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69th EAGE Conference and Exhibition incorporating SPE EUROPEC 2007
- Conference date: 11 Jun 2007 - 14 Jun 2007
- Location: London, UK
- ISBN: 978-90-73781-54-2
- Published: 11 June 2007
81 - 100 of 574 results
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CRS Stacking – A Simplified Explanation
Authors J. Mann, J. Schleicher and T. HertweckB044 CRS Stacking – A Simplified Explanation J. Mann* (Geophysical Institute University of Karlsruhe) J. Schleicher (Dept. Applied Math. IMECC/UNICAMP Brazil) & T. Hertweck (Fugro Seismic Imaging Ltd) SUMMARY Stacking velocity analysis and stacking is usually performed within common-midpoint gathers. Generalized approaches like the Common-Reflection-Surface stack method additionally include neighboring common-midpoint gathers to fully exploit the redundancy in the data and to extract additional stacking parameters. In many publications the basics of the CRS stack are obscured by the uncommon parameterization. Our aim is to relate this often poorly understood approach to the established CMP-based approach in a simple and
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Multi-Scale Attenuation in Seismic Transmission Measurements Using the Wavelet Transform
Authors N. Filippidou, G. G. Drijkoningen and E. C. SlobB045 Multi-Scale Attenuation in Seismic Transmission Measurements Using the Wavelet Transform N. Filippidou* (Delft University of Technology) G.G. Drijkoningen (Delft University of Technology) & E.C. Slob (Delft University of Technology) SUMMARY We present a methodology that bridges the scale gap between ultrasonic acoustic measurements and VSP seismic measurements in terms of attenuation and dispersion. It is used to tie different datasets acquired at different frequencies and account for the scaling effects without compromising the fine scale information inherent in large scale measurements but often overlooked. The method is demonstrated on a synthetic velocity log with statistics of fractal Brownian motion.
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Seismic Attenuation Models for Partially Saturated Media
Authors B. B. S. A. Vogelaar and D. M. J. SmeuldersB047 Seismic Attenuation Models for Partially Saturated Media B.B.S.A. Vogelaar* (Delft University of Technology) & D.M.J. Smeulders (Delft University of Technology) SUMMARY Usually wave propagation in the presence of partial fluid saturation is modeled according to the White- Dutta-Odé (WDO) model which is based on the calculation an effective wave modulus of the saturated medium from a boundary value problem. We present here a new model that overcomes some disadvantages in that model by the definition of an effective bulk modulus of the fluid which includes gas bubbles according to the Smeulders-Van Dongen (SvD) model. This paper compares the frequencydependent
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Acoustics of Random Patchy Saturation
Authors J. Toms, B. Gurevich, T. M. Mueller and D. L. JohnsonB048 Acoustics of Random Patchy Saturation J. Toms* (Curtin University of Technology) B. Gurevich (Curtin University and CSIRO Petroleum) T.M. Mueller (University of Karlsruhe) & D.L. Johnson (Schlumberger-Doll Research) SUMMARY Mesoscale heterogeneities occur on a spatial scale which is greater than pore-scale but less than wavelength scale. The presence of mesoscale heterogeneities in saturating fluids within porous rock causes significant attenuation and phase velocity dispersion. In particular both contrast in fluid properties and spatial distribution of fluids significantly affects attenuation and dispersion. Thus patchy saturation models need to be flexible in order to account for both contrast and distribution effects.
