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- Volume 21, Issue 2, 2003
First Break - Volume 21, Issue 2, 2003
Volume 21, Issue 2, 2003
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A story of two men and the beginning of the Italian oil industry
Authors F. di Cesare and F. GuidiThis is a short story which could be summarized in a few short chapters starting with the enterprise of Henry Salvatori, a young Italian emigrant in the USA, followed by the birth and development of the oil industry in Italy, and then, by the key decision of Enrico Mattei not to liquidate AGIP after the Second World War. Destinies, as usual, become entwined and, even in a story as short as this, part of the plot must be the role played by Salvatori’s seismic endeavours in persuading Enrico Mattei to make the decision which ensured the growth of AGIP into the company we know today. The story tellers are Franco di Cesare and Francesco Guidi, who both worked at AGIP.
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How to optimize pilot sweep of vibratory sources in seismic surveys
Authors Y. Tyapkin, E.A. Robinson, M. Ewing and J.L. WorzelProf Yuriy Tyapkin, of the Ukrainian State Geological Prospecting Institute, and Enders A. Robinson, Maurice Ewing and J. Lamar Worzel professor emeritus of geophysics, Columbia University, New York City, have been developing a solution to what they believe is a longstanding omission in the effectiveness of the pilot sweep of vibratory sources in seismic survey acquisition. Successful application of high-resolution seismic methods requires the evaluation of each element in the seismic system to ensure that each part makes an optimal contribution. This principle extends from seismic signal radiation through to data processing where good performance and correct parameter selections are required. Unfortunately, unlike the data processing stage, this important field operation is not usually optimised. The purpose of our study was to eliminate the obvious non-co-ordination of field operations with data processing so that both stages co-operate fully and optimally. We addressed not only the beginning of the seismic system, the source of the seismic signal, but the system as a whole. To validate its feasibility, this optimisation was based upon the Vibroseis technique, primarily because of its versatility in controlling the signal spectrum. The method illustrated here for optimising a pilot sweep signal, using synthetic data as examples, allows the best data quality to be achieved with limited energy expenses. The reflectivity function, also called the impulse response, allows geophysicists to investigate structural and reflective properties of geologic boundaries in the subsurface. Unfortunately the response is always distorted by the filtering (smoothing) effect of a wavelet radiated by a seismic source (Robinson and Treitel, 1980). In order to remove or, more exactly, to reduce the impact of this factor, special processes known as deconvolution are widely used. Unless such procedures have been implemented, seismic data cannot be interpreted in detail and with confidence. Importantly, the deconvolution methods, among which the Wiener filters are most widespread, usually have an optimum character. Favourable conditions for the subsequent resolution improvement should be created, even in the field, so that both stages of the seismic system, field operations and data processing, blend harmoniously and concur in achieving their common objective. The problem, easily solved in this case, is most germane to Vibroseis systems, controllable and hence adaptable to the seismic properties of any area. The Vibroseis technique, conceived more then 40 years ago, is now mature and deployed by a large variety of users in the oil industry. In recent years, vibrators have been the energy sources for over half of the 2D/3D seismic crews operating worldwide. Strangely enough, however, most if not all of them have not benefited from real optimisation of the sweep signal, the most important parameter of vibratory sources. As a matter of fact, any attempt to optimise the pilot sweep at the input to the seismic system made without reference to the properties of the system (Goupillaud, 1976; Dougherty and Justice, 1988) is doomed to fail. This is because it bears no relation to the optimum result at the output of the system. Instead of special preliminary quantitative estimations, a testing of various sweep parameters – the frequency band and the type of non-linearity with associated characteristics foremost among them – followed by visual (so, subjective) analysis of the results is implemented in order to choose a suitable vibratory signal (e.g. Pritchett, 1994). This conventional approach sometimes causes a highly inefficient distribution of the generated energy along the frequency axis, for example, groundless significant extra expenses, on the one hand, and deterioration of the data quality compared with the best (optimum) that should and could be attained, on the other. A method that takes the properties of the entire seismic exploration system into account was first developed in Widess (1982) for optimisation of the pilot sweep. It supposed a special filter to be used for optimising a local criterion for the vertical resolving power of the system. However, the Wiener deconvolution filter, which has enjoyed widespread use for source wavelet deconvolution in exploration seismology, is certain to be more helpful in such a case. Preoptimisation of the signal spectrum at the input to the Wiener deconvolution filter was described in Franks (1969). To avoid some obstacles, however, the solution was simplified and reduced to a band-limited form. A method for optimisation of the spectrum of the pilot sweep which overcomes the shortcomings of the Vibroseis technique described above is the subject here enabling the most efficient use of the radiated energy as a result of its rational distribution along the frequency axis. Emitting the optimum pilot sweep along with finishing Wiener deconvolution filtering at the very end of processing provides the best data quality under a natural restriction on the source energy available.
