Method and system for predicting performance of a drilling system having multiple cutting structures

A computer program stored on a computer-readable medium for execution by a computer to use in a drilling system having multiple cutting structures, including a bit and one or more secondary cutting structures, to balance the rate of penetration of the drilling system and the wear on the cutting structures by controlling weight on bit and RPM, the computer program comprising:

• (O1) instructions for calculating a predicted rate of penetration for the bit, using in the calculation the current predicted wear on the bit and the properties of the rock to be penetrated by the bit;
• (O2) instructions for calculating a predicted rate of penetration for at least one of the one or more secondary cutting structures, using in the calculation the current predicted wear on the secondary cutting structure and the properties of the rock to be penetrated by the secondary cutting structure;
• (O3) instructions for determining the slowest rate of penetration among those calculated for the bit and at least one the one or more secondary cutting structures;
• (O4) instructions for calculating the weight on bit and RPM for each of the bit and at least one of the one or more secondary cutting structures to substantially match the determined slowest rate of penetration;
• and
• (O5) instructions for summing the calculated weights on bit to calculate a goal weight on bit for the drilling system and setting a goal RPM for a rotary portion of the drilling system to the slowest RPM calculated for the cutting structures that rotate at substantially the speed of the rotary portion of the drilling system.

A computer implemented method to use in a drilling system having multiple cutting structures, including a bit and one or more secondary cutting structures, to balance the rate of penetration of the drilling system and the wear on the cutting structures by controlling weight on bit and RPM when drilling a well along a predicted path, the method comprising:

• during a planning stage:
• (P1) constructing a pseudo log for the well;
• (P2) using the pseudo log to calculate shale plasticity along the predicted path;
• (P3) using the pseudo log to calculate confined and unconfined rock strengths along the predicted path;
• during an operations stage during which the well is drilled:
• (O1) calculating a predicted rate of penetration for the bit, using in the calculation the current predicted wear on the bit and the properties of the rock to be penetrated by the bit;
• (O2) calculating a predicted rate of penetration for at least one of the one or more secondary cutting structures, using in the calculation the current predicted wear on the secondary cutting structure and the properties of the rock to be penetrated by the secondary cutting structure;
• (O3) determining the slowest rate of penetration among those calculated for the bit and at least one the one or more secondary cutting structures;
• (O4) calculating the weight on bit and RPM for each of the bit and at least one of the one or more secondary cutting structures to substantially match the determined slowest rate of penetration;
• and
• (O5) summing the calculated weights on bit to calculate a goal weight on bit for the drilling system and setting a goal RPM for a rotary portion of the drilling system to the slowest RPM calculated for the cutting structures that rotate at substantially the speed of the rotary portion of the drilling system;
• and
• (O6) adjusting the weight on bit for the drilling system so that it substantially matches the goal weight on bit and adjusting the RPM of the rotary portion of the drilling system so that it substantially matches the goal RPM.

A graphical user interface (“GUI”) for use in configuring a drilling system having multiple cutting structures to balance the rate of penetration of the drilling system and the wear on the cutting structures by controlling weight on bit and RPM, the GUI comprising:

• a display for constructing a pseudo log;
• a display for entering constraints for the multiple cutting structures;
• a display for displaying a goal weight on bit for the drilling system calculated using the pseudo log and the constraints;
• and
• a display for displaying a goal RPM for a rotary portion of the drilling system calculated using the pseudo log and the constraints.