Methods for modeling, displaying, designing, and optimizing fixed cutter bits

• US 7,693,695 B2
• Filed: 07/09/2004
• Issued: 04/06/2010
• Est. Priority Date: 03/13/2000
• Status: Active Grant

• Current Assignee: Smith International Incorporated (Schlumberger NV)
• Original Assignee: Smith International Incorporated (Schlumberger NV)
• Inventors: Huang, Sujian J., Cariveau, Peter Thomas
• Primary Examiner(s): Shah; Kamini S
• Assistant Examiner(s): Saxena; Akash
• Application Number:
  US10/888,358
• Publication Number:
  US 20050133272A1
• Time in Patent Office: 2,097 Days
• Field of Search: 703/7, 703/10, 175/39, 175/57
• US Class Current: 703/7
• 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

Abstract

In one aspect, the invention provides a method for modeling the performance of a fixed cutter bit drilling an earth formation. 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, displaying the simulating, and adjusting at least one parameter affecting the performance. The method of design is used to make a fixed cutter drill bit. In another embodiment the method includes 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 designing a fixed cutter drill bit, comprising:

dynamically simulating the fixed cutter drill bit drilling in an earth formation, wherein the dynamically simulating comprises using at least one datum of a first iteration of the simulation in a subsequent iteration of the simulation;

graphically displaying at least a portion of the dynamic simulation in three dimensions;

adjusting a value of at least one design parameter for the fixed cutter drill bit based on the graphical display, wherein the adjusted design parameter affects at least one of bit wear and drill string dynamics; and

repeating the simulating and displaying to change a simulated performance of the fixed cutter drill bit.

2. The method of claim 1, further comprising repeating the simulating and adjusting to optimize a performance characteristic.

3. The method of claim 1, further comprising graphically displaying at least one fixed cutter drill bit design parameter.

4. The method of claim 1, wherein simulating further comprises:

simulating one or more performance characteristics at a plurality of increments of simulated fixed cutter drill bit rotation.

5. The method of claim 1, wherein simulating comprises:

selecting one or more parameters affecting drilling performance from the group consisting of control model type parameters, drill string design parameters, drill bit design parameters, earth formation parameters, drill bit/formation interface configuration parameters, and drilling operating parameters.

6. The method of claim 5, wherein the control model type parameters comprise at least one of cutter/formation control model, weight on bit (WOB) control model, and rate of penetration control (ROP) control model, constrained centerline model, and dynamic model.

7. The method of claim 5, wherein the drill string design parameters comprise at least one of number of components, type of components, material of components, length, strength and elasticity of components, O.D. of components, I.D. of components, nodal division of components, type of down hole assembly, length, strength, elasticity, density, density in mud, O.D. and I.D. of down hole assembly, hook load, drill bit type, drill bit design parameters, length, diameter, strength, elasticity, O.D., I.D. and wear model of drill bit, number of blades, orientation of blades, shape, size strength, elasticity, OD, ID and wear model of blades.

8. The method of claim 5, wherein the drill bit design parameters comprise at least one of number of cutters, bit cutting profile, position of cutters on drill bit blades, bit axis offset of the cutter, bit diameter, cutter radius on bit, cutter vertical height on bit, cutter inclination angle on bit, cutter body shape, cutter size, cutter height, cutter diameter, cutter orientation, cutter back rake angle, cutter side rake angle, working surface shape, working surface orientation, bevel size, bevel shape, bevel orientation, cutter hardness, PDC table thickness, and cutter wear model.

9. The method of claim 5, wherein the earth formation parameters comprise at least one of formation layer type, formation mechanical strength, formation density, formation wear characteristics, formation non-homogeneity, formation strength, anisotropic orientation, borehole diameter, empirical test data for earth formation type, multiple layer formation interfaces, formation layer depth, formation layer interface dip angle, formation layer interface strike angle, and empirical test data for multiple layer interface.

10. The method of claim 5, wherein the drilling operation parameters comprise at least one of the group consisting of weight on hit, bit torque, rate of penetration, rotary speed, rotating time, wear flat area, hole diameter, mud type, mud density, vertical drilling, drilling tilt angle, platform/table rotation, directional drilling, down hole motor rotation, bent drill sting rotation, and side load.

