Focused array laterolog tool

Patent metadata

Field	Value
Publication number	US-9239402-B2
Application number	US-201214370188-A
Country	US
Kind code	B2
Filing date	Jan 3, 2012
Priority date	Jan 3, 2012
Publication date	Jan 19, 2016
Grant date	Jan 19, 2016

Abstract

Various embodiments include apparatus and methods to make resistivity measurements in a borehole using tool having an array of electrodes operable to provide focused currents and measure corresponding voltages to determine resistivity. Tools can be configured with a main electrode having a number of spaced apart electrodes within the main electrode such that the spaced apart electrodes are arranged azimuthally with respect to an axis of the tool. Generation of current from the spaced apart electrodes and control of current from additional electrodes on each side of the main electrode can provide for focused measurements. Additional apparatus, systems, and methods are disclosed.

First claim

What is claimed is:

1. An apparatus comprising:
a main electrode of a tool, the main electrode having a number of spaced apart electrodes within the main electrode, the spaced apart electrodes arranged azimuthally with respect to an axis of the tool;
a first number of electrodes to one side of the main electrode along the axis and a second number of electrodes on another side of the main electrode along the axis;
a number of monitor electrodes arranged along the axis of the tool from the main electrode such that voltages to the number of monitor electrodes are operatively controlled with respect to current operatively generated from the spaced apart electrodes of the main electrode; and
a control unit to operatively control generation of a current pattern selected from a plurality of modes, each mode having current generated from the main electrode, from one or more electrodes of the first number of electrodes to only one non-current generating electrode of the first number of electrodes, the one non-current generating electrode operatively selected according to the mode, and from one or more electrodes of the second number of electrodes to only one non-current generating electrode of the second number of electrodes, the one non-current generating electrode operatively selected according to the mode, wherein at least one mode of the plurality of the modes has a plurality of non-current generating electrodes selected from each of the first number of electrodes and the second number of electrodes.

2. The apparatus of claim 1 , wherein the main electrode includes a main monitor electrode separated from the spaced apart electrodes by an insulator.

3. The apparatus of claim 2 , wherein the insulator separates a first spaced apart electrode from a second spaced electrode within the main electrode.

4. The apparatus of claim 1 , wherein the number of spaced apart electrodes equals two or more, the spaced apart electrodes wrapped around the axis of the tool.

5. The apparatus of claim 1 , wherein each one of the first number of electrodes is coupled to a corresponding one of the second number of electrodes.

6. The apparatus of claim 1 , wherein the control unit is arranged to selectively control the first number of electrodes and the second number of electrodes such that selected ones of the first number of electrodes and the second number of electrodes receive current from the spaced apart electrodes of the main electrode.

7. The apparatus of claim 6 , wherein the control unit is arranged to generate current from other selected ones of the first number of electrodes and the second number of electrodes based on a selected current pattern.

8. The apparatus of claim 7 , wherein the control unit is arranged to adjust the current such that a potential difference between selected ones of the monitored electrodes equals a reference potential.

9. The apparatus of claim 1 , wherein the apparatus includes a control unit to selectively control the main electrode, the first number of electrodes, and the second number of electrodes to generate a current pattern, k, such that a monitor electrode, M 0 , for the main electrode has a reference potential, VM 0 k , for each current pattern k, VM 0 k given by

VM
⁢

⁢

0
k

=

∑

i
=
1

N

⁢

⁢

VM
⁢

⁢
0
⁢

(

k
,
i

)

N

,

where N equals the number of spaced apart electrodes of the main electrode and where VM 0 (k,i) is the potential at M 0 for the current pattern k for spaced apart electrode i, i=1, . . . , N.

10. The apparatus of claim 9 , wherein the apparatus includes a data processing unit to process measured voltages to generate a resistivity, R(k,i) for the current pattern k for the i th spaced apart electrode, R(k,i) given by

R
⁡

(

k
,
i

)

=

K
⁢

⁢
k
⁢

∑

j
=
1

N

⁢

⁢

VM
⁢

⁢
1
⁢

(

k
,
j

)

*

C
⁡

(

k
,
j

)

N
*
IA
⁢

⁢
0
⁢

(

k
,
i

)

⁢

(

i
=
1

Assignees

• Li Shanjun
• Bittar Michael S
• Halliburton Energy Services Inc

Inventors

• Li Shanjun
• Bittar Michael S

Classifications

• G01V99/00

  Subject matter not provided for in other groups of this subclass · CPC title

• G01V3/24 Primary

  using AC · CPC title

• G01V3/20 Primary

  operating with propagation of electric current · CPC title