US4646239A — Method of seismic exploration including processin…

Claim 1

Independent Claim 88 words

A method of seismic exploration including processing a plurality of seismic signals to quantitatively distinguish among seismic events, comprising the steps of: obtaining an incident angle ordered gather of seismic signals; obtaining a measure of the reflection coefficient as a function of incident angle for selected seismic events within the incident angle ordered gather of seismic signals; and developing sets of attributes descriptive of variations in the amplitude of the seismic signal as a function of incident angle from the reflection coefficient to quantitatively distinguish among seismic events.

Claim 2

Independent Claim 88 words

A method of seismic exploration including processing a plurality of seismic signals to quantitatively distinguish among seismic events, comprising the steps of: obtaining an incident angle ordered gather of seismic signals; obtaining a measure of the reflection coefficient as a function of incident angle for selected seismic events within the incident angle ordered gather of seismic signals; and developing sets of attributes descriptive of variations in the amplitude of the seismic signal as a function of incident angle from the reflection coefficient to quantitatively distinguish among seismic events.

Claim 3

Dependent Claim 27 words

The method of claim 1 further including the step of: overlaying selected attributes of the sets of attributes onto a corresponding seismic section of the seismic signals.

Claim 4

Dependent Claim 72 words

The method of claim 1 wherein the sets of attributes includes: a first set of attributes for inferring changes in formations properties including ##EQU5## where Z is the average compressional impedance of adjacent formations; α is the average compressional wave velocity of adjacent formations; β is the average shear wave velocity of adjacent formations; μ is the average shear modulus of adjacent formations; and Δ indicates a change in a given property.

Claim 5

Dependent Claim 20 words

The method of claim 3 wherein the first set of attributes for inferring changes in formation properties further includes: ##EQU6##

Claim 6

Dependent Claim 45 words

The method of claim 3 further including the step of: developing a second set of attributes which provide a measure of the variations in the amplitude of the seismic signal as a function of incident angle and are functions of the first set of attributes.

Claim 7

Dependent Claim 58 words

The method of claim 5 further including the step of: assigning a selected color to each attribute of the first and second set of attributes, the intensity of each color being a function of the magnitude of the selected attribute; and overlaying selected colored attributes of the sets of attributes onto a corresponding seismic section of seismic signals.

Claim 8

Dependent Claim 31 words

The method of claim 5 wherein the second set of attributes includes a measure of change in magnitude of the amplified for each selected seismic event as a function of range.

Claim 9

Dependent Claim 38 words

The method of claim 7 wherein said change in magnitude of the amplitude as a function of range is described by: B.sub.s =sign (B.sub.0)*sign (B.sub.1) where sign indicates the ± sense of B 0 and B 1 .

Claim 10

Dependent Claim 21 words

The method of claim 5 wherein an attribute of the second set of attributes is described by: B.sub.L =arctan (B.sub.1 /B.sub.0).

Claim 11

Dependent Claim 20 words

The method of claim 5 wherein an attribute of the second set of attributes is described by: B.sub.r =B.sub.1 /B.sub.0.

Claim 12

Dependent Claim 24 words

The method of claim 1 wherein the sets of attributes includes a measure of the normal incidence reflection coefficient for each selected seismic event.

Claim 13

Dependent Claim 39 words

The method of claim 11 wherein the measure of the normal incidence reflection coefficient is described by the attribute B 0 where B.sub.0 =ΔZ/2Z, Z is the average compressional impedance, and ΔZ is a change in the compressional impedance.

Claim 14

Dependent Claim 33 words

The method of claim 1 wherein the set of attributes includes a measure of rate of variation of the seismic signal amplitude as a function of incident angle for each selected seismic event.

Claim 15

Dependent Claim 63 words

The method of claim 13 wherein: the rate of variation of the seismic signal amplitude is described by the attribute B 1 : where ##EQU7## α is the average compressional wave velocity of adjacent formations; β is the average shear wave velocity of adjacent formations; μ is the average shear modulus of adjacent formations; and Δ indicates a change in a given property.

Claim 16

Dependent Claim 40 words

The method of claim 1 wherein the sets of attributes includes: a measure of the normal incidence reflection coefficient for each selected seismic event; and a rate of variation of the seismic signal amplitude as a function of incident angle.

