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- Volume 17, Issue 1, 1999
First Break - Volume 17, Issue 1, 1999
Volume 17, Issue 1, 1999
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The Year Ahead
1999 will be a challenging year for the oil industry. Low oil prices and company cutbacks in budgets and people have set the scene for an uncomfortable time for the oilfield services sector. The question is how uncomfortable. First Break reports. 1999 for oil companies, contractors and suppliers of equipment and services looks as though it will see the playing out of a scenario which was sparked primarily by the collapse over a year ago of the seemingly unstoppable boom in the economies of South East Asia. The global fallout from that reverse in fortunes combined with a vulnerable oil price due to chronic over-supply has provoked a sharp reaction in the oil industry, the full impact of which has still to be measured. We are currently in the eye of a storm with major league consolidations, defensive mergers between smaller companies, spending cuts and job losses all part of the mix against the background of uncertainty over the future trend in oil price.
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Fracture-related amplitude variations with offset and azimuth in marine seismic data
Authors C. MacBeth, H. Jakubowicz, W. Kirk, X.Y. Li and F. OhlsenFractures are of great interest for hydrocarbon production. In particular, they can provide conduits for fluid flow, hence knowledge of their distribution and orientation can be critical, especially for horizontal wells. Unfortunately, most fractures are relatively small, and well beyond the imaging range of conventional seismic data. On the other hand, it is increasingly recognized that fractures do have a strong influence on shear-wave energy (S waves). Indeed, amplitude variations in stacked (qS2) shear-wave data have successfully been used to identify productive fracture clusters in the Austin Chalk formation in Texas (Mueller 1991). Although seismic information on fracturing is most readily obtained from shear waves, direct measurements of shear-wave energy require both specialized sources and multicomponent receivers, and are not feasible in marine environments, except perhaps at the sea floor. Of importance is the fact that fractures have an impact on the entire seismic wavefield, with the imprint of the fracture symmetries leading to a general azimuthal behaviour. As a result, although compressional (P) waves are relatively insensitive to fracturing at near offsets, they can become linked to the larger effects experienced by the shear-waves through mode conversion at oblique incidence, and also through their own specific sensitivity. Thus, it is feasible that anisotropic variations in P-wave behaviour can provide a way of obtaining information on fracture properties at subseismic scales. (MacBeth 1995). This then offers a potential means of studying fracture distributions and orientations in marine areas. In this paper we present evidence to show that information on both the presence and nature of fractures can be obtained from conventional marine (i>P-wave) seismic data using AVO (amplitude variation with offset) analysis. In particular, our results demonstrate that fracture-related AVO has a distinct anisotropic (directional) behaviour that can be linked directly to the azimuthal orientation of the fractures. Indeed, this is consistent with the numerical study of Mallick & Frazer (1991), and has previously been observed in land data for a variety of fractured gas reservoirs (Lynn et al. 1996). However, to our knowledge, the results given in this paper constitute the first example of this phenomenon for a marine dataset.
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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)