Controlling and assessing pressure conditions during treatment of tar sands formations

• US 9,181,780 B2
• Filed: 04/18/2008
• Issued: 11/10/2015
• Est. Priority Date: 04/20/2007
• Status: Expired due to Fees

• Current Assignee: Shell Oil Company (Shell Plc)
• Original Assignee: Shell Oil Company (Shell Plc)
• Inventors: Zhang, Etuan, Beer, Gary Lee
• Primary Examiner(s): DiTrani, Angela M
• Application Number:
  US12/105,974
• Publication Number:
  US 20090321071A1
• Time in Patent Office: 2,762 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: C09K 8/845 containing inorganic compounds
• CPC Class Codes: C09K 8/86 containing organic compounds
• CPC Class Codes: C10G 1/008 Controlling or regulating of liquefaction processes
• CPC Class Codes: C10G 1/02 by distillation
• CPC Class Codes: C10G 1/04 by extraction
• CPC Class Codes: C10G 1/042 by the use of hydrogen-donor solvents
• CPC Class Codes: E21B 36/04 using electrical heaters
• CPC Class Codes: E21B 43/16 Enhanced recovery methods for obtaining hydrocarbons
• CPC Class Codes: E21B 43/24 using heat, e.g. steam injection
• CPC Class Codes: E21B 43/2401 by means of electricity
• CPC Class Codes: Y10T 29/49083 Heater type

Abstract

A method for treating a tar sands formation includes providing heat to at least part of a hydrocarbon layer in the tar sands formation from a plurality of heaters located in the formation. Heat is allowed to transfer from the heaters to at least a portion of the formation. A pressure in the portion of the formation is controlled such that the pressure remains below a fracture pressure of the formation overburden while allowing the portion of the formation to heat to a selected average temperature of at least about 280° C. and at most about 300° C. The pressure in the portion of the formation is reduced to a selected pressure after the portion of the formation reaches the selected average temperature.

Claims

1. A method for treating a tar sands formation, comprising:

providing heat to at least part of a hydrocarbon layer in the tar sands formation from a plurality of heaters located in the formation;

allowing the heat to transfer from the heaters to at least a portion of the formation;

allowing an average temperature of the portion of the formation to increase to a selected average temperature between about 280°

C. and about 300°

C. while maintaining a pressure in the portion of the formation below a fracture pressure of the formation overburden;

assessing the average temperature in the portion by assessing at least one property of gases produced while maintaining the pressure below the fracture pressure;

reducing the pressure in the portion of the formation to a lower pressure while the portion of the formation is at the selected average temperature;

increasing the average temperature of the portion of the formation to a temperature of at most about 350°

C. after reducing the pressure; and

producing, after the pressure is reduced to the lower pressure, at least some mobilized, visbroken, or pyrolyzed fluids from the portion of the formation at the lower pressure.

2. The method of claim 1, wherein the fracture pressure is between about 1000 kPa and about 15000 kPa.

3. The method of claim 1, wherein the lower pressure is a pressure below which hydrocarbon coking in the portion occurs when the average temperature in the portion is at most 300°

C.

4. The method of claim 1, wherein the lower pressure is between about 100 kPa and about 1000 kPa.

5. The method of claim 1, wherein the lower pressure is between about 200 kPa and about 800 kPa.

6. The method of claim 1, further comprising producing fluids from the portion to maintain the pressure below the fracture pressure.

7. The method of claim 1, wherein the selected average temperature is between about 285°

C. and about 295°

C.

8. The method of claim 1, further comprising providing a drive fluid to the portion.

9. The method of claim 1, further comprising providing steam to the portion.

10. The method of claim 1, further comprising:

producing fluids from the portion;

reducing heat output from two or more of the heaters after a selected time; and

continuing producing fluids from the portion after reducing the heat output from the two or more heaters.

11. The method of claim 1, further comprising increasing the average temperature of the portion while producing the at least some mobilized, visbroken, or pyrolyzed fluids from the portion of the formation at the lower pressure.

