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53rd EAEG Meeting
- Conference date: 26 May 1991 - 30 May 1991
- Location: Florence, Italy
- ISBN: 978-90-73781-03-0
- Published: 28 May 1991
141 - 160 of 315 results
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2D and 3D seismic modelling of crustal structural heterogeneities
Authors S. Hestholm, B. O. Rosland, E. S. Husebye and B. O. RuudSeismic surveys are based on analysis of complex short wavelength signaIs, while the resolved model elements are often simple and of much longer wavelength. Furthermore, attribute analysis of three component seismic records testifies towarels medium complexities not commonly incorporated in the structural modeIs. To provide better understanding of high frequency wave propagation within the heterogeneous crust, we use finite difference (FD) modeling in 2D and 3D in combination with more conventional analysis of seismological data.
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Shear-waves from 3-C ocean bottom seismographs indicative of anisotropy in the lower crust
Authors R. Mjelde, M. A. Sellevoll and E. W. BergThis refraction study was performed in August 1988 by the Institute of Solid Earth Physics, University of Bergen, Norway in cooperation with the Hokkaido and Tokyo Universities, Japan. The purpose of the experiment was to map the crustal structure off Lofoten, northern Norway, from the outer part of the continental shelf to the oceanic crust, and to make use of all three components of the Ocean Bottom Seismographs (OBS) in a detailed shear-wave study. Twenty one 3-C OBSs were used along 8 profiles in a 3D grid.
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Amplitude and time-frequency analysis of ecors deep reflection seismic data
Authors D. Rappin, J. M. Marthelot and E. de BazelaireThe discontinuous aspect of deep crustal reflections on stacked seismic sections has led us to a study of the original records, the true amplitude shot gathers. We look at the amplitudes, the lateral continuity of reflections and the frequency content of the signal in order to obtain more precise informations about the physical properties and the geometrical structures in the crust. These studies are done on ECORS deep reflection seismic profiles and can also be done on seismic exploration data.
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Geophysical study of the Ross Sea (Antarctica)
Authors M. Pipan, J. Finetti, A. D. Ben and R. GelettiThe interpretation of a large amount of multichannel seismic reflection sections recorded during the first Italian geophysical cruises to Antarctica (1978-88, 1988-89), performed by OGS-Trieste, has revealed new and interesting elements about the structure, the stratigraphy and the evolution of the Pacific sector of the Antarctic Platform.
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Statistical investigations of the density-velocity relation using the database DABACOS
More LessEmpirical correlations between seismic velocities and bulk densities of rocks are of particularly interest for practical purposes like combining results of seismic and gravity measurements. Relations like the Nafe-Drake-curve or the Gardner-formula are used to get a priori data for the estimation of a density model by seismic data. Beyond that, they are frequently employed for theoretical penetration studies of seismic waves and for the calculation of synthetical seismograms. Combined with deep drilling programs relations for crystalline rocks become even more important in the near future.
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Application of fuzzy pattern recognition to seismic stratigraphy
Authors B. Lashgari and R. E. EstillA new method for seismic stratigraphic analysis is proposed and its effectiveness on seismic data is discussed. The method utilizes seismic attributes and the concept of fuzzy pattern recognition to automatically track horizons and identify termination points. In sequence stratigraphy this is an effective approach in providing valuable information to interpreters in relation to sequence boundaries, seismic facies, and horizon mapping.
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Logical object model and derived exchange format for 3D subsurface model data
Authors I. L. Ritsema, S. Pen and Th. KemmeIn the Oil and Gas Exploration and Production Industry many data are being exchanged or traded. For many object classes commonly agreed data exchange formats exist (e.g. SEGY. LIS. UKOOA. OLG. etc.). An important object class without any standard exchange format is the class of 3D geological or geophysical data. In the Geoscience Research Programme funded in part by the EC (OG XII) a logical model has been developed for objects describing 3D subsurface modeis. From the logical object model three types of implementations and a exchange format can be derived.
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Interpretation and geomodelling of diapiric structures using the SlIS workstation
Authors D. Jackson, A. Carter and J. FarnsworthThe value of workstations for exploration and development has long been appreciated, but recently in addition to the interpretation and general mapping capabilities, interactive geomodelling techniques carried out wholly within the workstation environment are becoming available. using examples from recently drilled diapiric plays in the Central North Sea, we illustrate how interactive interpretation and geomodelling have been applied during a series of pre-drill/ post-drill phases.
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Practical use of advance software in an interactive stratigraphic and structural analysis of roar field: A case history
Authors I. Abatzis and J. D. KerrThe Roar structure is situated in the Danish Central Graben and is surrounded by the Bo, Boje, Adda, Tyra and Jens structures. It is a low relief porous chalk closure generated by structural inversion during the Late Cretaceous and Tertiary periods. In addition, the general increase in subsidense toward the center of the Central Graben in Tertiary times has also influenced the structural evolution.
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Visualization of map and seismic attributes
Authors H. R. Nelson Jr., S. Mastoris and C. HuxohlNew map and seismic attributes have been developed for use on interactive seismic workstations. These techniques were applied to the interpretation of both geologic structure and stratigraphy from 3d seismic surveys from Canada and the Gulf of Mexico. In both of these geological domains the new attributes provided new infonnation leading to a more complete and accurate interpretation. We will first describe the seismic attributes used to assist identifieation of reservoir reflectors, and then describe the map attributes and how they aided the interpretation. Specifically, we show how these map and seismic attributes explained why wells in one part of a project area were more productive than those in other places in the project, and how this interpretation fonnulated new leads for additional well locations.
