Process for obtaining viscous mineral oil from an underground deposit

Abstract

The invention provides a process for producing mineral oil from an underground mineral oil deposit into which at least one injection well which is in contact with the mineral oil deposit via at least one perforation zone and at least one production well have been sunk, comprising injecting at least one aqueous urea solution into the injection well and pressure-injecting the aqueous urea solution through the perforation zone into the mineral oil deposit, wherein the aqueous urea solution on pressure injection into the mineral oil deposit is at a temperature of at least 80° C.

1 . A process for producing mineral oil from an underground mineral oil deposit into which at least one injection well which is in contact with the mineral oil deposit via at least one perforation zone and at least one production well have been sunk, comprising injecting at least one aqueous urea solution into the injection well and pressure-injecting the aqueous urea solution through the perforation zone into the mineral oil deposit, wherein the aqueous urea solution on pressure injection into the mineral oil deposit is at a temperature of at least 80° C., wherein the at least one aqueous urea solution is heated to at least 80° C. in the injection well by means of electrical and/or inductive heating elements arranged above the perforation zone in the injection well. 
     
     
         2 . The process according to  claim 1 , wherein the at least one aqueous urea solution is injected into the at least one injection well in serial portions and pressure-injected into the deposit through the at least one perforation zone. 
     
     
         3 . The process according to  claim 1 , wherein the at least one aqueous urea solution is heated to at least 80° C. in two or more stages, the heating comprising the following stages:
 (a) heating to a temperature below 80° C., and 
 (b) heating to at least 80° C. 
 
     
     
         4 . The process according to  claim 3 , wherein stage (a) is performed outside the injection well and stage (b) within the injection well. 
     
     
         5 . The process according to  claim 1 , wherein the at least one urea solution on pressure injection into the mineral oil deposit is at a temperature below the boiling temperature of the at least one urea solution. 
     
     
         6 . The process according to  claim 1 , wherein the at least one aqueous urea solution is vaporized in the injection well prior to pressure injection into the deposit. 
     
     
         7 . The process according to  claim 1 , wherein, before and after the at least one aqueous urea solution, at least one portion of flooding water is injected through the at least one injection well and pressure-injected into the deposit, the flooding water on pressure injection having a temperature of at least 80° C. in each case. 
     
     
         8 . The process according to  claim 1 , wherein the at least one aqueous urea solution comprises 3 to 79% by weight of urea and 21 to 97% by weight of water, based on the total weight of the urea solution. 
     
     
         9 . The process according to  claim 1 , wherein the at least one aqueous urea solution comprises 0.1 to 5% by weight of at least one surface-active component, based on the total weight of the urea solution. 
     
     
         10 . The process according to  claim 1 , wherein the at least one aqueous urea solution comprises 5 to 30% by weight of at least one ammonium salt, based on the total weight of the urea solution. 
     
     
         11 . The process according to  claim 1 , wherein the ratio of water to urea in the at least one aqueous urea solution is 21 to 25% by weight of water to 75 to 79% by weight of urea, based on the total weight of water and urea. 
     
     
         12 . The process according to  claim 1 , wherein, alternately with the at least one aqueous urea solution, at least one further aqueous flood solution comprising at least one additive selected from surface-active components and ammonium salts is injected into the at least one injection well and pressure-injected into the deposit. 
     
     
         13 . The process according to  claim 12 , wherein there is no heating in the injection well on injection of the at least one further flood solution comprising at least one additive selected from surface-active components and ammonium salts into the injection well and pressure injection into the deposit. 
     
     
         14 . The process according to  claim 1 , wherein the heating elements are arranged above the perforation zone in the lower region of the injection well. 
     
     
         15 . The process according to  claim 1 , wherein the aqueous urea solution is heated or vaporized by the heating elements until at least 90% of the urea is present in hydrolyzed form.