stochastic inversion of seismic pp and ps data for reservoir parameter estimation we have investigated the value of isotropic seismic converted wave i e ps data for reservoir parameter estimation using stochastic approaches based on a floating grain rockphysics model we first performed statistical analysis on a simple two layer model built on actual borehole logs and compared the relative value of ps data versus amplitudevariation with offset avo gradient data for estimating the floating grain fraction we found that ps data were significantly more informative than avo gradient data in terms of likelihood functions and the combination of ps and avo gradient data together with pp data provided the maximal value for the reservoir parameter estimation to evaluate the value of ps data under complex situations we developed a hierarchical bayesian model to combine seismic pp and ps data and their associated time registration we extended a model based bayesian method developed previously for inverting seismic pp data only by including ps responses and time registration as additional data and ps traveltime and reflectivity as additional variables we applied the method to a synthetic six layer model that closely mimics real field scenarios we foundthatpsdataprovidedmoreinformationthan avo gradient data for estimating the floating grain fraction porosity net to gross and layer thicknesses when their corresponding priors were weak

joint inversion of pp and ps reflection data for vti media a north sea case study despite the significant advantages of combining pp and ps reflection data in anisotropic parameter estimation application of this approach has been hindered by the inherent complexity of ps wave moveout to overcome this problem v grechka and i tsvankin suggested a model independent procedure to construct the traveltimes of pure ss wave reflections from pp and ps data here we apply their method and anisotropic multicomponent stacking velocity tomography to a 2 d line acquired over the lower tertiary siri reservoir in the north sea the computed traveltimes of ss reflections from several horizons are used to estimate the effective ss wave normal moveout nmo velocities which are combined with the nmo velocities of pp waves in the tomographic velocity analysis comparison of the vertical and nmo velocities of the pp and ss waves provides clear evidence of anisotropy in the section above the reservoir the interval parameter estimation is performed under the assumption that the section is composed of

prediction of coal seam details and mining safety using multicomponent seismic data a case history from china abstractwith the increasing mining depth of coal mines geologic hazards have become the main source of accidents for this reason coal seam prediction requires more assessment parameters such as the degree of anisotropy vp vs value and elastic modulus these parameters are difficult to determine using only the pp wave we have inverted and interpreted multicomponent seismic data acquired from a 2 56 km2 area in the guqiao mine located on the southern margin of the north china plate under the constraints of drill log and rock physics test data the production coal seam 11 2 of the mine located in the permian formation was our focus of this study and our objective was to determine the structure fracture development thickness surrounding rock lithology roof stability and mining safety of the seam to achieve this we first performed an analysis of s wave splitting and joint pp and ps wave inversions the inversion results were then combined to derive additional parameters such as the vp vs

joint pp and ps seismic inversion we present a case history of joint inversion of pp and ps reflection seismic data using a weighted stacking technique our example comes from blackfoot field owned and operated by pancanadian petroleum in southeastern alberta canada the exploration target at blackfoot is a lower cretaceous channel system approximately 1 4 km deep figure 1 figure 1 the glauconitic channel system at blackfoot oil field alberta is a sequence of sand and shale filled valleys incised into lower cretaceous and mississippian carbonates the blackfoot interpretation has an upper and lower channel that are prospective and separated by a nonporous lithic channel these glauconitic channels with sand or shale fill are found throughout the region and as there were many episodes of channel formation can be stacked on top of one another at blackfoot the channel interval is about 40 m thick and 100 m wide there tends to be good porosity in an upper channel and a lower channel that are separated by a tight lithic channel the upper channel where present is usually gas prone while the lower channel is generally oil prone when the pore fluid in the channel sands is a compressible hydrocarbon instead of incompressible water the bulk compressibility is reduced and this modifies the signature of seismic reflection data because pressure waves and shear waves sense different rock and pore fluid properties joint use of pp and ps data can provide superior lithologic discrimination the conversion of one elastic wave either p or s into another upon reflection or transmission at an interface is described by the zoeppritz equations these equations are algebraically quite complex and it is not practical to reproduce them here instead we will present useful concepts and approximate forms we invite the reader to visit our web site http www crewes org and interactively examine the equations using our

