Identifying antenna system parameter changes

Patent metadata

Field	Value
Publication number	US-2018138992-A1
Application number	US-201615354709-A
Country	US
Kind code	A1
Filing date	Nov 17, 2016
Priority date	Nov 17, 2016
Publication date	May 17, 2018
Grant date	—

Abstract

Systems, methods, and devices for evaluation of an earth formation intersected by a borehole using a logging tool. Methods include performing EM logging in a borehole intersecting an earth formation using a measurement signal from an antenna system in the borehole, the measurement signal dependent upon a parameter of interest of the formation and at least one antenna system parameter of the antenna system, comprising feeding a calibration signal into a signal path of the antenna system to generate a resultant signal; estimating at least one value of the at least one antenna system parameter by using the resultant signal; and performing further logging operations in dependence upon the at least one value of the at least one antenna system parameter. The calibration signal comprises at least two calibration subsignals with a first calibration subsignal having a first frequency and a second calibration subsignal having a second frequency.

First claim

What is claimed is:

1 . A method for performing electromagnetic (EM) logging in a borehole intersecting an earth formation using a measurement signal from an antenna system in the borehole, the measurement signal dependent upon a parameter of interest of the formation and at least one antenna system parameter of the antenna system, the method comprising:
feeding a calibration signal into a signal path of the antenna system to generate a resultant signal; estimating at least one value of the at least one antenna system parameter by using the resultant signal; and performing further logging operations in dependence upon the at least one value of the at least one antenna system parameter; the calibration signal comprising at least two calibration subsignals with a first calibration subsignal of the at least two calibration subsignals having a first frequency and a second calibration subsignal of the at least two calibration subsignals having a second frequency different than the first frequency.

2 . The method of claim 1 , wherein the at least one antenna system parameter comprises at least one of:
i) a transfer function of at least a part of the antenna system; ii) a frequency of an extreme value of the transfer function of at least a part of the antenna system; and iii) a width of a peak of the transfer function.

3 . The method of claim 1 , wherein the at least one antenna system parameter comprises at least one of:
i) resonance frequency of the antenna system; ii) antenna system impedance; iii) antenna system moment; iv) antenna system inductance; v) antenna system capacitance; vi) antenna system resistance; and vii) antenna system quality factor.

4 . The method of claim 1 wherein the antenna system comprises a transmitter assembly configured to transmit an excitation signal and a receiver assembly configured to receive the measurement signal.

5 . The method of claim 1 wherein the calibration signal comprises at least three calibration subsignals, each calibration subsignal of the at least three calibration subsignals having a unique frequency.

6 . The method of claim 5 wherein the at least three calibration subsignals form at least one swept frequency signal.

7 . The method of claim 1 wherein a first signal of the at least two calibration subsignals is fed into the signal path during a period of time that overlaps with a second signal of the at least two calibration subsignals fed into the signal path.

8 . The method of claim 1 wherein a first subsignal of the at least two calibration subsignals is fed into the signal path during a first period of time and a second subsignal of the at least two calibration subsignals is fed into the signal path during a second period of time different than the first period of time.

9 . The method of claim 1 further comprising:
monitoring values of the antenna system parameter over time;
detecting changes in values of the antenna system parameter meeting a threshold value; and
responsive to detecting antenna system parameter changes meeting the threshold value, performing at least one of:
i) storing at least one of the values; ii) transmitting at least one of the values to the surface; and iii) notifying a system operator.

10 . The method of claim 1 wherein performing further logging operations comprises determining a value of the parameter of interest of the formation.

11 . The method of claim 1 wherein performing further logging operations comprises performing at least one of:
i) adjustment of a measurement signal;
ii) adjustment of the signal path;
iii) adjustment of an excitation signal of the logging tool.

12 . The method of claim 1 comprising estimating a resonance frequency of the antenna system by performing at least one of:
i) estimating a frequency of an extreme value of the transfer function of at least a part of the system; and
ii) estimating a width of a resonance peak of a transfer function.

13 . The method of claim 1 wherein:
the antenna system comprises at least one electronic component; and
the logging operation comprises adjustment of at least one of the at least one electronic component.

14 . An apparatus for evaluating an earth formation intersected by a borehole, the apparatus comprising:
an electromagnetic (EM) logging tool configured for conveyance in the borehole on a tool string, and further configured to generate an excitation in the formation with an EM signal from at least one antenna system on the tool at at least one frequency; at least one receiver assembly on the EM tool configured to make EM measurements by receiving a signal at the at least one antenna system responsive to the excitation; at least one processor; and an antenna system including an antenna connected to the at least one processor via a signal path and configured to provide a measurement signal to the at least one processor responsive to the EM measurements, the measurement signal dependent upon a parameter of interest of the formation and at least one antenna system parameter of the antenna system; wherein the at least one processor is configured to:
feeding a calibration signal into the signal path of the logging tool to generate a resultant signal;
estimating at least one value of the at least one antenna system parameter by using the resultant signal; and
performing further logging operations in dependence upon the at least one value of the at least one antenna system parameter;
the calibration signal comprising at least two calibration subsignals with a first subsignal of the at least two calibration subsignals having a first frequency and a second subsignal of the at least two calibration subsignals having a second frequency different than the first frequency.

15 . The apparatus of claim 14 further comprising a tool string.

16 . The apparatus of claim 15 wherein the tool string is a drill string, and the apparatus comprises a drill bit at a distal end of the drill string.

17 . The apparatus of claim 14 wherein the antenna system comprises a transmitter assembly configured to transmit an excitation signal and a receiver assembly configured to receive the measurement signal.

18 . The apparatus of claim 14 , further comprising at least one electronic component configured to be adjusted based on the at least one value of the at least one antenna system parameter.

19 . The apparatus of claim 14 , wherein the at least one antenna system parameter comprises at least one of:
i) a transfer function of at least a part of the antenna system; ii) a frequency of an extreme value of the transfer function of at least a part of the antenna system; and iii) a width of a peak of the transfer function.

20 . The apparatus of claim 14 , wherein the at least one antenna system parameter comprises at least one of:
i) resonance frequency of the antenna system; ii) antenna system impedance; iii) antenna system moment; iv) antenna system inductance; v) antenna system capacitance; vi) antenna system resistance; and vii) antenna system quality factor.

Assignees

• Baker Hughes Inc

Inventors

• Kraft Kersten
• Le Trung H

Classifications

• H04B17/12 Primary

  of transmit antennas, e.g. of the amplitude or phase · CPC title

• H04B17/102

  Power radiated at antenna · CPC title

• H01Q1/04

  Adaptation for subterranean or subaqueous use · CPC title

• G01R29/10

  Radiation diagrams of antennas · CPC title

• H03H7/38

  Impedance-matching networks · CPC title