experimental study of fluid transport processes in the matrix system of the european organic rich shales i scandinavian alum shale abstract this contribution presents results from a laboratory study investigating the fluid gas water transport properties in the matrix system of the scandinavian alum shale the maturity of the organic matter of the shale samples ranged between 0 5 and 2 4 vitrinite reflectance vr r gas he ar ch 4 and water flow properties were determined at effective stresses ranging between 5 and 30 mpa and a temperature of 45 c the effects of different controlling factors parameters on the fluid conductivity including permeating fluid moisture content anisotropy heterogeneity effective stress pore pressure and load cycling were analyzed and discussed pore volume measurements by helium expansion were conducted under controlled in situ effective stress conditions on a limited number of plugs drilled parallel and perpendicular to bedding for alum shale the intrinsic permeability coefficients measured parallel and perpendicular to bedding 6 10 22 8 10 18 m 2 were within the range previously reported for other shales and mudstones permeability coefficients were strongly dependent on permeating fluid moisture content anisotropy effective stress and other sample to sample variations the intrinsic absolute permeabilities measured with helium were consistently higher up to five times than those measured with argon and methane permeability coefficients he ch 4 measured on a dry sample were up to six times higher than those measured on an as received sample depending on effective stress the effect of moisture on measured permeability coefficients became more significant as effective stress increased permeability coefficients he ch 4 measured parallel to bedding were up to more than one order of magnitude higher than those measured perpendicular to bedding parallel to bedding all samples showed a nonlinear reduction in permeability with increasing effective stress 5 30 mpa the stress dependence of permeability could be well described by an exponential relationship

inverse q filter for seismic resolution enhancement a principal limitation on seismic resolution is the earth attenuation or q effect including the energy dissipation of high frequency wave components and the velocity dispersion that distorts seismic wavelets an inverse q filtering procedure attempts to remove the q effect to produce high resolution seismic data but some existing methods either reduce the s n ratio which limits spatial resolution or generate an illusory high resolution wavelet that contains no more subsurface information than the original low resolution data in this paper seismic inverse q filtering is implemented in a stabilized manner to produce high quality data in terms of resolution and s n ratio stabilization is applied to only the amplitude compensation operator of a full inverse q filter because its phase operator is unconditionally stable but the scheme neither amplifies nor suppresses high frequencies at late times where the data contain mostly ambient noise the latter property makes the process invertible differ

predicting capillarity of mudrocks abstract this study provides a compilation evaluation and correlation of published petrophysical datasets determined for 233 rock samples 165 mudrocks 27 sandstone 25 carbonate 11 anhydrite and 5 marlstone datasets with predominant focus on mudrocks a review of the methods used for determination of capillary breakthrough and snap off pressures is given additionally based on more recent data previously published empirical correlations are critically investigated knowledge about these two critical pressures is important for both the prediction of the capillary sealing capacity of natural gas reservoirs or co 2 storage sites but also for production estimates from tight gas or shale gas plays capillary pressure experiments when performed on low permeability core plugs are difficult and time consuming laboratory measurements on core plugs under in situ conditions are mostly performed using nitrogen but also with methane and carbon dioxide therefore mercury injection porosimetry mip measurements are preferably used in the industry to determine an equivalent value for the capillary breakthrough pressure these measurements have the advantage to be quick and cheap and only require cuttings or trim samples when evaluating the database in detail we find that 1 mip data plot well with the drainage breakthrough pressures determined on sample plugs while the conversion of the system hg air to gas brine e g ch 4 co 2 using interfacial and wettability data does not provide a uniform match potentially caused by different wettability characteristics 2 brine permeability versus capillary breakthrough pressure determined on sample plugs shows a good match and could provide a first estimate of p c values since permeability is easier to determine than capillary breakthrough pressures for imbibition snap off pressures a good correlation was found for ch 4 measured on sample plugs only 3 porosity shows a fairly good correlation with permeability for sandstone only and with plug derived capillary breakthrough pressures for sandstones carbonates and evaporates no such correlations exist for mudrocks 4 air and brine derived permeabilities show an excellent correlation and 5 from the data used we do not infer any direct correlations between specific surface area ssa mineralogy or organic carbon content with permeability or capillary pressure however we were able to better predict permeabilities using a more sophisticated model that relies on a combination of these parameters