geochemistry and origin of archaean quartz cordierite gneisses from the godthabsfjord region west greenland we report new data on the major minor and trace element compositions of metasedimentary quartzcordierite gneisses qcg an important member of the archaean malene supracrustal suite found throughout the godthabsfjord region of west greenland the analyzed qcg contain assemblages of quartz cordierite biotite garnet anthophyllite gedrite staurolite sillimanite plagioclase with abundant accessory zircon and minor rutile monazite and allanite and broadly resemble cordierite orthoamphibole rocks found in a great number of other metamorphic terrains chemically the qcg are characterized by 1 high but variable sio2 59 87 wt relative enrichments in mgo feo and al2o3 mg 0 35 0 85 and depletions in na2o k2o and especially cao 2 low concentrations of sc cr co ni and sr 3 high concentrations of y nb zr hf ta th u and ree rare earth elements with prominent negative eu anomalies in each case 5 high concentrations of ga 18 55 ppm with variable ga al ratios that are significantly higher than average crustal material low cr and ni together with enriched and fractionated ree displaying negative eu anomalies distinguish the malene qcg from published accounts of most other archaean sedimentary rocks furthermore all of the above mentioned trace element characteristics distinguish the qcg from ordinary malene clastic metasediments quartzites psammites and pelites suggesting a separate origin for the qcg these data point towards chemically evolved felsic igneous rocks being the source of the qcg consequently we propose that the malene qcg represent metamorphosed felsic volcaniclastic sediments that underwent hydrothermal alteration by heated seawater prior to metamorphism which resulted in gain of mg and fe loss of alkalis and lime and possibly eu and sr the overall trace element characteristics of the qcg elevated ga zr nb ree etc are features shared by a type granites and their volcanic equivalents such igneous rocks may represent the ultimate source material for the qcg protolith

boundary layer mechanisms in extratropical cyclones this paper revisits the mechanism for the interaction of the boundary layer with extratropical cyclones two diagnostic approaches are compared ekman pumping and potential vorticity ekman pumping derives from the boundary layer stress which induces convergence and ascent boundary layer potential vorticity contains in a single quantity both the vorticity and stratification these quantities are compared for an idealized extratropical cyclone life cycle simulated with the met office unified model a significant component of the boundary layer stress and thus ekman pumping at occlusion is forced by the cold conveyor belt jet in the unstable boundary layer in contrast much of the boundary layer depth averaged potential vorticity is contained within the stable warm sector region inversion of the warm sector pv indicates a small local deepening of about 2 5 hpa moreover switching off the boundary layer mixing in the unstable cold sector has much more impact than in the stable warm sector the sensitivity of the cyclone and its boundary layer to basic state jet strength is then investigated the maximum friction velocity scales closely with the initial maximum jet strength this demonstrates the important role of the large scale flow in organizing the boundary layer structure changes in the minimum pressure produced by altering the boundary layer parametrization correspond closely to changes in the surface stress averaged over the cyclone different operational changes to the boundary layer scheme produce small and compensating changes to the cyclone minimum pressure over three days crown copyright 2007 reproduced with the permission of the controller of hmso published by john wiley sons ltd

shear wave velocity and density estimation from ps wave avo analysis application to an obs dataset from the north sea s wave velocity and density information is crucial for hydrocarbon detection because they help in the discrimination of pore filling fluids unfortunately these two parameters cannot be accurately resolved from conventional p wave marine data recent developments in ocean bottom seismic obs technology make it possible to acquire high quality s wave data in marine environments the use of s waves for amplitude variation with offset avo analysis can give better estimates of s wave velocity and density contrasts like p wave avo s wave avo is sensitive to various types of noise we investigate numerically and analytically the sensitivity of avo inversion to random noise and errors in angles of incidence synthetic examples show that random noise and angle errors can strongly bias the parameter estimation the use of singular value decomposition offers a simple stabilization scheme to solve for the elastic parameters the avo inversion is applied to an obs data set from the north sea special prestac