11. The method of claim 1, wherein the graphically displaying comprises graphically displaying at least one of the group consisting of bottom hole pattern, forces on bit, torque, weight on bit, imbalanced force components, total imbalanced force on bit, vector angle of total imbalanced force on bit, imbalance of forces on blade, forces on blades, radial force, circumferential force, axial force, total force on blade, vector angle of total force, forces on cutters, cutter forces defined in a selected Cartesian coordinate system, radial cutter force, circumferential cutter force, axial cutter force, an angle (Beta) between the radial force component and the circumferential force component of total imbalance force, total force on cutter, vector angle of total force, imbalance of forces on cutter, back rake angle of cutter against the formation, side rake angle, cut shape on cutters, wear on cutters, and contact of bit body with formation, impact force, restitution force, location of contact on bit or drill string, and orientation of impact force.

12. The method of claim 1, wherein simulating comprises determining one or more from the group consisting of bottom hole pattern, forces on bit torque, weight on bit imbalanced force components in a selected Cartesian coordinate system, total imbalanced force on bit, vector angle of total imbalanced force on bit, imbalance of forces on blade, forces on blades, forces defined in a selected Cartesian coordinate system, total force on blade, vector angle of total force on blade, imbalance of forces on blade, forces on cutters, forces on the cutter defined in a selected Cartesian coordinate system, normal cutter force (Fn), cutting force (Fc), side force (Fs), total force on cutter (Ft), vector angle of total force, imbalance of forces on cutter, back rake angle of cutter against the formation, side rake angle, cut shape on cutters, wear on cutters, and contact of bit body with formation, impact force, restitution force, location of contact on bit or drill string, and orientation of impact force.

13. The method of claim 1, wherein simulating further comprises simulating a plurality of increments of rotation of the fixed cutter drill bit drilling in the earth formation.

14. The method of claim 13, wherein graphically displaying at least a portion of the simulating further comprises:

graphically displaying a portion of the simulating at a selected one of the plurality of increments of rotation of the fixed cutter drill bit drilling in the earth formation.

15. The method of claim 13, wherein graphically displaying at least a portion of the simulating further comprises:

graphically displaying a portion of the simulating corresponding to the plurality of increments of rotation of the fixed cutter drill bit drilling in the earth formation.

16. The method of claim 1, wherein the graphically displaying comprises;

displaying, on a single display screen, a combination of numeric values representing input parameters affecting simulated performance of the fixed cutter drill bit and simulated performance characteristics.

17. The method of claim 1, wherein the graphically displaying comprises:

displaying a three-dimensional graphical depiction of a bottomhole pattern cut into the earth formation by the dill bit.

18. The method of claim 1, wherein the graphically displaying comprises:

displaying a three-dimensional graphical depiction of at least one cutter of the dill bit of the simulation spatially oriented relative to the drill bit, the three-dimensional graphical depiction including a cutter/formation interface contact area shape.

19. The method of claim 1, wherein the graphically displaying comprises:

displaying a three-dimensional graphical depiction of at least one cutter of the fixed cutter dill bit of the simulation, spatially oriented relative to at least one other cutter of the fixed cutter drill bit of the simulation, the three-dimensional graphical depiction including a cutter/formation interface contact area shape.

20. The method of claim 19, wherein the three-dimensional graphical depiction including a cutter/formation interface contact area shape further comprises a color coded indication of force distribution on the contact area.

21. The method of claim 20, further comprising a graphical depiction of a force vector acting on the at least one spatially oriented cutter.

22. The method of claim 1, wherein the graphically displaying comprises:

displaying a three-dimensional graphical depiction of at least one cutter of the fixed cutter dill bit of the simulation spatially oriented relative to the fixed cutter dill bit, the three-dimensional graphical depiction including a graphical depiction of cut force and normal force vectors acting on the at least one spatially oriented cutter.

23. The method of claim 1, wherein the graphically displaying comprises:

displaying a three-dimensional depiction of a cut force vector and a normal force vector acting on spatially oriented cutters.

24. The method of claim 1, wherein the graphically displaying comprises:

displaying a total imbalance force vector on the drill bit spatially oriented relative to the drill bit.

25. The method of claim 1, wherein the graphically displaying comprises:

displaying a total imbalance force vector on the drill bit spatially oriented relative to at least one cutter of the drill bit.

26. The method of claim 1, wherein the graphically displaying comprises:

displaying a radial imbalance force component, a circumferential force imbalance component, and a beta angle between the radial imbalance force component and the circumferential force imbalance component.

27. The method of claim 1, wherein the graphically displaying comprises:

displaying a graphical plot of the angle, beta, between the radial component of the total imbalance force vector on the fixed cutter drill bit and the circumferential component of the total imbalance force vector on the fixed cutter drill bit.

