- Home
- A-Z Publications
- First Break
- Previous Issues
- Volume 6, Issue 12, 1988
First Break - Volume 6, Issue 12, 1988
Volume 6, Issue 12, 1988
-
-
Detection of zero-offset seismic reflections
More LessIn one-dimensional (1D) seismic inversion one may either estimate the acoustic impedance as a function of two-way traveltime or one may identify discrete layers. We have chosen the latter approach and assume that the subsurface consists of horizontal layers, where each layer is characterized by three parameters: the wave propagation velocity, the density, and the thickness. In principle, it is possible to estimate both the velocity and the density of each layer using the amplitude and traveltime of both primary and multiple reflected pulses. In practice, however, this procedure is unstable. Therefore, the geometrical spreading is computed from known stacking velocities, and only the acoustic impedance of each layer is estimated. From a known source waveform and zero-offset seismie data, the primary reflections are estimated using a least-squares detection scheme. Geometrical spreading and transmission losses are corrected for and multiple reflections may also be taken into account. The output from the procedure is a section consisting of reflection coefficients as a function of two-way traveltime or depth. The reflection coefficients are computed in true amplitude since all elastic wave propagation effects for a point source have been taken into account. Data examples using an airgun array, a single airgun and a single watergun show that it is possible to estimate the reflection coefficients reliably down to the arrival of the first water-layer multiple reflection. In order to identify deeper layers, a more general inversion scheme and/or multichannel seismic data are needed. In this case the detection algorithm may be used to generate an initial model for the more complete inversion algorithm.
-
-
-
Modelling study of tuning effects for the calculation of the thickness and areal extent of thin beds
Authors R. Tatalovic, J.A. McDonald and G.H.F. GardnerSeismic resolution has been studied theoretically by many researchers using numerical models; typically, one-dimensional (1D) synthetic sections over thinning beds. Although numerical models are useful, physical models provide additional insight into such problems. Research into the physical modelling of thin beds has been conducted at the Seismie Acoustics Laboratory (SAL) at the University of Houston for some years. In this article, the problem of vertical resolution is examined in terms of how accurately the thickness of a thin bed can be calculated, and the problem of horizontal resolution is that of how precisely the termination of a thinning bed can be determined. Although the problem of resolution is often divided into two parts, horizontal and vertical resolution are considered to be interdependent since, for the correct estimation of reservoir size, both the horizontal and the vertical dimension of a layer must be determined. It will also be shown that improved horizontal resolution enables more accurate thickness calculations.
-
Volumes & issues
-
Volume 42 (2024)
-
Volume 41 (2023)
-
Volume 40 (2022)
-
Volume 39 (2021)
-
Volume 38 (2020)
-
Volume 37 (2019)
-
Volume 36 (2018)
-
Volume 35 (2017)
-
Volume 34 (2016)
-
Volume 33 (2015)
-
Volume 32 (2014)
-
Volume 31 (2013)
-
Volume 30 (2012)
-
Volume 29 (2011)
-
Volume 28 (2010)
-
Volume 27 (2009)
-
Volume 26 (2008)
-
Volume 25 (2007)
-
Volume 24 (2006)
-
Volume 23 (2005)
-
Volume 22 (2004)
-
Volume 21 (2003)
-
Volume 20 (2002)
-
Volume 19 (2001)
-
Volume 18 (2000)
-
Volume 17 (1999)
-
Volume 16 (1998)
-
Volume 15 (1997)
-
Volume 14 (1996)
-
Volume 13 (1995)
-
Volume 12 (1994)
-
Volume 11 (1993)
-
Volume 10 (1992)
-
Volume 9 (1991)
-
Volume 8 (1990)
-
Volume 7 (1989)
-
Volume 6 (1988)
-
Volume 5 (1987)
-
Volume 4 (1986)
-
Volume 3 (1985)
-
Volume 2 (1984)
-
Volume 1 (1983)