Method for optimizing drill bit design parameters

• US 6,349,595 B1
• Filed: 09/27/2000
• Issued: 02/26/2002
• Est. Priority Date: 10/04/1999
• Status: Expired due to Term

• Current Assignee: Smith International Incorporated (SLB)
• Original Assignee: Smith International Incorporated (SLB)
• Inventors: Zausa, Fabrizio, Civolani, Lorenzo
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): Politzer, Jay L.
• Application Number:
  US09/671,231
• Time in Patent Office: 517 Days
• Field of Search: 731/520.2, 73/81, 73/85, 731/520.3, 731/525.2, 731/525.9
• US Class Current: 73/152.02
• CPC Class Codes: E21B 49/005 Testing the nature of borehole walls or the formation by using drilling mud or cutting data
• CPC Class Codes: G01N 3/42 by performing impressions under a steady load by indentors, e.g. sphere, pyramid G01N3/54 takes precedence
• CPC Class Codes: G01N 33/24 Earth materials G01N33/42 takes precedence

Abstract

A method for selecting a drilling parameter is disclosed. The method includes determining a loading displacement relationship for samples of earth formations. The loading displacement measurements are made by an indenter. The drilling parameter is selected from the loading displacement relationship. In one embodiment of the invention, the loading displacement relationship is determined from cuttings made during drilling of a wellbore. The loading displacement relationship determined during drilling is used to select at least one drilling parameter during drilling to improve drilling performance. Drilling parameters which can be selected include mill tooth and/or insert bit type; type of gauge protection to be used on the bit; type, size and orientation of jet nozzles on the bit; and blade structure, cutter type and density as well as the cutter impact resistance for fixed cutter bits. Other drilling parameters include weight on bit, drill bit rotation rate, and drilling fluid flow rate.

Claims

1. A method for selecting parameters for drilling a wellbore through earth formations, comprising:

determining a loading displacement relationship from measurements made by an indenter on samples of selected earth formations obtained during drilling of the wellbore;

characterizing said loading displacement relationship with respect to a compressive strength of said selected earth formations, the characterizing comprising measuring said loading displacement through a preselected displacement range on samples of a plurality of selected earth formations, determining a substantially linear portion of said relationship for each of said samples from said plurality of formations and correlating a slope of said substantially linear portion for each of said samples from said plurality of formations to a measured compressive strength of each of said samples from said plurality of formations; and

selecting at least one drill bit design parameter during the drilling of the wellbore based on said loading displacement relationship.

2. The method as defined in claim 1 further comprising determining a compressive strength of at least one additional formation sample, comprising:

performing a loading displacement test on said at least one additional sample;

determining a slope of a linear portion of the loading displacement relationship performed on the at least one additional sample; and

determining the compressive strength of the at least one additional sample from the correlation of the slopes of the each of said samples from said plurality of formations to the measured compressive strength of each of said samples from the plurality of formations.

3. The method as defined in claim 1 wherein said at least one additional sample is taken from a wellbore during drilling thereof, and said at least one drill bit design parameter is adjusted in response to a slope of a linear portion of said loading displacement relationship determined for said at least one additional sample taken during said drilling of said wellbore.

4. The method as defined in claim 1 wherein said at least one drill bit design parameter comprises mill tooth type on a roller cone drill bit.

5. The method as defined in claim 1 wherein said at least one drill bit design parameter comprises insert type on a roller cone drill bit.

6. The method as defined in claim 1 wherein said at least one drill bit design parameter comprises gauge protection type.

7. The method as defined in claim 1 wherein said at least one drill bit design parameter comprises jet nozzle type and orientation.

8. The method as defined in claim 1 wherein said at least one drill bit design parameter comprises at least one of bit profile, cutter density, cutter type and cutter impact resistance on a fixed cutter drill bit.

9. The method as defined in claim 1 further comprising selecting at least one of weight on bit, bit rotation rate and drilling fluid flow rate based on said loading displacement relationship.

10. The method as defined in claim 1 wherein said samples are disposed in a resin, said resin is cured, and a test specimen is generated therefrom by grinding a substantially parallel flat surfaces on said cured resin.

11. A method for selecting drilling parameters, comprising:

measuring a loading displacement relationship through a preselected displacement range on at least one sample of at least one earth formation collected during drilling of a wellbore;

determining a substantially linear portion of said loading displacement relationship for said at least one sample;

correlating a slope of said substantially linear portion of said at least one sample to a relationship of a compressive strength to a linear portion of a loading displacement relationship of other formation samples to determine a compressive strength of said at least one sample; and

selecting at least one drill bit design parameter during the drilling of the wellbore in response to said determined compressive strength.

12. The method as defined in claim 11 wherein said at least one drill bit design parameter comprises mill tooth type on a roller cone drill bit.

13. The method as defined in claim 11 wherein said at least one drill bit design parameter comprises insert type on a roller cone drill bit.

14. The method as defined in claim 11 wherein said at least one drill bit design parameter comprises gauge protection type.

15. The method as defined in claim 11 wherein said at least one drill bit design parameter comprises jet nozzle type and orientation.

16. The method as defined in claim 11 wherein said at least one drill bit design parameter comprises at least one of bit profile, cutter density, cutter type and cutter impact resistance on a fixed cutter drill bit.

17. The method as defined in claim 11 further comprising selecting at least one of weight on bit, bit rotation rate and drilling fluid flow rate based on said loading displacement relationship.

18. The method as defined in claim 11 wherein said samples are disposed in a resin, said resin is cured, and a test specimen is generated therefrom by grinding a substantially parallel flat surfaces on said cured resin.