a new boundary layer mixing scheme part i scheme description and single column model tests a new boundary layer turbulent mixing scheme has been developed for use in the ukmo weather forecasting and climate prediction models this includes a representation of nonlocal mixing driven by both surface fluxes and cloud top processes in unstable layers either coupled to or decoupled from the surface and an explicit entrainment parameterization the scheme is formulated in moist conserved variables so that it can treat both dry and cloudy layers details of the scheme and examples of its performance in single column model tests are presented

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

joint pp and ps ava seismic inversion using exact zoeppritz equations the zoeppritz equations describe the relationship between seismic properties that are useful for the interpretation of lithology and fluid properties various approximations to the zoeppritz equations are often used in linear amplitude variation with offset and amplitude variation with angle inversions assuming lowcontrast boundaries these approximations restrict the inversion method to not too large angle cases and reduce the inversion accuracy therefore it is necessary to develop joint pp and ps prestack inversion methods using the exact zoeppritz equations we have developed a method for nonlinear joint prestack inversion using the exact zoeppritz equations we established an objective function to combine pp and ps information based on a least squares approach and weusedthetaylorexpansionmethod to derive a model updating formula for the inversion we also used a mean shift method to improve the accuracy of inversion results we validated our inversion using synthetic and field seismic data the model for calculating synthetic data contained high contrast interfaces to match the reservoir layers which included for example coal seams and unconsolidated sandstone the outputs of the inversion were the elastic parameters p and s wave velocities as well as density rather than the changes in elastic parameters we found that the nonlinear joint prestack inversion achieved more accurate results than the linear joint prestack inversion regardless of incidence angle size furthermore if the prestack data were of high enough quality it was possible to identify thin layers from the inversion result

a semi geostrophic model incorporating well mixed boundary layers semi geostrophic theory has proved a powerful framework for understanding the dynamics of mid latitude weather systems however one limitation is the lack of a realistic boundary layer representation semi geostrophic theory can be modified to include an atmospheric boundary layer by replacing the geostrophic wind with the geotriptic or ekman balanced value in the substantive derivative and appropriately approximating the momentum diffusion term the so called semi geotriptic theory however until now solutions of the semi geotriptic equations using predictor corrector methods have not been possible for the important case of well mixed boundary layers existing predictor corrector methods require a brunt vaisala frequency greater than zero to be solvable here we describe a method of incorporating well mixed boundary layers into semi geotriptic theory we modify the hydrostatic relationship by including a small horizontal diffusion of vertical velocity this enables the formation of a well posed predictor corrector method given well mixed boundary layers are a ubiquitous feature of the lower atmosphere the modification increases the usability of the model calculations are also performed at much higher vertical resolution than before the revised semi geotriptic model is compared with a hydrostatic primitive equation model for a test case of a two dimensional idealized diurnal cycle of a sea breeze the performance of the revised semi geotriptic model in the growth phase of the sea breeze is improved as a well mixed boundary layer is now permitted the additional vertical resolution captures the capping inversion and the sea breeze circulation better the hydrostatic primitive equation model is shown to produce inertial oscillations that persist beyond the evening decay of the boundary layer until the following morning in contrast the semi geotriptic model decays following the boundary layer state in a more realistic way the semi geotriptic model thus demonstrates its usefulness as a critical tool in understanding boundary layer dynamics coupling issues in operational models copyright 2010 royal meteorological society and crown copyright

