DETERMINING GRAVITY TOOLFACE AND INCLINATION IN A ROTATING DOWNHOLE TOOL

• US 20150330210A1
• Filed: 12/27/2012
• Published: 11/19/2015
• Est. Priority Date: 12/27/2012
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Lozinsky, Clint P.
• Granted Patent: US 10,539,005 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: E21B 47/024 of devices in the borehole determining slope or direction of the borehole E21B47/022

Abstract

Systems and methods for determining gravity toolface and inclination are described herein. An example may comprise a downhole tool (300) and a sensor assembly (330, 340, 350) disposed in a radially offset location within the downhole tool. The sensor assembly may comprise three accelerometers and an angular rate sensing device. A processor (402a) may be in communication with the sensor assembly and may be coupled to at least one memory device (402b). The memory device may contain a set of instruction that, when executed by the processor, cause the processor to receive an output from the sensor assembly; determine at least one of a centripetal acceleration (r) and a tangential acceleration (a) of the downhole tool based, at least in part, on the output; and determine at least one of a gravity toolface and inclination of the downhole tool using at least one of the centripetal acceleration and the tangential acceleration.

Claims

1. A system for determining gravity toolface and inclination, comprising:

a downhole tool;

a sensor assembly disposed in a radially offset location within the downhole tool, wherein the sensor assembly comprises three accelerometers and an angular rate sensing device;

a processor in communication with the sensor assembly, wherein the processor is coupled to at least one memory device containing a set of instruction that, when executed by the processor, cause the processor to

receive an output from the sensor assembly;

determine at least one of a centripetal acceleration and a tangential acceleration of the downhole tool based, at least in part, on the output; and

determine at least one of a gravity toolface and inclination of the downhole tool using at least one of the centripetal acceleration and the tangential acceleration.

2. The system of claim 1, wherein the three accelerometers comprise:

a first accelerometer oriented to sense a first component in a first direction within a plane;

a second accelerometer oriented to sense a second component in a second direction within the plane, wherein the second direction is perpendicular to the first direction; and

a third accelerometer oriented to sense a third component in a third direction perpendicular to the plane.

3. The system of claim 2, wherein the angular rate sensing device comprises a gyroscope.

4. The system of claim 1, wherein:

the centripetal acceleration is determined using the following equation;

r=ω

² * radius,

where r corresponds to the centripetal acceleration, ω

corresponds to an angular speed output of the angular rate sensing device, and radius corresponds to a radial distance of the angular rate sensing device from a longitudinal axis of the downhole tool; and

the tangential acceleration is determined using the following equation;

a=((ω

₂−

ω

₁)/(t₂−

t₁)) * radius

where a corresponds to the tangential acceleration, ω

₂ corresponds to an angular speed output of the angular rate sensing device at time t₂, ω

₁ corresponds to an angular speed output of the angular rate sensing device at time t₁, and radius corresponds to a radius of the downhole tool.

5. The system of claim 4, wherein the gravity toolface Θ

is determined using at least one of the following equations;

x=(g*sinΘ

)+a;

y=(−

g*cosΘ

)−

r;

with x corresponding to the sensed first component from the first accelerometer, y corresponding to the sensed second component from the second accelerometer;

g corresponding to the force of gravity, a corresponding to the tangential acceleration, and r corresponding to the centripetal acceleration.

6. The system of claim 1, wherein the output comprises:

the sensed first component from the first accelerometer;

the sensed second component from the second accelerometer;

the sensed third component from the third accelerometer; and

an angular speed from the angular rate sensing device.

7. The system of claim 1, wherein the sensor assembly is implemented on a single printed circuit board (PCB).

8. The system of claim 7, wherein the angular rate sensing device comprises a gyroscope implemented in a single integrated circuit chip coupled to the PCB.

9. A system for determining gravity toolface and inclination, comprising:

a downhole tool;

a first sensor assembly disposed in a first radially offset location within the downhole tool, wherein the first sensor assembly comprises a first accelerometer and a second accelerometer;

a second sensor assembly disposed in a second radially offset location within the downhole tool, wherein the second sensor assembly comprises a third accelerometer and a fourth accelerometer;

a processor in communication with the first sensor assembly and the second sensor assembly, wherein the processor is coupled to at least one memory device containing a set of instruction that, when executed by the processor, cause the processor to

receive a first output from the first sensor assembly and a second output from the second sensor assembly;

determine at least one of a centripetal acceleration and a tangential acceleration of the downhole tool based, at least in part, on the first output and the second output; and

determine at least one of a gravity toolface and inclination of the downhole tool using at least one of the centripetal acceleration and the tangential acceleration.

