seismic fluid detection a review abstract since the advent of seismic imaging techniques the dream of geophysicists has been to identify the fluid effect and be able to accurately map hydrocarbon from the brine within a target reservoir the usage of bright spots strong reflection amplitudes as an indicator of hydrocarbon was the earliest recognition of the direct role played by the pore fluids in seismic signatures further development of new techniques had a strong correlation with the increase in computing power and advances in seismic acquisition and processing techniques in this review we touch upon the relevant theory developed more than 100 years ago and then review the methods developed over five decades leading to the quantitative interpretation of seismic data for fluid detection we also carried out a case study to compare selected fluid identification methods applied to a complex reservoir within an oil and gas field in the barents sea the impedance based methods cpei curved pseudo elastic impedance and lmr lambda mu rho inversion provided better results compared to other techniques highlighting the critical influence anomalous lithologies have on such screening attributes

a general rule for synoptic eddy feedback onto low frequency flow in this study scale interaction between synoptic eddies and low frequency flow is investigated it is demonstrated here that there is a general rule the left hand rule that describes synoptic eddy feedback onto low frequency flow the rule is that low frequency anomalies systematically stir and deform the transient eddies in such a way that the irrotational eddy vorticity fluxes are directed preferentially about 90 toward the left hand side of the low frequency flow thus this eddy feedback plays a positive role in maintaining and prolonging low frequency flow under the stormy atmosphere similarly we show that the irrotational eddy temperature and moisture fluxes are also directed preferentially about 90 toward the left hand side of the low frequency flow in the northern hemisphere the eddy temperature fluxes and their vertical structure play a positive role in reinforcing the low frequency flow in the low levels the moisture fluxes play a role in enhancing low frequency flow by providing eddy induced moisture convergence and divergence

midlatitude atmospheric transient eddy feedbacks influenced enso associated wintertime pacific teleconnection patterns in two pdo phases the el nino southern oscillation enso associated wintertime atmospheric teleconnection patterns in two pacific decadal oscillation pdo phases are investigated using era 20c reanalysis data for 1950 2010 a strengthened enso associated pacific north american pna teleconnection pattern presents in pdo positive phase while a west pacific wp pattern over northwestern pacific and a squeezed pna pattern coexist when enso occurs in pdo negative phase the dynamical role of atmospheric transient eddy feedbacks to the teleconnection patterns are highlighted in the present study when enso occurs in pdo positive phase the uniform strengthened westerly jet anomalies downstream of the climatological main body of jet accompany with energetic transient eddy anomalies over northeastern pacific the transient eddy feedbacks largely enhance and favor the strengthened pna pattern when enso occurs in pdo negative phase the strengthened westerly jet anomalies appear to separate into two parts one locating north of the climatological main body of jet and the other at the downstream the accompanied transient eddy anomalies also split into two parts under such conditions the transient eddy feedbacks are limited over northeastern pacific and favor a weak pna pattern however the transient eddy anomalies over northwestern pacific strengthen and the feedbacks also strengthen and largely contribute to the wp pattern moreover the transient eddy anomalies over northwestern pacific seem to be anchored along the anomalously poleward strengthened oceanic subarctic frontal zone safz in pdo negative phase the enhanced atmospheric baroclinicity anomalies coupled with the strengthened safz energize atmospheric transient eddy anomalies and work as the potential maintenance in shaping the wp pattern

interannual and decadal modulations recently observed in the pacific storm track activity and east asian winter monsoon abstract interannual variability of the north pacific storm track observed over 17 recent winters is documented the local storm track activity is measured by a meridional flux of sensible heat associated with the lower tropospheric subweekly fluctuations the interannual variability in the heat flux over the northwestern nw pacific is found to be strongest in midwinter the first empirical orthogonal function of the interannual variability in midwinter captures the decadal tendency toward the enhanced storm track activity in midwinter over the nw pacific in association with the decadal weakening of the east asian winter monsoon siberian high and the aleutian low that occurred in the late 1980s the most marked signature of this enhancement is that the midwinter minimum in the storm track activity which had been apparent in the early to mid 1980s almost disappeared afterward as opposed to linear theory of baroclinic instability the enhanced activity occurred despite the weakening of the pacific j

lithology color coded seismic sections the calibration of avo crossplotting to rock properties in the late 1960s several oil companies noticed that in environments of young clastic sediments large seismic amplitudes were associated with gas saturated sands this method of correlating lithology to normal incidence ni reflectivities was appropriately named the bright spot technique however it quickly became apparent that not all large amplitudes were necessarily associated with gas reservoirs and much to our chagrin not all gas reservoirs had large amplitudes for the next decade geophysicists tried numerous techniques to resolve the ambiguity associated with lithologic identification by means of the seismic attribute ni this met with various degrees of success finally ostrander s work on amplitude variation with offset avo led to the development of another seismic attribute s which improved our discrimination of lithologies see plane wave reflection coefficients for gas sands at nonnormal angles of incidence geophysics 1984 but proper application of this new attribute along wit

