced tensile fractures reservoir pressure has declined since production started and poroelastic responses have been assessed and used to estimate the present day stress state and the criticality of those fractures that are most likely to fail or slip although a conventional approach has been used the present authors argue that a new approach to stress response with changing pore pressure should be taken unlike the previous theory of criticality in which a reduction in pore pressure is considered to lead to a stabilization of the fracture network the present study suggests that a system may remain critically stressed regardless of pressure decline 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

empirical relationships among seismic velocity effective pressure porosity and clay content in sandstone we use a multivariate analysis to investigate the influence of effective pressure pe porosity and clay content c on the compressional velocity vp and shear velocity vs of sandstones laboratory measurements on water saturated samples of 64 different sandstones provide a large data set that was analyzed statistically for each sample relationships between effective pressure and vp and vs have been determined all samples were well fit by relationships that have an exponential increase in velocity at low pe tapering to a linear increase with pe for pe greater than 0 2 kbar there are differences in the pressure dependences of velocity for different rocks particularly at very low pressures however the differences cannot be attributed to or c for the combined set of measurements from all samples the best fitting formulations are vp 5 77 6 94 1 73c 0 446 pe e 16 7pe and vs 3 70 4 94 1 57c 0 361 pe e 16 7pe while this is admittedly a very simplified parameterization it is remarkable how well

analytical and numerical solutions on the response of pore pressure to cyclic atmospheric loading with application to horonobe underground research laboratory japan during the long term stability assessment of underground disposal repositories buried in sedimentary formations one of crucial scientific problems is to determine parameters of site formations the analysis of response of the pore pressure due to atmospheric loading provides a possible way of accurate estimation of formation parameters in this paper an analytical solution of response of the pore pressure to atmospheric loading was derived starting from the biot s poroelasticity and its corresponding numerical solutions were developed by finite element methods for 1d and 2d situations with comparison to the analytical solution the experimental results show that the numerical schemes sound reasonable to implement the assessment of response of the pore pressure in horizontal multilayer sedimentary formations in particular it is effective for a 2d model over large area with consideration of background horizontal groundwater flow a highlight of this work is to construct a reasonable approach to capture responses of the pore pressure to atmospheric loading and at the same time to provide the feasibility of integrated analysis of well monitoring data of pore pressure variance in horonobe underground research laboratory url hokkaido japan

thermal mechanical and chemical influences on the performance of optical fibres for distributed temperature sensing in a hot geothermal well structural well bore integrity is an important issue for sustainable provision of geothermal energy raman scattering based fibre optic distributed temperature sensing dts can help to monitor the status of a well and therefore help to optimize expensive work over activities this study reports on the installation of a fibre optic cable in the cemented annulus behind the anchor casing in the high temperature geothermal well he 53 hellishei i geothermal field sw iceland although the cable has been damaged during the installation temperature data could be acquired during the entire length of installation down to 261 3 m temperature measurements were performed during the installation in spring 2009 during the onset of a flow test in summer 2009 and after a 8 5 month shut in period in summer 2010 during the flow test maximum temperatures of 230 c were measured after 2 weeks fluid production using optical time domain reflectometry otdr attenuation measurements at 850 and 1 300 nm enabled to identify mechanical thermal and chemical degradation along the optical fibre the observed degradation led to erroneous temperature readings and limits due to the optical budget of the dts system the accessible length of the fibre the characteristics and the influence of the different degradation mechanisms on the accuracy of the dts measurements are discussed and recommendations for an optimized installation are given

stress field constraints on intraplate seismicity in eastern north america focal mechanisms of 32 north american midplate earthquakes mo 3 8 6 5 were evaluated to determine if slip is compatible with a broad scale regional stress field derived from plate driving forces and if so under what conditions stress regime pore pressure and frictional coefficient using independent information on in situ stress orientations from well bore breakout and hydraulic fracturing data and assuming that the regional principal stresses are in approximately horizontal and vertical planes 10o the constraint that the slip vector represents the direction of maximum resolved shear stress on the fault plane was used to calculate relative stress magnitudes defined by the parameterb s2 s3 s s3 from the fault stress geometry as long as the focal mechanism has a component of oblique slip i e the b axis does not coincide with the intermediate principal stress direction this calculation identifies which of the two nodal planes is a geometrically possible slip plane gephart 1985 slip in a majority of the earthquakes 25 of 32 was found to be geometrically compatible with reactivation of favorably oriented preexisting fault planes in response to the broad scale uniform regional stress field slip in five events was clearly inconsistent with the regional stress field and appears to require a localized stress anomaly to explain the seismicity significantly all five of these events occurred prior to 1970 when many regional networks were installed and their focal mechanisms are inconsistent with more recent solutions of nearby smaller events the frictional likelihood of the geometrically possible slip on the selected fault planes was evaluated in the context of conventional frictional faulting theory the ratio of shear to normal stress on the fault planes at hypocentral depth was calculated relative to an assumed regional stress field regional stress magnitudes were determined from 1 s s3 ratios based on the frictional strength of optimally oriented faults the basis for the linear brittle portion of lithospheric strength profiles 2 the computed relative stress magnitude b values and 3 a vertical principal stress assumed equal to the lithostat two end member possibilities were examined to explain the observed slip in these less than optimally oriented fault planes first the frictional coefficient was held constant on all faults hydrostatic pore pressure was assumed regionally and the fault zone pore pressure was determined since pore pressure is a measurable quantity with real limits in the crust p0 s3 this end member case was used to determine which of the geometrically possible slip planes were frictionally likely slip planes alternately pore pressure was fixed at hydrostatic everywhere and the required relative lowered frictional coefficient of the fault zone was computed slip in 23 of the 25 geometrically compatible earthquakes was determined to also be frictionally likely in response to an approximately horizontal and vertical regional stress field derived from plate driving forces whose magnitudes are constrained by the frictional strength of optimally oriented faults assuming hydrostatic pore pressure regionally the conditions for slip on these 23 relatively well oriented earthquake faults were determined relative to this regional crustal strength model and require only moderate increases in pore pressure between about 0 4 0 8 of lithostatic hydrostatic is about 0 37 of lithostatic or alternately moderate lowering 50 of the frictional coefficient on the faults which slipped superlithostatic pore pressures are not required focal mechanisms for the two other earthquakes with slip vectors geometrically consistent with the regional stress field however did require pore pressures far exceeding the least principal stress or extremely low coefficients of friction these events may reflect either local stress rotations undetected with current sampling or poorly constrained focal mechanisms the analysis also confirmed a roughly north to south contrast in stress regime between the central eastern united states and southeastern canada previously inferred from a contrast in focal mecha nisms between the two areas most central eastern united states earthquakes occur in response to a strike slip stress regime whereas the southeastern canadian events require a thrust faulting stress regime this contrast in stress regime with a constant maximum horizontal stress orientation determined by far field plate driving forces requires a systematic lateral variation in relative stress magnitudes superposition of stresses due to simple flexural models of glacial rebound stresses are of the correct sense to explain the observed lateral variation but maximum computed rebound related stress magnitude changes are quite small about 10 mpa and do not appear large enough to account for the stress regime change if commonly assumed stress magnitudes determined from frictional strength apply to the crust at seismogenic depths

implications of the pore pressure and in situ stress for the coalbed methane exploration in the southern junggar basin china abstract the southern junggar basin hosts abundant coalbed methane cbm resources and is expected to be an important cbm production base in china the pore pressure and in situ stress are key factors that influence the exploration and development of cbm however these factors are poorly understood in this area based on extended leak off test data mathematical models were established for pore pressure and in situ stress prediction using regression analysis subsequently the correlations between the pore pressure in situ stress and permeability were analyzed and the stress ratios were investigated finally the forming mechanism of stress zonation in the study area was discussed the results show that cbm reservoirs are generally underpressured and partly overpressured at depths greater than 800 m in the study area the study area is characterized by notable stress zoning the stress regime varies from reverse to strike slip to normal faulting with increasing depth significantly positive correlations exist between the pore pressure maximum principal stress minimum principal stress vertical stress and principal stress difference the minimum horizontal stress is approximately 70 of the vertical stress in the study area a mud weight window varying from the pore pressure to the most likely breakdown pressure is suggested at depths greater than 600 m a relatively high principal stress difference is observed which indicates that deep coals have a relatively high mechanical strength and their permeability can be enhanced by hydraulic fracturing the depth dependent stress zonation is mainly due to the influence of thrusting on the in situ stress which diminishes with increasing depth the compressional stress regime in the shallow area benefits the sealing of faults and the preservation of cbm resources in the study area the deep cbm resources have a development potential the outcomes of this study contribute to the cbm exploration and development in the study area

montessus de ballore a pioneer of seismology the man and his work abstract ferdinand de montessus de ballore was one of the founders of scientific seismology he was a pioneer in seismology at the same level as perrey mallet milne and omori he became familiar with earthquakes and volcanoes in central america 1881 1885 after his experience in el salvador his interest for understanding earthquakes and volcanoes oriented all of his life back in france he worked out a most complete world catalogue of earthquakes with 170 000 events 1885 1907 and completed his career being the head of the chilean seismological service 1907 1923 many of his ideas were in advance of later discoveries he was an exceptional writer and published more than 30 books and hundreds of papers

source modeling of the hsingtai china earthquakes of march 1966 abstract the hsingtai china earthquakes of march 1966 were a series of destructive earthquakes associated with the shu lu graben five strong shocks of ms 6 occurred within a period of less than a month the largest of which was ms 7 2 body and surface waves over the period range from several to 100 s have been modeled for the four largest events using synthetic seismograms in the time domain and spectral analysis in the frequency domain data from ground deformation local geology regional seismic network and teleseismic joint epicenter determination have also been used to constrain the source model and the rupture process the fault mechanism of the hsingtai sequence was mainly strike slip with a small component of normal dip slip the strikes of the four largest shocks range from n26 to 30 e approximately along strike of the major faults of the shu lu graben and the aftershock distribution the source mechanisms can be explained with a nnw sse extensional stress and a nee sww compressional stress acting in the area the major shocks all had focal depths 10 km the four largest shocks in the sequence were characterized by a relatively simple and smooth dislocation time history the durations of the far field source time functions ranged from 3 5 to 5 s while the rise times were all 1 s the seismic moments of the four largest earthquakes ranged from 1 43 1025 to 1 51 1026 dyne cm 1 the fault sizes of the four events were very close assuming circular faults the diameters of the four events were determined to be between 10 and 14 km stress drops varied from 52 to 194 bars a trend of increasing stress drop with earthquake size was observed a survey of stress drop determinations for 15 major intraplate earthquakes shows that on the average the magnitude of stress drop of oceanic intraplate earthquakes and passive continental margin events is higher 200 to several hundred bars than that of continental intraplate earthquakes 100 bars or less

