DRILL FLUID AND METHOD FOR TUNNELING

• US 20190316019A1
• Filed: 06/22/2018
• Published: 10/17/2019
• Est. Priority Date: 03/02/2007
• Status: Active Grant

• Current Assignee: Canadian Energy Services L.P. (Ces Energy Solutions Corp.)
• Original Assignee: Canadian Energy Services L.P. (Ces Energy Solutions Corp.)
• Inventors: SMITH, Carl Keith, GAWRYLUK, Josh
• Granted Patent: US 11,155,742 B2
• Time in Patent Office: Days
• 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 tunnel through a formation must address environmental concerns. One tunneling method comprises the steps of: preparing a mixed metal-viscosified drilling fluid including bentonite, a mixed metal viscosifier and controlling pH to 8.5 to 9.5 to permit a reaction between the bentonite and the mixed metal viscosifier; adding at least one of: (i) calcium sulfate and (ii) a potassium salt; and pumping the drilling fluid while drilling the tunnel with the pH lowered to 7-9. The amount of mixed metal viscosifier used can be limited such that the weight ratio of mixed metal viscosifier to MBT reaches up to 1:30. In the event that there is a problematic increase in viscosity, a non-toxic anionic thinner can be added to the drilling fluid. One such anionic thinner is a polyacrylate.

Claims

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

preparing a mixed metal-viscosified drilling fluid including bentonite, a mixed metal viscosifier and controlling pH to 8.5 to 9.5 to permit a reaction between the bentonite and the mixed metal viscosifier;

adding at least one of;

(i) calcium sulfate and (ii) a potassium salt; and

pumping the drilling fluid while drilling the tunnel with the pH lowered to 7-9.

2. The method of claim 1 wherein preparing the mixed metal-viscosified drilling fluid includes mixing water, 15 to 45 kg/m3 bentonite and the mixed metal viscosifier at a weight ratio of 1:

3 to 1;

20, viscosifier to bentonite, and pumping proceeds with a clay load increasing from incorporated clay such that the weight ratio of the mixed metal viscosifier;

total clay is up to 1;

30.

3. The method of claim 1 wherein the potassium salt is selected from potassium sulfate or potassium chloride and adding adds the potassium salt for a concentration of 1 to 5% w/v.

4. The method of claim 1 wherein adding brings the calcium sulfate to 0.05 to 1.0% w/v.

5. The method of claim 1 further comprising adding a non-toxic anionic thinner when the drilling fluid shows a problematic increase in viscosity as indicated by:

a) a funnel viscosity of 70 seconds/L;

b) a yield point of 30 Pa;

or

c) an MBT of 60 kg/m3.

6. The method of claim 1 wherein the non-toxic anionic thinner is selected from the group consisting of:

coal fines, lignite, lignite resin, humalite, poly-anionic cellulose, tetra potassium pyrophosphate (TKPP), sodium acid pyrophosphate, tetra sodium pyrophosphate, polyacrylic acid, polyacrylates, polyacrylate co-polymers or xanthan gum.

7. The method of claim 1 further comprising adding a polyacrylate anionic thinner when the drilling fluid shows a problematic increase in viscosity as indicated by:

a) a funnel viscosity of 70 seconds/L;

b) a yield point of 30 Pa;

or

c) an MBT of 60 kg/m3.

8. The method of claim 1 wherein:

preparing the mixed metal-viscosified drilling fluid includes mixing water, 15 to 45 kg/m3 bentonite and the mixed metal viscosifier at a weight ratio of 1;

3 to 1;

20, viscosifier to bentonite,

pumping proceeds with a clay load increasing from incorporated drilled clay and limited addition of further mixed metal viscosifier such that the weight ratio of the mixed metal viscosifier;

total clay is up to 1;

30; and

further comprising adding humalite or a polyacrylate anionic thinner when the drilling fluid shows a problematic increase in viscosity as indicated by;

a) a funnel viscosity of 70 seconds/L;

b) a yield point of 30 Pa;

or

c) an MBT of 60 kg/m3.

9. A method for drilling a tunnel through a formation, the method comprising:

providing a mixed metal-viscosified drilling fluid;

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

monitoring the drilling fluid for a condition of drilling indicative of a problematic increase in viscosity of the drilling fluid;

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

adding a non-toxic anionic thinner to the drilling fluid to adjust the viscosity of the drilling fluid.

10. The method of claim 9 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:

3 to 1;

30, viscosifier to bentonite and a base to maintain the pH above 7.0.

11. The method of claim 9 wherein adding a potassium salt occurs during the step of providing.

12. The method of claim 9 wherein adding a potassium salt occurs after identifying the condition of drilling indicative of a problematic increase in viscosity of the drilling fluid.

13. The method of claim 9 wherein adding a potassium salt brings the concentration of potassium salt to 1 to 5% w/v.

14. The method of claim 9 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 pH 8.5-9.5; and

adding the potassium salt.

15. The method of claim 9 further comprising adding any of fluid loss control additives and/or lost circulation materials.

16. The method of claim 9 wherein providing the mixed metal-viscosified drilling fluid provides a drilling fluid with a yield point greater than 10 Pa.