simultaneous inversion of prestack seismic data for rock properties using simulated annealing a new prestack inversion algorithm has been developed to simultaneously estimate acoustic and shear impedances from p wave reflection seismic data the algorithm uses a global optimization procedure in the form of simulated annealing the goal of optimization is to find a global minimum of the objective function which includes the misfit between synthetic and observed prestack seismic data during the iterative inversion process the acoustic and shear impedance models are randomly perturbed and the synthetic seismic data are calculated and compared with the observed seismic data to increase stability constraints have been built into the inversion algorithm using the low frequency impedance and background vs vp models the inversion method has been successfully applied to synthetic and field data examples to produce acoustic and shear impedances comparable to log data of similar bandwidth the estimated acoustic and shear impedances can be combined to derive other elastic parameters which may be use

statistical rock physics combining rock physics information theory and geostatistics to reduce uncertainty in seismic reservoir characterization any physical theory is a kind of guesswork there are good guesses and bad guesses the language of probability allows us to speak quantitatively about some situation which may be highly variable but which does have some consistent average behavior our most precise description of nature must be in terms of probabilities richard feynman this paper presents snapshots of current and emerging trends in applied statistical rock physics for reservoir characterization by integrating fundamental concepts and models of rock physics statistical pattern recognition and information theory with seismic inversion and geostatistics we can quantify and reduce uncertainties in reservoir management rock physics allows us to link seismic response and reservoir properties and to extend the available data to generate training data for the classification system seismic imaging brings indirect but nevertheless spatially exhaustive lateral and vertical information about reservoir properties that are not available from pinpoint well data classification and estimation methods based on computational statistical techniques such as nonparametric bayesian classification bootstrap and neural networks help quantitatively measure interpretation uncertainty and the mis classification risk at each spatial location geostatistical stochastic simulations add spatial correlation and small scale variability which is hard to identify from seismic only because of the limits of resolution combining deterministic physical models with statistical techniques leads to new methods for interpretation and estimation of reservoir rock properties from seismic data these formulations identify the most likely interpretation the uncertainty of the interpretation and guide quantitative decision analysis subsurface heterogeneity delineation is a key factor in reliable reservoir characterization these heterogeneities occur at various scales and can include variations in lithology pore fluids clay content porosity pressure and temperature some methods used in seismic reservoir characterization are purely statistical others are deterministic based on physical models theoretical laboratory each group of techniques can have some

quasi stationary extratropical wave trains associated with distinct tropical pacific seasonal mean convection patterns observational and amip model results in this paper mechanisms for the formation of quasi stationary extratropical wave trains associated with four distinct winter patterns of seasonal mean tropical pacific convection anomalies including the western cp w cp pattern la nina ln pattern cp el nino cpen pattern and ep el nino epen pattern are investigated by utilizing observational and six atmospheric model intercomparison project phase 5 amip5 high skilled models access1 0 canam4 ccsm4 cmcc cm hadgem2 a mpi esm lr datasets the observational results show that tropical pacific forcing induces upper level anomalous rossby wave source that force vorticity over the central north pacific through modulating the local hadley circulation then excite eastward propagation of quasi stationary planetary waves penetrating into the north atlantic and finally establish the associated teleconnections in mid and high latitudes by local synoptic eddy mean flow interaction different structures of wave trains may be explained by evident differences in intensity and scale of the extratropical vorticity forcing originating from distinct convection anomalies over the tropical pacific the mme results further confirm the possible physical processes obtained from observations but there still exist some significant differences these cover the north pacific and north america and can possibly be attributed to the models simulation ability of extratropical vorticity forcing and local storm track intensity in addition the stratosphere troposphere interaction plays an important role for extratropical atmospheric circulation anomalies the stratospheric polar vortex not only modulates the underlying wave train especially for the north atlantic europe sector but is also affected by the upper tropospheric disturbance in high latitudes through the upward wave activity flux

a unified nonlinear multiscale interaction model of pacific north american teleconnection patterns abstractin this paper reanalysis data are first analyzed to reveal that the individual negative positive phase pacific north american pattern pna or pna pna has a lifetime of 10 20 days i

principles of avo crossplotting hydrocarbon related avo anomalies may show increasing or decreasing amplitude variation with offset conversely brine saturated background rocks may show increasing or decreasing avo

northern hemisphere winter circulation associated with the north atlantic oscillation and stratospheric polar night jet the interannual variability of the atmospheric winter circulation as characterized by the geopotential height at 500 hpa and temperature at 850 hpa associated with the north atlantic oscillation nao and stratospheric polar night jet pnj is examined it is suggested that the wintertime atmospheric circulation related to the nao index can be separated into two different modes of variability one is a regional mode characterized by a meridional dipole type pattern in the 500 hpa geopotential height anomaly field over the atlantic region the other having more zonal structure extends over wider region of the northern hemisphere this is also related to the lower stratospheric polar night jet air temperature near the surface over the eastern part of the eurasian continent is more closely correlated with the above mentioned hemispheric mode of variability than the regional nao

