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Title:
APPARATUS AND METHODS FOR PRODUCING NATURAL GAS USING A GAS RECYCLE PHASE TO REMOVE LIQUID FROM A WELL
Document Type and Number:
WIPO Patent Application WO/2013/010244
Kind Code:
A1
Abstract:
Apparatus and methods for producing natural gas from a well that include operating in a gas production phase wherein liquid can accumulate in a liquid accumulation zone as natural gas is being extracted from a gas production chamber, and operating in a gas recycle phase in which working gas is injected into a liquid accumulation chamber through a working gas injection tube to drive liquid from a liquid accumulation zone up out of the well. In some embodiments, natural gas can continue to be extracted from the gas production chamber during the gas recycle phase.

Inventors:
KOSLOW EVAN (CA)
Application Number:
CA2011/000830
Publication Date:
January 24, 2013
Filing Date:
July 19, 2011
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
KOSLOW EVAN (CA)
International Classes:
E21B43/40; E21B17/18; E21B34/06; E21B43/38; F04B47/04
Domestic Patent References:
WO2002035057A12002-05-02
WO2008153407A12008-12-18
Foreign References:
US5211242A1993-05-18
US3746089A1973-07-17
US20020023750A12002-02-28
GB2348909A2000-10-18
US20030183394A12003-10-02
Attorney, Agent or Firm:
BERESKIN & PARR LLP/SENCRL, SRL (40 King Street WestToronto, Ontario M5H 3Y2, CA)
Download PDF:
Claims:
Claims:

1. An apparatus for producing natural gas from a well having a casing and perforations in the casing, the apparatus comprising:

a sealing member positioned below the perforations and adapted to seal against the casing within the well so as to define a liquid accumulation chamber therebelow;

a working gas injection tube having a first opening within the liquid accumulation chamber;

a liquid lift tube having a second opening within the liquid accumulation chamber below the first opening, the first and second openings spaced apart by a liquid accumulation height to define a liquid accumulation zone within the liquid accumulation chamber;

a valve adapted to allow selective fluid communication between the liquid accumulation chamber and a gas production chamber defined between the working gas injection tube, the liquid lift tube and the casing so that liquid in the gas production chamber can flow through the valve and into the liquid accumulation chamber to fill the liquid accumulation zone; and

an assembly for selectively switching between a gas production phase wherein the valve is open and liquid can accumulate in the liquid accumulation zone as natural gas is extracted from the gas production chamber, and a gas recycle phase in which the valve is closed and working gas is injected into the liquid accumulation chamber through the working gas injection tube to drive liquid from the liquid accumulation zone up the liquid lift tube and out of the well.

2. The apparatus of claim 1 , wherein the sealing member is a packer that secures the working gas injection tube and liquid lift tube within the well.

3. The apparatus of claim 2, wherein the valve includes a check valve in the packer.

4. The apparatus of claim 3 wherein the check valve is adapted to close when the gas recycle phase begins.

5. The apparatus of claim 1 , wherein the assembly is adapted to permit the extraction of natural gas from the gas production chamber during the gas recycle phase.

6. The apparatus of claim 5, wherein after a gas recycle phase, the valve is adapted to open for draining upper liquid that accumulated in the gas production chamber into the liquid accumulation chamber.

7. The apparatus of claim 1 , wherein the assembly is adapted to initiate a supplemental gas production phase after the valve is closed and prior to the gas recycle phase beginning.

8. The apparatus of claim 7, wherein the assembly is adapted to initiate a subsequent gas recycle phase after the supplemental gas production phase.

9. The apparatus of claim 1 , further comprising a liquid gas separator for removing liquid from the natural gas.

10. The apparatus of claim 1 , further comprising a compressor for compressing the natural gas.

11. The apparatus of claim 10, wherein the compressor is operable to compress the natural gas to form the working gas at an elevated pressure selected for lifting the liquid from the well.

12. The apparatus of claim 1 , wherein the assembly is adapted to extract natural gas from the well during the gas recycle phase and use at least a portion of said extracted natural gas as the working gas.

13. The apparatus of claim 1 , wherein the working gas has an elevated pressure selected so that the working gas in the liquid accumulation chamber flows up the liquid lift tube with a velocity greater than a critical velocity to cause liquid entrainment in the working gas.

14. The apparatus of claim 1 , wherein during the gas recycle phase the working gas increases the pressure within the liquid accumulation chamber without increasing the pressure within the gas production chamber.

15. The apparatus of claim 1 , further comprising a controller for controlling the assembly to switch between the gas production phase and the recycle phase.

16. The apparatus of claim 1 , wherein the volume of the working gas injection tube is significantly less than the volume of the gas production chamber.

