Methods for designing fixed cutter bits and bits made using such methods

• US 20050080595A1
• Filed: 07/09/2004
• Published: 04/14/2005
• Est. Priority Date: 07/09/2003
• Status: Active Grant

• Current Assignee: Smith International Incorporated (SLB)
• Original Assignee: Smith International Incorporated (SLB)
• Inventors: Huang, Sujian
• Granted Patent: US 7,844,426 B2
• Time in Patent Office: Days
• US Class Current: 702/183
• CPC Class Codes: E21B 10/00 Drill bits specially adapted for deflecting the direction of boring E21B7/064; with means for collecting substances E21B27/00
• CPC Class Codes: E21B 44/00 Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions

Abstract

In one aspect, the invention provides a method for modeling the dynamic performance of a fixed cutter bit drilling earth formations. In one embodiment, the method includes selecting a drill bit and an earth formation to be represented as drilled, simulating the bit drilling the earth formation. The simulation includes at least numerically rotating the bit, calculating bit interaction with the earth formation during the rotating, and determining the forces on the cutters during the rotation based on the calculated interaction with earth formation and empirical data.

Claims

1. A method for analyzing a fixed cutter drill bit, said method comprising:

(a) selecting a cutter;

(b) selecting an earth formation;

(c) engaging said cutter with said earth formation at a selected orientation with respect to said earth formation;

(d) determining a force on the cutter; and

(e) storing data representative of at least the force applied to the cutter, the selected depth of cut, the selected orientation of the cutter, and a geometric parameter of the cutter.

2. The method of claim 1, wherein engaging comprises selecting a depth of cut in step (c), and further comprises rotating the drill bit to make the selected cutter cut through the earth formation at substantially the selected depth of cut.

3. The method of claim 1, wherein engaging comprises selecting a load acting on the cutter in step (c), and further comprises determining a depth at which the cutter penetrates the formation, under the selected load.

4. The method of claim 1, further comprising changing the selected orientation of the cutter and repeating steps (c)-(f).

5. The method of claim 1, wherein said force applied to the cutter includes at least one of an axial component, radial component, and a circumferential component.

6. The method of claim 1, wherein the geometric parameter of the cutter comprises at least one of cutter height, cutter shape, cutter size, bit axis offset of the cutter, bit cutting profile, and bit diameter.

7. The method of claim 1, wherein the drill bit comprises a plurality of cutters, wherein the plurality of cutters are engaged with the earth formation at about the same time, and steps (c)-(f) are repeated for each of the plurality of cutters.

8. The method of claim 1, wherein the bit design parameter is one selected from a number of blades, a number of the plurality of cutters, locations of the plurality of cutters, a diameter, and a shape of the drill bit.

9. The method of claim 1, wherein the earth formation is an actual formation, and the determining the force applied to the cutter comprises measuring an interaction force between the cutter and the actual formation.

10. The method of claim 9, wherein the actual formation is a defined formation used in a laboratory.

11. The method of claim 1, wherein the earth formation is a formation model based on solid mechanics principles and the determining the force applied to the cutter comprises calculating a cutter-formation interaction force based on the formation model.

12. The method of claim 11, wherein the formation model includes non-linear strength in a selected direction.

13. The method of claim 1, wherein the cutter engages the earth formation under a selected confining pressure.

14. The method of claim 13, wherein the selected confining pressure corresponds to a hydraulic pressure of a selected mud weight.

15. The method of claim 1, wherein the formation comprises two layers having different properties, and the cutter engages the earth formation at an interface between the two layers.

16. The method of claim 1, wherein the formation is inhomogeneous.

17. The method of claim 1, further comprising interpolating data for cutters and/or formations having values differing from ones used in parts (b)-(f) to form an interaction model.

18. The method of claim 1, wherein craters created in parts (b)-(f) are converted to coordinates representative of a geometry of the crater.

19. The method of claim 1, further comprising optically imaging the crater created in parts (b)-(f).

20. The method of claim 1, wherein calculated cut parameters are determined from numerical analysis of penetration of the cutter having a known geometry impressed on the earth formation sample having known mechanical properties with a selected force.

21. The method of claim 20, wherein said numerical analysis comprises at least one of finite difference analysis and finite element analysis.

22. The method of claim 20, wherein said numerical analysis comprises boundary element analysis.

23. A fixed cutter bit designed using at least a portion of information generated by the method of claim 1.

24. A method for analyzing a fixed cutter drill bit, said method comprising:

(a) selecting a blade having a plurality of cutters disposed thereon, the cutters having selected orientations and geometries;

(b) selecting an earth formation;

(c) engaging said blade with said earth formation such that certain of said cutters engage the formation at a selected orientation with respect to said earth formation;

(d) applying a force to said blade to make said blade cut through the formation at substantially the depth of cut;

(e) storing data representative of at least the force applied to the blade and to the plurality of cutters, the depth of cut, the selected orientation of the cutters, and the selected geometry of the cutters.

25. A method of simulating a fixed cutter bit drilling, the simulating comprising:

(a) selecting an earth formation;

(b) executing the simulation;

wherein the executing comprises;

i. determining, based on a means for determining a force, a force acting on at least one cutter,

ii. rotating the bit and redetermining the force acting on the at least one cutter; and

iii. repeating the rotating and redetermining for a number of rotations.

26. The method of claim 25, wherein selecting the earth formation further comprises including at least one of a transition layer and an inhomogeneous formation.

27. The method of claim 25, further comprising determining a predicted rate of penetration for the fixed cutter bit, based on parts (a) and (b).

28. The method of claim 25, wherein said force comprises at least one of an axial component, radial component, and a circumferential component.

29. The method of claim 28, further comprising summing an axial component of the force applied to the cutter for the each of the plurality of the cutters to produce a total axial force.

30. The method of claim 29, further comprising comparing the total axial force with a weight on bit.

31. The method of claim 28, further comprising summing a radial component of the force applied to the cutter for the each of the plurality of the cutters to produce a total radial force.

32. The method of claim 28, further comprising summing a circumferential component of the force applied to the cutter for the each of the plurality of the cutters to produce a total circumferential force.

33. The method of claim 25, further comprising calculating parameters for a crater formed when the at least one cutter contacts said earth formation.

34. The method of claim 33, further comprising graphically displaying a predicted bottomhole geometry formed when said crater is removed from a bottomhole surface.

35. The method of claim 25, further comprising graphically displaying at least one aspect of the simulation.

36. The method of claim 35, wherein the graphically displaying comprises displaying a bottomhole pattern being drilled in a transition layer.

37. A fixed cutter bit designed using the method of claim 25.

38. A method of improving drilling performance comprising:

selecting a formation to be drilled;

calculating a performance of a fixed cutter drill bit in the formation;

adjusting at least one of a drill bit design parameter and a drilling operating parameter; and

re-calculating the performance of the fixed cutter drill bit in the formation.