weighted stacking for rock property estimation and detection of gas amplitude versus offset concepts can be used to generate weighted stacking schemes here called geo stack which can be used in an otherwise standard seismic data processing sequence to display information about rock properties the zoeppritz equations can be simplified and several different approximations appear in the literature they describe the variation of p wave reflection coefficients with the angle of incidence of a p wave as a function of the p wave velocities the s wave velocities and the densities above and below an interface using a smooth representative interval velocity model from boreholes or velocity analyses and assuming no dip the angle of incidence can be found as a function of time and offset by iterative ray tracing in particular the angle of incidence can be computed for each sample in a normal moveout corrected cmp gather the approximated zoeppritz equation can then be fitted to the amplitudes of all the traces at each time sample of the gather and certain rock properties can be estimated the estimation of the rock properties is achieved by the application of time and offset variant weights to the data samples before stacking the properties which can be displayed by geo stack are p wave reflectivity or true zero offset reflectivity s wave reflectivity and the reflectivity of p wave velocity divided by s wave velocity or pseudo poisson s ratio reflectivity if assumptions are made about the relation between p wave velocity and s wave velocity for water bearing clastic silicate rocks then it is possible to create a display which highlights the presence of gas

scandinavian pattern and its climatic impact a lasg institute of atmospheric physics chinese academy of sciences beijing china b department of earth and planetary science university of tokyo tokyo japan maintenance mechanisms of the scandinavian teleconnection pattern and its possible impact on the eurasian climate are investigated on the basis of long term monthly data its upstream portion over the north atlantic is forced and maintained by feedback forcing from transient eddies migrating along the nearby storm track with an additional contribution from incoming rossby wave activity from further upstream the primary anomaly centre over the scandinavian peninsula and the downstream portion of the pattern manifest themselves basically as rossby waves propagating towards central siberia and east asia under the modest feedback forcing from transient eddies the pattern shows apparent seasonality in its dynamical properties including the wave train orientation and wavelength under the seasonally varying transient eddy feedback forcing and waveguide structure for rossby waves in cold seasons the positive phase of the pattern causes cold air accumulation over a vast area extending from western siberia to the regions around lake baikal and lake balkhash while giving rise to decreased precipitation over northeastern europe western siberia and some of the arctic coastal regions the pattern also changes the north atlantic sea surface temperature differently between autumn and winter

inverse rock physics modeling for reservoir quality prediction abstractseismic reservoir characterization requires a transform of seismically derived properties such as p and s wave velocities acoustic impedances elastic impedances or other seismic attributes into parameters describing lithology and reservoir conditions a large number of different rock physics models have been developed to obtain this link their relevance is however constrained by the type of lithology porosity range textural complexity saturation conditions and the dynamics of the pore fluid because the number of rock physics parameters is often higher than the number of seismic parameters this is known to be an underdetermined problem with nonunique solutions we have studied the framework of inverse rock physics modeling which aims at direct quantitative prediction of lithology and reservoir quality from seismic parameters but where nonuniqueness and data error propagation are also handled the procedure is based on a numerical reformulation of rock physics models so that the seismi

is the north atlantic oscillation a breaking wave abstract given the recent observational evidence that the positive negative phase of the north atlantic oscillation nao is the remnant of anticyclonic cyclonic wave breaking this study uses a multilevel primitive equation model to investigate important dynamical attributes of the above wave breaking behavior for this purpose a hierarchy of different basic states two and three dimensional and initial perturbations are used with the three dimensional climatological flow as the basic state it is found that initial perturbations located equatorward poleward and upstream of the climatological atlantic jet lead to wave breaking similar to that of the positive negative nao phase consistently analysis of observational data indeed shows that the pacific storm track is displaced equatorward poleward prior the onset of the positive negative nao phase this result suggests that the latitudinal position of the pacific storm track plays an important role for determining the phase of the nao sen

decadal covariability of the northern wintertime land surface temperature and atmospheric circulation abstractthe decadal covariability of northern wintertime land surface temperature and 500 hpa geopotential anomalies is examined using the national centers for environmental prediction national center for atmospheric research and the twentieth century reanalyses over the twentieth century and a 996 yr preindustrial climate simulation from the canadian earth system model based on the reanalysis data the covariability is dominated by two leading maximum covariance analysis mca modes mca1 is characterized by temperature anomalies over most of canada the eastern united states mexico and eurasian mid to high latitudes accompanied by anomalies of opposite sign elsewhere over northern landmasses mca2 features temperature anomalies over most of north america eurasia and greenland with opposite anomalies elsewhere in the upper troposphere the synoptic vorticity fluxes reinforce the anomalous circulation while in the lower troposphere advection by the anomalous mean flow offsets the eddy forcing and

