High resolution LWD imaging

Patent metadata

Field	Value
Publication number	US-9658360-B2
Application number	US-201113310389-A
Country	US
Kind code	B2
Filing date	Dec 2, 2011
Priority date	Dec 3, 2010
Publication date	May 23, 2017
Grant date	May 23, 2017

Abstract

A method for forming a high resolution logging while drilling image includes receiving a logging while drilling data set and selecting a borehole grid. The borehole grid includes a plurality of pixels that define discrete azimuthal positions and depth positions in the borehole. The LWD data set is mapped to the selected borehole grid such that an azimuthal position and a depth position are assigned to each data point in the data set. An interpolation routine is used to fill empty pixels. Disclosed embodiments enable high resolution LWD imaging that may resolve various fine formation features such as fractures, fine bedding layers, breakout, and vugs.

First claim

What is claimed is:

1. A method for forming an image of logging data, the method comprising:
(a) receiving a logging while drilling data set that comprises a first number data points obtained by a logging-while-drilling tool over a plurality of depths and at a plurality of azimuthal positions over the plurality of depths, at a processor;
(b) selecting a borehole grid, the borehole grid including a plurality of pixels defining discrete azimuthal positions and depth positions in a borehole, in the processor, wherein the borehole grid comprises a second number of pixels, wherein the second number of pixels is greater than the first number of data points in the logging while drilling data set;
(c) mapping each of the data points of the logging while drilling data set received in (a) to at least one pixel the borehole grid selected in (b) such that an azimuthal position and a depth position is assigned to each data point in the data set, while at least one pixel is not mapped to any of the data points and therefore is empty, in the processor; and
(d) filling the at least one empty pixel determined from (c) with an interpolated data value via interpolation to obtain the image of the logging data, in the processor.

2. The method of claim 1 , wherein the logging while drilling data set received in (a) comprises at least one of ultrasonic standoff data, gamma ray data, density data, or photoelectric effect data.

3. The method of claim 1 , wherein the logging while drilling data set received in (a) is acquired in a borehole including a non-conductive drilling fluid.

4. The method of claim 1 , wherein the logging while drilling data set received in (a) comprises a time stamped set of logging while drilling data acquired at a predetermined time interval.

5. The method of claim 4 , wherein the logging while drilling data set further comprises a time stamped set of azimuth measurements.

6. The method of claim 1 , wherein the logging while drilling data set is received at a surface location in (a) from memory in a logging while drilling tool.

7. The method of claim 1 , wherein the borehole grid includes from about 32 to about 512 azimuthal positions and about 2 to about 50 depth positions per foot of measured depth in the borehole.

8. The method of claim 1 , wherein the mapping in (c) comprises processing the data set in combination with a set of azimuth measurements and a set of measured depth measurements such that an azimuthal position and a depth position is assigned to each data point in the data set.

9. The method of claim 1 , wherein said interpolation in (d) includes computing an average or weighted average value of a predetermined number of nearest neighbor pixel values at each pixel location.

10. The method of claim 9 , wherein a weighted average is computed in which a midpoint of a Gaussian distribution is centered on each of said selected pixel locations.

11. The method of claim 1 , further comprising: (e) applying a one-dimensional robust estimation technique to the data set prior to said mapping in (c).

12. The method of claim 1 , further comprising: (e) applying a two-dimensional robust estimation technique to the data set after said mapping in (c).

13. The method of claim 1 , further comprising: (e) further processing the image using a histogram equalization or a deconvolution technique after said filling in (d).

14. A method for imaging a subterranean formation, the method comprising:
(a) rotating a logging while drilling tool in a borehole, the logging while drilling tool including at least one logging sensor;
(b) causing the logging sensor to acquire a data set that comprises a first number of data points while rotating in (a);
(c) saving the data set to a downhole memory;
(d) receiving the data set at a surface location;
(e) selecting a borehole grid, the borehole grid including a plurality of pixels defining discrete azimuthal positions and depth positions in a borehole, wherein the borehole grid comprises a second number of pixels, wherein the second number of pixels of the borehole grid is greater than the first number of data points in the data set;
(f) mapping the logging while drilling data set received in (d) to the borehole grid selected in (e) such that an azimuthal position and a depth position is assigned to each data point in the data set, but not every pixel is mapped to one of the data points; and
(g) filling empty pixels that were not mapped to one of the data points in step (f) with interpolated data values via interpolation.

15. The method of claim 14 , wherein the borehole includes a non-conductive drilling fluid.

16. The method of claim 14 , wherein the logging sensor comprises a gamma ray sensor or an ultrasonic standoff sensor and wherein the data set comprises ultrasonic standoff data, gamma ray data, density data, or photoelectric effect data.

17. The method of claim 14 , wherein: the logging while drilling data set received in (d) comprises a time stamped set of logging while drilling data acquired at a predetermined time interval; the logging while drilling data set further comprises a time stamped set of azimuth measurements; and the mapping in (e) comprises processing the logging while drilling data in combination with the azimuth measurements and a set of measured depth measurements such that an azimuthal position and a depth position is assigned to each logging while drilling data point.

18. The method of claim 14 , wherein said interpolation in (d) includes computing an average or weighted average value of a predetermined number of nearest neighbor pixel values at each pixel location.

19. The method of claim 18 , wherein a weighted average is computed in which a midpoint of a Gaussian distribution is centered on each of said selected pixel locations.

20. The method of claim 14 , further comprising at least one of the following:
(h) applying robust estimation technique to the data set prior to said mapping in (f); and (i) applying at least one of a histogram equalization and a deconvolution technique to the image after said filling in (d).

Assignees

• Hollmann Joseph L
• Kirkwood Andrew
• Schlumberger Technology Corp

Inventors

• Hollmann Joseph L
• Kirkwood Andrew

Classifications

• G01V3/38 Primary

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