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Solving Short-Wavelength Velocity Variations with High-Resolution Hybrid Grid Tomography
Authors M. Dazley, P. J. Whitfield, B. Santos-Luis, A. Sellars, P. Szabo, F. Nieuwland and L. LemaistreC001 Solving Short-Wavelength Velocity Variations with High-Resolution Hybrid Grid Tomography M. Dazley* (WesternGeco Ltd) P.J. Whitfield (WesternGeco Ltd.) B. Santos-Luis (WesternGeco Ltd) A. Sellars (WesternGeco Ltd) P. Szabo (WesternGeco Ltd) F. Nieuwland (Total E & P Nederland B.V.) & L. Lemaistre (Total S.A.) SUMMARY Short wavelength velocity variations are observed within the Cretaceous chalk in some areas of the Southern North Sea. Depth imaging is required because of the strong lateral velocity variations but building a suitable high-resolution velocity model is not easy. Here we present a case history of a pre-stack depth migration project where five overlapping surveys with
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Velocity Analysis in the Dip-Angle Domain
By M. ReshefC002 Velocity Analysis in the Dip-Angle Domain M. Reshef* (Tel Aviv University) SUMMARY When interval velocity analysis is carried out over complex geological regions the use of scattering-angle CIGs may cause significant inaccuracies. The reason for it is the summation over dip-angles which can eliminate information from the analysed CIGs. In this study the idea of performing the interval velocity analysis in the dip-angle domain is discussed and demonstrated with synthetic and field data examples. EAGE 69 th Conference & Exhibition — London UK 11 - 14 June 2007 Introduction The advantage of using common scattering-angle gathers as the output
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Subsalt Velocity Analysis by Combining Wave Equation Based Redatuming and Kirchhoff Based Migration Velocity Analysis
Authors B. Wang, F. Audebert, V. Dirks, J. Liu and P. ZhangC003 Subsalt Velocity Analysis by Combining Wave Equation Based Redatuming and Kirchhoff Based Migration Velocity Analysis B. Wang* (CGGVeritas) F. Audebert (CGGVeritas) V. Dirks (CGGVeritas) J. Liu (CGGVeritas) & P. Zhang (CGGVeritas) SUMMARY Due to the geometrical complexity of the typical Gulf of Mexico (GOM) velocity models with embedded salt bodies of any shapes wave equation migration is used preferentially over Kirchhoff methods for subsalt velocity model building. This preference is based on the ability of wave-equation based migrations to overcome the need for tracing complex ray paths through the salt bodies and for a better handling of multi-path arrivals
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Pre-Stack Depth Imaging Via Simultaneous Joint Inversion of Seismic, Gravity and Magnetotelluric Data
Authors D. Colombo and M. De StefanoC004 Pre-Stack Depth Imaging Via Simultaneous Joint Inversion of Seismic Gravity and Magnetotelluric Data M. De Stefano (Geosystem SRL) & D. Colombo* (Geosystem SRL) SUMMARY The problem of velocity model building for depth-imaging applications (i.e. Pre-Stack Depth Migration) is approached from the point of view of simultaneous Joint Inversion of multiple geophysical domains. For this purpose a general formulation of the joint inversion problem is provided which integrates geological constraints within a data-driven procedure. The method is then applied to synthetic (long offset) seismic data where seismic travel-time residuals (first-break and post-migration Common Image Gather residuals) are jointly inverted with
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Salt Interpretation Enabled by Reverse Time Migration
Authors J. Buur, J. Keating and T. KuehnelC005 Salt Interpretation Enabled by Reverse Time Migration J. Buur* (Shell International Exploration & Production) J. Keating (Shell International Exploration & Production) & T. Kuehnel (Shell International Exploration & Production) SUMMARY With the success of reverse time migration focus in the geophysical community has shifted towards the final frontier. How to build a velocity model which is accurate enough for imaging with advanced wave equation algorithms? We show that early utilization of reverse time migration in the model building loop can help to delineate complex structures in a salt diapir province offshore West Africa. EAGE 69 th Conference & Exhibition
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From Time to Depth Imaging – A Fast and Accurate Workflow
