Bit for drilling with casing or liner string and manufacture thereof

1. A bit for drilling with a casing or liner string, comprising:

a tubular stem made from a high strength metal or alloy;

a head:

having a cutting face with an inner cone, an outer shoulder, and an intermediate nose between the cone and the shoulder;

attached to an end of the stem; and

made from a nonferrous metal or alloy;

a plurality of blades formed integrally with the head, made from the nonferrous metal or alloy, and each extending from a center of the cutting face to the shoulder;

a plurality of superhard cutters mounted along each blade;

a plurality of gauge pads formed integrally with the stem; and

a flush joint formed between each blade and a respective gauge pad,

wherein:

a yield strength of the high strength metal or alloy is at least twice a yield strength of the nonferrous metal or alloy,

the bit further comprises a lock joint and a lap joint attaching the head to the stem, and

the lap joint has a lap coupling of the stem engaged with a lap coupling of the head.

2. The bit of claim 1 , wherein:

the high strength metal or alloy is steel, and

the nonferrous metal or alloy is nickel-based.

3. The bit of claim 1 , further comprising a layer of hardfacing deposited on a bottom or outer surface of each blade and an outer surface of each pad.

4. The bit of claim 1 , wherein the lock joint comprises:

a receptacle having a hole formed through the lap coupling of the stem and a socket formed into the lap coupling of the head;

a fastener disposed in the socket and the hole; and

a plug closing the receptacle.

5. The bit of claim 1 , wherein:

the lap coupling of the head has a chamfer formed in an outer surface thereof, and

the bit further comprises a seal disposed between the chamfer and the lap coupling of the stem.

6. The bit of claim 1 , wherein the lap coupling of the head has a taper formed in an inner surface thereof for guiding a second drill bit into the head.

7. The bit of claim 1 , wherein the head further has:

a plurality of fluid courses formed between the blades;

a plenum formed therein; and

a plurality of ports extending from the fluid courses and to the plenum.

8. The bit of claim 7 , wherein:

the bit further comprises a plurality of nozzles,

each nozzle is mounted in a respective port, and

each nozzle is made from a ceramic or cermet.

9. The bit of claim 7 , wherein:

the blades are primary blades,

some of the ports are inner ports disposed adjacent to the center of the cutting face, and

the bit further comprises a plurality of secondary blades each extending from a location on the cutting face adjacent to a respective inner port to the shoulder.

10. The bit of claim 1 , wherein:

each flush joint has a curved cut at a shoulder end of the respective blade and a curved cut at an end of the respective gauge pad adjacent to the shoulder end of the blade,

the blades and pads have a slight helical curvature, and

the curved cuts conform to the slight helical curvature.

11. The bit of claim 1 , wherein:

the stem has a reserve port formed through a wall thereof, and

the bit further comprises a rupture disk closing the reserve port.

12. The bit of claim 1 , wherein:

the end is a lower end of the stem, and

the bit further comprises a threaded coupling formed at an upper end of the stem for connection to the casing or liner string.

13. A method of drilling a wellbore using the bit of claim 12 , comprising:

assembling the bit as part of the casing or liner string;

drilling the casing or liner string into the wellbore to extend the wellbore through a problem formation;

cementing the casing or liner string into the wellbore; and

drilling out an inner portion of the head with a polycrystalline diamond compact or roller cone second drill bit,

wherein an outer portion of the head remains after drill-out.

14. A method of drilling a wellbore, comprising:

assembling a bit as part of a casing or liner string, the bit comprising:

a tubular stem made from a high strength metal or alloy;

a head:

having a cutting face with an inner cone, an outer shoulder, and an intermediate nose between the cone and the shoulder;

attached to an end of the stem; and

made from a nonferrous metal or alloy;

a plurality of blades formed integrally with the head, made from the nonferrous metal or alloy, and each extending from a center of the cutting face to the shoulder;

a plurality of superhard cutters mounted along each blade;

a plurality of gauge pads formed integrally with the stem; and

a flush joint formed between each blade and a respective gauge pad,

wherein:

a yield strength of the high strength metal or alloy is at least twice a yield strength of the nonferrous metal or alloy,

the end is a lower end of the stem,

the bit further comprises a threaded coupling formed at an upper end of the stem for connection to the casing or liner string,

the bit further comprises a lock joint and a lap joint attaching the head to the stem, and

an outer portion of the head includes an essential portion of the lock joint;

drilling the casing or liner string into the wellbore to extend the wellbore through a problem formation;

cementing the casing or liner string into the wellbore; and

drilling out an inner portion of the head with a polycrystalline diamond compact or roller cone second drill bit,

wherein the outer portion of the head remains after drill-out.

15. A bit for drilling with a casing or liner string, comprising:

a head having a cutting face with an inner cone and an intermediate nose and made from a nonferrous metal or alloy;

a tubular stem attached to the head, having an outer shoulder of the cutting face, and made from a high strength metal or alloy;

a plurality of first blades formed integrally with the head, made from the nonferrous metal or alloy, and each extending from a center of the cutting face to the nose;

a plurality of superhard cutters mounted along each first blade;

a plurality of second blades formed integrally with the stem, made from the high strength metal or alloy, and each having a curved shoulder portion and a gage portion;

a plurality of superhard cutters mounted along each shoulder portion; and

a flush joint formed between each first and second blade,

wherein:

a yield strength of the high strength metal or alloy is at least twice a yield strength of the nonferrous metal or alloy,

the bit further comprises a lock joint and a lap joint attaching the head to the stem, and

the lap joint has a lap coupling of the stem engaged with a lap coupling of the head.

16. The bit of claim 15 , wherein the lock joint comprises:

a receptacle having a hole formed through the lap coupling of the stem and a socket formed into the lap coupling of the head;

a fastener disposed in the socket and the hole; and

a plug closing the receptacle.

17. The bit of claim 15 , wherein:

the lap coupling of the head has a chamfer formed in an outer surface thereof, and

the bit further comprises a seal disposed between the chamfer and the lap coupling of the stem.

18. The bit of claim 15 , wherein the lap coupling of the head has a taper formed in an inner surface thereof for guiding a second drill bit into the head.

19. The bit of claim 15 , wherein each flush joint has a miter cut at a nose end of the respective first blade and a miter cut at a shoulder end of the respective second blade.

20. A method of drilling a wellbore using the bit of claim 15 , comprising:

assembling the bit as part of the casing or liner string;

drilling the casing or liner string into the wellbore to extend the wellbore through a problem formation;

cementing the casing or liner string into the wellbore; and

drilling out the head with a polycrystalline diamond compact or roller cone second drill bit.