US3597727A — Method of attenuating multiple seismic signals in…

Claim 1

Independent Claim 334 words

In collecting and processing of cross-steered seismic data containing high signal-to-noise ratios for determining the threedimensional stratal configuration of an earth formation, a method for simultaneously improving the primary-to-multiple signal ratios of said seismic data, comprising a. generating a record of seismic signals from seismic discontinuities within said earth formation, including multiply reflected signals, by employing an array of seismic sources and seismic detectors positioned such that center points between all possIble source-detector pairs form a two-dimensional grid of center points along a line of survey, said array of sources and detectors being positioned with respect to said line of survey so as to provide a plurality of source points aligned with one of (i) a spread line substantially parallel to said line of survey and (ii) a series of oblique lines intersecting said line of survey at a common oblique angle, and a plurality of detector stations aligned with the other of said spread line and said series of oblique lines, said recorded signals being the output of said seismic detectors, b. by means of automated data processing means, statically and dynamically correcting said recorded signals with said twodimensional grid of center points so as to produce a series of corrected traces, said series of corrected traces containing cross sets of traces associated with crosslines of center points of said center point grid substantially perpendicular to said line of survey, at least one trace of each cross set of traces being a product of a respective source-detector pair having a substantially different horizontal spacing than at least one other source-detector pair of other traces associated with said each cross set of traces, and c. by means of automated data processing means, beam steering each cross set of traces to produce a subset of crossdirectional traces having improved signal-to-noise ratios for use in determining the three-dimensional stratal configuration of said earth formation, said multiply reflected signals in each of said cross set of traces also being significantly attenuated as said traces are beam steered.

Claim 2

Dependent Claim 334 words

In collecting and processing of cross-steered seismic data containing high signal-to-noise ratios for determining the threedimensional stratal configuration of an earth formation, a method for simultaneously improving the primary-to-multiple signal ratios of said seismic data, comprising a. generating a record of seismic signals from seismic discontinuities within said earth formation, including multiply reflected signals, by employing an array of seismic sources and seismic detectors positioned such that center points between all possIble source-detector pairs form a two-dimensional grid of center points along a line of survey, said array of sources and detectors being positioned with respect to said line of survey so as to provide a plurality of source points aligned with one of (i) a spread line substantially parallel to said line of survey and (ii) a series of oblique lines intersecting said line of survey at a common oblique angle, and a plurality of detector stations aligned with the other of said spread line and said series of oblique lines, said recorded signals being the output of said seismic detectors, b. by means of automated data processing means, statically and dynamically correcting said recorded signals with said twodimensional grid of center points so as to produce a series of corrected traces, said series of corrected traces containing cross sets of traces associated with crosslines of center points of said center point grid substantially perpendicular to said line of survey, at least one trace of each cross set of traces being a product of a respective source-detector pair having a substantially different horizontal spacing than at least one other source-detector pair of other traces associated with said each cross set of traces, and c. by means of automated data processing means, beam steering each cross set of traces to produce a subset of crossdirectional traces having improved signal-to-noise ratios for use in determining the three-dimensional stratal configuration of said earth formation, said multiply reflected signals in each of said cross set of traces also being significantly attenuated as said traces are beam steered.

Claim 3

Dependent Claim 57 words

The method of claim 1 in which each of said cross lines of center points associated with a respective cross set of traces has a maximum total cross offset length of sufficient magnitude to permit processing of said sets of cross traces by beam steering so as to produce statistically related subsets of cross steered, cross-directional traces.

Claim 4

Dependent Claim 26 words

The method of claim 2 in which said maximum total cross offset length of each of said crosslines of center points is less than 3,000 feet.

Claim 5

Dependent Claim 26 words

The method of claim 2 in which said maximum total cross offset length of each of said crosslines of center points is less than 300 feet.

Claim 6

Dependent Claim 39 words

The method of claim 2 in which said array of source and detectors are arranged so that said grid of center points between all possible source-detector pairs forms a grid of equispaced center points of uniform center point density.

