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60th EAGE Conference and Exhibition
- Conference date: 08 Jun 1998 - 12 Jun 1998
- Location: Leipzig, Germany
- ISBN: 978-90-73781-09-2
- Published: 08 June 1998
1 - 50 of 489 results
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Tomography and Depth Imaging
By R. BloorBuilding a depth velocity model for prestack depth migration is a time consuming and complicated task . To assist this talk we require as much a priori information as possible. Additionally we use the simplest methods which will address the problem of building the vetocity model for the current structure (Bloór et al. 1997, Stork et al. 1997). However, as structure becomes more complicated we have to resort to more complex methods to determine the vetocity model.
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Testing the Behaviour of Differential Semblance for Velocity Optimization
Authors H. Chauris, M. Noble and P. PodvinBackground velocity estimation is a critical step for the depth imaging process. Because of constant increase of acquired 3D data volumes, this velocit estimation, cast as an inverse problem, should be automated (no picking).
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Velocity Macro Model Estimation by Stereotomography - Application to Real Data
Authors F. Billette, G. Lambaré and P. PodvinIn [1] and [2], we introduced a. new tomographic method, Stereotomography, for estirnating velocity macro rnodels from seismic reflection data.
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Dispersion of 3D Velocity Estimators
More LessWe study the dispersion of the estimators of a 3D velocity model in presence of white noise and with a limited range of azimuths available.
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CRP-Scan - Solving 3D PreSDM Velocity Analysis with Zero-Offset
Authors F. Audebert, P. Guillaume, X. Zhang and I. JonesMigration velocity analysis (MVA) should allow interpreters to check and improve the complex velocity models required for 3D pre-stack depth imaging
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3D Adaptive Tomography by the Fresnel Criterion
Authors P. Galuppo, G. Böhm and A. VesnaverSeismic tomography adopts usually ray tracing as the forward modelling tool for the traveltime inversion.
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Estimation Laterally Varying Velocity Models Using Focusing Operators
Authors R. F. Hegge and J. T. FokkemaThe estimation of macromodels containing laterally varying velocities presents no problem for the method which is based on on the global inversion of focusing operators.
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Practical Anisotropic Imaging
Authors R. Schmid, P. Butler and R. VestrumThere is a strong resurgence and renewed interest in the study of anisotropy. Most of the excellent research involves the theoretical aspects, studying anisotropy in flat lying beds, or using shear wave anisotropy in fracture detection. It is natural and fitting that anisotropy research is performed in the depth domain. However, most depth imaging is performed in complex structural environments, typically for thrustbelt or subsalt imaging. Therefore, truly practical depth imaging which attempts to correct for anisotropic affects must deal with dipping anisotropic geologie formations.
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Pattern Recognition and Subtraction of Coherent Noise
By S. SpitzA crucial issue when processing seismic data is the ability to remove coherent noise while preserving the amplitudes of the signal. Strong noise (multiple reflections, ground roll, converted waves in compression mode analysis) interferes with the signal and can lead to incorrect pre stack attributes and to erroneous interpretations of the final images at target level.
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Tests of a Two-Step Correction Procedure for Long-Offset Data
Authors F. K. Levin and R. C. ChambersThe use in recent years of offset-to-reflector depth ratios of two or three rather than the unity common earlier has resulted in traveltime-offset curves that are not hyperbolic. For long offsets or where anisotropy is important, a need to include a quartic term in the squared traveltime-squared offset function has been established. Long offsets are common today for AVO analysis in areas such as the Gulf of Mexico.
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Traveltime Picking in 3D Data Volumes
Authors N. Bienati and U. SpagnoliniTomography, seismic imaging, and statics require the estimation of traveltimes from 3-D pre-stack data volumes. Manual interpretation is known to be time consuming and not free of errors. We propose here an automatic and robust traveltime picking of 3-D data volumes that avoids (or at least aids) manual intepretation
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Is Common-Offset Common-Azimuth DMO Really That Bad?
By R. FerberThe cross-spread is the basic subset of the orthogonal geometry. It is a single-fold 3D data set which was shown by Vermeer et al. (1995) to be suitable for DMO. This was good news, because DMO was usually regarded as an operation on common-offset common-azimuth (COA) subsets of the acquisition geometry.