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Chałupki Dębniańskie Field: Improving drilling success in shallow gas reservoirs with VectorSeis
Authors E. Gruszczyk, Z. Tresnioswki, P. Misiaczek, P. Brettwood and J. TessmanEdward Gruszczyk, Zygmunt Trzesnioswki and Piotr Misiaczek of Geofizyka Krakow, Poland with Paul Brettwood (UK) and Jon Tessman (USA) of Input/Output provide a case study comparing the performance in the field of I/O VectorSeis sensor technology with conventional analogue geophone systems. In the spring of 2002, a field experiment was conducted over a gas field in southeast Poland. The primary objective was to characterize the response of the I/O VectorSeis sensor in a direct comparison with conventional analogue geophone systems. Both dynamite and Vibroseis sources were tested during the course of the experiment. Analysis of the acquired datasets demonstrated clearly that, in this relatively shallow (160 m - 800 m depth range) clastic depositional environment, VectorSeis sensors not only matched the results of the analogue geophones but also produced datasets with superior vertical resolution. In addition to the conventional compressional datasets, converted wave data were also acquired. These demonstrated that high quality converted wave data could be acquired in a cost-effective manner and that they could solve a number of imaging problems directly related to the presence of multiple stacked gar reservoirs. Mapping of the PS data into PP time also demonstrated that the PS data had similar apparent frequency response when compared to analogue geophone compressional data.
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The future of the upstream oil and gas industry: a City perspective
By R. ArnottDr. Robert Arnott, senior research fellow, at the Oxford Institute for Energy Studies, and former oil analyst, provides an insight into how the investment community views the oil and gas E and P industry, with particular reference to the UK North Sea. The article is based on Dr Arnott’s keynote presentation at last December’s PETEX event in London and highlights themes included in his recent book ‘Oil company crisis: managing structure, profitability and growth’.
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Land seismic technology: Where do we go from here?
By I. JackIn this article, Ian Jack of BP*, provides an overview of land seismic technology today serving as an introduction to our Special Topic on land seismic which includes articles on sensor technology, optimising the pilot sweep of vibratory sources, and seismic applications in archaeology investigations. Jack says that pressure is mounting for changes in land seismic technology. These pressures come from research findings of ways to improve geophysical methodology, and from hardware, operational, societal and cost issues which are encountered while using existing technology stretching it into higher and higher channel counts. They also come from the development of technology in parallel industries.
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Ancient Roman remains in Israel provide a challenge for physical-archaeological modelling techniques
Authors L.V. Eppelbaum, Z. Ben-Avraham and S.E. ItkisIsraeli geoscientists Lev V. Eppelbaum, Zvi Ben-Avraham and Sonya E. Itkis provide an insight into some of the geophysical investigation options available for archaeological investigations of Ancient Rome in Israel. The territory of Israel, in spite of its comparatively small size (21 000 km2), is very attractive for archaeologists in view of its dramatic ancient and Biblical history. Many authors (for instance, Kenyon, 1979; Reich, 1992; Mayer, 1996) note that the location of archaeological sites on Israeli territory is the densest in the world. Ancient Roman remains total more than 10% of the total number of discovered archaeological objects. The Roman remains, according to accumulated experience, occur in the subsurface layer at a depth from 0.5 to 3 m and usually retain their initial correct (quasi-correct) geometrical shape. Geophysical methods have been successfully applied to the search and location of archaeological remains as a rapid, effective and non-invasive way to reveal a broad range of targets: buried walls, columns, foundations, chambers, water pipe systems and high temperature features (e.g. Aitken, 1974; Clark, 1986; Tsokas & Rocca, 1986; Vogell & Tsokas, 1993; Parasnis, 1997; Desvignes et al. 1999; Sambuelli et al. 1999; Gaffney et al. 2000; Eppelbaum et al. 2001). Barker (1982) emphasizes that ‘Unlike the study of ancient document, the study of a site by excavation is an unrepeatable experiment’. Geophysical non-invasive experiments, which apply methods basing on different physical principles and perform surveys on various scales with a range of locations for the sensor using different combinations of method, practically have no limitations. Geophysical surveys can provide a ground plan of cultural remains before excavations, or they may even be used instead of excavating. Road and plant construction work in Israel, as well as the selection of areas for various engineering and agricultural purposes, are usually preceded by detailed geophysical (first of all, magnetic) investigations. This is intended to help judge the possible archaeological significance of the area under scrutiny.
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Volumes & issues
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Volume 42 (2024)
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Volume 41 (2023)
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Volume 40 (2022)
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Volume 39 (2021)
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Volume 38 (2020)
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Volume 37 (2019)
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Volume 36 (2018)
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Volume 35 (2017)
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Volume 34 (2016)
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Volume 33 (2015)
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Volume 32 (2014)
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Volume 31 (2013)
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Volume 30 (2012)
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Volume 29 (2011)
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Volume 28 (2010)
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Volume 27 (2009)
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Volume 26 (2008)
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Volume 25 (2007)
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Volume 24 (2006)
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Volume 23 (2005)
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Volume 22 (2004)
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Volume 21 (2003)
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Volume 20 (2002)
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Volume 19 (2001)
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Volume 18 (2000)
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Volume 17 (1999)
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Volume 16 (1998)
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Volume 15 (1997)
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Volume 14 (1996)
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Volume 13 (1995)
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Volume 12 (1994)
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Volume 11 (1993)
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Volume 10 (1992)
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Volume 9 (1991)
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Volume 8 (1990)
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Volume 7 (1989)
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Volume 6 (1988)
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Volume 5 (1987)
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Volume 4 (1986)
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Volume 3 (1985)
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Volume 2 (1984)
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Volume 1 (1983)