wetland landscape dynamics swifterbant land use systems and the mesolithic neolithic transition in the southern north sea basin abstract over the last decade excavations in the lower scheldt river basin nw belgium have identified the first presence of the transitional mesolithic neolithic swifterbant culture previously only known from the netherlands and one site in northwest germany these excavations have also yielded the first evidence for the presence of early neolithic linearbandkeramik limbourg blicquy and epi rossen cultural remains in these wetland landscapes high quality organic preservation at these sites offered the opportunity to reliably place the swifterbant within the absolute chronology of the mesolithic neolithic transition in this region as well as the reconstruction of swifterbant subsistence practices most notably the incorporation of cattle husbandry into a traditional hunting fishing gathering economy two different site types could be identified between the six excavated sites dune and natural levee sites which had contemporaneous periods of occupation but different occupation histories the integration of the dates from these different site types with the palaeoenvironmental dates provides an initial model of the swifterbant settlement system in the area and its role in the specific tempo and trajectories of cultural and economic change that occurred during the neolithisation of the scheldt basin this model consists of relatively specialized and temporarily inhabited cattle and hunting fishing camps on the dunes and larger more continuously occupied levee camps along the river valleys bayesian statistical modeling suggests that swifterbant occupation of the dune sites occurred during a brackish water flooding period and that occupation of the levee sites was more continuous

rock physics diagnostic of north sea sands link between microstructure and seismic properties velocity in high porosity sands strongly depends on the position and amount of intergranular material velocity is high if the original grains are cemented at their contacts it is low if the pore filling material is placed away from the contacts the amount and type of intergranular material can be theoretically determined from velocity and porosity data by adjusting an effective medium theoretical model curve to a trend in the data and then assuming that the microstructure of the sediment is such as used in the model we apply this diagnostic method to clean sands in the heimdal formation the north sea the results show that the reservoir zone sand in one well under examination has slight contact cementation while it is completely uncemented and friable in another well this conclusion is supported by microscopic grain images the rock physics diagnostic is important for establishing a velocity porosity trend consistent with local geology such trends can improve the accuracy of porosity prediction from seismic data

geographical dependence of upper level blocking formation associated with intraseasonal amplification of the siberian high abstract intraseasonal amplification events of the surface siberian high in winter are generally associated with blocking ridge formation in the upper troposphere composite analysis applied to the 20 strongest intraseasonal events of upper level anticyclonic anomalies at every grid point over siberia reveals that the blocking formation differs fundamentally between the east and west of the climatological upper level trough over the far east to the west what can be called wave train atlantic origin type is common where a blocking ridge develops from anomalies as a component of a quasi stationary rossby wave train propagating across the eurasian continent under modest feedback forcing from transient eddies to the east of the trough what can be called pacific origin type dominates where a blocking ridge forms in association with westward development of anticyclonic anomalies from the north pacific under stronger feedback forcing from the pacific storm track regardless of a particular type of bl

thermally driven and eddy driven jet variability in reanalysis two important dynamical processes influence the extratropical zonal wind field angular momentum transport by the thermally direct hadley circulation thermal driving t and momentum flux convergence by atmospheric waves eddies that develop in regions of enhanced baroclinicity eddy driving e the relationship between extratropical zonal wind variability and these driving processes is investigated using 40 yr european centre for medium range weather forecasts re analysis era 40 data indices representing the processes it and ie are defined based on vertically integrated diabatic heating and meridional convergence of the meridionalflux of zonal momentum by eddies respectively zonal wind signatures associated with these indices are identified via composite analysis in the atlantic sector zonal wind variability is mainly associated with momentum flux convergence by baroclinic eddies supporting the established view that the atlanticjetis primarilyeddydriven inthe pacificsector zonal windvariability isassociatedwith bothdriving processes evidence that the pacific jet is both thermally driven and eddy driven the thermally driven pacific signature reflects changes in jet strength intensity and longitudinal extent with some resemblance to the zonal wind anomalies of the pacific north america pna pattern the eddy driven signature reflects a latitudinal shift of the jet exit region in both sectors that resembles the zonal wind anomalies of the north atlantic oscillation nao or west pacific wp patterns

seismic screening for hydrocarbon prospects using rock physics attributes rock physics templates rpt in combination with seis mic avo inversion data can be used to screen for hydrocar bon prospects during exploration with the improved quality and increased use of elastic seismic inversion there has re cently been a paradigm change in prospect mapping in the oil industry and quantitative interpretation has become a widely used jargon rock physics models are essential in that they help in converting elastic parameters from inversion data to reservoir parameters in the screening phase of inversion data rock physics models also can reveal hydrocarbon associated anomalies two new rock physics attributes help in detecting hydrocarbons from seismic the curved pseudo elastic im pedance and the trend angle the first of these is similar to the extended elastic impedance or the fluid factor in that it represents a deviation from a wet background trend in a rock physics template however it honors the nonlinear nature of a compaction trend the trend angle is a measure of slope angle between two adjacent data points in the ai versus v p v s crossplot and this attribute will highlight fluid trends in the data those two attributes can be used complementarily to detect and highlight hydrocarbon accumulations as demon strated on data from the norwegian shelf