28. The method of claim 1, wherein the graphically displaying comprises:

displaying a three-dimensional graphical depiction of the fixed cutter drill bit of the simulation and a graphical depiction of a total imbalance force vector on the drill bit, the graphical depiction of the total imbalance force vector including a circumferential component, a radial component, and a beta angle between the radial and circumferential components spatially oriented relative to at least one cutter of the fixed cutter drill bit and depicted dynamically over a selected interval of time, corresponding to a sequence of a number of incremental portions of rotation.

29. The method of claim 1, wherein the graphically displaying comprises:

displaying a number of cutters in contact with the earth formation at a given point in time during simulated drilling.

30. The method of claim 1, wherein the graphically displaying comprises:

displaying a number of cutters in contact with the earth formation at a plurality of incremental rotation intervals over a selected period of time during simulated drilling.

31. The method of claim 1, wherein the simulating comprises:

solving for a dynamic response of the drill bit to an incremental rotation using a mechanics analysis model, and

repeating said solving for a select number of successive incremental rotations.

32. The method of claim 1, wherein the simulating comprises:

solving for a dynamic response of the fixed cutter drill bit to an increment of simulated rotation using a mechanics analysis model, and

repeating the solving, for a plurality of successive increments of simulated rotations.

33. The method of claim 1, wherein the simulating comprises:

determining an offset distance between a centerline of the fixed cutter drill bit and a theoretical centerline of a borehole drilled through an earth formation in response to an increment of simulated rotation of the fixed cutter drill bit using a mechanics analysis model, and

repeating the determining to determine a plurality of offset distances for successive increments of simulated rotation.

34. The method of claim 33, wherein the graphically displaying comprises displaying the determined offset distance between the centerline of the fixed cutter drill bit and the theoretical centerline of the borehole at an increment of simulated rotation of the fixed cutter drill bit.

35. The method of claim 33, wherein the graphically displaying comprises displaying a plurality of determined offset distances between the centerline of the fixed cutter drill bit and the theoretical centerline of the borehole at the plurality of successive increments of simulated rotation.

36. The method of claim 1, wherein the graphically displaying comprises displaying a historical plot of a plurality of determined offset distances between a centerline of the fixed cutter drill bit and a theoretical centerline of the borehole for a plurality of increments of simulated rotation.

37. The method of claim 1, wherein the graphically displaying comprises displaying a dynamic sequence of a plurality of determined offset distances between a centerline of the fixed cutter drill bit and a theoretical centerline of a borehole for a plurality of increments of simulated rotation over a period of time.

38. A method for designing a fixed cutter drill bit, comprising:

determining a performance characteristic of the fixed cutter drill bit through dynamic simulation, wherein the dynamic simulation comprises using at least one datum of a first iteration of the simulation in a subsequent iteration of the simulation;

graphically displaying the performance characteristic to a design engineer, as the design engineer adjusts at least one design parameter for a fixed cutter bit based on the graphical display, wherein at least a portion of the graphical display is in three-dimensions, and wherein the adjusted design parameter affects at least one of bit wear and drill string dynamics; and

outputting the fixed cutter drill bit design based on the graphically displaying and the adjustments to the at least one design parameter,

wherein determining the performance characteristic of the fixed cutter drill bit comprises selecting one or more parameters affecting drilling performance from the group consisting of control model type parameters, drill string design parameters, drill bit design parameters, earth formation parameters, drill bit/formation interface configuration parameters, and drilling operating parameters;

wherein the graphically displaying the performance characteristic comprises graphically displaying at least one of the group consisting of bottom hole pattern, forces on bit, torque, weight on bit, imbalanced force components, total imbalanced force on bit, vector angle of total imbalanced force on bit, imbalance of forces on blade, forces on blades, radial force, circumferential force, axial force, total force on blade, vector angle of total force, forces on cutters, cutter forces defined in a selected Cartesian coordinate system, radial cutter force, circumferential cutter force, axial cutter force, an angle (Beta) between the radial force component and the circumferential force component of total imbalance force, total force on cutter, vector angle of total force, imbalance of forces on cutter, back rake angle of cutter against the formation, side rake angle, cut shape on cutters, wear on cutters, and contact of bit body with formation, impact force, restitution force, location of contact on bit or drill string, and orientation of impact force.

39. The method of claim 38, further comprising graphically displaying at least one fixed cutter drill bit design parameter.

