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65th EAGE Conference & Exhibition
- Conference date: 02 Jun 2003 - 05 Jun 2003
- Location: Stavanger, Norway
- Published: 02 June 2003
81 - 100 of 487 results
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Azimuth Preservation in Marine 4D Acquisition
Authors M. Widmaier, S. Hegna, F. Smit and E. TijdensC-04 Azimuth Preservation in Marine 4D Acquisition Summary - An Acquisition Strategy for Marine 4D Repeating source-receiver azimuths can be an important aspect of 4D acquisition. Seismic repeatability will decrease with an increase of source-receiver azimuth differences between base and monitor surveys. This paper discusses a marine acquisition strategy with respect to the optimal preservation of source-receiver azimuths in the presence of feathering. We show that repeating shot positions is favourable for azimuth preservation in 4D acquisition in combination with overlap configurations (additional outer streamers). With a dense streamer separation source-receiver azimuths can be repeated very accurately by using this
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Positioning Accuracy and 4D Seismic Sensitivity in Land Acquisition
Authors S. Herculin and J. MeunierC-05 POSITIONING ACCURACY AND 4D SEISMIC SENSITIVITY IN LAND ACQUISITION 1 Abstract The most challenging difficulty of marine 4D seismic technology is repeating a given acquisition geometry with high precision. This challenge does not exist onshore. It is therefore possible to aim for the higher 4D sensitivity needed to observe changes in carbonated reservoirs. The required precision of source and receiver deployment is first evaluated on synthetic data. A field experiment is conducted its results are analyzed and as a conclusion recommendations are made to achieve higher 4D sensitivity. Introduction The slower development of 4D seismic technology onshore than offshore
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Simultaneous Coded Vibroseismics
By M. BecqueyC-06 SIMULTANEOUS CODED VIBROSEISMICS Abstract Vibrations from two vibrators emitting simultaneously with shifted coded signals were recorded and separated. Processing and stacked sections are similar to the results obtained with a classical sweep acquisition. The possibilities of separation of simultaneous records offered by the experimented codes may lead to an increase in productivity. They may also lead to an increase in resolution by allowing to dissociate and reconstruct the shot arrays. Introduction Methods for separating overlapping sweeps have been developed for productivity purposes (Rozemond 1996). These methods encounter some problems with the presence of harmonic noise (Meunier et al. 2001).
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One Step Better than Static Corrections – The Topographic Datuming Operator
Authors C. Bagaini and T. AlkhalifahC-07 ONE STEP BETTER THEN STATIC CORRECTIONS - THE TOPOGRAPHIC DATUMING OPERATOR Abstract 1 We formulate an analytical expression of a new prestack operator the Topographic Datuming Operator (TDO). This datuming operator generalizes the operation of static corrections which is very well known in the seismic exploration community and widely used in land seismic data processing. TDO eliminates the essential assumption of vertical incidence to the Earth’s surface of the downward- and upward-propagating reflected wavefield which is not valid in the presence of high-velocity shallow layers and/or large offset-to-reflector depth ratios. The assumptions of equivalent constant velocities for the overburden
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Influence of Acquisition-Related Amplitude Variations on Imaged-Reflector Amplitude Accuracy
Authors M.B. Koch, G.G. Drijkoningen, A.W.F. Volker and N. FilippidouC-08 INFLUENCE OF ACQUISITION-RELATED AMPLITUDE VARIATIONS ON IMAGED- REFLECTOR AMPLITUDE ACCURACY Summary 1 MENNO KOCH 1 GUY DRIJKONINGEN 1 ARNO VOLKER 2 and NIKOLETTA FILIPPIDOU 1 1 Delft University of Technology Department of Applied Earth Sciences EAGE 65th Conference & Exhibition — Stavanger Norway 2 - 5 June 2003 2 TNO TPD Delft Many factors in aseismic acquisition and processing sequence affect the reliability of the amplitudes in a seismic image. On land data the acquisition footprint is usually not observed due to other amplitude errors like source- and geophone-to-ground interaction effects. The CFP method enables the assessments of the
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Rock Physics around the World – Local Differences and Global Similarities
Authors P. Avseth, R. Ona, S.L. Jensen and A-J. van WijngaardenC-09 ROCK PHYSICS AROUND THE WORLD – LOCAL DIFFERENCES AND GLOBAL SIMILARITIES Abstract 1 Rock physics and seismic properties of rocks are highly controlled by local geologic factors. Thus rock physics properties can change dramatically within a given sedimentary basin. For the same reason rocks in different areas of the world may have very different seismic properties even if the burial depth is the same. Critical geologic factors that control seismic properties are either related to mineralogy depositional environment or burial history. In this paper we demonstrate that local geology is important when analyzing rock physics and seismic properties in
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Views of Rock Physics in a Ternary Space
