Encapsulation and controlled delivery of strong mineral acids

Patent metadata

Field	Value
Publication number	US-2016017215-A1
Application number	US-201414333879-A
Country	US
Kind code	A1
Filing date	Jul 17, 2014
Priority date	Jul 17, 2014
Publication date	Jan 21, 2016
Grant date	—

Abstract

A polymer-encapsulated mineral acid solution and a method for forming the polymer-encapsulated mineral acid solution. Introducing a strong mineral acid solution to a monomer solution occurs such that a primary emulsion that is a water-in-oil type emulsion forms. Introducing the primary emulsion to a second aqueous solution forms a secondary emulsion that is a water-in-oil-in-water type double emulsion. The monomer in the secondary emulsion is cured such a polymerized shell forms that encapsulates the strong mineral acid solution and forms the capsule. The strong mineral acid solution has up to 30 wt. % strong mineral acid. A method of stimulating a hydrocarbon-bearing formation using the polymer-encapsulated mineral acid solution includes introducing a capsule suspension into a fissure in the hydrocarbon-bearing formation to be stimulated through a face in a well bore. The capsule is maintained within the fissure until the polymer shell degrades.

First claim

What is claimed is:

1 . A method for forming a polymer-encapsulated mineral acid solution, the method comprising the steps of:
introducing a strong mineral acid solution to a monomer solution such that a primary emulsion forms, where the primary emulsion is a water-in-oil (W/O) type emulsion, where the strong mineral acid solution comprises a strong mineral acid that is in a range of from greater than 0 wt. % to 30 wt. % of the strong mineral acid solution, where the monomer solution comprises a monomer and a free-radical initiator, and where the monomer is hydrophobic and is operable to polymerize upon initiation of a free-radical chain polymerization reaction; introducing the primary emulsion to a second aqueous solution such that a secondary emulsion forms, where the secondary emulsion is a water-in-oil-in-water (W/O/W) type double emulsion; and converting the free-radical initiator in the monomer solution such that a free-radical chain polymerization reaction is initiated in the monomer solution, the polymerized shell forms, and the secondary emulsion converts into the polymer-encapsulated mineral acid solution, where the polymerized shell encapsulates the strong mineral acid solution and prevents interaction with the strong mineral acid solution until the polymerized shell degrades, and where the strong mineral acid solution does not degrade the polymerized shell.

2 . The method of claim 1 where the strong mineral acid is selected from the group consisting of hydrochloric acid (HCl), hydrofluoric acid (HF), sulfuric acid (H 2 SO 4 ), nitric acid (HNO 3 ) and combinations thereof.

3 . The method of claim 1 where the monomer solution comprises a monomer having acrylate end group functionality.

4 . The method of claim 1 where the monomer solution comprises a monomer having methacrylate end group functionality.

5 . The method of claim 1 where the monomer solution has a density that is not substantially different than the density of the strong mineral acid solution.

6 . The method of claim 1 where the monomer solution has a viscosity that is not substantially different than the viscosity of the strong mineral acid solution.

7 . The method of claim 1 where the free-radical initiator is a photo-initiator.

8 . The method of claim 1 where the secondary aqueous solution further comprises an acid.

9 . The method of claim 8 where the secondary aqueous solution has a negative ion concentration that is not substantially different than the negative ion concentration of the strong mineral acid solution.

10 . The method of claim 1 where the secondary aqueous solution further comprises a salt.

11 . The method of claim 10 where the secondary aqueous solution has a negative anion concentration that is not substantially different than the negative ion concentration of the strong mineral acid solution.

12 . The method of claim 1 where converting the free-radical initiator in the monomer solution occurs by introducing electromagnetic energy into the secondary emulsion.

13 . A polymer-encapsulated mineral acid solution comprising:
a strong mineral acid solution where the strong mineral acid is in a range of from greater than 0 wt. % to about 30 wt. % of the solution; and a polymerized shell that encapsulates the strong mineral acid solution such that the polymerized shell encapsulates and prevents interaction with the strong mineral acid solution until the polymerized shell degrades, where the strong mineral acid solution does not degrade the polymerized shell.

