Western Atlas International, Inc.

Fairfield Industries, Inc.

Baker Hughes Corporation

Magseis Ff LLC

Josef Paffenholz

Frederick J Barr

Ronald E Chambers

Kenneth Craft

Kenneth L Craft

Gary Arthur Sitton

James E Gaiser

Systems and methods of performing a seismic survey are described. The system can receive seismic data in a first domain, and transform the seismic data into a tau-p domain. The system can identify a value on an envelope in the tau-p domain, select several values on the tau-p envelope using a threshold, and then generate a masking function. The system can combine the masking function with the tau-p transformed seismic data, and then perform an inverse tau-p transform on the combined seismic data. The system can adjust amplitudes in the inverse tau-p transformed combined seismic data, and identify one or more coherent events corresponding to subsea lithologic formations or hydrocarbon deposits.

3D tau-P coherency filtering

Methods and apparatus for processing dual sensor (e.g., hydrophone and vertical geophone) data that includes intrinsic removal of noise as well as enhancing the wavefield separation are provided. The methods disclosed herein are based on a decomposition of data simultaneously into dip and frequency while retaining temporal locality. The noise removed may be mainly coherent geophone noise from the vertical geophone, also known as V(z) noise.

Geophone noise attenuation and wavefield separation using a multi-dimensional decomposition technique

Methods and apparatus for removing noise from signal traces collected during a seismic gather, particularly removing the aliased energy in the time-slowness (tau-P) domain so that aliasing noise does not lead to high noise levels in the inverse transformed data are provided. Removal of the aliasing noise may provide for quieter seismic traces and may increase the likelihood for successful three-dimensional (3-D) tau-P interpolation and detection of seismic events.

3-D TAU-P interpolation

Methods and apparatus for determining an accurate differential transfer function (DTF) between two closely spaced hydrophones in a dual-hydrophone configuration such that the wavefield may be properly separated into up- and down-going components are provided. The methods disclosed herein are based on the premise that the cross-correlation at a lag of zero between up- and down-going wavefields should be at a minimum for perfectly matched hydrophones. Thus, any suitable global optimization technique may be utilized to determine an accurate DTF where the zero-lag cross-correlation between up- and down-going energy is at a minimum after multiplying a particular hydrophone spectrum of the pair (depending on how the DTF was defined) with a possible DTF suggested by the global optimization technique.

Method for determination of differential transfer function between two closely spaced hydrophones

A method for accurately determining travel time separation between dual vertically spaced hydrophones below a water surface to achieve separation of pressure wavefields into an up-going and a down-going wavefield in the frequency domain, and for accurately determining the depth of a vertical mid-point between the dual hydrophones below the water surface.

Method and system for deriving receiver separation and depth dual phone seismic surveys

In a marine seismic survey, water bottom travel times are obtained by conventional methods. Near offset seismic data are then dereverberated using a suite of possible water bottom reflection coefficients to give a suite of filtered traces. The water bottom reflectivity that gives the minimum value over the suite of processed traces is determined to give a set of selected reflectivities each of the analysis points within a time window. A weight is determined for each analysis time within the time window, the weight being related to the change in the amplitude of the filtered trace at that sample point over the suite of water bottom reflectivities. The selected reflectivities are weighted by the weights and averaged to make a determination of the water bottom reflectivity. This determined water bottom reflectivity is used to process the recorded seismic trace. This determined water bottom velocity may also be used to obtain the upcoming dereverberated wavefield in a dual sensor array wherein a hydrophone-geophone combination is used to record data at the ocean bottom.

Method of deriving water bottom reflectivities in the presence of

The objective of this invention is to provide a method for estimating, in the frequency domain, deconvolution operators for removing spurious resonant coupling responses from the cross-line and the vertical seismic signal components in OBC surveys. The purpose is to balance the spectral response of the respective signal component in amplitude and phase in a manner consistent with the field geometry.

Horizontal and vertical receiver-consistent deconvolution for an ocean

A method for determining water bottom reflectivities whereby pressure signals and velocity signals are combined to generate combined signals having signal components representing downwardly-travelling energy substantially removed. The pressure and velocity signals correspond to seismic waves generated at source locations n in a water layer and detected by co-located pressure and velocity receivers at receiver locations m in the water layer. The combined signals correspond to each pairing of source location n and receiver location m. The combined signals are transformed from the time domain to the frequency domain, generating transformed signals. A source peg-leg term and a receiver peg-leg term is calculated for each transformed signal, generating filtered signals. An optimization algorithm is applied to the filtered signals, using the corresponding source and receiver peg-leg terms to determine the water bottom reflectivity values R.sub.n and R.sub.m at the source locations n and the receiver locations m, respectively.

