Staggered horizontal well oil recovery process

Abstract

An in situ combustion process entailing the simultaneous production of oil and combustion gases that combines fluid drive, gravity phase segregation and gravity drainage to produce hydrocarbons from a subterranean oil-bearing formation, comprising initially injecting a gas through a pair of horizontal wells placed high in the formation and producing combustion gas and oil through parallel and laterally offset horizontal wells that are placed low in the formation intermediate the pair of horizontal wells placed high in the formation.

1 . An in situ combustion method for recovering oil from a hydrocarbon-containing subterranean reservoir, comprising the steps of:
 (i) drilling a pair of parallel, spaced-apart, upper horizontal wells within said hydrocarbon-containing reservoir and within a horizontal plane therein;   (ii) drilling, relatively low in said reservoir, a lower horizontal well, situated below said upper horizontal wells and positioned substantially parallel to and intermediate said pair of upper horizontal wells;   (iii) injecting an oxidizing gas into each of said upper horizontal wells and injecting said oxidizing gas into said reservoir via apertures in each of said pair of upper horizontal wells;   (iv) igniting said oxidizing gas within said formation and causing oil in said formation intermediate said upper horizontal wells to become heated;   (v) recovering oil which has become heated and which has migrated downwardly in said subterranean reservoir, in said lower horizontal well; and   (vi) recovering said oil from said lower horizontal well to surface.   
     
     
         2 . A method for recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 1 , comprising the further steps of:
 (a) drilling a further upper horizontal well within an upper region of said hydrocarbon-containing reservoir substantially parallel to and laterally spaced apart from said upper horizontal wells;   (b) drilling a further lower horizontal well intermediate said further upper horizontal well and a nearest of said upper horizontal wells, positioned below said upper horizontal wells and positioned substantially parallel therewith;   (c) injecting said oxidizing gas into said further upper horizontal well and into said nearest of said upper horizontal wells so as to thereby inject said oxidizing gas into said reservoir via a plurality of apertures in said further upper horizontal well and said nearest of said upper horizontal wells;   (d) collecting oil which has become heated as a result of heat being produced during combustion of said oxidizing gas and hydrocarbons in said reservoir and which has migrated downwardly in said subterranean reservoir, in said further lower horizontal well;   (e) recovering said oil from said further lower horizontal well to surface.   
     
     
         3 . A method for recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 2 , comprising the further steps of:
 (f) successively repeating steps (a)-(e) to thereby progress in a linear direction with drilled horizontal wells so as to progressively recover oil in said linear direction from said underground hydrocarbon reservoir.   
     
     
         4 . A method for recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 1 ,  2 , or  3 , wherein hot combustion gases are further drawn into and recovered to surface from said lower horizontal well along with said oil. 
     
     
         5 . A method for recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 1  wherein said step of injecting said oxidizing gas into said upper injection wells comprises the step of injecting said oxidizing gas into proximal ends of said upper horizontal wells situated on a side of said underground formation, and said step of withdrawing oil from said lower horizontal well comprises withdrawing said oil from a proximal end of said lower horizontal well which is situated on another side of said reservoir opposite said side at which said proximal ends of said upper horizontal wells are situated. 
     
     
         6 . A method for recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 1  wherein said step of injecting said oxidizing gas into said upper horizontal wells comprises the step of injecting said oxidizing gas into proximal ends of said upper horizontal wells situated on a side of said underground formation, and said step of withdrawing oil from said lower horizontal well comprises withdrawing said oil from a distal ends of said lower horizontal well situated on another side of said reservoir opposite said side at which said proximal ends of said upper horizontal wells are situated. 
     
     
         7 . A method for recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 6 , wherein production tubing is positioned in said lower horizontal well and which tubing has an open end proximate a distal end of said lower horizontal well, said step of recovering oil from said lower horizontal well comprising the step of recovering said oil via said open end of said tubing. 
     
