DRILLING FLUID AND METHOD FOR DRILLING A WELLBORE

• US 20130126243A1
• Filed: 01/11/2013
• Published: 05/23/2013
• Est. Priority Date: 03/02/2007
• Status: Active Grant

• Current Assignee: Canadian Energy Services L.P. (Ces Energy Solutions Corp.)
• Original Assignee: Tech-Star Fluid Systems Inc.
• Inventors: SMITH, CARL KEITH
• Granted Patent: US 9,670,394 B2
• Time in Patent Office: Days
• US Class Current: 175/65
• CPC Class Codes: C09K 8/05 containing inorganic compounds only, e.g. mixtures of clay and salt
• CPC Class Codes: C09K 8/203 Wood derivatives, e.g. lignosulfonate, tannin, tall oil, sulfite liquor
• CPC Class Codes: C09K 8/206 Derivatives of other natural products, e.g. cellulose, starch, sugars
• CPC Class Codes: E21B 21/003 Means for stopping loss of drilling fluid plastering the borehole wall E21B33/138
• CPC Class Codes: E21B 21/062 by mixing components

Abstract

A method for drilling a wellbore into a formation. The method includes: providing a mixed metal-viscosified drilling fluid including at least 1% potassium salt and/or at least 0.05% calcium sulfate; circulating the drilling fluid through the well; and drilling into a formation. An anionic thinner may be added if the clay concentration of the drilling fluid reaches a problematic level to adversely affect pumpability of the fluid.

Claims

1. A method for drilling a well through a formation, the method comprising:

providing a mixed metal-viscosified drilling fluid;

circulating the drilling fluid through the well while drilling into the formation;

identifying a condition of drilling indicative of a problematic increase in the clay concentration of the drilling fluid;

adding a potassium salt to the drilling fluid to bring the concentration to at least 1% w/v potassium salt; and

adding an anionic thinner to the drilling fluid to adjust the viscosity of the drilling fluid.

2. The method of claim 1 wherein providing the mixed metal-viscosified drilling fluid includes providing an aqueous-based drilling fluid including 15 to 45 kg/m3 bentonite, mixed metal viscosifier at a weight ratio of 1:

8 to 1;

12, viscosifier to bentonite and a base to maintain the pH above 10.0.

3. The method of claim 1 wherein adding a potassium salt occurs during the step of providing.

4. The method of claim 1 wherein adding a potassium salt occurs after identifying.

5. The method of claim 1 wherein adding a potassium salt brings the concentration of potassium salt to 1 to 5% w/v.

6. The method of claim 1 wherein providing the mixed metal-viscosified drilling fluid includes:

mixing bentonite in water to form a bentonite mixture;

adding a mixed metal viscosifier to the bentonite mixture;

adjusting pH to greater than pH 10; and

adding the potassium salt.

7. The method of claim 1 further comprising adding any of fluid loss control additives and/or lost circulation materials.

8. The method of claim 1 wherein providing the mixed metal-viscosified drilling fluid provides a drilling fluid with a yield point greater than 10 Pa.

9. The method of claim 1 wherein adding an ionic thinner is initiated after identifying a condition of drilling indicative of a problematic increase in the clay concentration of the drilling fluid.

10. The method of claim 1 wherein adding an ionic thinner brings the fluid yield point to between 10 and 60 Pa.

11. The method of claim 1 wherein circulating the drilling fluid is initiated prior to drilling into a clay deposit.

12. The method of claim 1 wherein circulating the drilling fluid is maintained while a clay deposit is open to the drilling fluid.

13. The method of claim 1 wherein circulating the drilling fluid is initiated substantially at surface.

14. The method of claim 1 wherein identifying includes determining the viscosity of the drilling fluid.

15. The method of claim 1 wherein identifying includes determining the clay concentration in the drilling fluid.

16. The method of claim 1 wherein identifying includes considering the location of the wellbore relative to a known location of a clay deposit.

17. The method of claim 1 wherein a condition of drilling indicative of a problematic increase in the concentration of clay includes at least one of:

a) a funnel viscosity of 70 seconds/quart;

b) a yield point of 60 Pa;

c) for freshwater based fluids, a MBT of ≧

20 ppb;

or

d) for saltwater based fluids, a MBT ≧

40 ppb.

