Dual-Mechanism Thickening Agents for Hydraulic Fracturing Fluids

• US 20150218438A1
• Filed: 08/30/2013
• Published: 08/06/2015
• Est. Priority Date: 04/23/2009
• Status: Active Grant

• Current Assignee: Pilot Polymer Technologies Incorporated
• Original Assignee: ATRP Solutions, Inc. (Pilot Chemical Corp.)
• Inventors: McCarthy, Patrick, Liao, Yuanxi, Huang, Liang
• Granted Patent: US 9,783,628 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: C08F 220/06 Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• CPC Class Codes: C08F 220/14 Methyl esters , e.g. methyl (meth)acrylate
• CPC Class Codes: C08F 220/325 containing glycidyl radical, e.g. glycidyl (meth)acrylate
• CPC Class Codes: C09K 8/035 Organic additives
• CPC Class Codes: C09K 8/64 Oil-based compositions
• CPC Class Codes: C09K 8/685 containing cross-linking agents
• CPC Class Codes: C09K 8/887 containing cross-linking agents

Abstract

The present invention relates to multi-arm star macromolecules which are used as thickening agents or rheology modifiers, including use in hydraulic fracturing fluid compositions. In one aspect of the invention, a star macromolecule is capable of thickening via a dual mechanism comprising (1) self-assembly of the hydrophobic polymerized segments of the star macromolecules via hydrophobic interactions or associations, and (2) association, reaction, or combination of the hydroxyl-containing polymerized segments of one or more of the star macromolecules.

Claims

1. A star macromolecule represented by Formula (I):

2. The star macromolecule of claim 1, wherein the one or more star macromolecules have a molecular weight of between 150,000 g/mol and 5,000,000 g/mol.

3. The star macromolecule of claim 1, wherein the sum total number of arms (r+t) is between 3 and 1000, or the sum total number of arms (s+t) is between 3 and 1000, or both sum total number of arms (r+t) and sum total number of arms (s+t) are each between 3 and 1000.

4. The star macromolecule of claim 1, wherein the molar ratio of r to t is in the range of between 8:

1 and 3;

1, or the molar ratio of s to t is in the range of between 8;

1 and 3;

1, or both the molar ratio of r to t and the molar ratio of s to t are each in the range of between 8;

1 and 3;

1.

5. The star macromolecule of claim 1, wherein:

i) both q2 and q3 have a value greater than 100, and q2 is greater than q3;

or

ii) both q5 and q3 have a value greater than 100, and q5 is greater than q3;

or

iii) both q2 and q3 have a value greater than 100, and q5 and q3 have a value greater than 100, and q2 and q5 are greater than q3.

6. The star macromolecule of claim 1, wherein the core comprises a hydrophobic crosslinked polymeric segment.

7. The star macromolecule of claim 1, wherein the star macromolecule is a water soluble mikto star macromolecule.

8. The star macromolecule of claim 1, wherein the star macromolecule, when dissolved in water at a concentration of at least 0.2 wt. %, forms a clear, homogeneous gel having a viscosity of at least 20,000 cP.

9. A star macromolecule composition, comprising at least 0.05 wt. % of the star macromolecule of claim 1.

10. The star macromolecule composition of claim 9, wherein the composition is a fracturing fluid thickening additive, a drilling well fluid thickening additive, a gelling agent, or an additive to improve oil extraction from oil sands.

11. The star macromolecule composition of claim 10, wherein the composition is a rheology-modifying composition having a shear-thinning value of at least 6.

12. The star macromolecule composition of claim 10, wherein the composition further comprises one or more boric acid additives or borate-type additives.

13. The star macromolecule composition of claim 10, wherein the composition comprises predominantly star macromolecules having a molecular weight within 5% of the molecular weight of the pre-determined star macromolecule represented by Formula (I), relative to the total star macromolecules in the composition.

20. A process of preparing a star macromolecule represented by Formula (I) of claim 1, wherein the star macromolecule represented by Formula (I) is prepared by one or more star macromolecule processes, comprising:

one-pot process, the arm first process, ATRP, CRP, RAFT, TEMPO, Nitroxide, LRP, CRP, anionic polymerization, cationic polymerization, or combinations thereof.

14. A dual-mechanism thickening agent, comprising a star macromolecule having a molecular weight of between 150,000 g/mol and 5,000,000 g/mol that forms a homogeneous gel when dissolved in water at a concentration of at least 0.05 wt. %;

wherein the gel has;

i) a dynamic viscosity of at least 20,000 cP;

ii) a salt-induced break value of at least 60%;

iii) a shear-thinning value of at least 10;

iv) an increase in dynamic viscosity of at least 5,000 cP in a 0.2 wt. % Borax aqueous solution, according to Borate-Crosslinker Thickening Test;

or

v) combinations thereof.

15. The thickening agent of claim 14, wherein the gel-forming star macromolecule has an increase in dynamic viscosity in the range of between 5,000 cP to 30,000 cP, or an increase in dynamic viscosity of at least 12%, in a 0.2 wt. % Borax aqueous solution, according to the Borate-Crosslinker Thickening Test, relative to the dynamic viscosity of a homogeneuous gel of the star macromolecule with 0.0 wt. % Borax aqueous solution.

16. The thickening agent of claim 14, wherein the gel-forming star macromolecule has a viscosity of less than 5,000 cP at a shear rate of 4 sec⁻

1.

17. The thickening agent of claim 14, wherein the gel-forming star macromolecule has a PDI in the range of between 1.0 to 8.0.

18. The thickening agent of claim 14, wherein the gel-forming star macromolecule is a water-soluble mikto star macromolecule.

19. The thickening agent of claim 14, wherein the arms of the gel-forming star macromolecule comprise:

i) hydrophilic polymeric arms;

ii) copolymeric arms, comprising;

a) hydrophilic polymeric segments and predominantly hydrophobic polymeric segments; and

b) hydrophilic polymeric segments and predominantly hydroxyl-containing polymeric segments.