Static corrections for seismic traces by cross-correlation method

Claim 1

A method for determining the best values of static correction to be applied to each amplitude versus time trace of a multitrace seismic record representing the output amplitudes of spatially adjacent geophone locations, by determining the individual source-to-datum-plane and geophone-to-datum-plane corrections for each source and each geophone employed in a seismic survey, said method using intertrace cross-correlation time-lag measurements between a plurality of pairs of traces of said record, and taking account of the possibility that measured intertrace crosscorrelation time-lag values between the correlated traces may be composed not only of source-to-datum-plane and geophone-to-datumplane time components, but also, simultaneously, of time components due to subsurface structural reflection time variations between said correlated pairs of traces and time components due to residual normal moveout variations between said correlated pairs of traces, comprising the steps of: a. constraining said variations of the unknown structural reflection time components, and the unknown residual normal moveout time components by defining their individual unknown values respectively in terms of fewer reference unknown values, b. constraining the variation of at least some of said sourceto-datum correction time components and some of said geophoneto-datum correction time components by the introduction of preliminary, field measured, and field estimated, source-todatum-plane time values and geophone-to-datum-plane time values, both of said time values including error quantities to be minimized, c. generating a redundant set of simultaneous linear equations, corresponding to a redundant set of said cross-correlation time-lag measurements, whose unknowns are (i) said source-todatum corrections, (ii) said geophone-to-datum corrections, (iii) said reference unknown structural reflection time components, and (iv) said reference unknown residual normal moveout time components, d. then solving said redundant set of linear equations for source-to-datum and geophone-to-datum corrections to be applied as said determined static corrections to each of said traces of said record, by minimizing the sum of the squares of the individual amounts by which the individual equations of said redundant set are not satisfied by their common solution.

Claim 2

A method for determining the best values of static correction to be applied to each amplitude versus time trace of a multitrace seismic record representing the output amplitudes of spatially adjacent geophone locations, by determining the individual source-to-datum-plane and geophone-to-datum-plane corrections for each source and each geophone employed in a seismic survey, said method using intertrace cross-correlation time-lag measurements between a plurality of pairs of traces of said record, and taking account of the possibility that measured intertrace crosscorrelation time-lag values between the correlated traces may be composed not only of source-to-datum-plane and geophone-to-datumplane time components, but also, simultaneously, of time components due to subsurface structural reflection time variations between said correlated pairs of traces and time components due to residual normal moveout variations between said correlated pairs of traces, comprising the steps of: a. constraining said variations of the unknown structural reflection time components, and the unknown residual normal moveout time components by defining their individual unknown values respectively in terms of fewer reference unknown values, b. constraining the variation of at least some of said sourceto-datum correction time components and some of said geophoneto-datum correction time components by the introduction of preliminary, field measured, and field estimated, source-todatum-plane time values and geophone-to-datum-plane time values, both of said time values including error quantities to be minimized, c. generating a redundant set of simultaneous linear equations, corresponding to a redundant set of said cross-correlation time-lag measurements, whose unknowns are (i) said source-todatum corrections, (ii) said geophone-to-datum corrections, (iii) said reference unknown structural reflection time components, and (iv) said reference unknown residual normal moveout time components, d. then solving said redundant set of linear equations for source-to-datum and geophone-to-datum corrections to be applied as said determined static corrections to each of said traces of said record, by minimizing the sum of the squares of the individual amounts by which the individual equations of said redundant set are not satisfied by their common solution.

Claim 8

A method for determining the static correction to be applied to each trace of a multitrace seismic record by determining the individual source-to-datum-plane and geophone-to-datum-plane corrections for each particular source and each particular geophone employed to produce said trace in said multitrace seismic record, said method using a multiplicity of intertrace cross-correlation time-lag measurements between selected pairs of traces in said record, and taking account of the possibility that measured intertrace cross-correlation time-lag values may be composed not only of source-to-datum-plane and geophone-to-datum-plane time components, but also, simultaneously, of time components due to subsurface structural reflection time variations between traces and time components due to residual normal moveout variations between traces, comprising the steps of: a. generating from said measured cross-correlation time-lag values, derived from pairs of cross-correlated traces, a redundant set of simultaneous linear equations including error quantities to be minimized, said set comprising one equation for each cross-correlation time-lag value and each equation containing a different set of said source-to-datum-plane time components, said geophone-to-datum-plane time components, said structural reflection time components and said residual normal moveout time components, b. then solving said redundant set of simultaneous linear equations, minimizing said error quantities by the least-squares-error method, for the individual source-to-datum-plane and geophone-to-datum-plane time components to be applied for the particular source and particular geophone employed in producing each of said cross-correlated traces, c. and shifting each trace on said record in accordance with its found particular source-to-datum-plane and geophone-to-datum-plane time components constituting said static correction for that trace.

Claim 9

A method for determining the static correction to be applied to each trace of a multitrace seismic record by determining the individual source-to-datum-plane and geophone-to-datum-plane corrections for each particular source and each particular geophone employed to produce said trace in said multitrace seismic record, said method using a multiplicity of intertrace cross-correlation time-lag measurements between selected pairs of traces in said record, and taking account of the possibility that measured intertrace cross-correlation time-lag values may be composed not only of source-to-datum-plane and geophone-to-datum-plane time components, but also, simultaneously, of time components due to subsurface structural reflection time variations between traces and time components due to residual normal moveout variations between traces, comprising the steps of: a. generating from said measured cross-correlation time-lag values, derived from pairs of cross-correlated traces, a redundant set of simultaneous linear equations including error quantities to be minimized, said set comprising one equation for each cross-correlation time-lag value and each equation containing a different set of said source-to-datum-plane time components, said geophone-to-datum-plane time components, said structural reflection time components and said residual normal moveout time components, b. then solving said redundant set of simultaneous linear equations, minimizing said error quantities by the least-squares-error method, for the individual source-to-datum-plane and geophone-to-datum-plane time components to be applied for the particular source and particular geophone employed in producing each of said cross-correlated traces, c. and shifting each trace on said record in accordance with its found particular source-to-datum-plane and geophone-to-datum-plane time components constituting said static correction for that trace.