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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 - 50 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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Three-dimensional Inversion of Sea-Bottom MT Data for Petroleum Exploration
Authors M.S. Zhdanov and L. WanWe investigate the feasibility of sea-bottom MT observations for petroleum exploration. The
resistivity of petroleum reservoirs and of salt structures is usually on an order greater than those
of surrounding sea-bottom sediments. That is why these structures can be considered easily
detectable targets for marine MT methods. We consider the schematic model of an offshore
Angola sea-bottom petroleum reservoir. The 3-D inversion results show that even in the case of
complex sea-bottom geological structures, where the reservoir response is strongly distorted by
the salt dome effect, the inversion generates a clear image of the reservoir. These results
demonstrate that the sea-bottom MT survey can be a powerful tool for offshore petroleum
exploration.
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PS-wave azimuthal anisotropy: benefits for fractured reservoir management
Authors J.E. Gaiser and R.R. VanDokFractured reservoirs have been encountered worldwide and in general they are profitably produced, however
it is safe to say that none of them have been depleted efficiently. As the seismic industry focuses more on
production and development it is becoming more important to recognize the presence of fractures for optimal
reservoir management. Fractures can significantly influence the behavior of reservoir porosity and
permeability, resulting in numerous dry wells and higher production costs. A key strategy for fractured
reservoir management is a quantitative description of the geology, geophysics and petrophysical attributes.
3D converted-wave (PS-wave) surveys provide complimentary surface-seismic information to help identify
fracture properties early in the production history of a reservoir. Based on azimuthal anisotropy
measurements, PS-waves indicate fracture density and strike, and because of their asymmetry they are also
sensitive to fracture dip. These large-scale properties will be critical for solving specific production problems
associated with different fractured reservoir types, and could improve reservoir modeling: production-history
matching, and fluid-flow simulation. From an economic point of view, if multicomponent surveys prevent a
small fraction of unproductive wells, then they are worth the expense.
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First arrival picking using image processing methods
Authors C.J. Criss, R. Kappius and D. CunninghamA new methodology for picking refraction arrivals is proposed for the purpose of automatic and
accurate picking of large volumes of first break picks for refraction static analysis or geometry quality
control. Raw or processed shot records are processed through a conversion method that creates a
binary raster image that focuses the anomalous amplitude associated with the first arrival. Analysis has
demonstrated that this method can be robust with many types of data including those with large time
variances in the first arrivals due to elevations changes or near surface statics. The method is also
independent of the offset information for the traces so first arrival picking can be accomplished
independent of the geometry definition, and the resultant picks are ideal for traditional geometry
analysis methods.
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Integrated Crosswell Seismic – A new Technology for Reservoir Management - Case Histories
Authors M. Antonelli, F. Miranda and L. TerziIntegrated Crosswell Seismic (ICS) is set of innovative techniques - devised and proposed to characterize the
internal structure of a reservoir - that is now evolved from being primarily an exploration tool to a
development and production tool.
This paper gives a few examples of such an evolution, presenting the results of some ICS applications that
Eni has carried out on its operated producing oil fields - located in Italy and oversea – as a part of a
continuous R&D effort for improving the reservoir characterization process.
The case histories here presented show how this methodology worked in reservoirs of different lithologies
and geological frameworks, and prove how its high flexibility and applicability can substantially assist the
reservoir management in providing important information for:
♦ a higher resolution structural & stratigraphic imaging;
♦ a better well-to-well log correlation;
♦ the building and validation of the geological models;
♦ the estimation of petrophysical properties and the detection of flow barriers;
♦ the identification of “infill” drilling targets (e.g. for planning horizontal wells);
♦ the time lapse monitoring and imaging of the fluid flow.
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Permanent Downhole Seismic Sensors in Flowing Wells
More LessIt is generally accepted that the ‘Oilfield of the Future’ will incorporate distributed permanent
downhole seismic sensors in flowing wells. The effectiveness of these sensors will be limited by the extent to
which seismic signals can be discriminated, or de-coupled, from flow induced acoustic noise originating
within the production tubing,
A specialised test facility has been developed in order to understand and characterise the acoustic
noise generated by fluid flow within a production borehole, with the goal of developing the next generation
of seismic tools suitable for permanent deployment in flowing wells.