10. The system of claim 9, wherein:

the first accelerometer is oriented to sense a first component in a first direction within a plane;

the second accelerometer is oriented to sense a second component in a second direction within the plane, wherein the second direction is perpendicular to the first direction;

the third accelerometer is oriented to sense a third component in a third direction within the plane, wherein the third direction is opposite the first direction;

the fourth accelerometer is oriented to sense a fourth component in a fourth direction within the plane, wherein the fourth direction is perpendicular to the third direction and opposite the fourth direction.

11. The system of claim 10, wherein:

the centripetal acceleration is determined using the following equation;

r=−

(y+y2)/2

where r corresponds to the centripetal acceleration, y corresponds to a second sensed component from the second accelerometer, and y2 corresponds to the fourth sensed component from the fourth accelerometer; and

the tangential acceleration is determined using the following equation;

a=(x+x2)/2

where a corresponds to the tangential acceleration, x corresponds to a first sensed component from the first accelerometer, and x2 corresponds to the third sensed component from the third accelerometer.

12. The system of claim 11, wherein the gravity toolface Θ

is determined using at least one of the following equations;

x=(g*sinΘ

)+a;

x2=(−

g*sinΘ

)+a;

y=(−

g*cosΘ

)−

r;

y2=(g*cosΘ

)−

r

with x corresponding to a first sensed component from the first accelerometer, x2 corresponding to the third sensed component from the third accelerometer, y corresponding to a second sensed component from the second accelerometer, y2 corresponding to the fourth sensed component from the fourth accelerometer;

g corresponding to the force of gravity, a corresponding to the tangential acceleration, and r corresponding to the centripetal acceleration.

13. The system of claim 9, wherein the output comprises:

the sensed first component from the first accelerometer;

the sensed second component from the second accelerometer;

the sensed third component from the third accelerometer; and

the sensed fourth component from the fourth accelerometer.

14. The system of claim 9, wherein the first sensor assembly is implemented on a first printed circuit board (PCB) and the second sensor assembly is implemented on a second PCB.

15. The system of claim 9, wherein the first radially offset location is diametrically opposite the second radially offset location.

16. A method for determining gravity toolface and inclination, comprising:

positioning a downhole tool within a borehole, wherein;

the downhole tool comprises a sensor assembly disposed in a radially offset location within the downhole tool; and

the sensor assembly comprises at least two accelerometers and an angular rate sensing device;

determining at least one of a centripetal acceleration and a tangential acceleration of the downhole tool based, at least in part, on an output of the sensor assembly; and

determining at least one of a gravity toolface and an inclination of the downhole tool using at least one of the centripetal acceleration and the tangential acceleration.

17. The method of claim 16, further comprising altering a steering assembly based, at least in part, on at least one of the gravity toolface and the inclination of the downhole tool.

18. The method of claim 16, wherein the three accelerometers comprise:

a first accelerometer oriented to sense a first component in a first direction within a plane; and

a second accelerometer oriented to sense a second component in a second direction within the plane, wherein the second direction is perpendicular to the first direction.

19. The method of claim 18, further comprising a third accelerometer oriented to sense a third component in a third direction perpendicular to the plane.

20. The method of claim 18, wherein:

the centripetal acceleration is determined using the following equation;

r=ω

² * radius,

where r corresponds to the centripetal acceleration, ω

corresponds to an angular speed output of the angular rate sensing device, and radius corresponds to a radial distance of the angular rate sensing device from a longitudinal axis of the downhole tool;

the tangential acceleration is determined using the following equation;

a=((ω

₂−

ω

₁)/(t₂−

t₁)) * radius

where a corresponds to the tangential acceleration, ω

₂ corresponds to an angular speed output of the angular rate sensing device at time t₂, ω

₁ corresponds to an angular speed output of the angular rate sensing device at time t₁, and radius corresponds to a radius of the downhole tool; and

the gravity toolface Θ

is determined using at least one of the following equations;

x=(g*sinΘ

)+a;

y=(−

g*cosΘ

)−

r;

with x corresponding to the sensed first component from the first accelerometer, y corresponding to the sensed second component from the second accelerometer;

g corresponding to the force of gravity, a corresponding to the tangential acceleration, and r corresponding to the centripetal acceleration.