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54th EAEG Meeting
- Conference date: 01 Jun 1992 - 05 Jun 1992
- Location: Paris, France
- ISBN: 978-90-73781-04-7
- Published: 01 June 1992
41 - 60 of 405 results
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Use of GPR to obtain layers thickness variation in a test track
Authors E. Lorenzo, I. Fernandez and V. CuellarA test track built by the official research center of the Spanish Ministry of Public Works (CEDER) came into operation in January 1988 . The track constituted by two 75 m long straight sections connected by two curves has an oval shape and a total length of 304 m . It stands on a concrete box 8 wide and 2 .60 m deep .
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Ground penetrating radar for roads and bridges: strengths and limitations
Authors N. S. Parry, J. les Davis and J. R. RossiterGround Penetrating Radar (GPR) has been used increasingly on roads and bridges over the last five years. GPR offers non-destructive evaluation of the subsurface along continuous profiles, providing unique information on the structural layers and material properties of roadways . Given that roads have a relatively simple geometry and are usually composed of homogeneous, engineered materials, this application would appear ideally suited to SPR . However, there are several pitfalls associated with this application . Some of these pitfalls are generated by equipment limitations, such as pulse length, sampling rates and fitter . Others are introduced when standard assumptions, commonly applied to GPR data from geotechnical environments, are used . In addition, the particular Weeds of the end client must be considered .
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Ground penetrating radar applications for nondestructive inspection of construction work
Authors M. Bashforth and S. KoppenjanThe nondestructive inspection of construction work has gained significant interest in the United States in the 1940's. The decire to verify building standards and codes has become an increasing problem. In many cases there - is no existing nondestructive method to accomplish this. Knowledge of the location and depth of building support mate rials is greatly needed .
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Groundradar applications for road constructions
Authors V. Hopman, A. J. M. Peters and J. W. de FeijterIn the Netherlands a large amount of infrastructural elements are concentrated on a relative small area . Highways, railways, waterways and all kinds of roads intersect each other at many locations . High investments are necessary to maintain these infrastuctures. Also cables, pipes and many cycle-paths cross main infrastructuren.
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Save Venice. A multidisciplinary investigation in the Rio Nuovo collapsing embankments
Authors M. Picollo, A. Fio, G. Niccolini and G. SpangheroBecause of erosion problems in the foundation wall of Rio Nuovo, probably caused by the ferry boat traffic, some collapse phenomena were observed on the surface of the embankment . A diagonal fracture in the asphalt surface interested a corner of the ferry boat station showing a collapse of about 15 cm. The interest was to understand the geometry of the collapsing structure, the depth limit of the event, the possible relationships with the morphology of the channel bottom and the identification of other hazard areas in west and east embankments .
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Radar techniques for the evaluation of masonry structures
More LessCivil engineers have a need to evaluate the condition of masonry structures such as bridges and tunnels in order to classify the condition of the structure . Impulse radar techniques have been used in the past, but interpretation of the data has been difficult as the radar data does not necessarily correspond with the geometrical structure . British Rail Research commissioned ERA Technology, over several years, to carry out a detailed investigation of the correlation between the radar image and the physical structure, in order to improve the clarity of the radar image .
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Subsurface imaging with EMAP - an aid to seismic processing and interpretation
By R. K. WarrenThe EMAP (Electromagnetic Array Profiling) exploration method has been combined with a direct inversion process for conversion to depth to produce a subsurface resistivity cross-section. This cross-section is interpreted in parallel with a seismic cross-section to enhance the prediction of rock type and structure. In complex thrust environments, areas of shallow volcanics and/or carbonates the EMAP method is used to provide additional data to either help the seismic processing and/or aid the seismic interpretation . In particular, the EM data are used to build an independent seismic velocity file for depth migration .
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Electromagnetic mapping of electrical conductivity beneath the Columbia basalt
Authors Y. Shoham, F. Morrison and C. Torres-VerdinThe Colombia basalts cover a petroliferous sedimentary section and they present a representative example of the challenging problems of trying to determine sedimentary thickness and structure in situations where seismic methods do not provide adequate depth of exploration . Between 1979 and 1986 Shell conducted a series of controlled source (CSEM) and natural field (MT) surveys at several sites in the Columbia basalts and the results for a profile near Boylston are described in this study .