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Generation and processing of pseudo shear-wave data: Theory and case study
Authors V. Grechka and P. DewanganProcessing of converted (PS) waves currently adopted by the exploration industry is essentially based on resorting
PS data into common conversion point gathers and using them for velocity analysis. Here we explore an alternative
procedure. Our key idea is to generate the so-called pseudo-shear (ªS) seismograms from the recorded PP and
PS traces and run conventional velocity analysis on the reconstructed ªS data. This results in an effective S-wave
velocity model because our method creates the data that possess kinematics of pure shear-wave primaries. Since we
never deal with such complexities of converted waves as moveout asymmetry, reflection point dispersal, and polarity
reversal, these generally troublesome features become irrelevant.
We describe the details of our methodology and apply the developed processing flow to a multicomponent ocean
bottom cable line acquired in the Gulf of Mexico. Since the obtained stacking velocities of P- and ªS-waves indicate
the presence of effective anisotropy, we proceed with estimating a family of kinematically equivalent VTI (transversely
isotropic with a vertical symmetry axis) velocity models of the subsurface.
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Inversion of multi-component, multi-azimuth, walkaway VSP data for the stiffness tensor
Authors P. Dewangany and V. GrechkaVertical seismic profiling (VSP) is an established method for estimating in-situ anisotropy that might provide
valuable information for characterization of reservoir lithology, fractures, and fluids. The P-wave slowness components,
conventionally measured in multi-azimuth, walkaway VSP surveys, allow one to reconstruct some portion of
the corresponding slowness surface. A major limitation of this technique is that the P-wave slowness surface alone
does not constrain a number of stiffness coefficients that may be crucial for inferring certain rock properties. Those
stiffnesses can be obtained only by combining the measurements of P-waves with those of S (or PS) modes.
We show that, when polar and azimuthal coverage of the data is good, the polarizations and slownesses of P
and two split shear (S1 and S2) waves are sufficient for estimating all 21 local elastic stiffness coefficients cij that
characterize the most general triclinic anisotropy. The inverted stiffnesses themselves indicate whether or not the data
can be described by a higher-symmetry model. We discuss three different scenarios for inverting noise-contaminated
data and then apply our methodology to a multi-azimuth, multi-component VSP data set acquired in the Vacuum
Field, New Mexico, USA. Our inversion indicates that the medium at the receiver level can be approximated by an
orthorhombic model.
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Experimental study on wave propagation in a borehole intersected by a finite vertical fracture
Authors F. Henry, C.J. de Pater and J.T. Fokkema����������������������������������������������������������������������������������������������� � ��������������������������������������� � ����������������������������������������������������������������������������������������������� � �������� � ���������������������������������������������������������������������������������������������������������������� ������� ������� ���� ������� ��� ������������� ���������������� ��� ���������� ���� �������� ��� ����� ����������� ����� ������ ��� ��� ����� ��������� ��������� ���� ���� ������� ���������� ��� ����� ��� ���� �������� ���� ������� ��� �� ��������� ������� ��������� ��������� ��� ��������� ����� ������������ ���� ��������� ���� ������������ ����� ���� ���� ��� ���� ��������� ��������� ���� ��� ��������� ��� �� ������������ ���������� ��� ���� ��������� ����� ����������� ���� �� ������� ���������� ���� ��������� ����� ���������� ��� ����� ����������� ����� ���� ��� ����� ��������� ���������� ��������� ���� ������������ �������� ������� ����� ��� ���������� ���
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Leaping to 21st Century Geophysical Volumes: Case Studies in Hierarchical Project Content Management
By J.B. KozmanExplorationists are discovering that the explosive growth of geophysical data in the 21st century requires
new paradigms in data management strategies. As the number of versions of geophysical volumes grows
exponentially, storage systems are overwhelmed by demands for disk space. Disks are continuously full,
backup windows interfere with interpretation workflows, users become responsible for data management,
and geophysicists use their time looking for data instead of looking for hydrocarbons. Hierarchical
content management, in which geophysical project files are managed according to their usage patterns,
alleviates these problems and returns value to exploration and production project life cycles.
