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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
21 - 40 of 322 results
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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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