Method for simulating drilling of roller cone bits and its application to roller cone bit design and performance

A method for designing a roller cone drill bit, comprising:

• selecting initial bit design parameters, comprising at least a geometry of a cutting element on said bit;
• selecting drilling parameters, comprising at least an axial force on said bit;
• selecting an earth formation to be represented as drilled;
• calculating from said selected drilling parameters, said selected bit design parameters and said earth formation, parameters for a crater formed when one of a plurality of said cutting elements contacts said earth formation;
• calculating a bottomhole geometry, wherein said crater is removed from a bottomhole surface;
• simulating incrementally rotating said bit, and repeating said calculating of said crater parameters and said bottomhole geometry based on calculated roller cone rotation speed and geometrical location with respect to rotation of said roller cone drill bit about its axis;
• and
• adjusting at least one of said initial bit design parameters, and repeating said calculating said crater parameters, said bottom hole geometry and said simulated incrementally rotating until an optimal set of said bit design parameters is obtained.

A method for optimizing drilling parameters of a roller cone drill bit drilling an earth formation, comprising:

• selecting bit design parameters, comprising at least a geometry of a cutting element on said bit;
• selecting initial drilling parameters, comprising at least an axial force on said bit;
• selecting an earth formation to be represented as drilled;
• calculating from said selected drilling parameters, said selected bit design parameters and said earth formation, parameters for a crater formed when one of a plurality of said cutting elements contacts said earth formation;
• calculating a bottomhole geometry, wherein said crater is removed from a bottomhole surface;
• simulating incrementally rotating said bit, and repeating said calculating of said crater parameters and said bottomhole geometry based on calculated roller cone rotation speed and geometrical location with respect to rotation of said roller cone drill bit about its axis;
• and
• adjusting at least one of said initial drilling parameters, and repeating said calculating said crater parameters, said bottom hole geometry and said simulating incrementally rotating until an optimal set of said drilling parameters is obtained.