reflection waveform inversion using local descent methods estimating attenuation and velocity over a gas sand deposit prestack seismic reflection data contain amplitudes traveltimes and moveout information waveform inversion of such data has the potential to estimate attenuation levels reflector depths and geometry and background velocities however when inverting reflection data strong nonlinearities can cause reflectors to be incorrectly imaged and can prevent background velocities from being updated to successfully recover background velocities previous authors have resorted to nonlinear global search inversion techniques we propose a two step inversion procedure using local descent methods in which we perform alternate inversions for the reflectors and the background velocities for our reflector inversion we exploit the efficiency of the back propagation method when inverting for a large parameter set for our background velocity inversion we use newton inverse methods during the background velocity inversions it is crucial to adaptively depth stretch the model to preserve the vertical traveltimes this reduces nonlinearity by largely decoupling the effects of the background velocities and reflectors on the data nonlinearity is further reduced by choosing to invert for slownesses and by inverting for a sparse parameter set which is partially defined using geological reflector picks applying our approach to shallow seismic data from the north sea collected over a gas sand deposit we demonstrate that the proposed method is able to estimate both the geometry and internal velocity of a significant velocity structure not present in the initial model over successive iterations the use of adaptive depth stretching corrects the pull down of the base of the gas sand vertical background velocity gradients are also resolved for an insignificant extra cost the acoustic attenuation parameter q is included in the inversion scheme the final attenuation tomogram contains realistic values of q for the expected lithologies and for the effect of partial fluid saturation associated with a shallow bright spot the attenuation image may also indicate the presence of fracturing

effective stress law for the permeability of clay rich sandstones 1 two models of clay rich sandstones are analyzed to explain the relative sensitivity of permeability to pore pressure and confining pressure in one model the clay lines the entire pore wall in a layer of uniform thickness and in the second model the clay is distributed in the form of particles that are only weakly coupled to the pore walls equations of elasticity and fluid flow are solved for both models giving expressions for the effective stress coefficients in terms of clay content and the elastic moduli of the rock and clay both models predict that the permeability will be much more sensitive to changes in pore pressure than to changes in confining pressure the clay particle model gives somewhat better agreement with data from the literature and with new data on a stainton sandstone having a solid volume fraction of 8 clay

comparison of geomechanical deformation induced by megatonne scale co2 storage at sleipner weyburn and in salah geological storage of co2 that has been captured at large point source emitters represents a key potential method for reduction of anthropogenic greenhouse gas emissions however this technology will only be viable if it can be guaranteed that injected co2 will remain trapped in the subsurface for thousands of years or more a significant issue for storage security is the geomechanical response of the reservoir concerns have been raised that geomechanical deformation induced by co2 injection will create or reactivate fracture networks in the sealing caprocks providing a pathway for co2 leakage in this paper we examine three large scale sites where co2 is injected at rates of 1 megatonne y or more sleipner weyburn and in salah we compare and contrast the observed geomechanical behavior of each site with particular focus on the risks to storage security posed by geomechanical deformation at sleipner the large high permeability storage aquifer has experienced little pore pressure increase over 15 y of injection implying little possibility of geomechanical deformation at weyburn 45 y of oil production has depleted pore pressures before increases associated with co2 injection the long history of the field has led to complicated sometimes nonintuitive geomechanical deformation at in salah injection into the water leg of a gas reservoir has increased pore pressures leading to uplift and substantial microseismic activity the differences in the geomechanical responses of these sites emphasize the need for systematic geomechanical appraisal before injection in any potential storage site