40. The method of claim 38, wherein determining the performance characteristic of the drill bit further comprises:

calculating the performance characteristic at a plurality of increments of rotation.

41. The method of claim 38, wherein the control model type parameters comprise at least one of cutter/formation control model, weight on bit (WOB) control model, and rate of penetration control (ROP) control model, constrained centerline model, and dynamic model.

42. The method of claim 38, wherein the drill string design parameters comprise at least one of number of components, type of components, material of components, length, strength and elasticity of components, O.D. of components, I.D. of components, nodal division of components, type of down hole assembly, length, strength, elasticity, density, density in mud, O.D. and I.D. of down hole assembly, hook load, drill bit type, drill bit design parameters, length, diameter, strength, elasticity, O.D., I.D. and wear model of drill bit, number of blades, orientation of blades, shape, size strength, elasticity, OD, ID and wear model of blades.

43. The method of claim 38, wherein the drill bit design parameters comprise at least one of number of cutters, bit cutting profile, position of cutters on drill bit blades, bit axis offset of the cutter, bit diameter, cutter radius on bit, cutter vertical height on bit, cutter inclination angle on bit, cutter body shape, cutter size, cutter height, cutter diameter, cutter orientation, cutter back rake angle, cutter side rake angle, working surface shape, working surface orientation, bevel size, bevel shape, bevel orientation, cutter hardness, PDC table thickness, and cutter wear model.

44. The method of claim 38, wherein the earth formation parameters comprise at least one of formation layer type, formation mechanical strength, formation density, formation wear characteristics, formation non-homogeneity, formation strength, anisotropic orientation, borehole diameter, empirical test data for earth formation type, multiple layer formation interfaces, formation layer depth, formation layer interface dip angle, formation layer interface strike angle, and empirical test data for multiple layer interface.

45. The method of claim 38, wherein the drilling operation parameters comprise at least one of the group consisting of weight on bit, bit torque, rate of penetration, rotary speed, rotating time, wear flat area, hole diameter, mud type, mud density, vertical drilling, drilling tilt angle, platform/table rotation, directional drilling, down hole motor rotation, bent drill string rotation, and side load.

46. The method of claim 38, wherein determining the performance characteristic of the fixed cutter drill bit comprises determining at least one of bottom hole pattern, forces on bit, torque, weight on bit, imbalanced force components in a selected Cartesian coordinate system, total imbalanced force on bit, vector angle of total imbalanced force on bit, an angle (Beta) between the radial force component and the circumferential force component of total imbalance force, imbalance of forces on blade, forces on blades, forces defined in a selected Cartesian coordinate system, radial force (normal force), circumferential force (tangential force), axial force (vertical force), total force on blade, vector angle of total force, imbalance of forces on blade, forces on cutters, cutter forces defined in a selected Cartesian coordinate system, radial cutter force (normal force), circumferential cutter force (tangential force), axial cutter force (vertical force), total force on cutter, vector angle of total force, imbalance of forces on cutter, back rake angle of cutter against the formation, side rake angle, cut shape on cutters, wear on cutters, and contact of bit body with formation, impact force, restitution force, location of contact on bit or drill string, and orientation of impact force.

47. The method of claim 38, wherein determining a performance characteristic of the fixed cutter drill bit comprises:

calculating the performance characteristics over a plurality of incremental portions of rotation; and

graphically displaying the performance characteristics at a selected incremental portion of calculated rotation.

48. The method of claim 38, wherein:

determining a performance characteristic comprises calculating the performance characteristic over a plurality of incremental portions of rotation; and

graphically displaying comprises displaying the performance characteristic in a sequence of displays over a series of sequential incremental portions of calculated rotation.

49. The method of claim 38, wherein the graphically the performance characteristic comprises:

displaying a calculated performance characteristic selected from the group consisting of bottom hole pattern, forces on blades, forces on cutters, cut shape on cuff ers, wear on cutters, and contact of bit body with earth formation.

50. The method of claim 38, wherein the graphically displaying the performance characteristic comprises:

displaying a combination of numeric values representing input parameters affecting performance calculation and performance characteristics on a single screen.

51. The method of claim 38, wherein the graphically displaying the performance characteristic comprises:

displaying a three-dimensional graphical depiction of a bottomhole pattern cut into a formation by the dill bit in the earth formation.

52. The method of claim 38, wherein the graphically displaying the performance characteristic comprises:

displaying a three-dimensional graphical depiction of at least one cutter spatially oriented relative to the fixed cutter drill bit, the three-dimensional graphical depiction including a cutter/formation interface contact area shape.

