Bit based formation evaluation using a gamma ray sensor

1. A drill bit, comprising:

a bit body including a cone having a cutter and a shank having a neck section; and

a gamma ray sensor that is one of embedded in the cone and within a shank of the bit body outside the neck section, the gamma ray sensor configured to detect naturally occurring gamma rays from a formation being drilled.

2. The drill bit of claim 1 , wherein the gamma ray sensor is embedded into the cutter.

3. The drill bit of claim 1 , wherein the gamma ray sensor is positioned in one of: (i) the shank, (ii) on a blade profile and (iii) proximate the cutter.

4. The drill bit of claim 1 , wherein the gamma ray sensor is configured to detect one of: (i) potassium, (ii) uranium and (iii) thorium.

5. The drill bit of claim 1 , further comprising a communication link configured to provide data communication between a remote device and the gamma ray sensor.

6. The drill bit of claim 1 further comprising a circuit in the bit body configured to at least partially process signals from the gamma ray sensor.

7. A method of making a drill bit, comprising:

embedding in a bit body of the drill bit a gamma ray sensor configured to provide signals representative of a naturally occurring gamma ray source in a formation being drilled, wherein the bit body includes a cone having a cutter and a shank having a neck section, and wherein the gamma ray sensor is one of embedded in the cone and within the shank of the bit body outside the neck section.

8. The method of claim 7 further comprising placing a circuit in the drill bit configured to process signals from the gamma ray sensor.

9. A drilling system for use in drilling a wellbore in an earth formation, comprising:

a drill string;

a drill bit having a bit body positioned at an end of the drill string, wherein the bit body includes a cone having a cutter and a shank having a neck section;

a gamma ray sensor that is one of integrated in the cone and within the shank of the bit body outside the neck section, the gamma ray sensor configured to provide signals representative of one or more naturally occurring gamma ray sources in a formation being drilled; and

a processor configured to receive data from the gamma ray sensor and estimate a desired parameter of interest relating to the formation being drilled.

10. The drilling system of claim 9 wherein the desired parameter of interest is a lithology of the formation.

11. The drilling system of claim 9 wherein the desired parameter of interest is a bed boundary.

12. The drilling system of claim 9 , wherein at least a portion of the processor is placed in the drill bit.

13. A method for drilling a wellbore in an earth formation, comprising:

drilling the wellbore with a drill bit having a gamma ray sensor embedded in a bit body, wherein the bit body includes a cone having a cutter and a shank having a neck section, and wherein the gamma ray sensor is one of embedded in the cone and within the shank of the bit body outside the neck section; and

detecting one or more naturally occurring gamma ray sources in a formation being drilled using the gamma ray sensor.

14. The method of claim 13 further comprising processing signals from the gamma ray sensor.

15. The method of claim 14 further comprising estimating a location of a bed boundary by processing the signals.

16. The method of claim 14 further comprising estimating a lithology of a formation being drilled by processing the signals.

17. The method of claim 14 further comprising adjusting drilling parameter after processing the signals.

18. The method of claim 17 wherein the drilling parameter includes one of: (i) weight-on-bit, and (ii) RPM of the drill bit.

19. The method of claim 14 further comprising changing a direction of drilling after processing the signals.