seismic attenuation of atlantic margin basalts observations and modeling paleogene basalts are present over much of the northeastern atlantic european margin in regions containing significant thicknesses of layered basalt flows conducting seismic imaging within and beneath the volcanic section has proven difficult largely because the basalts severely attenuate and scatter seismic energy we use data from a vertical seismic profile vsp from well 164 07 1 that penetrated 1 2 km of basalt in the northern rockall trough west of britain to measure the seismic attenuation caused by the in situ basalts the effective quality factor qeff of the basalt layer is found from the vsp to be 15 35 which is considerably lower more attenuative than the intrinsic attenuation measured on basalt samples in the laboratory we then run synthetic seismogram models to investigate the likely cause of the attenuation full waveform 1d modeling of stacked sequences of lava flows based on rock properties from the same well indicates that much of the seismic attenuation observed from the vsp can b

elastic wave equation traveltime and waveform inversion of crosswell data a method is presented for reconstructing p and s velocity distributions from elastic traveltimes and waveforms the input data consist of crosswell hydrophone records generated by a piezoelectric borehole source borehole effects are partially accounted for by using a low frequency green s function to simulate the pressure generated in the fluid filled receiver well the tube waves in the borehole are ignored on the assumption that they can be removed from the field data by median filtering in addition the source radiation pattern is partially taken into account by inverting for the equivalent stress components acting on the earth at the source location the elastic wave equation traveltime and waveform inversion wtw method is applied to both synthetic crosswell data and the mcelroy field crosswell data as predicted by theory results show that elastic wtw tomograms provide a sharper interface image than delineated in the traveltime tomograms the spatial resolution of the mcelroy traveltime tomogr

the middle palaeolithic of west africa lithic techno typological analyses of the site of tiemassas senegal abstract due to its significant position between the sahara desert and tropical africa senegal may have played a decisive role in the dispersal of modern humans between north and sub saharan africa however our knowledge about these intra african dispersals and the character of the demographic connection between north and sub saharan africa are poorly understood and archaeological records in the sahel are limited between 1940 and 1960 the senegalese littoral yielded prehistoric sites attributed to the middle stone age msa or middle palaeolithic this chrono cultural framework is based on typological considerations about lithic industries generally found in secondary or disturbed stratigraphic contexts of these sites tiemassas has been considered to be the most important located about 100 km from dakar the site has been considered middle palaeolithic mesolithic and even neolithic but has not been analysed in detail in this paper the compositions of the lithic assemblages represented at tiemassas are discussed and their technological strategies are analyzed results indicate that the site is characterized by the use of diverse strategies of raw material exploitation in relation to the morphology and morphometry of the exploited pebbles the assemblage is flake dominated generally characterized by typical msa methods such as levallois opportunistic systeme par surface de debitage alterne ssda and discoid flaking and more rarely by laminar methods finally retouch is usually applied to transform objects into side scrapers these results are indicative of a msa cultural attribution and represent a first step in the process of definition and description of the senegalese msa together with its wider continental context

direct thermoluminescence chronology for early iron age smelting technology on the gambaga escarpment ghana abstract we present luminescence dates which demonstrate a full blown smelting technology in northern ghana west africa during the early iron age our chronology is based on thermoluminescence tl dating of quartz grains extracted from the walls of three iron smelters located at the birimi site in the northern region of ghana two of the smelters yielded statistically indistinguishable ages of 1080 70 and 1090 60 years while the third yielded a higher age of 1600 100 years all are significantly older than the sole direct radiocarbon date of 550 330 calbp 460 90 bp obtained on a furnace in the northern region the tl ages indicate that iron smelting was well established in the northern region before the middle of the first millennium ad and corroborate the validity of a number of similarly early radiocarbon dates associated with early iron age ceramics but not directly associated with smelting activity from other sites in northern ghana the iron working remains at birimi are located on a river terrace only a few tens of meters west of a dense kintampo occupation radiocarbon and tl dates for the kintampo complex demonstrate that the iron age and kintampo components at birimi are clearly non contemporaneous the occurrence of two distinct layers of goethite within 150 cm of the terrace surface both of which are clearly exposed in the scarp of the terrace upon which the smelters are situated indicates that the industrial site was deliberately sited to take advantage of the readily available source material this premise is confirmed by geochemical analyses of sediment goethite and slag from the smelting site we therefore propose that the frequent proximity of kintampo and iron production sites is incidental in the sense that each group exploited different resources offered by a riverbank location

