Acid gas disposal method

• US 20030047309A1
• Filed: 09/04/2002
• Published: 03/13/2003
• Est. Priority Date: 09/07/2001
• Status: Active Grant

• Current Assignee: Exxonmobil Upstream Research Company (Exxon Mobil Corporation)
• Original Assignee: Exxonmobil Upstream Research Company (Exxon Mobil Corporation)
• Inventors: Northrop, P. Scott, Thomas, Eugene R., Hu, Hua
• Granted Patent: US 7,128,150 B2
• Time in Patent Office: Days
• US Class Current: 166/265
• CPC Class Codes: E21B 41/0064 Carbon dioxide sequestration storing fluids in porous layers B65G5/005
• CPC Class Codes: E21B 43/162 Injecting fluid from longitudinally spaced locations in injection well
• CPC Class Codes: E21B 43/164 Injecting CO2 or carbonated water in combination with organic material C09K8/594
• CPC Class Codes: E21B 43/166 Injecting a gaseous medium; Injecting a gaseous medium and a liquid medium CO2 injection E21B43/164; steam injection E21B43/24
• CPC Class Codes: E21B 43/30 Specific pattern of wells, e.g. optimising the spacing of wells
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y02P 90/70 Combining sequestration of CO2 and exploitation of hydrocarbons by injecting CO2 or carbonated water in oil wells

Abstract

This invention is method of recovering gas from a gas-bearing subterranean formation in which gas is produced from an upper portion of the formation and a waste gas is injected into a lower portion of the formation to dispose of the waste gas. The waste gas is injected within a 3000 foot (914 m) radial distance from the production of the gas. The injection and production can be carried out using one well or a plurality of wells.

Claims

1. A method of recovering gas from a gas-bearing subterranean formation comprising:

a) producing gas from an upper portion of the formation; and

b) injecting a waste gas into a lower portion of the formation to dispose of the waste gas, said waste gas being injected within a 3000 foot (914 m) radial distance from the production of the gas.

2. The method of claim 1 where the production of gas is through one or more production wells and the injection of waste gas is through one or more spaced-apart injection wells.

3. The method of claim 2 wherein each production well is in fluid communication with the upper portion of the formation, and each injection well is in fluid communication with the lower portion of the formation and a substantial portion of the waste gas injected through a selected injection well is stored outside the drainage volume of the production well closest to the selected injection well.

4. The method of claim 2 wherein at least one of the one or more injection wells is a deviated well.

5. The method of claim 1 wherein the steps of producing gas and the injection of waste gas are carried out within one or more wells.

6. The method of claim 1 wherein the produced gas is produced through a production zone of a well and the injection of waste gas is through an injection zone of the well, and the horizontal distance between the top of the injection zone and the bottom of the production zone being at least distance D in which

D=h tan θ

where;

θ

=Arc cos[(0.64h^⅔

/A^⅓

R^⅓

(k_v/k_h)^⅔

(I/W)^⅓

]

h is the vertical distance from the bottom of the production zone to the top of the injection zone;

R is a recovery factor for the well drainage volume;

A is the drainage area of the well;

k_v/k_h is the ratio of vertical permeability to horizontal permeability of the formation; and

I/W is the ratio of waste gas injection rate to produced gas production rate.

7. The method of claim 2 in which one or more production wells are placed in the upper portion of the formation, and one or more injection wells are placed in the lower portion of the formation, with the horizontal displacement between the injection through any one of the injection wells and the production through any one of the production wells being at least a distance D in which

D=h tan θ

where;

θ

=Arc cos[(0.64h^⅔

/R^⅓

A^⅓

(k_v/k_h)^⅔

(I/W)^⅓

]

h is the vertical distance from the bottom of the producing zone of the producing well to the top of the injection zone of the injection well;

R is a recovery factor for the well drainage volume;

A is the drainage area of the production well;

k_v/k_h is the ratio of vertical permeability to horizontal permeability of the formation; and

I/W is the ratio of waste gas injection rate to produced gas production rate.

