Time domain electromagnetic tensor based logging method

Patent metadata

Field	Value
Publication number	US-12189079-B2
Application number	US-202218569602-A
Country	US
Kind code	B2
Filing date	Oct 28, 2022
Priority date	Oct 29, 2021
Publication date	Jan 7, 2025
Grant date	Jan 7, 2025

Abstract

A time domain electromagnetic tensor based logging method, relating to the field of induction logging. A transmitting coil system Tx and a receiving coil system Rx are each composed of three orthogonal direction coils, and the transmitting coil system and the receiving coil system form a borehole probe; a time domain electromagnetic field is excited by means of two orthogonal transmitting coil systems Tx, and a secondary field signal is received by two orthogonal receiving coil systems Rx located above transmitting coils and having a distance D; during each measurement, three directions are used for transmitting, nine component data is received at the same time, and each component is a series of induction potentials in one-to-one correspondence with measurement time sequences, and a potential or resistance change, from near to far, of the rock stratum where a measurement point is located is obtained after time-depth conversion.

First claim

What is claimed is:

1. A logging method based on a time-domain electromagnetic tensor, wherein the logging method comprises:
constructing a transmitting coil system Tx and a receiving coil system Rx, wherein the transmitting coil system Tx and the receiving coil system Rx are respectively composed of three coils in different directions and orthogonal to each other, and a borehole probe is formed by the transmitting coil system Tx and the receiving coil system Rx;
setting a measurement point; exciting, through the transmitting coil system Tx, a time-domain electromagnetic field;
receiving, by the receiving coil system Rx located above the transmitting coil system Tx with a distance D, secondary field signals;
receiving the secondary field signals in three component directions simultaneously to obtain nine component data, wherein each component data is a series of induction potentials corresponding to measurement time series one by one;
obtaining, through each measurement time series, a potential sequence or a resistivity value changing over time for a layer where a corresponding measurement point is located; and
obtaining, after a time-depth conversion, a change on a potential or a resistivity of the layer where the corresponding measurement point is located,
wherein a method for obtaining each resistivity value and induction potential of a magnetic field intensity is as follows:
setting a stratigraphic coordinate system (x,y,z) and an instrument coordinate system (x′,y′,z′), setting θ as an azimuth angle of an instrument tilted, and β as a self-rotation angle of the instrument during a measuring process and a rotation angle of the instrument during a descending process, that is the azimuth angle of the instrument;
wherein equivalent magnetic moments in three directions of transmitting coils in the borehole probe are M x′ , M y′ , M z′ , and a relationship between magnetic field intensities H x′ , H y′ , H z′ , received by receiving coils in three directions of the borehole probe and the equivalent magnetic moments is:

(

H
x
′

H
y
′

H
z
′

)

-

R
T

_

·

G
_

·

R
_

·

(

M
x
′

M
y
′

M
z
′

)

where G denotes a Dyadic Green's function, R denotes a transformation matrix from the instrument coordinate system to the stratigraphic coordinate system, and R T denotes a transpose matrix of R , and a formula for calculating the Dyadic Green's function G by adopting a transmission line equivalent principle is as follows:

=

[

G
~

xx
HM

G
~

xy
HM

G
~

xz
HM

G
~

yx
HM

G
~

yy
HM

G
~

yz
HM

G
~

zx
HM

G
~

zy
HM

G
~

zz
HM

]

=

[

-

k
x
2

k
ρ

Assignees

• Univ China Mining

Inventors

• Yang Haiyan
• Yue Jianhua
• Liu Zhixin
• Hu Shuanggui
• Xu Yunlei
• Li Wenyu
• Ran Huageng
• Che Rongqi
• Sun Menglang
• Li Zhenyang

Classifications

• G01V3/38

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

• Y02A90/30

  Assessment of water resources · CPC title

• E21B49/00

  Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells · CPC title

• E21B47/00

  Survey of boreholes or wells (monitoring pressure or flow of drilling fluid E21B21/08) · CPC title

• G01V3/28 Primary

  using induction coils · CPC title