Claim 7

Dependent Claim 41 words

The method of claim 1 wherein said plurality of seismic source points are aligned with said series of oblique lines intersecting said line of survey, and said detector stations are positioned on said spread line coincident with said line of survey.

Claim 8

Dependent Claim 269 words

The method of claim 1 in which said first-mentioned step includes the substeps of: a. positioning a plurality of detectors along said spread line coincident with said line of survey and a seismic source positioned at a first source point having a predetermined cross offset with respect to said line of survey whereby center points between all detector-source pairs produce a line of center points parallel to said line of survey, said detectors having a substantially constant station-to-station spacing between 50-500 feet, b. exciting said source to produce a seismic disturbance, c. recording the output signals of each detector following excitation, d. positioning along a first oblique line intersecting said last-used source point another seismic source at another source point more advanced in the in-line direction of survey than the last-used source point, and advancing said plurality of detectors along said line of survey a distance equal to the in-line spacing between the last-used source point and said another source point, said another source point having an offset distance with respect to said line of survey different than that of the last-used source point so as to produce another line of cEnter points between all detector-source pairs substantially parallel to the line of survey, offset from said first-produced line of center points, but having a substantial number of center points in cross alignment with said center cross points of said first-produced line, so as to define cross lines of center points substantially perpendicular to said line of survey, e. exciting said another source to produce seismic disturbance, f. recording the output signals of each detector following the last-mentioned excitation.

Claim 9

Dependent Claim 100 words

The method of claim 7 with the additional step of repeating, in sequence, substeps (d), (e) and (f) until the last-used source point along said first oblique line is at a maximum cross offset from said line of survey, so as to produce additional center points in alignment with said crosslines of center points substantially perpendicular to said line of survey, at least one center point in each crossline of center points being positioned between a source-detector pair whose horizontal spacing is substantially different than that of at least one other source-detector pair of the same crossline of center points.

Claim 10

Dependent Claim 159 words

The method in accordance with claim 8 with the additional steps of: g. positioning, on another oblique line intersecting said line of survey at an intersection angle equal to that of said first oblique angle, yet another seismic source at yet another source point more advanced in the in-line direction by said in-line spacing of said plurality of detectors than said last-used source point, and advancing said plurality of detectors along said line of survey a distance equal to the in-line spacing between the last-used source point and said yet another source point, said yet another source point having an offset distance with respect to said line of survey less than that of the last-used source point, as to produce another line of center points between all detector-source pairs substantially parallel to the line of survey, h. exciting said yet another source to produce a seismic disturbance, i. recording the output signals of each detector following the last-mentioned excitation.

Claim 11

Dependent Claim 72 words

The method of claim 9 with the additional step of repeating, in sequence, steps (g), (h) and (i) until the last-used source point along said another oblique line is at a maximum cross offset with respect to said line of survey, the magnitude of said offset being about equal to that of the last-used source point associated with said first oblique line, as to define a continuous two-dimensional grid of center points.

Claim 12

Dependent Claim 145 words

The method of claim 1 in which said first-mentioned step includes the substeps of locating said detector stations on said line of survey and locating said plurality of source points on said series of oblique lines intersecting said line of survey, such that said oblique lines of source points define common slopes and common angles of intersection with said line of survey, said detection stations have a common, constant in-line spacing, each line of source points also having a constant, common oblique spacing interval between adjacent source points and including at least first and second terminal source points spaced apart on opposite sides of said line of survey, said first and second terminal source points having substantially equal offset spacings with respect to the line of survey whereby the grid of center points between all possible source-detector pairs is centered at the line of survey.

Claim 13

Dependent Claim 95 words

The method of claim 11 in which the plurality of source points is located such that the common, constant oblique spacing interval between source points defines a common oblique spacing interval between adjacent source points, the cross offset component of which being equal to (i) about the magnitude of the spacing interval between adjacent detector stations, and (ii) about one-half its in-line component parallel to the line of survey, whereby the grid of center points between all possible source-Detector pairs is equispaced in both cross and in-line directions and of substantial uniform center point density.