17. The method of claim 9 wherein adding an anionic thinner is initiated after identifying the condition of drilling indicative of a problematic increase in viscosity of the drilling fluid.

18. The method of claim 9 wherein adding an anionic thinner brings the fluid yield point to between 10 and 60 Pa.

19. The method of claim 9 wherein circulating the drilling fluid is initiated prior to drilling into a clay deposit.

20. The method of claim 9 wherein circulating the drilling fluid is maintained while a clay deposit is open to the drilling fluid.

21. The method of claim 9 wherein circulating the drilling fluid is initiated substantially at surface.

22. The method of claim 9 wherein monitoring includes determining the viscosity of the drilling fluid.

23. The method of claim 9 wherein monitoring includes determining the clay concentration in the drilling fluid.

24. The method of claim 9 wherein monitoring includes considering the location of the tunnel relative to a known location of a clay deposit.

25. The method of claim 9 wherein the condition of drilling indicative of a problematic increase in viscosity includes at least one of:

a) a funnel viscosity of 70 seconds/L;

b) a yield point of 30 Pa; and

c) an MBT of 60 kg/m3.

26. The method of claim 9 wherein the non-toxic anionic thinner is selected from the group consisting of:

coal fines, lignite, lignite resin, humalite, poly-anionic cellulose, tetra potassium pyrophosphate (TKPP), sodium acid pyrophosphate, tetra sodium pyrophosphate, polyacrylic acid, polyacrylates, polyacrylate co-polymers or xanthan gum.

27. The method of claim 9 wherein the potassium salt is selected from the group consisting of potassium sulfate, potassium chloride, potassium acetate and potassium formate.

28. The method of claim 9 wherein the potassium salt is potassium sulfate.

29. The method of claim 9 wherein the potassium salt is potassium chloride.

30. The method of claim 14 wherein the pH is adjusted using lime.

31. A method for drilling a tunnel through a formation, the method comprising:

providing a mixed metal-viscosified drilling fluid;

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

monitoring the drilling fluid for a condition of drilling indicative of a problematic increase in viscosity 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 a non-toxic anionic thinner to the drilling fluid to adjust the viscosity of the drilling fluid.

32. The method of claim 31 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:

3 to 1;

30, viscosifier to bentonite and a base to maintain the pH above 7.0.

33. The method of claim 31 wherein adding a calcium sulfate occurs during the step of providing.

34. The method of claim 31 wherein adding a calcium sulfate occurs after identifying the condition of drilling indicative of a problematic increase in viscosity of the drilling fluid.

35. The method of claim 31 wherein adding calcium sulfate brings the concentration of calcium sulfate to 0.05 to 1.0% w/v.

36. The method of claim 31 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 pH 8.5-9.5; and

adding the calcium sulfate.

37. The method of claim 31 further comprising adding any of fluid loss control additives and/or lost circulation materials.

38. The method of claim 31 wherein providing the mixed metal-viscosified drilling fluid provides a drilling fluid with a yield point greater than 10 Pa.

39. The method of claim 31 wherein adding an anionic thinner is initiated after identifying the condition of drilling indicative of a problematic increase in viscosity of the drilling fluid.

40. The method of claim 31 wherein adding an anionic thinner brings the fluid yield point to between 10 and 60 Pa.

41. The method of claim 31 wherein circulating the drilling fluid is initiated prior to drilling into a clay deposit.

42. The method of claim 31 wherein circulating the drilling fluid is maintained while a clay deposit is open to the drilling fluid.

43. The method of claim 31 wherein circulating the drilling fluid is initiated substantially at surface.

44. The method of claim 31 wherein monitoring includes determining the viscosity of the drilling fluid.

45. The method of claim 31 wherein monitoring includes determining the clay concentration in the drilling fluid.

46. The method of claim 31 wherein monitoring includes considering the location of the tunnel relative to a known location of a clay deposit.

47. The method of claim 31 wherein a condition of drilling indicative of a problematic increase in viscosity includes at least one of:

a) a funnel viscosity of 70 seconds/L;

b) a yield point of 30 Pa; and

c) an MBT of 60 kg/m3.

48. The method of claim 31 wherein the non-toxic anionic thinner is selected from the group consisting of:

coal fines, lignite, lignite resin, humalite, poly-anionic cellulose, tetra potassium pyrophosphate (TKPP), sodium acid pyrophosphate, tetra sodium pyrophosphate, polyacrylic acid, polyacrylates, polyacrylate co-polymers or xanthan gum.

49. The method of claim 47 wherein the pH is adjusted using lime.

50. A mixed metal-viscosified drilling fluid comprising:

water;

15 to 45 kg/m3 bentonite;

a mixed metal viscosifier at a weight ratio of 1;

3 to 1;

30, viscosifier to bentonite;

at least 0.05% w/v calcium sulfate and/or at least 1% w/v potassium salt;

a polyacrylate anionic thinner; and

a base to maintain the pH above 7.0.

51. The mixed metal-viscosified drilling fluid of claim 50 wherein the polyacrylate anionic thinner is selected from polyacrylic acid, polyacrylate or polyacrylate co-polymer.