Data reduction of images measured in a borehole

Patent metadata

Field	Value
Publication number	US-10302811-B2
Application number	US-19581008-A
Country	US
Kind code	B2
Filing date	Aug 21, 2008
Priority date	Aug 21, 2008
Publication date	May 28, 2019
Grant date	May 28, 2019

Abstract

A data reduction method for transmission of a borehole image to the surface of the earth using restricted band widths of LWD telemetry systems. The data reduction method is based on the measurement physics rather than mathematical compression algorithms. Measured data from a sensor are fitted, within the logging tool, to a response function relating sensor response to a parameter of interest. The coefficients of the fitted response function are scaled and then telemetered to the surface. The measured data are reconstructed at the surface by combining the telemetered coefficients with the response function. A borehole image is formed by combining reconstructed reduced data. Parameters of dipping beds intersecting the borehole can be determined from the coefficients.

First claim

What is claimed is:

1. A method of improving imaging of a formation feature intersected by a borehole in a formation by improving transmission of image data from the borehole to surface equipment at surface, the method comprising:
drilling the borehole in the formation;
imaging the formation by measuring, while drilling the borehole, borehole image data of the intersected formation feature in the borehole using a logging tool sensor of a logging tool disposed in the borehole;
performing within the logging tool disposed in the borehole, the steps of:
fitting the measured borehole image data to an azimuthally dependent response function of the logging tool sensor, the response function representing measurement physics of the logging tool, wherein the fitting includes determining one or more response function coefficients;
scaling the one or more response function coefficients to a predetermined number of bits, wherein the scaled coefficients combined with the response function represent reduced measured data; and
telemetering the scaled coefficients to the surface equipment using a telemetry unit of the logging tool; and

generating, from the response function and the telemetered scaled coefficients, a resulting borehole image at the surface to determine a characteristic of the intersected formation feature.

2. The method of claim 1 wherein the response function is a modified Gaussian function having five coefficients.

3. The method of claim 2 wherein:
variation in at least one of the response function coefficients indicates a dipping bed interface intersecting the borehole; and
magnitude of at least one of the response function coefficients indicates an azimuthal direction of the dipping bed interface.

4. The method of claim 3 wherein zero crossings of a second derivative of said response function yields azimuthal angles at which a bed boundary interface intersects said borehole.

5. The method of claim 2 wherein the response function is of the form

f
⁡

(
ϕ
)

=

A
5

+

A
4

⁢

e

-
0.5

⁢

(



ϕ
-

A
1



A
2

)

A
3

wherein:
ϕ is an azimuthal angle;
A1 is a coefficient representing an angle of azimuthal interface with a dipping bed, the angle of azimuthal interface being measured with respect to the borehole's longitudinal axis;
A2 is a coefficient proportional to an azimuthal resolution of the tool;
A3 is a coefficient indicative of a contrast between two beds crossed;
A4 is a coefficient indicative of a difference of tool response amplitude between two formations; and
A5 is a coefficient indicative of a tool response amplitude for one of the formations.

6. The method of claim 1 further comprising:
performing at the surface equipment, the steps of:
receiving the telemetered coefficients from the logging tool; and
combining the received coefficients with the response function to reconstruct reduced data thereby forming the resulting borehole image.

7. The method of claim 1 , further comprising determining, at surface, the characteristic of the intersected formation feature.

8. The method of claim 7 , wherein determining, at surface, the characteristic of the intersected formation feature comprises determining, at surface, a direction of a dipping bed intersected by the borehole.

9. A logging tool for improving imaging of a formation feature intersected by a borehole in a formation by improving transmission of image data from the borehole to a surface-located telemetry unit at surface, the logging tool comprising:
a logging tool body disposed on a drilling assembly drilling the borehole in the formation;
a logging tool sensor disposed on the logging tool body and measuring, while drilling the borehole, data representative of a borehole image of the intersected formation feature in the borehole;
a processor disposed on the logging tool body, the processor operationally connected to the logging tool sensor and programmed to:
fit the measured data representative of the borehole image to a response function of the logging tool sensor, the response function representing measurement physics of the logging tool, wherein the fitting includes determining one or more response function coefficients; and
scale the one or more response function coefficients to a predetermined number of bits; and

a telemetry unit disposed on the logging tool body, the telemetry unit cooperating with the processor and configured to telemeter the scaled coefficients to the surface-located telemetry unit, the response function and the telemetered scaled coefficients configured to generate a resulting borehole image at surface to determine a characteristic of the intersected formation feature.

10. The logging tool of claim 9 wherein the logging tool body is configured to be operationally connected to surface equipment by a drill string of the drilling assembly.

11. The apparatus of claim 10 wherein the processor is further programmed to:
measure variation in one or more of the response function coefficients to identify a dipping bed interface intersecting said borehole;
measure a magnitude of one or more of the response function coefficients to compute azimuthal direction of the dipping bed interface.

12. The apparatus of claim 11 wherein the processor is further programmed to:
compute a second derivative of the fitted response function;
determine zero crossings of the second derivative; and
determine from the zero crossings azimuthal angles at which a bed boundary interface intersects said borehole.

13. The logging tool of claim 9 wherein the response function is of the form

f
⁡

(
ϕ
)

=

A
5

+

A
4

⁢

Assignees

• Mickael Medhat W
• Weatherford Tech Holdings Llc

Inventors

• Mickael Medhat W

Classifications

• E21B47/12 Primary

  Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling · CPC title

• G01V1/48

  Processing data · CPC title

• G01V11/002 Primary

  Details, e.g. power supply systems for logging instruments, transmitting or recording data, specially adapted for well logging, also if the prospecting method is irrelevant (means for transmitting well survey signals E21B47/12; signal transmission systems in general G08C; transmission in general H04B) · CPC title

• E21B47/00 Primary

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

• G01V5/045

  Transmitting data to recording or processing apparatus; Recording data · CPC title