Method for deriving surface consistent reflectivity map from dual sensor

A method for determining ocean bottom reflectivities from dual sensor seismic data, whereby a first time windowed pressure signal and a first windowed velocity signal are summed to generate a first summed signal, and a second time windowed pressure signal and a second time windowed velocity signal are summed to generate a second summed signal. The first summed signal and the second summed signal are transformed from the time domain to the frequency domain to generate a first transformed sum and a second transformed sum, respectively. A value R for said ocean bottom reflectivity is selected and used to calculate an inverse Backus filter (1+Rz).sup.2, where Z is the Z-transform of the two-way travel time delay filter. The first transformed sum and the second transformed sum are multiplied by the inverse Backus filter to generate a first filtered sum and a second filtered sum, respectively. A cross spectrum is calculated from the first filtered sum and the second filtered sum to generate a trial cross spectrum. An optimization algorithm is applied to the trial cross spectrum to determine the ocean bottom reflectivity.

Method for improving the accuracy of ocean bottom reflectivity

The two-way water-layer travel time, .tau., is derived from duel-mode seismic sensor data by cross-correlating the Fourier transforms of the sum and difference of the velocity and pressure signatures. The Z-transform of .tau. evaluates one of the two Backus variables, Z.sub.w. The second variable is R.sub.b, the water bottom reflectivity coefficient. The frequency-domain transforms of the above summed and differenced signatures are each multiplied by the Backus operator (1+R.sub.b Z.sub.w).sup.2 after initializing R.sub.b and the products are iteratively cross-correlated until the correlation function converges to a minimum. R.sub.b is perturbed after each iteration. The value of R.sub.b upon convergence is the local water bottom reflectivity coefficient.

Method for measuring the water bottom reflectivity

A method of reducing effects of noise in seismic signals generated by a plurality of seismic sensors at spaced apart locations from a seismic source is disclosed. Each of the signals is represented by a signal trace in a record section. The method includes the steps of isolating noise in the signal traces, time aligning corresponding portions of the noise in the traces thereby generating time-aligned noise traces, stacking the time-aligned noise trace to generate a stacked noise trace, replicating the stacked noise trace at each corresponding trace position in the record section, restoring the replicated traces to the original trace time positions by reversing the step of time-aligning to generate noise signature traces, comparing the noise signature traces to corresponding signal traces to generate filters which substantially minimize a measure of the difference between the noise signature traces and the signal traces. The noise signature traces are then filtered and the resulting filtered noise signature traces are subtracted from the signal traces. In a preferred embodiment the steps of comparing, generating filters, filtering and subtracting comprise linear adaptive filtering. In a particular embodiment the step of isolating the noise comprises bandpass filtering the signal traces.

Method of reducing noise in seismic signals by adaptive filtering of a

Pressure and velocity seismic signals are combined, the combined signal is transformed into the frequency domain and multiplied by the inverse Backus operator or the combined signal is convolved with the inverse Backus operator, and an optimization algorithm is utilized to solve for water bottom reflectivity. Pressure and velocity seismic signals are combined, and the combined signal is multiplied by the inverse Backus operator containing the water bottom reflectivity to eliminate first order peg leg multiples.

Method for deriving water bottom reflectivity in dual sensor seismic

A method for determining water bottom reflectivity in dual sensor seismic surveys is disclosed. The method eliminates the need for a separate survey to collect calibration data. The method involves summing the pressure and velocity signals, and multiplying the result by the inverse Backus operator, and then solving for the ocean bottom reflectivity R utilizing an optimization algorithm. Also disclosed is a method for combining the dual sensor data which results in the complete elimination of the first order peg-leg multiples and the modulation of the sub-surface reflector strength with the ocean bottom reflectivity. The method involves summing the pressure and velocity signals, and multiplying the result by the inverse Backus operator containing the correct value for the ocean bottom reflectivity R found with the method described above.

Growing community of inventors

Missouri City, TX, United States of America

Josef Paffenholz