17. An apparatus for producing natural gas from a well having a casing and perforations in the casing, the apparatus comprising: a sealing member positioned above the perforations and adapted to seal against the casing within the well so as to define a liquid accumulation chamber therebelow;

a working gas injection tube having a first opening within the liquid accumulation chamber;

a liquid lift tube having a second opening within the liquid accumulation chamber below the first opening, the first and second openings spaced apart by a liquid accumulation height to define a liquid accumulation zone within the liquid accumulation chamber;

a valve adapted to allow selective fluid communication between the liquid accumulation chamber and a gas production chamber defined between the working gas injection tube, the liquid lift tube and the casing so that natural gas in the liquid accumulation chamber can flow through the valve into the gas production chamber; and

an assembly for selectively switching between a gas production phase wherein the valve is open and liquid can accumulate in the liquid accumulation zone as natural gas is extracted from the gas production chamber, and a gas recycle phase in which the valve is closed and working gas is injected into the liquid accumulation chamber through the working gas injection tube to drive liquid from the liquid accumulation zone up the liquid lift tube and out of the well.

18. The apparatus of claim 17, wherein the valve includes a swing valve in the working gas injection tube.

19. The apparatus of claim 18, wherein the swing valve is coupled to a float operable to automatically close the swing valve and inhibit fluid communication between the gas production chamber and liquid accumulation chamber when the liquid accumulation zone is full.

20. The apparatus of claim 17, wherein the working gas injection tube and liquid lift tube are concentric.

21. The apparatus of claim 20 wherein the liquid lift tube is provided within the working gas injection tube.

22. A method for producing natural gas from a well having a casing and perforations in the casing, the well including:

a sealing member positioned below the perforations and sealing against the casing so as to define a liquid accumulation chamber therebelow; a working gas injection tube having a first opening within the liquid accumulation chamber;

a liquid lift tube having a second opening within the liquid accumulation chamber below the first opening, the first and second openings spaced apart by a liquid accumulation height and defining a liquid accumulation zone within the liquid accumulation chamber;

a gas production chamber between the working gas injection tube, the liquid lift tube and the casing; and

a valve adapted to allow selective fluid communication between the liquid accumulation chamber and the gas production chamber so that liquid in the gas production chamber can flow through the valve and into the liquid accumulation chamber to fill the liquid accumulation zone;

wherein the method comprises: operating in a gas production phase wherein the valve is open and liquid can accumulate in the liquid accumulation zone as natural gas is being extracted from the gas production chamber; and

operating in a gas recycle phase in which the valve is closed and working gas is injected into the liquid accumulation chamber through the working gas injection tube to drive liquid from the liquid accumulation zone up the liquid lift tube and out of the well.

23. The method of claim 22, further comprising extracting natural gas from the gas production chamber during the gas recycle phase.

24. The method of claim 22, further comprising operating in the gas production phase until the liquid accumulation zone is substantially full.

25. The method of claim 24, further comprising switching to operate in the gas recycle phase after the liquid accumulation zone is substantially full.

26. The method of claim 22, further comprising operating in the gas recycle phase until the liquid accumulation zone is substantially clear of liquid.

27. The method of claim 26, further comprising switching to operate in the gas production phase after the liquid accumulation zone is substantially clear of liquid.

28. The method of claim 22, further comprising, after a gas production phase, operating in a supplemental gas production phase in which the valve is closed and upper liquid can accumulate within the gas production chamber.

29. The method of claim 28, further comprising, after the supplemental gas production phase, initiating a gas recycle phase, then draining the upper liquid into the liquid accumulation zone.

30. The method of claim 29, further comprising initiating a subsequent gas recycle phase after the upper liquid has been drained into the liquid accumulation zone

31. The method of claim 22, further comprising removing liquid from the extracted natural gas.

32. The method of claim 22, further comprising compressing the extracted natural gas.

33. The method of claim 32, wherein the natural gas is compressed to form the working gas at an elevated pressure selected for lifting the liquid from the well.

34. The method of claim 22, wherein the working gas has an elevated pressure selected so that the working gas in the liquid accumulation chamber flows up the liquid lift tube with a velocity greater than a critical velocity to cause liquid entrainment in the working gas.

35. The method of claim 22, wherein during the gas recycle phase the working gas increases the pressure within the liquid accumulation chamber without increasing the pressure within the gas production chamber.