18. The method of claim 1 wherein the anionic thinner is selected from the group consisting of:

coal fines, lignite, lignite resin, sulphomethylated lignite, lignosulfonate, humalite, tannin including sulfonated tannin, sodium asphalt sulfonate, poly-anionic cellulose, penta potassium pyrophosphate (PKPP), sodium acid pyrophosphate, tetra sodium pyrophosphate, sulphomethylated phenolic resin or xanthan gum.

19. The method of claim 1 wherein the potassium salt is selected from the group consisting of potassium sulfate, potassium chloride, potassium acetate and potassium formate.

20. The method of claim 1 wherein the potassium salt is potassium sulfate.

21. The method of claim 1 wherein the potassium salt is potassium chloride.

22. The method of claim 6 wherein the pH is adjusted using caustic soda, caustic potash, potassium carbonate or soda ash.

23. A method for drilling a well through a formation, the method comprising:

providing a mixed metal-viscosified drilling fluid;

circulating the drilling fluid through the well while drilling into the formation;

identifying a condition of drilling indicative of a problematic increase in the clay concentration of the drilling fluid;

adding calcium sulfate to the drilling fluid to bring the concentration to at least 0.05% w/v calcium sulfate in the drilling fluid; and

adding an anionic thinner to the drilling fluid to adjust the viscosity of the drilling fluid.

24. The method of claim 23 wherein providing the mixed metal-viscosified drilling fluid includes providing an aqueous-based drilling fluid including 15 to 45 kg/m3 bentonite, mixed metal viscosifier at a weight ratio of 1:

8 to 1;

12, viscosifier to bentonite and a base to maintain the pH above 10.0.

25. The method of claim 23 wherein adding a calcium sulfate occurs during the step of providing.

26. The method of claim 23 wherein adding a calcium sulfate occurs after identifying.

27. The method of claim 23 wherein adding a calcium sulfate brings the concentration of calcium sulfate to 0.05 to 1.0% w/v.

28. The method of claim 23 wherein providing the mixed metal-viscosified drilling fluid includes:

mixing bentonite in water to form a bentonite mixture;

adding a mixed metal viscosifier to the bentonite mixture;

adjusting pH to greater than pH 10; and

adding the calcium sulfate.

29. The method of claim 23 further comprising adding any of fluid loss control additives and/or lost circulation materials.

30. The method of claim 23 wherein providing the mixed metal-viscosified drilling fluid provides a drilling fluid with a yield point greater than 10 Pa.

31. The method of claim 23 wherein adding an ionic thinner is initiated after identifying a condition of drilling indicative of a problematic increase in the clay concentration of the drilling fluid.

32. The method of claim 23 wherein adding an ionic thinner brings the fluid yield point to between 10 and 60 Pa.

33. The method of claim 23 wherein circulating the drilling fluid is initiated prior to drilling into a clay deposit.

34. The method of claim 23 wherein circulating the drilling fluid is maintained while a clay deposit is open to the drilling fluid.

35. The method of claim 23 wherein circulating the drilling fluid is initiated substantially at surface.

36. The method of claim 23 wherein identifying includes determining the viscosity of the drilling fluid.

37. The method of claim 23 wherein identifying includes determining the clay concentration in the drilling fluid.

38. The method of claim 23 wherein identifying includes considering the location of the wellbore relative to a known location of a clay deposit.

39. The method of claim 23 wherein a condition of drilling indicative of a problematic increase in the concentration of clay includes at least one of:

a) a funnel viscosity of 70 seconds/quart;

b) a yield point of 60 Pa;

c) for freshwater based fluids, a MBT of ≧

20 ppb;

or

d) for saltwater based fluids, a MBT ≧

40 ppb.

40. The method of claim 23 wherein the anionic thinner is selected from the group consisting of:

coal fines, lignite, lignite resin, sulphomethylated lignite, lignosulfonate, humalite, tannin including sulfonated tannin, sodium asphalt sulfonate, poly-anionic cellulose, penta potassium pyrophosphate (PKPP), sodium acid pyrophosphate, tetra sodium pyrophosphate, sulphomethylated phenolic resin or xanthan gum.

41. The method of claim 39 wherein the pH is adjusted using caustic soda, caustic potash, potassium carbonate or soda ash.