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Some properties of fundamental acoustic modes when logging while drilling
Authors J. Market and D.P. SchmittThe properties of the fundamental modes generated by acoustic monopole, dipole and quadrupole sources
in the LWD environment are reviewed in the presence of homogeneous slow isotropic formations. The
techniques that can be used to determine the formation shear wave velocity are also discussed. For dipole
data, interference between the formation and tool signals requires the inversion of the mode velocity at
intermediate frequencies. The reliability of such process increases with decreasing formation shear wave
velocity. The fundamental quadrupole mode phase velocity starts with the formation shear wave velocity at a
cut-off frequency at which very little energy is present and then decreases toward the Scholte velocity, like
the flexural mode. Such features may require a dispersion analysis/correction depending on the fluid annulus
thickness and the signal to noise ratio in the low frequencies.
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Geological-Geophysical Model Of Suplacu de Barcau Oilfield
Authors N. Pandele, G. Susanu, C. Balanean, M. Farcas, A. Leparda and V.F. SabauIt has become extremely important in recent years to do a better job in well planning to ensures that
well cost estimates and drilling programs are as complete and accurate as possible. Comprehensive well
programs and realistic estimates are nescessary to determine which drilling prospects are most attractive
considering current upstream economics.
Pore pressure analysis is the initial and in most cases, the most important step in developing an
accurate, complete well program. Casing setting depths, hole sizes, number of casing strings, mud programs
and hydraulics, are examples of items in a well program which are influenced by the pore pressure profile
determined for a well. Pore pressure analysis is especially critical for exploratory and delineation wells but
until recently our predictive techniques were somewhat inadequate.
This paper will present general survey of the application of the log and core techniques well prior to
drilling and the applications and the results in productivity, also temperatures distribution in the Suplacu de
Barcau field during the combustion process.
As a general introductory we can say from the historically point of view that the degree of
knowledge of geological structure of Pannonian Basin, (where the Suplacu de Barcau field is situated), it is
due to the geological and geophysical prospects, and to exploration works which had been performed in this
unity.
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An object driven approach to analyze geological objects in high-resolution seismic data
Authors I.R. Rabelo and S.M. Luthi���������������������������������������������������������������������������������������� � ��������������������������������������� �� � � �������� �������� �� ����������� ��� �������� ������ �������������� ����������� ��� ������������ �������� ��� ������ ���������������������������������������������������� � �������� � ������������������������������������������������������������������������������������������������������ ��� ����������� ���� ��� �������� ��������������� ���� ������ ���� �������� ��� �������������� ��������� ���� �������������� ��� ���������� ������������ �������� ������ ����� �������� ������������ ��� �� ����������� ������� ��� �������������� ��� �������� �� ������������������ �������� ����� ���� ����� ���� �� ����������� �������� ����� ���� �� �� �������� �������������������������������������������������������������������������������������������������������� ��������� ����������� �������� ����� ��� ���������� �������� ������ ��� ����������� ��������� ���������� �������� ������������������������������������������������������� � ������������� � ������������������ ����� �������������� ��� ����������� ������� ����� ���������������� �������� ����� ���
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Estimation of Abnormal Pressures zones on the basis of seismic. Case study of carbonate reservoirs.
Authors H. Jędrzejowska, Z. Herman and R. HermanThe aim of this paper is to present the application of seismic inversion and time to depth conversion for prediction of overpressure zones in geological media. Contrary to conventional approach we do not used V NMO or V RMS analysis. Results play an important role in the absence of well information and can help in risk reduction while drilling.
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Frequency dependent anisotropy in saturated porous rocks with aligned fractures
Authors L. Brown and B. GurevichPorous rocks with aligned fractures exhibit frequency dependent seismic anisotropy due to wave induced
fluid flow between pores and fractures. To model this frequency dependent anisotropy, we combine the low
frequency anisotropic Gassmann model with the frequency dependency from a penny shaped crack model.