Claim 17

Dependent Claim 98 words

The method of claim 1 wherein the step of obtaining a measure of the reflection coefficient includes the steps of: obtaining a measure of the amplitude for the selected seismic event of each offset seismic signal in an incident angle ordered gather of offset seismic signal; and statistically fitting the measure of amplitude of each offset seismic signal according to: R.sub.c (θ)=B.sub.0 +B.sub.1 tan.sup.2 θ+B.sub.2 tan.sup.2 θ sin.sup.2 θ (9) where B 0 , B 1 and B 2 are attributes; and θ is an incident angle for the selected seismic event on each of said seismic signal.

Claim 18

Dependent Claim 14 words

The method of claim 16 wherein the maximum incident angle θ is approximately 35°.

Claim 19

Dependent Claim 33 words

The method of claim 17 wherein the step of obtaining a measure of the reflection coefficient includes the step of statistically fitting the measure of amplitude according to: R.sub.c (θ)=B.sub.0 +B.sub.1 tan.sup.2 θ.

Claim 20

Independent Claim 126 words

A method for aligning and obtaining a measure of seismic signal amplitude of seismic signals as a function of incident angle for selected seismic events comprising the steps of: sorting offset seismic signals into gathers of ordered incident angle; forming a reference seismic signal from the incident angle gather of offset seismic signals; cross-correlating a segment of the reference seismic signal containing the selected seismic event with a segment of the corresponding gather of offset seismic signals, the position of maximum cross-correlation on each offset seismic signal being a primary offset event position; averaging the lobe amplitude of each offset seismic signal within a prescribed time window of the offset primary event position; and forming ordered pairs of averaged lobe amplitudes and corresponding primary offset positions.

Claim 21

Independent Claim 126 words

A method for aligning and obtaining a measure of seismic signal amplitude of seismic signals as a function of incident angle for selected seismic events comprising the steps of: sorting offset seismic signals into gathers of ordered incident angle; forming a reference seismic signal from the incident angle gather of offset seismic signals; cross-correlating a segment of the reference seismic signal containing the selected seismic event with a segment of the corresponding gather of offset seismic signals, the position of maximum cross-correlation on each offset seismic signal being a primary offset event position; averaging the lobe amplitude of each offset seismic signal within a prescribed time window of the offset primary event position; and forming ordered pairs of averaged lobe amplitudes and corresponding primary offset positions.

Claim 22

Dependent Claim 33 words

The method of claim 19 wherein the step averaging further includes: averaging only lobe amplitudes having the same sign as the product of the reference signal lobe amplitude and the cross correlation function.

Claim 23

Dependent Claim 25 words

The method of claim 19 further including: obtaining a measure of the incident angle for the selected seismic event at each offset primary event position.

Claim 24

Independent Claim 120 words

A method of displaying seismic data to quantitatively distinguish seismic events and to infer changes in the geology of the subterranean formations comprising the steps of: obtaining sets of attributes descriptive of variations in seismic signal amplitude as a function of incident angle for selected seismic events in an incident angle ordered gather of seismic signals; and overlaying selected attributes descriptive of amplitude variations for selected seismic events in incident angle ordered gathers of seismic signals from the sets of attributes descriptive of variations in seismic signal amplitude in incident angle ordered gathers of seismic signals on corresponding seismic sections of the seismic data to quantitatively distinguish seismic events and to infer changes in the geology of the subterranean formations.

Claim 25

Independent Claim 120 words

A method of displaying seismic data to quantitatively distinguish seismic events and to infer changes in the geology of the subterranean formations comprising the steps of: obtaining sets of attributes descriptive of variations in seismic signal amplitude as a function of incident angle for selected seismic events in an incident angle ordered gather of seismic signals; and overlaying selected attributes descriptive of amplitude variations for selected seismic events in incident angle ordered gathers of seismic signals from the sets of attributes descriptive of variations in seismic signal amplitude in incident angle ordered gathers of seismic signals on corresponding seismic sections of the seismic data to quantitatively distinguish seismic events and to infer changes in the geology of the subterranean formations.