8. The method of claim 1 wherein the produced gas is natural gas.

9. The method of claim 8 wherein the natural gas comprises an acid gas.

10. The method of claim 9 wherein the acid gas is at least one of carbon dioxide and hydrogen sulfide.

11. The method of claim 9 further comprises removing at least part of the acid gas from the natural gas and using the removed acid gas as the source of waste gas for injection into the subterranean formation.

12. The method of claim 9 wherein the acid gas is injected into the formation simultaneously with production of the natural gas from the formation.

13. The method of claim 1 in which the relative permeability of the waste gas is reduced in the region of the formation above injection of the waste gas into the formation by injecting a fluid agent into the formation immediately above the injection of waste gas into the formation.

14. The method of claim 13 wherein the fluid agent is water.

15. The method of claim 13 wherein the fluid agent is foam.

16. The method of claim 1 wherein the viscosity ratio of the injected waste gas to the produced gas (μ

_inj/μ

^disp) is greater than 1.05.

17. The method of claim 1 wherein the density ratio of the injected waste gas to the produced gas (ρ

_inj/ρ

_disp) is greater than 1.05.

29. The method of claim 16 in which the relative permeability of the acid gas is reduced in the region of the formation above injection of the acid gas into the formation by injecting a fluid agent into the formation immediately above the injection of acid gas into the formation.

30. The method of claim 29 in which the fluid agent is water.

31. The method of claim 29 in which the fluid agent is foam.

18. A method of recovering hydrocarbons from a subterranean formation, comprising:

a) producing the hydrocarbons from the upper portion of the formation, the hydrocarbons comprising an acid gas;

b) separating the acid gas from the hydrocarbons; and

c) placing at least a portion of the separated acid gas into the lower portion of the formation.

19. The method of claim 18 wherein the separation of acid gas is performed in a well into which the hydrocarbon is produced.

20. The method of claim 18 wherein the separation of acid gas is performed after the hydrocarbon is passed to the earth'"'"'s surface.

21. The method of claim 18 wherein the acid gas and hydrocarbons are produced into a well, the acid gas is separated from the hydrocarbons in the well, and the separated acid gas is placed into the lower portion of the formation from the same well.

22. The method of claim 19 wherein the well is deviated.

23. The method of claim 22 in which the deviated well contains production perforations through which the hydrocarbons are produced and injection perforations through which acid gas is placed into the lower portion of the formation, and the horizontal distance between the top of the injection perforations and the bottom of the production perforations being less than 3000 feet (914 m).

24. The method of claim 23 wherein the horizontal distance between the top of the injection perforations and the bottom of the production perforations is less than 2000 feet (610 m).

25. The method of claim 23 further comprising injecting into the formation between the top of the acid gas injection perforations and the lower end of the production perforations a permeability reducing agent to reduce the relative permeability of the acid gas in the region between the acid gas injection perforations and hydrocarbon production perforations.

26. The method of claim 25 in the permeability-reducing agent is water.

27. The method of claim 25 in the permeability-reducing agent is foam.

28. The method of claim 18 wherein the hydrocarbons are produced into a first well and the acid gas is placed into the lower portion of the formation from a second well.

32. The method of claim 18 wherein the hydrocarbons are produced from the formation for a desired period of time prior to commencement of acid gas placement into the formation.

33. The method of claim 18 in which the formation is anticlinal and the production of hydrocarbons is from a plurality of production wells positioned generally in the interior portion of the formation and the placement of acid gas into the formation is from a plurality of injection well that are placed generally at the peripheral region of the formation.

34. The method of claim 18 in which the formation is monoclinal and production of hydrocarbons is from a plurality of production wells that are placed in the updip portion of the monocline formation, and placement of acid gas is through a plurality of injection wells placed in the downstructure portion of the formation in a line-drive configuration.

35. The method of claim 18 in which the formation is already partially depleted by existing production wells, and in which some of said existing wells are converted to injection wells.