Predictions of the anisotropic Gassmann model, and the combined frequency dependent model, are compared
to angular dependent wave velocities measured on a synthetic porous sample with aligned cracks. For the
saturated sample, the anisotropic Gassmann model predicts qualitatively accurate velocities, but P-wave
anisotropy is overestimated by approximately 25%. This discrepancy can be explained by the low frequency
assumption of the anisotropic Gassmann model, which does not account for fluid diffusion effects occurring
at the relatively high frequencies used in the experiment. The combined frequency dependent model accounts
for fluid diffusion effects, resulting in excellent agreement for predicted P- and S-wave velocities.
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MEMS for Geophysicists
Authors D.J. Tessman, B. Reichert, J. Marsh, J. Gannon and H. GoldbergInput/Output, Inc. has developed a MEMS accelerometer
to use as a seismic sensor for oil and gas exploration.
Currently, moving coil inductive geophones are used as
seismic sensors. Geophone design and performance have
evolved for more than 50 years to the point that modern
geophones are small, rugged, highly sensitive to motion,
and produce minimal background noise. Achieving
performance superior to a modern geophone with a
MEMS accelerometer has been a significant technical
challenge, but other benefits enabled by MEMS and
accelerometer technology, such as direct digital output at
the sensor, inherent high vector fidelity, and superior lowfrequency
response, justify the effort.
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Microseismic Monitoring of Hydrocarbon Reservoirs
More LessThis paper demonstrates how microseismic activity in the reservoir can be used for continuous 3D
time-lapse monitoring of hydro and geo-mechanical processes occurring in the interwell region and assist in
the reservoir management process.
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3D/4C EMILIO: A multi-component survey for fractures characterization
Authors L. Vetri, J. Gaiser, E. Loinger and H. LynnThe Emilio 3D/4C ocean bottom cable survey in the Adriatic Sea was designed to acquire wideazimuth
data and processed to detect azimuthal anisotropy for fracture characterization in the carbonate
reservoir. Exploiting the high and uniform fold of coverage in each offset and azimuth range, separate
volumes for the different wave-field propagation directions were produced: four PP-wave and sixteen PSwave
restricted azimuth datasets. Valuable anisotropy information was derived from pre- and post-stack
analysis of all these volumes. Analysis of PP and PS amplitudes and results of PS layer stripping at the target
were crosschecked to bore-hole information and well data production.
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Sakhalin I 3D Seismic Interpretation Leads to Discovery of Significant Oil Leg at Chayvo Field
Authors J.M. Lohmar, R.J. Powell, D.H. Freeman, E.M. Johnstone and D.C. KasperA 3D seismic survey acquired over Chayvo Field, offshore Sakhalin Island, in 1997 identified the likely
presence of large oil rims in reservoirs which had tested mostly gas in crestal wells. The rims were identified
from pairs of amplitude anomalies that conformed to structural contours and were interpreted as gas-oil and
oil-water contacts. Several interpretation techniques were used to increase confidence in the postulated
contacts and predict contact depths. The oil rims and contact depths were tested and confirmed with an
appraisal well drilled in 2000, resulting in a significant oil project in a field thought to contain mostly gas.
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Direct seismic detection of fluids and reservoirs: technology trends and lessons learned
Authors D. Johnston, K. Rudolph, B. Fahmy and J. ReillyThe oil industry is increasingly reliant on the analysis of seismic data for the quantitative prediction of fluids
and reservoirs. This includes technologies such as DHIs (direct hydrocarbon indicators), AVA (amplitude
vs. angle), quantitative attribute analysis, and visualization. Such techniques are critical to identify and
characterize new wildcat opportunities, optimize developments, and exploit remaining reserves in mature
fields.
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Quantifying 3D Acquisition Adequacy for Azimuthal AVO Analysis
Authors W. Dong and M.E. DavidsonAzimuthal AVO (AZAVO) refers to the directional
variation of P-wave reflection amplitude at a fixed offset.