Authors W.D. Pennington and D. ForelC-10 VIEWS OF ROCK PHYSICS IN A TERNARY SPACE Summary 1 Elastic properties of rocks can be made easier to understand and to compare among models when viewed in a three-dimensional “ternary space” with parameters plotted above a ternary diagram that represents the composition of a rock. Vagaries of certain models and differences or similarities among models that are difficult to explain when viewed in the conventional two-dimensional framework suddenly appear intuitive and straightforward. The ternary space model can be extended to additional dimensions although then it is difficult to visualize. In any number of dimensions the model can be
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Elastic Behaviour of North Sea Chalk
Authors L. Gommesen, I.L. Fabricius and J.M. PedersenC-11 ELASTIC BEHAVIOUR OF NORTH SEA CHALK 1 L. GOMMESEN 1 I. L. FABRICIUS 2 and J. M. PEDERSEN 3 . 1 Ødegaard A/S Titangade 15 DK-2200 Copenhagen Denmark formerly E&R Technical University of Denmark. 2 E&R Technical University of Denmark. Summary This work describes the elastic behaviour of chalk from the Ekofisk Tor and Hod formations from the Danish sector of the North Sea from a study of log data from four wells. We discuss the detection of cementation and how it affects the elastic behaviour of the chalk. By applying a suitable fluid substitution model to an established
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Velocity, Saturation and Fluid Distribution Measured by a 4D-CT Laboratory Method
Authors S.E. Johnstad and K. MonsenC-12 VELOCITY SATURATION AND FLUID DISTRIBUTION MEASURED BY A 4D-CT LABORATORY METHOD Summary 1 A recently developed laboratory method allows for simultaneous imaging of fluid distribution and measurement of acoustic wave velocities during flooding experiments. Using a specially designed acoustic sample holder that combines high pressure capacity with good transparency for X-rays it is possible to investigate velocity-fluid saturation relations at reservoir stress levels. High-resolution 3-D images are constructed from thin slices of cross-sectional CT-scans covering the entire rock core volume showing the distribution of fluid at different saturation levels. The system is briefly described and examples are presented from
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Wave Velocities in Shales – A Rock Physics Model
More LessC-13 WAVE VELOCITIES IN SHALES – A ROCK PHYSICS MODEL Abstract 1 A rock physics model for predicting wave velocities in shale has been established based on the Hashin-Shtrikman (1963) theory for elastic properties of composite media. The model has been used to analyse P-wave velocity measurements on 20 different shale cores with porosities ranging from 3 to 70 %. At present it seems to capture the porosity dependence as well as the stress sensitivity of the P-wave velocity. Introduction Elastic wave propagation in shale is of interest to the petroleum industry for several reasons. All seismic investigations of reservoirs
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Rock Physics of Gas Hydrate Reservoir
Authors J. Dvorkin and A. NurC-14 ROCK PHYSICS OF GAS HYDRATE RESERVOIR 1 Summary. Enormous amounts of methane gas hydrate are present in sediments under the world's oceans as well as in on-shore sediments in the Arctic. These hydrates are a potential future energy resource. The most well-developed geophysical tool for exploring large volumes of the subsurface where gas hydrate is found is seismic reflection profiling. To characterize a natural gas hydrate reservoir with seismic data we must be able to relate the elastic properties of the sediment to the volume of gas hydrate present. One way of achieving this goal is through rock physics
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Experimental Study of Wettability and Seismic Velocity in Sandstones
Authors J. Sothcott, C McCann, S. Assefa, P.R. Domnesteanu and T.R. AstinC-15 EXPERIMENTAL STUDY OF WETTABILITY AND SEISMIC VELOCITY IN SANDSTONES Summary 1 This abstract presents the results of a laboratory investigation into the effect of changed wettability and of pore fluid type on the acoustic properties of two sandstones. The compressional wave velocity and the shear wave velocity were measured for the core plugs saturated with brine with a mixed phase of crude oil/brine and with crude oil at effective pressures up to 60 MPa. The wettability of the core was changed by ageing wettability state being determined by environmental scanning electron microscope observations. Introduction Oil fields exhibit a wide
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Ranking Geological Drives for Mapping Fracture Intensity at the Pinedale Anticline
Authors P.M. Wong and S. BoernerC-17 RANKING GEOLOGICAL DRIVES FOR MAPPING FRACTURE INTENSITY AT THE PINEDALE ANTICLINE Abstract 1 Fractured reservoir characterization requires a good understanding of the spatial distribution of fracture intensity. In practice the relationships between various geological drivers and fracture indicator are complex and highly nonlinear. The problem is worse when there are many drivers but the number of sample locations is small. This paper compares the use of two ranking algorithms namely “fuzzy ranking” and “optimized piecewise rank correlation” or OPRAC for selecting relevant drivers for building regression models. The study uses a set of seismic and gas production data at
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Fracture Mapping Using Azimuthal Velocity/AVOA Seismic Data in Saudi Arabia