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Interactive Polarization Filtering of Nine-Component Seismic Data
By A. H. BalchSome areas of geologic and economic importance are so hostile to seismic investigations, that processing and interpretation of data obtained there remain difficult or impossible, despite the best state-of-the art field and processing procedures
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Practical Wave Equation Datuming
By M. StanleyApplication of Wave Equation Datuming (WED) can produce dramatically improved seismic images. However the technique has not received the degree of acceptance it probably deserves for a number of reasons
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A New Cost-Effective Approach to Statics in Sand Dunes Areas
Authors P. Storer, A. Corrao and M. PastoriStatics computation for reflection seismic in areas covered by sand dunes still remains a challenging problem in the hydrocarbon exploration activity
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A Novel Approach to Cost Effective 4C/4D - the Teal South Experiment
Authors D. Ridyard, P. Maxwell, G. Fisseler and S. RocheUntil quite recently, multicomponent recording has been a minor part of the seismic market, and systems have required expensive and time consuming adaptation to facilitate 4-C recording (three component velocity plus a pressure transducer). The cost and inconvenience of these adaptations has lead to a cost premium in 4-C. As the value of 4-C is becoming apparent, from numerous experimental surveys, it is now time to rethink some of the basic system design concepts to address the practicalities of efficient 4-C recording.
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Seismic Detector Positioning in a 4D/4C OBC Survey Using Both Acoustics and First Breaks
More LessIn the summer of 1997 Texaco conducted, over their Teal South field, the first time-lapse (4-D), multicomponent (4-C), ocean bottom cable (OBC) seismic survey in the Gulf of Mexico.
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4C Sea Bottom Receiver Evaluation
Authors J. Meunier, J-J. Chameau, J. Bijou and J. MaidaSummary not available
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On-Board Processing of Ocean Bottom Cable Multicomponent Data
Authors N. Jones, J. E. Gaiser and E. AngererHistorically, observations of shear-waves in the marine environment began with the work of oceanographic institutes in their investigations of ocean-crust velocity structure.
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t-p Domain Combination of Dual-Sensor Ocean Bottom Cable Data
By R. WombellOBC data is usually processed assuming normal incidence and ignoring angular variations in the geophone response, water bottom reflectivity and reverberation period. A z-p domain decomposition allows the angular variations within the data to be separated and handled. An approach to handling the ghost attenuation is described
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An Essential Processing Correction for Seabed Recording
By C. MacBethThe processing of recordings made at, or near, the seabed is rendered inaccurate by naturally occuring amplitude and phase changes
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Azimuthal Moveout Analysis for Fracture Detection in Marine Streamer Data
By X-Y. LiIn dual-sensor ocean-bottom-cable surveys both pressure and velocity data are recorded. Both data sets contain the up-going energy convolved with their corresponding receiver-ghost operators. The ultimate goal of dual-sensor processing is to eliminate the ghost response and the water bottom reverberation
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Hydrophone-Geophone Deghosting of OBC Data in the t-p Domain
By R. BaleThe receiver ghost for ocean bottom recording, unlike a towed streamer ghost, generates notches in the seismic passband. Fortunately, the positioning of dual or multi-component sensors on the sea bottom presents an opportunity for removing the receiver ghost and reverberation sequence whilst producing a single combined output from the hydrophone and geophone
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3D Target-Oriented AVO Inversion of Data from the Statfjord Field
Authors S. Østmo, E. Tjåland, A. Buland and R. SollieStratigraphic full waveform AVO-inversion is a powerful technique for determining P- and S-wave velocities and densities from seismic pre-stack data
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AVO Behaviour at the Top of a Class-4 Sand - a Case Study of the Maitland-1 Well
More LessThe Maitland gas field is located in the Barrow Sub-basin, offshore Western Australia. The well Maitland-1 was drilled in September 1992 on a strong amplitude anomaly. It intersected a 23m thick land with gas saturation. The well was plugged and abandoned as a gas discovery (Sit).