36. A method for producing natural gas from a well having a casing and perforations in the casing, the well including:

a sealing member positioned above the perforations and sealing against the casing so as to define a liquid accumulation chamber therebelow; a working gas injection tube having a first opening within the liquid accumulation chamber;

a liquid lift tube having a second opening within the liquid accumulation chamber below the first opening, the first and second openings spaced apart by a liquid accumulation height and defining a liquid accumulation zone within the liquid accumulation chamber;

a gas production chamber between the working gas injection tube, the liquid lift tube and the casing; and

a valve adapted to allow selective fluid communication between the liquid accumulation chamber and the gas production chamber so that natural gas in the liquid accumulation chamber can flow through the valve into the gas production chamber;

wherein the method comprises:

operating in a gas production phase wherein the valve is open and liquid can accumulate in the liquid accumulation zone as natural gas is being extracted from the well; and

operating in a gas recycle phase in which the valve is closed and working gas is injected into the liquid accumulation chamber through the working gas injection tube to drive liquid from the liquid accumulation zone up the liquid lift tube and out of the well.

37. The method of claim 36, further comprising operating in the gas production phase until the liquid accumulation zone is substantially full.

38. The method of claim 37, further comprising switching to operate in the gas recycle phase after the liquid accumulation zone is substantially full.

39. The method of claim 36, further comprising operating in the gas recycle phase until the liquid accumulation zone is substantially clear of liquid.

40. The method of claim 39, further comprising switching to operate in the gas production phase after the liquid accumulation zone is substantially clear of liquid.

41. An apparatus for producing natural gas from a well having a casing and perforations in the casing, the apparatus comprising:

a sealing member adapted to seal against the casing within the well so as to define a liquid accumulation chamber therebelow;

a working gas injection tube having a first opening within the liquid accumulation chamber;

a liquid lift tube having a second opening within the liquid accumulation chamber below the first opening, the first and second openings spaced apart by a liquid accumulation height to define a liquid accumulation zone within the liquid accumulation chamber;

a valve adapted to allow selective fluid communication between the liquid accumulation chamber and a gas production chamber defined between the working gas injection tube, the liquid lift tube and the casing; and

an assembly for selectively switching between a gas production phase wherein the valve is open and liquid can accumulate in the liquid accumulation zone as natural gas is extracted from the gas production chamber, and a gas recycle phase in which the valve is closed and working gas is injected into the liquid accumulation chamber through the working gas injection tube to drive liquid from the liquid accumulation zone up the liquid lift tube and out of the well.

42. A method for producing natural gas from a well having a casing and perforations in the casing, the well including:

a sealing member sealing against the casing so as to define a liquid accumulation chamber therebelow;

a working gas injection tube having a first opening within the liquid accumulation chamber;

a liquid lift tube having a second opening within the liquid accumulation chamber below the first opening, the first and second openings spaced apart by a liquid accumulation height and defining a liquid accumulation zone within the liquid accumulation chamber;

a gas production chamber between the working gas injection tube, the liquid lift tube and the casing; and

a valve adapted to allow selective fluid communication between the liquid accumulation chamber and the gas production chamber;

wherein the method comprises:

operating in a gas production phase wherein the valve is open and liquid can accumulate in the liquid accumulation zone as natural gas is being extracted from the gas production chamber; and

operating in a gas recycle phase in which the valve is closed and working gas is injected into the liquid accumulation chamber through the working gas injection tube to drive liquid from the liquid accumulation zone up the liquid lift tube and out of the well.

Description:
Title: Apparatus and Methods for Producing Natural Gas Using a Gas Recycle Phase to Remove Liquid From a Well Technical Field

[0001] Embodiments disclosed herein relate to the production of natural gas, and in particular to apparatus and methods for producing natural gas using a gas recycle phase to remove liquid from a well. Introduction

[0002] Natural gas is commonly found in subterranean geological formations, such as deposits of granular material or porous rock (e.g. sandstone). The production of natural gas typically involves drilling a well into these geological formations, installing a casing into the well, and perforating the casing so that formation pressures force natural gas through the perforations and into the well. The natural gas may then be extracted, for example using tubing that is lowered into the well.

[0003] Along with the natural gas, formation liquids (e.g. water, oil and other hydrocarbons) are often present within the geological formations. As natural gas is extracted, the formation liquids will also tend to flow into the well. These formation liquids should be managed as they can negatively impact the production of natural gas.

[0004] In particular, when natural gas is flowing up a well, the formation liquids will tend to be entrained in the stream of natural gas, typically as small droplets or particles. Provided that the natural gas is flowing upwardly with a sufficient velocity (called the "critical velocity"), the liquid droplets will be lifted along with the gas to the top of the well, where the liquid and gas can be separated. As such, the velocity of the gas alone may provide for the removal of some liquid from a well, particularly with newer wells where the natural formation pressure and the corresponding gas velocities tend to be quite high.

