In-situ combustion recovery process using single horizontal well to produce oil and combustion gases to surface

Abstract

An in-situ combustion process which process does not employ one or more separate gas venting wells. At least one vertical production well having a substantially vertical portion extending downwardly into the reservoir and a horizontal leg portion extending horizontally outwardly therefrom completed relatively low in the reservoir is provided. At least one vertical oxidizing gas injection well, positioned above and in spaced relation to the horizontal well, is positioned laterally along the horizontal well approximately midsection thereof. Oxidizing gas is injected therein and combustion fronts are caused to progress outwardly from such injection well in mutually opposite directions along the horizontal well. Preferably a plurality of injection wells are provided along the direction of the horizontal well, and oxidizing gas is injected in each and combustion fronts caused to progress outwardly and in opposite directions from each, and oil is caused to drain down into the horizontal well, which oil along with hot combustion gases is produced to surface.

What is claimed is: 
     
         1 . An improved in-situ combustion process for reducing the viscosity of oil contained in an oil-containing reservoir and recovering said oil, along with combustion gases, from the reservoir, which process does not employ one or more separate combustion gas venting wells, comprising:
 (a) providing at least one production well having a substantially vertical portion extending downwardly into said reservoir, and having a horizontal leg portion in fluid communication with said vertical portion and extending horizontally outwardly therefrom, said horizontal leg portion completed relatively low in the reservoir;   (b) providing at least one injection well in a region intermediate opposite ends of said horizontal leg portion and in spaced relation to said horizontal leg portion and positioned substantially directly above said horizontal leg portion, for injecting an oxidizing gas into said reservoir above said horizontal leg portion and in a region intermediate mutually opposite ends of said horizontal leg portion ;   (c) injecting an oxidizing gas through said at least one injection well and initiating combustion of hydrocarbons in said reservoir proximate said injection well so as to establish at least one or more combustion fronts above said horizontal leg portion, said one or more combustion fronts causing oil in said reservoir to become reduced in viscosity above said horizontal leg portion and to drain downwardly into said horizontal leg portion;   (d) allowing high temperature combustion gases along with said oil of reduced viscosity to be together collected in said horizontal leg portion; and   (e) producing said high temperature gases and said oil to surface; and   (f) separating at the heel of said horizontal well or at surface said oil from said high temperature combustion gases.   
     
     
         2 . The process of  claim 1 , wherein said at least one injection well injects oxidizing gas into said formation via said at least one injection well at less than fracturing pressure. 
     
     
         3 . The process of  claim 1  or  2 , wherein said at least one injection well comprises at least one vertical injection well situated along a length of the horizontal well and intermediate mutually opposite ends thereof, extending downwardly from surface towards said horizontal leg portion, and upon injection of oxidizing gas and ignition thereof said injection well supplies said oxidizing gas to at least two combustion fronts which each move in opposite directions outwardly from said vertical injection well and in a direction along said horizontal leg portion of said production well. 
     
     
         4 . The process of  claim 1 ,  2 , or  3  wherein a plurality of vertical injection wells are placed above and along a length of the horizontal well, and a combustion front is initiated at each injection well which progresses outwardly from each injection well in opposite directions, along a line of said horizontal well. 
     
     
         5 . The process of  claim 1  or  2 , wherein said at least one injection well comprises a horizontal injection well extending both above and along said horizontal leg portion of said production well, for injecting said oxidizing gas above said horizontal leg portion of said production well. 
     
     
         6 . The process of  claim 5 , wherein said at least one injection well injects oxidizing gas into the formation at a plurality of locations above said horizontal leg portion, so as to establish at least a pair of combustion fronts at each location which advance laterally outwardly from each location in opposite directions along said horizontal leg portion of said production well in a direction along said horizontal leg portion of said production well. 
     
     
         7 . The process of  claim 1 , wherein said hot combustion gases are subsequently used to heat water. 
     
     
         8 . The process of  claim 7 , wherein said heated water is subsequently used to produce steam for use in producing electrical power using turbines. 
     
     
         9 . The process of  claim 1 , wherein said high temperature combustion gases are used or further burned to produce electricity using gas turbines or steam turbines. 
     
     
         10 . The process of any one of  claims 1 - 9  wherein a tubing is placed within the horizontal leg portion of said production well, and a medium selected from the group of mediums comprising water, steam, non-oxidizing gas including CO 2 , hydrocarbon diluent, and mixtures thereof, is injected therein. 
     
     
         11 . The process of  claim 1  wherein the inner diameter of the horizontal leg portion of the production well is greater than 3 inches. 
     
     
         12 . The process of  claim 11  wherein the inner diameter of the horizontal leg portion of the production well is greater than 5 inches. 
     
     
         13 . The process of  claim 12  wherein the inner diameter of the horizontal leg portion of the production well is greater than 7 inches. 
     
     
         14 . The process of any one of  claims 1 - 6  and  10  wherein the oxidizing gas contains oxygen and CO 2 . 
     
