US 6,131,071 A · Spectral decomposition for seismic interpretation

Abstract

The present invention is directed generally toward a method of processing seismic data to provide improved quantification and visualization of subtle seismic thin bed tuning effects and other sorts of lateral rock discontinuities. A reflection from a thin bed has a characteristic expression in the frequency domain that is indicative of the thickness of the bed: the reflection has a periodic sequence of notches in its amplitude spectrum, with the notches being spaced a distance apart that is inversely proportional to the temporal thickness of the thin bed. Further, this characteristic expression may be used to track thin bed reflections through a 3-D volume and estimate their thicknesses and lateral extent. The usefulness of this invention is enhanced by a novel method of frequency domain whitening that emphasizes the geologic information present within the spectrum. Although the present invention is preferentially applied to a 3-D seismic volume, it is alternatively applied to any collection of spatially related seismic traces.

Claims40

Dependent claims

A method for the exploration of hydrocarbons, comprising the steps of:

(a) obtaining a representation of a set of seismic traces distributed over a pre-determined volume of the earth containing subsurface features conducive to the generation, migration, accumulation, or presence of hydrocarbons,
said set of seismic traces consisting of at least two different seismic lines, each of said seismic traces being associated with at least one of said seismic lines,
said seismic traces containing digital samples, and,
said digital samples being characterized by at least a time, a position, and an amplitude;
(b) selecting a part of said volume and the seismic traces and digital samples contained therein to define a zone of interest within said volume,
said selected seismic traces being associated with at least two different predetermined seismic lines of said at least two different seismic lines;
(c) transforming at least a portion of said selected seismic traces and said selected digital samples within said zone of interest using a discrete orthonormal transformation, said discrete orthonormal transformation producing transform coefficients from said seismic traces so transformed;
and,
(d) organizing said transform coefficients into a tuning cube for use in seismic exploration, whereby said tuning cube can be used in conjunction with a computer to identify one or more of said subsurface features conducive to the generation, migration, accumulation, or presence of hydrocarbons within said predetermined volume of the earth.

6 more elements

A method of geophysical exploration, comprising the steps of:

(a) obtaining a representation of a set of unstacked seismic traces distributed over a pre-determined volume of the earth containing subsurface features conducive to the generation, migration, accumulation, or presence of hydrocarbons,
each of said unstacked seismic traces being associated with a CMP location and containing digital samples,
wherein said digital samples are characterized by at least a time, a position, and an amplitude;
(b) selecting at least a part of said volume and the unstacked seismic traces and digital samples contained therein to define a zone of interest within said volume,
(c) transforming at least a portion of each of said selected unstacked seismic traces and said selected digital samples within said zone of interest using a discrete orthonormal transformation, said discrete orthonormal transformation
(c 1) being characterized by a plurality of orthonormal basis functions, and
(c2) producing a plurality of transform coefficients associated with said orthonormal basis functions from each of said selected unstacked seismic traces;
(d) selecting a CMP location having a plurality of unstacked seismic traces associated there with;
(e) selecting a predetermined orthonormal basis function;
(f) identifying within each of said selected plurality of unstacked seismic traces a transform coefficient associated with said selected predetermined orthonormal basis function;
(g) determining an angle of incidence for each of said identified transform coefficients;
(h) numerically fitting a function characterized by a plurality of constant coefficients to said angles of incidence and said identified transform coefficients, thereby producing a plurality of coefficient estimates;
(i) calculating a seismic attribute from one or more of said plurality of coefficient estimates;
(j) performing steps (e) to (i) a predetermined number of times, thereby producing a predetermined number of AVO coefficient estimates at said selected CMP location;
(k) performing steps (d) through (j) a predetermined number of times, thereby producing AVO coefficient estimates at a predetermined number of CMP locations;
and,
(l) using said AVO coefficient estimates to identify one or more of said subsurface features conducive to the generation, migration, accumulation, or presence of hydrocarbons within said predetermined volume of the earth.