There are several possible causes for this azimuthal
amplitude variation: reservoir property, structural change of
the reflector, near surface effects, overburden property
variation, acquisition footprint, processing artifacts,
source/receiver radiation/reception patterns, etc. While
paying close attention to all these causes is necessary for
meaningful azimuthal AVO analysis, geophysicists are
most interested in the azimuthal amplitude variation caused
by a particular reservoir property: fracturing of the
reservoir. Through a decade of theoretical study and some
well-documented case histories it’s now generally accepted
that aligned open fractures will introduce azimuthal
anisotropy to the host rock and can therefore be detected
from analyzing P-wave reflection amplitude variation as a
function of azimuth.
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Interpretation and Visualization of drilling hazards in the South Caspian Basin: Zafar Mashal Prospect
Authors J.K. Mikkelsen and K. FowlerThe large offshore structures in the Azerbaijan sector of the South Caspian Basin are associated with
difficult drilling conditions due to a number of factors. 3D visualization and interpretation tools have been applied
to mitigate the numerous drilling hazards such as over pressured channels, shallow faults, shallow gas and mud
volcanoes. The same tools have been used to integrate interpretation results into the well plan and visualize the
associated drilling uncertainties.
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Performance of gravimagnetic anomaly algorithms for uniform polyhedra
Authors H. Holstein and E.M. SherrattFormulas for the gravity potential, eld, eld-gradient,
magnetic potential and eld of a polyhedral target
of spatially uniform density or magnetization su er
asymptotic rounding error that grows proportionally to a
power of the dimensionless target distance. The form of
the error growth can be speci ed by universal templates
that are applicable to a very wide class of targets and
arbitrary floating point precision, and hold for all the
standard gravimetric anomaly calculations.
A compact form of the anomaly formulas allows the theoretical
a priori templates to be be derived, depending
only on the presence or absence of foreshortening in the
observed anomaly, and class of anomaly formula used,
of which three kinds are found in the literature. Computational
results, con rming this claim, demonstrate
automatic method selection to accomplish maintenance
of rounding error to a speci ed level in magnetic eld
computations.
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Assessment of the subsidence and turfs in the internal Maliqi depression using geophysical methods
More LessAn area of about 120 km2 (from the Zvirina-Podgorie Line in North close to the Vashtemi-Shamolli
Line, which is the area of the former Maliqi Swamp) was covered by the geophysical methods. Geologically
this area consists of the Quaternary overburden formations (Q1-4) and the Upper Neogene, concretely not
differentiated Pliocene and Pliocene-Quaternary (N2-Q1) formations.
The main objectives of this study have been:
1. Investigation of the subsidence phenomenon, which may lead to the gradual formation of the Maliqi
Swamp.
2. Development of the monitoring network to observe the subsidence phenomenon.
3. Locating an eventual second turf layer under the known one and its control with integrated methods.
To achieve geological-geophysical (electrical) resulsts for the two first objectives there have been mostly
used geodesical methods.
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Investigation of ground water of karst origin using geophysical methods, Kastrat area, Albania
More LessGeophysical methods, especially electrical ones, are widely applied in solving urban problems and
ground water prospecting as well. Intensive works of ground water prospecting are closely related to the
emergent needs of the Albanian society as result of the rapid demographic changes because of population
migration during the transition period. This abstract provides the results of application of geophysical
methods in ground water prospecting and investigating of water-bearing potential of carstified limestones in
the Komuna Kastrat area, northwest Albania. These works are carried out within the framework of a project
for natural resources of northern Albania Prefectures.
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Examples of use of electric sounding and SP for finding and estimating the aquifers, Lezhe-Shkoder region, Albania.
More LessThe Lezhe-Shkoder-Hani Hotit region takes part in the governmental perspective plans for
developing the tourism and it is also one of main priorities for developing the agriculture. Therefore the
exploration and discovering the aquiferous basins and estimating their potential especially for potable water
is an immediate geologic task.
The aquifer exploration in this regionis related with alluvial deposits of Quaternary and with carstic zones of
carbonates.
The Quaternary formations are represented by deluvialand aluvial deposits composed of argillaceous
gravelsand partly by limestone and dolomite blocks. The thickness of this formations is up to 100-120m
The geophysical surveys carried out with electrical soundings have provided considerable information on
lithology of the formations in the area and water-bearing potential as well.