Authors P. Guillaume, G. Lambaré, P. Herrmann, J. P. Touré, L. Capar, N. Bousquié, D. Grenié and S. ZimineC006 From Time to Depth Imaging – A Fast and Accurate Workflow G. Lambaré (CGG) P. Herrmann (CGG) J.P. Touré (CGG) L. Capar (CGG) P. Guillaume* (CGG) N. Bousquié (CGG) D. Grenié (CGG) & S. Zimine (CGG) SUMMARY We present a new strategy for depth velocity model building from pre-stack time migrated gathers (PreSTM). It is based on dense volumetric dip and residual move-out picking in the PreSTM domain. The kinematic information is de-migrated to compute multi-offset un-migrated attributes - called seismic invariants - used as input data for a multi-offset depth tomography. Compared to the corresponding existing strategy based
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Imaging Beneath Shallow Gas Using Wave Equation Tomography – A Field Data Example from Greater Cassia, Trinidad
Authors M. M. N. Kabir, U. Albertin, M. Zhou, V. Nagassar, E. Kjos and P. WhitakerC007 Imaging Beneath Shallow Gas Using Wave Equation Tomography – A Field Data Example from Greater Cassia Trinidad M.M.N. Kabir* (BP America Inc.) U. Albertin (BP America Inc.) M. Zhou (BP America Inc.) V. Nagassar (BP Trinidad) E. Kjos (BP Trinidad) & P. Whitaker (BP Trinidad) SUMMARY Shallow localized gas pockets cause challenging problems in seismic imaging because of the sags and disturbances they produce on imaged reflectors deep in the section. In addition the presence of shallow gas produces strong surface related and interbed multiples making velocity updating very difficult. Usual reflection tomography techniques may need many iterations to
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Application of Anisotropic Velocity Modeling and Pre-Stack Depth Migration in the Deepwater Gulf of Mexico
By S. L. NealC008 Application of Anisotropic Velocity Modeling and Pre-Stack Depth Migration in the Deepwater Gulf of Mexico S.L. Neal* (Chevron) SUMMARY Seismic imaging in the Deepwater Gulf of Mexico (GoM) has been and continues to be a challenge for all phases of exploration and development. Although the presence of an anisotropic velocity structure has long been recognized it is only occasionally analyzed rigorously or integrated into seismic imaging. A significant challenge posed in the shift to anisotropic imaging is the development of stable and geologically robust workflows. Our anisotropic Pre-Stack Depth Migration (PSDM) workflow consists of three key steps: building the
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Wide Azimuth 3D 4C OBC – A Key Breakthrough to Lead to the Development of Hild Field
Authors D. Vaxelaire, K. Kravik, F. Bertini and J. M. MougenotC009 Wide Azimuth 3D 4C OBC – A Key Breakthrough to Lead to the Development of Hild Field D. Vaxelaire* (Total SA) K. Kravik (Total E&P Norge) F. Bertini (Total E&P Norge) & J.M. Mougenot (Total SA) SUMMARY Seismic imaging is a major challenge for some complex fields in the North Sea. That is the case for the Hild Brent field discovery (Total E & P Norge operator) not yet developed due to inconsistent dynamic data and poor seismic image resulting from a seismic obscured area created by gas dismigration strong energy multiples and a highly faulted reservoir. Conventional 3D
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Mult-Azimuth 3D Provides Robust Improvements in Nile Delta Seismic Imaging
Authors J. Keggin, W. Rietveld, M. Benson, E. Manning, P. Cook, B. Barley and C. PageC010 Mult-Azimuth 3D Provides Robust Improvements in Nile Delta Seismic Imaging J. Keggin* (BP) W. Rietveld (BP) M. Benson (BP) E. Manning (BP) P. Cook (BP) B. Barley (BP) & C. Page (PGS) SUMMARY After covering over 3000 sq km of the Nile Delta with Multi-Azimuth (MAZ) data we demonstrate how and why the technique improves illumination demultiple and lateral resolution. The technique is shown to be robust and reliable providing improved seismic images for exploration and development purposes. EAGE 69 th Conference & Exhibition — London UK 11 - 14 June 2007 Introduction Since gas was first discovered in
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Wide Azimuth Feasibility Study – Key Processing Considerations for an Optimum Design
Authors E. Ceragioli, A. Melois and P. HugonnetC011 Wide Azimuth Feasibility Study – Key Processing Considerations for an Optimum Design E. Ceragioli* (Total SA) A. Melois (Total SA) & P. Hugonnet (CGGVeritas) SUMMARY The Wide Azimuth technique represents a very promising approach for the optimal definition of complex geological targets particularly in sub-salt environments. Encouraging results are being observed from the first “at scale” application in the Gulf of Mexico. In order to deliver the full potential of this technique and maximise the benefit-to-cost ratio a rigorous and detailed feasibility study is absolutely necessary. We examine three key elements of such a study: the expected illumination improvements
