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57th EAGE Conference and Exhibition
- Conference date: 29 May 1995 - 02 Jun 1995
- Location: Glasgow, UK
- ISBN: 978-90-73781-06-1
- Published: 29 May 1995
1 - 20 of 562 results
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3D Prestack Depth Migration - an Aid to Development Drilling
Authors S. A. Whitney, C. More, D. W. Hawson and W. S. HarlanThe 3D seismic survey discussed here was acquired in 1991 and covers an area of 300sq kms of the UK, Southern North Sea. Accurate time imaging is not possible due to structural complexities and lateral velocity contrasts in the section above the target horizon (Leman Sandstone). Structural complexities in the overburden are formed by salt walls and associated Mesozoic graben systems which juxtapose fast, dipping, Cretaceous, chalk against slow, Tertiary, clastic sediments. Conventional time processing, including DMO and migration does not yield a clear, accurately positioned image, and occasionally, no image is formed at the target horizon. Recent advances in computer hardware permat computationally intensive prestack depth migration to be performed on a 3D volume (a 7km x 11 km subset of the original dataset) which can produce more accurate images if an appropriate velocity/depth model is applied.
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An Interactive Tool for Time and Depth Migration
Authors S. Kaculini and J. ArnaudDuring the seismic interpretation it is necessary to use data that are in different domains: the interpretation of seismic sections are often done in time migrated domain, the well data are in depth domain and in vertical time domain, etc . On the other hand, the final result must be in depth. So a great number of conversions from a domain into another must be done and the quality of the final result depends on the quality of all these conversions.
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Geostatistical Depth Conversion from Well and Seismic Data - a Case Study in a North Sea Field
By D. PsailaOne of the problems with the production of velocity maps for the purpose of depth conversion is that of data integration. Checkshot-derived well velocities, NMO-derived seismic velocities and seismic travel time information must be combined to produce consistent velocity estimates away from the wells.
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Interval Velocity Maps of the Danish Central Trough, North Sea
By P. JapsenInterval velocity maps in scale 1:200.000 of four major geological units in the Danish Central Trough, North Sea, are presented: the Post Chalk Group (Cenozoic excl. Danian), the Chalk Group (Upper Cretaceous-Danian), the Cromer Knoll Group (Lower Cretaceous) and the Upper Jurassic. The three first mentioned maps represent models based on well data and the structural configuration of the boundary layers determined seismically.
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3D Globally Optimized Seismic Inversion
Authors K. G. Maver, K. B. Rasmussen, J. M. Pedersen and I. AbatzisA globally optimized seismic inversion method is used for inversion of a 3D seismic data cube front the producing Dan Field, Danish Central Graben. As the inversion method is globally optimized no seismic interpretation is carried out prior to the inversion. Only 5 control parameters and the acoustic impedance log are used to setup the seismic inversion, The 1.400 by 1.525 km seismic data tube consisting of 3,416 traces is inverted from 1.6 to 2.2 sec. TWT. This interval covers chalk deposits and the seismic reflection pattem exhibits prominent lateral variation. The vertical well M-8x with both sonic log and density log is located within the datatube.
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A Seismic Reflection and Wide-Angle Study of Methane Gas Hydrates, Offshore Vancouver Island
Authors T. A. Minshull, G. D. Spence and C. R. FinkSeismic reflection profiles across many continental margins have imaged "bottom simulating reflectors" (BSRs), which are interpreted as marking the base of the methane hydrate stability field.
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Coupled P-P and P-SV Seismic Analysis of a Carbonate Reservoir, Alberta, Canada
Authors S. L. M. Miller, M. P. Harrison, D. C. Lawton, R. R. Stewart and K. T. SzataConverted-wave multicomponent seismic data provider complementary (P-P and P-SV) images of the subsurface for a relatively small additional cost, as conventional sources and receiver geometries are employed.
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Explosive Source 3D Seismic and its Impact on the Geology of the Selby Coalfield
Authors J. M. Holt, M. Elstob and C. RobsonWithin the Selby Coalfield, Yorkshire, UK, conventional 2D surface seismic surveying has determined the elements of the geological structure. These are large NE-SW trending faults of up to 130 m throw together with large E-W trending faults of up to 60 m throw. Faults with displacements down to 7 m have been successfully identified in position and throw. As mining proceeded a third element to the faulting was encountered. This comprised zones, up to 500 m wide and of some lateral extent, with complex normal and strike slip faulting. The vertical displacement is generally less than 5 m. These zones have been valled "shear zones" and because of their irregular shape and extent preclude mining over large areas.
