Viscoelastic surfactant fluids and related methods of use

Abstract

Viscoelastic surfactant based aqueous fluid systems useful as thickening agents in various applications, e.g. to suspend particles produced during the excavation of geologic formations. The surfactants are zwitterionic/amphoteric surfactants such as dihydroxyl alkyl glycinate, alkyl ampho acetate or propionate, alkyl betaine, alkyl amidopropyl betaine and alkylimino mono- or di-propionates derived from certain waxes, fats and oils. The thickening agent is used in conjunction with an inorganic water-soluble salt or organic additive such as phthalic acid, salicylic acid or their salts.

1 - 99 . (canceled) 
     
     
         100 . A viscoelastic fluid, comprising:
 (1) an aqueous medium;   (2) erucyl amidopropyl betaine   (3) a member selected from the group consisting of organic acids, organic acid salts, inorganic salts, and combinations of one or more organic acids or organic acid salts with one or more inorganic salts;   wherein the fluid exhibits viscoelasticity.   
     
     
         101 . The fluid of  claim 100 , further comprising an anionic surfactant. 
     
     
         102 . The fluid of  claim 101 , wherein the anionic surfactant is present at 1.2% or less by weight of the fluid. 
     
     
         103 . The fluid of  claim 101 , wherein the anionic surfactant is present at 0.9% or less by weight of the fluid. 
     
     
         104 . The fluid of  claim 101 , wherein the anionic surfactant is present at about 0.5% or less by weight of the fluid. 
     
     
         105 . The fluid of  claim 100 , wherein erucyl amidopropyl betaine is present at about 0.5 wt % to about 10 wt % by weight of the fluid. 
     
     
         106 . The fluid of  claim 100 , wherein erucyl amidopropyl betaine is present at about 0.5 wt % to about 8 wt % by weight of the fluid. 
     
     
         107 . The fluid of  claim 100 , wherein erucyl amidopropyl betaine is present at about 0.5 wt % to about 6 wt % by weight of the fluid. 
     
     
         108 . The fluid of  claim 100 , wherein erucyl amidopropyl betaine constitutes 89% or more by weight of all surfactants present in the fluid. 
     
     
         109 . The fluid of  claim 100 , wherein erucyl amidopropyl betaine constitutes 92% or more by weight of all surfactants present in the fluid. 
     
     
         110 . The fluid of  claim 100 , wherein the member is an inorganic salt and is present at about 0.1% to about 30% by weight. 
     
     
         111 . The fluid of  claim 100 , wherein the member is an organic acid or salt thereof and is present at about 0.1% to about 10% by weight. 
     
     
         112 . The fluid of  claim 100 , further comprising a nonionic surfactant or a cationic surfactant. 
     
     
         113 . The fluid of  claim 100 , further comprising an anionic surfactant, wherein the ratio of erucyl amidopropyl betaine to anionic surfactant is 3⅓ to 1 or greater. 
     
     
         114 . The fluid of  claim 113 , wherein the ratio of erucyl amidopropyl betaine to anionic surfactant is greater than 5 to 1. 
     
     
         115 . The fluid of  claim 114 , wherein the ratio of erucyl amidopropyl betaine to anionic surfactant is greater than 8 to 1. 
     
     
         116 . The fluid of  claim 115 , wherein the ratio of erucyl amidopropyl betaine to anionic surfactant is greater than 12 to 1. 
     
     
         117 . The fluid of  claim 100 , further comprising an anionic surfactant, wherein erucyl amidopropyl betaine is present at about 0.5 wt % to about 10 wt % by weight of the fluid, wherein the ratio of erucyl amidopropyl betaine to anionic surfactant is 3⅓ to 1 or greater, wherein the member is an inorganic salt present at about 0.1% to about 30% by weight or an organic acid or salt thereof present at about 0.1% to about 10% by weight. 
     
     
         118 . The fluid of  claim 100 , further comprising an anionic surfactant, wherein erucyl amidopropyl betaine is present at about 0.5 wt % to about 6 wt % by weight of the fluid, wherein the ratio of erucyl amidopropyl betaine to anionic surfactant is greater than 5 to 1, wherein the member is an inorganic salt present at about 0.1% to about 30% by weight or an organic acid or salt thereof present at about 0.1% to about 10% by weight. 
     
     
         119 . (canceled)