Effect of bio-polymer viscosity on residual oil saturation in carbonate reservoirs

Abstract

Polymer flooding models for carbonate reservoirs and related methods include the trapping number effect on residual oil saturation. A method for predicting oil recovery from a reservoir using enhanced oil recovery techniques can include simulating the reservoir in a computer simulation (202). Injection of a fluid (204) can be simulated in the computer simulation and an enhanced oil recovery technique can be simulated to simulate the oil recovery from die reservoir (206).

1 . A method of generating a prediction of an oil recovery from a reservoir induced by accomplishing an enhanced oil recovery technique that comprises injection of one or more fluids into the reservoir, the method comprising:
 simulating the reservoir in a computer simulation;   simulating injection of a first fluid into the reservoir in the computer simulation; and   simulating the oil recovery from the reservoir induced by accomplishing an enhanced oil recovery technique in the computer simulation so as to account for an estimated change in aqueous viscosity that would be induced by injection of the first fluid into the reservoir.   
     
     
         2 . The method of  claim 1 , wherein the computer simulation simulates:
 the reservoir in three dimensions; and   multiphase flow within the reservoir.   
     
     
         3 . (canceled) 
     
     
         4 . The method of  claim 2 , further comprising simulating injection of a second fluid into the reservoir in the computer simulation, optionally wherein the first fluid is injected into the reservoir after the second fluid is injected into the reservoir in the enhanced oil recovery technique, or the first fluid comprises a polymer and the second fluid comprises water. 
     
     
         5 .- 6 . (canceled) 
     
     
         7 . The method of any of  claim 1 , comprising:
 calculating a trapping number (N Tl ) for the reservoir that accounts for the first fluid within the reservoir, wherein the trapping number is defined as:   
       
         
           
             
               
                 v 
                 ⁢ 
                 μ 
               
               
                 σ 
                 
                   o 
                   ⁢ 
                   w 
                 
               
             
           
         
       
       where ν is a Darcy velocity of a core sample comprising the same or similar material as the reservoir, μ is an aqueous phase viscosity, and σ ow  is an interfacial tension between oil and water. 
     
     
         8 . A method comprising:
 generating a model of a hydrocarbon reservoir having parameters;   determining a critical trapping number for the hydrocarbon reservoir based in part on a substrate of the hydrocarbon reservoir;   determining a trapping number of the substrate for a given injection volume;   determining whether the trapping number has exceeded the critical trapping number; and   modifying, based in part on the determination that the critical trapping number has been exceeded, one or more parameters of the model of the hydrocarbon reservoir.   
     
     
         9 . The method of  claim 8 , wherein generating the model of the hydrocarbon reservoir comprises generating the hydrocarbon reservoir in three dimensions and modeling multiphase flow within the hydrocarbon reservoir, optionally wherein the parameters of the hydrocarbon reservoir comprise residual oil and relative permeability, or wherein modifying the one or more parameters of the model comprises modifying the residual oil and relative permeability parameters. 
     
     
         10 .- 11 . (canceled) 
     
     
         12 . The method of  claim 8 , wherein determining a trapping number of the substrate for a given injection volume comprises simulating injection of a first fluid into the model of the hydrocarbon reservoir, optionally wherein the first fluid comprises a polymer. 
     
     
         13 . (canceled) 
     
     
         14 . The method of  claim 8 , further comprising, determining expected oil recovery for a reservoir having a substrate that is the same as or similar to the substrate of the model of the hydrocarbon reservoir, optionally wherein determining the expected oil recovery comprises determining the expected oil recovery using an enhanced oil recovery technique. 
     
     
         15 . (canceled) 
     
     
         16 . A method of simulating oil recovery from a biopolymer injection cycle in a hydrocarbon carbonate reservoir, the method comprising:
 determining a critical trapping number representative of a simulated hydrocarbon carbonate reservoir based in part on a composition of a reservoir substrate;   determining whether, for a given injection volume, a trapping number of a substrate of the hydrocarbon carbonate reservoir has exceeded a critical trapping number; and   modifying residual oil and relative permeability parameters of the simulated hydrocarbon carbonate reservoir based on the determination that the critical trapping number has been exceeded.   
     
     
         17 . The method of  claim 16 , wherein, prior to determining the critical trapping number, the method further comprises simulating the hydrocarbon carbonate reservoir, optionally wherein the hydrocarbon carbonate reservoir is simulated in three dimensions and includes multiphase flow within the hydrocarbon carbonate reservoir. 
     
     
         18 . (canceled) 
     
     
         19 . The method of  claim 16 , wherein prior to determining whether the trapping number of the substrate has exceeded the critical trapping number, the method further comprises determining the trapping number of the substrate for the given injection volume, optionally wherein the trapping number (N Tl ) is defined as 
       
         
           
             
               
                 
                   v 
                   ⁢ 
                   μ 
                 
                 
                   σ 
                   
                     o 
                     ⁢ 
                     w 
                   
                 
               
               , 
             
           
         
       
       where ν is a Darcy velocity of a core sample comprising the same or similar material as the hydrocarbon carbonate reservoir, μ is an aqueous phase viscosity, and σ ow  is an interfacial tension between oil and water. 
     
     
         20 . (canceled) 
     
     
         21 . The method of  claim 19 , wherein determining the trapping number comprises simulating injection of a first fluid into the simulated hydrocarbon carbonate reservoir, optionally wherein the first fluid comprises a polymer. 
     
     
         22 . (canceled) 
     
     
         23 . The method of  claim 21 , further comprising, determining expected oil recovery for a reservoir having a substrate that is the same as or similar to the substrate of the simulated hydrocarbon carbonate reservoir, optionally wherein determining the expected oil recovery comprises determining the expected oil recovery using an enhanced oil recovery technique. 
     
     
         24 . (canceled) 
     
     
         25 . A computer system comprising:
 rewritable memory; and   a processor operable in response to execution instructions stored in the rewritable memory to:
 determine a critical trapping number representative of a simulated hydrocarbon reservoir based in part on a composition of a reservoir substrate; 
 determine whether, for a given injection volume, a trapping number of the substrate has exceeded the critical trapping number; and 
 modify residual oil and relative permeability parameters of the simulated hydrocarbon reservoir based on the determination that the critical trapping number has been exceeded. 
   
     
     
         26 . The computer system of  claim 25 , wherein, prior to determining the critical trapping number, the processor and rewritable memory are further operable to simulate the hydrocarbon reservoir, optionally wherein the hydrocarbon reservoir is simulated in three dimensions and includes multiphase flow within the hydrocarbon reservoir. 
     
     
         27 . (canceled) 
     
     
         28 . The computer system of  claim 25 , wherein prior to determining whether the trapping number of the substrate has exceeded the critical trapping number, the processor is further operable to determine the trapping number of the substrate for the given injection volume, optionally wherein the trapping number (N Tl ) is defined as 
       
         
           
             
               
                 
                   v 
                   ⁢ 
                   μ 
                 
                 
                   σ 
                   
                     o 
                     ⁢ 
                     w 
                   
                 
               
               , 
             
           
         
       
       where ν is a Darcy velocity of a core sample comprising the same or similar material as the reservoir, μ is an aqueous phase viscosity, and σ ow  is an interfacial tension between oil and water. 
     
     
         29 . (canceled) 
     
     
         30 . The computer system of  claim 25 , wherein the processor and rewritable memory are further operable to, determine expected oil recovery for a reservoir having a substrate that is the same as or similar to the substrate of the simulated hydrocarbon reservoir, optionally wherein the expected oil recovery is determined for oil recovery using an enhanced oil recovery technique. 
     
     
         31 . (canceled)