Preventing flow through subterranean zones

• US 20030181543A1
• Filed: 03/12/2003
• Published: 09/25/2003
• Est. Priority Date: 10/26/2000
• Status: Active Grant

• Current Assignee: Baireddy R. Reddy, Larry S. Eoff
• Original Assignee: Baireddy R. Reddy, Larry S. Eoff
• Inventors: Eoff, Larry S., Reddy, Baireddy R.
• Granted Patent: US 6,843,841 B2
• Time in Patent Office: Days
• US Class Current: 523/130
• CPC Class Codes: C09K 8/5083 obtained by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: C09K 8/512 containing cross-linking agents
• CPC Class Codes: C09K 8/514 of natural origin, e.g. polysaccharides, cellulose C09K8/512 takes precedence
• CPC Class Codes: Y10S 507/903 Crosslinked resin or polymer

Abstract

The present invention provides methods of preventing the flow of water or gas or both through a subterranean zone having a high temperature and a depth such that a long pumping time is required to place a sealing composition therein. The methods basically comprise the steps of preparing a polymeric sealing composition comprised of water, a cross-linking agent and a selected water-soluble polymer which reacts with the cross-linking agent and forms a sealing gel which is stable for a desired period of time at the temperature of the zone and has a pumping time before gelation in the presence of the cross-linking agent whereby the composition can be pumped to the depth of the zone and placed therein. Thereafter, the sealing composition is pumped into the zone and allowed to form a sealing gel therein.

Claims

1. A composition for preventing the flow of water or gas or both through a subterranean zone penetrated by a well bore comprising:

water;

a biodegradable and non-toxic cross-linking agent comprised of chitosan; and

a selected water soluble polymer which reacts with said cross-linking agent and forms a sealing gel which is stable for a desired period of time at the temperature of said zone and has a pumping time before gelation in the presence of said cross-linking agent whereby said composition can be pumped to the depth of said zone and placed therein.

2. The composition of claim 1 wherein said water soluble polymer is selected from the group consisting of polyacrylamide, AMPS®

/acrylamide copolymers, sulfonated styrene/maleic anhydride copolymers, vinylpyrrolidone/AMPS®

/acrylamide terpolymers, AMPS®

/N-N-dimethyl-acrylamide/acrylamide terpolymers and mixtures thereof.

3. The composition of claim 1 wherein said water is selected from the group consisting of natural seawater, synthetic seawater, brine, unsaturated salt water and fresh water.

4. The composition of claim 1 wherein said subterranean zone has a temperature in the range of from about 70°

F. to about 230°

F., requires a pumping time in the range of from about 2 hours to about 96 hours and said water soluble polymer is polyacrylamide.

5. The composition of claim 1 wherein said subterranean zone has a temperature in the range of from about 70°

F. to about 230°

F., requires a pumping time in the range of from about 2 hours to about 96 hours and said water soluble polymer is an AMPS®

/acrylamide copolymer.

6. The composition of claim 1 wherein said subterranean zone has a temperature in the range of from about 200°

F. to about 350°

F., requires a pumping time in the range of from about 2 hours to about 14 days and said water soluble polymer is selected from the group of vinylpyrrolidone/AMPS®

/acrylamide terpolymers, AMPS®

/N-N-dimethyl-acrylamide/acrylamide terpolymers, sulfonated styrene/maleic anhydride terpolymers and mixtures thereof.

7. The composition of claim 1 wherein the weight ratio of said water soluble polymer to said cross-linking agent is in the range of from about 50:

1 to about 1.1;

1.

8. The composition of claim 1 wherein said water soluble polymer is present in said sealing composition in an amount in the range of from about 0.5% to about 20% by weight of said composition.

9. The composition of claim 1 wherein said cross-linking agent is present in said composition in an amount in the range of from about 0.05% to about 15% by weight of said composition.

10. A biodegradable and non-toxic composition for sealing subterranean zones comprising water, chitosan and a biodegradable and/or non-toxic cross-linkable polymer.

11. The composition of claim 10 wherein said biodegradable and non-toxic polymer is an alginic acid derivative.