     
         8 . A method for recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 1  wherein production tubing is positioned in each of said upper horizontal wells and which tubing has an open end proximate a respective distal end of each of said upper horizontal wells, said step of injecting oxidizing gas into said formation comprising injecting said oxidizing gas into said tubing situated in each of said upper horizontal wells and thus into distal ends thereof, and said step of withdrawing oil from said lower horizontal well comprises withdrawing said oil from a proximal end of said lower horizontal well which is situated on a same side of said reservoir on which proximal ends of said upper horizontal wells are situated. 
     
     
         9 . A method for recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 1 , wherein each of said upper horizontal wells has a well liner in which said plurality of apertures are situated, and wherein a size of said apertures or a number of said apertures within said well liner progressively increases from a proximal end to a distal end of said upper horizontal wells, and said oxidizing gas is injected into said proximal end of each of said upper horizontal wells. 
     
     
         10 . A method for recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 1 , wherein said lower horizontal well has a well liner in which a plurality of apertures are situated, and wherein a size of said apertures or a number of said apertures within said well liner progressively increases from a proximal end to a distal end of said lower horizontal well, and said oil is recovered from said proximal end of said lower horizontal well. 
     
     
         11 . A method for recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claims 9  and  10 . 
     
     
         12 . A method for recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 11 , wherein proximal ends of said upper wells and proximal ends of said lower horizontal wells are situated on a same side of said reservoir. 
     
     
         13 . A method for recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 1 , wherein a volume of said oxidizing gas injected into said subterranean reservoir is equal or less than a volume of oil recovered from said horizontal wells located low in the reservoir. 
     
     
         14 . A method of recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 1 , wherein said oxidizing gas comprises oxygen or air. 
     
     
         15 . A method of recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 1 , wherein said oxidizing gas further comprises water, steam, or carbon dioxide. 
     
     
         16 . A line-drive method for recovering oil from a hydrocarbon-containing subterranean reservoir, comprising the steps of:
 (i) drilling a pair of parallel, spaced-apart, upper horizontal wells within an upper region of said hydrocarbon-containing reservoir, substantially coplanar with each other;   (ii) drilling, relatively low in said reservoir, a lower horizontal well, situated below said upper horizontal wells and positioned substantially parallel to and intermediate said pair of upper horizontal wells;   (iii) injecting an oxidizing gas into each of said upper horizontal wells and injecting said oxidizing gas into said reservoir via apertures in each of said pair of upper horizontal wells;   (iv) igniting said oxidizing gas within said formation and causing oil in said formation intermediate said upper horizontal wells to become heated;   (v) recovering oil which has become heated and which has migrated downwardly in said subterranean reservoir, in said lower horizontal well and recovering said oil from said lower horizontal well to surface.   (vi) drilling a further upper horizontal well within an upper region of said hydrocarbon-containing reservoir substantially parallel to and laterally spaced apart from said upper horizontal wells;   (vii) drilling a further lower horizontal well intermediate said further upper horizontal well and a nearest of said upper horizontal wells, positioned below said upper horizontal wells and positioned substantially parallel therewith;   (viii) injecting said oxidizing gas into said further upper horizontal well and into said nearest of said upper horizontal wells so as to thereby inject said oxidizing gas into said reservoir via a plurality of apertures in said further upper horizontal well and said nearest of said upper horizontal wells;   (ix) collecting oil which has become heated as a result of heat being produced during combustion of said oxidizing gas and hydrocarbons in said reservoir and which has migrated downwardly in said subterranean reservoir, in said further lower horizontal well;   (x) recovering said oil from said further lower horizontal well to surface; and   (xi) successively repeating steps (vi)-(x) to thereby progress in a linear direction with drilled horizontal wells so as to progressively recover oil in said linear direction from said underground hydrocarbon reservoir.   
     
     
         17 . A method of recovering oil from a hydrocarbon-containing subterranean reservoir as claimed in  claim 16 , wherein said oxidizing gas comprises a mixture of
 (i) air and steam;   (ii) air and suspended water droplets; or   (iii) air and water vapour.