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Effect of Structure on Wide Azimuth Acquisition and Processing
Authors B. J. VerWest, D. Lin, Z. Meng and S. NealC012 Effect of Structure on Wide Azimuth Acquisition and Processing B.J. VerWest* (CGGVeritas) D. Lin (CGGVeritas) Z. Meng (CGGVeritas) & S. Neal (Chevron USA) SUMMARY This model study shows that narrow azimuth acquisition may be adequate for structures which are oriented dip to the acquisition direction but strike components are not well imaged. Wide azimuth acquisition with sufficient cross line offset gives improved results compared to narrow azimuth acquisition for both dip and strike components since this method is actually “directionless”. Also 3D SRME on narrow azimuth data shot dip gives a good image but narrow azimuth strike data does
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Multiple Elimination on Wide Azimuth Towed Streamer Data by Extended Wavefield Extrapolation
More LessC013 Multiple Elimination on Wide Azimuth Towed Streamer Data by Extended Wavefield Extrapolation G. Xia* (BP America Inc.) & K. Matson (BP America Inc.) SUMMARY Wide Azimuth Towed Streamer (WATS) data provides a step-change in our ability to illuminate complex subsurface structures. The WATS data with rich diversity of azimuth and offset is effective at attenuating multiples – through simple stacking of post-migration image gathers. However the effectiveness of stacking degrades for exploration scale sampling. Moreover simple stacking precludes prestack analysis for velocity estimation and angle dependent amplitudes on the image gathers. Therefore it is desirable to develop better techniques
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Shot Based Pre-Processing Solutions for a WATS Survey – An Example from a Field Trial in Green Canyon – Gulf of Mexico
Authors J. -C. Ferran, M. Magesan, S. Kaculini, C. J. Faulkner, P. Herrmann, A. Pica, G. Poole and S. Le RoyC014 Shot Based Pre-Processing Solutions for a WATS Survey – An Example from a Field Trial in Green Canyon – Gulf of Mexico M. Magesan (CGGVeritas) J.-C. Ferran* (CGGVeritas) S. Kaculini (CGGVeritas) C.J. Faulkner (CGGVeritas) P. Herrmann (CGGVeritas) A. Pica (CGGVeritas) G. Poole (CGGVeritas) & S. Le Roy (CGGVeritas) SUMMARY In July 2006 a 3D Wide Azimuth Towed Streamer (WATS) field trial was carried out in a deep water area of Green Canyon in the Gulf of Mexico. The purpose was to provide insight into the potential problems and complexities of such seismic datasets and to challenge conventional and newly
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Stress and Seismic Anisotropy Near Salt Bodies – Numerical Modeling and Observation from Wide-Azimuth Marine Data
Authors R. Bachrach, M. Sengupta and A. SalamaC016 Stress and Seismic Anisotropy Near Salt Bodies – Numerical Modeling and Observation from Wide- Azimuth Marine Data R. Bachrach* (WesternGeco) M. Sengupta (WesternGeco) & A. Salama (WesternGeco) SUMMARY Wide-azimuth marine data enable us to observe and analyze the azimuthal response of marine sediments. Modeling the stress near salt bodies using realistic salt geometry and a finite-element solver we show that the presence of salt bodies cause changes in the orientation of the stress in the sediment near the salt. Thus horizontal stresses magnitude and direction may vary near salt bodies. We use third-order elasticity (TOE) theory to quantify the
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Interactive Seismic Imaging by Fast Beam Migration
Authors F. Gao, P. Zhang, B. Wang, G. Thomas-Collignon and V. DirksC017 Interactive Seismic Imaging by Fast Beam Migration F. Gao* (CGGVeritas) P. Zhang (CGGVeritas) B. Wang (CGGVeritas) G. Thomas-Collignon (CGGVeritas) & V. Dirks (CGGVeritas) SUMMARY This paper presents a Fast Beam migration algorithm which has been specifically designed to facilitate very rapid migration turnarounds to allow for interactive velocity model building and validation. The very fast imaging turnaround is achieved by only migrating pre-picked events in a wavelet by wavelet fashion. Coherent noise and migration artifacts are reduced compared to classical Kirchhoff migration techniques by using a sophisticated event selection scheme during the event picking phase and by subsequent multi-path
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