53. The method of claim 52, wherein the cutter contact/formation interface contact area shape depiction further comprises a color coded indication of force distribution on the contact area.

54. The method of claim 38, wherein the graphically displaying the performance characteristic comprises:

displaying a three-dimensional graphical depiction of at least one cutter, spatially oriented relative to at least one other cutter of the fixed cutter drill bit, the three-dimensional graphical depiction including a cutter/formation interface contact area shape.

55. The method of claim 52, further comprising a graphical depiction of a force vector acting on the at least one spatially oriented cutter.

56. The method of claim 54, wherein the cutter contact/formation interface contact area shape depiction further comprises a color coded indication of force distribution on the contact area.

57. The method of claim 54, further comprising a graphical depiction of a force vector acting on the at least one spatially oriented cutter.

58. The method of claim 38, wherein the graphically displaying the performance characteristic comprises:

displaying a three-dimensional graphical depiction of at least one cutter spatially oriented relative to the drill bit, the three-dimensional graphical depiction including a graphical depiction of cut force, and normal force vectors acting on the at least one spatially oriented cutter.

59. The method of claim 38, wherein the displaying a graphical display a performance characteristic comprises:

displaying a three-dimensional graphical depiction of a plurality of cutters of a dill bit of the calculation, the cutters depicted spatially oriented relative each other, the three-dimensional graphical depiction including a graphical depiction of a cut force vector and a normal force vector acting on the spatially oriented cutters.

60. The method of claim 38, wherein the graphically displaying the performance characteristic comprises:

displaying a three-dimensional graphical depiction of the fixed cutter dill bit and a graphical depiction of a total imbalanced force vector on the fixed cutter drill bit spatially oriented relative to the fixed cutter drill bit.

61. The method of claim 38, wherein the graphically displaying the performance characteristic comprises:

displaying a three-dimensional graphical depiction of the fixed cutter dill bit and a graphical depiction of a total imbalanced force vector on the fixed cutter drill bit spatially oriented relative to at least one cutter of the fixed cutter drill bit.

62. The method of claim 38, wherein the graphically displaying the performance characteristic comprises:

displaying a three-dimensional graphical depiction of a fixed cutter dill bit and a graphical depiction of a total imbalance force vector on the fixed cutter drill bit, the three-dimensional graphical depiction including a radial imbalance force component and a circumferential force imbalance component, and a Beta angle between the radial imbalance force component and the circumferential force imbalance components.

63. The method of claim 38, wherein the graphically displaying the performance characteristic comprises:

displaying a graphical plot of the angle, beta, between the radial component of the total imbalance force vector on the fixed cutter drill bit and the circumferential component of the total imbalance force vector on the fixed cutter drill bit.

64. The method of claim 38, wherein the graphically displaying the performance characteristic comprises:

displaying a three-dimensional graphical depiction of a fixed cutter dill bit and a graphical depiction of a total imbalance force vector on the fixed cutter drill bit, the graphical depiction of a total imbalance force vector including a circumferential component, a radial component, and a beta angle between the radial and circumferential components spatially oriented relative to at least one cutter of the fixed cutter drill bit and depicted dynamically over a selected interval of time.

65. The method of claim 38, wherein the graphically displaying the performance characteristic comprises displaying a graphical display of the number of cutters in contact with the earth formation a given point in time.

66. The method of claim 38, wherein the graphically displaying the performance characteristic comprises displaying a graphical display of the number of cutters in contact with the earth formation at a plurality of incremental rotation intervals over a selected period of time.

67. The method of claim 38, wherein the determining a performance characteristic of the fixed cutter drill bit comprises:

solving for a response to an increment of rotation of the fixed cutter drill bit, using a mechanics analysis model of the fixed cutter drill bit on a drill string; and

repeating the solving for a select number of successive increments of rotation.

68. The method of claim 38, wherein the determining a performance characteristic of the fixed cutter drill bit comprises;

calculating an offset of a centerline of the fixed cutter drill bit from a central axis of a borehole in response to rotation of the fixed cutter drill bit on a drill string; and

repeating the calculating for a select number of successive increments of the rotation.

69. The method of claim 68, wherein the calculating an offset of a centerline of the fixed cutter drill bit from a central axis of a borehole drilled through the earth formation in response to rotation comprises:

calculating the offset of the centerline of the fixed cutter drill bit from the central axis of a borehole drilled through the earth formation in response to an increment of rotation of the fixed cutter drill bit using a mechanics analysis model.

