Encapsulated breaker chemical

• US 5,102,558 A
• Filed: 01/04/1991
• Issued: 04/07/1992
• Est. Priority Date: 12/14/1989
• Status: Expired due to Fees

• Current Assignee: Exxon Research and Engineering Company (Exxon Mobil Corporation)
• Original Assignee: Exxon Research and Engineering Company (Exxon Mobil Corporation)
• Inventors: Drake, Evelyn N., Manalastas, Pacifico V., Newlove, John C., McDougall, Lee A.
• Primary Examiner(s): Stoll, Robert L.
• Assistant Examiner(s): SAYALA, CHHAYA D
• Application Number:
  US07/637,401
• Time in Patent Office: 459 Days
• Field of Search: 252/8.551, 252/8.553, 252/186.32, 252/330, 252/358, 166/308, 428/402.22, 427/213
• US Class Current: 507/260
• CPC Class Codes: C09K 8/62 Compositions for forming crevices or fractures
• CPC Class Codes: C09K 8/92 characterised by their form or by the form of their components, e.g. encapsulated material C09K8/70 takes precedence
• CPC Class Codes: Y10S 507/902 Controlled release agent
• CPC Class Codes: Y10S 507/921 Specified breaker component for emulsion or gel
• CPC Class Codes: Y10S 507/922 Fracture fluid
• CPC Class Codes: Y10T 428/2987 Addition polymer from unsaturated monomers only

Abstract

An encapsulated breaker chemical composition used in a fracturing process in the protection of an oil or gas stimulation operation which comprises: a breaker chemical; and a pinhole free coating of a neutralized sulfonated elastomeric polymer of about 2 to about 80 microns thick deposited onto the surface of the breaker chemical, wherein said neutralized sulfonated polymer encapsulates the breaker chemical, wherein the neutralized sulfonated polymer is permeable to the breaker chemical and the neutralized sulfonated polymer is non-reactive to the breaker chemical.

Claims

1. An encapsulated breaker chemical composition used in an oil or gas operation which comprises:

(a) a particulate breaker chemical; and

(b) a coating substantially free of pinholes comprising a neutralized sulfonated elastomeric polymer having a thickness of at least about 1 micron deposited onto the surface of particles of said breaker chemical, wherein said neutralized sulfonated polymer encapsulates said breaker chemical, wherein said neutralized sulfonated polymer is essentially impermeable to said breaker chemical under conditions of use and said neutralized sulfonated polymer is non-reactive to said breaker chemical.

2. The encapsulated breaker chemical composition of claim 1 wherein said elastomeric polymer is selected from the group consisting of sulfonated copolymers of ethylene and propylene, sulfonated terpolymers of ethylene, propylene and a diene, sulfo Butyl rubber, sulfo isoprene/styrene rubber, sulfo isoprene/butadiene rubber, sulfo isoprene/butadiene/styrene copolymers, sulfo isobutylene/styrene copolymers, sulfo isobutylene/para methyl styrene copolymers, and complexes of the aforementioned polymers with a vinyl pyridine copolymer.

3. The encapsulated breaker chemical composition of claim 1 wherein said coating has a thickness within the range of from about 2 to about 80 microns.

4. The encapsulated breaker chemical composition of claim 3 wherein said neutralized sulfonated elastomeric polymer is a neutralized sulfonated EPDM terpolymer.

5. The encapsulated breaker chemical composition of claim 1 wherein the acid groups of said sulfonated elastomeric polymer are at least about 50% neutralized.

6. The encapsulated breaker chemical composition of claim 5 wherein the acid groups of said sulfonated elastomeric polymer are about 100% neutralized.

7. The encapsulated breaker chemical composition of claim 5 wherein the acid groups of said sulfonated elastomeric polymer are neutralized with an ion selected from the group consisting of zinc or sodium.

8. The encapsulated breaker chemical composition of claim 1 wherein said breaker chemical is coated on a seed particle which is essentially chemically inert with respect to said breaker chemical.

9. The encapsulated breaker chemical composition of claim 8 wherein said seed particle comprises urea.

10. The encapsulated breaker chemical composition of claim 1 wherein said breaker chemical is selected from the group consisting of ammonium persulfate, potassium persulfate, sodium persulfate, sodium chlorite and mixtures thereof.

11. The encapsulated breaker chemical composition of claim 1 wherein said breaker chemical is selected from the group consisting of sulfamic acid, oxalic acid, citric acid, ammonium sulfate, sodium acetate and mixtures thereof.

12. The encapsulated breaker chemical composition of claim 1 wherein said breaker chemical is selected from the group consisting of ammonium bifluoride, potassium fluoride, sodium fluoride and mixtures thereof.

13. The encapsulated breaker chemical composition of claim 1 wherein said breaker chemical is an enzyme.

14. The encapsulated breaker chemical composition of claim 4 wherein said EPDM terpolymer contains copolymerized ethylidene norbornene.

15. The encapsulated breaker chemical composition of claim 4 wherein said coating has a thickness in the range of from about 2 to about 80 microns.

16. The encapsulated breaker chemical composition of claim 1 wherein said sulfonated elastomeric polymer contains from about 4 to about 200 milliequivalents of pendant sulfonate groups per 100 g of polymer.

17. The composition of claim 1 wherein said encapsulated breaker chemical is further overcoated with a layer of thermoplastic polymer.

18. The composition of claim 17 wherein said thermoplastic polymer is a neutralized sulfonated styrene polymer.

19. The composition of claim 17 wherein the thickness of said layer of thermoplastic polymer is within the range of from about 1 to about 20 microns.

20. A fracturing fluid comprising a carrier fluid, a viscosifying polymer or oil and an encapsulated breaker chemical as defined in claims 1, 4, 8, or 17.

21. A process for fracturing subterranean formations comprising injecting under pressure a fracturing fluid into the subterranean formation, said fracturing fluid comprising a carrier fluid, a viscosifying polymer or oil and an encapsulated breaker chemical as defined in claims 1, 4, 8, or 17.