Mobil Oil Corporation

Keh Pann

Bonita F Bowman

Denis P Schmitt

Maynard S Redeker

Robert G Keys

David Hinkley

Thomas J Mason

Cynthia T Kalkomey

John A Nieto

Jerry L Fields

A method for eliminating sinusoidal noise without affecting the response of the formation means that the actual formation responses of the logging tools are recovered, and the logs can be used quantitatively. Removal of sinusoidal noise from a log is accomplished in three steps. First, the log is reduced to a zero-mean, stationary series. Second, the wavenumber of the sinusoidal noise is identified by its peak in the Fourier amplitude spectrum. And third, the noise is removed by applying a zero-phase notch filter. In order to preserve the quantitative data integrity, the low wavenumber trend is kept. Preserving the quantitative data integrity is accomplished by approximating the log with a least-squares cubic spline which retains the overall log character, ignoring the sinusoidal noise. A zero mean stationary series is formed by subtracting the least-squares cubic spline from the data. The remaining steps, Fourier analysis and filtering are performed on the difference series. Recombining the filtered series with the spline restores the log data without the sinusoidal noise.

Method for removing borehole rugosity noise from well log data

A method of removing multiple surface reflection events from seismic data is disclosed. Pairs of real seismic traces having end points in common with a trace being analyzed are convolved with one another to yield synthetic multiple traces having real components. All possible combinations of real traces are thus convolved. These are then stacked to yield the synthetic multiple trace having the shortest total travel time, which is the synthetic multiple trace corresponding to the actual multiple reflection event recorded as part of the real trace being analyzed. The stacked synthetic multiple trace can then be subtracted from the real trace under analysis to yield a multiple-free seismic record for further processing.

Removal of surface multiples

Disclosed is a method for constructing an optimal pilot trace from a gather of seismic traces, which pilot trace can be used to obtain statics estimates for time correction of the gathered traces prior to common depth point stacking. During construction of the optimal pilot trace, the statics estimates are inherently obtained.

Method for constructing and using an optimal pilot trace in surface

Disclosed are a method and apparatus for vibratory seismic prospecting in which a vibratory signal sweep is produced by a vibrating apparatus in accordance with a power spectrum function S(f), which is proportional to a noise component function n(f) and a subsurface signal amplitude attenuation function B(f) for an area to be surveyed, to thereby produce reflection signals having an improved signal-to-noise ratio.

Vibratory signal sweep seismic prospecting method and apparatus

In seismic exploration, aliasing caused by coarse sampling along a line of exploration is corrected by trace interpolation. The interpolated traces are obtained by inserting zero amplitude traces between seismic traces. Transformation into the f-k domain and filtering of the aliased regions in the f-k domain produces properly interpolated traces when transformed to the x-t domain.

Seismic trace interpolation using f-k filtering

In seismic exploration, the response characteristics of an array of seismic sources is displayed by contours of equal values of amplitude response as a function of azimuth and dip angle in a stereoscopic polar projection. The projection includes a center point on an axis extending away from the center point representing amplitude response at locations on the line of exploration. Points disposed circumferentially about said axis amplitude response at different azimuth angles from the line of exploration and points at different radial distances from the center point represent amplitude response at different dip angles.

Display of response characteristics of seismic source arrays

In marine seismic exploration, seismic energy is transmitted through a water layer into the earth and seismic reflection signals from subsurface interfaces are recorded. Any undulating water bottom distortion in the recorded reflection signals is removed by replacing the seismic energy velocity in the water layer with a velocity matching that of the earth medium below the water bottom.

Method for enhancing recorded marine seismic reflection signals having

In seismic exploration, seismic reflection signals are obtained along a line of exploration. These seismic reflection signals are time shifted to correct for moveout caused by horizontal dipping and diffraction subsurface events. These connected signals are stacked with a dip independent velocity parameter to provide a zero source-to-receiver seismic record section enhanced in signal-to-noise ratio.

Method for enhancement of the signal-to-noise ratio in seismic

In seismic exploration a seismic source transmits seismic energy into the earth and seismic detectors record the seismic waves returning to the earth's surface from reflecting subsurface interfaces. The downgoing transmitted seismic energy and the upcoming reflected seismic waves are transformed into the frequency domain, downward continued, and summed to produce a migrated seismic depth section.

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Richardson, TX, United States of America

Keh Pann