Drilling fluid

• US 10,280,353 B2
• Filed: 04/10/2018
• Issued: 05/07/2019
• 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:
  US15/949,393
• Publication Number:
  US 20180223154A1
• Time in Patent Office: 392 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 drilling fluid consisting essentially of:

an aqueous mixture of 15 to 50 kg/m3 bentonite and a mixed metal viscosifier at a weight ratio of 1;

8 to 1;

12 viscosifier to bentonite, the mixed metal viscosifier being of the following empirical formula;

Li_mD_dT(OH)_(m+2d+3+na)A_aⁿ, where;

m represents the number of Li ions present;

D represents divalent metal ions selected from Mg, Ca, Ba, Sr, Mn, Fe, Co, Ni,

Cu, Zn or mixtures thereof;

d is the number of ions of D in the formula and is from 0 to 4;

T represents trivalent metal ions selected from Al, Ga, Cr or Fe;

A represents monovalent or polyvalent anions selected from;

halide, sulfate,

nitrate, phosphate, carbonate or hydrophilic organic ions selected

from alveolate, lignosulfate, polvcarboxvlate, or polvacrylates;

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;

a base to maintain a pH of the mixture above about 10; and

0.1 to 1.0% calcium sulfate (w/v), the drilling fluid having a yield point of greater than 10Pa.

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

9.5 to 1;

10.5 viscosifier to bentonite, and the base maintaining the pH between about 10.5 to 13.

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

10 mixed metal viscosifier to bentonite with the pH controlled to greater than 11 and 0.1 to 0.5% calcium sulfate.

4. The drilling fluid of claim 1 wherein the drilling fluid is prepared by:

mixing the bentonite in water to form a bentonite mixture;

adding the mixed metal viscosifier to the bentonite mixture;

adjusting the pH to greater than about 10; and

adding the calcium sulfate.

5. The drilling fluid of claim 1 further comprising at least one of a fluid loss control additive and/or a lost circulation material.

6. The drilling fluid of claim 1 wherein the calcium sulfate is in the form of gypsum.

7. The drilling fluid of claim 1 further comprising an amount of potassium salt selected from the group consisting of potassium sulfate, potassium chloride, potassium acetate and potassium formate.

8. The drilling fluid of claim 1 wherein the pH is adjusted using caustic soda or caustic potash.

9. The drilling fluid of claim 1 wherein the bentonite is in the form of untreated bentonite.