Well treatment fluid and methods with oxidized polysaccharide-based polymers

Abstract

The present invention provides a well treatment fluid containing water, a amine-based polymer, and an oxidized polysaccharide-based polymer. The oxidized polysaccharide-based polymer is able to crosslink with the amine-based polymer and produce a gel having a viscosity of greater than about 20 cp, measured at a pH of about 4 to about 7 and at STP. The present invention also provides a method of treating a subterranean formation penetrated by a wellbore comprising the steps of: (a) forming the well treatment fluid, and (b) contacting the subterranean formation with the fluid.

1 . A well treatment fluid for use in a well, the well treatment fluid comprising: 
 (a) water;    (b) an amine-based polymer; and    (c) an oxidized polysaccharide-based polymer, which is able to crosslink with the amine-based polymer in water to produce a gel having a viscosity of greater than or equal to about 20 cp.    
     
     
         2 . The well treatment fluid of  claim 1 , wherein the amine-based polymer comprises at least one member selected from the group of chitosan, oxidized chitosan, polyvinylalcoholamine and polyethyleneimine.  
     
     
         3 . The well treatment fluid of  claim 2  wherein the oxidized chitosan is prepared by oxidizing chitosan-based polymers selected from the group consisting of chitosan, chitosan salts, and any combinations in any proportion thereof.  
     
     
         4 . The well treatment fluid of  claim 1  wherein the amine-based polymer is prepared by oxidizing a chitosan-based polymer with an oxidizer selected from the group consisting of sodium hypochlorite, sodium periodate, hydrogen peroxide, peracetic acid, and any mixture in any proportion thereof.  
     
     
         5 . The well treatment fluid of  claim 1  wherein the oxidized polysaccharide-based polymer is selected from the group consisting of dialdehyde starch, dialdehyde cellulose, oxidized starch, oxidized cellulose, oxidized agarose, oxidized partially-acetylated cellulose, oxidized HEC, and combinations thereof.  
     
     
         6 . The well treatment fluid of  claim 5  wherein the oxidized starch, oxidized cellulose, oxidized agarose, oxidized HEC, or oxidized partially-acetylated cellulose is prepared by oxidizing about 1% to about 25% of the glucose units of the polysaccharide-based polymer with an oxidizer selected from the group consisting of alkali, alkaline earth and transition metal salts of periodate, hypochlorite, perbromate, chlorite, chlorate, hydrogen peroxide and combinations thereof.  
     
     
         7 . The well treatment fluid of  claim 1  wherein the oxidized polysaccharide-based polymer is selected from the group consisting of dialdehyde starch, dialdehyde cellulose, oxidized starch and combinations thereof.  
     
     
         8 . The well treatment fluid of  claim 1  wherein the oxidized polysaccharide based polymer comprises oxidized starch, oxidized cellulose, oxidized agarose, oxidized hydroxyethylcellulose, or oxidized partially-acetylated cellulose prepared by oxidizing about 1% to about 25% of the glucose units of the polysaccharide-based polymer with an oxidizer selected from the group consisting of alkali, alkaline earth and transition metal salts of periodate, hypochlorite, perbromate, chlorite, chlorate, hydrogen peroxide and combinations thereof.  
     
     
         9 . The well treatment fluid of  claim 8  wherein the oxidized polysaccharide is oxidized starch and said oxidized starch is present in an amount of up to about 10 wt %.  
     
     
         10 . The well treatment fluid of  claim 9  wherein the ratio of the oxidized starch to the amine-based polymer is from about 20:1 to about 1:20.  
     
     
         11 . The well treatment fluid of  claim 1  wherein the amine-based polymer is oxidized chitosan which is present in an amount of up to about 10 wt %.  
     
     
         12 . The well treatment fluid of  claim 1  wherein the ratio of the oxidized chitosan to oxidized polysaccharide is from about 50:1 to about 1:50.  
     
     
         13 . The well treatment fluid of  claim 1  wherein the water for the well treatment fluid is selected from the group consisting of fresh water, seawater, natural brine, formulated brine, 2% KCl solution, and any mixtures in any proportion thereof.