Seismic horizon autopicking using orientation vector field
A method is disclosed for automatically extending interpreter horizon picks over a wider area of traces in such manner that the automatically generated picks are very similar to picks that an interpreter would pick manually. The method applies optical filters to seismic sections to determine the intrinsic orientation of seismic events. Seismic orientation is captured in the Orientation Vector Field, which is then used to guide the picking process.
1. A method for determining a horizon in a two-dimensional seismic section from an initial pick point on the horizon, the seismic section comprising a plurality of samples, wherein each sample is referenced using the variable x and y as the coordinates of the sample in the seismic section, the method comprising:
convolving a set of optical filters with the seismic section to obtain a set of responses, wherein, for each sample, there are corresponding response values associated with the x and y coordinates of the sample, the optical filters having various center orientation values;
determining an orientation vector for each sample based on the response value associated with the x and y coordinates of the sample;
creating an orientation vector field comprising the orientation vectors of all the samples and storing the orientation vector field; and
using a computer processor to determine the horizon by following the orientation vectors of the samples in the orientation vector field, beginning with the initial pick point on the horizon.
2. The method of claim 1 , wherein the optical filters are modified Log-Gabor filters.
3. The method of claim 1 , wherein the orientation vector for each sample is determined based on the maximum response value associated with the x and y coordinates of the sample.
4. The method of claim 1 , wherein determining an orientation vector comprises:
comparing response values associated with the x and y coordinates of the sample for different optical filters of the set of optical filters;
determining a maximum response value;
selecting the optical filter corresponding to the maximum response value; and
setting the orientation vector of the respective sample as the center orientation value of the selected filter.
5. The method of claim 1 , wherein the orientation vectors are determined by:
comparing response values associated with each sample for different optical filters of the set of optical filters;
determining a maximum response value for each sample;
selecting the optical filter corresponding to the maximum response value; and
setting the orientation vector of the respective sample as the center orientation value of the selected filter.
6. The method of claim 1 , wherein the set of optical filters comprises a set of matrices of numbers.
7. The method of claim 1 , wherein convolving comprises:
converting the seismic section from a spatial domain to a frequency domain using a Fourier transform;
convolving the set of optical filters with the converted seismic section in the frequency domain; and
converting response values from the convolving from the frequency domain to the spatial domain using an inverse Fourier transform.
8. The method of claim 1 , wherein convolving comprises obtaining an angle and a convolution energy as a response for each filter and sample combination of the seismic section and wherein determining comprises selecting the filter corresponding to the highest convolution energy.
9. The method of claim 1 , wherein determining comprises selecting, for each sample, the optical filter corresponding to the maximum response value and setting the center orientation value of the selected filter as the orientation of the orientation vector for the respective x and y coordinate.
10. The method of claim 2 , wherein the modified Log-Gabor filters are modified by replacing filters at different scales by a radial direction step function.
11. A non-transitory computer-readable medium having instructions stored thereon that, when operated on by the computer, cause the computer to perform operations comprising:
convolving a set of optical filters with a seismic section to obtain a set of responses, the seismic section comprising a plurality of samples, wherein each sample is referenced using the variable x and y as the coordinates of the sample in the seismic section, wherein, for each sample, there are corresponding response values associated with the x and y coordinates of the sample, the optical filters having various center orientation values;
determining an orientation vector for each sample based on the response value associated with the x and y coordinates of the sample;
creating an orientation vector field comprising the orientation vectors of all the samples and storing the orientation vector field; and
using the orientation vector field to determine a horizon in the two-dimensional seismic section by following the orientation vectors of the samples, beginning with the initial pick point on the horizon.
12. The medium of claim 11 , wherein the optical filters are modified Log-Gabor filters.
13. The medium of claim 11 , wherein the orientation vector for each sample is determined based on the maximum response value associated with the sample.
14. The medium of claim 11 , wherein the orientation vectors are determined by:
comparing response values associated with each sample for different optical filters of the set of optical filters;
determining a maximum response value for each sample;
selecting the optical filter corresponding to the maximum response value; and setting the orientation vector of the respective sample as the center orientation value of the selected filter.
15. The medium of claim 11 , wherein convolving comprises:
converting the seismic section from a spatial domain to a frequency domain using a Fourier transform;
convolving the set of optical filters with the converted seismic section in the frequency domain; and
converting response values from the convolving from the frequency domain to the spatial domain using an inverse Fourier transform.
16. The medium of claim 11 , wherein convolving comprises obtaining an angle and a convolution energy as a response for each filter and sample combination of the seismic section and wherein determining comprises selecting the filter corresponding to the highest convolution energy.
17. The medium of claim 11 , wherein determining comprises selecting, for each sample, the optical filter corresponding to the maximum response value and setting the center orientation value of the selected filter as the orientation of the orientation vector for the respective x and y coordinate.
18. The medium of claim 12 , wherein the modified Log-Gabor filters are modified by replacing filters at different scales by a radial direction step function.