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Geophysics of the 21st Century - The Leap into the Future
- Conference date: 01 Sep 2003 - 04 Sep 2003
- Location: Moscow, Russia
- Published: 01 September 2003
1 - 20 of 322 results
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Geovolume visualization and interpretation: speed and accuracy with auto-tracking
Authors T.M. Sheffield, T.E. Bulloch, D. Meyer and J. SuttonGeovolume visualization allows the geoscientist to examine many different interpretation possibilities for
every data set. However, to gain both speed and accuracy, interpreters must begin to utilize faster methods of
(seismic, reservoir characterization etc.) interpretations. Old methods of grid digitizing and interpolation are
too slow and inaccurate. New methods began in the 1980’s with trace-based autotracking, and in the 1990’s
voxel-based tracking gained momentum. The attribute-based methods of the 2000’s involve the combination
of multi-attributes and multi-samples with three-dimensional voxel tracking. This paper will compare and
give examples of these tracking techniques along with recommendations of when to use them.
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The structure of the Upper Triassic (Keuper) sequence based on the deep borehole data and interpretation of seismic lines within Glueckstadt Graben
Authors U. Bayer, Y. Maystrenko, N. Hoffmann, M. Scheck-Wenderoth and H. MeyerA detailed study of the structure and evolution of the Glueckstadt Graben (GG) shows
that the main phase of subsidence occurred during Late Triassic (Keuper) times. This
subsidence was strongly affected by Permian (Zechstein and Rotliegend) salt movement with
formation of very complicated structures of Upper Triassic sedimentary succession.
Furthermore, the deepest part of the GG partially formed as “rim syncline” at least within
southern part in Late Triassic. It is possible, that the Triassic GG an inherited structure from
Late Paleozoic (Early Permian).
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2D Reverse Tectonic Modelling along the DOBRE-2000 deep seismic reflection profile and its northern continuation in the Donbas Foldbelt, Ukraine
Authors Y. Maystrenko, U. Bayer, S. Stovba, R. Stephenson and A. Saintot2D reverse tectonic modelling was carried out to examine the results of the DOBRE-2000
deep seismic reflection profile and its northern continuation. The results of the palinspastic
reconstruction show that a crustal-scale pop-up structure provides a reasonable interpretation.
In addition, we present the evolution of the Donbas Foldbelt (DF) through time by 2D reverse
tectonic modelling. Tectonic modelling from the Late Devonian rifting to the Pre-Triassic uplift
was done taking into account two phases of salt tectonics which occurred during Early
Carboniferous.
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Petrophysical model of sedimentary rocks from Ruhnu borehole, Estonia
Authors A. Shogenova, A. Jõeleht, R. Einasto, A. Kleesment, K. Mens and R. VaherPhysical properties of 113 Estonian sedimentary rock samples from Ruhnu borehole were studied together
with their chemical composition and interpreted using correlation analysis. Stratigraphic sequence
represented by carbonate and siliciclastic rocks was deposited during eight sedimentary cycles. Studied data
set was subdivided into the six lithological rock groups, distinguished by chemical composition and rock
properties. Distinct correlations were obtained for limestones together with calcareous marlstones and for
dolomitized carbonate rocks (dolostones and dolomitic marlstones). Correlation coefficients were higher for
limestones with calcareous marlstones for porosity-dependent parameters. The lowest porosity and iron
content were in pure limestones. Primary porosity and iron content had high positive correlation with clay
content in the studied rocks. Secondary porosity was determined in the dolomitized carbonate rocks. The
highest porosity and the lowest density were measured in the silicicalstic rocks represented by sandstones
and siltstones. Porosity, density, P-wave velocity, electric resistivity, thermal conductivity and magnetic
susceptibility of dolostones were higher than of limestones. Obtained results may serve as a basis for
interpretation of geophysical, petrophysical and geological data in Estonia and for correlation of sedimentary
beds in the other parts of the Baltic sedimentary basin.