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Advances in the integrated interpretation of seismics with magnetotellurics (illustrated by practical examples from the Pannonian basin in Hungary)
By Z. NagyIntegrated interpretation of seismic reflection and magnetotelluric (MT) surveys is a new approach to improve the results in prospecting for hydrocarbons. Recent, successful applications of MT method to the hydrocarbon exploration are discuseed by Christopherson (1991). However, there are few published case histories on the integration of seismic and MT data. The main purpose of this paper is to demonstrate that the interpretation of seismic sections can be improved by incorporating results from magnetotelluric surveys . In Hungary, the Hungarian Oil and Gas Co. is prospecting for hydrocarbons . Most of the work is in several subbasins of the Pannonian basin (Silverman and Barton, 1991) . Although the seismic reflection method is the primary tool employed, non-seismic methods are also applied, including magnetotelluric techniques (Ádám, Nagy and Varga, 1989) and other controlled source EM methods (Nagy et .al, 1991) . MT soundings are used for integrated interpretation purposes.
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Transient electromagnetic and seismic prospecting - an analysis of their similarities
More LessA fundamental introduction is presented to the similarities that exist between the transient electromagnetic and the seismic prospecting methods.
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Structure, stratigraphy, fluid content and field procedures for seismic and EM
Authors A. M. Ziolkowski, W. Peet, K. -M. Strack, P. Andrieux and K. VozoffThis paper looks at the problem of joint inversion of seismic and electromagnetic data and points to ways in which the acquisition of data in both methods should be improved. The sonic and resistivity logs from the same well often show a marked resemblance. Rocks with high compressional wave velocities, such as carbonates, are often very resistive. Porous permeable rocks with a large fluid content are often very conductive and have lower compressional wave velocities. The conductivity can vary enormously within a porous medium depending on the fluid content. Salt water is much more conductive than gas, for example . This suggests that electromagnetic methods should be used to determine fluid content within a reservoir and thus locate the reserves. The problem with electromagnetic methods is that they have poor resolution when used on their own .
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Integrating long-offset transient electromagnetics (LOTEM) with seismic in an exploration environment
Authors K. -M. Strack and K. VozoffDuring the past decade long-offset transient electromagnetics (LOTEM) was applied to many exploration problems in Africa, Australia, China, Europe, India and the USA . Initially, the technique was applied in areas where Bood seismic data was difficult to obtain. With the experience of ongoing surveys and an improvement in instrumeritation, the main application which is emerging is the combination with seismics to map porosities in carbonate reservoirs. The major problems overcome along the way included acquisition difficulties (strong cultural noise levels, not enough data), data processing difficulties (low signal-to-noise ratios), and interpretation limitations (restricted 3-D modeling capabilities). LOTEM is now a vérsatile and reliable exploration tool .
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Integration of MT, seismic, gravity, and magnetic data for reconnaissance of the Colombian Amazon
Authors W. A. Burgett, A. Orange and R. F. SigalAmoco Production Company integrates the interpretation of magnetotelluric (MT) data with seismic, gravity, and magnetic data for regional basin reconnaissance and prospect evaluation worldwide. Experience shows that : MT data acquisition can be fast and affordable; high quality data suitable for relatively high resolution interpretation can be acquired in most parts of the world; and in many instances MT data has made a critica) contribution to the final interpretation. One case history that demonstrates some of these advantages is described in this paper. MT was used as part of a very broad regional program to study a large, remote, and essentially unexplored area . A seismic program and stratigraphic well tested the interpretation of gravity, magnetic and MT data and the correlation was excellent .
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Papua New Guinea MT: looking where seismic is blind
More LessHydrocarbon exploration in the Papuan fold belt is made extremely difficult by mountainous terrain, equatorial jungle and Chick kanstic Miocene limestones at the surface. The high velocity karstic limestones at or near the surface often renden the seismic technique useless for imaging the subsurface . In such areas Magnetotellurics (MT) provides a valuable capability for mapping subsurface structure. The environment of the Papua New Guinea (PNG) highlands presents a wide range of MT data acquisition and interpretation problems, the most important of which, from an interpretational point of view, are the rugged topography, severe electric staties, and complex two and three dimensional stroclone. The main structural interface which can be mapped with MT, due to the large electrical contrast, is the contact between the resistive Darai limestone and the underlying conductive sediments of the Ieru Formation. Within the Ieru the reservoir of Toro Sandstone does not have sufficient electrical contrast with the surrounding shales to allow its direct mapping. Nevertheless the ability to map the base of the Darai accurately allows the mapping of the Toro by inference since the leru Fonnation maintains a relatively constant thickness. BP, as part of its ongoing exploration program in PNG, pas acquired more than 700 MT sites to aid in structural interpretations.