biot gassmann theory for velocities of gas hydrate bearing sediments elevated elastic velocities are a distinct physical property of gas hydrate bearing sediments a number of velocity models and equations e g pore filling model cementation model effective medium theories weighted equations and time average equations have been used to describe this effect in particular the weighted equation and effective medium theory predict reasonably well the elastic properties of unconsolidated gas hydrate bearing sediments a weakness of the weighted equation is its use of the empirical relationship of the time average equation as one element of the equation one drawback of the effective medium theory is its prediction of unreasonably higher shear wave velocity at high porosities so that the predicted velocity ratio does not agree well with the observed velocity ratio to overcome these weaknesses a method is proposed based on biot gassmann theories and assuming the formation velocity ratio shear to compressional velocity of an unconsolidated sediment is related to the

coastal quaternary morphologies on the northern coast of the south china sea china and their implications for current tectonic models a review and preliminary study marine terraces tidal notches and sediments along a 1200 km long stretch of the northern coast of the south china sea passive margin were studied and divided into five areas with varying tectonic characters up to three marine terraces occur that have elevations reaching up to 60 m above mean sea level amsl and two marine notches occur up to 11 m amsl chronology of the morphologies and deposits was obtained mainly by comparison with quaternary sea levels derived from the oxygen isotope curve however prior to the last interglacial highstand mis 5e c 125 ka evidence of history of events is less well constrained leading to less precision on sea level positions prior to mis 5e using the morphological features of mis 5e as a marker mean coastal uplift rates in the last c 125 ka range from 0 07 mm yr to 0 18 mm yr the pattern of deformations is slightly higher than those observed on passive margin coasts in other parts of the world the cause of uplift of the south china coastline is not clear but may relate to the himalayan collision zone or any other large scale phenomena

modification of heavy mineral assemblages in english coversands by acid pedochemical weathering summary weathering of non opaque heavy minerals in five english soil profiles developed in texturally homogeneous late devensian coversands has been investigated by spline interpolation of detailed mineral counts values for d90 90 mineral depletion derived from the splines suggest a depletion sequence that is generally applicable to moderately acid weathering of sediments apatite olivines amphiboles pyroxenes epidotes garnets more resistant minerals weathered minerals form three groups each of which is eliminated in an almost discrete stage weathering is accompanied by a characteristic developmental sequence of surface textures weathering rates of most of the silicate minerals are probably determined mainly by their fe2 contents effective surface areas and soil ph considerable variations in the depth and severity of weathering between profiles may reflect differences in vegetation histories heavy mineral weathering is related to soil chemistry to examine its implications for podzol genesis

wellbore reservoir coupled simulation to study thermal and fluid processes in a co2 based geothermal system identifying favorable and unfavorable conditions in comparison with water using co2 as a heat transmission fluid to extract geothermal energy is currently considered as a way to achieve co2 resource utilization and geological sequestration as a novel heat transmission fluid the thermophysical properties of co2 are quite different from those of water co2 has many advantages such as larger mobility and buoyancy resulted from the lower density and viscosity this will reduce the consumption of pressure driving the circulation and save the energy of external equipment the cycle even can be achieved by siphon phenomenon under a negative circulating pressure difference however there are still some disadvantages for co2 as the heat transmission fluid such as small heat capacity leading to a less heat at the same mass flow rate at the same time because of the lager expansion and compression coefficient for co2 changes in temperature and pressure may cause a more complex flow and thermodynamic processes the lager compressibility makes it possible to get high temperature at the bottom of the injection well whereas the lager expansion coefficient makes the temperature drop rapidly along the production well therefore how to scientifically control the production pressure to guarantee sufficient high temperatures at the head of production well and thereby improve the efficiency of heat extraction are the key issues needed to be further addressed the geological and geothermal conditions correspond to the central depression of the songliao basin located in the northest of china this depression has a high geothermal gradient and heat flow in this article a classic idealized five spot reservoir model coupled with wellbores is used for simulations and analyses the objectives of the present work are 1 to investigate the fluid flow and thermal processes of supercritical co2 along the wellbore and in the reservoir 2 to understand the heat extracting mechanism 3 to identify advantages and disadvantages of using co2 as the heat transmission fluid and 4 to provide a theoretical basis for the selection of heat transmission fluid

a compositional approach to the reconstruction of geochemical processes involved in the evolution of holocene marine flooded coastal karst basins mljet island croatia abstract geochemical patterns in the environment are always the result of certain processes therefore it is essential to decipher a process to properly evaluate the environmental role and potential of chemical elements compounds this allows the distinction between natural and anthropogenic influence on elemental concentrations however if the compositional nature of geochemical data is neglected erroneous or misleading conclusions regarding the processes involved are probable in this study the reconstruction of depositional environments and processes through the holocene in two sediment cores obtained from submerged sinkholes located on the island of mljet croatia was performed by taking into account the compositional nature of geochemical mineralogical and grainsize data problems involving compositional data are always multivariate for example the concentration of a single element does not carry any interpretative information as only the ratios between elements do this has led to the discovery of a large number of geochemical proxies based on elemental ratios which describe certain environmental conditions and processes involved nevertheless some proxies have been found to be restricted to only some specific environments thus preventing them from being used in general therefore some kind of relation between different proxies is necessary to obtain final conclusions however when using simple elemental ratios those correlations cannot be obtained due to the nature of compositional data with a sequential binary partition of a compositional vector orthonormal log ratio olr coordinates proxies can be constructed when based on expert knowledge those proxies fully acknowledge the geochemical properties of the chosen elements with one major difference that the correlation between newly obtained variables is mathematically well grounded as a result the final conclusion is more accurate in this research geochemical proxies obtained as a representation in olr coordinates of the elements that are enriched compared to the local soil were used to perform principal component analyses it helped to unravel the evolution of sedimentary environments mineralogical xrd and heavy mineral data and grain size analyses supported the conclusions obtained based solely on geochemical data furthermore data analysis suggests that the proxies for redox conditions described in the literature should be used with caution as their use is somewhat limited

impact of glacial activity on the weathering of hf isotopes observations from southwest greenland abstract data for the modern oceans and their authigenic precipitates suggest incongruent release of hafnium hf isotopes by chemical weathering of the continents the fact that weathering during recent glacial periods is associated with more congruent release of hf isotopes has led to the hypothesis that the incongruency may be controlled by retention of unradiogenic hf by zircons and that glacial grinding enhances release of hf from zircons here we study the relationship between glacial weathering processes and hf isotope compositions released to rivers fed by land terminating glaciers of the greenland ice sheet as well as neighbouring non glacial streams the weathered source rocks in the studied area mostly consist of gneisses but also include amphibolites of the same age 1 9 ga hafnium and neodymium isotope compositions in catchment sediments and in the riverine suspended load are consistent with a predominantly gneissic source containing variable trace amounts of zircon and different abundances of hornblende garnet and titanite glacially sourced rivers and non glacial streams fed by precipitation and lakes show very unradiogenic nd isotopic compositions in a narrow range nd 42 8 to 37 9 hafnium isotopes on the other hand are much more radiogenic and variable with hf between 18 3 and 0 9 in glacial rivers and even more radiogenic values of 15 8 to 46 3 in non glacial streams although relatively unradiogenic hf is released by glacial weathering glacial rivers actually fall close to the seawater array in hf nd isotope space and are not distinctly unradiogenic based on their abundance in rocks and sediments and their isotope compositions different minerals contribute to the radiogenic hf in solution with a decreasing relevance from garnet to titanite hornblende and apatite neodymium isotopes preclude a much stronger representation of titanite hornblende and apatite in solution such as might result from differences in dissolution rates than estimated from mineral abundance the strong contrast in hf isotope compositions between glacial rivers and non glacial streams results mostly from different contributions from garnet and zircon where zircon weathering is more efficient in the subglacial environment a key difference between glacial and non glacial waters is the water rock interaction time while glacial rivers receive continuous contributions from long residence time waters of distributed subglacial drainage systems non glacial streams are characterized by fast superficial drainage above the permafrost horizon therefore the increased congruency in hf isotope weathering in glacial systems could simply reflect the hydrological conditions at the base of the ice sheet and glaciers with zircon weathering contributions increasing with water rock interaction time

sensitivity of 3d thermal models to the choice of boundary conditions and thermal properties a case study for the area of brandenburg ne german basin based on newly available data of both the structural setting and thermal properties we compare 3d thermal models for the area of brandenburg located in the northeast german basin to assess the sensitivity of our model results the structural complexity of the basin fill is given by the configuration of the zechstein salt with salt diapirs and salt pillows this special configuration is very relevant for the thermal calculations because salt has a distinctly higher thermal conductivity than other sediments we calculate the temperature using a femethod to solve the steady state heat conduction equation in 3d based on this approach we evaluate the sensitivity of the steady state conductive thermal field with respect to different lithospheric configurations and to the assigned thermal properties we compare three different thermal models a a crustal scale model including a homogeneous crust b a new lithosphere scale model including a differentiated crust and c a crustal scale model with a stepwise variation of measured thermal properties the comparison with measured temperatures from different structural locations of the basin shows a good fit to the temperature predictions for the first two models whereas the third model is distinctly colder this indicates that effective thermal conductivities may be different from values determined by measurements on rock samples the results suggest that conduction is the main heat transport mechanism in the brandenburg area

thermophysical rock properties of the crystalline gonghe basin complex northeastern qinghai tibet plateau china basement rocks the basement of the gonghe basin complex gbc mainly consists of plutonic rocks which in general are suitable for geothermal applications knowledge of the rock properties of the deep basement formations is of fundamental importance for unconventional geothermal applications such as enhanced geothermal systems an outcrop analogue study at the margin of the gbc was conducted to improve the understanding of the petrophysical rock properties and enhance the data availability for numeric simulation and resource assessment approaches in total 148 samples were derived from 21 sampling locations at the margin of the gbc area and mountain ranges within lithologically the sample set was divided in three sample types 1 syenogranite 2 granite and biotite granite 3 granodiorite petrophysical properties such as grain density bulk density porosity intrinsic matrix permeability compressional and shear wave velocities as well as thermal properties like thermal conductivity and thermal diffusivity were analyzed on oven dry specimens under laboratory conditions ambient temperature atmospheric pressure unconfined compressive strength was additionally measured on selected samples the resulting dataset shows averaged bulk densities ranging between 2 59 and 2 73 g cm 3 and porosities from 0 2 to 1 7 matrix permeability is lower than 1 10 18 m2 averaged thermal conductivity ranges from 2 34 to 3 19 w m 1 k 1 compressional wave velocity from 3 6 to 6 2 km s 1 and unconfined compressive strength from 128 to 241 mpa petrophysical data are correlated with mineral content and grain size to show the influence of petrography on petrophysical properties although the petrophysical rock properties were analyzed at laboratory conditions and therefore deviate from in situ properties at reservoir conditions the presented dataset enhances the knowledge of petrophysical rock properties within the study area for further geothermal applications a first prediction of in situ reservoir conditions was performed on laboratory data based on empirically determined pressure and temperature dependencies of thermal conductivity thermal diffusivity specific heat capacity and compressional wave velocity