comparison of avo indicators a modeling study a worldwide collection of 25 sets of velocity and density measurements from adjacent shales brine sands and gas sands was acquired with full waveform sonic dipole sonic and conventional well logging devices and or in the laboratory these data provide theoretical shale over brine sand and shale over gas sand p wave and s wave normal incidence reflection coefficients r p and r s avo intercepts a avo gradients b the avo indicators r p r s reflection coefficient difference and a b avo product the reflection coefficient difference is found to be a more universal indicator than the avo product in clastic stratigraphic intervals for shale over brine sand re flections the average r p r s tends to be near zero and relatively invariant with depth irrespective of gas sand impedance r p r s is always negative for shale over reservoir quality gas sand reflections and more negative than for the corresponding brine sand reflections in comparison the avo product may be positive near zero or negative for gas sands depend ing on the impedance contrast with the overlying shale these measurements also verify that r p r s is well approximated by a simple linear combination of a and b

impact of the winter north atlantic oscillation nao on the western pacific wp pattern in the following winter through arctic sea ice and enso part ii multi model evaluation of the nao enso linkage a 1 year lagged relationship between the north atlantic oscillation nao in winter and el nino southern oscillation enso in the following year was examined with a multi model ensemble analysis using coupled model intercomparison project phase 3 models a coherency index was developed as a measure of the coherence between the nao and enso in each model and used as a weighting factor in the ensemble model weighted multi model ensemble means of the regressed field on the maximum covariance analysis coefficients between the surface pressure field in the north atlantic nao field and the sea surface temperature field in the equatorial pacific enso field were explored the results indicated that when the wintertime nao was in its negative positive phase anomalous atmospheric circulation associated with a large small eurasian snow mass anomaly intensified weakened the asian cold surge and the westerly wind burst wwb in the warm pool region intensification of the wwb initiates el nino a sensitivity experiment using an idealized dry general circulation model revealed that the atmospheric response to anomalous near surface cooling associated with an anomalous eurasian snow mass induced higher surface pressure near the tibetan plateau and thus intensified the asian cold surge and wwb linear regression analyses applied to the reanalysis data strongly supported the model results our results therefore suggest an influence of the nao on the initiation of el nino via a process that involves eurasian snow anomalies associated with the nao phase

seismic attributes a historical perspective a seismic attribute is a quantitative measure of a seismic characteristic of interest analysis of attributes has been integral to reflection seismic interpretation since the 1930s when geophysicists started to pick traveltimes to coherent reflections on seismic field records there are now more than 50 distinct seismic attributes calculated from seismic data and applied to the interpretation of geologic structure stratigraphy and rock pore fluid properties the evolution of seismic attributes is closely linked to advances in computer technology as examples the advent of digital recording in the 1960s produced improved measurements of seismic amplitude and pointed out the correlation between hydrocarbon pore fluids and strong amplitudes bright spots the introduction of color printers in the early 1970s allowed color displays of reflection strength frequency phase and interval velocity to be overlain routinely on black and white seismic records interpretation workstations in the 1980s provided

intraseasonal variations of the british baikal corridor pattern abstractthe british baikal corridor bbc pattern is the dominant waveguide mode trapped along the summertime polar front jet over northern eurasia it consists of four geographically fixed centers

dynamical feedbacks and the persistence of the nao the persistence of the north atlantic oscillation nao is studied using observations of the threedimensional vorticity budget in the atlantic sector analysis of the relative vorticity tendency equation shows that convergence of eddy vorticity flux in the upper troposphere counteracts the effect of anomalous largescale divergence at the upper level at low levels the convergence associated with this large scale vertical circulation cell maintains the relative vorticity anomaly against frictional drag the eddy vorticity flux convergence thus acts to sustain the vorticity anomaly associated with the nao against drag and increases the persistence of the nao vorticity anomaly the adiabatic cooling associated with the rising motion in the vorticity maximum sustains the thermal structure of the nao anomaly enhancing the baroclinicity and thus eddy generation this constitutes a positive eddy feedback that helps maintain the nao the positive eddy feedback occurs only in the midlatitude region and is strongest during the negative phase of the nao when the atlantic jet is displaced toward the equator with a high pressure anomaly to the north and a low pressure anomaly to the south the stronger feedback demonstrated during the negative phase is consistent with the greater persistence observed for this phase of the nao the positive feedback appears to be associated with anomalous northward eddy propagation away from the jet