gas permeability calculation of tight rocks based on laboratory measurements with non ideal gas slippage and poroelastic effects considered abstract permeability measurements on low permeable rocks in the laboratory require much higher pressure gradients than those in real reservoirs to produce detectable flow rates in finite laboratory time this may result in a high effective stress gradient that can cause non uniform deformation of the pore system to better understand the measured laboratory data a theoretical model has been developed for calculating gas permeability of tight rock from laboratory measurements which couples the effect of poroelastic deformation with the gas non ideality and slippage effects the proposed characteristic pressure model considers the poroelastic deformation and the real gas effects in the permeability calculation which improves the accuracy of calculated permeability from laboratory measurements of tight rocks under large pressure gradients the new model is validated by independent multiscale simulations in which the poroelastic deformation and slippage effects are captured on the pore scale while the real gas behavior is captured on the core scale the numerical results also indicate that the poroelastic deformation mainly affects the high pressure region while the variation of gas properties dominates the low pressure region the new model is then applied to the calculation of gas permeability based on the laboratory measurements on coal and shale samples with non ideal gas slippage and poroelastic effects considered the poroelastic deformation and the real gas effect can be important as well as the slippage effect and the calculated apparent permeability will be overestimated if these two effects are neglected

stress dependence of the permeability and porosity of sandstone and shale from tcdp hole a abstract we utilize an integrated permeability and porosity measurement system to measure the stress dependent permeability and porosity of pliocene to pleistocene sedimentary rocks from a 2000 m borehole experiments were conducted by first gradually increasing the confining pressure from 3 to 120 mpa and then subsequently reducing it back to 3 mpa the permeability of the sandstone remained within a narrow range 10 14 10 13 m2 the permeability of the shale was more sensitive to the effective confining pressure varying by two to three orders of magnitude than the sandstone possibly due to the existence of microcracks in the shale meanwhile the sandstone and shale showed a similar sensitivity of porosity to effective pressure whereby porosity was reduced by about 10 20 when the confining pressure was increased from 3 to 120 mpa the experimental results indicate that the fit of the models to the data points can be improved by using a power law instead of an exponential relationship to extrapolate the permeability or porosity under larger confining pressure e g 300 mpa using a straight line in a log log plot might induce unreasonable error but might be adequate to predict the stress dependent permeability or porosity within the experimental stress range part of the permeability and porosity decrease observed during loading is irreversible during unloading

imaging high resolution seismic velocity from walkaway vertical seismic profile data in a carbonate reservoir using acoustic waveform tomography abstracthigh resolution seismic velocity was obtained using acoustic full waveform tomography of walkaway vertical seismic profile vsp data from an oil field dominated by carbonate rocks offshore abu dhabi in the united arab emirates the data were collected in a deviated borehole with receivers located from 521 to 2742 m depth the inversion was performed in the frequency domain the success of the inversion was determined by three important factors the starting model the preconditioning of the input data and the inversion strategy which included an appropriate selection of a damping term in the laplace fourier transformation the inversion was performed between the frequencies of 4 and 50 hz and a logarithmic data residual was used the extracted 1d velocity profiles from the final high resolution velocity model correlate well with the sonic log and estimated vertical incidence vsp velocities the predicted data obtained by the final velocity model indicate a generally good fit with the field

wave equation traveltime inversion this paper presents a new traveltime inversion method based on the wave equation in this new method designated as wave equation traveltime inversion wt seismograms are computed by any full wave forward modeling method we use a finite difference method the velocity model is perturbed until the traveltimes from the synthetic seismograms are best fitted to the observed traveltimes in a least squares sense a gradient optimization method is used and the formula for the frechet derivative perturbation of traveltimes with respect to velocity is derived directly from the wave equation no traveltime picking or ray tracing is necessary and there are no high frequency assumptions about the data body wave diffraction reflection and head wave traveltimes can be incorporated into the inversion in the high frequency limit wt inversion reduces to ray based traveltime tomography it can also be shown that wt inversion is approximately equivalent to full wave inversion when the starting velocity model is

