Integrated collar sensor for measuring mechanical impedance of the downhole tool

1. A downhole tool comprising:

a collar; and

one or more sensors secured to the collar for measuring one or more operational characteristics of the downhole tool including a mechanical impedance during operation of the downhole tool, the one or more sensors including a first sensor including:

a first substrate;

a plurality of strain gauges integrated into the first substrate and configured to measure axial strains and torsional strains on the collar that are transferred to the first substrate for measuring the one or more operational characteristics including the mechanical impedance of the downhole tool;

a printed circuit board (PCB) positioned within the first sensor in proximity to the first substrate and the plurality of strain gauges integrated into the first substrate; and

a temperature sensor included in the PCB in proximity to the plurality of strain gauges and configured to measure temperature at the plurality of strain gauges,

wherein the plurality of strain gauges are configured and controlled based at least in part on the temperature at the plurality of strain gauges.

2. The downhole tool of claim 1 , wherein the mechanical impedance is indicative of one or more formation parameters of a medium in which the downhole tool is operating.

3. The downhole tool of claim 2 , wherein the one or more formation parameters include one or a combination of a compressive strength of the medium, a porosity of the medium, a shear strength of the medium, and a modulus of elasticity of the medium.

4. The downhole tool of claim 2 , wherein the one or more operational characteristics of the downhole tool include weight-on-bit and torque-on-bit of the downhole tool and the weight-on-bit and the torque-on-bit of the downhole tool are determined from the axial strains and the torsional strains on the collar measured by the plurality of strain gauges, and either or both the weight-on-bit and the torque-on-bit of the downhole tool are indicative of the one or more formation parameters of the medium.

5. The downhole tool of claim 4 , wherein a change in either or both the weight-on-bit and the torque-on-bit of the downhole tool are indicative of the one or more formation parameters of the medium.

6. The downhole tool of claim 2 , wherein the one or more operational characteristics of the downhole tool include a rate of penetration of the downhole tool and the rate of penetration of the downhole tool is indicative of the one or more formation parameters of the medium.

7. The downhole tool of claim 6 , wherein a change in the rate of penetration of the downhole tool is indicative of the one or more formation parameters of the medium.

8. The downhole tool of claim 1 , wherein the PCB includes electronics for controlling operation of the first sensor in measuring the one or more operational characteristics of the downhole tool.

9. The downhole tool of claim 8 , wherein the first sensor is calibrated by concurrently calibrating the electronics of the PCB and the plurality of strain gauges.

10. The downhole tool of claim 8 , wherein a position of the PCB in proximity to the first substrate and the plurality of strain gauges within the first sensor reduces an amount of signal noise in signals transmitted between the PCB and the plurality of strain gauges.

11. The downhole tool of claim 1 , wherein the plurality of strain gauges includes eight strain gauges integrated into the first substrate and circumferentially spaced apart at 45°+ or − a range of 10° and thereby forming two full-bridge strain sensors within the first sensor.

12. The downhole tool of claim 1 , further comprising:

one or more additional sensors including at least a second sensor secured to the collar for measuring the one or more operational characteristics of the downhole tool during operation of the downhole tool, the second sensor including:

a second sensor substrate; and

a second plurality of strain gauges integrated into the second sensor substrate and configured to measure the axial strains and torsional strains on the collar for measuring the one or more operational characteristics of the downhole tool.

13. The downhole tool of claim 12 , wherein the first sensor and the second sensor are secured at opposing positions along a circumference of the collar separated by 180° around the circumference of the collar.

14. A sensor of a downhole tool comprising:

a substrate configured for positioning on a collar of the downhole tool;

a plurality of strain gauges integrated into the substrate and configured to measure axial strains and torsional strains on the collar that are transferred to the substrate for measuring one or more operational characteristics including a mechanical impedance of the downhole tool;

a printed circuit board (PCB) positioned within the sensor in proximity to the substrate and the plurality of strain gauges integrated into the substrate; and

a temperature sensor included in the PCB in proximity to the plurality of strain gauges and configured to measure temperature at the plurality of strain gauges,

wherein the plurality of strain gauges are configured and controlled based at least in part on the temperature at the plurality of strain gauges.

15. The sensor of claim 14 , wherein the mechanical impedance is indicative of one or more formation parameters of a medium in which the downhole tool is operating.

16. The sensor of claim 15 , wherein the one or more formation parameters include one or a combination of a compressive strength of the medium, a porosity of the medium, a shear strength of the medium, and a modulus of elasticity of the medium.

17. The sensor of claim 15 , wherein the one or more operational characteristics of the downhole tool include weight-on-bit and torque-on-bit of the downhole tool and the weight-on-bit and the torque-on-bit of the downhole tool are determined from the axial strains and the torsional strains on the collar measured by the plurality of strain gauges, and either or both the weight-on-bit and the torque-on-bit of the downhole tool are indicative of the one or more formation parameters of the medium.

18. The sensor of claim 15 , wherein the one or more operational characteristics of the downhole tool include a rate of penetration of the downhole tool and the rate of penetration of the downhole tool is indicative of the one or more formation parameters of the medium.

19. A method for fabricating a sensor for a downhole tool comprising:

installing a plurality of strain gauges on a single substrate of the sensor, wherein the sensor is configured to measure axial strains and torsional strains on a collar when the sensor is secured to the collar for measuring one or more operational characteristics including a mechanical impedance of the downhole tool;

coupling the substrate to a metal support structure;

attaching wires to the substrate coupled to the metal support structure for providing electrical connections to the plurality of strain gauges;

connecting a printed circuit board (PCB) including electronics for controlling operation of the sensor in measuring the one or more operational characteristics of the downhole tool to the wires, and a temperature sensor in proximity to the plurality of strain gauges and configured to measure temperature at the plurality of strain gages, wherein the plurality of strain gauges are configured and controlled based at least in part on the temperature at the plurality of strain gauges;

physically connecting the PCB to the substrate; and

concurrently calibrating the electronics and the plurality of strain gauges as part of calibrating the sensor.