acoustic measurements in unconsolidated sands at low effective pressure and overpressure detection shallow water flows and over pressured zones are a major hazard in deepwater drilling projects their detection prior to drilling would save millions of dollars in lost drilling costs i have investigated the sensitivity of seismic methods for this purpose using p wave information alone can be ambiguous because a drop in p wave velocity vp can be caused both by overpressure and by presence of gas the ratio of p wave velocity to s wave velocity vp vs which increases with overpressure and decreases with gas saturation can help differentiate between the two cases since p wave velocity in a suspension is slightly below that of the suspending fluid and vs 0 vp vs and poisson s ratio must increase exponentially as a load bearing sediment approaches a state of suspension on the other hand presence of gas will also decrease vp but vs will remain unaffected and vp vs will decrease analyses of ultrasonic p and s wave velocities in sands show that the vp vs ratio especially at low effective pressures

seismic anisotropy in sedimentary rocks part 2 laboratory data part one of this paper presents a method for measuring seismic velocities and transverse isotropy in rocks using a single core plug this method saves at least two thirds of the time for preparing core samples and measuring velocities in transversely isotropic ti rocks using this method we have measured velocity and anisotropy of many shale and reservoir rocks from oil and gas fields around the world we present some of the data in this paper which include seismic velocity and anisotropy in 17 brine saturated shale samples 1 gas and brine saturated coal sample 8 brine saturated sands 12 gas saturated sands 32 gas saturated carbonate samples and 25 brine saturated carbonate samples the results show that clays and fine layering in sedimentary rocks are the main causes of seismic anisotropy very little intrinsic anisotropy exists in unfractured reservoir rocks such as sands sandstones and carbonates under reservoir conditions in contrast all shales were found seismically anisotropic anisotr

impact of single inclined faults on the fluid flow and heat transport results from 3 d finite element simulations the impact of inclined faults on the hydrothermal field is assessed by adding simplified structural settings to synthetic models this study is innovative in carrying out numerical simulations because it integrates the real 3 d nature of flow influenced by a fault in a porous medium thereby providing a useful tool for complex geothermal modelling the 3 d simulations for the coupled fluid flow and heat transport processes are based on the finite element method in the model one geological layer is dissected by a dipping fault sensitivity analyses are conducted to quantify the effects of the fault s transmissivity on the fluid flow and thermal field different fault models are compared with a model where no fault is present to evaluate the effect of varying fault transmissivity the results show that faults have a significant impact on the hydrothermal field varying either the fault zone width or the fault permeability will result in relevant differences in the pressure velocity and temperature field a linear relationship between fault zone width and fluid velocity is found indicating that velocities increase with decreasing widths the faults act as preferential pathways for advective heat transport in case of highly transmissive faults whereas almost no fluid may be transported through poorly transmissive faults

screening and ranking of sedimentary basins for sequestration of co2 in geological media in response to climate change sedimentary basins are suitable to different degrees for co2 geological sequestration as a result of various intrinsic and extrinsic characteristics of which the geothermal regime is one of the most important warm basins are less favorable for co2 sequestration than cold basins because of reduced capacity in terms of co2 mass and because of higher co2 buoyancy which drives the upward co2 migration a set of 15 criteria with several classes each has been developed for the assessment and ranking of sedimentary basins in terms of their suitability for co2 sequestration using a parametric normalization procedure a basin s individual scores are summed to a total score using weights that express the relative importance of different criteria the total score is ranked to determine the most suitable basin or region thereof for the geological sequestration of co2 the method is extremely flexible in that it allows changes in the functions that express the importance of various classes for any given criterion and in the weights that express the relative importance of various criteria examples of application are given for canada s case and for the alberta basin in canada

effective stress coefficient in shales and its applicability to eaton s equation pore pressure within formations determines the mud weight required to build a balancing fluid pressure downhole an improper understanding of the subsurface geology and the formation pressures may result in fracturing the formation if the mud weight is too high in contrast if mud weight is too low then formation fluids can flow into the well potentially leading to well blowouts if not controlled complex geological settings make pore pressure prediction difficult and often inaccurate due to uncertainty in pressure generating mechanisms estimation of proper pore pressures is necessary for designing stable holes and an optimized casing program in exploration knowledge of pore pressures can assist in assessing seal effectiveness and in high grading reservoir sweet spots it also provides useful calibration information for basin modeling hence it becomes very important to accurately predict pore pressures

thermal hydraulic measurements and modelling of the brine circuit in a geothermal well wellhead temperature and pressure are critical parameters of a geothermal well their prediction requires knowledge of the geofluid properties and detailed thermal modelling of the well and formation high salinity and gas content complicate the task this article presents a comprehensive thermal hydraulic wellbore model which is parameterized and validated with data from the gross schoenebeck site and used for a long term prognosis geofluid properties are calculated based on the specific gas and salt contents by determining the vapour liquid equilibrium

a geological database for parameterization in numerical modeling of subsurface storage in northern germany underground land use can play a significant role in future concepts of energy and gas storage and requires an improved understanding of the parameters of potential storage formations saline aquifers for instance of porosity and permeability and also of mineralogical and gas compositions this study aims at providing data examples and calculating vertical spatial variations through variogram analyses of important north german geological reservoirs from dogger rhaetian middle buntsandstein and rotliegend sub groups and formations focusing on the western part of the north german basin vertical correlation lengths of porosity and permeability data range between 0 and 30 m while most results are calculated at approximately 2 4 m and do not show relevant differences among the evaluated formations in the majority of the regarded formations the kozeny carman relationship between porosity and permeability is supported as long as low porosity and permeability values are excluded from the evaluation mineral percentages varied significantly among the evaluated sediments besides quartz ankerite is the main compound in the dogger group while feldspars and clay minerals were more frequent in the rhaetian middle buntsandstein and rotliegend sediments methane was the main gas compound in the reservoirs followed by nitrogen ethane and carbon dioxide this study serves as preparatory work to allow for the parameterization of geological models and a subsequent simulation of fluid transport to evaluate long term safety and impacts of geothermal and gas storage projects

large intraplate earthquakes and static stress changes in the south china coastal region abstract a number of moderate earthquakes occurred in the south china continental edge or coastal area several large earthquakes are sparsely distributed along the seismic belt with the northeast direction between the south china and the continental shelf of the south china sea coulomb stress changes of the 1969 yangjiang main shock ms 6 4 with the following events of the 1986 ml 5 4 the 1987 ml 5 4 and the 2004 ml 5 2 in the yangbian bay area are studied the complex stress patterns of the main shock caused by the dextral pinggang strike slip fault imported on the planes of the normal fault strike slip fault and thrust fault of three events indicate that the distribution of aftershocks mainly located in the areas of positive stress changes and part of aftershocks fall into the stress shadow area due to the reactivity of the local faults the 1969 yangjiang event occurred between the intraplate and the broad plate boundary zone setting when we apply on the empirical relationship between the aftershock durations and the fault loading rate the intersection fault model is proposed and could explain the stress changes of the yangjiang earthquake sequences in south china coastal area the future hazard assessment requires to take account of the stress increase area along the tip of the main shock source fault and off fault stress increase area

the loess section at borden kent se england a 5 3m profile originally described as loess with a buried interglacial soil is reinterpreted from petrographic evidence and thermoluminescence dating as a holocene colluvial accretionary soil mineralogical analyses of coarse silt 16 63 m fractions suggest that most of the silty colluvium was derived from weathered thanet beds upslope though some loess was incorporated during the final depositional phase thin sections show that clay illuviation occurred penecontem poraneously with deposition of colluvium thermoluminescence properties suggest partial optical bleaching of the grains during rapid deposition which is consistent with a holocene colluvial origin

neotectonic regime on the passive continental margin of the northern south china sea abstract between 1989 and 1994 more than 6600 km of reflection seismic profiles were obtained in the south china sea off hong kong with the german research vessel sonne during cruises so 50b so 72a and so 95 a seismo stratigraphic interpretation of this data set leads to a new age assignment of the unconformity t0 which we place within the pleistocene both neogene unconformities t1 and t0 are generated by uplift of the dongsha rise and truncation of their overlying strata this uplift is caused by intrusion of magma into the upper crust our seismic profiles show plutons which have penetrated the sedimentary cover whereby their original stratification in the contact zone is eliminated these magmato tectonic events may be correlated to the two main collision phases between taiwan and the continental margin of east china 5 3 and 3 0 ma ago the collisional events subsequent to the nnw to wnw drift of taiwan transformed the compression into strike slip movements along the continental margin of southeastern china the accompanying stress regime is transtensional with subsidence of the cooling oceanic crust since the cessation of rifting and its consumption beneath the manila trench providing the extensional stress the strike slip movements remobilized many of the rift and drift faults providing pathways for magma ascent the tectonic framework of the northern south china sea is characterized by miocene faults trending ne sw these faults are scarce but are distributed throughout the study area pliocene faults striking ene wsw to ne sw are concentrated west of the dongsha islands and are mostly strike slip in character recent faults are generally oriented ne sw subparallel to the synrift faults they result in part from local uplifts where they are normal in character but strike slip motion also occurs most of the faults involve the basement and represent reactivated zones of weakness of the rift and drift phases

modelling hydrostratigraphy and groundwater flow of a fractured and karst aquifer in a mediterranean basin salento peninsula southeastern italy the control exerted by the hydrostratigraphic structure on aquifer recharge groundwater flow and discharge along the coastal areas of a mediterranean basin salento peninsula about 5 000 km2 wide southern italy is assessed through the development and application of a groundwater flow model based on the reconstruction of the hydrostratigraphic architecture at the regional scale the hydrostratigraphic model obtained by processing surface and subsurface data is applied to map the top of the main aquifer which is hosted in the deep hydrostratigraphic unit corresponding to cretaceous and oligocene limestones with complex geometrical relationships with the sea it is also used to estimate the aquifer recharge which occurs by percolation through overlying younger sediments with low permeability these data are completed with information about the soil use to estimate water abstraction for irrigation and with literature data to estimate the water abstraction for drinking and industrial purposes the above sketched conceptual model is the basis for a finite difference groundwater 2d pseudo stationary flow model which assumes the following fundamental approximations the fractured and karst limestone hydrostratigraphic unit can be approximated at the model scale as a continuous medium for which the discrete darcy s law is valid the transition zone between salt and fresh water is so small with respect to the grid spacing that the ghyben herzberg s approximation for a sharp interface can be applied along the coastline different boundary conditions are assigned if the top of the limestone hydrostratigraphic unit lies either above the sea level the aquifer has a free surface and fresh water is drained or below the sea level the aquifer is under pressure and the contact with sea occurs off shore the groundwater flow model correctly predicts the areas where the aquifer is fully saturated with salt water

