Polymeric gel system and use in hydrocarbon recovery

Abstract

Coacervate gels having excellent shear viscosities and other properties are made with anionic or cationic polymers, a smaller amount of a surfactant having a charge opposite that of the polymer, and a hydrophobic alcohol. The Zeta Potential of the gel is maintained at an absolute value of at least 20. Optional gel promoting additives include betaines and amine oxides. A preferred gel comprises poly diallyl dimethyl ammonium chloride, a lesser amount of sodium lauryl sulfonate, and lauryl alcohol. The gels are particularly useful in well drilling fluids and well fracturing fluids.

1 . An aqueous gel comprising water and, by weight based on the water, (a) 0.1% to 5% of an anionic or cationic polymer, (b) a lesser amount but at least 0.01% of a surfactant having from 8 to 22 carbon atoms and a charge opposite that of said polymer, (c) from 0.001 to 5% of a hydrophobic alcohol, (d) up to 5% of an amphoteric surfactant, and (e) up to 5% of an amine oxide, said gel having a Zeta Potential of an absolute value of at least 20 millivolts.  
     
     
         2 . An aqueous gel of  claim 1  wherein said polymer is an anionic polymer comprising at least 20% mer units derived from 2-acrylamido-2-methylpropane sulfonic acid.  
     
     
         3 . An aqueous gel of  claim 1  wherein said amphoteric surfactant comprises a betaine or sultaine gel promoter and is present in an amount from 0.001% to 2%.  
     
     
         4 . An aqueous gel of  claim 3  wherein said amphoteric surfactant comprises cocamidopropyl betaine and is present in an amount from 0.001% to 2%.  
     
     
         5 . An aqueous gel of  claim 1  wherein said amine oxide comprises lauryl amine oxide and is present in an amount from 0.001% to 2%.  
     
     
         6 . An aqueous gel of  claim 1  wherein said polymer is a cationic polymer and said hydrophobic alcohol is a linear or branched alkyl alcohol of the general formula C M H 2M+2−N (OH) N , where M is a number from 6-23, and N is 1 when M is 6-12, but where M is 13-23, N may be a number from 1 to 3, said gel including at least one of (a) 0.001% to 5% amine oxide and (b) 0.001% amphoteric surfactant.  
     
     
         7 . An aqueous gel of  claim 6  wherein said alkyl alcohol is a linear monohydric alcohol having from 8-15 carbon atoms.  
     
     
         8 . An aqueous gel of  claim 7  wherein said alkyl alcohol comprises lauryl alcohol.  
     
     
         9 . An aqueous gel of  claim 6  wherein at least 20% of the mer units of said cationic polymer are derived from dimethyl diallyl ammonium chloride.  
     
     
         10 . A subterranean fracturing fluid comprising an aqueous gel of  claim 6  and a propping agent.  
     
     
         11 . A subterranean drilling fluid comprising an aqueous gel of  claim 6  and a foam generating gas.  
     
     
         12 . A subterranean formation treatment fluid comprising an aqueous gel of  claim 6  and a gel breaker.  
     
     
         13 . Method of making an aqueous gel comprising adding to water 0.1% to 5%, by weight based on the water, cationic polymer and a lesser amount but at least 0.01% by weight of an anionic surfactant having from 8 to 22 carbon atoms, in the presence of 0.001% to 5% linear or branched alkyl alcohol of the general formula C M H 2M+2−N (OH) N , where M is a number from 6-23, and N is 1 when M is 6-12, but where M is 13-23, N may be a number from 1 to 3, and optionally in the presence of at least one of (a) up to 5% by weight amphoteric surfactant and (b) up to 5% by weight amine oxide, the ratio of said cationic polymer to said anionic surfactant being effective to provide a Zeta Potential having an absolute value of at least 20 millivolts.  
     
     
         14 . Method of  claim 13  wherein said cationic polymer comprises a polymer including mer units derived from dimethyl diallyl ammonium chloride.  
     
     
         15 . Method of  claim 14  wherein said anionic surfactant comprises sodium lauryl sulfonate.  
     
     
         16 . Method of  claim 13  wherein said alkyl alcohol comprises a linear monohydroxy alcohol having from 8 to 14 carbon atoms.  
     
     
         17  An aqueous gel comprising a water-soluble polymer in an amount no greater than 1% by weight, having at least one of (a) a zero shear viscosity of at least 45,000 following the zero shear viscosity extrapolation procedure of Asadi, Conway and Barree in SPE 73755 or (b) a “10/100 20/40” settling rate result at 60 minutes of no more than 8 millimeters.  
     
     
         18  An aqueous gel of  claim 17  wherein said water-soluble polymer is cationic and is present in said gel in an amount no greater than 0.7%.  
     
     
         19  A well treatment fluid comprising a proppant and a gel of  claim 18 .  
     
     
         20  An aqueous gel of  claim 18  including an anionic surfactant in an amount less than that of said polymer, and a small amount of a hydrophobic alcohol.