14 more elements

A method of geophysical exploration, comprising the steps of:

(a) obtaining a representation of a set of seismic traces distributed over a pre-determined volume of the earth,
each of said unstacked seismic traces containing digital samples, and,
said digital samples being characterized by at least a time, a position, and an amplitude;
(b) selecting at least a part of said volume and the seismic traces and digital samples contained therein to define a zone of interest within said volume,
(c) transforming at least a portion of each of said selected seismic traces and said selected digital samples within said zone of interest using a discrete orthonormal transformation, said discrete orthonormal transformation
(d1) being characterized by a plurality of orthonormal basis functions, and
(d2) producing a plurality of transform coefficients associated with said orthonormal basis functions;
(d) organizing said transform coefficients into a tuning cube,
said tuning cube being composed of tuning cube traces,
each of said tuning cube traces containing at least a portion of said organized transform coefficients, and
each of said tuning cube traces being associated with a surface location above said predetermined volume of the earth;
and,
(e) calculating at least one seismic attribute from said tuning cube, said at least one seismic attribute being used in conjunction with a computer to identify subsurface stratigraphic and structural formations conducive to the generation, migration, or trapping of hydrocarbons within said predetermined volume of the earth.

10 more elements

A method for the exploration of hydrocarbons, comprising the steps of:

(a) obtaining a representation of a set of seismic traces distributed over a pre-determined volume of the earth,
each of said seismic traces being associated with a location above said predetermined volume of the earth, and,
each of said seismic traces containing digital samples;
(b) selecting a predetermined number of seismic traces and a plurality of digital samples within each of said selected seismic traces to define a zone of interest within said predetermined volume of the earth;
(c) choosing one of said predetermined number of seismic traces;
(d) selecting an analysis window within said zone of interest, said analysis window encompassing at least two of said plurality of digital samples within each of said selected seismic traces;
(e) transforming said digital samples encompassed by said analysis window within said chosen seismic trace using a discrete orthonormal transformation,
said discrete orthonormal transformation producing a plurality of transform coefficients when so used;
(f) calculating a seismic attribute from said plurality of transform coefficients;
(g) repeating steps (d) through (f) a predetermined number of times, thereby creating a plurality of seismic attributes associated with said chosen seismic trace,
said plurality of seismic attributes taken together comprising a seismic attribute trace;
(h) performing steps (c) through (g) a predetermined number of times, thereby creating a predetermined number of seismic attribute traces;
and,
(i) forming said predetermined number of seismic attribute traces into a tuning cube for use in seismic exploration for hydrocarbons within said predetermined volume of the earth.

11 more elements

A method for the exploration of hydrocarbons, wherein a predetermined volume of the earth containing structural and stratigraphic features has been specified, comprising:

(a) obtaining a representation of a set of spatially related seismic traces distributed over said pre-determined volume of the earth,
said spatially related seismic traces containing signals representative of at least a portion of said structural and stratigraphic features,
each of said spatially related seismic traces consisting of a plurality of digital samples, and,
each of said spatially related seismic traces being characterized by at least a location on a surface of the earth;
(b) selecting a target location on a surface of the earth, said target location having at least three seismic traces proximate thereto;
(c) selecting at least three traces from said at least three seismic traces proximate to said target location;
(d) specifying an analysis window that includes at least one digital sample from each of said selected at least three seismic traces;
(e) fitting a function characterized by a plurality of constant coefficients to at least a portion of said included digital samples and said selected at least three trace locations, thereby producing a plurality of coefficient estimates;
(f) calculating a seismic attribute from at least one of said plurality of coefficient estimates;
(h) storing said seismic attribite at a position representative of said target location;
(i) repeating steps (b) through (h) for at least two additional target locations, thereby creating a stored plane of seismic attributes, said stored plane of seismic attributes being used to identify subsurface structural and stratigraphic features that are conducive to the migration, accumulation, or presence of hydrocarbons, conducive to the migration, accumulation, or presence of hydrocarbons.

8 more elements

Dependencies are inferred from the claim text.

Spectral decomposition for seismic interpretation

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Spectral decomposition for seismic interpretation

Life of this patent

Abstract

Claims40