Completion fluid

Abstract

An aqueous well completion/workover fluid, including a surfactant, at least one salt and an alkaline material, wherein the surfactant comprises a mixture of a phosphate ester and a non ionic ethoxylated alcohol, wherein the fluid has a pH between 6 and 8, and wherein the fluid generates an interfacial tension with crude oil of less than or equal to 1 dyne/cm. The fluid is not harmful to a formation if it penetrates the formation, and further exhibits an excellent detergency which can be beneficial as well.

1 - 14 . (canceled) 
     
     
         15 . A method for completing a well, comprising the steps of
 pumping an aqueous fluid comprising: a surfactant; at least one salt; and an alkaline material, wherein the surfactant comprises a mixture of a phosphate ester and a non ionic ethoxylated alcohol, wherein the fluid has a pH between 6 and 8, and wherein the fluid generates an interfacial tension with crude oil of less than or equal to 1 dyne/cm; and   holding the fluid in the well during a completion process   
     
     
         16 . The method of  claim 15 , wherein the at least one salt is selected from the group consisting of potassium chloride (KCl), potassium acetate (CH 3 CO 2 K), sodium chloride (NaCl), calcium chloride (CaCl 2 ), and a mixture thereof. 
     
     
         17 . The method of  claim 15 , wherein the alkaline material is preferably an amino-alcohol. 
     
     
         18 . The method of  claim 15 , wherein the fluid exhibits a detergency of at least 90%. 
     
     
         19 . The method of  claim 15 , wherein the fluid contains the surfactant in an amount between 0.2 and 3.0 w/w with respect to weight of the fluid. 
     
     
         20 . The method of  claim 15 , wherein the fluid contains the surfactant in an amount between 0.5 and 1% w/w with respect to weight of the fluid. 
     
     
         21 . The method of  claim 15 , wherein the surfactant contains the phosphate ester in an amount between 20 and 60% w/w of the surfactant. 
     
     
         22 . The method of  claim 21 , wherein the surfactant contains the non-ionic ethoxylated alcohol in an amount between 80 and 40% w/w of the surfactant. 
     
     
         23 . The method of  claim 15 , wherein the phosphate ester has the following chemical structure: 
       
         
           
           
               
               
           
         
         where: 
         x is the number of ethylene oxide units present in the molecule and x=3, 6 or 9; and 
         n is length of the alkyl hydrocarbon, and n=12-14. 
       
     
     
         24 . The method of  claim 15 , wherein the non-ionic ethoxylated alcohol has the following chemical structure:
   HO—(CH 2 CH 2 O) x —(C n H 2n+1 )
   wherein:   x is the number of ethylene oxide units present in the molecule, and x=3, 6 or 9; and   n is length of the alkyl hydrocarbon, and n=12-14.   
     
     
         25 . The method of  claim 15 , wherein the at least one salt is potassium chloride. 
     
     
         26 . The method of  claim 15 , wherein the at least one salt is present in an amount between about 1 and about 5% w/w with respect to weight of the fluid. 
     
     
         27 . The method of  claim 15 , wherein the fluid contains the alkaline material in an amount between 0.15 and 1.00% w/w of the fluid. 
     
     
         28 . The method of  claim 15 , wherein the alkaline material is amino-alcohol selected from the group consisting of monoethanolamine, potassium hydroxide (KOH), sodium hydroxide (NaOH), and mixtures thereof.