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Effective anisotropy due to thin VTI layers
By A. BakulinSeismic anisotropy observed in the field is a cumulative result of various mechanisms. Subsurface rocks often
possess intrinsic anisotropy approximated by a transversely isotropic solid with a vertical symmetry axis (VTI).
Alternatively, in the long-wavelength limit, ”layer-induced” VTI anisotropy may arise even in a stack of thin isotropic
constituent layers. In most practical cases these two effects occur simultaneously. We develop weak anisotropy and
weak contrast approximations to understand the contributions of intrinsic and layer-induced anisotropy. When the
contrast in elastic parameters between the constituents is small and their anisotropy is weak, then (to the first order)
layering-induced anisotropy is insignificant whereas intrinsic anisotropy produces effective Thomsen parameters equal
to the thickness-weighted average of the interval anisotropy parameters. This conclusion considerably simplifies
upscaling of finely-layered VTI media because to find the effective Thomsen parameter ² (or ± or °) one needs to
know only constituents ²’s (or ±’s or °’s correspondingly).
For larger variation in the elastic properties, each anisotropic parameter may be approximated as the sum of two
terms: one is the averaged intrinsic anisotropy and the other is a purely isotropic term related to fluctuations in
the vertical interval velocities. The isotropic term has been extensively investigated in literature, and all previous
conclusions may be directly applied to the more realistic VTI case considered in this study.
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Rock Property Determination Using Digital Rock Physics
Authors J. Dvorkin, A. Tutuncu, M. Tutuncu, A. Nur and A. MeseThe Digital Rock Physics (DRP) technology is based on a rigorous numerical simulation of physical experiments
in a realistic pore space, at the pore-scale level. The output is usually a macroscopic property conventionally
measured in the lab. For example, a single-phase viscous fluid flow simulation through a digitized pore space
provides absolute permeability. A simulation of electrical current provides conductivity, and a simulation of the
stress field provides the elastic moduli and strength. DRP complements lab measurements and, at the same time,
enormously enhances the geoscientist’s capabilities because digital experiments can be conducted in real time
and on small fragments of rock, such as drill cuttings. We report a feasibility study on DRP technology applied
to drill cutting samples to obtain porosity, permeability, and the P- and S-wave velocity.
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Enhanced signal-to-noise ratio and bandwidth through explosives design
Authors D. Bremner, G.A. Tite, P. Thompson and J. BrooksThe signal-to-noise ratio and bandwidth of explosive-sourced seismic data are the direct result of the
properties of the explosives used and the near-surface conditions. Conventional wisdom has dictated
that certain properties are desirable in seismic explosives. A series of experiments have shown that
some of these assumptions should be revisited.
Multivarient testing has confirmed that the efficacy of seismic explosives can be improved in many
environments. This reinforces the contention that the design of the explosive utilized is critical to the
ultimate quality of seismic data. These results suggest that a method of testing and customizing
explosives to take advantage of these variations can be established.
Current data suggest that 3 to 6 dB of signal enhancement may be achieved in the seismic bandwidth
through the use of metalized explosives. Examples of these improvements will be presented in the
paper. Based on these improvements, it should be possible to achieve better signal-to-noise ratio and
bandwidth.
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Borehole Integration Technologies for Seismic Reservoir Characterization: Application to Hassi Messaoud Field.
Authors S. Morice, M. Robinson, R. Lounis, S. Leaney, S. Tcherkashnev and M. WheelerNew technologies for integrating borehole information throughout the surface-seismic workflow have demonstrated superior seismic imaging and reservoir characterization, and reductions in project turn-around time. These technologies, and results from their application in Hassi Messaoud Field, Algeria are presented.
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Interval density mapping for thick layers
Authors I. Vasiljevic and J. MilovacA simple method for interval density determination in thick layers by joint analysis of surface and
subsurface gravity maps is presented in this paper. Method is designed for solving interval density
distribution problem in cases of significant lateral density variations above deep mines, where there is no
possibility to conduct gravity measurements along vertical shafts. Application of this method doesn't require
precise position and characteristics of anomalous masses. All that is necessary is a general idea of anomalous
zones distribution.
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