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Stress-Dependent Elastic Wave Velocities in Shales
By C. M. SayersThe anisotropy of shales results from a partial alignment of anisotropic plate-like clay minerals. Slow sedimentation of clay minerals from dilute suspension favours face-to-face aggregation to foren `domains' of parallel clay platelets as shown in figure 1.
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Compound Effect of Inter-Layer Fluid Flow and Scattering on Attenuation in Finely-Layered Reservoir Rocks
Authors B. Gurevich, S. A. Shapiro and V. B. ZyrianovScattering due to fine lagering is known to play a major role in seismic attenuation. If the rock is also parous and permeable, additional attenuation can be caused by a flow of the pore fluid between lagers, a flow which is induced by the passing wave (White, 1983). In recent years both effects have been extensively studied theoretically and numerically.
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Spectrum Analysis of Pulse-Induced Acoustic Field in Jointed and Faulted Rock Formations
Authors A. O. Rozanov, V. N. Savel‘ev and S. A. StanchitsThe problem of determination of parameters of the elastic waves source in the fractured rocks is complicated by the presence of a variety of free surfaces. We study the influence of a structural element of jointed rock formation with specific site D close to the length a of the radiated pulse (a~D) on the initial field. In this work the problem turns into finding the spectrum of the natural vibrations of the solid of finite dimensions, and on extracting this one from the general spectrum of the recorded acoustic signal. It seems to be important for improving the spectral method for detecting the inhomogeneities with share boundaries and determining their dimensions.
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Monitoring the Widt of Hydraulic Fractures with Ultrasonic Measurements
Authors J. Groenenboom, A. J. W. Duijndam and J. T. FokkemaDuring hydraulic fracturing experiments in the laboratory the opening of hydraulic fractures is monitored with ultrasonic transducers. The experiment closely resembles seismic monitoring surveys in the field [MEADOWS AND WINTERSTEIN 1994, WILLS ET AL. 1942]. The extraction of information out of these experiments is critically dependent on the understanding of the elastodynamic behaviour of the thin fluid filled fractures. The laboratory experiments provide useful information on what determines the seismic visibility of these fractures, both for compressional and shear waves. The role of the fracture thickness or width on the elastodynamic response and a new method for monitoring fracture opening is investigated.
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Estimating Permeability from P- and S-Wave Velocities and Formation Resistivity Factor
Authors M. Nabi-Bidhendi and M. S. KingP- and S-wave velocities have been measured on several sandstones with different porosities and permeabilities under confining stresses to 60 MPa, white maintaining the pore pressure at 1 atmosphere.
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Spatial Up-Scaling of Isotropic Laboratory-Scale Geomechanical Parameters Resulting in Large-Scale Anisotropy in Layered Subsurfaces
Authors W. Zijl and I. RitsemaIn many cases, the mechanical behaviour of formations in situ is quite different from the behaviour observed in the laboratory when doing rock mechanical investigations on cores. If such a difference is the case, the laboratory data cannot be used in a finite element model for geomechanical analyses on large spatial stales.
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Near-Front Spatial Profile of Wave Impulses in Micro-Inhomogeneous Media
By V. RokAs it was observed and theoretically proved [1,2] the dispersion of sound in microinhomogeneous media is connected with relaxatian process that leads to equalizatian an additional thermodynamic parameter ξ that depends on wave pressure (or stress) differently in inclusions and host medium.
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Model-Based 3D Seismic Survey Design
Authors S. Slawson, K. Grove and D. J. MonkThis paper illustrates a new approach for both land and marine 3-D survey design. Reflection point data from 3-D model ray-tracing is used to quantify and optimize the illurnination resulting from 3-D geometries. Comparisons between the common midpoint (CMP) and modeled common reflection point (CRP) results are shown for a simplified demonstration model and for a salt diapir model.
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Monte Alpi 3D - A Unique 3D Survey in the Apennine Range, Southern Italy
Authors G. La Bella, L. Bertelli and L. SaviniThe survey covers a surface of roughly 200 Sq. Km. over the Morste Alpi oil field in the Apennine Range, Southern Italy, and represents a unique "Case History" for the peculiar aspects to be faced in the area of the operations. The first two factors are the very complex geologic setting and the rough morphological conditions. Other special characteristics were the severe operative conditions and the ecologically sensitive environment.
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Ground Roll and Polarization
Authors E. Kragh and L. PeardonSuppression of ground roll using multi-component polarisation filters is not a new idea, though the methods are far from standard practice. Why is this? The main advantage of polarisation filtering is the potential to use single geophones (necessarily multi-component) rather than long arrays which tend to attenuate high frequency signal.
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