residual migration velocity analysis in the plane wave domain over the last few years migration velocity analysis methods have been developed for 2 d and 3 d models by extending the assumptions and approximations used for rms velocity models computational requirements for these analyses have increased dramatically because top down layer stripping migration is needed to derive interval velocities directly instead of using rms velocities and then converting into interval velocities we establish exact equations for 1 d and 2 d residual velocity analysis in the depth plane wave domain and use these in an iterative and interactive migration velocity analysis program the new method updates interval velocities directly in a top down residual difference correction for all layers after prestack depth migration instead of top down layer stripping migration followed by residual analysis this makes the new method a suitable tool for migration velocity analysis especially for 3 d surveys we test the method on synthetic and field data the field data results show that a reasonable velocity model is obtained and most common image gathers are correctly imaged using no more than four iterations

migration velocity analysis accounting for the effects of lateral velocity variations the most common migration velocity analysis algorithms iterative profile migration focusing analysis and stack power analysis are based on restrictive subsurface assumptions that may cause the methods to break down in the presence of lateral velocity variations typically the subsurface is assumed to have either a constant velocity or at most a depth variable velocity recent innovations include the use of traveltime inversion philosophy to invert migration measurements of the curvature as a function of offset exhibited by an event following migration traveltime inversion makes few assumptions regarding the subsurface but is a rather unstable process thus an important question is under what conditions do the traditional methods break down and make the use of traveltime inversion methods mandatory marrying the common migration analysis with tomography results in a set of equations that while useful for generating updates from migration measurements are too complex for answering the above qu

two dimensional full wavefield inversion of wide aperture marine seismic streamer data summary a 2 d full wavefield inversion method is presented for the processing of wide aperture data the diversity of information contained within such datasets may be handled in a complete manner by first matching the traveltimes of the main events and then progressing to waveform fitting of the data through explicit full wavefield modelling our wavefield inversion scheme is based upon a finite difference solution of the 2 d elastic wave equation in the time distance domain the strength of adopting such an approach is the ability to generate all possible wave types within a given 2 d model multiples converted waves etc and thus to simulate and accurately model complex seismic wavefields the aim of the inversion is to find the 2 d p wave velocity model that minimizes the least squared difference between the observed and synthetic data across the full range of offsets following extensive testing on synthetic data the wavefield inversion scheme has been applied to wide aperture real marine seismic streamer datasets we present results from the synthetic testing and the wavefield inversion of wide aperture real data out to 12 km offset that was recorded on a single streamer even though current computational restrictions allow only a small subsection of the data to be analysed these examples demonstrate the potential value of wide aperture 2 d full wavefield inversion

experimental study of fluid transport processes in the matrix system of the european organic rich shales ii posidonia shale lower toarcian northern germany abstract a laboratory study has been conducted to investigate the transport of gases he ar ch 4 and water in the matrix of lower toarcian posidonia shale samples from three shallow boreholes in northern germany the maturity of the organic matter of the shale samples ranged between 0 53 and 1 45 vitrinite reflectance vr r the measurements were performed at effective stresses ranging between 6 and 37 mpa and a temperature of 45 c the effects of different controlling factors including permeating fluid maturity anisotropy moisture content and effective stress on the fluid conductivity were analyzed and discussed permeability coefficients measured perpendicular and parallel to bedding 3 10 22 to 9 7 10 17 m 2 were within the range previously reported for other shales and mudstones they exhibited a strong dependence on permeating fluid maturity anisotropy moisture content and effective stress the permeability coefficients measured with helium as permeate were consistently higher up to two times than those measured with argon and methane permeability coefficients measured with water were up to three orders of magnitude lower than klinkenberg corrected gas permeability coefficients measured with helium and methane under similar experimental conditions among the samples studied the lowest porosity and permeability coefficients were measured on samples of intermediate thermal maturity 0 88 vr r oil window permeability coefficients he ch 4 measured parallel to bedding were up to more than one order of magnitude higher than those measured perpendicular to bedding permeability coefficients measured with he and ch 4 on a dry sample were up to two times higher than those measured on a sample with the as received moisture content all samples showed a nonlinear reduction in permeability parallel to bedding with increasing effective stress 6 37 mpa the permeability anisotropy and stress dependence of permeability were controlled by the mineralogy