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Style and timing of salt tectonics in the Dniepr-Donets Basin (Ukraine) from seismic data
Authors S. Stovba and R. StephensonThe Ukrainian Dniepr-Donets Basin (DDB) is a Late Palaeozoic intracratonic rift basin, with
sedimentary thicknesses up to 19 km, displaying the effects of salt tectonics during its entire history of
formation, from Late Devonian rifting to the Tertiary. Hundreds of concordant and discordant salt structures
formed during this time. It is demonstrated that the variety of styles of salt structure formation in the DDB
provide important constraints on understanding the triggering and driving mechanisms of salt kinematics in
sedimentary basins in general. Specifically, syn- and post-rift regional extensional and compressional
tectonic events were very important mechanisms involved in the initiation of salt movements in the DDB.
Other geological processes were significant factors in the development of a variety of salt geometries once
salt flow had been triggered by tectonic disturbance of the unstable equilibrium between salt layers and their
overburden.
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Fundamentals of Seismicity Based Reservoir Characterization
Authors S.A. Shapiro and E. RothertProcesses of pore fluid substitutions or borehole fluid injections are typical for developments of hydrocarbon
or geothermic reservoirs. Microseismicity occurring during such borehole fluid injections or extractions has
a large potential in understanding of physics of the seismogenic process as well as in obtaining detailed
information about reservoirs at locations as far as several kilometers from boreholes. Here we introduce a
concept for interpretation of microseismic data which provides a possibility to infer an information about
hydraulic properties of rocks. Estimates of hydraulic diffusivity tensors on large spatial scales as well as
imaging of its distributions in space resulting from this concept can be of significant importance for industrial
applications and understanding of physical properties of geological structures.
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Utilising information from VSP data to improve reservoir characterisation
Authors M. Urosevic, A. Gerhardt and K. DoddsIn this work we use VSP data to help solve practical exploration problems. In particular, we show how VSP
data can be used to quickly assess the response of various seismic attributes. Specifically, we use downgoing
energy to evaluate and relate anomalous behaviour of seismic attributes to changes in effective stress.
Selected attributes are then computed on up-going VSP energy using later arrival times and, if sensitivity
with respect to changes in effective stress is retained, they are subsequently computed on surface seismic
data. Such simplified VSP-based analysis enables quick and efficient qualitative assessment of variations in
lithology, geo-pressure, or other rock properties under investigation. We also discuss how multi-offset VSP
data can be used to speed up pre-stack depth migration (PSDM) of surface seismic data in areas where
anisotropy is non-negligible and typically not fully defined.
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Application of geophysical methods to the investigation of the Enguri dam (Georgia), in the frame of the Georgian-Italian cooperation Project
Authors M. Piccolo, D. Nieto, I. Noniev, N. Sulkanishvili and G. AbusashviliThe Enguri dam is situated in the Enguri River in the west part of Georgia and is the largest arch
dam in the world. The structure is 271,5 m tall, 750 m wide, the dam body has a volume of 4 millions of
cubic meters and the volume of the basin is about 1,1 billions of cubic meters, it is linked to a high pressure
tunnel with a diameter of 9,5 meters and a length of 14,5 km and is equipped with 5 x 275 MW generators
unit, Francis type.
The construction started in the late 70’s and the dam entered in temporary operation in the year 1978 and was
finished in the year 1987.
The dam crosses a valley formed by fractured limestone and interested by an important fault, the area has
also a seismic activity.
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Frequency-Power-Law Attenuation - Scattering by Fractal Inclusions
Authors V. Rok, A. Druzhinin and R. EvansWe have investigated wave propagation in chaotic structures of fractal geometry with random
spatial variation. Specifically, we have examined simple closed-form solutions in fractal poroelastic
media. These solutions may be characterized by their frequency-power-law (FPL) signature caused
by wave dispersion and attenuation. Numerical results show that the fractal dimension can be
estimated from the FPL dependence of the scattered wavefield. It appears that finite-bandwidth
signals are delayed with respect to the wavefront in comparable elastic media.
