Determination of an actual optimum salinity and an actual optimum type of microemulsion for surfactant/polymer flooding

Abstract

Systems and methods for the determination of an optimum salinity type and an optimum salinity of a surfactant microemulsion system are shown. Optimum salinity type and optimum salinity in surfactant/polymer flooding is determined, according to embodiments, by core-flood experiments so that a variety of multiphase flow parameters such as relative permeability and phase trapping that affects oil recovery factor, influences the determination of the optimum salinity type and optimum salinity. The optimum salinity determined from this approach preferably corresponds to the highest oil recovery factor.

1 . A method of determining an actual optimum salinity of a surfactant system that produces an optimal recovery factor of an oil from a reservoir, said method comprising:
 conducting core flood experiments for said reservoir;   determining from said core flood experiments, said actual optimum salinity, wherein said determined actual optimum salinity is a function of IFT and parameters other than IFT and wherein said core flood experiments comprises a first set of core flood experiments that are run to determine the actual optimum system type and then a second set of core flood experiments run to determine the actual optimum salinity in said actual optimum system type.   
   
   
       2 . The method of  claim 1  wherein said other parameters is selected from the list consisting of: relative permeability, phase trapping and adsorption. 
   
   
       3 . (canceled) 
   
   
       4 . (canceled) 
   
   
       5 . The method of  claim 1  wherein said core flood experiments, to determine the actual optimum system type, are run in each of surfactant system types, Type II(−), Type III, and Type II(+). 
   
   
       6 . A method of determining an optimum salinity of a surfactant system that produces an optimal recovery factor of an oil, said method comprising:
 determining a surfactant salinity range for each of system types Type II(−), Type III, and Type II(+) system;   selecting a plurality of salinities from each of at least two of said determined ranges of system types, wherein said determining of said salinity ranges of system types includes: experiments that measure the interfacial tension between a microemulsion and a water solution and said microemulsion and said oil;   running core flood experiments for said selected surfactant salinities to determine a highest oil recovery factor of said plurality of selected salinities;   selecting a series of surfactant system salinities from the salinity range of said system type that includes the surfactant salinity with said highest oil recovery factor; and   running core flood experiments on said series of surfactant salinities to determine an oil recovery factor for each of said selected series of surfactant salinities.   
   
   
       7 . (canceled) 
   
   
       8 . The method of  claim 6  wherein said determining of said surfactant salinity ranges of system types includes:
 experiments that equilibrate a mixture of said oil and a surfactant system and measuring the volumes of phases formed by said equilibration.   
   
   
       9 . The method of  claim 6  wherein said selecting includes:
 selecting combinations from the list consisting of:
 a salinity about midpoint of said Type III system, a salinity about a predetermined percentage below the lowest Type III salinity, a salinity about said predetermined percentage above the highest Type III salinity. 
   
   
   
       10 . The method of  claim 9  wherein said predetermined percentage is 5-30%. 
   
   
       11 . The method of  claim 6  further comprising:
 identifying the optimum oil recovery factor obtained from said core flood experiments for said selected surfactant salinities.   
   
   
       12 . The method of  claim 6  further comprising:
 selecting a new surfactant system salinity from each of at least two of said ranges of system types if said highest oil recovery factor of said selected salinities is within a predetermined percentage of a core flood oil recovery factor of said other selected salinities; and   running core flood experiments for said new system surfactant salinities.   
   
   
       13 . The method of  claim 12  wherein the predetermined percentage is selected from the range of 5 to 15. 
   
   
       14 . (canceled) 
   
   
       15 . The method of  claim 6  further comprising:
 identifying the surfactant system salinity of said series of salinities having the highest oil recovery as the optimum salinity.   
   
   
       16 . A method of recovering oil from a reservoir, said method comprising:
 conducting core flood experiments for said reservoir;   determining from said core flood experiments, said actual optimum salinity, wherein said determined actual optimum salinity is a function of IFT and parameters other than IFT; and   flooding said reservoir with a surfactant system of said optimum salinity, wherein said core flood experiments are run first to determine the actual optimum system type and then to determine the actual optimum salinity in said actual optimum system type.   
   
   
       17 . The method of  claim 16  wherein said other parameters is selected from the list consisting of: relative permeability, phase trapping, and adsorption. 
   
   
       18 . (canceled) 
   
   
       19 . (canceled) 
   
   
       20 . The method of  claim 16  wherein said core flood experiments are run in at least two surfactant system types, said surfactant system types selected from the list consisting of: Type II(−), Type III, and Type II(+) system. 
   
   
       21 . A method of recovering oil from a reservoir, said method comprising:
 flooding said reservoir with a surfactant system, the salinity of said surfactant system determined by:
 determining a surfactant salinity range for each of system types Type II(−), Type III, and Type II(+) system; 
 selecting a plurality of salinities from each of at least two of said determined ranges of system types; and 
   running core flood experiments for said selected plurality of surfactant salinities to determine a highest oil recovery factor of said selected salinities;   selecting a series of surfactant salinities from the salinity range of said system type that includes the surfactant salinity with said highest oil recovery factor; and   running core flood experiments on said series of surfactant salinities to determine an oil recovery factor for each of said selected series of surfactant salinities.   
   
   
       22 . The method of  claim 21  wherein said determining of said salinity ranges of system types includes:
 experiments that measure the interfacial tensions between a microemulsion and a water solution, and between said microemulsion and said oil.   
   
   
       23 . The method of  claim 21  wherein said determining of said salinity ranges of system types includes:
 experiments that equilibrate a mixture of said oil and a surfactant system and measuring the volumes of phases formed by said equilibration.   
   
   
       24 . The method of  claim 21  wherein said selecting includes:
 selecting combinations from the list consisting of: a salinity about midpoint of said Type III system, a salinity about 5-30% below the lowest Type III salinity, a salinity about 5-30% above the highest Type III salinity.   
   
   
       25 . The method of  claim 21  wherein said surfactant system salinity determination further comprises:
 identifying the highest oil recovery factor obtained from said core flood experiments for said selected surfactant salinities.   
   
   
       26 . The method of  claim 25  wherein said surfactant system salinity determination further comprises:
 selecting a new surfactant system salinity from each of at least two of said ranges of system types if said highest oil recovery factor of said selected salinities is within a predetermined percentage higher than that of a core flood oil recovery factor of said other selected salinities; and   running core flood experiments for said new surfactant salinities.   
   
   
       27 . The method of  claim 26  wherein the predetermined percentage is selected from the range of about 5 to 15. 
   
   
       28 . (canceled) 
   
   
       29 . The method of  claim 21  wherein said surfactant system salinity determination further comprises:
 identifying the salinity of said series of salinities having the highest oil recovery as the optimum salinity.