Robert J Keys

US Patent:

55792480, Nov 26, 1996

Filed:

Jan 9, 1995

Appl. No.:

8/369965

Inventors:

John A. Nieto - Carrollton TX
Denis P. Schmitt - Richardson TX
Robert G. Keys - Dallas TX
Keh Pann - Richardson TX

Assignee:

Mobil Oil Corporation - Fairfax VA

International Classification:

G01V 136
G01V 140

US Classification:

364574

Abstract:

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.

US Patent:

52873285, Feb 15, 1994

Filed:

Jan 28, 1993

Appl. No.:

8/010097

Inventors:

John E. Anderson - Richardson TX
Michael A. Jervis - Austin TX
Robert G. Keys - Dallas TX

Assignee:

Mobil Oil Corporation - Fairfax VA

International Classification:

G01V 136

US Classification:

367 38

Abstract:

Recorded seismic traces are gathered into common offset groups. Within each group, the traces are arranged according to shot point number. Mean and standard deviations are determined for each trace. High frequency amplitude variations in the mean and standard deviations caused by variations in source strengths and receiver calibrations are removed to produce traces of low frequency amplitude variations representing subsurface geology or wave propagation effects.