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Dispersion and attenuation of P-waves in porous rocks with aligned fractures
Authors M. Brajanovski and B. GurevichFractures in a porous rock can be modeled as very thin and highly porous layers in a porous background. Elastic moduli of a porous rock permeated by a system of such fractures distributed periodically can be obtained using the result of Norris (1993) for elastic properties of layered poroelastic media. When both pores and fractures are dry, such material is equivalent to a transversely isotropic dry elastic porous material with linear-slip interfaces. When saturated with a liquid this material exhibits significant attenuation and velocity dispersion due to wave induced fluid flow between pores and fractures. The characteristic frequency of the attenuation and dispersion depends on the background permeability, fluid viscosity, as well as fracture density and spacing.
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Seismic signatures of patchy saturation in poroelastic structures
Authors B. Gurevich and T.M. 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Shell’s Experience with 4D Seismic Monitoring and new Directions
By R. Calvert4D seismic monitoring has become a near standard practice within Shell for field
management. We find that conventional seismic survey techniques need to be updated
for improved seismic repeatability, which is the key to being able to see small field
production related changes. Seismic surveys with sparse sea-bed receivers is one way we
expect to get better, faster and affordable results whenever needed.
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Induced polarisation method (Time domain) in hidden bauxite deposits exploration
Authors N. Trifunovic, V. Kecojevic and S. Komatina-PetrovicThis paper shows the results of the induced polarization method (IP) in time domain (2 sec. time interval) and
resistivity method (RM) in finding hidden bauxite deposits in the area of Stitovo near Niksic (Montenegro).
Theoretical basis of the IP method is given, as well as methodological and technical data of the geoelectric
method applied, and electrodes array for the field measurements.
Results obtained through interpretation of acquired and processed IP and RM parameters are presented. In the
paper, results of exploration of some other ores performed from 1980 to 2002 are also presented. At the end, we
have drawn important conclusions concerning IP and RM method application together with decay curve
analysis.
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Role of enormous changeable earth magnetic fields (CEMF) intensities in etiopathogenesis of mental disturbances and illnesses (MDI)
Authors N. Trifunovic, D. Nikolić and S. Komatina-PetrovicAim of this paper is contribution to MDI etiopathogenesis appeared under the influence of enormous CEMF
intensities and explanation of central nervous system (CNS) operation from knowing the effect of natural
physical fields on evolution of living world and CNS operation aspect. Correlation between enormous CEMF
and MDI was determined. Effect of enormous CEMF zones upon CNS had been revealed, and then the diseased
was moved away from the enormous zones influence. Synthesis of two data groups was made. Processing the
first data group correlation between present enormous CEMF zones and CNS of the diseased was determined.
The second data group is theoretical explanations of unclearness found in literature concerning CNS from
knowing the CEMF aspect. Coincidence of practical measuring results and theoretical explanations of almost all
unclearness from the literature on CNS was determined.
It was concluded that enormous CEMF are the main cause of MDI appearance and that moving the diseased
away from enormous zones is a great help to the patient and his doctor in treatment.
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Using rock physics for pseudo well log construction
More LessQuantitative analyses of seismic using well logs require two sets of data, none of which are
usually available: dipole sonic logs, due to cost and velocity and bulk density logs in the
shallow part of the holes, due to large holes.
In this abstract, we present a general rock physics based technique for constructing
pseudo-logs. The pseudo-shear sonic log is based on the work by Dutta & Wendt’s (1993).
The shallow pseudo-logs for P-velocity and density are based on mechanical compaction
theory and rock physics based velocity-porosity relationships. We test the technique on well
log data in the Gulf of Mexico.