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Interactive volume modelling
Authors P. A. Irwin and A. ParadisDynamic Graphics, Inc. has developed a tool that enables the display and analysis of three-dimensional data. Users are able to rapidly gain a much clearer understanding of internal geometric and property relationships within three-dimensional singel of multiple layer frameworks.
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Seismic attributes in borehole full waveform sonic logging
By S. KnizeApplication of surface seismic data processing and display techniques to borehole sonic data provides a means for formation description near the borehole, as well as for the integration of sonic information with surface seismic and cross-borehole tomography sections. The seismic trace attributes analysis and the colorcoded displays which are adapted for Investigation of full waveform sonic (FWS) data reveal additional FWS characteristics helpful in describing rock properties such as dipping boundaries, fractures, and permeability. In this appllcatlon the seismic attributes have distinct geophysical meaning which are specifically pertinent to FWS logging and are called Instantaneous Waveform Characteristics (IWC). The color-coded displays are called colorgrams. The IWC displayed in the colorgrams are also quantified, plotted as log curves, and interrelated to give geophysical parameters such as the quality factor (a) of the formation.
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Cross-well continuity logging using stoneley waves at the Whitchester borehole test site
More LessThe Imperial College borehole test site is situated in the the county of Northumberland, England. It consists of four vertical 250 metre boreholes positioned as in figure 1. The holes intersect an Upper Carboniferous cyclical sequence of sandstones, shales and limestones. (see Figure 2a) Holes 1 and 2 have been fully cored and all holes have been extensively logged. Although the bedding is approximately horizont al over the area of the site, minor faulting has been identified. This is very clearly indicated in the FMS data which has been acquired in all four holes.
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Fracture detection using reverse vertical seismic profiles and cross-hole surveys
Authors E. Liu, S. Crampin and J. H. QueenPrevious observations have suggested that the effects of fractured-related seismic anisotropy is observabIe, particularly in vertical seismic profiles (VSPs) (Crampin et al. 1986; Johnston 1986, and among many others). Fractures can be a significant feature of hydrocarbon reserviors where their presence (either natural or .induced) may increase the productive capacity. Many reserviors with a low matrix permeability would not be commercially attractive without a natural or induced fracture system. Fractures at the shallow depths are also important for the fluid flow in engineering and hydrological applications.
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Seismic imaging at the Whitchester test site using cross-hole data
Authors Q. Li and P. R. WilliamsonThe Imperial College test site at Whitchester consists of a group of four near-vertical boreholes of approximately 250 metres depth. These have been extensively logged and are now cased. A crosshole seismic dataset has be collected between boreholes 1 and 2 over a depth range of 50 to 120 metres. The holes are 25 metres apart. The sources were detonator caps fired at 2 metre intervals, and the signals were recorded with a twelve-component hydrophone streamer. The data contain frequencies in excess of 1.5kHz, with peak energy around 800Hz in the early arrivals. Despite severe contamination by tube waves the data are suitable for use in a variety of imaging algorithms.
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Tube-wave-VSP in cracked crystalline rocks: some new aspects
More LessIn vertical seismic profiling tube waves are generalty classified as noise, They have, however, one useful application: Tube waves can be generated by compressional waves at fluid filted cracks crossing the walt of the borehole. In this case the permeability of the crack can be estimated from the amplitude ratio of the incident p - wave and the generated tube wave.
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Borehole stoneley wave propagatoin across heterogeneous and permeable structures
Authors X. M. Tang and C. H. ChengFractures or permeable structures in reservoirs are of great importance in the exploration and production of hydrocarbons. Heterogeneous layers in the formation are also of major significance. A very good example of such heterogeneous and permeable structures are the sand-shale sequence found in sedimentary fonnations. Full wavefone acoustic logging offers an effective tooI for characterizing these structures.
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Fault mapping using scattered, guided arrivals on a single-level walkaway seismic profile
Authors G. M. Jackson, I. M. Mason and D. LeeField recordings of a 2-D grid of surface shotlines by a single triaxial down hole geophone (single-level Walkaway Seismic Profile) showed guided arrivals scattered from faults. Downgoing P-wave energy scattered from breaks in a strong reflector became trapped in a low velocity layer immediately beneath the reflector.
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Reservoir sonics: A north sea case study
Authors B. E. Hornby, W. F. Murphy III, H. -L. Liu and K. HsuFull waveform sonic data, acquired with a research sonic tooI in a borehole penetrating a North Sea reservoir, were used to explore potentially new applications for analysis and interpretation of full-waveform sonic data. The reservoir is a high porosity, unconsolidated sandstone with Darcy permeability and is inter-bedded with calcite and coal stringers. The wellbore is deviated approximatly 50 degress through low-angle bedding and intersects a region of strong normal faulting.
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Field studies of the anisotropic properties of sedimentary rocks
Authors C. K. Jituboh, M. S. Sams, M. S. King and M. H. WorthingtonExperiments have been perforrned at the Imperial College test site, Whitchester, Northumberland (Worthington, 1991) to determine the anisotropic properties of a variety of sedimentary rock types over a wide range of frequencies. The four boreholes at the site have been extensively logged and cored, so that detailed information is available on many properties of the rocks under investigation.
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