a preliminary site selection system for a co2 ages project and its application in china because of the high costs involved in co2 sequestration in deep saline formations it has been difficult for its widespread application in the short term recently however a new technology called combined geothermal production co2 sequestration technology has made the technique more attractive not only by increasing the co2 storage capacity but also by decreasing the operational costs through the utilization of geothermal energy either directly or for the purpose of producing electricity a co2 aided or co2 involved geothermal extraction system co2 ages is presented based on existing technologies and the new ideas of combined geothermal production co2 sequestration introduced in this paper this system can be used to extract geothermal energy from sedimentary aquifer formations low medium temperature at different stages the purpose of this paper is to set up an evaluation system for selecting a suitable site for this co2 ages system there are both similarities and differences in the procedure needed for selecting a site for a conventional pure co2 sequestration and for this co2 ages system both are carried out at different scales including basin region and target formation scales the biggest difference is the temperature gradient which plays an opposite role in the two systems by using the preliminary ranking and screening method presented in this paper it can be shown that the bohaiwan songliao and qiangtang basins have the highest potential for the application of this co2 ages technology however if co2 sequestration is considered alone the ordos tarim and bohaiwan basins should be selected as the best three operational sites in china while preliminary evaluation methods can provide some useful information on the selection of the best sites for the combined geothermal production co2 sequestration technology more detailed work is still required because of the strong uncertainties that exist in the determination of the upper and lower boundaries for each indicator

deep 3d thermal modelling for the city of berlin germany this study predicts the subsurface temperature distribution of germany s capital berlin for this purpose a data based lithosphere scale 3d structural model is developed incorporating 21 individual geological units this model shows a horizontal grid resolution of 500 500 m and provides the geometric base for two different approaches of 3d thermal simulations 1 calculations of the steady state purely conductive thermal field and 2 simulations of coupled fluid flow and heat transport the results point out fundamentally different structural and thermal configurations for potential geothermal target units the top of the triassic middle buntsandstein strongly varies in depth 159 2 470 m below sea level and predicted temperatures 15 95 c mostly because of the complex geometry of the underlying permian zechstein salt the top of the sub salt sedimentary rotliegend is rather flat 2 890 3 785 m below sea level and reveals temperatures of 85 139 c the predicted 70 c isotherm is located at depths of about 1 500 2 200 m cutting the middle buntsandstein over large parts of berlin the 110 c isotherm at 2 900 3 700 m depth widely crosscuts the sedimentary rotliegend groundwater flow results in subsurface cooling the extent of which is strongly controlled by the geometry and the distribution of the tertiary rupelian clay the cooling effect is strongest where this clay rich aquitard is thinnest or missing thus facilitating deep reaching forced convective flow the differences between the purely conductive and coupled models highlight the need for investigations of the complex interrelation of flow and thermal fields to properly predict temperatures in sedimentary systems

geological 3 d model of the larger altensalzwedel area germany for temperature prognosis and reservoir simulation in the framework of the german r d programme clean co2 large scale enhanced gas recovery in the altmark natural gas field the geological structure of an area encompassing the altensalzwedel sub field and its surrounding was analysed in detail a 3 d model was developed that contains the major geological formations and their general lithology including the natural gas reservoir in the permian rotliegend the immediate cap rock permian zechstein of the reservoir and its overburden based on this geological model a 3 d steady state thermal model was generated as part of a shared earth model the parameterisation of the geological model layers with thermal rock properties is based on laboratory and well log data the model shows temperature changes in dependence of geological structure and of different rock thermal conductivity the calculated surface heat flow is high 80 mw m 2 for most of the area which is in accordance to measured surface heat flow temperature on top of the rotliegend reservoir is variable ranging from 110 to 150 c the quantification of temperature changes versus depth as well as laterally in the reservoir are valuable input data for modelling the dynamic processes of co2 injection within clean

the correlation between low tectonic stress and the appalachian basin quiet zone abstract in order to assess the nature of the appalachian basin quiet zone abqz a region of low seismic activity a minimum horizontal stress profile from sonic logs was calibrated using hydraulic fracture stress measurements in a well from mckean county pa the calibrated minimum horizontal stress profile that best fits with the hydraulic fracture stress data was established using an extended eaton s model that treats rock as a transverse isotropic material with a vertical symmetry axis tiv to achieve a best fit several assumptions are introduced 1 a constant tectonically induced elastic strain of ehmax 3 3 10 4 2 an anisotropic velocity model annie approximation for shales and 3 a bimodal pore pressure distribution with abnormally high pore pressure in the marcellus gas shale other calibration methods assume an isotropic medium a constant tectonic strain gradient corresponding to zero stress at ground surface or constraints from sidewall core data to estimate stiffness constants by testing four calibration methods we find that stress profiles are affected by multiple factors including the ratio of maximum tectonically induced elastic strain over minimum tectonic strain pore pressure in the marcellus biot s coefficients and elastic properties sensitivity analysis was conducted to analyze the influence of these parameters our stress profile is most influenced by pore pressure and tectonically induced elastic strain while other factors had much smaller effects tectonically included strain in the abqz is insufficient to achieve the critical stress necessary to induce frictional slip on favorably oriented faults in the sedimentary cover which presumably speaks to the lack of earthquakes in the basement of the abqz however induced earthquakes from deep disposal wells suggest that basement at the edge of the abqz may be decoupled from the sedimentary cover in which case the cover has relaxed through a time dependent deformation mechanism such as pressure solution creep

scanning electron microscope study of zircons and rutiles from a podzol chronosequence at cooloola queensland australia summary a chronosequence of four soils derived from aeolian deposited sand at cooloola along the eastern coast of southern queensland has been studied to document predepositional and pedogenic changes in zircon and rutile grains in the fine sand fraction 53 125 m with increasing soil age the soils range in age from holocene typic quartzipsamment presently drifting sand to mid pleistocene spodic quartzipsamment 90 ka bp parent materials are moderately stratified sands with irregular depositional layers in places having high concentration of heavy mineral grains scanning electron microscopy was used to characterize grain surface microtexture by a semi quantitative method based on frequency of occurrence of ten classes of surface microtextures pedogenic changes were quantified and differences between horizons in the same profile between different profiles within the same horizon and between minerals were tested for significance using the 2 distribution zircon grains are less chemically weathered during pedogenesis than rutile possibly due to the higher iron content of the latter however zircons tend to show more features which can be associated with physical alteration rutile grains in the illuviated b2hs horizons of the troporthod and spodic quartzipsamments are more thickly coated with poorly crystalline iron and alumino silicate compounds compared with zircon grains and the presence of grain coatings does not seem to have prevented the surfaces of grains from developing solution pits with increasing age there is a preponderance of weathering features on grains of both minerals the presence of various shapes and surface microtextures on grains from the different soils suggests a multiple grain source for zircon and rutile and a complex predepositional history for these minerals nevertheless microtextural features of zircons and rutiles are valuable for the interpretation of the extent and nature of post depositional weathering

regional waveform constraints on the source parameters of the xunwu china earthquake of 2 august 1987 with implications for mid plate seismotectonics abstract the xunwu china earthquake of 2 august 1987 m s 5 3 was a damaging intraplate event in a stable continental region in this paper long period p and sh waves recorded by the world wide standardized seismograph network and the chinese standard seismic network stations within 30 epicentral distance have been modeled to determine the focal mechanism and source parameters of the mainshock using body wave waveform synthesis and p wave first motions the focal parameters are determined as follows strike 338 6 dip 53 4 rake 39 7 focal depth 7 4 k moment 3 63 1 57 10 23 dyn cm and stress drop 2 6 1 2 bars analysis of the local tectonic setting geometry of isoseismals and aftershock distribution indicates that the earthquake probably ruptured along a nw se striking secondary fault near its intersection with a nne ssw trending major fault the fault motion was normal oblique slip with a left lateral strike slip component based on the p and t axes the epicentral area is subject to nw se compression with a relatively large plunge and a nearly horizontal ne sw extension the observed large plunge of the p axis is probably due to an anomalous local stress field in comparison with other intraplate events the stress drop of the xunwu earthquake is very low suggesting a weak and fractured crustal medium in the epicentral region

episodic rifting and subsidence in the south china sea the south china sea experienced at least three stages of rifting and two intervening stages of sea floor spreading since the early cretaceous its evolution can be described by an episodic model of tectonism one of thermal cooling and subsidence pulsed by temporally and spatially confined heating events analysis of regional geologic and geophysical data suggests episodes of rifting and associated thermal activities initiated during the late cretaceous the late eocene and the late early miocene the rift system corresponding to the first episode trends northeast southwest whereas those of the second and third trend east west these two trends coincide with the orientations of the major tectonic lineations within the basin age estimates from heat flow and bathymetric data suggest the oceanic crust in the southwest subbasin is considerably older 55 ma than that in the northwest 35 36 ma or east 32 ma subbasins the episodic tectonic model is supported by basin subsidence analysis subsidence especially subsidence rate curves derived from the regional well data demonstrates that unlike a classic atlantic passive margin thermal subsidence in the south china sea was punctuated by rapid subsidence events which are chronologically consistent with the rifting episodes in terms of hydrocarbon potential the episodes of rifting and drifting would be conducive to the development of overprinted structures and the deposition of several discrete transgressive packages of source rocks and reservoirs separated by widespread unconformities the thermal maturity of sedimentary organic matter affected by episodic rifting and subsidence may be greater than expected on a purely passive margin of equivalent age that had not experienced repeated heating

estimation of co2 saturation during both co2 drainage and imbibition processes based on both seismic velocity and electrical resistivity measurements summary in order to monitor injected carbon dioxide co2 simultaneous measurements of seismic velocity and electrical resistivity are employed during the drainage co2 injection and imbibition water injection processes of a berea sandstone supercritical co2 10 mpa at 40 o c was injected into a water saturated berea sandstone in the drainage stage and monitored via simultaneous measurements after the injection of supercritical co2 fresh distilled water was injected into the co2 injected sandstone during the imbibition stage electrical resistivity and p wave velocity measurements acquired during the drainage and imbibition stages were employed to evaluate co2 saturations sco2 based on the resistivity index and the gassmann fluid substitution equations respectively comparing estimated values for sco2 saturation against those from volume derived sco2 based on analysis on injected and drained fluid volumes in the drainage process we conclude that gassmann brie and resistivity index are suitable for the evaluation based on p wave velocity and electrical resistivity respectively rt based estimation properly tracks the variation in sco2 even when sco2 is large 0 15 while vp based estimation is sensitive to the variation in sco2 when sco2 is small 0 1 while properly estimating sco2 when sco2 is small 0 1 monitoring the co2 imbibition process confirms residual co2 saturation within the sample