70. The method of claim 38, wherein the graphically displaying the performance characteristic comprises displaying a graphical display of a calculated offset of the fixed cutter drill bit centerline from a central axis of a borehole drilled into the earth formation.

71. The method of claim 38, wherein the graphically displaying the performance characteristic comprises displaying a graphical display of an offset between a centerline of the fixed cutter drill bit and the central axis of a borehole drilled through the earth formation, the offset calculated for an increment of rotation of the fixed cutter drill bit using a mechanics analysis model.

72. The method of claim 71, wherein the graphically displaying the performance characteristic comprises displaying a graphical display of a calculated centerline offset at an increment of rotation of the fixed cutter drill bit.

73. The method of claim 71, wherein the graphically displaying the performance characteristic comprises displaying a historical plot of a plurality of calculated centerline offsets at a plurality of increments of rotation of the fixed cutter drill bit.

74. The method of claim 71, wherein the graphically displaying the performance characteristic comprises displaying a dynamic sequence of a plurality of calculated centerline offsets at a plurality of respective increments of rotation of the fixed cutter drill bit.

75. A method for designing a fixed cutter drill bit, comprising:

calculating a plurality of performance characteristics of the fixed cutter drill bit through dynamic simulation, wherein the wherein the dynamic simulation comprises using at least one datum of a first iteration of the simulation in a subsequent iteration of the simulation, and wherein the calculated performance characteristic is selected form the group comprising;

trajectories and cut patterns of at least two cutters on separate blades of a fixed cutter drill bit, the cutters having partially overlapping trajectories such that a ridge is formed between grooves of material removed from an earth formation being drilled by the separate cutters during drilling;

a cutter/formation interface area size, shape, and force vectors for each of at least two cutters on separate blades of the fixed cutter drill bit, the cutters having partially overlapping trajectories such that material removed from an earth formation being drilled by one of the at least two cutters affects the cutter/formation interface area, size, shape and force vectors of the other of the at least two separate cutters during drilling;

imbalance force vectors acting upon a fixed cutter drill bit during drilling through an earth formation;

imbalance force vectors acting upon the fixed cutter drill bit during drilling through an earth formation, including components of circumferential imbalance force and radial imbalance force and an angle, Beta, between the imbalance for components;

Beta angle, between components of an imbalance force acting on the fixed cutter drill bit drilling through an earth formation;

forces acting upon a plurality of blades of a fixed cutter drill bit during drilling through an earth formation;

forces acting upon a plurality of cutters of the fixed cutter drill bit during drilling through an earth formation;

wear pattern on a plurality of cutters on the fixed cutter drill bit over a selected time interval;

force vectors acting upon at least one cutter on the fixed drill bit during drilling through a transition between different layers of an earth formation;

dynamic force vectors acting upon at least one cutter on the fixed cutter drill bit during drilling through an earth formation;

dynamic force vectors acting upon a plurality of cutters on the fixed cutter drill bit during drilling through an earth formation;

dynamic force vectors acting upon at least one cutter on the fixed cutter drill bit during drilling through a transition between a plurality of different layers of an earth formation;

dynamic force vectors acting upon a plurality of cutters on the fixed cutter drill bit during drilling through a transition between a plurality of different layers of an earth formation; and

selectively graphically displaying, to a design engineer, the plurality of calculated performance characteristics of the fixed cutter drill bit, as the design engineer adjusts design parameters based on the graphical display, wherein at least a portion of the graphical display is in three dimensions.

76. The method of claim 75, wherein the selectively displaying further comprised toggling by the design engineer between two or more of the plurality of calculated parameters and characteristics of the fixed cutter drill bit, as the design engineer adjusts design parameters.

77. A method for designing a fixed cutter drill bit, comprising:

simulating a dynamic performance of the fixed cutter drill bit drilling into a borehole without the centerline of the fixed cutter drill bit constrained into alignment with the centerline of the borehole, wherein the simulating comprises six degrees of freedom;

displaying a visual display of at least one characteristic of the simulated performance; and

adjusting a value of at least one design parameter for a fixed cutter bit assembly according to the visual display.

78. The method of claim 77, comprising repeating the simulating, the displaying and the adjusting to change the characteristic of the simulated performance.

79. The method of claim 78, the characteristic of performance is changed to optimize the characteristic of the simulated performance.

80. The method for designing a fixed cutter bit assembly of claim 77, wherein the displaying comprises displaying a characteristic of the dynamic performance over a selected time interval.