Patent EP0135623A2 successfully refreshed from Google Patents.
EP0135623A2
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EP
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Seismic method for identifying low velocity subsurface zones
Assignee: Cook Ernest Ewart
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Filing: 1983-08-30
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Granted: —
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Expires: 2003-08-30
Abstract
Abstract This invention consists of producing a two-dimensional display from exploration seismic data designed to indicate zones of anomalous low velocity in the subsurface. Such zones may be indicative of porosity and the possible occurrence of hydrocarbons. They will be localized in terms of position along the seismic profile and in approximate zone of reflection arrival time. Date used in making the display are derived from both the CDP stacked seismic profile and corresponding velocity analyses used also to stack the data itself. Stacking velocity curves are plotted according to CDP location for each reflector designated by an interpreter to be of interest. These curves are overlain in pairs using calibration calculations and empirical criteria. Calibration helps smooth "noisy" values and compensates for velocity variations resulting from changes in separation or dip of the two reflectors from which the overlain velocity curves derive. In addition, it is presumed that the inverval bracketed by each reflector pair taken in turn has uniform or only regional lateral variations of interval velocity - no local lateral variation is assumed. "Cross overs" or convergences of the paired curves thus indicate zones of either high or low interval velocity of local nature. The display itself consists of the velocity curves for all possible reflector pairs and vertical bands of color which are assigned to identify the reflection interval of particular low velocity zones which are shown consistently by all reflectors taken in pairs which bracket such zones. Horizontal position is of course indicated by the CDP location.
Inventors
- 👤 Norman Samson Neidell
- 👤 Ernest Ewart Cook
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 03:11
CPC Classifications
G; G01; G01V; G01V1/00; G01V1/28; G01V1/30; G01V1/303
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
81 words
A seismic method for identifying the presence of subsurface low velocity zones comprising: a) plotting velocity curves for a plurality of seismic reflections according to common depth point location; b) overlaying each of said velocity curves in a best fit manner with all other velocity curves in turn; and c) identifying zones of consistent low velocity disparity of deeper velocity curves with shallower velocity curves bracketing a common zone, said zones suggesting the presence of low velocity in the subsurface formation.
Claim 2
Dependent Claim
81 words
A seismic method for identifying the presence of subsurface low velocity zones comprising: a) plotting velocity curves for a plurality of seismic reflections according to common depth point location; b) overlaying each of said velocity curves in a best fit manner with all other velocity curves in turn; and c) identifying zones of consistent low velocity disparity of deeper velocity curves with shallower velocity curves bracketing a common zone, said zones suggesting the presence of low velocity in the subsurface formation.
Claim 3
Dependent Claim
16 words
A seismic method as recited in Claim 1, wherein said velocity curves are stacking velocity curves.
Claim 4
Dependent Claim
28 words
A method as recited in Claim 1 wherein said best fit manner consists of calibrating the overlain curves when the curves are within 250 msec. of one another.
Claim 5
Dependent Claim
167 words
A seismic method for identifying the presence of low velocity subsurface zones comprising: a) picking a velocity for each recorded reflection event time and for each velocity analysis; b) separately plotting the velocities for each reflection event according to said analysis location, the velocity plots thus obtained representing velocity trends as picked for each reflector of interest; c) overlaying each of the individual velocity plots in pairs in a best fit manner with all other velocity plots taken in turn to bracket zones between reflections; d) conducting a semi-empirical alignment to compensate for possible development of discordant dip between the particular reflector pair; e) identifying low velocity disparity zones for a predicted velocity curve for a deeper reflector and the actual velocity curve for said reflector; f) developing a final graphical display with all curve combination pairs presented in order of depth; and g) visually emphasizing places along the profile where velocity curves of deeper reflectors are in low velocity disparity with velocity curves from shallower reflectors.
Claim 6
Dependent Claim
167 words
A seismic method for identifying the presence of low velocity subsurface zones comprising: a) picking a velocity for each recorded reflection event time and for each velocity analysis; b) separately plotting the velocities for each reflection event according to said analysis location, the velocity plots thus obtained representing velocity trends as picked for each reflector of interest; c) overlaying each of the individual velocity plots in pairs in a best fit manner with all other velocity plots taken in turn to bracket zones between reflections; d) conducting a semi-empirical alignment to compensate for possible development of discordant dip between the particular reflector pair; e) identifying low velocity disparity zones for a predicted velocity curve for a deeper reflector and the actual velocity curve for said reflector; f) developing a final graphical display with all curve combination pairs presented in order of depth; and g) visually emphasizing places along the profile where velocity curves of deeper reflectors are in low velocity disparity with velocity curves from shallower reflectors.
Claim 7
Dependent Claim
55 words
A method as recited in Claim 4, wherein said velocity curves are stacking velocity curves and said overlaying said velocity pairs comprises: a) plotting stacking velocity curves for each of the reflections of interest on a stacked seismic section; and b) overlaying the stacking velocity curves with other stacking velocity curves in order of depth.
Claim 8
Dependent Claim
11 words
A method as recited in Claim 4 wherein said interpreting comprises;
Claim 9
Dependent Claim
47 words
a) coloring areas defined by consistent velocity curve disparity for prediction of an intervening anomalous low velocity occurrence; b) preparing an aperture calculation; and c) plotting the aperture calculation in graphical form on the interpretive display for reference in confirming the predicted intervening anomalous low velocity occurrence.
