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- Volume 25, Issue 12, 2007
First Break - Volume 25, Issue 12, 2007
Volume 25, Issue 12, 2007
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Industry fighting the odds to meet increasing global oil and gas demand
By A. GouldLet me start by looking again at something I presented back in 2003. At that time, this slide summarized the task that we saw facing the industry. The figures, from the 2002 IEA World Energy Outlook, forecast that 2002 oil production of 77 million b/d would need to grow to 88 million by 2010. The same forecast also predicted that this increase would be dwarfed by the 33 million b/d required to replace production lost to decline. We now know that world oil production is likely to reach the 88 million b/d level perhaps as early as this coming winter—almost two years ahead of time. So what happened to change this picture and why is the industry challenged in expanding capacity to meet the increased demand?
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Increased resolution and penetration from a towed dual-sensor streamer
Authors D.H. Carlson, A. Long, W. Söllner, H. Tabti, R. Tenghamn and N. LundeDavid Carlson, Andrew Long, Walter Söllner, Hocine Tabti, Rune Tenghamn, and Nils Lunde discuss the theory behind a towed dual-sensor developed by Petroleum Geo-Services to operate at deeper depths and deliver de-ghosted data.
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Lessons through time in 4D seismic
More LessMichael Tang, Robert Ross, and Robin Walker of WesternGeco discuss experience with a new proprietary system designed to reduce time-lapse noise by accurately repeating source and receiver positions in relation to 4D vintage surveys.
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Practical applications for node seismic
SeaBed Geophysical, wholly-owned subsidiary of SeaBird Exploration, is one of the few companies to have carried out ocean bottom 4C seismic using seabed node receivers. Here the company provides this update on a technology option that has still to find its place in the marine seismic business.
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Optimizing USBL subsea positioning systems
By S. PartridgeWith increasing demand for subsea positioning systems to meet the requirements of ocean bottom seismic and electromagnetic surveys, Simon Partridge, engineering director, Sonardyne outlines some of the practical considerations for obtaining optimal results from the latest ultra-short baseline (USBL) techniques.
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Subsurface correlation in the Upper Carboniferous (Westphalian) of the Anglo-Dutch Basin using the climate stratigraphic approach
Authors M. de Jong, S.D. Nio, D. Smith and A.R. BöhmThe Upper Carboniferous play in the Anglo-Dutch offshore continues to be a challenging exploration target, as well as providing a significant portion of the region’s existing gas production. Despite the application of various techniques, a secure genetic stratigraphic framework, applicable at field as well as regional level, has continued to be elusive. This paper presents such a framework, using only routine wireline log data supported by the limited amount of published stratigraphic information. In addition to their conventional properties, wireline logs conceal information encoded in their waveform properties. Treated as complex waveforms, logs are amenable to a range of ‘time-series’ analytical methods. Applying the concepts of global cyclostratigraphy (Perlmutter et al., 1990, 1998), so-called spectral trend (or INPEFA) curves, which show uphole changes in the waveform properties of the data, are used to generate a framework of near-synchronous well-to-well correlations. Using this approach, we have subdivided the top part of the Carboniferous succession – essentially the Westphalian – into nine first-order stratigraphic packages, W1000 to W9000 from bottom to top. Most of these packages can be further subdivided into second-order packages, and some of these into third-order packages, taking the resolution of this scheme down to a few tens of metres, or even to a few metres. These packages have been identified in a total of over 50 wells in the offshore UK and offshore Netherlands sectors.Comparison with the limited information publicly available on previous stratigraphic classifications indicates that our scheme is far more widely applicable, and probably considerably more reliable than any other previously attempted at the regional scale. Also, the scheme has the potential for further subdivision, to the limit of resolution of the log data, at the local (field/reservoir) scale. As our subdivisions are inherently time-related, they will now serve as the most appropriate framework within which to understand basin paleogeographic development, and the distribution of reservoir and seal facies within the Upper Carboniferous. The purpose of the paper is two-fold. First, we present our stratigraphic scheme and the method of climate stratigraphy upon which it is based. Second, we show how systematic application of this method in well-to-well correlations leads to the identification of important intra-formational unconformities.
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Practical Gassmann fluid substitution in sand/shale sequences
By R. SimmWhen performing fluid substitution on log data Gassmann’s (1951) model is the general tool of choice. Whilst the equations and software implementations are straightforward, there are potential pitfalls. Several authors have noted the need for quality control (QC) of Gassmann input parameters (e.g., Smith et al., 2003; Han and Batzle, 2004; and Skelt, 2004 have described the problem of erroneous fluid substitution results in laminated sand/shale intervals). Despite the warnings, however, it is not clear what the interpreter should do in the application of Gassmann to mitigate the chances of erroneous results. Nor is it clear, for example, in the case of shaley sand scenarios, what the right answer should be. The approach taken here is essentially pragmatic, suggesting an adaptive Gassmann workflow that can be modified to give intuitive results. The paper illustrates the need to QC the dry rock data implicit in Gassmann’s model and to condition the dry rock data used in fluid substitution. The following discussion assumes that good quality log data, including logs of shear wave velocity Vs, are available. No discussion will be made here of issues such as log editing and Vs prediction.
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Dip and azimuth displays for 3D seismic interpretation
Authors R.M. Dalley, E.C.A. Gevers, G.M. Stampfli, D.J. Davies, C.N. Gastaldi, P.A. Ruijtenberg and G.J.O. VermeerIn the last decade, the sophistication of three-dimensional (3D) seismic data has been applied increasingly to the more precise definition of geological structures containing oil and gas accumulations. In favourable circumstances, it is even possible to define the limits of the hydrocarbons themselves and, in rare cases, show the retreat of hydrocarbon-water contacts in response to sustained oil and gas production. In the early days, 3D seismic data were interpreted in a manner comparable to the interpretation of a grid of two-dimensional (2D) profiles. Equispaced in-lines and cross-lines were abstracted from the total data volume and, with the additional benefit of arbitrary lines and time-slices, interpreters were able to construct time contour maps of selected horizons with increased confidence. However, a significant percentage of the total volume of acquired data was by-passed in this process, and it was not until the advent of interactive trace interpretation systems (the so called work stations) that the interpretation of the full data volume became feasible. Feasibility turned into reality with the development of new and powerful automatic tracking (horizon picking) programs. These enable the interpreter to incorporate data from every common midpoint (CM) in the data volume. In some more advanced programs, selected ‘seed’ lines, which are initially interpreted by hand, are fed to the automatic tracking programs which, in turn, extrapolate the horizon pick until every CMP in the survey has been covered. For any given reflection horizon it is thus possible to generate files of two-way time, amplitude, instantaneous phase, etc. in a framework of x,y coordinates. These files permit the calculation of additional horizon attributes, especially dip and azimuth (Shell Internationale Petroleum Maatschappij BV 1988. Horizon processing techniques for recognition of structural geology on 3D seismic. Research Disclosure 29473). This paper is concerned with the determination and display of the latter two attributes. It will be shown that, with carefully chosen colour display parameters, subtle laterally continuous features that would have been overlooked during traditional interpretation may be interpreted with relative ease and confidence as having geological significance. The techniques employed have much in common with those used in photogeology.
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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)