Method for diverting steam in thermal recovery process

• US 4,612,990 A
• Filed: 12/13/1984
• Issued: 09/23/1986
• Est. Priority Date: 08/01/1983
• Status: Expired due to Fees

• Current Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Original Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Inventors: Shu, Winston R.
• Primary Examiner(s): Leppink, James A.
• Assistant Examiner(s): Neuder, William P.
• Application Number:
  US06/681,343
• Time in Patent Office: 649 Days
• Field of Search: 166/272, 166/274, 166/288, 166/303
• US Class Current: 166/272.3
• CPC Class Codes: E21B 43/24 using heat, e.g. steam injection

Abstract

The sweep efficiency of a steam flooding process is improved by injecting steam into the lower portion of the formation through an injection well until steam channeling or steam overriding has occurred, after which steam injection is terminated and an oxygen-containing gas such as air, oxygen-enriched air, or oxygen is injected into the formation to oxidize the residual oil in the portion of the formation where steam override or channeling has occurred. This forms an asphaltic material that decreases the permeability of that zone. Thereafter, steam injection is resumed and as a consequence of the oxidized asphaltic material plug, the steam moves into portions of the formation to mobilize viscous oil not swept by the initial injection of steam. During injection of the oxygen-containing gas production of oil may be terminated or continued. Multiple cycles of steam and oxygen-containing gas injection may be applied to a formation to better control sweep efficiency.

Claims

1. A method of recovering viscous oil from a subterranean, viscous oil-containing, permeable formation penetrated by an injection well which is in fluid communication with the lower one-third to one-half of the formation and a prouction well which is in fluid communication with a substantial portion of the formation, comprising:

(a) injecting steam into the formation through the injection well and recovering fluid including oil from the formation by the production well for a predetermined period of time, forming a steam-swept zone and an unswept zone in the formation;

(b) shutting in the production well;

(c) injecting an oxygen-containing gas into the steam swept zone through the injection well in an amount of 0.5 to 1.5 MSCF of oxygen per barrel of residual oil in the steam-swept zone, sufficient to oxidize residual oil in the steam-swept zone and sufficient to form a viscous asphaltic material in that zone, decreasing its permeability until the injection pressure increases; and

(d) thereafter injecting steam only into the formation through the injection well and recovering fluid including oil from said unswept zone of the formation through the production well until the fluid recovered from the production well comprises an unfavorable amount of steam or water.

2. A method according to claim 1 in which the oxygen-containing gas is injected into the steam swept zone in the absence of added water.

3. A method according to claim 1 in which the oxygen-containing gas is air.

4. A method according to claim 1 wherein the oxygen-containing gas is essentially pure oxygen.

5. A method according to claim 1 in which step (a) is continued until the fluid being recovered from the production well includes a predetermined amount of steam or water.

6. A method according to claim 1 wherein the amount of the oxygen-containing gas injected during step (c) is about 0.5 to 1.5 MSCF of oxygen per barrel of residual oil in the steam-swept zone.

7. A method according to claim 1 in which steps (a) through (d) are repeated for a plurality of cycles.

8. A method of recovering viscous oil from a subterranean, viscous oil-containing, permeable formation penetrated by an injection well which is in fluid communication with the lower one-third to one-half of the formation and a production well which is in fluid communication with a substantial portion of the formation, comprising:

(a) injecting steam into the formation through the injection well and recovering fluid including oil from the formation by the production well to form a steam-swept zone and an unswept zone in the formation;

(b) continuing to recover fluid including oil from the formation through the production well and simultaneously injecting an oxygen-containing gas into the steam swept zone through the injection well to oxidize residual oil in the steam-swept zone and form a viscous asphaltic material in that zone, decreasing its permeability until the injection pressure increases; and

(c) thereafter injecting steam only into the formation through the injection well and recovering fluid including oil from said unswept zone of the formation through the production well until the fluid recovered from the production well comprises an unfavorable amount of steam or water.

9. A method according to claim 8 in which the oxygen-containing gas is injected into the formation in the absence of added water.

10. A method according to claim 9 in which the amount of oxygen-containing gas injected into the formation is from 1.0 to 7.5 MSCF of oxygen per barrel of residual oil in the steam swept zone.

11. A method according to claim 8 in which the oxygen-containing gas is air.

12. A method according to claim 8 in which the oxygen-containing gas is oxygen-enriched air.

13. A method according to claim 8 in which the oxygen-containing gas is essentially pure oxygen.

14. A method according to claim 8 in which step (a) is continued until the fluid being recovered from the production well comprises a predetermined amount of steam or water.

15. A method according to claim 8 in which steps (a) through (c) are repeated for a plurality of cycles.

20. The method as recited in claim 11 where in step (b) said production well is shut in during the injection of said oxygen-containing gas which is injected at about 0.5 to about 1.5 MSCF of oxygen per barrel of residual oil.

16. A method for recovering hydrocarbonaceous fluids from an unswept area of a viscous hydrocarbonaceous fluid bearing formation having a swept area therein where said swept area contains residual oil and where both areas are penetrated by an injection well which is in fluid communication with a spaced apart production well comprising:

(a) injecting steam into said formation through said injection well and recovering fluids including oil from said formation via said production well for a predetermined period of time from said swept zone;

(b) injecting simultaneously via said injection well an oxygen-containing gas into said swept zone in an amount sufficient to oxidize said residual oil in said swept zone for a time sufficient to form a viscous asphaltic material from said residual oil in said swept zone thereby decreasing its permeability causing an increase in the injection pressure;

(c) ceasing injection of said oxygen-containing gas and continuing injection of said steam; and

(d) recovering fluids including hydrocarbonaceous fluids from said unswept area via said production well.

17. The method as recited in claim 16 where in step (a) steam injection is continued until said recovered fluids contain a predetermined amount of water or steam.

18. The method as recited in claim 16 where in step (a) steam injection is continued until steam break through occurs.

19. The method as recited in claim 16 where in step (b) said oxygen-enriched air is a member selected from the group consisting of air, oxygen-enriched air, and substantially pure oxygen.

21. The method as recited in claim 16 where steps (a), (b), (c) and (d) are repeated until the pore volumes previously swept by steam are largely plugged by oxidation of residual oil.