In situ thermal processing of an oil shale formation having permeable and impermeable sections
An oil shale formation may be treated using an in situ thermal process. Heat may be provided to a formation from one or more heat sources in the formation. Hydrocarbons within the formation may be pyrolyzed. Hydrocarbons, H 2 , and/or other formation fluids may be produced from the formation. In some embodiments, the formation may include a relatively impermeable portion and/or a relatively permeable portion.
1. A method for treating an oil shale formation in situ, comprising:
providing heat from one or more heaters to at least a portion of the formation;
allowing the heat to transfer from the one or more heaters to a first section of the formation such that the heat from the one or more heaters pyrolyzes at least some hydrocarbons in the first section;
producing a mixture through a second section of the formation, wherein the produced mixture comprises at least some pyrolyzed hydrocarbons from the first section, and wherein the second section comprises a higher permeability than the first section; and
forming one or more fractures that propagate between the first section and the second section.
2. The method of claim 1 , wherein the heat provided from at least one of the heaters is transferred to the formation substantially by conduction.
3. The method of claim 1 , wherein the mixture is produced from the formation when a partial pressure of hydrogen in at least a portion the formation is at least about 0.5 bars.
4. The method of claim 1 , further comprising increasing permeability in the second section by allowing heat to transfer from one or more of the heaters to the second section.
5. The method of claim 1 , wherein the second section has a higher permeability than the first section before providing heat to the formation.
6. The method of claim 1 , wherein the second section comprises an average permeability thickness product of greater than about 100 millidarcy feet.
7. The method of claim 1 , wherein the first section comprises an initial average permeability thickness product of less than about 10 millidarcy feet.
8. The method of claim 1 , wherein the second section comprises an average permeability thickness product that is at least twice an initial average permeability thickness product of the first section.
9. The method of claim 1 , wherein the second section comprises an average permeability thickness product that is at least ten times an initial average permeability thickness product of the first section.
10. The method of claim 1 , wherein one or more of the heaters are placed in one or more uncased wellbores in the formation.
11. The method of claim 10 , further comprising allowing at least some hydrocarbons from the first section to propagate through at least one of the uncased wellbores into the second section.
12. The method of claim 10 , further comprising producing at least some hydrocarbons through at least one of the uncased wellbores.
13. The method of claim 1 , further comprising allowing at least some hydrocarbons from the first section to propagate through one or more of the fractures into the second section.
14. The method of claim 1 , further comprising producing the mixture from the formation through a production well placed in the second section.
15. The method of claim 1 , further comprising producing the mixture from the formation through a production well placed in the first section and in the second section.
16. The method of claim 1 , further comprising inhibiting fracturing of a section of the formation that is substantially adjacent to an environmentally sensitive area.
17. The method of claim 1 , further comprising producing at least some hydrocarbons through the second section to maintain a pressure in the formation below a lithostatic pressure of the formation.
18. The method of claim 1 , further comprising producing at least some hydrocarbons through a production well placed in the first section.
19. The method of claim 1 , further comprising pyrolyzing at least some hydrocarbons in the second section.
20. The method of claim 1 , wherein the first section and the second section are substantially adjacent.
21. The method of claim 1 , further comprising allowing migration of fluids between the first section and the second section.
22. The method of claim 1 , wherein at least one of the heaters comprises a conductor having a thickness that is adjusted to provide more heat to the first section than to the second section.
23. A method for treating an oil shale formation in situ, comprising:
providing heat from one or more heaters to at least a portion of the formation, wherein one or more of the heaters are placed in one or more uncased wellbores in the formation;
allowing the heat to transfer from the one or more heaters to a first section of the formation such that the heat from the one or more heaters pyrolyzes at least some hydrocarbons in the first section;
allowing at least some hydrocarbons from the first section to propagate through at least one of the uncased wellbores into a second section of the formation; and
producing a mixture through the second section of the formation, wherein the produced mixture comprises at least some pyrolyzed hydrocarbons from the first section, and wherein the second section comprises a higher permeability than the first section.
24. The method of claim 23 , further comprising producing at least some hydrocarbons through at least one of the uncased wellbores.
25. The method of claim 23 , wherein the mixture is produced from the formation when a partial pressure of hydrogen in at least a portion of the formation is at least about 0.5 bars.
26. The method of claim 23 , wherein the second section comprises an average permeability thickness product that is at least twice an initial average permeability thickness product of the first section.
27. The method of claim 23 , further comprising inhibiting fracturing of a section of the formation that is substantially adjacent to an environmentally sensitive area.
28. The method of claim 23 , further comprising producing at least some hydrocarbons through the second section to maintain a pressure in the formation below a lithostatic pressure of the formation.
29. The method of claim 23 , further comprising producing at least some hydrocarbons through a production well placed in the first section.
30. The method of claim 23 , further comprising pyrolyzing at least some hydrocarbons in the second section.
31. The method of claim 23 , wherein at least one of the heaters comprises a conductor having a thickness that is adjusted to provide more heat to the first section than to the second section.
32. A method for treating an oil shale formation in situ, comprising:
providing heat from one or more heaters to at least a portion of the formation, wherein at least one of the heaters comprises a conductor having a thickness that is adjusted to provide more heat to a first section of the formation than to a second section of the formation;
allowing the heat to transfer from the one or more heaters to the first section of the formation such that the heat from the one or more heaters pyrolyzes at least some hydrocarbons in the first section; and
producing a mixture through the second section of the formation, wherein the produced mixture comprises at least some pyrolyzed hydrocarbons from the first section, and wherein the second section comprises a higher permeability than the first section.
33. The method of claim 32 , wherein the mixture is produced from the formation when a partial pressure of hydrogen in at least a portion the formation is at least about 0.5 bars.
34. The method of claim 32 , wherein the second section comprises an average permeability thickness product that is at least twice an initial average permeability thickness product of the first section.
35. The method of claim 32 , further comprising inhibiting fracturing of a section of the formation that is substantially adjacent to an environmentally sensitive area.
36. The method of claim 32 , further comprising producing at least some hydrocarbons through the second section to maintain a pressure in the formation below a lithostatic pressure of the formation.
37. The method of claim 32 , further comprising producing at least some hydrocarbons through a production well placed in the first section.
38. The method of claim 32 , further comprising pyrolyzing at least some hydrocarbons in the second section.