Recovery From A Hydrocarbon Reservoir

Abstract

Methods and systems for recovering heavy oil, such as bitumen, by steam assisted gravity drainage (SAGD) from subterranean formations having a water and/or gas containing layer overlying a heavy oil containing layer. A fluid blocking agent is injected into the water and/or gas containing layer above at least one pair of horizontal wells. The blocking agent undergoes a change of density, viscosity or solidity when elevated to a temperature between an initial ambient reservoir temperature and 175 degrees by heat from steam used in the SAGD process, thereby creating a seal within the reservoir above the at least one pair of horizontal wells limiting or preventing movements of fluid through the seal.

What is claimed is: 
     
         1 . A method of recovering heavy oil from a hydrocarbon reservoir in which a water and/or gas containing layer overlies a heavy oil containing layer, the method comprising:
 providing an injection well in said water and/or gas containing layer above at least one pair of horizontal wells in said heavy oil containing layer for heavy oil recovery by a steam assisted gravity drainage process;   injecting a first blocking agent into said water and/or gas containing layer via said injection well to form a first region of said water and/or gas containing layer containing said first blocking agent adjacent an interface between said water and/or gas containing layer and said heavy oil containing layer above said at least one pair of horizontal wells; and   operating said steam assisted gravity drainage process via said at least one pair of horizontal wells by injecting steam into said heavy oil containing layer and recovering heavy oil from said heavy oil containing layer;   wherein said first blocking agent is injected into said water and/or gas containing layer before operating said steam assisted gravity drainage process or before heat generated by said steam assisted gravity drainage process reaches said first region of said water and/or gas containing layer; and   wherein said first blocking agent, when present in said first region, undergoes a change of viscosity, density or solidity when elevated to a temperature between an initial ambient reservoir temperature in said first region and 175° C. by heat from steam used in said steam assisted gravity drainage process, and thereby creates a seal within the hydrocarbon reservoir above said at least one pair of horizontal wells limiting or preventing movements of fluid through said seal.   
     
     
         2 . The method of  claim 1 , wherein said first blocking agent is in a form selected from the group consisting of a liquid, a flowable slurry, and a gel. 
     
     
         3 . The method of  claim 1 , wherein said first blocking agent is in a form of a liquid selected from the group consisting of a solution and an emulsion. 
     
     
         4 . The method of  claim 1 , wherein said first blocking agent has inverse-solubility characteristics such that the first blocking agent is configured to increase in viscosity, density or solidity with increase of temperature. 
     
     
         5 . The method of  claim 1 , wherein said first blocking agent increases in viscosity, density or solidity to form said seal within the reservoir when heated by heat from said steam to a temperature between initial ambient temperature of said first region and about 125° C. 
     
     
         6 . The method of  claim 1 , wherein said first blocking agent increases in viscosity, density or solidity to form said seal within the reservoir when heated by heat from said steam to a temperature between initial ambient temperature of said first region and about 100° C. 
     
     
         7 . The method of  claim 1 , wherein said first blocking agent comprises an aqueous solution of sodium silicate. 
     
     
         8 . The method of  claim 7 , further comprising introducing an additive into said aqueous solution, said additive being at least one compound selected from the group consisting of acids, chelating agents, pH modifiers and anti-scalants. 
     
     
         9 . The method of  claim 7 , wherein said sodium silicate is present in said aqueous solution at a concentration in a range of 1 to 10 wt. %. 
     
     
         10 . The method of  claim 7 , wherein said sodium silicate is present in said aqueous solution at a concentration in a range of 3 to 5 wt. %. 
     
     
         11 . The method of  claim 1 , wherein said first blocking agent comprises an aqueous solution of sodium bicarbonate. 
     
     
         12 . The method of  claim 1 , wherein said first blocking agent comprises colloidal silica. 
     
     
         13 . The method of  claim 1 , wherein said first blocking agent comprises a solution of silica and a soluble compound of a metal selected from the group consisting of Ca, Mg and Fe that forms insoluble metal silicates when subjected to heat from said steam. 
     
     
         14 . The method of  claim 1 , wherein, after injecting said first blocking agent into said water and/or gas containing layer, a second blocking agent is injected into said water and/or gas containing layer to form a second region above said at least one pair of horizontal wells, said second blocking agent undergoing an increase of density, viscosity or solidity when situated within said second region. 
     
     
         15 . The method of  claim 14 , wherein said second blocking agent is injected into said water and/or gas-containing layer via said injection well used for injection of said first blocking agent. 
     
     
         16 . The method of  claim 14 , wherein said second blocking agent is injected into said water and/or gas-containing layer via at least one injection well different from said injection well used for injection of said first blocking agent first. 
     
     
         17 . The method of  claim 14 , wherein said second blocking agent is a thermally-activated blocking agent having normal solubility characteristics such that said second blocking agent is configured to increase in viscosity, density or solidity with decrease of temperature when injected at elevated temperature into said water and/or gas containing layer. 
     
     
         18 . The method of  claim 14 , wherein said second blocking agent comprises an aqueous solution of silica injected into said water and/or gas containing layer at an elevated temperature above said ambient reservoir temperature. 
     
     
         19 . The method of  claim 18 , wherein said elevated temperature is a temperature of at least 80° C. 
     
     
         20 . The method of  claim 1 , wherein said steam assisted gravity drainage process comprises:
 injecting steam into said heavy oil containing layer via an uppermost one of said at least one pair of horizontal wells to heat heavy oil in said heavy oil containing layer to reduce viscosity of said heavy oil; and   removing the heavy oil from said heavy oil containing layer via a lowermost one of said at least one pair of horizontal wells.