Method and system for determining gamma-ray measurements using a sensitivity map and controlled sampling motion

1. A method, comprising:

obtaining, by a computer processor and using a gamma-ray sensing system comprising a gamma-ray detector and a sensing region, first acquired gamma-ray data regarding a first core sample,

wherein the first core sample is analyzed by the gamma-ray sensing system at a plurality of periodic intervals in the sensing region using a controlled sampling motion comprising a plurality of sensor steps, and

wherein a respective sensor step among the plurality of sensor steps defines a predetermined change in distance of the first core sample in the sensing region with respect to the gamma-ray detector;

determining, by the computer processor, a sensitivity map based on the first acquired gamma-ray data and comprising a plurality of weighted coefficients, wherein a respective weighted coefficient among the plurality of weighted coefficients correspond to the respective sensor step;

obtaining, by the computer processor and using the gamma-ray detector, second acquired gamma-ray data regarding a second core sample at the plurality of sensor steps wherein the respective weighted coefficient determines a filtered gamma-ray signal for a portion of the second acquired gamma-ray data at the respective sensor step; and

generating, by the computer processor, a gamma-ray log using the sensitivity map and a gamma-ray inversion process.

2. The method of claim 1 , further comprising:

determining one or more geological properties for a geological region of interest using the gamma-ray log,

wherein the geological region of interest corresponds to a predetermined formation, and

wherein the second core sample is acquired from a well in the predetermined formation.

3. The method of claim 2 ,

wherein the one or more geological properties corresponds to an amount of shale content in the geological region of interest.

4. The method of claim 1 , further comprising:

obtaining a nonlinear solver that performs an iterative reweighted least squares (IRLS) operation,

wherein the gamma-ray inversion process uses the nonlinear solver to minimize a predetermined misfit function.

5. The method of claim 1 ,

wherein the first core sample is a baseline core sample.

6. The method of claim 1 ,

wherein the gamma-ray detector is moved at the plurality of sensor steps along a first axis of the first core sample, and

wherein the first core sample is longer with respect to the first axis than a second axis that is perpendicular to the first axis.

7. The method of claim 1 ,

wherein the second core sample is acquired from a well in a coring operation using a core bit, a core barrel, and a core catcher.

8. The method of claim 1 ,

wherein the gamma-ray detector is a passive detector in a gamma-ray system without an active gamma-ray source.

9. A system, comprising:

a gamma-ray detector configured to detect a plurality of gamma rays from a sensing region; and

a host device comprising a computer processor, wherein the host device is coupled to the gamma-ray detector, the host device being configured to perform a method comprising:

obtaining, using the gamma-ray detector, first acquired gamma-ray data regarding a first core sample,

wherein the first core sample is analyzed at a plurality of periodic intervals in the sensing region using a controlled sampling motion comprising a plurality of sensor steps, and

wherein a respective sensor step among the plurality of sensor steps defines a predetermined change in distance of the first core sample in the sensing region with respect to the gamma-ray detector;

determining a sensitivity map based on the first acquired gamma-ray data and comprising a plurality of weighted coefficients, wherein a respective weighted coefficient among the plurality of weighted coefficients correspond to the respective sensor step;

obtaining, using the gamma-ray detector, second acquired gamma-ray data regarding a second core sample at the plurality of sensor steps, wherein the respective weighted coefficient determines a filtered gamma-ray signal for a portion of the second acquired gamma-ray data at the respective sensor step; and

generating a gamma-ray log using the sensitivity map and a gamma-ray inversion process.

10. The system of claim 9 , wherein the host device further comprises functionality for:

determining one or more geological properties for a geological region of interest using the gamma-ray log,

wherein the geological region of interest corresponds to a predetermined formation, and

wherein the second core sample is acquired from a well in the predetermined formation.

11. The system of claim 9 , wherein the host device further comprises functionality for:

obtaining a nonlinear solver that performs an iterative reweighted least squares (IRLS) operation,

wherein the gamma-ray inversion process uses the nonlinear solver to minimize a predetermined misfit function.

12. The system of claim 9 ,

wherein the gamma-ray detector is moved at the plurality of sensor steps along a first axis of the first core sample, and

wherein the first core sample is longer with respect to the first axis than a second axis that is perpendicular to the first axis.

13. The system of claim 9 , further comprising:

a logging system coupled to a wellbore, wherein the logging system comprises a coring tool,

wherein the second core sample is acquired from a well in a coring operation using the coring tool.

14. The system of claim 9 ,

wherein the gamma-ray detector is a passive detector in a gamma-ray system without an active gamma-ray source.

15. A non-transitory computer readable medium storing instructions executable by a computer processor, the instructions comprising functionality for:

obtaining, from a gamma-ray sensing system comprising a gamma-ray detector and a sensing region, first acquired gamma-ray data regarding a first core sample,

wherein the first core sample is analyzed by the gamma-ray sensing system at a plurality of periodic intervals in the sensing region using a controlled sampling motion comprising a plurality of sensor steps, and

wherein a respective sensor step among the plurality of sensor steps defines a predetermined change in distance of the first core sample in the sensing region with respect to the gamma-ray detector;

determining a sensitivity map based on the first acquired gamma-ray data and comprising a plurality of weighted coefficients, wherein a respective weighted coefficient among the plurality of weighted coefficients correspond to the respective sensor step;

obtaining, from the gamma-ray detector, second acquired gamma-ray data regarding a second core sample at the plurality of sensor steps, wherein the respective weighted coefficient determines a filtered gamma-ray signal for a portion of the second acquired gamma-ray data at the respective sensor step; and

generating a gamma-ray log using the sensitivity map and a gamma-ray inversion process.

16. The non-transitory computer readable medium of claim 15 , the instructions further comprising functionality for:

determining one or more geological properties for a geological region of interest using the gamma-ray log,

wherein the geological region of interest corresponds to a predetermined formation, and

wherein the second core sample is acquired from a well in the predetermined formation.

17. The non-transitory computer readable medium of claim 15 , the instructions further comprising functionality for:

obtaining a nonlinear solver that performs an iterative reweighted least squares (IRLS) operation,

wherein the gamma-ray inversion process uses the nonlinear solver to minimize a predetermined misfit function.