Nonionic Surfactants Employed with Extended Chain as the Oil Displacement Agent to use in Enhanced Oil Recovery

Abstract

Some reservoirs have tight oil formations, such as the Changqing reservoir. The surfactant polymer flooding and low tension gas flooding are two potential chemical flooding methods for use in tight oil formations. In these methods, an oil displacement agent, or surfactant, is added. Nonionic surfactants with extended chains (by propylene oxide and ethylene oxide) from dialkyl alcohols or dialkyl amines were tested. A synergistic blend of surfactants was developed between the nonionic surfactants and anionic surfactants that lowers interfacial tension and improves surfactant solubility in water and oil.

1 . A nonionic long chain surfactant of formula:
 C n+1 H 2n+3 CH(C n+3 H 2n+7 )CH 2 O(PO) x (EO) y H   wherein:   n is 3, 5, 9, 7, 11, or 13;   x is 5-50; and   y is 5-30.   
     
     
         2 . The nonionic long chain surfactant of  claim 1  wherein the surfactant is dissolved in formation water with at least one anionic surfactant. 
     
     
         3 . The nonionic long chain surfactant of  claim 2  wherein the at least one anionic surfactant is alkyl benzene sulfonate. 
     
     
         4 . The nonionic long chain surfactant of  claim 2  wherein the weight ratio of the nonionic long chain surfactant to the anionic surfactant is from 2:5 to 6:1. 
     
     
         5 . The nonionic long chain surfactant of  claim 1  wherein the surfactant is dissolved in formation water. 
     
     
         6 . The nonionic long chain surfactant of  claim 5  further comprising a 0-20% salt solution. 
     
     
         7 . The nonionic long chain surfactant of  claim 6  wherein the salt is monovalent or divalent. 
     
     
         8 . The nonionic long chain surfactant of  claim 6  wherein the salt comprises NaCl, KCl, MgCl 2 , MgCO 3 , CaCl 2 , or combinations thereof. 
     
     
         9 . The nonionic long chain surfactant of  claim 2  wherein the surfactant is further dissolved with 0-5% polymer. 
     
     
         10 . The nonionic long chain surfactant of  claim 9  wherein the polymer is polyacrylamide. 
     
     
         11 . A method of preparing a nonionic long chain surfactant comprising:
 adding KOH to an alcohol in a reactor to form a mixture;   initially heating and agitating the mixture in the reactor under vacuum with a nitrogen purge;   further heating the mixture;   adding propylene oxide to the mixture;   incubating the propylene oxide reaction;   adding ethylene oxide to the mixture;   incubating the ethylene oxide reaction;   cooling the mixture; and   removing the nonionic long chain surfactant from the reactor.   
     
     
         12 . The method of  claim 11  wherein the initial heating of the reactor occurs at about 100 degrees Celsius. 
     
     
         13 . The method of  claim 11  wherein the initial heating occurs for 0-2 hours. 
     
     
         14 . The method of  claim 11  wherein the mixture is further heated to 120-150 degrees Celsius. 
     
     
         15 . The method of  claim 11  wherein the mixture is cooled to about 60 degrees Celsius. 
     
     
         16 . The method of  claim 11  wherein the alcohol is a Guerbet alcohol. 
     
     
         17 . The method of  claim 16  wherein the Guerbet alcohol has a formula comprising:
 C n+1 H 2n+3 CH(C n+3 H 2n+7 )CH 2 OH wherein n is 3, 5, 7, 9, 11, or 13. 
 
     
     
         18 . The method of  claim 16  wherein incubating the propylene oxide reaction results in 5-50 propylene oxide molecules attached in a surfactant chain to the Guerbet alcohol. 
     
     
         19 . The method of  claim 18  wherein incubating the ethylene oxide reaction results in 5-30 ethylene oxide molecules attached in the surfactant chain. 
     
     
         20 . The method of  claim 11  wherein incubating the propylene oxide reaction occurs for 2-6 hours and incubating the ethylene oxide reaction occurs for 2-6 hours.