Viscous oil recovery using electric heating and solvent injection

Abstract

To recover in situ viscous oil from an underground reservoir, electricity is conducted through the underground reservoir by at least two electrodes in an amount that would, in the absence of solvent injection, cause water in the reservoir to vaporize adjacent to the electrodes, and injecting solvent into the reservoir to mitigate water vaporization adjacent to the electrodes by vaporizing solvent in this region. Oil and solvent are produced through one or more production wells.

1 . A method of recovering hydrocarbons from an underground reservoir, the method comprising:
 (a) conducting electricity at least partially through a conductive brine within the reservoir between two or more electrodes disposed in the reservoir;   (b) injecting solvent into the reservoir at least partially in a liquid phase and where the solvent has a bubble point temperature between 10° C. and 100° C. at a pressure of 1 atm.;   (c) heating a portion of the reservoir through said conduction of electricity to vaporize at least a portion of the injected solvent; and   (d) producing hydrocarbons through one or more wells.   
     
     
         2 . The method of  claim 1  wherein sufficient solvent is injected into the reservoir and proximate to one or more of the two or more electrodes to maintain the portion of the reservoir at a temperature below the boiling point temperature of water at reservoir pressure conditions. 
     
     
         3 . The method of  claim 1  wherein the hydrocarbons are a viscous oil having an in situ viscosity greater than 10 cP at initial reservoir conditions. 
     
     
         4 . The method of  claim 1  wherein the portion of the reservoir is adjacent to at least one of the two or more electrodes. 
     
     
         5 . The method of  claim 1  further comprising injecting a conductive brine into the reservoir to further control reservoir in situ temperature or to maintain or achieve in situ conductivity. 
     
     
         6 . The method of  claim 1  wherein the solvent comprises propane, butane, pentane, hexane, or heptane, or a combination thereof. 
     
     
         7 . The method of  claim 1  further comprising heating the solvent above ground prior to injection. 
     
     
         8 . The method of  claim 1  further comprising heating the solvent beneath ground prior to injection into the reservoir. 
     
     
         9 . The method of  claim 8  wherein the solvent heating is effected by a subsurface electric heating element. 
     
     
         10 . The method of  claim 1  wherein the solvent is produced through one or more wells and is at least partially produced as a vapor. 
     
     
         11 . The method of  claim 1  wherein one or more wells used for solvent injection are also used as, or houses, one or more of the two or more electrodes. 
     
     
         12 . The method of  claim 1  wherein one or more of the one or more wells used for production is also used as, or houses, one or more of the two or more electrodes. 
     
     
         13 . The method of  claim 1  wherein the solvent is injected through at least two injection wells which act as, or house, the two or more electrodes, respectively. 
     
     
         14 . The method of  claim 1  wherein the solvent has a bubble point temperature between 35° C. and 99° C. at a pressure of 1 atm. 
     
     
         15 . The method of  claim 1  wherein the solvent has a solubility limit at reservoir conditions of at least 5% by mass in the hydrocarbons in the underground reservoir. 
     
     
         16 . The method of  claim 1  wherein the solvent has a solubility limit at reservoir conditions of at least 20% by mass in the hydrocarbons in the underground reservoir. 
     
     
         17 . The method of  claim 1  wherein the solvent has a solubility limit at reservoir conditions of at least 50% by mass in the hydrocarbons in the underground reservoir. 
     
     
         18 . The method of  claim 1  wherein at least 25 mass % of the solvent enters the reservoir as a liquid. 
     
     
         19 . The method of  claim 1  wherein at least 50 mass % of the solvent enters the reservoir as a liquid. 
     
     
         20 . The method of  claim 1  wherein the solvent comprises greater than 50 mass % of components comprising propane, butane, or pentane. 
     
     
         21 . The method of  claim 1  wherein the solvent comprises greater than 50 mass % propane. 
     
     
         22 . The method of  claim 1  wherein the solvent comprises greater than 70 mass % propane. 
     
     
         23 . The method of  claim 1  wherein cycles of solvent injection and solvent and hydrocarbon production occur through the one or more wells and where the one or more wells also act as or house one or more of the two or more electrodes.