Measuring petrophysical properties of an earth formation by regularized direct inversion of electromagnetic signals

Patent metadata

Field	Value
Publication number	US-2018203151-A1
Application number	US-201715406308-A
Country	US
Kind code	A1
Filing date	Jan 13, 2017
Priority date	Jan 13, 2017
Publication date	Jul 19, 2018
Grant date	—

Abstract

Methods and apparatus for evaluating an earth formation intersected by a borehole. Methods include using at least one transmitter to generate electromagnetic (EM) waves propagating through the formation; generating measurement signals at at least one receiver responsive to the propagating EM waves; taking a plurality of propagation measurements from the measurement signals representative of the propagating EM waves, where each propagation measurement of the plurality comprises at least one of: i) a relative phase shift between a first wave of the plurality of propagating EM waves and a second wave of the plurality of propagating EM waves; and ii) a relative attenuation between a first wave of the plurality of propagating EM waves and a second wave of the plurality of propagating EM waves; and performing a single inversion which uses the plurality of propagation measurements as input and generates at least one petrophysical parameter as output.

First claim

What is claimed is:

1 . A method of evaluating an earth formation intersected by a borehole, the method comprising:
using at least one transmitter to generate a plurality of electromagnetic (EM) waves propagating through the formation; generating measurement signals at at least one receiver responsive to the plurality of propagating EM waves; taking a plurality of propagation measurements from the measurement signals representative of the propagating EM waves, where each propagation measurement of the plurality comprises at least one of: i) a relative phase shift between a first wave of the plurality of propagating EM waves and a second wave of the plurality of propagating EM waves; and ii) a relative attenuation between a first wave of the plurality of propagating EM waves and a second wave of the plurality of propagating EM waves; performing a single inversion which uses the plurality of propagation measurements as input and generates at least one petrophysical parameter as output.

2 . The method of claim 1 wherein the inversion comprises a single step.

3 . The method of claim 1 wherein the inversion is performed on the at least one petrophysical parameter and the plurality of propagation measurements simultaneously.

4 . The method of claim 1 comprising wherein the plurality of EM waves are generated by the at least one transmitter at a plurality of frequencies.

5 . The method of claim 1 , comprising:
selecting at least one petrophysical mixing model for the inversion; regularizing the inversion.

6 . The method of claim 5 wherein regularizing the inversion comprises incorporating a priori data into the inversion, the a priori data comprising information about probable values of parameters in the mixing model.

7 . The method of claim 6 wherein the a priori data comprises a probability distribution function representing the probable values of the parameters of the mixing model.

8 . The method of claim 5 wherein regularizing the inversion comprises incorporating a priori data into the inversion, the a priori data comprising information about probable values of formation properties constraining the inversion.

9 . The method of claim 6 wherein the a priori data comprises a probability distribution function representing the probable values of the formation properties.

10 . The method of claim 5 comprising selecting the at least one petrophysical mixing model in dependence upon at least one estimated lithology of the formation.

11 . The method of claim 1 comprising representing predicted EM properties of the formation as a dispersive relation for calculated permittivity values and conductivity values of the formation.

12 . The method of claim 11 comprising using the EM properties to simulate tool responses using a forward model to generate predicted responses.

13 . The method of claim 12 comprising, in response to determining the predicted responses are not substantially similar to the plurality of propagation measurements, modifying at least one of: i) the at least one petrophysical mixing model; and ii) the forward model.

14 . The method of claim 1 comprising generating an electrical property of the formation as output.

15 . The method of claim 1 wherein the electrical property comprises at least one of: i) a frequency dependent conductivity parameter; and ii) a frequency dependent permittivity parameter.

16 . The method of claim 1 comprising estimating a solution space for the at least one petrophysical parameter.

17 . The method of claim 1 wherein performing the single inversion comprises using a discretized formation model as a forward model.

18 . The method of claim 1 wherein performing the single inversion comprises including at least one petrophysically based regularization model in the inversion.

19 . An apparatus for evaluating an earth formation intersected by a borehole, the apparatus comprising:
at least one processor; and a computer memory accessible to the at least one processor comprising a computer-readable medium having instructions thereon that, when executed, causes the at least one processor to perform a method, the method comprising:
using at least one transmitter to generate a plurality of electromagnetic (EM) waves propagating through the formation;
generating measurement signals at at least one receiver responsive to the plurality of propagating EM waves;
taking a plurality of propagation measurements from the measurement signals representative of the propagating EM waves, where each propagation measurement of the plurality comprises at least one of: i) a relative phase shift between a first wave of the plurality of propagating EM waves and a second wave of the plurality of propagating EM waves; and ii) a relative attenuation between a first wave of the plurality of propagating EM waves and a second wave of the plurality of propagating EM waves;
performing a single inversion which uses the plurality of propagation measurements as input and generates at least one petrophysical parameter as output.

Assignees

• Baker Hughes Inc

Inventors

• Kouchmeshky Babak
• Fanini Otto N
• Mezzatesta Alberto

Classifications

• G01V3/30 Primary

  operating with electromagnetic waves · CPC title

• G01V3/38

  Processing data, e.g. for analysis, for interpretation, for correction · CPC title

• G01V3/26 Primary

  operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device (with electromagnetic waves G01V3/30) · CPC title