Kinetic Energy Harvesting in a Drill String

• US 20090256532A1
• Filed: 04/11/2008
• Published: 10/15/2009
• Est. Priority Date: 04/11/2008
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Ciglenec, Reinhart, Hoefel, Albert
• Granted Patent: US 8,022,561 B2
• Time in Patent Office: Days
• US Class Current: 322/4
• CPC Class Codes: E21B 41/0085 Adaptations of electric power generating means for use in boreholes

Abstract

An apparatus and method for harvesting energy in a wellbore is disclosed. In one embodiment, a harvester tool positioned in a wellbore for capturing energy in the wellbore is disclosed. The harvester tool includes a rotor comprising a magnet. The magnet is disposed eccentric to a center of the harvester tool. In addition, the rotor is rotatable around the center of the harvester tool. The harvester tool also includes a stator. Rotation of the rotor induces a voltage in the stator.

Claims

1. A harvester tool positioned in a wellbore for capturing energy in the wellbore, comprising:

a rotor comprising a magnet, wherein the magnet is disposed eccentric to a center of the harvester tool, and wherein the rotor is rotatable around the center of the harvester tool; and

a stator, wherein rotation of the rotor induces a voltage in the stator.

2. The harvester tool of claim 1, wherein the rotor is rotatable about the stator.

3. The harvester tool of claim 1, wherein the magnet is a permanent magnet.

4. The harvester tool of claim 1, further comprising bearings, wherein the bearings allow the rotor to rotate about the center of the harvester tool.

5. The harvester tool of claim 1, wherein the stator comprises stator windings.

6. The harvester tool of claim 1, wherein the rotor comprises a plurality of magnets.

7. The harvester tool of claim 1, wherein the rotor further comprises an eccentric mass, wherein the eccentric mass is disposed eccentric to the center of the harvester tool.

8. The harvester tool of claim 1, wherein the harvester tool is rotatable in an eccentric motion in the wellbore.

9. A method of capturing energy from a drill string in a wellbore, comprising:

(A) providing a harvester tool in the wellbore, wherein the harvester tool comprises a rotor and a stator, and wherein the rotor comprises a magnet disposed eccentric to a center of the harvester tool;

(B) rotating the harvester tool in an eccentric motion in the wellbore;

(C) rotating the magnet around the center of the harvester tool; and

(D) inducing a voltage in the stator, wherein rotation of the rotor induces the voltage in the stator.

10. The method of claim 9, further comprising rotating the rotor about the stator.

11. The method of claim 9, further comprising providing the rotor with a plurality of magnets.

12. The method of claim 9, further comprising providing the rotor with an eccentric mass, wherein the eccentric mass is disposed eccentric to the center of the harvester tool.

13. The method of claim 9, wherein rotation of the drill string rotates the harvester tool.

14. The method of claim 9, further comprising determining a load torque on the magnet for forced motion of the harvester tool, wherein the load torque is determined by:

−

m₂l₁l₂{dot over (Φ

)}₁² sin(Φ

₁−

Φ

₂)=−

τ

₁,

wherein m₂ is weight of the magnet, l₁ is a distance from the center of the harvester tool to a center of the wellbore, l₂ is a distance of the magnet from the center of the harvester tool, Φ

₁ is an angle of the center of the harvester tool with the center of the wellbore, {dot over (Φ

)}₁ is a first derivative to time of Φ

₁, Φ

₂ is an angle of the magnet with the center of the harvester tool, and τ

₁ is the load torque.

15. The method of claim 9, further comprising determining a maximum load torque on the magnet, wherein the maximum load torque is determined by:

m₂l₁l₂ω

₁²=τ

_1max,

wherein m₂ is weight of the magnet, l₁ is a distance from the center of the harvester tool to a center of the wellbore, l₂ is a distance of the magnet from the center of the harvester tool, ω

₁ is angular velocity of the center of the harvester tool around the center of the wellbore, and τ

_1max is the maximum load torque.

16. The method of claim 9, further comprising determining a load torque on the magnet when the harvester tool is rotating in an eccentric motion in the wellbore, wherein the load torque is determined by:

$m_2<br><br>l_1<br><br>l_2<br><br>{{\mathrm{\omega <br><br>}}_c^2<br><br>\left(\frac{R_c}{R_B}\right)}^2><br><br>{\mathrm{\tau <br><br>}}_1,$

wherein m₂ is weight of the magnet, l₁ is a distance from the center of the harvester tool to a center of the wellbore, l₂ is a distance of the magnet from the center of the harvester tool, ω

_c is angular velocity of the harvester tool, R_c is radius of the harvester tool, R_B is radius of the wellbore, and τ

₁ is the load torque.

17. The method of claim 16, further comprising determining a power output of the harvester tool for the load torque, wherein the power output is determined by:

P_max=τ

₁ω

₂(1+(R_C/R_B)²),

wherein P_max is the power output of the harvester tool, and ω

₂ is angular velocity of the magnet around the center of the harvester tool.

18. The method of claim 9, further comprising determining additional power available to the harvester tool, wherein the additional power is determined by:

ω

_cm₂l₂ sin(θ

)<

P_add,

wherein ω

_c is angular velocity of the harvester tool, m₂ is weight of the magnet, l₂ is a distance of the magnet from the center of the harvester tool, θ

is inclination angle of the harvester tool, and P_add is the additional power.

19. The method of claim 9, further comprising determining an induced open terminal voltage of the harvester tool, wherein the induced open terminal voltage is determined by:

$U_{\mathrm{ind}}<br><br>\mathrm{\_tt}=K_c<br><br>\left({\mathrm{\omega <br><br>}}_2-{\mathrm{\omega <br><br>}}_c\right)=K_c<br><br>{\mathrm{\omega <br><br>}}_c<br><br>\left(1+{\left(\frac{R_c}{R_B}\right)}^2\right),$

wherein U_ind is the induced open terminal voltage, tt is a terminal phase to phase voltage, K_c is a voltage constant, ω

₂ is angular velocity of the magnet around the center of the harvester tool, ω

_c is angular velocity of the harvester tool, R_c is radius of the harvester tool, and R_B is radius of the wellbore.

20. The method of claim 9, further comprising increasing a weight of the magnet to increase a power output of the harvester tool.