Apparatus and method for drilling with casing

1. A method of drilling a wellbore with casing, comprising:

placing a string of casing with a drill bit at the lower end thereof into a previously formed wellbore;

urging the string of casing axially downward to form a new section of wellbore;

pumping fluid through the string of casing into an annulus formed between the casing string and the new section of wellbore; and

diverting a portion of the fluid from the annulus into an upper annulus in the previously formed wellbore.

2. The method of claim 1 , wherein the annulus is smaller in diameter than the upper annulus.

3. The method of claim 1 , wherein the fluid travels upward in the annulus at a higher velocity than the fluid travels in the upper annulus.

4. The method of claim 1 , wherein the previously formed wellbore is at least partially lined with casing.

5. The method of claim 1 , wherein the fluid carries wellbore cuttings upwards towards a surface of the wellbore.

6. The method of claim 1 , further including rotating the string of casing as the string of casing is urged axially downward.

7. The method of claim 1 , wherein the fluid is diverted into the upper annulus from a flow path in a run-in string of tubulars disposed above the string of casing.

8. The method of claim 7 , wherein the flow path is selectively opened and closed to control the amount of fluid flowing through the flow path.

9. The method of claim 1 , wherein the fluid is diverted into the upper annulus via an independent fluid path.

10. The method of claim 9 , wherein the independent fluid path is formed at least partially within the string of casing.

11. The method of claim 9 , wherein the independent fluid path is selectively opened and closed to control the amount of fluid flowing through the independent fluid path.

12. The method of claim 1 , wherein the fluid is diverted into the upper annulus via a flow apparatus disposed in the string of casing.

13. The method of claim 12 , wherein the flow apparatus includes one or more ports that may be selectively opened and closed to control the amount of fluid flowing through the flow apparatus.

14. The method of claim 13 , wherein the ports are positioned in an upward direction to direct the flow of fluid upward into the upper annulus.

15. A method of drilling with casing to form a wellbore, comprising:

placing a casing string with a drill bit at the lower end thereof into a previously formed wellbore;

urging the easing string axially downward to form a new section of wellbore;

pumping fluid through the casing string into an annulus formed between the casing string and the new section of wellbore; and

diverting a portion of the fluid into an upper annulus in the previously formed wellbore from a flow path in a run-in string of tubulars disposed above the casing string.

16. The method of claim 15 , wherein the annulus is smaller in diameter than the upper annulus.

17. The method of claim 15 , wherein the fluid travels upward in the annulus at a higher velocity than the fluid travels in the upper annulus.

18. The method of claim 15 , wherein the previously formed wellbore is at least partially lined with casing.

19. The method of claim 15 , further including rotating the string of casing as the string of casing is urged axially downward.

20. The method of claim 15 , further including diverting a second portion of fluid into an upper annulus in the previously formed wellbore from an independent fluid path formed at least partially within the casing string.

21. The method of claim 15 , wherein the fluid carries wellbore cuttings upwards towards a surface of the wellbore.

22. The method of claim 15 , wherein the independent fluid path is selectively opened and closed to control the amount of fluid flowing through the independent fluid path.

23. The method of claim 15 , wherein a flow apparatus is disposed in the casing string.

24. The method of claim 23 , wherein the flow apparatus includes one or more ports that may be selectively opened and closed to control the amount of fluid flowing through the flow apparatus into the upper annulus.

25. An apparatus for forming a wellbore, comprising:

a casing string with a drill bit disposed at an end thereof; and

a working string coupled to the casing string;

a fluid bypass disposed above the drill bit and operatively connected to the casing string for diverting a portion of fluid flowing towards the drill bit from an interior portion of the working string to an exterior portion of the working string.

26. The apparatus of claim 25 , wherein the fluid bypass is selectively opened and closed to control the amount of fluid flowing through the fluid bypass.

27. The apparatus of claim 25 , further including a flow apparatus disposed in the casing string.

28. The method of claim 27 , wherein the flow apparatus includes one or more ports that may be selectively opened and closed to control the amount of fluid flowing through the flow apparatus.

29. The apparatus of claim 25 , wherein the fluid bypass is formed at least partially within the casing string.

30. An apparatus for forming a wellbore, comprising:

a casing string with a drill bit disposed at an end thereof; and

a fluid bypass operatively connected to the casing string for diverting a portion of fluid from a first to a second location within the wellbore as the wellbore is formed, wherein the fluid bypass is selectively opened and closed to control the amount of fluid flowing through the fluid bypass.

31. An apparatus for forming a wellbore, comprising:

a casing string with a drill bit disposed at an end thereof;

a fluid bypass operatively connected to the casing string for diverting a portion of fluid from a first to a second location within the wellbore as the wellbore is formed;

a flow apparatus disposed in the casing string, wherein the flow apparatus includes one or more ports that may be selectively opened and closed to control the amount of fluid flowing through the flow apparatus.