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Improved Seismic Resolution of the Ty Reservoir by AVO-Processing, Sleipner Øst Field
Authors K. Duffaut, T. Erling and K. HorpestadThe field has its main production from a Paleocene deepwater sandstone reservoir . The main geophysical challenges in the field have been to identify the top reservoir, the reservoir pinch-out zone and internal reservoir geometry. To understand the seismic response at reservoir level a geophysical modeling study (including AVO-modeling) was performed. Well data and pre-stack data from 10 lines were used in the modeling. The modeling showed that the mis-tie between synthetic seismograms and surface seismic data in the hydrocarbon bearing part of the reservoir was caused by an AVO effect. Both the modeled and the real CMP-gathers showed a rapid decrease of the amplitude with offset including a polarity reversal. To avoid the effect of this polarity reversal on the stacked data the concept of Intercept-stack was introduced. The Intercept-stack is an extrapolation of the near offset reflectivity to zero offset.
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Postcritical-Angle AVO for Carbonate Reservoirs
Authors O. K. Youn, H-W. Zhou, S. A. Hall and R. E. SheriffMost carbonate reefs under shale have small critical angle and small amplitude variation with offset (AVO) in the precritical offset range.
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AVA and Residual Moveout
By I. MooreIt is well known that residual moveout can cause large errors in the estimate of amplitude versus angle (AVA) attributes, and in particular in the estimate of gradients. This paper illustrates the problem and proposes two complementary approaches to reducing the effect. Synthetic data are used to assess the effectiveness of these methods, which have also been applied to real data.
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Are Near-Offset Shear Wave Conversions Useful?
By C. MacBethIt is standard to record near-or zero-offset VSP with three-component receiver tools. However, the principal use of these data is to determine model velocities and a high resolution section as an aid to interpretation of surface seismic data. These objectives are fulfilled using only the vertical component recordings.
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Amplitude Versus Offset for Refracted Waves
Authors P. Borejko, E. Brückl and W. ChwatalThe analysis of amplitude versus offset (AVO) is widely used in reflection seismic processing and interpretation. By this technique lithological information (S-wave velocity and density) can be extracted from P-wave reflection coefficients.
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Viscoacoustic Asymptotic Waveform Inversion of Ultrasonic Laboratory Data
Authors A. Ribodetti, H. -P. Valero, S. Operto, J. Virieux and D. GilbertIn this study, we test asymptotic diffraction tomography for viscoacoustic medium imaging by scaled model ultrasonic experiment. Diffraction tomography (namely, the inverse scattering problem) is a useful technique to save various classes of problems involving non destructive evaluation such as seismic exploration and ultrasonic medical imaging . Diffraction tomography is used to image the discontinuities of parameters describing the medium both in terms of localization and true amplitude of the discontinuities.
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Joint 3D Inversion of Direct and Reflected Arrivals from Surface and SWD Seismic Data
Authors G. Rossi, P. Corubolo, G. Böhm, P. Dell‘Aversana and E. CeragioliVertical Seismic Profiles (VSP) provide an effective tie between well information (as logs and core analysis) and surface seismics, by linking the local geology to the Earth reflectivity. Seismic tomography gets similar benefits from the joint inversion of direct and reflected arrivals, recorded both at the surface and in a well.
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Stochastic Inversion of Seismic Data by Evaluation of Pseudo-Wells
Authors B. Bril and P. De GrootA seismic inversion method is described based upon the ranking of realistic local subsurface models. Real wells and/or stochastically simulated pseudo-wells are scored at real seismic locations for seismic response and geostatistical probability. The resulting scores are analysed to yield both detailed local and generalised spadal information on geological and petrophysical subsurface properties.
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Statistical Reservoir Thickness Estimation
By A. G. SenaWith the increasing availability of 3D seismic data, good quality amplitude maps can be generated for prospective horizons. In interpreting these maps the quantification of how much pay is involved is essential and difficult to obtain. By analyzing reflection amplitudes from nearby well log data, a systematic analysis of the amplitude variation with respect to lithology, porosity, hydrocarbon pore fluid saturation, bedding geometries, and reservoir thickness con be carried out.
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Spatially Varying Wavelet in Seismic Inversion
Authors K. B. Rasmussen, H. Wagner and J. M. PedersenWith the introduction of relatively fast globally aptimized post-stack seismic inversion it is now possible to apply post stack seismic inversion of large seismic data volumes. Large seismic data volumes challenge the normal assurnption that a constant wavelet can be used to describe the relationship between acoustic impedance reflectivity and the seismic data for the whole tube. For this reason the determination and use of a spatially varying wavelet has been developed. It is presented below.