simulation of the observed evening transition and nocturnal boundary layers large eddy simulation large eddy simulations are performed of two observed cases of evening transition boundary layers over land although generally similar to the observations the simulations have a poor match to the ageostrophic wind above the boundary layer and overestimate the nocturnal 4 m wind speed for one case the nocturnal phase is also simulated using a close match to observations in the early evening reproducing well the early morning boundary layer and jet this is achieved with a moderate resolution 5 m and also demonstrates the importance of a good initial wind state in a numerical weather prediction context these findings motivate improved wind profile observations around transition and a better representation of the ageostrophic wind by the boundary layer parametrization copyright 2006 crown copyright

on the incorporation of atmospheric boundary layer effects into a balanced model a method of coupling the thermal and frictional forcing in the atmospheric boundary layer to a semi geostrophic model of the internal dynamics is developed it is illustrated by two dimensional sea breeze simulations which are compared with those of a two dimensional primitive equation model it is demonstrated that the main features of the circulation on a horizontal scale larger than 20 km can be simulated with the semi geostrophic model but the detailed local circulations cannot

shear wave elastic impedance it is well known that if we are able to estimate acoustic impedance ai and a parameter related to shear wave velocity from seismic data our ability to discriminate between different lithologies and fluid phases will increase prestack inversion on individual cdp gathers and inverting directly for vp vs and density have been tested in several ways but the estimated parameters are often poorly determined a more robust approach is to apply poststack inversion on partial stacks for inversion of the near offset stack ai can be calculated directly from well logs however for the far offset stack we need to derive an equivalent of the acoustic impedance that can be used to calibrate the non zero offset seismic reflectivity connolly 1998 1999 derived such an equivalent elastic impedance ei and demonstrated how by using elastic impedance logs which requires shear wave logs he was able to perform well calibration and inversion of far offset data this article describes a new function shear wave elastic impedance sei for linking converted wave stacks to wells using a linearization of the zoeppritz equations sei is similar to ei but adapted to p s converted seismic data it can be computed from acoustic log data p and s wave velocities and density and used for well calibration wavelet estimation and inversion of p s reflectivity data leading to improved interpretability of converted wave data equation 4 in appendix 1 is the key mathematical formula in this approach to sei to test the sei technique we used a 3 d four component 4 c ocean bottom cable obc survey acquired in 1997 that covers approximately 10 km2 of the statfjord field rogno et al 1999 both p wave and converted wave data were 3 d prestack time migrated the hydrophone p and the vertical geophone z component were summed to attenuate receiver side water layer reverberations and both data sets pz

archean chemical weathering at three localities on the canadian shield abstract sapropelite developed on a granodiorite basement below the archean steeprock group in the western superior structural province of canada weathered materials from a 3 15 ga granitic basement to the archean yellowknife supergroup in the slave structural province and weathered detritus from contemporaneous komatiites and gneissic basement of the archean prince albert group in northern churchill structural province have been analysed the deviation of the weakly metamorphosed weathered material from the chemical composition of their precursors is comparable to that seen in more recent weathered profiles from similar source materials this includes the enhancement of ferric to ferrous iron ratios and potash to soda lime and magnesia ratios there is also an increase in lighter ree and a depletion of heavier ree quartz rich sediments immediately above the unconformity derived from the basement granitoids may be enriched in aluminum and iron and yield chloritoid under proper metamorphic conditions sediments formed from mixed sources such as weathered gneissic basement and contemporaneous komatiitic volcanics yield anomalous resistate sedimentary mixtures such as chromiferous quartzites based on the data given here there is no need to postulate that different weathering and or ground water systems were operative during the archean compared to more recent times on the other hand the complicated weathering and diagenetic history that altered material undergoes below a subsiding unconformity relies as much or more on the buffering capacity of the enclosed rock mass as on the atmospheric conditions prevalent at the time of weathering hence weathering profiles old and new are more a response to local environmental conditions within the rock than the composition of the atmosphere

