Method of producing viscous hydrocarbons by steam-assisted gravity drainage

Abstract

A non-cemented liner ( 20 ) is introduced into an injection bore ( 21 ), steam is fed into the liner at a first bore part ( 24 ) and injected into the reservoir through holes ( 22, 23 ) in the liner distributed so that the total hole area per length unit of the liner is greater at a second part ( 25 ) than at the first part of the bore. Steam enters an annular space between liner and bore only through holes near first part of the bore and subsequently gradually travels inside the liner in direction of second bore part and gradually enters the annular space through holes nearer and nearer second bore part. Gradually liquid is displaced away from an upper liner part and an upper part of the annular space, so that steam contacts the bore along substantially the entire length of the liner in the upper part of the annular space.

1 . A method of producing viscous hydrocarbons by steam-assisted gravity drainage (SAGD), comprising:
 injecting steam into a hydrocarbon reservoir via an injection well bore placed above a production well bore, so that heat is transferred from the steam to the reservoir fluids and thereby reduces the viscosity of hydrocarbons of the reservoir, thereby facilitating recovery of hydrocarbons via the production well bore, wherein a liner is introduced into the injection well bore so that it extends from a first part of the injection well bore to a second part of the injection well bore as a non-cemented liner, and wherein the steam is fed into the liner at the first part of the injection well bore and is injected into the hydrocarbon reservoir through a number of holes formed in a wall of the liner, wherein an annular space is formed between the liner and the injection well bore in which annular space steam injected through the liner may travel along the outside of the liner and contact the injection well bore along the entire length of the liner, and wherein the holes are distributed so that the total hole area per length unit of the liner is greater at the second part of the injection well bore than at the first part of the injection well bore and so that, during a start-up phase, initially, the steam enters the annular space only through holes near the first part of the injection well bore, and subsequently the steam gradually travels inside the liner in the direction of the second part of the injection well bore and thereby gradually enters the annular space through holes nearer and nearer the second part of the injection well bore, thereby gradually displacing liquid away from an upper part of the liner and away from an upper part of the annular space, so that, during the start-up phase, finally, steam contacts the injection well bore along at least substantially the entire length of the liner in the upper part of the annular space; and   injecting acid into the hydrocarbon reservoir via the injection well bore before that steam is injected into the hydrocarbon reservoir via the injection well bore.   
     
     
         2 . The method according to  claim 1 , wherein an end opening of the liner located at the second part of the injection well bore is closed or at least substantially closed against the injection well bore, preferably via an end cap or the like. 
     
     
         3 . The method according to  claim 1 , wherein steam is introduced into the liner only from the end at the first part of the injection well bore. 
     
     
         4 . The method according to  claim 1 , wherein the first part of the injection well bore is the inner part at the heel of the injection well bore, and wherein the second part of the injection well bore is the outer part at the toe of the injection well bore. 
     
     
         5 . The method according to  claim 1 , wherein the liner includes top holes pointing upwards for diverting the steam into the reservoir and bottom holes pointing downwards in order for condensed water and initial well bore fluids to escape from the liner. 
     
     
         6 . The method according to  claim 1 , wherein the liner is inserted into the injection well bore by connecting a number of liner sections at random angular rotation in relation to each other, and wherein each liner section includes at least one set of at least two holes arranged with a regular spacing in the circumferential direction of the liner section. 
     
     
         7 . The method according to  claim 6 , wherein each liner section includes at least one set of two holes arranged with a spacing of approximately 180 degrees in the circumferential direction of the liner section. 
     
     
         8 . The method according to  claim 6 , wherein the holes of the at least one set of at least two holes have corresponding or equal cross-sectional area. 
     
     
         9 . The method according to  claim 6 , wherein all the holes included by each set of holes are arranged at the same length position of the liner section. 
     
     
         10 . The method according to  claim 1 , wherein the total hole area per length unit of the liner gradually increases from the first part of the injection well bore to the second part of the injection well bore. 
     
     
         11 . The method according to  claim 1 , wherein the total hole area per length unit of the liner at a part of the second part of the injection well bore is at least 2 times, preferably at least 3 times and most preferred at least or about 4 times the total hole area per length unit of the liner at a part of the first part of the injection well bore. 
     
     
         12 . The method according to  claim 1 , wherein the holes in the liner has a diameter in the interval from about 0.5 mm to about 8 mm, and wherein the distance between holes in the liner at the second part of the injection well bore is less than 12 meters, preferably less than 9 meters and most preferred about 7.5 meters, and the distance between holes in the liner at the first part of the injection well bore is more than 24 meters, preferably more than 27 meters meters and most preferred about 30 meters meters. 
     
     
         13 . The method according to  claim 1 , wherein the liner has a diameter of between about 2.5 cm to about 18 cm. 
     
     
         14 . The method according to  claim 1 , wherein, over a length of the liner of not more than 20 metersmeters, preferably not more than 30 metersmeters and most preferred not more than 35 metersmeters, at least one hole is positioned at a top position of the liner, and at least one hole is positioned at a bottom position of the liner. 
     
     
         15 . The method according to  claim 2 , wherein steam is introduced into the liner only from the end at the first part of the injection well bore. 
     
     
         16 . The method according to  claim 7 , wherein the holes of the at least one set of at least two holes have corresponding or equal cross-sectional area. 
     
     
         17 . The method according to  claim 7 , wherein all the holes included by each set of holes are arranged at the same length position of the liner section. 
     
     
         18 . The method according to  claim 2 , wherein the first part of the injection well bore is the inner part at the heel of the injection well bore, and wherein the second part of the injection well bore is the outer part at the toe of the injection well bore. 
     
     
         19 . The method according to  claim 2 , wherein the liner includes top holes pointing upwards for diverting the steam into the reservoir and bottom holes pointing downwards in order for condensed water and initial well bore fluids to escape from the liner. 
     
     
         20 . The method according to  claim 2 , wherein the liner is inserted into the injection well bore by connecting a number of liner sections at random angular rotation in relation to each other, and wherein each liner section includes at least one set of at least two holes arranged with a regular spacing in the circumferential direction of the liner section.