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Synergetic interpretation of well test and seismic data for reservoir characterization
Authors S. Ronen, C. Economides and G. VarvikA pressure buildup well test is a measurement of bottomhole pressures in a wellbore beginning while the well is flowing and continuing for a period of several hours or days after the well is shut in . After the well is shut in, no force maintains the low pressure at the well and the tendency toward equilibrium results in a buildup of pressure in the wellbore. The pressure perturbation initiated by shutting in the well, expands about the well, and trends in the measured wellbore pressures may be altered whenever the pressure wave encounters a change in rock or fluid properties .
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Lateral prediction of reservoir properties using seismic attributes with well log data
Authors S. Ronen, M. Hattori, S. Geoltrain and P. SchultzSeismic attributes are mathematical transformations of seismic data, typically dove after stacking and imaging (Taner et al, 1979) . Examples are amplitude, instantaneous frequency, P and S velocities, band-limited impedance, apparent dip or azimuth, and others . Rock or petrophysical propertjes (e .g ., porosity, Poisson's ratio, relative shale volume, fluid content, and others) describe the medium itself, and are measured or computed in situ from logs. Seismic attributes carry the promise of indicating such real propertjes, since in some circumstances certain attributes can be expected to correlate highly with specific rock properties (Sonneland et al, 1990)
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Improved reservoir description by use of an integrated approach: application to a gas storage reservoir
Authors P. Y. Dequirez, F. Fournier and V. RichardThe integration of all available information is a key point to improve the description of a reservoir . In particular, seismic data are essential to complete our knowledge of the reservoir between the wells. We illustrate this point through an integrated procedure applied to a gas storage reservoir. This procedure combines different techniques using post-stack seismic data, impedance well logs and geological information. It is divided in three mais steps 1. waveform calibration of the stacked seismic data using wen log-baserf reflectivity 2. generation of inter-well impedances using stratigraphic modelling and inversion 3 . inter-well impedance facies recognition using multivariate statistical techniques and geological interpretation .
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Seismic blind zone detection by image processing techniques
By G. DarcheSeismic blind zones (weak or incoherent reflections) are an important source of mistakes for automatic 2D/3D interpretation softwares, and their detection would save these softwares a substantial computation time. To isolate these blind zones, we apply a recent image processing technique, the SNAKE method, traditionally used for edge detection, and we adapt it to the particular case of seismic images, to find smoothly shaped blind zones . After a description of the SNAKE method, we apply it to our problem, and illustrate the method on a 2D seismic section.
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3D Seismic: An exploration & production tool for the Abu Gharadig Basin, Egypt
Authors M. Nessim, S. M. H. Abedi and M. el ToukhyThe Abu Gharadig Basin is well established as a prolific hydrocarbon bearing province of the Western Desert, Egypt. However, the oil and gas fields discovered so far are moderate to small in site and are trappel in a complex stratigraphic and structural setting. Postulated hydrocarbon generation models indicate that significantly more hydrocarbons (up to 3 billion bbls) have been generated in this basis and have migrated into the available traps. However, the relatively remote location of this area requires careful economic considerapons before commitment to any potential development. Therefore, better means of trap definition is highly desirable .
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Prestack seismic signatures of actual and synthetic reflections from different petrophysical targets
Authors G. Ravagnan, A. Mazotti, A. MMelis and G. BernasconiWe describe the reflections from gas sands, lignitic sands and cinerites of a marine seismic dataset in terms of their Amplitude Vs .Offset (AVO) responses . As an additional aid to the interpretation we also make use of the Phase and Frequency Vs . offset (PVO and FVO) indicators . These offset dependent signatures are related to the different petrophysical, and thus elastic, situations or to peculiar interference patterns and may help to distinguish the amplitude anomalies observed in the stack sections . It is in fact well known that the presence of volcanic sediments or of lignites is a common cause of "false" bright spots .
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