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Lithocube Analyses with Uncertainty using Rock Physics, High Resolution Seismic and Bayesian Classification Scheme: Applications to Clastic Basins
Authors R. Bachrach and N. DuttaA successful seismic based lithology prediction effort depends on reliable rock physics
transformation from seismic attribute space into the lithology space. This problem is non-unique and
thus uncertainty associated with the different predicted lithologies and fluids (i.e. confidence interval
and estimate of misclassification probability) should be addressed. We address the problem using rock
physics relationships in conjunction with well known statistical tools and Bayesian Classification
technique to characterize various lithofacies and fluids in subsurface. Our final output is most likely
lithology unit, with most likely fluids and the probability associated with it. The procedure is
illustrated with examples from clastics basins.
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Determination of Anisotropy Parameter G (Delta) using CMP Gathers and Application of Anisotropy NMO in Seismic Processing
By S.N. MohantyAnisotropy in rock layer is manifested in seismic data as anomalies in travel time, waveform
and amplitudes. Seismic wave travels generally in anisotropic medium, as the earth is
fundamentally anisotropic, but most of the processing algorithms assume the ideal condition of
isotropy. This faulty assumption leads to erroneous imaging and thus wrong interpretation. The
anisotropy is hidden inside the hyperbolic moveout velocity and moveout looks hyperbolic, even
though the layer is aniosotropic. Incorporation of velocity anisotropy in routine processing
improves the character of the reflector with proper focusing of amplitude and provides more
geological meaning to acoustic impedance and different attributes. Better accuracy, higher
resolution, wider spread length and improved ties between seismic and log require understanding
and application of anisotropy, if conflicting results of the routine processing and interpretation
objectives are to be reconciled. Hence, in many situations it becomes necessary to include the
effect of anisotropy for obtaining correct images and rock properties from seismic data.
Thomsen (1986) derived equations to account for anisotropy and these simplified equations
are widely used for solving important seismological problems effectively in anisotropic medium.
The purpose of this study is to estimate the Thomsen’s anisotropy parameter d(Delta), for
transversely isotropic medium from common mid point gather. Here, we describe a new approach
for determination of d(Delta) based on optimum moving window velocity analysis within
common mid point gather for different offset ranges to extend anisotopic normal move out
correction in processing steps. Further, parameters,d(Delta), are calibrated at well to resolve the
depth uncertainties. We shall demonstrate our technique and show the results from a field data set
from Cauvery basin, Southern India.
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Seismic upscaling of layered anisotropic media
Authors A. Bakulin and V. GrechkaAll measurements of anisotropic coefficients in exploration seismology are made over finite volumes of inevitably
heterogeneous rocks and, therefore, represent some effective values. As a result, a geophysicist often needs to estimate
how unaccounted heterogeneity influences (or biases) the estimates of anisotropy. We show that this influence is
usually weaker than one might think.
In particular, we demonstrate that the difference between any effective quantity me and its arithmetic average ¯m
over a given volume is always quadratic in the local fluctuations ˜m, i.e., me ¡ ¯m = O( ˜m2). We prove this statement
under quite general conditions that have mathematical nature rather than express specifics of a given quantity m.
To verify our theoretical findings, we perform Backus- and Dix-type averages of a typical well log intentionally
“contaminated” by moderate anisotropy.
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Induced polarization spectra of sands and clays measured in the time domain
Authors A. Tarasov, K. Titov, M. Münch and A. KemnaTime domain induced polarization (IP) responses of pure clay, pure sieved sand, and two sand
mixtures were measured and inverted to relaxation time distributions (RTD) and pore characteristic length
distributions (CLD) representing IP spectra. For the clay the CLD was found to be similar to the pore size
distribution obtained on the basis of scanning microscope imaging. For the sand mixtures the CLD was
found to be sensitive to the proportion of particles of different sizes. In both cases the form of the CLD is
practically independent of water conductivity.
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The Drive for Better Bandwidth and Resolution
By M.S. EganThe drive for better bandwidth and resolution has been a priority since the early days of the seismic method.
Evolutionary strides have been made continuously, but especially in the last few years quite a number of
advancements have been introduced. These span all segments of the seismic industry. This paper reviews
those recent advancements from the standpoints of the strategies involved and their associated enabling
technologies.
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