optical and thermoluminescence dating of middle stone age and kintampo bearing sediments at birimi a multi component archaeological site in ghana abstract we report the first luminescence ages for the archeological and geological sediments forming the substrate of the birimi archaeological site in the northern region of ghana the site s significance rests on the fact that it contains a rich collection of artifact assemblages representative of three distinct cultures and that on the basis of artifact typology the earliest assemblage is diagnostic of the middle stone age msa in situ occurrences of msa artifacts are found at over 1 m below today s surface they are overlain by a ceramic rich complex of a sedentary or semi sendentary later stone age culture known as the kintampo the western half of the site is dominated by the industrial remains of iron age smelting activity elemental mineralogical and sedimentological analysis of the cultural and sub cultural sedimentary horizons at the site revealed at least three distinct lithostratigraphic units the quartz sediments are derived from the sandstone of the gambaga escarpment mass wasted and accreted fluvially at a rate of 3 2 cm ka forming a wide terrace at birimi silts and finer fractions derive from windblown dust likely from white volta river and granitic sources to the north soil forming processes and wide fluctuations in moisture have progressively reduced the sediments at depth to the resistant quartz and kaolinite with rich iron oxide coatings and created two ironstone horizons composed of goethite cemented quartz nodules multiple aliquot green light stimulated optical ages for 125 150 m quartz grains yielded ages of 23 6 2 9 and 40 8 11 8 ka for the msa bearing sediments and 58 4 15 3 ka for the base of the terrace radiocarbon ages on charcoal from kintampo bearing units are 3 36 3 83 ka cal bp and are supported by thermoluminescence tl ages on pottery sherds and burnt house daub fragments of this cultural complex a 0 4 ka age on sediment from the site s surface confirms that the quartz zeroes well when exposed to natural light sediments bearing the kintampo artifacts however yielded ages of 7 8 16 9 ka these ages were obtained on sediments from large pits some over 50 cm deep and they deviate only slightly from the ages expected for naturally aggraded sediments at these depths we conclude therefore that extensive digging of pits by the kintampo dwellers was followed by rapid refilling and that the bulk mobilization of the matrix did not permit the sedimentary quartz grains to experience any appreciable zeroing at that time

combining wave equation imaging with traveltime tomography to form high resolution images from crosshole data traveltime tomography is an appropriate method for estimating seismic velocity structure from arrival times however tomography fails to resolve discontinuities in the velocities wave equation techniques provide images using the full wave field that complement the results of traveltime tomography we use the velocity estimates from tomography as a reference model for a numerical propagation of the time reversed data these backpropagated wave fields are used to provide images of the discontinuities in the velocity field the combined use of traveltime tomography and wave equation imaging is particularly suitable for forming high resolution geologic images from multiple source multiple receiver data acquired in borehole to borehole seismic surveying in the context of crosshole imaging an effective implementation of wave equation imaging is obtained by transforming the data and the algorithms into the frequency domain this transformation allows the use of efficient frequency domain numerical propagat

acoustic wave equation traveltime and waveform inversion of crosshole seismic data a hybrid wave equation traveltime and waveform inversion method is presented that reconstructs the interwell velocity distribution from crosshole seismic data this inversion method designated as wtw retains the advantages of both full wave inversion and traveltime inversion i e it is characterized by reasonably fast convergence which is somewhat independent of the initial model and it can resolve detailed features of the velocity model in principle no traveltime picking is required and the computational cost of the wtw method is about the same as that for full wave inversion we apply the wtw method to synthetic data and field crosshole data collected by exxon at their friendswood texas test site results show that the wtw tomograms are much richer in structural information relative to the traveltime tomograms subtle structural features in the wtw friendswood tomogram are resolved to a spatial resolution of about 1 5 m yet are smeared or completely absent in the traveltime tomogram this sugg

