Automatic dip picking in borehole images
The techniques and device provided herein relate to receiving, via a processor, image data representative of a borehole of a well. The technique may include generating dequantized image data based on the image data, such that the dequantized image data filters one or more artifacts present in a Hough transformed version of the image data. One or more dip orientations (inclination and azimuth) associated with one or more formation dips present in the image data may be determined based on the dequantized image data. The technique may also include performing an a-contration validation algorithm for for the one or more formation dips to verify whether at least a formation dip having the or one of the possible dip orientation is present at a predetermined measured depth in the image data.
1. A method, comprising:
receiving, via a processor, image data representative of a borehole image obtained by a downhole tool;
generating, via the processor, dequantized image data based on the image data, wherein the dequantized image data filters one or more artifacts present in a Hough transformed version of the image data;
determining, via the processor, one or more possible dip orientations associated with one or more formation dips present in the image data based on the dequantized image data;
performing, via the processor, an a-contrario validation algorithm for the one or more formation dips to verify whether at least a formation dip having the or one of the possible dip orientation is present at a predetermined measured depth in the image data.
2. The method of claim 1 , wherein generating the dequantized image data comprises applying a Gaussian blur to the image data.
3. The method of claim 1 , wherein determining one or more possible dip orientations includes determining, via the processor, local orientations of each pixel of the borehole image.
4. The method of claim 1 , wherein determining the one or more possible dip orientations comprise applying a Hough transform to the dequantized image data.
5. The method of claim 3 , wherein determining the one or more possible dip orientations comprise applying a Hough transform to the dequantized image data and wherein determining the one or more possible dip orientation comprises performing, via the processor, Hough voting on the one or more local orientations, representing the votes in a Hough transformed image, the determination being based on the Hough voting.
6. The method of claim 5 , wherein the one or more possible dip orientation correspond to a local or global maximum of the Hough transformed image.
7. The method of claim 4 , comprising performing, via the processor, Hough smoothing on the Hough transform image before determining the one or more possible dip orientation.
8. The method of claim 1 , wherein determining the dip orientation includes using a sliding window on the borehole image, the determination being performed for each window.
9. The method of claim 1 , wherein performing an a contrario validation algorithm comprises using statistical tests.
10. The method of claim 1 , including determining an optimal scale parameter of the borehole image and scaling the image data according to the scale parameter before dequantizing the image.
11. The method of claim 1 , including scaling the image data according to a plurality of scaling parameters in order to obtain from a borehole image a plurality of scaled image, wherein the method comprise determining formation dips from at least two scaled images of the plurality.
12. The method of claim 2 , comprising determining an optimal blur parameter and applying the Gaussian blur according to the optimal blur parameter.
13. The method of claim 2 , comprising applying a plurality of Gaussian blurs to the image data, each Gaussian blur being according to a specific blur parameter in order to obtain from a borehole image a plurality of dequantized images, wherein the method comprises determining formation dips from at least two dequantized images of the plurality.
14. A system, comprising:
a downhole tool configured to be disposed within a wellbore of a well, wherein the downhole tool is configured to acquire measurements regarding the wellbore, and wherein the measurements are used to generate an image of the wellbore;
a processor configured to identify one or more formation dips within the image by:
receiving the image;
generating a dequantized image based on the image, wherein the dequantized image filters one or more artifacts present in a Hough transformed version of the image;
determining one or more possible dip orientations associated with one or more formation dips present in the image data based on the dequantized image data;
performing an a-contrario validation algorithm for the one or more formation dips to verify whether at least a formation dip having the or one of the possible dip orientation is present at a predetermined measured depth in the image data.
15. The system of claim 14 , comprising a drilling tool configured to drill into the wellbore based on the one or more formation dips.