Claim 14

Dependent Claim 101 words

The method of claim 1 in which said first-mentioned step includes locating said source points on said series of oblique lines intersecting said line of survey and locating said detector stations on said spread line coincident with said line of survey, source points along any one oblique line forming a set of source points having a constant source point interval in the oblique direction and including terminal first and second source points located on the same side of said line of survey, said series of oblique lines having common slopes and common oblique angles of intersection with said line of survey.

Claim 15

Dependent Claim 103 words

The method of claim 13 in which the plurality of source points is located such that the slopes of said series of oblique lines are similar and the common, constant spacing interval between source points along any one oblique line of source points of similar slope defines a common oblique spacing interval, the cross component of which being equal to (i) about the magnitude of the spacing interval between adjacent detector stations, and (ii) about one-half its in-line component parallel to the line of survey, whereby the grid of center points between all possible source-detector pairs is of substantial uniform center point density.

Claim 16

Dependent Claim 217 words

The method of claim 13 in which the plurality of source points is located along oblique lines intersecting said line of survey such as to define (i) a first set of source points located along one of a first series of divergent oblique lines having a positive slope and a second series of divergent oblique lines having a negative slope measured from said line of survey in the direction of the survey, and (ii) a second set of source points located along the other of said first and second series of positively and negatively sloped oblique lines, said first and second sets of source points having similar and constant spacing intervals in directions along said oblique lines, and each set of source points including terminal first and second source points located on the same side of said line of survey, the first and second series of divergent lines each being defined by common oblique angles at respective points of intersection with said line of survey and including spacing intervals at their points of intersection of constant and equal values whereby any one interval between adjacent lines of one of said first and second series of lines being bisected by the point of intersection of one line on the other of said first and second series of lines.

Claim 17

Dependent Claim 88 words

The method in accordance with claim 15 in which the plurality of source points are located such that the common, constant spacing interval between source points along any one oblique line defines a common oblique spacing interval, the cross component of which being equal to (i) about the magntidue of the spacing interval between adjacent detector stations, and (ii) about one-half its in-line component parallel to the line of survey, whereby the grid of center points between all possible source-detector pairs is of substantial uniform center point density.

Claim 18

Dependent Claim 92 words

The method in accordance with claim 1 in which the first-mentioned step includes the step of positioning said array of seismic sources and seismic detectors such that the incremental horizontal spacing factor, Dmax-Dmin is between 1,000 feet up to and including 8,000 feet where Dmax is the maximum horizontal spacing between a source-detector pair associated with center points aligned in the same line perpendicular to the line of survey and Dmin is the minimum horizontal spacing between another source-detector pair in the same center point line as said first-mentioned one source-detector pair.

Claim 19

Dependent Claim 67 words

The method in accordance with claim 1 in which said step of beam steering each cross set of traces includes the additional step of: d. by means of automated data processing means, arranging said subsets of cross directional traces such that each subset comprises at least two directional traces with a common cross compositional moveout and different in-line positions, the different subsets having different cross compositional moveouts.

Claim 20

Dependent Claim 82 words

The method of claim 18 with the additional steps performed by means of automated data processing means consisting of: e. determining the cross moveout of at least one seismic event in a subset of cross directional traces by identifying which directional traces evidence said one seismic event most prominently, and f. determining the in-line moveout of the same one seismic event by the disparity in arrival time of said event on at least two directional traces having the same cross compositional moveout.

Claim 21

Dependent Claim 256 words

In systematically collecting seismic data along a line of survey for use in determining the three-dimensional configuration of an earth formation by interpretation of enhanced, beam-steered records of seismic signals, including multiply reflected signals, received from discontinuities within said formation, said records being locationally associated with at least two center points aligned along a series of lines perpendicular to said line of survey, an apparatus comprising: an array of seismic source and seismic detectors positioned about said line of survey so as to define a series of source points positioned along one of (i) a spread line parallel to said line of survey and (ii) a series of oblique lines intersecting said survey line, and a plurality of detector stations aligned with the other of said spread line and said series of oblique lines, said array being arranged such that the center points between all pairs of source point-detector stations define a two-dimensional grid including sets of center points aligned along a series of lines substantially perpendicular to the line of survey, said source points and detector stations having in-line and offset spacings relative to said line of survey arranged such that at least one center point of each set of cross center points is formed between a source-detector pair having a substantially different horizontal spacing than that of at least on other source-detector pair of the same set of cross center points so that subsequently derived beam-steered traces associated with each set of cross center points of said grid contain significantly attenuated multiply reflected signals.