atmospheric response to a midlatitude sst front alongfront winds abstractsatellite observations and modeling studies show that midlatitude sst fronts influence the marine atmospheric boundary layer mabl and atmospheric circulation here the weather research and forecasting wrf mesoscale model is used to explore the atmospheric response to a midlatitude sst front in an idealized dry two dimensional configuration with a background wind oriented in the alongfront direction the sst front excites an alongfront wind anomaly in the free atmosphere with peak intensity just above the mabl this response is nearly quasigeostrophic in contrast to the inertia gravity wave response seen for cross front background winds the free atmosphere response increases with the background wind in contrast to previously proposed sst frontal mabl models the mabl winds are nearly in ekman balance however a cross front wind develops in the mabl as a result of friction and rotation such that the mabl cross front rossby number e 0 2 the mabl vorticity balance and scaling arguments

multicomponent vp vs correlation analysis an important step in the simultaneous interpretation or inversion of multicomponent data sets is to quantitatively estimate the ratio of p wave velocity to s wave velocity vp vs in this endeavor i have developed correlation techniques to determine long wavelength components of vp vs that can lead to more accurate measurements of rock properties and processing parameters p wave reflections are correlated with converted p to s wave reflections or s wave reflections from the same location to determine which events are related to the same subsurface impedance contrasts shear waves are transformed compressed to p wave time via average vp vs conjugate operators before correlation aided by conventional p wave velocity information and petrophysical relationships this technique provides optimal vp vs estimates in a similar manner that semblance analyses provide stacking velocities these estimates can be used to transform the entire s wave trace to p wave time for short wavelength amplitude inversion

rare earth element patterns in archean high grade metasediments and their tectonic significance abstract metasediments from two contrasting types of archean high grade terrains are interpreted as being derived from distinct tectonic settings the kapuskasing structural zone canada represents the deep roots of a typical greenstone belt whereas the limpopo province southern africa and western gneiss terrain australia mainly consist of shelf sediments deposited on a granitic basement and then buried to the depths required for granulite fades metamorphism upper amphibolite to granulite fades paragneisses from the kapuskasing structural zone have ree patterns similar to those of greenstone belt sediments except where partial melting has occurred forming restites with eu enrichment and melts with eu depletion except in this latter instance metamorphism has not affected the primary ree patterns ree patterns in archean upper amphibolite to granulite facies metasediments from the central limpopo province and western gneiss terrain show wide differences ranging from patterns which resemble those in post archean terrigenous sediments to typical archean sedimentary rock patterns the diversity in ree patterns for these shallow shelf metasediments is interpreted as resulting from derivation from local provenances samples with post archean patterns displaying eu depletion are interpreted as being derived from k rich granitic plutons which were portions of small stable early archean terrains precursors of the widespread late archean proterozoic episode of major cratonic development

balanced models of boundary layer convergence in the tropics positive sea surface temperature anomalies are often coupled to the well mixed boundary layer the boundary layer then typically forces convergence and ascent the ascent can trigger moist convection established diagnostic models of boundary layer convergence employ the steady state ekman geotriptic balance here we extend the steady state balance to include non stationarity within an idealised one dimensional shallow water framework we identify three time varying balanced models planetary geotriptic pgt and semi geotriptic sgt a and sgt b these models are verified against the shallow water swe model the pgt model has prognostic mass and diagnostic momentum whereas the sgt models also include prognostic momentum the sgt models have separate ekman balanced and advecting winds the friction term in the sgt a model is a function of twice the balanced wind minus the advecting wind we show that the sgt a model has stable solutions in time and is between first and second order accurate in contrast the sgt b model s friction is a function of just the advecting wind although second order accurate the sgt b is also unstable and thus unusable for cases of significant nonlinear advection the sgt a model predicts more accurate convergence than the pgt model however the sgt a model has a less accurate geopotential field than the pgt model after a period the swe model breaks down into near grid scale gravity waves and the solutions are no longer numerically reliable the sgt a and pgt models then maintain a smooth solution with the gravity waves filtered out and thus give a more robust evolution in convergence for cases of diurnal forcing with a fast frictional time scale the sgt a model follows the growth phase of the swe model more closely than the pgt model copyright 2012 royal meteorological society and british crown copyright the met office