14 . The capsule of claim 13 where the strong mineral acid is selected from the group consisting of hydrochloric acid (HCl), hydrofluoric acid (HF), sulfuric acid (H 2 SO 4 ), nitric acid (HNO 3 ) and combinations thereof.

15 . The capsule of claim 13 where the polymerized shell comprises a polyacrylate homopolymer.

16 . The capsule of claim 13 where the polymerized shell comprises a polymethacrylate homopolymer.

17 . The capsule of claim 13 where the polymerized shell comprises polymerized monomer having acrylate end group functionality.

18 . The capsule of claim 13 where the polymerized shell comprises polymerized monomer having methacrylate end group functionality.

19 . The capsule of claim 13 where the polymerized shell is the resultant of a free-radical chain polymerization reaction.

20 . The capsule of claim 13 where the polymerized shell has a glass transition temperature (T g ) and the T g is in a range of from 43° C. to 151° C.

21 . The capsule of claim 13 where the polymerized shell does not have a glass transition temperature (T g ).

22 . A polymer-encapsulated mineral acid solution suspension comprising:
a polymer-encapsulated mineral acid solution, comprising:
a strong mineral acid solution where the acid is in a range of from greater than 0 wt. % to about 30 wt. % of the solution, and
a polymerized shell that encapsulates the strong mineral acid solution such that the polymerized shell contains the strong mineral acid solution and prevents interaction with the strong mineral acid solution until the polymerized shell degrades, where the strong mineral acid solution does not degrade the polymerized shell; and
a suspension fluid.

23 . The solution of claim 22 where the polymerized shell has a glass transition temperature (T g ) and where the suspension fluid has a temperature that is less than T g .

24 . The solution of claim 22 where the suspension fluid is a brine.

25 . A method of stimulating a hydrocarbon-bearing formation using a polymer-encapsulated mineral acid solution, the method comprising:
introducing a polymer-encapsulated mineral acid solution suspension into a fissure traversing the hydrocarbon-bearing formation to be stimulated; and maintaining the polymer-encapsulated mineral acid solution within the fissure such that the polymer shell degrades within the fissure, the strong mineral acid solution is released into the fissure of the hydrocarbon-bearing formation, and the hydrocarbon-bearing formation is stimulated, where the polymer-encapsulated mineral acid solution suspension comprises a suspension fluid and a polymer-encapsulated mineral acid solution, where the polymer-encapsulated mineral acid solution comprises:
a strong mineral acid solution where the acid is in a range of from greater than 0 wt. % to about 30 wt. % of the solution, and
a polymerized shell that encapsulates the strong mineral acid solution such that the polymerized shell contains the strong mineral acid solution and prevents interaction with the strong mineral acid solution until the polymerized shell degrades, where the strong mineral acid solution does not degrade the polymerized shell; and
where the well bore is defined by a well bore wall and traverses the hydrocarbon-bearing formation, where the face is a portion of the well bore wall associated with and operable to provide fluid communication between the hydrocarbon-bearing formation and the well bore, and where the fissure in the hydrocarbon-bearing formation is accessible through the face.

26 . The method of claim 25 where the polymerized shell has a glass transition temperature (T g ) and where the introduced polymer-encapsulated mineral acid solution suspension has a temperature that is less than T g .

Assignees

• Aramco Services Co
• Rti Internat

Inventors

• Al-Muntasheri Ghaithan
• Rothrock Ginger Denison
• Johnson Leah M
• Shepherd Sarah

Classifications

• C09K8/725

  Compositions containing polymers · CPC title

• E21B43/25

  Methods for stimulating production {(by vibrating earth formations E21B43/003)} · CPC title

• C09K8/882 Primary

  obtained by reactions only involving carbon-to-carbon unsaturated bonds · CPC title

• C09K8/92

  characterised by their form or by the form of their components, e.g. encapsulated material (C09K8/70 takes precedence) · CPC title

• C09K8/82

  Oil-based compositions (C09K8/64 takes precedence) · CPC title