US 5,774,417 A · Amplitude and phase compensation in dual-sensor ocean bottom cable seismic data processing

Abstract

A method and computer system for applying corrections to dual sensor ocean bottom cable marine seismic signals, for purposes of eliminating ghosts and reverberations, are disclosed. According to the disclosed method and system, both phase and amplitude corrections are derived in common receiver gathers, and applied to each geophone trace in the gather; preferably, the derivation of the corrections is performed on a limited offset common receiver gather. The phase correction is determined by minimizing a folded cross-correlation of the hydrophone and geophone signals over varying phase angles, with the appropriate phase correction corresponding to the angle at which the minimum is obtained; preferably, stacked cross-correlations are used in the phase correction determination to reduce the effects of random noise. The phase correction is then applied to the geophone traces in the gather, and an amplitude correction is derived by minimizing a cross-ghosting relationship. Preferably, the cross-ghosting minimization is based upon stacked cross-correlations of the geophone and hydrophone signals and a stacked hydrophone autocorrelation, to eliminate the effects of coherent noise on the geophone trace and the effects of random noise on both the geophone and hydrophone traces. The amplitude correction is then applied to each of the geophone traces in the gather, and the summation scalar is then derived and used to sum the geophone and hydrophone traces for each source-receiver path. The summation scalar may be selected to compensate not only for ghosts, but also for receiver-side reverberations. The summation scalar may also be derived using an estimate for the seafloor reflectivity that takes into account source-side reverberations.

Claims23

Dependent claims

A method of filtering the effects of ghost reflections from dual sensor marine seismic survey signals, comprising the steps of:

retrieving signals corresponding to a plurality of pairs of pressure and velocity traces measured at a first receiver location in the survey, wherein the pressure and velocity traces in each pair each include a modulated signal corresponding to energy imparted from a common source location in the survey and reflected from a subsurface reflecting interface;
from the plurality of pairs of pressure and velocity traces, estimating a relative phase angle between the modulated signals of the pressure and velocity traces;
phase-modifying the pressure and velocity traces in each pair, relative to one another, with a phase shift corresponding to the estimated relative phase angle;
from the plurality of pairs of pressure and velocity traces, estimating a relative sensitivity between the modulated signals of the pressure and velocity traces;
amplitude-modifying the pressure and velocity traces in each pair, relative to one another, with an amplitude scalar corresponding to the estimated relative sensitivity;
and
after the phase-modifying and amplitude-modifying steps, performing a weighted summing of the pressure and velocity traces in each pair, using a summation scalar as a weighting factor, to generate a plurality of summed traces.

4 more elements

A computer system for filtering the effects of ghost reflections from seismic survey signals corresponding to acoustic energy generated by a marine source and detected at a plurality of receiver locations, such detected energy including acoustic energy reflected from subsurface geological structures and ghost reflections from the water surface, wherein each of the receiver locations comprise a geophone for measuring velocity signals and a hydrophone for measuring pressure signals, comprising:

a computer memory for storing seismic trace data corresponding to pairs of velocity and pressure signals, each pair associated with a common source-receiver path;
an output device, for displaying a seismic survey based upon the stored summed traces corresponding to each of the receiver locations;
and
a system computer, coupled to the computer memory and to the output device, programmed to perform, for each of the plurality of receiver locations, the steps of:
retrieving, from the computer memory, digital data corresponding to a plurality of pairs of pressure and velocity traces measured at the receiver location, wherein the pressure and velocity traces in each pair each include a modulated signal corresponding to energy imparted from a common source location in the survey and reflected from a subsurface reflecting interface;
from the plurality of pairs of pressure and velocity traces, estimating a relative phase angle between the modulated signals of the pressure and velocity traces;
phase-modifying the pressure and velocity traces in each pair, relative to one another, with a phase shift corresponding to the estimated relative phase angle;
from the plurality of pairs of pressure and velocity traces, estimating a relative sensitivity between the modulated signals of the pressure and velocity traces;
amplitude-modifying the pressure and velocity traces in each pair, relative to one another, with an amplitude scalar corresponding to the estimated relative sensitivity;
and
after the phase-modifying and amplitude-modifying steps, performing a weighted summing of the pressure and velocity traces in each pair, using a summation scalar as a weighting factor, to generate a plurality of summed traces;
and
storing the summed traces in the computer memory.

10 more elements

A computer-readable memory configured so that, when read and used by a computer, the computer is directed to filter the effects of ghost reflections from seismic survey signals corresponding to acoustic energy generated by a marine source and detected at a plurality of receiver locations, such detected energy including acoustic energy reflected from subsurface geological structures and ghost reflections from the water surface, wherein each of the receiver locations comprise a geophone for measuring velocity signals and a hydrophone for measuring pressure signals, said computer directed by a plurality of operations comprising:

retrieving, from computer memory, digital data corresponding to a plurality of pairs of pressure and velocity traces measured at one of the receiver locations, wherein the pressure and velocity traces in each pair each include a modulated signal corresponding to energy imparted from a common source location in the survey and reflected from a subsurface geological structure;
from the plurality of pairs of pressure and velocity traces, estimating a relative phase angle between the modulated signals of the pressure and velocity traces;
phase-modifying the pressure and velocity traces in each pair, relative to one another, with a phase shift corresponding to the estimated relative phase angle;
from the plurality of pairs of pressure and velocity traces, estimating a relative sensitivity between the modulated signals of the pressure and velocity traces;
amplitude-modifying the pressure and velocity traces in each pair, relative to one another, with an amplitude scalar corresponding to the estimated relative sensitivity;
after the phase-modifying and amplitude-modifying steps, performing a weighted summing of the pressure and velocity traces in each pair, using a summation scalar as a weighting factor, to generate a plurality of summed traces;
and
storing the summed traces in the computer memory.

5 more elements

Dependencies are inferred from the claim text.

Amplitude and phase compensation in dual-sensor ocean bottom cable seismic data processing

Life of this patent

Amplitude and phase compensation in dual-sensor ocean bottom cable seismic data processing

Life of this patent

Abstract

Claims23