12. A method for treating a hydrocarbon containing formation, comprising:

providing heat to at least part of a hydrocarbon layer in the formation from a plurality of heaters located in the formation;

allowing the heat to transfer from the heaters to at least a portion of the formation;

allowing an average temperature of the portion of the formation to increase to a selected average temperature range while maintaining a pressure in the portion of the formation below a fracture pressure of the formation overburden;

producing at least some fluids from the formation to maintain the pressure below the fracture pressure;

assessing at least one property of gases in the fluids produced to maintain the pressure below the fracture pressure;

assessing the average temperature in the portion based on the at least one assessed property of the gases in the fluids produced to maintain the pressure below the fracture pressure;

reducing the pressure in the formation to a lower pressure while the portion of the formation is in the selected average temperature range;

increasing the average temperature of the portion of the formation to a temperature of at most about 350°

C. after reducing the pressure; and

producing, after the pressure is reduced to the lower pressure, at least some mobilized, visbroken, or pyrolyzed fluids from the portion of the formation at the lower pressure.

13. The method of claim 12, further comprising assessing the average temperature in the portion based on, at least in part, a hydrocarbon isomer shift in the fluids produced to maintain the pressure below the fracture pressure.

14. The method of claim 12, further comprising assessing the average temperature in the portion based on, at least in part, a weight percentage of saturates in the fluids produced to maintain the pressure below the fracture pressure.

15. The method of claim 12, further comprising assessing the average temperature in the portion based on, at least in part, a weight percentage of n-C₇ in the fluids produced to maintain the pressure below the fracture pressure.

16. The method of claim 12, wherein the selected average temperature range comprises a temperature range from about 280°

C. to about 300°

C.

17. The method of claim 12, wherein the selected average temperature range is below the temperature at which coking of hydrocarbons occurs in the portion.

18. The method of claim 12, further comprising providing steam to the portion.

19. The method of claim 12, wherein the formation comprises a tar sands formation.

20. The method of claim 12, further comprising increasing the average temperature of the portion while producing the at least some mobilized, visbroken, or pyrolyzed fluids from the portion of the formation at the lower pressure.

21. A method for treating a tar sands formation, comprising:

providing heat to at least part of a hydrocarbon layer in the hydrocarbon containing formation from a plurality of heaters located in the formation;

allowing the heat to transfer from the heaters to at least a portion of the formation;

controlling a pressure in the portion of the formation such that the pressure remains below a fracture pressure of the formation overburden by producing at least some fluid from the formation;

assessing a hydrocarbon isomer shift of at least a portion of the fluid being produced to control the pressure;

reducing the pressure in the formation to a lower pressure when the assessed hydrocarbon isomer shift of the produced fluids reaches a selected value;

increasing a temperature of the portion of the formation to a temperature of at most about 350°

C. after reducing the pressure; and

producing, after the pressure is reduced to the lower pressure, at least some mobilized, visbroken, or pyrolyzed fluids from the portion of the formation at the lower pressure.

22. A method for treating a hydrocarbon containing formation, comprising:

providing heat to at least part of a hydrocarbon layer in the hydrocarbon containing formation from a plurality of heaters located in the formation;

allowing the heat to transfer from the heaters to at least a portion of the formation;

controlling a pressure in the portion of the formation such that the pressure remains below a fracture pressure of the formation overburden by producing at least some fluid from the formation;

assessing a weight percentage of saturates of fluids in the portion of the formation by assessing weight percentage of saturates properties in portions of the fluid being produced to control the pressure;

reducing the pressure in the formation to a lower pressure when the assessed weight percentage of saturates reaches a selected value;

increasing a temperature of the portion of the formation to a temperature of at most about 350°

C. after reducing the pressure; and

producing, after the pressure is reduced to the lower pressure, at least some mobilized, visbroken, or pyrolyzed fluids from the portion of the formation at the lower pressure.

23. A method for treating a hydrocarbon containing formation, comprising:

providing heat to at least part of a hydrocarbon layer in the hydrocarbon containing formation from a plurality of heaters located in the formation;

allowing the heat to transfer from the heaters to at least a portion of the formation;

controlling a pressure in the portion of the formation such that the pressure remains below a fracture pressure of the formation overburden by producing at least some fluid from the formation;

assessing a weight percentage of n-C₇ of fluids in the portion of the formation by assessing weight percentage of n-C₇ properties in portions of the fluid being produced to control the pressure;

reducing the pressure in the formation to a lower pressure when the assessed weight percentage of n-C₇ reaches a selected value;

increasing a temperature of the portion of the formation to a temperature of at most about 350°

C. after reducing the pressure; and

producing, after the pressure is reduced to the lower pressure, at least some mobilized, visbroken, or pyrolyzed fluids from the portion of the formation at the lower pressure.