simultaneous inversion of pp and ps seismic data elastic parameters derived from seismic data are valuable input for reservoir characterization because they can be related to lithology and fluid content of the reservoir through empirical relationships the relationship between physical properties of rocks and fluids and p wave seismic data is nonunique this leads to large uncertainties in reservoir models derived from p wave seismic data because s waves do not propagate through fluids the combined use of p and s wave seismic data might increase our ability to derive fluid and lithology effects from seismic data reducing the uncertainty in reservoir characterization and thereby improving 3d reservoir model building we present a joint inversion method for pp and ps seismic data by solving approximated linear expressions of pp and ps reflection coefficients simultaneously using a least squares estimation algorithm the resulting system of equations is solved by singular value decomposition svd by combining the two independent measurements pp and

crustal evolution comments on the archean proterozoic transition evidence from the geochemistry of metasedimentary rocks from guyana and montana by a k gibbs c w montgomery p a o day and e a erslev

estimation of elastic parameters from avo effects in the tau p domain a quantitative avo algorithm suitable for media with slow lateral parameter variations is developed the method is based on a target oriented inversion scheme for estimation of elastic parameters in a locally horizontally stratified medium the algorithm uses band limited pp reflection coefficients in the tau p domain to estimate p and s wave velocities densities and layer thicknesses to obtain these reflection coefficients a pre processing involving the radon transform and multiple attenuation is necessary furthermore a macromodel for the velocities above the target zone must be found prior to the inversion various inversion tests involving synthetic data with white gaussian noise and modeling errors that are likely to occur in conjunction with real data have been performed in general the inversion algorithm is fairly robust since it is able to reproduce the main features of the reference model main interface locations and relative contrasts in the three unknown layer parameters are recovered from a test combining the effect of source directivity one thin layer and 20 white gaussian noise it was found that neglect of the source directivity in the inversion caused the largest errors in the estimates this indicates that it is very important either to eliminate the source directivity in amore preprocessing step or to take the directivity into account in the present algorithm despite these problems it was concluded that the inversion algorithm was able to reproduce the main features of the reference model less

combined interpretation of pp and ps data provides direct access to elastic rock properties multicomponent seismic has been around for more than 30 years but is still struggling to gain widespread acceptance although the benefits of shear wave exploration are countless only imaging through gas clouds is regularly implemented a significant niche perhaps but a niche nevertheless

estimation of elastic contrasts in a layered model from seismic ps to pp amplitude ratios summary we present a method to estimate seismic velocity and density contrasts at a given interface in a 1 d layered model using ps to pp reflection amplitude ratios the velocity structure above the reflector is constrained by traveltime modelling and the amplitude ratios are determined using the same source receiver pair for the measured pp and ps amplitudes commonoffset geometry thereby source and receiver site effects are cancelled and the remaining propagation effects are included in the ray theoretical forward modelling of theoretical ps topp ratios a minimization of the least squares misfit between observed and modelled ratios provides the remaining elastic parameters below the reflector of interest p velocity p to s velocity ratio density 1 d examples and a 2 d synthetic case study with a dipping reflector and a laterally varying overburden demonstrate the possibilities and limitations of the method an application of the method to a 0 6 km deep reflector below the campi flegrei caldera italy reveals a strong contrast with a p velocity increase from less than 2 to 3 5 km s 1 and a decrease of the p to s velocity ratio from 3 6 to 1 75 the proposed ps to pp amplitude ratio analysis is applicable for wide angle seismic reflection data especially when strong elastic parameter contrasts are expected and when source amplitudes or site effects are poorly known

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