Claim 22

Dependent Claim 256 words

In systematically collecting seismic data along a line of survey for use in determining the three-dimensional configuration of an earth formation by interpretation of enhanced, beam-steered records of seismic signals, including multiply reflected signals, received from discontinuities within said formation, said records being locationally associated with at least two center points aligned along a series of lines perpendicular to said line of survey, an apparatus comprising: an array of seismic source and seismic detectors positioned about said line of survey so as to define a series of source points positioned along one of (i) a spread line parallel to said line of survey and (ii) a series of oblique lines intersecting said survey line, and a plurality of detector stations aligned with the other of said spread line and said series of oblique lines, said array being arranged such that the center points between all pairs of source point-detector stations define a two-dimensional grid including sets of center points aligned along a series of lines substantially perpendicular to the line of survey, said source points and detector stations having in-line and offset spacings relative to said line of survey arranged such that at least one center point of each set of cross center points is formed between a source-detector pair having a substantially different horizontal spacing than that of at least on other source-detector pair of the same set of cross center points so that subsequently derived beam-steered traces associated with each set of cross center points of said grid contain significantly attenuated multiply reflected signals.

Claim 23

Dependent Claim 137 words

The apparatus in accordance with claim 20 in which said source points are located along said series of oblique lines and have constant, common spacing intervals between adjacent source points, and said detector stations are located along said spread line coincident with said line of survey such that intervals between adjacent detector stations are equalized, said oblique lines having common slopes and common angles of intersection at their points of intersection with said line of survey; each oblique line of source points including at least first and second terminal source points positioned on opposite sides of said line of survey, each terminal source point being of substantially the same cross offset as the other terminal source point whereby the grid of center points between all possible source point-detector station pairs are centered at said line of survey.

Claim 24

Dependent Claim 117 words

The apparatus of claim 20 in which said source points are located along a series of oblique lines, with intervals between adjacent source points being equalized, and said detector stations are located along said spread line coincident with said line of survey, with spacing intervals between adjacent detector stations also being equalized, said oblique lines having common slopes and forming common oblique angles of intersection at their points of intersection with said line of survey, each oblique line of source points including at least first and second terminal source points located on the same side of said line of survey whereby center poiNts between all possible source point-detector station pairs are offset from said line of survey.

Claim 25

Dependent Claim 218 words

The apparatus of claim 20 in which said series of source points are located along said series of oblique lines intersecting said line of survey and includes (i) a first set of source points located along one of a first series of divergent oblique lines having common positive slopes and a second series of divergent oblique lines having a negative slope measured from said line of survey in the direction of the survey, and (ii) a second set of source points located along the other of said first and second series of positively and negatively sloped oblique lines, said first and second sets of source points having similar and constant spacing intervals in directions along said oblique lines, and each set of source points including terminal first and second source points located on the same side of said line of survey, the first and second series of divergent lines each being defined by common oblique angles at respective points of intersection with said line of survey and including spacing intervals at their points of intersection of constant and equal values whereby any one interval between adjacent lines of one of said first and second series of lines is bisected by the point of intersection of one line on the other of said first and second series of lines.

Claim 26

Dependent Claim 68 words

The apparatus in accordance with claim 20 in which the incremental horizontal spacing factor Dmax-Dmin is between 1,000 feet up to and including 8,000 feet where Dmax is the maximum horizontal spacing between a source-detector pair in a particular cross set of center points perpendicular to the line of survey, and Dmin is the minimum spacing of another source-detector pair in the same cross set of center points.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1974-08-02	1975-02-01	1975-08-03	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1978-08-02	1979-02-01	1979-08-03	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1982-08-02	1983-02-01	1983-08-03	$7700.00	Window Closed / Lapsed

Method of attenuating multiple seismic signals in the determination of inline and cross dips employing cross-steered seismic data

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