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EAGE/SEG Research Workshop 1990
- Conference date: 15 Jul 1990 - 18 Jul 1990
- Location: Cambridge, UK
- ISBN: 978-94-6282-136-1
- Published: 15 July 1990
41 - 60 of 69 results
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Petrophysical interpretation of P- and S-wave velocities
By M. KriefIt has been observed that, in the case of a clean, homogeneous formation, points on a cross-plot of the squares of the P and S-wave sonic velocities fall along a straight line when the porosity is changing.
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Laboratory measurements and applications of seismic velocities
By Z. WangLaboratory measurements of seismic velocities play an important role in understanding seismic wave propagations in reservoir rocks. These seismic velocities are widely used in seismic data processing, correlations of seismic stratigraphy, seismic and weIl logging interpretations, lithology identification, and most recently in reservoir description and surveillance. In order to make fuIl use of the seismic velocity data, we must understand relationships between seismic velocity and a variety of reservoir and physical parameters.
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Estimates of velocity dispersion between seismic and ultrasonic frequencies
More LessVelocity dispersion in rocks is a pervasive, yet poorly understood, aspect of exploration geophysics.
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Velocity and absorption in sedimentary rocks at seismic and ultrasonic frequencies
Authors R. Mörig, R. Schütt and H. BürkhardtVelocity and attenuation of seismic waves are of great potential use in deducing lithological parameters from seismic data if we understand the physical laws governing dissipation of seismic energy and the accompanying velocity dispersion.
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Effects of grain-scale pore fluid flow on velocity dispersion in rocks
More LessDispersion in fluid saturated rocks appears to be dominated by two mechanisms: large scale average motion of the fluid phase relative to the solid phase, analyzed by Biot, and local grain scale relative motion.
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Static and dynamic properties of sandstones
More LessUsing laboratory measurements, we investigate the relationship between static and dynamic bulk moduli in 43 tight gas sandstones with porosity ranging from 2 to 14 percent and clay content ranging from 0 to 66 percent. Dynamic moduli are computed using compressional and shear velocities measured on the sandstones in air-dry condition.
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Pore-filling material and its effect on velocity in rocks
More LessA method is proposed to estimate the dependence of P and S velocities in rocks on elastic properties of the pore-filling material. The method goes beyond Gassmann 's relations in that it can account for saturating materials with nonzero shear stiffness.
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Theoretical modelling of the impact of free gas on seismic velocities
By E. FjaerSediments at the sea bottom of ten contain gas - normally methan, nitrogen or carbon dioxide (see f.i. Wheeler, 1986, Boden 1987). The presence of gas in a sediment affects its mechanical properties, and may thus have an impact on the stability of oil platforms resting on the sea bottom. Also, pockets of gas may cause dangerous situations during oil drilling, especially if the driller is not prepared for it. Seismic data often represent the only available information from the sediment prior to planning of platform sites, and drilling. Thus, it is important to be able to decide from the seismic data - with largest possible certainty - whether a sediment contains gas or not.
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Inversion of seismic velocities for rock- and pore parameters
Authors G. J. M. Lörtzer and A. J. BerkhoutThe ultimate result of the inversion of (surface) seismic data is in terms of rock and pore parameters, together describing the lithology.
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Pore structure mapping and permeability prediction prediction from velocity measurements
Authors S. Xu and M. S. KingKnowledge of perrneability of in situ rocks is of great importance in studies of nuclear waste disposal, underground water movement, petroleum and geothermal energy exploitation from reservoirs and in civil engineering applications such as dam constructions. Great difficulties have been experienced in predicting permeability of in situ rocks because of the limited information on discontinuities of all scales and of the pores of rocks, which together contribute to the permeability.
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Porosity and lithology estimation from elastic rock parameters
Authors M. L. Greenberg, W. J. Lamb and J. P. CastagnaA suite of 456 rock property laboratory measurements were used in the forward sense to calibrate a velocity response model and in the inverse sense to assess model resolution. The laboratory data support an approximately linear relation between velocity and porosity in relatively pure sandstones, limestones and dolomites. To first order, velocity of a Iithologic mixture is the volume-weighted linear combination of velocities of the pure, porous end-member lithologies. This velocity response model is superior to Wyllie's time-average equation, in which solid grain properties are mixed prior to accounting for porosity.
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Shear-wave investigations of the sea floor
Authors Fr. Theilen and I. PecherShear wave investigations of the sea floor in combination with conventional reflection seismic measurements yield information on the subsurface structures as well as on the elastic muduli of the sediments.
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3D Depth migration
Authors J. W. M. Dankbaar and E. B. J. KleissThe continuing increase in CPU capacity of modern computers has brought 3-D depth migration within the reach of geophysicists. Crux to a successful result is an accurate 3-D velocity model. A strategy to construct 3-D depth models is discussed and the impact of 3-D depth migrations is demonstrated.
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Steep-dip time migration and residual depth migration
Authors M. A. Brzostowski and J. L. BlackCommon practice is to perform steep-dip time migration followed by an image-ray correction. This paper examines the image-ray correction and finds it lacking. In particular, this correction is valid only for the small-dip portion of the migrated image.
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Migration velocity in areas of irregular topography
Authors C. J. Beasley and W. LynnSummary not available
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Utilization and integration of well and seismic velocity data for accurate multilevel depth conversion, northern U.K. southern gas basin
By J. M. ReillyThe subsurface velocity field in the northern portion of the U.K. Southern Gas Basin is complicated by the presence of (Permian) Zechstein salt swells and diapirs. In addition, the post-zechstein (post-Permian) section displays large lateral velocity variations.
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Interval-velocity studies in the Southern North Sea
By G. BrownInterval velocities have been derived from a dense grid of non-exclusive seismic data in the Southern Gas Basin of the North Sea. The analysis of around 8000 velocity spectra has enabled detailed interval velocity maps to be drawn down to Top Zechstein level. A comparison of the seismically derived velocities with known well-derived velocities indicates that in most circumstances the "Dix" interval velocities are a good approximation to the well velocities - particularly for the Tertiary and Upper Cretaceous Chalk intervals. Consequently, the interval velocity maps so derived are useful for the purposes of depth conversion. In addition , these maps reveal interesting trends and anomalies many of which can be interpreted as having distinct geological causes. This poster paper concentrates on the interpretation of velocity anomalies in the Upper Cretaceous Chalk.
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How to find the best possible velocity functions for time-depth conversion
More LessLarge sums of money and lots of time is put into seismic acquisition, processing and interpretation to obtain the best possible results. From these seismic interpretations, with the use of sophisticated gridding contouring and mapping software, finally depth and isopachmaps are produced on which basis expensive drilling deelslons will be taken.
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