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

thermo hydro mechanical modeling of carbon dioxide injection for enhanced gas recovery co2 egr a benchmarking study for code comparison the objective of this paper was to investigate the thm coupled responses of the storage formation and caprock induced by gas production co2 egr enhanced gas recovery and co2 storage a generic 3d planer model 20 000 3 000 100 m consisting of 1 200 m overburden 100 m caprock 200 m gas reservoir and 1 500 m base rock is adopted for the simulation process using the integrated code tough2 eos7c flac3d and the multi purpose simulator opengeosys both simulators agree that the co2 egr phase under a balanced injection rate 31 500 tons year will cause almost no change in the reservoir pressure the gas recovery rate increases 1 4 in the 5 year co2 egr phase and a better egr effect could be achieved by increasing the distance between injection and production wells e g 5 83 for 5 km distance instead of 1 2 km in this study under the considered conditions there is no evidence of plastic deformation and both reservoir and caprock behave elastically at all operation stages the stress path could be predicted analytically and the results show that the isotropic and extensional stress regime will switch to the compressional stress regime when the pore pressure rises to a specific level both simulators agree regarding modification of the reservoir stress state with further co2 injection tension failure in reservoir could occur but shear failure will never happen under these conditions using tough flac a scenario case is also analyzed with the assumption that the reservoir is naturally fractured the specific analysis shows that the maximal storage pressure is 13 6 mpa which is determined by the penetration criterion of the caprock

dynamic reservoir characterization of vacuum field this article briefly describes the 4 d 3 c technique and a research application of it at vacuum field new mexico by the reservoir characterization project rcp at the colorado school of mines rcp a consortium of 32 oil companies has been involved in 4 d 3 c research since 1995 because this technique has the potential to provide the most complete information needed for efficient reservoir characterization for example when three components of source are used nine times the data of a conventional 3 d p wave survey are recorded

mineral weathering in forest soils and its relevance to the preservation of the buried archaeological resource there is more woodland in britain now than for many centuries and considering many international climate change mitigation policies woodland cover both in britain and internationally is being promoted however neither the management of existing woodlands nor their expansion should be at the expense of important archaeological evidence due to the large number of known archaeological sites the large areas of land with uninvestigated archaeological potential and the expanding woodland cover suitable mitigation strategies need to be developed to allow preservation in situ of important sites an understanding of how woodland soils and the buried archaeological resource interact is therefore essential this paper utilises ongoing environmental research into the mineral weathering rates in forest soils and considers its application to artefact preservation the study concludes that soil water ph its movement and the saturation of dissolved ions in the soil solution are major factors determining both mineral and artefact longevity a simple guide to artefact longevity based on these properties is proposed and a geochemical model for predicting loss is tested these tools could be applied to any soil or individual horizon irrespective of land use

evaluating the geothermal heat pump potential from a thermostratigraphic assessment of rock samples in the st lawrence lowlands canada the installation cost and the performance of geothermal heat pump systems are influenced by the thermal state and properties of the subsurface the ground ability to transfer heat described by thermal conductivity is a dominant factor affecting the favorability of closed loop ground heat exchangers installed in vertical boreholes a study that aimed at evaluating the geothermal heat pump potential by mapping the thermal conductivity of rock sequences was therefore performed for the st lawrence lowlands sedimentary basin in canada thermal conductivity was measured in the laboratory on rock samples collected in outcrops and used to complete design calculations of a geothermal system with a single borehole results allowed the definition of thermostratigraphic units that can be linked to depositional environments basal quartz rich sandstones formed in a rift environment show a high geothermal potential overlying dolomites argillaceous limestones and shales deposited in a passive margin evolving to a foreland basin exhibit a transition toward the top from high to low geothermal potential upper turbidites and molasses have a moderate geothermal potential the thermal conductivity of the thermostratigraphic units is dominantly influenced by the mineralogy of the sedimentary rocks understanding their origin is a key to improve geothermal resource assessment and system design to anticipate new installations in the area

thermo optical parameter acquisition and characterization of geologic properties a 400 m deep bhe in a karstic alpine marble aquifer to dimension a geothermal array it is necessary to explore the geophysical and geologic qualities of the subsoil at the following example the project engineering of a prospective geothermal array is shown from the investigation up to the execution planning for the geothermic investigation a 400 m 1312 ft deep drilling was established and equipped with 50 mm 1 97 in duplex bhe with the mounting of the bhe a fiberglass hybrid cable was inserted as a loop parallel to the shanks of the bhe by means of optical frequency domain reflectometry ofdr an enhanced geothermal response test has been executed due the high local resolution of the resulting profile of conductivities the geological profile can be differentiated in areas with mainly conductive and areas of convective influenced heat transfer by knowledge of these both parts and its parameters the incident of groundwater flow on the bhe can be calculated peclet number analysis darcy velocity with the help of the ascertained geophysical and hydraulic rock parameters solid rock cleavages and karst cavity could be identified also the undisturbed ground temperature the effective thermal conductivity and areas with different geothermal gradients and the groundwater velocity in cleaved and caveated rocks could be determined

estimation of biot s effective stress coefficient from well logs effective stress governs the mechanical response of rock formations to variations in stress and pore pressure which affect wellbore stability and reservoir integrity during drilling and production biot s coefficient is employed to calculate effective stresses from total stress and pore pressure therefore the measurement of biot s coefficient becomes crucial however the laboratory measurement of biot s coefficient is expensive and laborious this paper presents three methods for computing biot s coefficient using logging data the first method calculates biot s coefficient using the existing empirical correlations between porosity and biot s coefficient the second and third methods calculate biot s coefficient using dynamic rock and solid bulk modulus computed using rock and solid wave velocities respectively however the second and third methods calculate the necessary solid wave velocities in different ways the second method calculates solid shear and compressive velocities vs and vp using a newly developed correlation between the differential pressure porosity and wave velocity of sandstone the third method calculates solid wave velocities based on the significant finding that the vp vs ratio with respect to the s wave velocity is constant for sediments including highly compacted sand case studies were undertaken using logging data from the gulf coast gas wells it was found that biot s coefficient calculated using the first method was highly dependent on the chosen relation while the coefficients calculated using the second and third methods were related to well logs results from the third method show that biot s coefficient deflects to higher values in situations where gamma ray surveys read low api values this is in agreement with the phenomenon that rocks with a smaller api should have lower a clay content and bigger value of biot s coefficient therefore the third method is more reliable and also requires fewer input parameters

the role of trace minerals in chemical weathering in a high elevation granitic watershed estibere france chemical and mineralogical evidence we investigated chemical weathering in a high elevation granitic environment in three selected watersheds located in the pyrenees france the sites were located on glacial deposits derived from similar hercynian 300 ma granites characterized by the occurrence of zoned plagioclases and trace calcic phases epidote prehnite sphene apatite the surface waters at those sites show high ca na molar ratios 1 which could not be explained by the dissolution of the major plagioclase oligoclase present in the rocks the coupled approach of investigating stream water chemistry and the mineralogy and chemistry of rocks and soils allowed us to explore the role of the weathering of trace calcic minerals in calcium export at the watershed scale the weathering of the trace calcic minerals which represent 1 of the total rock volume are responsible for more than 90 of the calcium export at the sites annual cationic fluxes 23 104 eq km2 yr calculated for the estibere watershed are among the highest reported for high elevation systems draining granitic rocks and 80 of this annual cationic flux can be attributed to the weathering of trace calcic phases calculations based on isotopic values 87sr 86sr go in the same direction except apatite the trace calcic phases appear to be mainly silicates thus the type of chemical weathering observed in the estibere watershed may have an influence on atmospheric co2 consumption by granite weathering however comparison with other watersheds draining granitic environments worldwide and with the two other sites in the pyrenees indicate that the role of trace calcic phases is important in most young environments exposed to chemical weathering e g high elevation catchments on glacial deposits other factors such as the date of glacial retreat the physical denudation rate the hydrological functioning of the watershed and the nature and structure of the soil cover are also important

numerical studies on co2 injection brine extraction process in a low medium temperature reservoir system co2 sequestration in deep saline formations has been proved to be an effective method for reducing greenhouse emissions into the atmosphere however pure sequestration of co2 will add to the costs incurred by both industries and governments a win win method of co2 injection and hot brine water extraction can become attractive to the investors as it will not only increase the storage capacity of the injected co2 but also offset the costs by selling and using the produced hot water for industrial agricultural or household purposes for instance water from very hot geothermal reservoirs t 150 c can be used for electricity generation in power plants and water from low medium temperature reservoirs the most predominant in natural systems are more popular for direct use e g in heating systems household hot water baths aquaculture etc in this paper low medium geothermal reservoirs widely distributed in china especially those in the ordos basin were selected for the numerical case studies using tough2mp with the eco2n module for the simulations generally simulation parameters were taken from the ordos basin where the first full integration co2 sequestration project had been operated since 2010 the simulations in the base case study lasted 35 years based on the lifespan of a normal geothermal project shallow re injection systems were also considered to investigate the influence of thermal breakthrough pressure perturbation etc results show that injection of cold co2 causes sharp decrease in temperature in the reservoir region near the injection well which is enlarged with continuous injection the region near the production well is dominated by different fluid phases during the co2 driven process including a single water phase a two phase fluid water and co2 and a phase of almost pure co2 results also show that the co2 breakthrough lags far behind the pressure response in the geothermal production system before breakthrough the injected co2 pressurizes the reservoir improving the overall performance of the geothermal reservoir furthermore the heat extraction efficiency of co2 based system is obviously higher than h2o based system

modelling of fractured carbonate reservoirs outline of a novel technique via a case study from the molasse basin southern bavaria germany fluid flow in low permeable carbonate rocks depends on the density of fractures their interconnectivity and on the formation of fault damage zones the present day stress field influences the aperture hence the transmissivity of fractures whereas paleostress fields are responsible for the formation of faults and fractures in low permeable reservoir rocks fault zones belong to the major targets before drilling an estimate for reservoir productivity of wells drilled into the damage zone of faults is therefore required due to limitations in available data a characterization of such reservoirs usually relies on the use of numerical techniques the requirements of these mathematical models encompass a full integration of the actual fault geometry comprising the dimension of the fault damage zone and of the fault core and the individual population with properties of fault zones in the hanging and foot wall and the host rock the paper presents both the technical approach to develop such a model and the property definition of heterogeneous fault zones and host rock with respect to the current stress field the case study describes a deep geothermal reservoir in the western central molasse basin in southern bavaria germany results from numerical simulations indicate that the well productivity can be enhanced along compressional fault zones if the interconnectivity of fractures is lateral caused by crossing synthetic and antithetic fractures the model allows a deeper understanding of production tests and reservoir properties of faulted rocks

pedogenic and geomorphic evolution of a buried dune palaeocatena at magilligan foreland northern ireland abstract field description and laboratory analyses of a complex stratigraphy recently exposed near magilligan point have elucidated the late holocene evolution of magilligan foreland n ireland a marine beach ridge palaeocatena passes northwards into a penecontemporaneous aeolian dune palaeocatena both include soils and peat filled depressions and are overlain by an aeolian dune sand a second dune sand is confined to the south of magilligan foreland the thickness of the decalcified zone of the palaeocatena varies from 0 4 m near the crest of the palaeodune to 2 m below its slopes the palaeodune core exhibits large scale cross stratification enclosing unusual small scale reverse flow cross stratified sets d 90 90 depletion values indicate similar weathering intensities in the palaeocatena and in the overlying sand but deeper weathering in the former a mineral stability sequence has been constructed and unweathered sand identified which indicates the original composition of the magilligan deposits inter profile differences in weathering rates are attributed to variations in local environments

