Method and apparatus for enhancing directional accuracy and control using bottomhole assembly bending measurements
A system for drilling a well comprises a tubular member having a bottomhole assembly at a bottom end thereof disposed in a wellbore. A first sensor is disposed in the bottomhole assembly at a predetermined axial location for detecting bending in a first axis and generating a first bending signal in response thereto, where the first axis is substantially orthogonal to a longitudinal axis of the bottomhole assembly. A second sensor is disposed in the bottomhole assembly at the predetermined axial location for detecting bending in a second axis and generating a second bending signal in response thereto, where the second axis is substantially orthogonal to the longitudinal axis. A processor receives the first bending signal and the second bending signal and relates the first bending signal and the second bending signal to a borehole curvature according to programmed instructions.
1. A method for drilling a wellbore, comprising:
extending a bottomhole assembly into the wellbore;
measuring a bending moment M at at least one axial location along the bottomhole assembly; and
estimating a dog leg severity of the wellbore using
δ=( k×M )/( E×I ),
where M is the measured bending moment, E is the Young's modulus for the bottomhole assembly, I is the moment of inertia of the bottomhole assembly, and k is a conversion factor.
2. The method of claim 1 further comprising controlling the dog leg severity of the wellhole according to a predetermined target value.
3. The method of claim 1 further comprising controlling the bending moment measurements at a target magnitudes and orientation of the bottomhole assembly to drill the wellhole along a target path.
4. The method of claim 1 further comprising estimating a curvature of the wellbore at a drill bit disposed at the bottom of the bottomhole assembly using bending moment measurement and a directional measurement at a location along the bottomhole assembly spaced apart from the drill bit.
5. The method of claim 1 , wherein measuring the bending moments comprises measuring the bending moment in two substantially orthogonal directions at the same axial location of the bottomhole assembly.
6. The method of claim 1 further comprising transmitting the bending moment measurement to a surface location for processing.
7. The method of claim 1 further comprising at least partially processing the bending moment measurement downhole.
8. The method of claim 1 further comprising estimating a bottomhole assembly misalignment in the wellbore at a directional measurement location using the bending moment measurement.
9. The method of claim 1 further comprising controlling a build rate of the wellbore using the bending moment measurement.
10. The method of claim 1 further comprising controlling a walk rate of the wellbore using the bending moment measurement.
11. The method of claim 1 further comprising estimating the dog leg severity of the wellbore at successive depths along the wellbore and using the estimated dog leg severity to alter a drilling parameter to control the dog leg severity at each such depth.
12. A system for drilling a wellbore, comprising:
a first sensor disposed in a bottomhole assembly at a predetermined axial location configured to measure a bending moment in a first axis substantially orthogonal to a longitudinal axis of the bottomhole assembly;
a second sensor disposed in the bottomhole assembly at the predetermined axial location configured to measure a bending moment in a second axis substantially orthogonal to the longitudinal axis; and
a processor configured to compute therefrom a dog leg severity of the wellbore using:
δ=( k×M )/( E×I );
where M is a bending moment obtaining from the bending moment in the first axis and the bending moment in the second axis. E is the Young's modulus for the bottomhole assembly, I is the moment of inertia of the bottomhole assembly, and k is a conversion factor.
13. The system of claim 12 , wherein the first sensor and the second sensor are both strain gauges.
14. The system of claim 13 , wherein the strain gauges are chosen from the group consisting of (i) resistance strain gauges and (ii) optical strain gauges.
15. The system of claim 12 further comprising a steerable device disposed in the bottomhole assembly, the steerable device configured to act cooperatively with the processor to control curvature of the wellbore.
16. The system of claim 15 , wherein the steerable device is chosen from the group consisting of: (i) a downhole motor and (ii) an adjustable stabilizer.
17. The system of claim 12 , wherein the processor is at least partially located downhole.
18. The system of claim 12 , wherein the processor is located at a surface location.
19. The system of claim 12 further comprising a directional sensor comfigured to obtain a measurement indicative of the path of the wellbore.
20. The system of claim 19 , wherein the directional sensor comprises one of: (i) a magnetometer, (ii) an accelerometer, and (iii) a gyro device.
21. The system of claim 12 , wherein the first axis and the second axis are substantially orthogonal to each other.