Authors F.A. Neves, A. Al-Marzoug, J.J. Kim and E. NebrijaC-18 FRACTURE MAPPING USING AZIMUTHAL VELOCITY/AVOA SEISMIC DATA IN SAUDI ARABIA Abstract 1 A wide-azimuth full-offset 3D P-wave seismic survey has been acquired over a sandstone gas reservoir in Saudi Arabia. The seismic data have been processed to preserve and extract anisotropic effects. Velocity and amplitude ellipticities were computed from pre-stack seismic data using a software developed in house by Saudi Aramco. Our results showed a slight azimuthal variation in P-wave velocity and significant variation in Amplitude-Variation-with- Offset-and-Azimuth (AVOA) at the reservoir level which were interpreted as being generated by either aligned vertical fractures or induced by the predominant tectonic
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Fracture Anisotropy Signatures in the Wudayhi Field Using Azimuthal Seismic Data
Authors K.A. Al-Hawas, M.S. Ameen, M. Wahab, E. Nebrija and C. MacBethC-19 FRACTURE ANISOTROPY SIGNATURES IN THE WUDAYHI FIELD USING AZIMUTHAL SEISMIC DATA 1 KHALID AL-HAWAS 1 MOHAMMED AMEEN 1 MOHAMMAD WAHAB 1 ED NEBRIJA 1 Summary The Wudyhi Field was discovered in Saudi Arabia in 1998. Well testing of the first few wells indicates that fractures are essential part of the reservoir. This makes it of paramount importance to detect and characterize the fracture distribution in the reservoir to optimize field development. Seismic data from a recently acquired wide-azimuth full-offset 3D survey shot over the Wudayhi are processed and interpreted to detect the azimuthal signature of aligned vertical fractures and
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Seismic Fracture Analysis on the Pinedale Anticline – Implications for Improving Drilling Success
Authors F.D. Gray, D. Todorovic-Marinic and M. LahrC-20 SEISMIC FRACTURE ANALYSIS ON THE PINEDALE ANTICLINE – IMPLICATIONS FOR IMPROVING DRILLING SUCCESS Summary 1 The Pinedale Anticline in Wyoming USA has become an area of significant interest since the recent success of several wells that have produced significant volumes of gas from its tight sandstone reservoirs. Production from these reservoirs is now possible using new stimulation techniques that were developed in neighboring Jonah Field. The best production rates appear to come from reservoirs that have had their permeability enhanced by natural fractures. Therefore the ability to detect the presence of natural fractures in the reservoir could have a
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Robust P-Wave Fracture Characterization from Wide-Azimuth Seismic Data
Authors E. Angerer, D. Lecerf and P. LanfranchiC-21 ROBUST P-WAVE FRACTURE CHARACTERIZATION FROM WIDE-AZIMUTH SEISMIC DATA Abstract 1 Reliable sub-seismic scale fracture characterization requires an integrated approach of wideazimuth wide-offset data acquisition data processing robust attribute generation and subsequent inversion of fracture-related azimuthal anisotropic effects. This workflow is illustrated on a real data example. A recently developed approach of geostatistical decomposition makes it possible to separate azimuthal seismic attributes into (1) a “geological” common part (2) the azimuth-dependent fracture information and (3) random and organized noise. A linear least-squares inversion leads to fracture density and orientation maps. Introduction Fractures cause second-order variations of both P- and S-wave
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PS-Wave Azimuthal Anisotropy – Seismic Properties for Fractured-Reservoir Management
Authors J.E. Gaiser and R.R. Van DokC-22 PS-WAVE AZIMUTHAL ANISOTROPY – SEISMIC PROPERTIES FOR FRACTURED- RESERVOIR MANAGEMENT Abstract 1 Fractures can significantly influence the behavior of reservoir porosity and permeability resulting in numerous dry wells and higher production costs. In some cases fractures can dominate storage and flow mechanisms within the reservoir and in other cases they can create barriers. 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 are also sensitive to fracture dip because of their asymmetry. These large-scale
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Azimuthal Anisotropy Analyses Using Multicomponent Seismic Data
Authors T. Probert, B. Olofsson, J. Gaiser, D. Underwood and P. KristiansenC-23 AZIMUTHAL ANISOTROPY ANALYSES USING MULTICOMPONENT SEISMIC DATA Abstract 1 There are numerous published case studies showing that 3D converted-wave processing can be successfully used to help solve a number of different geophysical problems. For instance imaging a low P-impedance contrast improved sub-gas imaging and characterizing reservoir fractures. However there is rarely a standard survey design and the processing is often dependent on the survey design and the geophysical objectives. One aspect that has become more important for all 3D converted-wave processing is the effect of S-wave splitting. This may be exploited to characterize reservoir fractures or it may be
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The Potential of Estimating Fracture Sizes from the Frequency Dependence of Anisotropy
Authors S. Maultzsch, M. Chapman and E. LiuC-24 THE POTENTIAL OF ESTIMATING FRACTURE SIZES FROM THE FREQUENCY DEPENDENCE OF ANISOTROPY Summary 1 Frequency-dependent anisotropy has been observed in seismic data and it can be explained by fluid flow in fractured porous rock. In this study we use a new equivalent medium theory that considers fluid movement due to a squirt-flow mechanism at two scales: the grain scale where the pore space consists of micro-cracks and equant matrix porosity and formation-scale fractures. The theory models velocity dispersion and frequency dependence of anisotropy with the fracture length being one of the key parameters. The model is first tested and
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