Temperature correction of magnetic resonance data

1. An apparatus for estimating properties of an earth formation, the apparatus comprising:

a carrier configured to be deployed in a borehole in the earth formation;

a nuclear magnetic resonance (NMR) measurement device including a magnet assembly configured to generate a static magnetic field in the formation, at least one transmitting assembly configured to generate an oscillating magnetic field in the formation, and a receiver configured to detect NMR signals from at least a sensitive volume in the formation; and

a processing device configured to receive NMR data corresponding to the detected NMR signals, the processing device configured to perform:

combining a distribution of signal contribution of the NMR logging tool with a temperature distribution, the temperature distribution indicating a temperature value at at least one location in the sensitive volume of the formation;

correcting the NMR data based on the temperature value, and estimating a property of the formation based on the corrected NMR data; and

performing one or more aspects of an energy industry operation based on the estimated property.

2. The apparatus of claim 1 , wherein the distribution of signal contribution is a three-dimensional or two-dimensional distribution of signal contribution.

3. The apparatus of claim 1 , wherein the distribution of signal contribution is a radial distribution of signal contribution.

4. The apparatus of claim 1 , wherein the temperature distribution is a three-dimensional or a two-dimensional distribution.

5. The apparatus of claim 1 , wherein the temperature distribution is a one-dimensional distribution.

6. The apparatus of claim 1 , wherein combining includes multiplying the temperature distribution by the distribution of signal contribution.

7. The apparatus of claim 1 , wherein combining includes calculating an integrated radial distribution of signal contribution.

8. The apparatus of claim 1 , wherein correcting includes multiplying the NMR data by a correction value derived from the temperature value to estimate a porosity value at one or more locations in the sensitive volume.

9. The apparatus of claim 1 , wherein correcting the NMR data includes calculating a centroid of an area or volume defined by the distribution of signal contribution, the temperature value corresponding to a value of the temperature distribution at a location in the sensitive volume corresponding to the centroid.

10. The apparatus of claim 9 , wherein correcting includes estimating a temperature corrected porosity φ MT based on the following equation:

φ

MT

=

φ

M

·

T

⁡

(

r

c

)

T

M

,

,

wherein φ M is a porosity value estimated by calibrating the NMR data based on a measured temperature of borehole fluid, T M is the measured temperature, and T(r c ) is a value of the temperature distribution at a radial location r c that corresponds to the centroid of the distribution of signal contribution.

11. A method of estimating properties of an earth formation, the method comprising:

disposing a nuclear magnetic resonance (NMR) measurement device in a borehole in the earth formation, the NMR measurement device including a magnet assembly configured to generate a static magnetic field in the formation, at least one transmitting assembly configured to generate an oscillating magnetic field in the formation, and a receiver configured to detect NMR signals from at least a sensitive volume in the formation;

receiving NMR data corresponding to the detected NMR signals by a processing device;

combining a distribution of signal contribution of the NMR logging tool with a temperature distribution, the temperature distribution indicating a temperature value at at least one location in the sensitive volume of the formation;

correcting the NMR data based on the temperature value, and estimating a property of the formation based on the corrected NMR data; and

performing one or more aspects of an energy industry operation based on the estimated property.

12. The method of claim 11 , wherein the distribution of signal contribution is a three-dimensional or two-dimensional distribution of signal contribution.

13. The method of claim 11 , wherein the distribution of signal contribution is a radial distribution of signal contribution.

14. The method of claim 11 , wherein the temperature distribution is a three-dimensional or a two-dimensional distribution.

15. The method of claim 11 , wherein the temperature distribution is a one-dimensional distribution.

16. The method of claim 11 , wherein combining includes multiplying the temperature distribution by the distribution of signal contribution.

17. The method of claim 11 , wherein combining includes calculating an integrated radial distribution of signal contribution.

18. The method of claim 11 , wherein correcting includes multiplying the NMR data by a correction value derived from the temperature value to estimate a porosity value at one or more locations in the sensitive volume.

19. The method of claim 11 , wherein correcting the NMR data includes calculating a centroid of an area or volume defined by the distribution of signal contribution, the temperature value corresponding to a value of the temperature distribution at a location in the sensitive volume corresponding to the centroid.

20. The method of claim 19 , wherein correcting includes estimating a temperature corrected porosity φ MT based on the following equation:

φ

MT

=

φ

M

·

T

⁡

(

r

c

)

T

M

,

,

wherein φ M is a porosity value estimated by calibrating the NMR data based on a measured temperature of borehole fluid, T M is the measured temperature, and T(r c ) is a value of the temperature distribution at the radial location r c that corresponds to the centroid of the distribution of signal contribution.