strike slip faulting on the northern margin of the south china sea evidence from two earthquakes offshore of hainan island china in december 1969 in december 1969 two earthquakes mb 4 7and4 8 occurred in a rift basin offshore of hainan island china in a passive continental margin environment by modeling short period p and long period sh waveforms recorded at wwssn stations we have determined the focal mechanisms and source parameters of these two events to be strike 45 7 dip 78 4 rake 6 7 focal depth 8 3 km seismic moment 1 73 0 4 1023 dyne cm and stress drop 56 6 bar for the 17 december event and strike 36 6 dip 60 4 rake 2 7 focal depth 8 3 km seismic moment 1 43 0 13 1023 dyne cm and stress drop 47 6 bar for the 20 december event results of relative location computed from differential arrival times indicate that the 20 december event is slightly deeper than the 17 december event but within the resolution limit of the waveform constraint analysis of the local tectonic setting geometry of isoseismals aftershock distribution and fault plane solutions indicate that the 17 december event probably ruptured along a ne sw striking fault on the northern margin of the songtao uplift in the qiongdongnan basin the 20 december event probably ruptured along another major ne sw striking fault on the northern margin of the qiongdongnan basin the fault motions of both earthquakes were almost pure left lateral strike slip p and t axes show that the epicentral area is subject to nearly horizontal n s directed compression and e w directed extension consistent with previously observed stress field in the area the two earthquakes represent reactivation of pre existing zones of weakness in the basin by the present day tectonic stress field a review of earthquakes in the region indicates that strike slip motion is characteristic of the seismotectonics of the northern margin of the south china sea

development of a feldspar weathering index and its application to a buried soil chronosequence in southeastern england abstract an index of feldspar weathering ifw has been developed based upon the assignment of individual grains to weathering classes defined in terms of progressive changes in surface morphology identifiable under a polarising microscope the index was used to test the hypothesis that profiles of a buried paleosol developed on the higher terraces of the river thames in southeastern england are more weathered than those formed on lower and younger terrace surfaces ifwr ratio between the ifw of soil and parent material and ifwd difference between the ifw of soil and parent material values support a trend of increased weathering with assumed terrace age although the pattern is less clear and conclusive towards the base of the terrace sequence anomalies in the dataset can be attributed to a range of factors including the possible variable composition and structure of the feldspars the nature of the parent material samples and probable fluctuations in soil processes and environments over time notwithstanding these problems some of which are specific to the study reported here the technique and general approach clearly have more widespread potential for the semi quantitative comparison of the relative weathering statuses of soils

body wave waveform constraints on the source parameters of the yangjiang china earthquake of july 25 1969 a devastating earthquake in a stable continental region on july 25 1969 anm s 5 9 earthquake shook the kwangtung province near yangjiang china casualties and extensive damage were reported in the epicentral area the yangjiang earthquake occurred within the passive margin located along china s southeast coast this stable continental setting is seismically one of the most quiet regions of china historic records indicate this earthquake to have been the first devastating one in the area a remarkable feature of this earthquake sequence is that its foreshocks and aftershocks are relatively small in terms of number and magnitude despite the relatively large main shock waveforms of long and short period teleseismicp and long period teleseismicsh waves have been modeled to estimate the source parameters for this earthquake the focal mechanism determined is predominately strike slip with a small normal component strike 263 dip 79 rake 194 and is in good agreement with observations in the epicentral area regarding dislocation direction of fissures distribution of aftershocks and isoseismals the average seismic moment is 5 15 1024 dyne cm and the focal depth is estimated to be 9 km the earthquake is characterized by a rather short source time function and a high stress drop of approximately 380 bars the observed pattern of the foreshock main shock aftershock sequence is interpreted in terms of the large stress drop associated with the main shock and the material properties at and near the source thep axis orientation lies roughly nw se and is consistent with the maximum compressive stress observed along the coast of southeast china this stress orientation is consistent with the nw subducting philippine sea plate and the se ward push from central china due to the convergence between indian and eurasian subcontinents

simulation of co2 plume movement in multilayered saline formations through multilayer injection technology in the ordos basin china deep saline aquifers still remain a significant option for the disposal of large amounts of co2 from the atmosphere as a means of mitigating global climate change the small scale carbon capture and sequestration demonstration project in ordos basin china operated by the shenhua group is the only one of its kind in asia to put the multilayer injection technology into practice this paper aims at studying the influence of temperature injection rate and horizontal boundary effects on co2 plume transport in saline formation layers at different depths and thicknesses focusing on the variations in co2 gas saturation and mass fraction of dissolved co2 in the formation of brine in the plume s radial three dimensional field around the injection point and interlayer communication between the aquifer and its confining beds of relatively lower permeability the study uses the eco2n module of tough2 to simulate flow and pressure configurations in response to small scale co2 injection into multilayer saline aquifers the modelling domain involves a complex multilayer reservoir caprock system comprising of a sequence of sandstone aquifers and sealing units of mudstone and siltstone layers extending from the permian shanxi to the upper triassic liujiagou formation systems in the ordos basin simulation results indicate that co2 injected for storage into deep saline aquifers cause a significant pressure perturbation in the geological system that may require a long duration in the post injection period to establish new pressure equilibrium the multilayer simultaneous injection scheme exhibits mutual interference with the intervening sealing layers especially when the injection layers are very close to each other and the corresponding sealing layers are thin the study further reveals that injection rate and temperature are the most significant factors for determining the lateral and vertical extent that the co2 plume reaches and which phase and amount will exist at a particular time during and after the injection in general a large number of factors may influence the co2 water fluid flow system considering the complexity in the real geologic sequence and structural configurations therefore optimization of a co2 injection scheme still requires pursuance of further studies

effect of fines content and void ratio on the saturated hydraulic conductivity and undrained shear strength of sand silt mixtures the hydraulic conductivity represents an important indicator parameter in the generation and redistribution of excess pore pressure of sand silt mixture soil deposits during earthquakes this paper aims to determine the relationship between the undrained shear strength liquefaction resistance and the saturated hydraulic conductivity of the sand silt mixtures and how much they are affected by the percentage of low plastic fines finer than 0 074 mm and void ratio of the soil the results of flexible wall permeameter and undrained monotonic triaxial tests carried out on samples reconstituted from chlef river sand with 0 10 20 30 40 and 50 non plastic silt at an effective confining pressure of 100 kpa and two initial relative densities d r 20 91 are presented and discussed it was found that the undrained shear strength liquefaction resistance can be correlated to the fines content intergranular void ratio and saturated hydraulic conductivity the results obtained from this study reveal that the saturated hydraulic conductivity k sat of the sand mixed with 50 low plastic fines can be in average four orders of magnitude smaller than that of the clean sand the results show also that the global void ratio could not be used as a pertinent parameter to explain the undrained shear strength and saturated hydraulic conductivity response of the sand silt mixtures

development of a semi analytical method to calculate depth dependent temperature and stress changes investigation of micro seismicity at unterhaching uha gt 2 geothermal well since october 2007 when the hydrothermal production of geothermal energy from the deep underground started at unterhaching near munich germany several micro seismic events have been observed three of the five strongest events with local magnitudes ml ranging from 2 0 to 2 4 occurred in 2008 and were partially felt by the residents the reasons for these events are not clear these micro seismic events could have been induced by a variety of factors the strongest micro seismic event was observed soon after the injection of cold water pointing to an intrinsic relationship between micro seismic event and cold water injection one of the possible reasons for the observed micro seismic events could be the reinjection of cooled thermal water into the hotter underground inducing stress redistribution and shear failures in the reservoir formations around the injection wellbore uha gt 2 to justify this reason further investigation will be carried out in another simulation study to verify whether the shear failures induced by cold water injection were the major cause for the occurrence of these micro seismic events nevertheless before the simulation of shear failures temperature profiles in both the wellbore and surrounding rocks as well as their corresponding thermal stresses during cold water injection should be established in this study in this paper a new semi analytical simulation method has been developed to calculate simultaneously the temperature profiles in the wellbore and the surrounding rock formations and also determine the corresponding thermal stresses in the surroundings near wellbore field and subsequently verified by analytical solution results show that great tensile thermal stresses in the reservoir were initiated by the injection of the cooled thermal water in the injection wellbore uha gt 2 the results of the simulated thermal stresses indicate a great potential for the ensuing shear failures to affect an extensive area and could be used as input data for the planned shear failure simulations in the future

mode of strain release of three graben associated earthquakes the nature of graben associated earthquakes has been investigated through a study of three earthquake sequences using various seismological geophysical and geological data the three earthquake sequences are the hsingtai china earthquakes maximum magnitude ms 7 2 of march 1966 the nevada earthquakes maximum m 7 1 of 1954 and the new madrid earthquakes maximum ms 8 8 of 1811 1812 these earthquake sequences represent a unique mode of strain release away from plate margins and have bearings on earthquake hazard evaluation a number of similarities have been observed during these earthquake sequences for instance all the three sequences are characterized by large multiple shocks or swarms which last from several weeks to several months among the large multiple shocks in each sequence the largest one usually is not the first one migrations of epicenters were observed during the hsingtai and the new madrid earthquakes significant amount of strike slip motion was associated or inferred with all these three sequences in particular for the hsingtai earthquakes the swarm of multiple shock activities is probably due to induced instability or strong coupling and interactions among a series of adjacent faults in a heterogeneous graben the strike slip motion can be explained by a change or a rotation of stress orientation after the formation of a graben the graben events are similar to the earthquake swarms associated with spreading oceanic ridges but with significant differences available data indicate that the recurrence intervals for the three graben earthquake sequences studied are of the order of thousands of years

an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence the orientations of fault planes and slip directions indicated by a population of earthquake focal mechanisms can be used to determine best fit regional principal stress directions and r 2 1 3 1 a measure of relative stress magnitudes under the assumption of uniform stress in the source region this analysis allows for the possibility that failure occurs on preexisting zones of weakness of any orientation in the inversion we perform a grid search of stress models to find the one which requires the smallest total rotation of all the fault planes that is needed to match the observed and predicted slip directions the method allows for errors in orientations of both the fault planes and slip directions we have an objective means for identifying the more likely of the two possible fault planes from each focal mechanism relative to a given stress model thus we do not face the problem of ambiguity of nodal planes which plagues other analyses of this kind by using a grid search of stress models rather than a linearization scheme we are able to perform a realistic error analysis and thus establish confidence limits for the preferred regional stresses the method can be used to investigate possible stress inhomogeneities during earthquake sequences by analyzing subsets of the data population the technique has been applied to 76 events from the san fernando earthquake sequence for which we have found best fit stresses plunge and azimuth 1 7 187 2 27 281 3 62 84 and r 0 65 the average misfit between this stress model and all the data is about 8 and all but eight of the aftershocks have misfits of less than 20 these values are considerably less than the uncertainty of the focal mechanism determinations therefore significant stress inhomogeneities are not required by the data our analysis does not support the suggestion of a change in stresses during the aftershock sequence as proposed by others on the basis of an apparent change in focal mechanisms

