DRILLING FLUID

• US 20180223154A1
• Filed: 04/10/2018
• Published: 08/09/2018
• Est. Priority Date: 08/26/2010
• 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
• Granted Patent: US 10,280,353 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 8/16 characterised by the inorganic compounds other than clay
• 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 drilling fluid and method for drilling in a coal containing formation with a mixed metal-viscosified drilling fluid including at least 0.05% calcium sulfate.

Claims

1-12. -12. (canceled)

13. A drilling fluid comprising:

an aqueous mixture of bentonite and a mixed metal viscosifier with a pH above about pH 10; and

at least 0.05% calcium sulfate (w/v).

14. The drilling fluid of claim 13 wherein the drilling fluid comprises 15 to 50 kg/m3 bentonite, mixed metal viscosifier at a weight ratio of 1:

8 to 1;

12, viscosifier to bentonite, a base to maintain the pH above about 10.0 and the at least 0.05% calcium sulfate.

15. The drilling fluid of claim 13 wherein the drilling fluid comprises 25 to 45 kg/m3 bentonite, mixed metal viscosifier at a weight ratio of 1:

9.5 to 1;

10.5, viscosifier to bentonite, a base to maintain the pH between about 10.5 to 13 and about 0.05 to 1.0% calcium sulfate.

16. The drilling fluid of claim 13 wherein the drilling fluid comprises about 30 to 40 kg/m3 bentonite, a mixed metal viscosifier in a quantity of about 1:

10 MMO, MMH or MMOH to bentonite with a pH controlled to greater than pH 11 and 0.1 to 0.5% calcium sulfate.

17. The drilling fluid of claim 13 wherein the drilling fluid is prepared by:

mixing bentonite in water to form a bentonite mixture;

adding a mixed metal viscosifier to the bentonite mixture;

adjusting pH to greater than about pH 10;

adding the calcium sulfate.

18. The drilling fluid of claim 13 further comprising at least one of a fluid loss control additive and/or a lost circulation material.

19. The drilling fluid of claim 13 wherein the drilling fluid includes a yield point of greater than 10 Pa.

20. The drilling fluid of claim 13 wherein the calcium sulfate is in the form of gypsum.

21. The drilling fluid of claim 13 wherein the calcium sulfate concentration is 0.5 to 50 kg/m3.

22. The drilling fluid of claim 13 further comprising an amount of potassium salt selected from the group consisting of potassium sulfate, potassium chloride, potassium acetate and potassium formate.

23. The drilling fluid of claim 13 wherein the pH is adjusted using caustic soda or caustic potash.

24. The drilling fluid of claim 13 wherein the bentonite is in the form of untreated bentonite.