impacts of small scale faults on continental to coastal plain deposition evidence from the realgrunnen subgroup in the goliat field southwest barents sea norway abstract in this study we synthesise sedimentological fault and amplitude versus angle ava analysis and propose that the fruholmen and tubaen formations realgrunnen subgroup are syn kinematic deposits that record a previously undocumented early phase of mesozoic rifting on the troms finnmark fault complex and within the hammerfest basin the realgrunnen subgroup hosts one of two triassic reservoirs currently being produced in the goliat field here the subgroup sits unconformably on top of the storfjorden subgroup carnian snadd formation away from the goliat field which is characterised by a periclinal anticline the realgrunnen subgroup also comprises the lower middle jurassic nordmela and sto formations sedimentological analysis of six exploration wells reveals that the fruholmen formation was deposited in a prodelta to delta plain environment where tide influenced and fluvial dominated distributary channels are represented by clay siltstones and very fine grained sandstones the overlying tubaen formation is characterised by medium to very coarse grained deposits locally conglomeratic and represents a widespread braid plain with localised alluvial fans displacement profiles of faults and along fault thickness variations demonstrate that an immature fault system was active during deposition of the realgrunnen subgroup a series of unconnected fault segments hosted isolated sub basins and erosional catchment areas in their hanging and footwalls respectively an ava attribute map generated from a 10 ms interval of the uppermost part of the subgroup reveals gross sand prone depositional bodies i e individual and amalgamated channels some of which show meandering geometries ox bow lakes and alluvial fans sand bodies frequently show elongate geometries parallel to faults indicative of syn depositional fault related subsidence driving mechanisms responsible for the norian to rhaetian event may relate to contemporaneous rejuvenation of the fennoscandian hinterland development of the novaya zemlya fold and thrust belt and or the early cimmerian tectonic phase in northern europe

anatomy of synoptic eddy nao interaction through eddy structure decomposition abstracta method of eddy structure decomposition is proposed to detect how low frequency flow associated with the north atlantic oscillation nao organizes systematically synoptic eddy se activity to generate in phase and upstream feedbacks in this method a statistical eddy streamfunction ses field defined by the three point covariance of synoptic scale streamfunction is introduced to characterize spatiotemporal se flow structures the ses field is decomposed into basic and anomalous parts to represent the climatological se flow structure and its departure these two parts are used to calculate the basic and anomalous eddy velocity eddy vorticity and thus eddy vorticity flux fields in order to elucidate those two se feedbacks onto the nao this method is validated by the fact that the observed anomalous eddy vorticity flux field can be reproduced well by two linear terms the basic eddy velocity field multiplied by anomalous eddy vorticity field and the anomalous eddy velocity field multiplied

interdecadal variability of the enso north atlantic oscillation connection in boreal summer understanding the combined effect of el nino southern oscillation enso and the north atlantic oscillation nao is of great importance for climate seasonal prediction extreme climate events in particular results in this study show that during the last hundred years 1900 to present the enso nao connection experiences a notable interdecadal change in summer june august according to a 21 year sliding correlation between them namely from no significant correlation uncoupling before the mid 1970s to a significant correlation coupling after the mid 1970s comparison analysis between the coupling epoch 1977 1997 and the uncoupling epoch 1958 1976 shows that the most pronounced circulation anomalies take place over the extratropical north pacific further analysis and numerical experiments suggest that a poleward propagating rossby wave train possibly enhanced by sea surface temperature anomalies in the extratropical north pacific associated with the developing phases of enso during the later epoch is responsible for connecting the enso signal with the nao 2012 crown in the right of canada published by johnwiley sons ltd

dynamics of synoptic eddy and low frequency flow interaction part iii baroclinic model results abstract in this three part study a linear closure has been developed for the synoptic eddy and low frequency flow self interaction and demonstrated that internal dynamics plays an important role in generating the leading low frequency modes in the extratropical circulation anomalies during cold seasons in part iii a new linearized primitive equation system is first derived for time mean flow anomalies the dynamical operator of the system includes a traditional part depending on the observed climatological mean state and an additional part from the self feedback closure utilizing the observed climatological properties of synoptic eddy activity the latter part relates nonlocally all the anomalous eddy forcing terms in equations of momentum temperature and surface pressure to the time mean flow anomalies using the observational data the closure was validated with reasonable success and it was found that terms of the self feedback in the momentum and pressure equations tend to reinforce the low f

interdecadal changes in the relationship between interannual variations of spring north atlantic sst and eurasian surface air temperature abstractthis study investigates interdecadal changes in the relationship between interannual variations of boreal spring sea surface temperature sst in the north atlantic and surface air temperature sat over the mid to high latitudes of eurasia during 1948 2014 analyses show that the connection between the spring north atlantic tripole sst anomaly pattern and the eurasian sat anomalies has experienced marked interdecadal shifts around the early 1970s and mid 1990s the connection is strong during 1954 72 and 1996 2014 but weak during 1973 91 a diagnosis indicates that interdecadal changes in the connection between the north atlantic sst and eurasian sat variations are associated with changes in atmospheric circulation anomalies over eurasia induced by the north atlantic tripole sst anomaly pattern further analyses suggest that changes in atmospheric circulation anomalies over eurasia are related to changes in the position of atmospheric heating anomalies over the north atlantic which may be due to