luminescence dating of hillslope deposits a review abstract luminescence dating determines the last exposure to light of quartz and feldspar mineral grains and thus the time a sediment was laid down prerequisite is that the sediment grains were sufficiently exposed to light prior to deposition for eolian deposits this seems a fair assumption although exceptions may well exist for other depositional environments light exposure prior to burial is often restricted in duration intensity and spectral composition and may result in an age overestimation recent developments now allow dating of sediments that were exposed to only little light prior to deposition the main developments are single aliquot techniques and statistical tests that allow extraction of valid age estimates even from deposits in which bleached and unbleached grains are mixed these developments in combination with the fact that the great majority of sediments near the earth s surface are not of eolian origin have resulted in the large interest in the luminescence dating of non eolian deposits here we review possibilities and challenges of luminescence dating of colluvial deposits we summarize techniques for the detection and handling of insufficiently bleached sediments a common condition in colluvial deposits we give an overview how luminescence dating has been applied on hillslope sediments for reconstructing landscape response to climate change to analyze past fault activity and unravel human induced soil erosion we discuss sampling strategies and give guidelines as to which techniques are best suited to establish luminescence chronologies for colluvium

full waveform tomography for lithospheric imaging results from a blind test in a realistic crustal model summary a comprehensive validation of 2 d frequency domain acoustic wave equation tomography was undertaken in a blind test using third party realistic elastic wave equation data the synthetic 2 d wide angle seismic data were provided prior to a recent workshop on the methods of controlled source seismology the true model was not revealed to the authors until after the presentation of our waveform tomography results the original model was specified on a detailed grid with variable p wave velocity s wave velocity density and viscoelastic q factor structure designed to simulate a section of continental crust 250 km long and 40 km deep synthetic vertical and horizontal component data were available for 51 shot locations spaced every 5 km recorded at 2779 receivers spaced every 90 m evenly spread along the surface of the model the data contained energy from 0 2 to 15 hz waveform tomography a combination of traveltime tomography and 2 d waveform inversion of the early arrivals of the seismic waveforms was used to recover crustal p velocity structure from the vertical component data using data from 51 sources 1390 receivers and frequencies between 0 8 and 7 0 hz the waveform tomography result contained apparent structure at wavelength scale resolution that was not evident on the traveltime tomography result the predicted acoustic waveforms in the final result matched the original elastic data to a high degree of accuracy during the workshop the exact model was revealed over much of the model the waveform tomography results provided a good correspondence with the true model from large to intermediate wavelength scales with a resolution limit on the order of 1 km a significant near surface low velocity zone invisible to traveltime methods was correctly recovered the results also provided a high resolution image of the complex structure of the entire crust and the depth and nature of the crust mantle transition some inaccuracies were observed near the edges of the images due to the limited ray coverage inherent to the footprint of the survey geometry several aspects of the waveform tomography strategy were critical to the success of the acoustic method with realistic synthetic viscoelastic data i the accuracy of the starting model from traveltime tomography ii implementation in the frequency domain iii the use of complex valued frequencies to effect time damping of the data residuals iv the selection of a suitable subset of data and data frequencies v progressive inversion of low to high frequency components of the data vi initial pre inversion matching of the amplitudes between observed and modelled data and vii sufficient preconditioning of both the data and the update images combined these strategies were effectively equivalent to a multiscale approach that mitigated the non linearity of the seismic inverse problem during the inversion we carried out repeated forward modelling to ensure our modelled waveforms matched the observed data as closely as possible in both frequency and time domains the synthetic data set used in this paper provides a benchmark for future testing of modelling inversion and imaging algorithms for wide angle lithospheric imaging

