Communications – electrical: acoustic wave systems and devices – Seismic prospecting – Land-reflection type
Patent
1996-07-01
1998-05-26
Lobo, Ian J.
Communications, electrical: acoustic wave systems and devices
Seismic prospecting
Land-reflection type
367 24, G01V 136
Patent
active
057577234
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of processing data representing energy passing through a medium and including energy subjected to more than one reflection within the medium.
Such a method may be used in medical imaging and non-destructive evaluation, where a sample is irradiated with energy, for instance in the form of x-rays or ultrasound, in order to determine the internal structure of the sample non-invasively. Such a method may also be used in the processing of seismic reflection data, and this application of the method will be described in detail so as to illustrate the invention.
2. Description of the Related Art
Seismic reflection data consists of "primaries" and "multiples". "Multiple" is the term used in exploration seismology for energy which has been reflected downwards at least once before being detected by a seismic sensor. Multiples are classified as free-surface or internal multiples, and by their order. Free-surface multiples experience a downward reflection at the free-surface whereas internal multiples have the downward reflection at a reflector below the free-surface. In land seismic exploration, the free-surface is the upper surface of the earth whereas, in marine seismic exploration, the free-surface is the surface of the sea. A multiple can consist of a combination of free-surface and internal downward reflections. First order multiples experience a single downwards reflection, second order multiples experience two downwards reflections, and so on.
Similarly, transmission data may be contaminated by multiples. In this case, all internal multiples undergo an even number of reflections between the source and the receiver. The primary data relates to energy which has not undergone multiple reflections between source and receiver.
Since almost all processing assumes that the data consists of primaries, it is important to remove multiply reflected energy. If multiples are not removed they may (1) be misinterpreted as primaries or (2) interfere with primaries. This in turn can lead to false or inaccurate target identification and characterisation. The goal of multiple suppression methods is to remove this troublesome component, for instance of seismic reflection data, and thereby enhance the ability to process, to interpret and ultimately to make effective exploration and production decisions.
Multiple suppression is a long-standing problem in exploration seismology. Known techniques include:
There are many cases where these procedures are effective. However, there are also many instances where multiples remain a serious problem. The reason is that the available procedures make assumptions about the nature of the earth that are often violated in practice. One of the assumptions made by methods (1) and (2) is that the earth is one dimensional (1D) with horizontal reflectors, that is the earth consists of horizontal layers which are horizontally uniform. Curved and/or dipping reflectors and/or lateral variations in the overburden can cause problems for these 1D methods.
Methods (3) and (4) can accommodate a multi-dimensional earth. However, method (3) requires precise knowledge of the reflectors causing both the upward and downward reflections (eg see J. Wendel Wiggins, Geophysics, Vol 53 No 12, December 1988, pp 1527-1539). Method (4), the surface removal method, requires knowledge of the reflector causing the downward reflection and the source signature. For the latter method, the data transformation which removes a surface in effect removes all the downward reflections that occur at that surface.
It has been suggested (Berkhout A. J., 1982, Seismic Migration: Imaging of Acoustic Energy by Wavefield Extrapolation, Theoretical Aspects, section edition, Elsevier Science Publ. Co. Inc., pp 211-218) that the surface removal method (4) originally applied to free-surface multiples be applied in a step-wise surface stripping manner. That is, in the marine case, after free-surface multiples due to the air-water interface (sea surface)
REFERENCES:
patent: 4209854 (1980-06-01), Ruehle
patent: 5365492 (1994-11-01), Dragoset Jr.
P.M. Carvalho et al, SP1.5, "Nonlinear Inverse Scattering for Multiple Suppression . . .", pp. 1093-1095.
M. Razavy, J. Acoust. Soc. Am., Vol. 58, No. 5, "Determination of the wave velocity in . . .", pp. 956-963, Nov. 1975.
H. E. Moses, Physical Review, Vol. 102, No. 2, "Calculation of the Scattering Potential . . .", pp. 559,567, Nov.1995.
J. Wendell Wiggins, Geophysics, Vol. 53, No. 12, "Attenuation of complex water-bottom . . .", pp. 1527-1539, Dec. 1988.
A. J. Berkhout, Seismic Migration, "Imaging of Acoustic Energy by Wave Field Extrapolation", pp. 185,219.
Riley & Claerbout, 2-D Multiple Reflections, pp. 592-618.
Weglein, Boyse & Anderson, Geophysics, Vol. 46, No. 8, Aug. 1991, "Obtaining three-dimensional velocity information . . .".
Stolt and Jacobs, Inversion of Seismic Data in a Laterally Heterogeneous.
Weglein & Stolt, The Wave Physics of Downward Continuation, Wavelet Estimation, and Volume and Surface Scattering.
Gasparotto Fernanda Araujo
Weglein Arthur Benjami
Atlantic Richfield Company
Lobo Ian J.
Schlumberger Technology Corporation
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