dynamics of synoptic eddy and low frequency flow interaction part ii a theory for low frequency modes abstract amidst stormy atmospheric circulation there are prominent recurrent patterns of variability in the planetary circulation such as the antarctic oscillation aao arctic oscillation ao or north atlantic oscillation nao and the pacific north america pna pattern the role of the synoptic eddy and low frequency flow self feedback in the formation of these dominant low frequency modes is investigated in this paper using the linear barotropic model with the self feedback proposed in part i it is found that the ao like and aao like leading singular modes of the linear dynamical system emerge from the stormy background flow as the result of a positive self feedback this self feedback also prefers a pna like singular vector as well among other modes under the climatological conditions of northern winters a model with idealized conditions of basic mean flow and activity of synoptic eddy flow and a prototype model are also used to illustrate that there is a natural scale selection for the aao

energetics of the western hemisphere circulation pattern abstractthe western hemisphere wh circulation pattern identified by self organizing maps cluster analysis is a low frequency atmospheric regime that influences the fluctuations of large scale c

left hand rule for synoptic eddy feedback on low frequency flow 1 in this study scale interaction between synoptic eddies and low frequency flow is investigated the synoptic eddy feedback is a key process in sustaining the low frequency flow we show clear evidence using ncep reanalysis data that there is a general underlying rule the left hand rule governing the synoptic eddy feedback onto low frequency flow this rule states that eddy vorticity fluxes are directed preferentially about 90 degrees toward their left hand side so that they converge into cyclonic flow and diverge from anticyclonic flow therefore the eddy vorticity flux plays a positive role in reinforcing low frequency flow citation kug j s and f f jin 2009 left hand rule for synoptic eddy feedback on low frequency flow geophys res lett 36 l05709 doi 10 1029 2008gl036435

variability of the baroclinic and barotropic transient eddy forcing associated with monthly changes in the midlatitude storm tracks abstract the heat and vorticity transports by synoptic scale eddies at various levels between 1000 and 100 mb have been compiled for each winter month of the 1966 84 period using time filtered daily analyses produced by the u s national meteorological center these circulation statistics were used to compute the three dimensional distributions of the quasigeostrophic geopotential tendency and vertical motion induced by baroclinic and barotropic eddy processes in individual months the latter fields serve as the basis for describing the synoptic scale eddy forcing associated with the leading modes of month to month variability of the storm tracks over the north pacific and north atlantic these modes are associated with the meridional displacements of the storm track axes from their climatological positions the placement of a storm track at a certain latitude in a certain month is accompanied by enhanced convergence of eddy heat fluxes poleward of in the tropospheric column poleward of the storm tra

detection of gas in sandstone reservoirs using avo analysis a 3 d seismic case history using the geostack technique the geostack technique is a method of analyzing seismic amplitude variation with offset avo information one of the outputs of the analysis is a set of direct hydrocarbon indicator traces called fluid factor traces the fluid factor trace is designed to be low amplitude for all reflectors in a clastic sedimentary sequence except for rocks that lie off the mudrock line the mudrock line is the line on a crossplot of p wave velocity against s wave velocity on which water saturated sandstones shales and siltstones lie some of the rock types that lie off the mudrock line are gas saturated sandstones carbonates and igneous rocks in the absence of carbonates and igneous rocks high amplitude reflections on fluid factor traces would be expected to represent gas saturated sandstones of course this relationship does not apply exactly in nature and the extent to which the mudrock line model applies varies from area to area however it is a useful model in many basins of the world including the one

relationships between compressional wave and shear wave velocities in clastic silicate rocks new velocity data in addition to literature data derived from sonic log seismic and laboratory measurements are analyzed for clastic silicate rocks these data demonstrate simple systematic relationships between compressional and shear wave velocities for water saturated clastic silicate rocks shear wave veloci ty is approximately linearly related to compressional wave velocity and the compressional to shear velocity ratio decreases with increasing compressional velocity laboratory data for dry sandstones indicate a nearly constant compressional to shear velocity ratio with rigidity approximately equal to bulk modulus ideal models for regular packings of spheres and cracked solids exhibit behavior similar to the observed water saturated and dry trends for dry rigidity equal to dry bulk modulus gassmann s equations predict velocities in close agreement with data from the water saturated

dynamics of synoptic eddy and low frequency flow interaction part i a linear closure abstract the interaction between synoptic eddy and low frequency flow self has been recognized for decades to play an important role in the dynamics of the low frequency variability of the atmospheric circulation in this three part study a linear framework with a stochastic basic flow capturing both the climatological mean flow and climatological measures of the synoptic eddy flow is proposed based on this linear framework a set of linear dynamic equations is derived for the ensemble mean eddy forcing that is generated by anomalous time mean flows by assuming that such dynamically determined eddy forcing anomalies approximately represent the time mean anomalies of the synoptic eddy forcing and by using a quasi equilibrium approximation an analytical nonlocal dynamical closure is obtained for the two way self feedback this linear closure directly relating time mean anomalies of the synoptic eddy forcing to the anomalous time mean flow becomes an internal part of a new linear dynamic system for an