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A High-Order Pertubative Approach - Examples of Inversion
Authors A. Druzhinin and A. HanygaA common procedure in nonlinear seismic inversion involves least squares optimization (LSO) [6,8] implemented by various Newton type iteratie algorithms [4]. Recent papers [2,3] indicate that the highorder perturbations can overcome the problems of the LSO concerning initial guess, a priori information, CPU/acquisition costs, etc. The purpose of this paper is to show how such additional constraints can be incorporated into the available LSO algorithms without their special modification.
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Can we Image Complex Structures with Ray-Born Inversion?
Authors S. Xu, S. Operto and G. LambaréSummary not available
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GPR Theory and Simulation in 3D Realistic Media
Authors J. M. Carcione, F. Cavallini and M. SchoenbergThe increasing use of ground-penetrating radar (GPR) for solving a wide range of engineering and environmental problems has been pushed by the application of seismic standard techniques, such as multi-fold coverage and processing.
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Multisource Prestack Depth Migration - an Application of GPR Data
Authors M. Barsotelli-Botelho and I. MuftyThe method of reverse-time migration is widely know for high-quality results as well as extremely high computational colts.
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Filtering of Radargram-Traces with the Wavelet-Transform
Authors C. Seegraef and B. ForkmannGround penetrating radar measurements represent a relatively new, fast and high-resolution investigation method for near surface objects. To explain and to interpret phenomena occurring in nature preliminary investigations with synthetically made radargrams have to be done.
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Influence of Hydrogeologic Properties on the Dielectric Permittivity of Sand Cray Mixtures
Authors T. Heßland, E. Moise and P. SchikowskyPorosity, internal surface area, pore filling, grain size, and temperature have great influence on the velocity of propagation of electromagnetic waves in granular soil. Therefore we investigated these parameters in laboratory to estimate their relevante for field measurement with Ground Penetrating Radar (GPR). Furthermore we verified the applicability of a whole range of mixing formulae which are important for the computation of water content from the propagation vetocity of radar waves.
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Imaging Structures under a Steel-Reinforced Concrete Floor
Authors J. B. U. Haldorsen, D. E. Miller and F. GilbertWe had undertaken a study aimed at assessing the quality of images obtained with ground-penetrating radars (GPR). Using the commercial, impulsive pulseEKKO 1000 from Sensors & Software, and non-standard acquisition geometries, we had collected several 3-D datasets in a natural, suburban environment in Newtown, Connecticut. When approached by the building manager at our Ridgefield research center who needed to break open a floor in one of the workshops for the construction of a new elevator, we thought it a challenging opportunity, particularly considering the steel rebars we expected to find in the floor of the workshop.
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Cavity Identification with GPR Using Variable Offset and Antenna Orientation
Authors A. Helm and U. YaramanciIn GPR, exploration it is of major interest to identify reflector lithology directly using their reflection characteristics. Investigations have been made with simple reflectors especially on cavities in a mine in saliniferous surrounding. The detection of cavities is not only important for mine security but also for eliminating disturbances in the GPR section.
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Verification of Subsurface Pollution Barriers Using Ground-Penetrating Radar
Authors J. B. U. Haldorsen, F. Gilbert, D. E. Miller and L. PellerinDuring August 1997, a project organized by Lawrence Berkeley National Laboratory was carried out on the grounds of Brookhaven National Laboratory. The purpose of the project was to test the feasibility of controlling buried contaminants by injecting colloidal silica (CS) gel to form an impermeable barrier around the contaminants. Geophysical techniques such as ground-penetrating radar (GPR) may be used in an attempt to verify the structural integrity, extent and bulk hydraulic conductivity of a subsurface barrier.
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Induced Polarization Effects in Frequency and Time Domain Electromagnetic Soundings
Authors S. Krylov, N. Bobrov and B. WächterBoth frequency and time domain electromagnetic soundings are widely employed for solving various near-surface geotechnical problems. The experience of field work has shown that the results of soundings often can be distorted by the frequency dispersion of resistivity which is caused by induced polarization (IP).
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Using PRBS-Sequences as Source for TEM-Measurements
By S. L. HelwigThe transient electromagnetic method (TEM) is a well known tool to investigate the subsurface distribution of electrical resistivity
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