a comparison between the behavior of objective functions for waveform inversion in the frequency and laplace domains in the frequency domain gradient based local optimization methods of waveform inversions have been unsuccessful at inverting subsurface parameters without an accurate starting model such methods could not correct automatically for poor starting models because multiple local minima madeitdifficulttoapproachthetrueglobalminimum inthis study wecomparedthebehaviorofobjectivefunctionsinthe frequency and laplace domains wavefields in the laplace domain correspond to the zero frequency component of a damped wavefield thus the laplace domain waveform inversion can image smooth velocity models objective functions in the laplace domain inversion have a smoother surface and fewer local minima than in the frequency domain inversion weappliedthewaveforminversiontoa2dsliceof the acoustic seg eage salt model in the laplace domain and recovered smooth velocity models from inaccurate initial velocity conditions we also successfully imaged velocities of the salt seg overthrust and institut francais du petrolemarmousimodelswiththefrequency domaininversion method by using the inverted velocity model of the laplacedomaininversionastheinitialmodel

applications of multiscale waveform inversion to marine data using a flooding technique and dynamic early arrival windows a recently developed time domain multiscale waveform tomography mwt method is applied to synthetic and field marine data although the mwt method was already applied to synthetic data the synthetic data application leads to a development of a hybrid method between waveform tomography and the salt flooding technique commonly use in subsalt imaging this hybrid method can overcome a convergence problem encountered by inversion with a traveltime velocity tomogram and successfully provides an accurate and highly resolved velocity tomogram for the 2d seg eage salt model in the application of mwt to the field data the inversion process is carried out using a multiscale method with a dynamic early arrival muting window to mitigate the local minima problem of waveform tomography and elastic effects with the modified mwt method reasonably accurate results as verified by comparison of migration images and common image gathers were obtained the hybrid method with the salt flooding technique is not used in this field data example because there is no salt in the subsurface according to our interpretation however we believe it is applicable to field data applications

use of a computational fault extraction process with calibrations to characterize a fractured basement reservoir yufutsu japan the yufutsu oil and gas field located in hokkaido northern japan produces hydrocarbon from a typical fracture type reservoir composed of very tight cretaceous granitic basement and overlying conglomerate of the eocene here delineations of faults accompanying large open fractures are essential for optimal developments to capture fault distribution objectively various seismic attribute estimates ascribed to fault distributions are derived from three dimensional seismic data by computational procedures however to use the estimates properly calibrating them with independent observations other than seismic data is important we present a calibration scheme by coupling seismic data with microseismic data and in situ stress data to delineate active faults under a strike slip faulting stress regime in the yufutsu field active faults are interpreted to be fluid pathways formed by shear dilation in the calibration two kinds of parameter sets are tuned one controls linkages of fault responses fragmented by artificial noises caused by seismic acquisition and processing to adjust spatial continuities of fault surfaces properly another limits extracted fault strikes with respect to mohr coulomb failure criterion to highlight active faults the calibrated seismic attribute estimates show a qualitative consistency with the microseismic hypocenter distribution observed during a massive hydraulic stimulation in addition a large difference in gas productivity observed at four wells from very high productivity to no gas flowing is clearly related to an existence of distinct lineation with strong magnitudes of the calibrated seismic attributes it suggests that the calibrated estimate becomes a criterion to judge an economic viability of a well

early arrival waveform tomography on near surface refraction data we develop a waveform tomography method for estimating the velocity distribution that minimizes the waveform misfit between the predicted and observed early arrivals in space time seismograms by fitting the waveforms of early arrivals early arrival waveform tomographyewt naturally takes into account more general wave propagation effects compared to the high frequency method of traveltime tomography meaning that ewt can estimate a wider range of slowness wavenumbers another benefit of ewt is more reliable convergence compared to full waveform tomography because an early arrival misfit function contains fewer local minima synthetic test results verify that the waveform tomogram is much more accurate than the traveltime tomogram and that this algorithm has good convergence properties for marine data from the gulf of mexico the statics problem caused by shallow gassy muds was attacked by using ewt to obtain a more accurate velocity model using the waveform tomogram to correct for statics the stacked section was significantly improved compared to using the normal moveout nmo velocity and moderately improved compared to using the traveltime tomogram inverting high resolution land data from mapleton utah showed an ewt velocity tomogram that was more consistent with the ground truth trench log than the traveltime tomogram our results suggest that ewt can provide supplemental shorter wavelength information compared to the traveltime tomogram for both shallow and moderately deep seismic data