Method for producing viscous hydrocarbon using incremental fracturing

Abstract

A method for producing viscous hydrocarbon formations involves the use of a downhole burner. The well undergoes a mild hydraulic fracturing process that limits the fractured zone to a relatively small dimension so as to avoid intersecting any drainage zones of adjacent wells. The operator pumps fuel, steam and oxygen to the burner, which bums the fuel, causing the flow of hot, gaseous fluids into the fractured zone. The steam delivered from the surface cools the burner and becomes superheated as it enters the fractured zone. The operator allows the fractured zone to soak, then produces the oil. After the production declines, the operator may repeat the fracturing to incrementally increase the fractured zone, then repeat the injection and soak cycles.

1 . A method for producing a viscous hydrocarbon from a well, comprising: 
 (a) hydraulically fracturing a viscous hydrocarbon formation surrounding the well, creating a limited fractured zone surrounded by an unfractured portion of the formation;    (b) securing a downhole burner in the well;    (c) pumping a fuel into the burner and burning the fuel in the burner;    (d) creating superheated steam in the burner and injecting the superheated steam into the fractured zone to heat the hydrocarbon therein, and impeding the escape of the superheated steam into the surrounding unfractured portion of the formation; then    (e) flowing hydrocarbon from the fractured zone up the well; then    (f) at a selected time, hydraulically fracturing the formation again to increase the extent of the fractured zone, and repeating steps (c), (d) and (e).    
   
   
       2 . The method according to  claim 1 , wherein the extent of the fractured zone created in step (a) is less than one-half a distance to any adjacent wells.  
   
   
       3 . The method according to  claim 1 , wherein the extent of the fractured zone created in step (a) is limited so as to avoid intersecting any drainage zones of any adjacent wells.  
   
   
       4 . The method according to  claim 1 , further comprising: 
 allowing the fractured zone to soak for a selected time after step (d) and before step (e) by stopping steps (c) and (d) other than to maintain the formation pressure at a desired level until beginning step (e).    
   
   
       5 . The method according to  claim 1 , wherein: 
 steps (c) and (d) create a solution gas and causes a formation pressure within the fractured zone to increase; and wherein step (e) comprises using the solution gas as a source to force the hydrocarbon into and up the well in step (e).    
   
   
       6 . The method according to  claim 1 , wherein step (d) comprises pumping partially saturated steam to the burner and flowing a portion of the partially saturated steam through a jacket around the burner to cool the burner and convert the partially saturated steam to superheated steam.  
   
   
       7 . The method according to  claim 1 , wherein step (f) is performed without removing the burner.  
   
   
       8 . A method for producing a viscous hydrocarbon from two adjacent wells, both of which extend into the same viscous hydrocarbon formation, comprising: 
 (a) hydraulically fracturing the hydrocarbon formation surrounding each of the wells, creating a separate fractured zone around each of the wells, and limiting the extent of the fractured zones so that they do not intersect each other, leaving unfractured portions of the formation surrounding each of the fractured zones;    (b) injecting steam into each of the fractured zones and impeding the escape of the steam from the fractured zones into the unfractured portions of the formation surrounding each of the fractured zones; then    (c) flowing hydrocarbon from each of the fractured zones up the well; and    (d) when the flow of hydrocarbon drops below a selected minimum in each of the wells, hydraulically fracturing the formation in each of the wells again to create enlarged fractured zones around each well, and limiting the extents of the enlarged fractured zones so as to avoid them intersecting each other; then repeating steps (b) and (c).    
   
   
       9 . The method according to  claim 8 , further comprising allowing the fractured zones to soak for a selected time after step (b) and before starting step (c), and while soaking, ceasing step (b) other than to maintain a desired pressure in each of the fractured zones.  
   
   
       10 . A method for producing a viscous hydrocarbon from a well, comprising: 
 (a) hydraulically fracturing a viscous hydrocarbon formation to create a fractured zone, but limiting an extent of the fractured zone so that the fractured zone is surrounded by an unfractured portion of the formation;    (b) securing a downhole burner in the well;    (c) pumping hydrogen, oxygen and partially saturated steam down the well to the burner, burning a portion of the hydrogen, cooling the burner with the partially saturated steam, and heating the partially saturated steam to create superheated steam;    (d) injecting the steam and unburned portions of the hydrogen from the burner into the fractured zone to heat the hydrocarbon and create a solution gas in the fractured zone, the unfractured portion of the formation impeding the escape of the heated steam and unburned portions of the hydrogen; then    (e) ceasing step (c) during a selected soak interval except for at least one repetition of step (c) to maintain a desired pressure in the fractured zone; then    (f) opening a valve at a wellhead and allowing the heated hydrocarbon to flow up the well driven at least in part by the solution gas; then    (g) repeating steps (a), (c), (d), (e) and (f).    
   
   
       11 . The method according to  claim 10 , wherein the hydraulic fracturing of step (a) is limited to have an outer periphery separated from a drainage zone of any adjacent wells.