Top-down oil recovery

Abstract

Methods relate to producing hydrocarbons, such as bitumen in an oil sands reservoir. The methods include utilizing an injector well with multiple horizontal laterals to provide downward fluid drive toward a producer well. Combined influence of gravity and a dispersed area of the fluid drive due to the laterals facilitate a desired full sweep of the reservoir. Fluids utilized for injection include water heated to less than 60 weight percent steam, solvent for the hydrocarbons and emulsifying agent for the hydrocarbons. The methods employing these fluids provide energy efficient recovery of the hydrocarbons.

1 . A method of producing hydrocarbons, comprising:
 forming a multilateral horizontal injector well in a hydrocarbon-bearing formation with a horizontal length closer to an overburden upper boundary of the hydrocarbon-bearing formation than a lower boundary of the hydrocarbon-bearing formation;   forming a horizontal producer well in the hydrocarbon-bearing formation below at least part of the injector well;   heating the hydrocarbon-bearing formation without fluid transfer between the injector and producer wells to establish fluid communication between the injector and producer wells;   introducing water heated to less than 60 weight percent steam, solvent for the hydrocarbons and emulsifying agent for the hydrocarbons through the injector well and into the hydrocarbon-bearing formation; and   producing the hydrocarbons recovered at the producer well by displacement resulting from combined forces of gravity and a pressure differential maintained between the injector and producer wells that provides a dispersed fluid drive due to the injector well being multilateral.   
     
     
         2 . The method according to  claim 1 , wherein the injector well includes at least four laterals in a common plane with the horizontal length of the injector well. 
     
     
         3 . The method according to  claim 1 , wherein the pressure differential is at least 15-20 kilopascals per meter of separation between the injector and producer wells. 
     
     
         4 . The method according to  claim 1 , wherein the solvent includes hydrocarbons with between 1 and 30 carbon atoms per molecule. 
     
     
         5 . The method according to  claim 1 , wherein the emulsifying agent is a thermally and chemically stable surfactant at reservoir conditions. 
     
     
         6 . The method according to  claim 1 , wherein the emulsifying agent is selected from the group consisting of aromatic sulfonates, alkyl benzyl sulfonates, olefin sulfonates, alkyl aryl sulfonates, alkoxy sulfates, alkaline metal carbonates, alkaline metal bicarbonates and alkaline metal hydroxides. 
     
     
         7 . The method according to  claim 1 , wherein the emulsifying agent includes sodium hydroxide. 
     
     
         8 . The method according to  claim 1 , wherein the solvent includes hydrocarbons with between 4 and 30 carbon atoms per molecule and the emulsifying agent is sodium hydroxide. 
     
     
         9 . The method according to  claim 1 , wherein the injector well is disposed in a top quarter of the hydrocarbon-bearing formation and the producer well is disposed in a bottom quarter of the hydrocarbon-bearing formation. 
     
     
         10 . The method according to  claim 1 , wherein the heating to establish fluid communication between the injector and producer wells includes at least one of electric resistive heating, radio frequency heating, electromagnetic heating and steam circulation with steam injection and production occurring in a same one of the injector and producer wells. 
     
     
         11 . The method according to  claim 1 , wherein the water makes up at least 90 volume percent of a combined quantity of the water and solvent injected. 
     
     
         12 . The method according to  claim 1 , wherein the producer well includes horizontal multilaterals. 
     
     
         13 . The method according to  claim 1 , wherein the water, the solvent and the emulsifying agent are injected together as a mixture. 
     
     
         14 . The method according to  claim 1 , wherein the water is injected at intermittent intervals between when the solvent and the emulsifying agent are injected. 
     
     
         15 . A method of producing hydrocarbons, comprising:
 forming a multilateral horizontal injector well in a hydrocarbon-bearing formation with a horizontal length within three meters of an upper boundary of the hydrocarbon-bearing formation;   forming a horizontal producer well in the hydrocarbon-bearing formation and extending in a horizontal direction within ten meters of the injector well and three meters of a lower boundary of the hydrocarbon-bearing formation;   introducing water heated to less than 60 weight percent steam, solvent for the hydrocarbons and emulsifying agent for the hydrocarbons through the injector well and into the hydrocarbon-bearing formation; and   producing the hydrocarbons recovered at the producer well by displacement resulting from combined forces of gravity and a pressure differential maintained between the injector and producer wells that provides a dispersed fluid drive due to the injector well being multilateral.   
     
     
         16 . The method according to  claim 15 , wherein the emulsifying agent is selected from the group consisting of aromatic sulfonates, alkyl benzyl sulfonates, olefin sulfonates, alkyl aryl sulfonates, alkoxy sulfates, alkaline metal carbonates, alkaline metal bicarbonates and alkaline metal hydroxides. 
     
     
         17 . The method according to  claim 15 , wherein the solvent is a hydrocarbon that is liquid under reservoir conditions. 
     
     
         18 . The method according to  claim 15 , wherein a horizontal bore of the producer well aligns in a vertical direction below a main horizontal bore of the injector well. 
     
     
         19 . The method according to  claim 15 , wherein the producer well includes horizontal multilaterals. 
     
     
         20 . The method according to  claim 15 , wherein the injector well includes at least two laterals on each side of a main bore along the horizontal length of the injector well and in a common plane with the main bore.