Method for calibrating seismic imaging velocities
View Patent ↗A method for adjusting an isotropic depth image based on a mis-tie volume is provided. The method generally includes obtaining an isotropic velocity volume for a geophysical volume, obtaining an isotropic depth image of the geophysical volume, obtaining time-depth pairs at downhole locations in the geophysical volume, generating mis-tie values based on the time-depth pairs and the isotropic velocity volume, assigning uncertainties to the mis-tie values, generating a smoothest mis-tie volume that satisfies a target goodness of fit with the mis-tie values. Adjustment of the isotropic depth image may be achieved based on the mis-tie volume or a calibration velocity obtained from the mis-tie volume.
1. A method, comprising:
obtaining an isotropic velocity volume for a geophysical volume;
obtaining time-depth pairs at downhole locations in the geophysical volume, the time-depth pairs corresponding to one or more wells located in the geophysical volume and comprising data indicative of at least one seismic survey;
generating, using a computer, depth mis-tie values based on the time-depth pairs and an isotropic depth image of the geophysical volume, the depth mis-tie values being computed according to the expression:
m ( x,y,t )= z iso ( x,y,t )− z ( x,y,t )
where z iso (x,y,t) is an isotropic depth based on the isotropic depth image, z(x,y,t) is a depth, and m(x,y,t) is a depth mis-tie;
assigning uncertainties to the depth mis-tie values; and
generating a mis-tie volume that satisfies a target goodness of fit with the depth mis-tie values.
2. The method of claim 1 , further comprising:
obtaining an isotropic depth image of the geophysical volume; and
adjusting the isotropic depth image using the mis-tie volume.
3. The method of claim 2 , wherein the adjusting the isotropic depth image further comprises:
obtaining a calibration velocity from the mis-tie volume.
4. The method of claim 3 , further comprising:
differentiating the mis-tie volume to obtain the calibration velocity.
5. The method of claim 1 , further comprising:
obtaining a calibration velocity from the mis-tie volume.
6. The method of claim 5 , wherein the calibration velocity is an estimate of the velocity of vertically propagating waves in the geophysical volume.
7. The method of claim 5 , further comprising:
obtaining an isotropic depth image of the geophysical volume;
generating a time image from the isotropic depth image; and
generating a depth image from the time image.
8. The method of claim 5 , further comprising:
generating a time image; and
generating a depth image from the time image.
9. The method of claim 8 , wherein the depth image is substantially equivalent to an adjusted isotropic image from the mis-tie volume.
10. A method, comprising:
obtaining an isotropic velocity volume for a geophysical volume utilizing data indicative of at least one seismic survey;
obtaining, using a computer, an isotropic depth image of the geophysical volume;
obtaining time-depth pairs at downhole locations in the geophysical volume, the time-depth pairs corresponding to one or more wells located in the geophysical volume based on the data indicative of the at least one measurement;
generating, using a computer, depth mis-tie values based on the time-depth pairs and an isotropic depth image of the geophysical volume, the depth mis-tie values being computed according to the expression:
m ( x,y,t )= z iso ( x,y,t )− z ( x,y,t )
where z iso (x,y,t) is an isotropic depth based on the isotropic depth image, z(x,y,t) is a depth, and m(x,y,t) is a depth mis-tie;
assigning uncertainties to the depth mis-tie values;
generating a smoothest mis-tie volume that satisfies a target goodness of fit with the depth mis-tie values;
obtaining a calibration velocity from the mis-tie volume;
generating a time image from the isotropic depth image; and
generating a depth image from the time image using the calibration velocity.
11. The method of claim 10 , wherein the calibration velocity is an estimate of the velocity of vertically propagating waves in the geophysical volume.
12. The method of claim 10 , wherein obtaining the calibration velocity further comprises:
differentiating the mis-tie volume.
13. The method of claim 10 , further comprising:
adjusting the isotropic depth image from the mis-tie volume.
14. The method of claim 13 , wherein the depth image is substantially equivalent to the adjusted isotropic image from the mis-tie volume.
15. A method, comprising:
obtaining an isotropic velocity volume for a geophysical volume using data indicative of at least one seismic survey;
obtaining, using a computer, an isotropic depth image of the geophysical volume;
obtaining, using a computer, depth mis-tie values by identifying isotropic depth images with known true depths measured at one or more wells, the depth mis-tie values being computed according to the expression:
m ( x,y,t )= z iso ( x,y,t )− z ( x,y,t )
where z iso (x,y,t) is an isotropic depth based on the isotropic depth image, z(x,y,t) is a depth, and m(x,y,t) is a depth mis-tie;
assigning uncertainties to the depth mis-tie values;
generating a smoothest mis-tie volume that satisfies a target goodness of fit with the depth mis-tie values; and
obtaining an estimate of a velocity normal to structure by taking the directional derivative with respect to time, in the direction normal to structure, of the mis-tie volume.
16. The method of claim 15 , wherein the obtaining depth mis-tie values is based on the known true depths and the isotropic velocity volume.
17. The method of claim 15 , further comprising:
adjusting the isotropic depth image using the mis-tie volume.
18. The method of claim 15 , further comprising:
generating a time image from the isotropic depth images.
19. The method of claim 18 , further comprising:
generating a depth image from the time image.
20. The method of claim 19 , wherein the depth image is substantially equivalent to an adjusted isotropic depth image from the mis-tie volume.
21. The method of claim 1 or 10 , wherein each depth mis-tie value is indicative of a deviation of a depth from a corresponding isotropic depth.
22. The method of claim 21 , wherein the isotropic depth is determined based on an isotropic velocity analysis.
23. The method of claim 21 , wherein each depth mis-tie value is indicative of a difference between the depth and the corresponding isotropic depth.
24. A method, comprising:
obtaining an isotropic velocity volume for a geophysical volume;
obtaining an isotropic depth image of the geophysical volume;
obtaining time-depth pairs at downhole locations in the geophysical volume, the time-depth pairs corresponding to one or more wells located in the geophysical volume and comprising data indicative of at least one seismic survey;
generating, using a computer, depth mis-tie values based on the time-depth pairs and the isotropic depth image, the depth mis-tie values being computed according to the expression:
m ( x,y,t )= z iso ( x,y,t )− z ( x,y,t )
where z iso (x, y, t) is an isotropic depth based on the isotropic depth image, z(x, y, t) is a depth, and m(x, y, t) is a depth mis-tie;
assigning uncertainties to the depth mis-tie values;
minimizing an objective function using a computer, the objective function being based on the depth mis-tie values and the uncertainties; and
based on the minimized objective function, generating a mis-tie volume that satisfies a target goodness of fit with the depth mis-tie values.