Claim 10
Dependent Claim
47 words
a) coloring areas defined by consistent velocity curve disparity for prediction of an intervening anomalous low velocity occurrence; b) preparing an aperture calculation; and c) plotting the aperture calculation in graphical form on the interpretive display for reference in confirming the predicted intervening anomalous low velocity occurrence.
Claim 11
Dependent Claim
34 words
A method as recited in Claim 6, including: a) confirming low velocity zones by their vertical alignment on said display; and b) installing vertical lines on said display to bracket said low velocity zones.
Claim 12
Dependent Claim
51 words
A seismic method of identifying low velocity zones in the subsurface comprising: a) estimating seismic velocities from pairs of overlying reflectors, each said pair bracketing a possible low velocity zone; and b) interpreting consistent low velocity indications for a common zone as suggesting low velocity for said zone in the subsurface.
Claim 13
Dependent Claim
51 words
A seismic method of identifying low velocity zones in the subsurface comprising: a) estimating seismic velocities from pairs of overlying reflectors, each said pair bracketing a possible low velocity zone; and b) interpreting consistent low velocity indications for a common zone as suggesting low velocity for said zone in the subsurface.
Claim 14
Dependent Claim
16 words
A seismic method for identifying low velocity subsurface zones which may be of reservoir quality, comprising;
Claim 15
Dependent Claim
16 words
A seismic method for identifying low velocity subsurface zones which may be of reservoir quality, comprising;
Claim 16
Dependent Claim
229 words
a) marking reflections of interest on a stacked seismic profile; b) timing the reflections of interest by common depth point basis and listing them; c) plotting the times listed on the velocity analyses; d) selecting stacking velocities that correspond to selected reflections, said stacking velocities being along the plotted times on the stacking velocity analyses; e) obtaining stacking velocities on a shot point by shot point basis; f) tracking seismic reflections of interest according to stacking velocity on an analysis-by-analysis basis using the times from said reflections from said seismic profile; g) plotting selected velocity curves for each selected reflection; h) overlaying in best fit manner each of the selected velocity. curves with each of the other velocity curves taken in turn for each selected reflection; i) conducting a semi-empirical alignment to compensate for possible development of discordance dip between the particular reflector pairs; j) arranging overlain pairs of velocity curves in order of depth, the overlain pairs of velocity curves defining low velocity disparity zones; k) preparing an aperture equation giving an aperture length for each reflector pair; 1) plotting the resulting aperture on the display of overlain pairs for reference in confirming the reality of possible low velocity zones, m) coloring low velocity disparity zones to enhance the visual identity thereof; and n) placing vertical lines on said display to bracket zones of consistent low velocity disparity...
Claim 17
Dependent Claim
229 words
a) marking reflections of interest on a stacked seismic profile; b) timing the reflections of interest by common depth point basis and listing them; c) plotting the times listed on the velocity analyses; d) selecting stacking velocities that correspond to selected reflections, said stacking velocities being along the plotted times on the stacking velocity analyses; e) obtaining stacking velocities on a shot point by shot point basis; f) tracking seismic reflections of interest according to stacking velocity on an analysis-by-analysis basis using the times from said reflections from said seismic profile; g) plotting selected velocity curves for each selected reflection; h) overlaying in best fit manner each of the selected velocity. curves with each of the other velocity curves taken in turn for each selected reflection; i) conducting a semi-empirical alignment to compensate for possible development of discordance dip between the particular reflector pairs; j) arranging overlain pairs of velocity curves in order of depth, the overlain pairs of velocity curves defining low velocity disparity zones; k) preparing an aperture equation giving an aperture length for each reflector pair; 1) plotting the resulting aperture on the display of overlain pairs for reference in confirming the reality of possible low velocity zones, m) coloring low velocity disparity zones to enhance the visual identity thereof; and n) placing vertical lines on said display to bracket zones of consistent low velocity disparity...
Claim 18
Dependent Claim
28 words
A method as recited in Claim 9 wherein said best fit manner consists of calibrating the overlain curves when the curves are within 250 msec. of one another.
Claim 19
Dependent Claim
11 words
Apparatus for identifying the presence of subsurface low velocity zones comprising
Claim 20
Dependent Claim
11 words
Apparatus for identifying the presence of subsurface low velocity zones comprising
Claim 21
Dependent Claim
87 words
a) means responsive to a plurality of seismic reflection to display a plot of velocity curves according to common depth point location, b) means for displacing such displayed velocity curves to overlay said curves in a best fit manner with the other velocity curves in turn, and c) means responsive to said overlaid curves to identify zones of consistent low velocity disparity of deeper velocity curves with shallower velocity curves bracketing a common zone which identified zones suggest the presence of low velocity in the subsurface formation."
Claim 22
Dependent Claim
87 words
a) means responsive to a plurality of seismic reflection to display a plot of velocity curves according to common depth point location, b) means for displacing such displayed velocity curves to overlay said curves in a best fit manner with the other velocity curves in turn, and c) means responsive to said overlaid curves to identify zones of consistent low velocity disparity of deeper velocity curves with shallower velocity curves bracketing a common zone which identified zones suggest the presence of low velocity in the subsurface formation."
References Cited (Backward Citations)
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