investigation of a new hdr system with horizontal wells and multiple fractures using the coupled wellbore reservoir simulator tough2mp well eos3 geothermal energy is renewable sustainable and available in large amounts the hot dry rock hdr systems in particular have the largest potential for long term sustainability and therefore draw a lot of attention the combination of horizontal wells and the technology of multiple transverse fractures technology is an attractive approach of such hdrs which is called in this paper as the specific egs enhanced geothermal system the main objective of this paper is to study the heat extraction over a period of 20 years by water circulating in a deep geothermal reservoir using this specific egs the wellbore flow module t2well eco2n is implemented in the parallelized simulator tough2mp as a new code tough2mp well eos3 which enables coupled wellbore reservoir simulations using this newly developed code the sensitivity of heat extraction against various parameters of the formation and fractures is assessed the influences of the fracture geometry and the space of two neighborhood fractures on the geothermal energy performance are analyzed according to the results in this paper the injection rate the wellbore radius and the fracture permeability are three main influence factors for the distribution of total flow through individual fractures a large injection rate a small wellbore radius and a large fracture width will cause the short circuit effect which reduces the performance of this specific egs compared with the classic hdr system doublet or triplet vertical wells single fracture this specific egs has a much higher performance and a longer duration of the economic production furthermore the horizontal wells can also be drilled in both directions of the minimum horizontal stress instead of in just one direction so that the energy performance is doubled and the investment cost per kw energy production is decreased and the advantage of this specific egs is significantly enlarged

conceptualization and characterization of a coastal multi layered aquifer system in the taranto gulf southern italy in some mediterranean karst areas groundwater is often the only available supply for fresh water besides the contamination induced by human activities coastal aquifers often suffer from the saltwater intrusion phenomenon which can be enhanced by both extensive withdrawals and climatic changes establishing an effective set of regulatory and management measures to ensure the sustainability of coastal aquifers requires a deep knowledge about natural and anthropic stresses involved in groundwater dynamics in this regard a prior conceptualization of aquifer systems and a deeper characterization of balance terms through mathematical modeling are of paramount importance in this paper previous works on the three dimensional hydrostratigraphic characterization and two dimensional groundwater flow modeling at the regional scale for the salento peninsula southeastern italy are shown to provide a fundamental basis for an overall conceptualization of the multi layered aquifer system of the taranto gulf northwestern salento this is done by identifying source terms and providing a preliminary estimate of different balance terms based on available data and information then a further characterization will be provided using three dimensional groundwater flow models and calibration techniques based on the solution of an inverse problem as a result the hydraulic features of the deep karst aquifer can be mapped the stresses due to human water demanding activities and the occurrence of the saltwater intrusion phenomenon were analyzed and possible weaknesses of the conceptual and of the preliminary numerical model pointed out

the deep geothermal potential of the berlin area in this study we model the geothermal potential of deep geological formations located in the berlin region in germany berlin is situated in a sedimentary geological setting northeastern german basin comprising low enthalpic aquifers at horizons down to 4 5 km depth in the berlin region the temperature increases almost linearly with depth by about 30 k per kilometer thus allowing for direct heating from deep aquifer reservoirs in principle our model incorporates eight major sedimentary units jurassic keuper muschelkalk upper middle lower buntsandstein zechstein salt and sedimentary rotliegend owing to lack of available petro physical rock data for the berlin region we have evaluated literature data for the larger northeastern german basin to develop a thermodynamic field model which regards depth corrected equations of state within statistical intervals of confidence integration over the thicknesses of the respective structural units yields their heat in place energy densities associated with the pore fluid and the rock matrix under local conditions in joule per unit area at the surface the model predicts that aquifers in the middle buntsandstein and in the sedimentary rotliegend may well exhibit energy densities about 10 gj m 2 for the pore fluids and 20 gj m 2 to 40 gj m 2 for the rock matrices on average referring these figures to the city area of berlin about 892 km2 a significant hydrothermal potential results which however remained undeveloped until today for the reason of present development risks the model accounts for these risks through statistical intervals of confidence which are in the order of 60 to 80 of the trend figures to minimize these uncertainties scientific field explorations were required in order to assess the petro physical aquifer properties locally

the identification of fault zones in deep karst aquifer of north china coal mine using parallel directional well logs water inrush from ordovician karst aquifer in north china coal mine has become a key issue on underground coal mining to address this problem it is necessary to identify fault zones because fault zones might connect limestone aquifers and coal seams enabling ordovician karst water to enter the mine in the study area a series of parallel directional holes were drilled along ordovician limestone at depths between 70 and 90 m under ordovician limestone boundary to conveniently detect fault zones and govern mine water disasters a series of natural gamma ray logging while drilling grlwd were undertaken the entire detecting region can be comprehensively covered by several directional borehole groups then fast fourier transform and short time fourier transform approaches were employed on the basis of grlwd data and geological data to extract faults information a segmented identification method for deep fault zones was established in this study this method can be used to markedly improve the identification of fault zones within ordovician limestone or the unitary lithology formation and provide crucial information relevant for deep coal mining safety

tidal current dominated depositional environments in the central northern yellow sea as revealed by heavy mineral and grain size dispersals abstract this study confirms that the fine sand sized detritus in the central northern yellow sea is chiefly derived by the yellow river and explains the holocene yellow river dispersal system and the preservation of transgressive deposits by heavy mineral and grain size analyses micas which are sensitive to hydraulic sorting offer an effective key for identifying the dispersal of holocene yellow river derived fine grained sediments the heavy mineral compositional changes are attributed to hydraulic sorting by different marine dynamics and various mixing with additional local transgressive deposits of miscellaneous provenance the effects of hydraulic sorting are dominated by holocene tidal currents and by foreshore waves during the rapid transgression respectively the former results in obvious enrichments of garnet and common stable species such as ti oxides tourmaline and titanite whereas the latter seems more remarkable for the compositional changes with further depletion of epidote actinolite tremolite and zoisite clinozoisite the central yellow sea mud deposit and the alongshore muddy zone off the southern liaodong peninsula are opposite to each other as a pair of structurally symmetric coalesced terminal lobes far away from the high energy strait between cape chengshan and changsan got the haiyang subaqueous clinoform as another terminal lobe is revealed by a heavy mineral index which represents an extremity of deposits accumulated by the modern yellow river derived sediments off the southwestern shandong coast a small mud patch is revealed roughly corresponding to the central regime of the amphidromic system of principal m2 constituent the tidal current dominated depositional pattern proposed here emphasizes the importance of time velocity asymmetry of tidal currents such a dynamic mechanism is primarily responsible for the dispersal of the modern yellow river derived sediments when they are entrained from the bohai sea to the south yellow sea through the bohai strait and the strait between cape chengshan and changsan got

seismic moment assessment of earthquakes in stable continental regions ii historical seismicity summary this part i study in conjunction with part 11 develops a method to determine within specified uncertainty bounds the seismic moment and thus moment magnitude of all earthquakes of stable continental regions scr for which instrumental or intensity data exist its basis is polynomial regression analysis using a database of scr earthquakes with direct seismic moment determination the independent variables include modern teleseismic magnitudes and regional magnitudes part i and isoseismal areas or number of recording stations part 11 part i11 is an application of the methodology of parts i and i1 to several major historical earthquakes all data used in the regressions are assigned individual uncertainties estimated from the literature or from experience formal confidence limits 68 per cent or 95 per cent on both the regression formulas and the predicted seismic moment values are then possible via error propagation analysis the most complete development is for the teleseismic magnitudes m and mb for both the final regression for log m is a quadratic formula that closely emulates the relationship between amplitude magnitudes and log m expected from dislocation theory and source scaling arguments regressions are also derived for the regional magnitudes mlg and m because there are many scr events mainly pre 1964 that have no teleseismic magnitudes prediction uncertainties from teleseismic magnitudes in moment magnitude units are in the ao 18 0 28 range and from regional magnitudes in the ko 23 0 38 range over a wide magnitude band finally the methodology developed here is generic even though the database is specific application to plate boundary oceanic intraplate or active continental intraplate regions should be straightforward

correlation of sandstones using heavy minerals an example from the statfjord formation of the snorre field northern north sea correlation of sandstones using heavy minerals is dependent on the recognition and quantification of provenance sensitive parameters suitable criteria include ratios of minerals that have similar hydraulic and diagenetic behaviour and properties of populations of individual mineral species sandstones of the statfjord formation in the snorre field display marked variations in their heavy mineral assemblages although hydraulic and diagenetic processes have played some part in generating these variations major changes in the nature of the source material can be detected on the basis of heavy mineral ratio and varietal data these changes in sand provenance can be used to produce a detailed stratigraphic breakdown of the sequence and to correlate from well to well eleven heavy mineral zones have been recognised on the basis of variations in monazite zircon garnet zircon and rutile zircon ratios on the incoming of chloritoid and on the composition of garnet populations the marked changes in provenance result from the proximity of the depositional location to the hinterland and it is considered unlikely that the detailed correlation made in the snorre field area applies to statfjord sandstones in other parts of the northern north sea however there is evidence for some degree of allogenic control on the heavy mineral variations and therefore some events may have regional significance

the geothermal potential of the underground of the salento peninsula southern italy the low enthalpy geothermal energy systems exploit the underground as a heat reservoir by coupling it with highly efficient heat pumps in winter the energy stored in the subsoil can be transferred to the surface to heat buildings whereas in summer the surplus heat in buildings can be transferred back to the ground providing a cooling action despite the high costs for installation low enthalpy geothermal systems have high energy efficiency and therefore contribute to energy saving to the use of renewable energy sources to environmental sustainability the effects on the hydrogeological cycle are often negligible and to the reduction in fuel consumption and in gas emissions in this paper a simple methodology is proposed to assess the geothermal potential of the underground of the salento peninsula southern italy at the regional scale by calculating the equivalent thermal performance of the subsoil which expresses the thermal power that is potentially extractable and useful to heat or cool a building since the possibility of exploiting the underground as a heat reservoir depends on the physical properties and water saturation of rocks previous detailed studies on the hydrostratigraphic setup of the region are the basis for this analysis of geothermal potential the equivalent thermal performance depends on the thermal efficiencies of different lithological units whose ranges of values for heating only are provided in literature for this case study a stochastic approach has been applied several combinations of thermal efficiencies were randomly selected from the intervals of reference values for every hydrostratigraphic formation and the corresponding minimum depths below the ground surface that must be reached to get the desired equivalent thermal performance are computed the results show that the underground of the salento peninsula has great potentialities for heating of buildings except for some coastal areas because the saltwater intrusion phenomenon could cause problems for the realization of low enthalpy geothermal energy systems