     
         15 . The process of any one of  claims 1 - 6  wherein the oxidizing gas injection pressure is limited to a maximum of less than 50% over the reservoir pressure by adjusting the oxidizing gas injection rate. 
     
     
         16 . An improved in-situ combustion process for reducing the viscosity of oil contained in an oil-containing reservoir and recovering said oil, along with combustion gases, from the reservoir, which process does not employ one or more separate combustion gas venting wells, comprising:
 (a) drilling at least one production well having a substantially vertical portion extending downwardly into said reservoir and having a horizontal leg portion in fluid communication with said vertical portion and extending horizontally outwardly therefrom, said horizontal leg portion completed relatively low in the reservoir;   (b) drilling at least one injection well located directly above said horizontal leg portion and in alignment therewith, positioned or extending intermediate opposite ends of said horizontal leg portion;   (c) injecting an oxidizing gas into said reservoir via said at least one injection well at a location above said horizontal leg portion and intermediate opposite ends of said horizontal leg portion ;   (d) initiating in situ combustion in said reservoir proximate said injection well so as to form at least a pair of vertically-extending combustion fronts advancing laterally in opposite directions along said horizontal leg portion, said combustion fronts causing oil in said formation to become reduced in viscosity and to drain downwardly into said horizontal leg portion;   (e) collecting high temperature combustion gases along with said oil of reduced viscosity in said horizontal leg; and   (f) producing such high temperature gases and oil to surface; and   (g) separating at the heel of said horizontal well or at surface said oil from said high temperature gases.   
     
     
         17 . The method as claimed in  claim 16 , wherein said step of drilling at least one injection well comprises drilling at least one vertical injection well intermediate opposite ends of said horizontal leg portion, and said step of initiating in situ combustion comprises initiating combustion proximate said at least one vertical injection well so as to form at least a pair of vertically-extending combustion fronts advancing laterally in opposite directions along said horizontal leg portion 
     
     
         18 . The method as claimed in  claim 17 , wherein said step of drilling at least one vertical injection well comprises drilling a plurality of vertical injections wells, and said step of initiating in situ combustion comprises initiating combustion proximate one of said plurality of vertical injection wells situated along said horizontal leg portion and intermediate opposite ends thereof, so as to thereby form a pair of vertically-extending combustion fronts advancing laterally in opposite directions along said horizontal leg portion, and upon said pair of vertically-extending combustion fronts advancing respectively and laterally along said horizontal well bore past a further one of said plurality of injection wells, oxidizing gas is injected into said reservoir at said further one of said injection wells. 
     
     
         19 . The method as claimed in  claim 17 , wherein said step of drilling at least one injection well comprises drilling a plurality of vertical injection wells directly above said horizontal leg portion and in alignment therewith and positioned intermediate opposite ends of said horizontal leg portion, said step of initiating in situ combustion comprising initiating combustion proximate each of said plurality of vertical injection wells so as to thereby form pairs of vertically-extending combustion fronts advancing laterally in opposite directions along said horizontal leg portion and outwardly from each of said plurality of vertical injection wells. 
     
     
         20 . The method as claimed in  claim 16 , wherein said step of drilling at least one injection well comprises drilling an injection well directly above said horizontal leg portion and in alignment therewith and extending intermediate opposite ends of said horizontal leg portion, said step of injecting an oxidizing gas into said reservoir comprising injecting said oxidizing gas into said injection well and into the formation at locations above said horizontal leg portions and along said horizontal leg portion intermediate opposite ends of said horizontal leg portion; said step of initiating in-situ combustion comprising initiating combustion proximate each of said locations situated above and along said horizontal leg portion so as to at each location form pairs of combustion fronts advancing laterally in opposite directions along said horizontal leg portion and outwardly from each of said locations. 
     
     
         21 . An improved in-situ combustion process for reducing the viscosity of oil contained in an oil-containing reservoir and recovering said oil, along with combustion gases, from the reservoir, which process does not employ one or more separate combustion gas venting wells, comprising:
 (a) providing at least one production well having a substantially vertical portion extending downwardly into said reservoir and having a horizontal leg portion in fluid communication with said vertical portion and extending horizontally outwardly therefrom, said horizontal leg portion completed relatively low in the reservoir;   (b) providing a plurality of vertical injection wells positioned directly above said horizontal leg portion and in substantial alignment therewith, extending downwardly towards said horizontal leg portion;   (c) injecting an oxidizing gas into said reservoir via at least two of said vertical wells;   (d) initiating in situ combustion in said reservoir proximate said at least two vertical injection wells so as to form at each injection well a pair of vertically-extending combustion fronts which advance laterally in opposite directions along said horizontal leg portion and outwardly from each of said at least two vertical injection wells, said combustion fronts causing oil in said formation to become reduced in viscosity and to drain downwardly into said horizontal leg portion;   (e) collecting high temperature combustion gases along with said oil of reduced viscosity in said horizontal leg; and   (f) thereafter producing such high temperature gases and oil to surface; and   (g) separating at surface said oil from said high temperature gases.