Global patent index - EP 0991958 A1

EP 0991958 A1 2000-04-12 - METHOD FOR REMOVING BOREHOLE RUGOSITY NOISE FROM WELL LOG DATA

Title (en)

METHOD FOR REMOVING BOREHOLE RUGOSITY NOISE FROM WELL LOG DATA

Title (de)

VERFAHREN ZUM UNTERDRUCKEN VON BOHRLOCHRAUHEITSGERAUSCH VON BOHRLOCHDATEN.

Title (fr)

PROCEDE PERMETTANT D'ELIMINER LE BRUIT DE RUGOSITE D'UN PUITS DE FORAGE DANS DES DONNEES DE DIAGRAPHIE DE PUITS

Publication

EP 0991958 A1 (EN)

Application

EP 96902668 A

Priority

US 9600449 W

Abstract (en)

[origin: WO9726559A1] A method for removing 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 (18). And third, the noise is removed by applying a zero-phase notch filter (46). 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.

IPC 1-7 (main, further and additional classification)

G01V 1/36; G01V 1/48

IPC 8 full level (invention and additional information)

G01V 1/36 (2006.01); G01V 1/48 (2006.01)

CPC (invention and additional information)

G01V 1/48 (2013.01); G01V 1/364 (2013.01); G01V 2210/32 (2013.01)

Designated contracting state (EPC)

DE FR GB NL

EPO simple patent family

WO 9726559 A1 19970724; EP 0991958 A1 20000412; EP 0991958 A4 20000412

INPADOC legal status

2009-11-04 [18D] DEEMED TO BE WITHDRAWN

- Ref Legal Event Code: 18D

- Effective date: 20021214

2001-10-31 [RAP1] TRANSFER OF RIGHTS OF AN EP PUBLISHED APPLICATION

- Owner name: EXXONMOBIL OIL CORPORATION

- Ref Legal Event Code: RAP1

2000-04-12 [17P] REQUEST FOR EXAMINATION FILED

- Ref Legal Event Code: 17P

- Effective date: 19980731

2000-04-12 [A4] SUPPLEMENTARY SEARCH REPORT

- Ref Legal Event Code: A4

- Effective date: 20000114

2000-04-12 [AK] DESIGNATED CONTRACTING STATES:

- Ref Legal Event Code: AK

- Designated State(s): DE FR GB NL

2000-04-12 [AK] DESIGNATED CONTRACTING STATES:

- Ref Legal Event Code: AK

- Designated State(s): DE FR GB NL