the seben kesenozu low temperature geothermal prospect nw turkey study of an advective geothermal system the kesenozu thermal springs are located in northwestern turkey about 10 km south of seben the springs emerge from a fracture zone created by strike slip faulting that strikes north northwest along the hamambogazi creek in northwestern anatolia the reservoir comprises a steeply dipping fracture zone and deep feeding aquifers hosted by limestones and conglomerates of the kesenozu formation eight springs and one shallow well discharge thermal water at a total rate of about 44 l s with temperatures between 42 and 78 c the waters are of neutral ph nahco3 type the meteoric origin of the spa waters is evident from their chemical and isotopic 18o 2h 3h compositions the thermal system is driven by deep reaching advective flows where rainwater becomes heated on descent and after deep paths ascend along fractures that act as hydrothermal conduits it can be described as an advective geothermal system silica chalcedony geothermometry indicates equilibrium temperatures between 89 and 94 c a recently drilled deep well encountered similar temperatures at about 2 km depth the minimum heating power potential direct use of the fracture zone reservoir is about 10 mwth

crustal structure across the xisha trough northwestern south china sea located at the northwestern part of the south china sea scs between the hainan and xisha paracel islands the xisha trough represents a failed rift in conjunction with the opening of the scs between 32 and 17 ma from west towards east within a scale of several hundred kilometers it presents all major stages of the rifting process and thus provides an ideal place to study the rifting process in great details in the autumn of 1996 a joint team of sino german scientists carried out a wide angle seismic experiment across the xisha trough with 10 ocean bottom hydrophones obh along a 237 km nnw sse oriented profile which was surveyed in 1987 with multi channel seismic mcs method by bgr of germany and soa of china favorable weather conditions and the powerful 4 x 12 1 air gun array rendered very good quality data with seismic signals observed at the offset of up to 110 km a detailed velocity depth model was obtained by using an interactive trial and error 2d ray tracing method interpretation of the nics data published by bgr provides very good geometrical constraints of the complex upper crustal structure which is characterized by fault blocks half horsts and half grabens filled with syn and post rift cenozoic sediments the velocity model in turn confirms the major structure outlined by the interpretation of the mcs data showing a varying sedimentary layer between i and 4 km of thickness and velocities between 1 7 and 4 5 km s the p wave velocity of 5 5 km s on the top of the crystalline basement is relatively low suggesting strong weathering within the crystalline crust the velocity increases downward continuously to 6 8 km s at the bottom of the crust without a clear differentiation in the middle crust showing clearly its continental nature even beneath the xisha trough the moho is marked by a sharp first order interface with a velocity of 8 0 8 1 km s at the uppermost mantle the moho depth is 15 km beneath the center of the trough and increases gradually to more than 25 kin towards north and south corresponding to an extreme thinning of the pre rift continental crust from more than 25 kin under the coast line to only 8 kin beneath the xisha trough the similar velocity structure of the continental nature on both sides of the xisha trough suggests a homogeneous pre rift continental setting the sharp moho and the lack of high velocity body hvb in the lower crust imply no magmatic underplating which is very different to interpretations across the eastern part of the continental margin in northern south china sea the intense faulting in the upper crust the strong but rather symmetrical crustal thinning centered at the xisha trough and the close neighborhood to the open scs nw subbasin suggest a pure shear rifting which failed most likely at the phase shortly before the continental breakup c 2001 elsevier science b v all rights reserved

the deep thermal field of the glueckstadt graben with this paper we assess the present day conductive thermal field of the glueckstadt graben in nw germany that is characterized by large salt walls and diapirs structuring the graben fill we use a finite element method to calculate the 3d steady state conductive thermal field based on a lithosphere scale 3d structural model that resolves the first order structural characteristics of the graben and its underlying lithosphere model predictions are validated against measured temperatures in six deep wells our investigations show that the interaction of thickness distributions and thermal rock properties of the different geological layers is of major importance for the distribution of temperatures in the deep subsurface of the glueckstadt graben however the local temperatures may result from the superposed effects of different controlling factors especially the upper sedimentary part of the model exhibits huge lateral temperature variations which correlate spatially with the shape of the thermally highly conductive permian salt layer variations in thickness and geometry of the salt cause two major effects which provoke considerable lateral temperature variations for a given depth 1 the chimney effect causes more efficient heat transport within salt diapirs as a consequence positive thermal anomalies develop in the upper part and above salt structures where the latter are covered by much less conductive sediments in contrast negative thermal anomalies are noticeable underneath salt structures 2 the thermal blanketing effect is caused by thermally low conductive sediments that provoke the local storage of heat where these insulating sediments are present the latter effect leads to both local and regional thermal anomalies locally this translates to higher temperatures where salt margin synclines are filled with thick insulating clastic sediments for the regional anomalies the cumulative insulating effects of the entire sediment fill results in a long wavelength variation of temperatures in response to heat refraction effects caused by the contrast between insulating sediments and highly conductive crystalline crust finally the longest wavelength of temperature variations is caused by the depth position of the isothermal lithosphere asthenosphere boundary defining the regional variations of the overall geothermal gradient we find that a conductive thermal model predicts observed temperatures reasonably well for five of the six available wells whereas the steady state conductive approach appears not to be valid for the sixth well

geomechanical and geochemical effects on sandstones caused by the reaction with supercritical co2 an experimental approach to in situ conditions in deep geological reservoirs the geochemical and geomechanical behaviour of reservoir rocks from deep saline aquifers during the injection and geological storage of co2 is studied in laboratory experiments a combination of geochemical and geomechanical studies was carried out on various sandstones from the north german basin after the mineralogical geochemical and petrophysical characterization a set of sandstone samples was exposed to supercritical sc co2 and brine for 2 4 weeks in an autoclave system one sample was mineralogically and geochemically characterised and then loaded in a triaxial cell under in situ pressure and temperature conditions to study the changes of the geomechanical rock properties after treatment in the autoclaves geochemical alterations mainly in the carbonate but also in the sheet silicate cements as well as in single minerals of the sandstones were observed affecting the rocks granular structure in addition to partial solution effects during the geochemical experiments small grains of secondary carbonate and other mineral precipitations were observed within the pore space of the treated sandstones results of additional geomechanical experiments with untreated samples show that the rock strength is influenced by the saturation degree the confining pressure the pore fluid pressure and temperature the exposure to pure scco2 in the autoclave system induces reduced strength parameters modified elastic deformation behaviour and changes of the effective porosity in comparison to untreated sandstone samples experimental results show that the volume of pore fluid fluxing into the pore space of the sandstones clearly depends on the saturation level of the sample

fluid dynamics driving saline water in the north east german basin in several areas of the north german basin saline water comes close to or even reaches the surface available data from wells indicate that brine stratification is under unstable conditions in the deeper underground in order to analyse the possible transport mechanisms 3d thermohaline simulations have been carried out for two different scenarios the 3d regional model 230 330 km indicates that salty water is driven to the surface by hydrostatical forces from the surrounding highlands in addition a smaller scale model 10 10 km has been constructed with a grid resolution accounting for possible convective flow the results indicate that convective flow may play a dominant role in areas with minor topography in summary the complex pattern of near surface occurrences of saline water probably results from the interaction of hydrostatic and thermal forces

subsurface thermal conductivity assessment in calabria southern italy a regional case study determining the suitability of a local area at a regional or local scale for the geothermal application of low enthalpy systems requires the knowledge of rock thermal conductivity values to evaluate the possibility of low enthalpy heat exchange a digital cartographic tool is also needed to synthesize the thermal properties of the underground this tool should be easily accessible and upgradeable and thus suitable for territorial planning and environmental control in order to address these key issues a methodological approach was developed within the framework of the national vigor project dedicated to evaluating the geothermal potential in southern italy in this paper the region of calabria was selected as a case study around 70 samples that were representative of the main geological formations were collected from all over the area thermal property tests were carried out both in dry and wet conditions using a thermal device in accordance with the modified transient plane source method the thermal conductivity values were then compared with data from the international literature in order to consider the influence of the entire stratigraphic sequence on the thermal conductivity parameters a geostatistical analysis of the available lithostratigraphic data was performed using the matlab toolbox modalstrata specially developed for this purpose a comprehensive geothermal subsurface characterization of calabria was thus obtained

thermoluminescence dating of the british coversand deposits abstract coversand deposits thought to be of lateglacial age are found in britain in north lincolnshire south west lancashire and central east anglia a comprehensive dating study of them using thermoluminescence tl techniques is currently underway in an attempt to link the british coversand deposits to the european coversand chronology initial results from four of the british coversand sites sampled are presented the 26 tl dates from 14 samples show that in lincolnshire aeolian deposition took place from 12 5 ka to i1 ka cessation of the initial sand deposition was synchronous with this in lancashire but sand deposition occurred significantly earlier in east anglia the upper layers of aeolian sand in lancashire are much younger and are attributed to holocene reworking on the basis of these dates lincolnshire and lancashire coversand deposition occurred at a similar time to the younger coversand ii whilst east anglian coversand deposition coincided with the younger coversand i phase in the european coversand chronology

elastic wave velocities chemistry and modal mineralogy of crustal rocks sampled by the outokumpu scientific drill hole evidence from lab measurements and modeling the outokumpu scientific deep drill hole intersects a 2500 m deep precambrian crustal section comprising a 1300 m thick biotite gneiss series mica schists at top followed by a 200 m thick meta ophiolite sequence underlain again by biotite gneisses mica schists 500 m thick with intercalations of amphibolite and meta pegmatoids pegmatitic granite from 2000 m downward the dominating rock types are meta pegmatoids pegmatitic granite average isotropic intrinsic p and s wave velocities and densities of rocks were calculated on the basis of the volume fraction of the constituent minerals and their single crystal properties for 29 core samples covering the depth range 198 2491 m the modal composition of the rocks is obtained from bulk rock xrf and mineral chemistry microprobe using least squares fitting laboratory seismic measurements on 13 selected samples representing the main lithologies revealed strong anisotropy of p and s wave velocities and shear wave splitting seismic anisotropy is strongly related to foliation and is in particular an important property of the biotite gneisses which dominate the upper and lower gneiss series at in situ conditions velocity anisotropy is largely caused by oriented microcracks which are not completely closed at the pressures corresponding to the relatively shallow depth drilled by the borehole in addition to crystallographic preferred orientation cpo of the phyllosilicates the contribution of cpo to bulk anisotropy is confirmed by 3d velocity calculations based on neutron diffraction texture measurements for vertical incidence of the wave train the in situ velocities derived from the lab measurements are significantly lower than the measured and calculated intrinsic velocities the experimental results give evidence that the strong reflective nature of the ophiolite derived rock assemblages is largely affected by oriented microcracks and preferred crystallographic orientation of major minerals in addition to the lithologic control c 2009 elsevier b v all rights reserved