Claim 26

Dependent Claim 79 words

The method of claim 22 wherein the sets of attributes includes: a first set of attributes B 0 , B 1 and B 2 obtained from a least squares fit of the amplitude variations as a function of incident angle according to R.sub.c (θ)=B.sub.0 +B.sub.1 tan.sup.2 θ+B.sub.2 tan.sup.2 sin.sup.2 θ where R c (θ) is the reflection coefficient of the selected seismic event; and θ is an incident angle for the selected seismic event on an offset seismic signal.

Claim 27

Dependent Claim 28 words

The method of claim 23 wherein the sets of attributes includes: a second set of attributes B F obtained from selected functions of the first set of attributes.

Claim 28

Dependent Claim 37 words

The method of claim 24 wherein the second set of attributes includes: B.sub.s =sign (B.sub.0)*sign (B.sub.1); B.sub.r =B.sub.1 /B.sub.0 ; and B.sub.L =arctangent (B.sub.1 /B.sub.0); where sign indicates ± sets of B 0 and B 1 .

Claim 29

Dependent Claim 19 words

The method of claim 22 further including: assigning a selected color to each attribute in the sets of attributes.

Claim 30

Dependent Claim 26 words

The method of claim 26 further including: varying the intensity of the color assigned to each attribute as a function of the magnitude of each attribute.

Claim 31

Independent Claim 133 words

A method of seismic exploration to quantitatively distinguish seismic events, comprising the steps of: (a) obtaining an incident angle ordered gather of seismic signals; (b) determining a measure of seismic signal amplitude as a function of incident angle for selected seismic events in the incident angle ordered gather of seismic signals at a position of maximum cross-correlation of each seismic signal of the gather with a reference seismic signal, the reference seismic signal being a stack of the incident angle ordered gather of seismic signals; and (c) performing a statistical fit of the measured amplitudes for selected seismic events to a function of incident angle to obtain a first set of attributes descriptive of variations in amplitude as a function of incident angle for the selected seismic events to quantitatively distinguish seismic events.

Claim 32

Independent Claim 133 words

A method of seismic exploration to quantitatively distinguish seismic events, comprising the steps of: (a) obtaining an incident angle ordered gather of seismic signals; (b) determining a measure of seismic signal amplitude as a function of incident angle for selected seismic events in the incident angle ordered gather of seismic signals at a position of maximum cross-correlation of each seismic signal of the gather with a reference seismic signal, the reference seismic signal being a stack of the incident angle ordered gather of seismic signals; and (c) performing a statistical fit of the measured amplitudes for selected seismic events to a function of incident angle to obtain a first set of attributes descriptive of variations in amplitude as a function of incident angle for the selected seismic events to quantitatively distinguish seismic events.

Claim 33

Dependent Claim 35 words

The method of claim 28 wherein step (c) comprises performing a statistical fit of the measured amplitude for the aligned selected seismic events to a measure of reflection coefficient as a function of incident angle.

Claim 34

Dependent Claim 56 words

The method of claim 29 wherein the measure of reflection coefficient as a function of incident angle includes: R.sub.c (θ)=B.sub.0 +B.sub.1 tan.sup.2 θ+B.sub.2 tan.sup.2 θ sin.sup.2 θ where B 0 , B 1 , and B 2 are attributes; and θ is an incident angle for the selected seismic event on each of said seismic signals.

Claim 35

Dependent Claim 100 words

The method of claim 28 wherein step (b) comprises: (a) forming the reference seismic signal by stacking the incident angle gather of offset seismic signals; (b) cross-correlating a segment of the reference seismic signals containing selected seismic events with a segment of the corresponding gather of offset seismic signals, the position of maximum cross-correlation on each offset seismic signal being a primary offset event position; (c) averaging the lobe amplitude of each offset seismic signal within a prescribed time window of the offset primary event position; and (d) forming ordered pairs of averaged lobe amplitudes and corresponding primary offset positions.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1990-02-23	1990-08-25	1991-02-24	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1994-02-23	1994-08-25	1995-02-24	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1998-02-23	1998-08-25	1999-02-24	$7700.00	Window Closed / Lapsed

Method of seismic exploration including processing and displaying seismic data to quantitatively distinguish among seismic events

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