Drilling fluid and method for drilling in coal-containing formations

• US 9,969,920 B2
• Filed: 11/10/2016
• Issued: 05/15/2018
• 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
• Primary Examiner(s): Hutton, Jr., William D
• Assistant Examiner(s): Skaist, Avi T
• Application Number:
  US15/348,629
• Publication Number:
  US 20170058178A1
• Time in Patent Office: 551 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. A method for producing a mixed metal-viscosified drilling fluid comprising an aqueous mixture of bentonite, a mixed metal viscosifier, and calcium sulfate (w/v), the method comprising:

mixing water, the bentonite and the mixed metal viscosifier;

monitoring rheology of the mixed metal-viscosified drilling fluid; and

,

adding the calcium sulfate in an amount of at least 0.05% (w/v) to the mixed metal-viscosified drilling fluid to avoid adverse rheological changes, wherein the calcium sulfate is added to protect an electrostatic interaction between the bentonite and the mixed metal-viscosifier, thereby maintaining the viscosity of the drilling fluid at a yield point of greater than 10 Pa.

2. The method of claim 1 wherein mixing includes 15 to 50 kg/m3 bentonite, the mixed metal viscosifier at a weight ratio of 1:

8 to 1;

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

3. The method of claim 2 wherein mixing includes about 25 to 45 kg/m3 bentonite and the mixed metal viscosifier in a quantity of about 1:

10 of mixed metal viscosifier to bentonite with a pH controlled to greater than pH 11.

4. The method of claim 1 wherein adding includes adding 0.05 to 1.0% calcium sulfate.

5. The method of claim 1 wherein mixing includes:

mixing bentonite in water to form a bentonite mixture;

adding a mixed metal viscosifier to the bentonite mixture; and

adjusting pH to greater than about pH 10.

6. The method of claim 5 further comprising adding any of fluid loss control additives and/or lost circulation materials.

7. The method of claim 1 wherein adverse rheological changes includes viscosity thinning.

8. The method of claim 1 wherein adding is conducted prior to drilling into a coal seam.

9. The method of claim 1 wherein adding is conducted prior to initiating the drilling process.

10. The method of claim 1 wherein the calcium sulfate is in the form of gypsum.

11. The method of claim 1 wherein the mixed metal viscosifier is an inorganic particle based on magnesium/aluminum oxides and/or hydroxides.

12. The method of claim 1 wherein the mixed metal viscosifier is a mixed metal layered hydroxide compound of the following formula:

Li_mD_dT(OH)_(m+2d+3+na)A_aⁿ,

where

m represents the number of Li ions present (preferably

     0);

D represents divalent metal ions such as Mg, Ca, Ba, Sr, Mn, Fe, Co, Ni, Cu, Zn, most preferably Mg, or mixtures thereof;

d is the number of ions of D in the formula, preferably from 0 to about 4, and most preferably about 1;

T represents trivalent metal ions and may be Al, Ga, Cr or Fe, preferably Al;

A represents monovalent or polyvalent anions other than OH ions and may be inorganic ions such as;

halide, sulfate, nitrate, phosphate, carbonate, most preferably halide, sulfate, phosphate, or carbonate, or they may be hydrophilic organic ions such as glycolate, lignosulfate, polycarboxylate, or polyacrylates;

a is the number of ions of A in the formula;

n is the valence of A; and

(m+2d+3+na) is equal to or greater than 3.