rock physics diagnostics of depositional texture diagenetic alterations and reservoir heterogeneity in high porosity siliciclastic sediments and rocks a review of selected models and suggested work flows rock physics has evolved to become a key tool of reservoir geophysics and an integral part of quantitative seismic interpretation rock physics models adapted to site specific deposition and compaction help extrapolate rock properties away from existing wells and by so doing facilitate early exploration and appraisal many rock physics models are available each having benefits and limitations during early exploration or in frontier areas direct use of empirical site specific models may not help because such models have been created for areas with possibly different geologic settings at the same time more advanced physics based models can be too uncertain because of poor constraints on the input parameters without well or laboratory data to adjust these parameters a hybrid modeling approach has been applied to siliciclastic unconsolidated to moderately consolidated sediments specifically in sandstones a physical contact theory such as the hertz mindlin model combined with theoretical elastic bounds such as the hashin shtrikman bounds mimics the elastic signatures of porosity reduction associated with depositional sorting and diagenesis including mechanical and chemical compaction for soft shales the seismic properties are quantified as a function of pore shape and occurrence of cracklike porosity with low aspect ratios a work flow for upscaling interbedded sands and shales using backus averaging follows the hybrid modeling of individual homogenous sand and shale layers different models can be included in site specific rock physics templates and used for quantitative interpretation of lithology porosity and pore fluids from well log and seismic data

dynamics of the extratropical response to a tropical atlantic sst anomaly abstract previous atmospheric general circulation model agcm experiments revealed that atmospheric responses to a tropical atlantic sea surface temperature anomaly ssta were asymmetric with respect to the sign of the ssta a positive ssta produced a south north dipole in geopotential heights much like the north atlantic oscillation nao while a negative ssta yielded an eastward propagating wave train with the northern lobe of the nao absent here these height responses are decomposed into components that are symmetric or antisymmetric with respect to the sign of the ssta the symmetric or notionally linear component is a nearly south north dipole projecting on the nao while the antisymmetric or notionally nonlinear component is a different dipole experiments with a diagnostic linear baroclinic model lbm suggest that both components are maintained primarily by transient eddy forcing dynamical mechanisms for the formation of the two components are explored using the lbm and a nonlinear baro

seismic reservoir and source rock analysis using inverse rock physics modeling a norwegian sea demonstration abstract identifying type of rocks and fluids from seismic amplitude anomalies can be challenging because of seismic nonuniqueness and rock physics ambiguities lithology and fluid predictions based on seismic properties therefore are often associated with uncertainties on the norwegian shelf clay rich source rocks and hydrocarbon filled sandstones often show similar avo responses a seismic screening method based on rock physics enables one to better discriminate between these different facies this technique is demonstrated on seismic avo data i e acoustic impedance ai and vp vs from the norwegian sea rock physics models for organic rich shales and gas sandstones are calibrated using nearby well data then these models are used for predictions of rock parameters away from well locations from these predictions the likelihood of presence of organic rich shales versus gas sandstones can be evaluated based on a rock physics approach however there are many uncertainties in the accuracy of the c

a comparison between methods that discriminate fluid content in unconsolidated sandstone reservoirs three seismic attributes commonly used to predict pore fluid and lithology are the fluid factor f poisson impedance pi and lambda rho we evaluated the pore fluid sensitivity of these attributes with both well log and seismic data in tertiary unconsolidated sediments from the gulf of mexico where sand and shale are the only expected lithologies while the sensitivity of one attribute versus another to discriminate pore fluid is often debated in the literature the sensitivities of the three attributes are not independent but can be traced back to the fluid factor which is a function of the p and s wave normal incident reflection coefficients interestingly the fluid factor which is a reflectivity attribute at the top of a hydrocarbon saturated reservoir is basically independent of the shale properties above the reservoir it is a function of the brine and hydrocarbon impedances of the reservoir the next attribute poisson impedance is thenequal to the fluid factor times the sum o

amplitude versus offset variations in gas sands seismic reflections from gas sands exhibit a wide range of amplitude versus offset avo characteristics the two factors that most strongly determine the avo behavior of a gas sand reflection are the normal incidence reflection coefficient r0 and the contrast in poisson s ratio at the reflector of these two factors r0 is the least constrained based on their avo characteristics gas sand reflectors can be grouped into three classes defined in terms of r0 at the top of the gas sand class 1 gas sands have higher impedance than the encasing shale with relatively large positive values for r0 class 2 gas sands have nearly the same impedance as the encasing shale and are characterized by values of r0 near zero class 3 sands have lower impedance than the encasing shale with negative large magnitude values for r0 each of these sand classes has a distinct avo characteristic an example of a gas sand from each of the three classes is presented in the paper the class 1 example involves a hartshorn channel s