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- Volume 3, Issue 9, 1985
First Break - Volume 3, Issue 9, 1985
Volume 3, Issue 9, 1985
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Stratifications and reflections
More LessThe term 'stratification' is used to denote the layered arrangement within sedimentary sequences. According to the International Stratigraphic Guide (Isse 1976), 'a geologic stratum is a layer (a generally tabular body) of rock characterised by certain unifying characters, properties, or attributes that distinguish it from adjacent layers'. From the point of view of reflection seismology, only stratification manifested by changes of acoustic properties is important because only such a stratification may influence the reflection seismic response. Acoustic properties within a layer may be either constant or variabie, the variation being either parallel to stratification, or perpendicular to it. Both types of variation might be present simultaneously resulting in an oblique variation. A boundary between two strata is expressed by more or less abrupt changes of acoustic properties and represents a reflector. The reflection seismic response is influenced by stratification in two ways: by the properties of individual reflectors, and by the properties of stratified systems. This paper's aim is to discuss, from the interpreter's point of view, the influence of both individual reflectors and stratified systems on the reflection seismic response.
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A look beyond the CMP concept
By M.J. KuhnFor the majority of present generation geophysicists the common mid-point (CMP) technique is the natural way to acquire and process seismic reflection data. Somehow it is always taken for granted that the paths to improvements in acquisition and processing lead through and not around the CMP concept. More often than not, the question of using non-CMP techniques is not even raised. Over the last quarter of a century our industry has become rigidly attached to a concept which in most geophysical exploration circles is no longer subjected to critical examination. It seems, however, that in the era of interactive graphics and supercomputers the CMP concept is no longer immune to critical review. The CMP method was developed independently by several geophysicists, but the first patent application was apparently filed in 1950 by H. Mayne. With the introduction of computers, digital processing systems began to gradually replace the analogue systems. The CMP concept was admirably suited for digital processing and soon it became almost unthinkable to implement it in any other way but digitally. In the early stages of digital seismic processing the question of whether the CMP method could be dispensed with was not seriously investigated, primarily because the production of CMP stacked traces was considered the zenith of the state of the art and also because the early seismic computer could not do much else. The CMP technique became even more popular when a velocity analysis based on scanning of the CMP gathers was introduced (Taner and Koehier 1969). However, the annoying property of the stacking velocity to vary with azimuth of the seismic line was recognised much later (Hubral 1976). This and other related findings have caused considerable inconvenience to the proponents of 3-D CMP data acquisition and processing. Today the basic elements needed to write a new chapter in seismic data acquisition and processing are in place; most larger oil companies have supercomputers, interactive graphics capabilities and rather well-trained geophysicists. This article is intended to show that CMP techniques as practised today are tantamount to destruction of a good part of the information content of the input field data, and that given sufficient computing power, alternative techniques may be designed which do not suffer similar drawbacks.
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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)