[0005] However, as a well continues to operate, the formation pressure in the well and the resulting gas velocities tend to diminish. Eventually, the gas velocity will fall below the critical velocity and become too low to extract liquid particles. When this happens, the liquids will begin to accumulate in the well, forming a liquid column. This liquid column exerts a hydrostatic pressure that counteracts the formation pressure and inhibits gas from flowing through the perforations into the well. This tends to slow the overall production of natural gas.

[0006] Eventually, when sufficient liquid has accumulated, the hydrostatic pressure will reach equilibrium with the formation pressure in the well. When this occurs, gas production will cease as the formation pressure can no longer overcome the hydrostatic pressure exerted by the accumulated liquids. This causes the well to die unless the accumulated liquid can be removed.

Brief Description of the Drawings

[0007] The drawings included herewith are for illustrating various examples of one or more apparatus, systems, and methods of the present specification and are not intended to limit the scope of what is taught in any way. In the drawings:

[0008] Figure 1 is a schematic side view of an apparatus for producing natural gas with a gas recycle phase according to one embodiment;

[0009] Figure 2 is a schematic end view of the apparatus of Figure 1 ;

[0010] Figure 3 is a schematic side view of the apparatus of Figure 1 shown near the beginning of a gas production phase with the liquid accumulation zone substantially free of liquid;

[0011] Figure 4 is a schematic side view of the apparatus of Figure 1 shown during a gas production phase with the liquid accumulation zone partially filled with liquid;

[0012] Figure 5 is a schematic side view of the apparatus of Figure 1 shown with the liquid accumulation zone substantially filled with liquid; [0013] Figure 6 is a schematic side view of the apparatus of Figure 1 during a gas recycle phase with working gas being injected into a liquid accumulation chamber through a working gas injection tube to lift liquid from the well through a liquid lift tube;

[0014] Figure 7 is a schematic side view of the apparatus of Figure 1 shown during a gas recycle phase;

[0015] Figure 8 is a schematic side view of the apparatus of Figure 1 shown near the end of a gas recycle phase with the liquid accumulation zone substantially free of liquid;

[0016] Figure 9 is a schematic side view of the apparatus of Figure 1 after a gas recycle phase with upper liquid flowing from the gas production chamber through a check valve in the packer and into the liquid accumulation chamber;

[0017] Figure 10 is a schematic side view of an apparatus for producing natural gas according to another embodiment shown near the beginning of a gas production phase;

[0018] Figure 11 is a schematic end view of the apparatus of Figure 10;

[0019] Figure 2 is a schematic side view of the apparatus of Figure 10 shown near the end of a gas production phase;

[0020] Figure 13 is a schematic side view of the apparatus of Figure 10 shown during a gas recycle phase;

[0021] Figure 14 is a schematic side view of the apparatus of Figure 10 shown near the end of a gas recycle phase; and

[0022] Figure 15 is a flowchart of a method of producing natural gas according to another embodiment.

Description of Various Embodiments

[0023] As briefly described above, when the gas velocity in a natural gas well drops below a critical velocity, formation liquids will begin to accumulate in the bottom of the well. The hydrostatic pressure from these accumulating liquids will counteract the natural formation pressure in the well, slowing the flow of gas into the well and eventually preventing gas production when the hydrostatic pressure equals the formation pressure.

[0024] According to the teachings as generally described herein, at least some liquid may be removed from the well during a gas recycle phase. This tends to increase natural gas production and inhibit liquid accumulation within the well.

[0025] In particular, a well may be cycled between a "gas production phase" in which liquid accumulates in the well, and a "gas recycle phase" in which a working gas is pumped down into a liquid accumulation chamber to lift liquid out of the well.

[0026] In some embodiments, natural gas can be extracted from the well during both the gas production phase and the gas recycle phase. In other embodiments, natural gas can be extracted from the well during the gas production phase, but may not be extracted during the gas recycle phase.

[0027] Turning now to Figures 1 and 2, an apparatus 10 for producing natural gas from a well W according to one embodiment will now be described.

[0028] As shown, the well W has been drilled into the earth 12. The earth 12 includes a plurality of geological formations, including a first geological formation 14 relatively free of hydrocarbons (e.g. a non- hydrocarbon zone), and a second geological formation 16 relatively rich in natural gas (also referred to as a hydrocarbon zone). In some cases, the well W may be many hundreds or even thousands of feet deep.

[0029] Provided within the well W is a body 20 that includes a well casing 22. The well casing 22 is installed into the well W to secure the well W, for example to inhibit the walls of the well W from collapsing during the production of natural gas.

[0030] As shown, the well casing 22 includes one or more perforations 24. The perforations 24 are located within the second geological formation 16 and allow natural gas to flow through the perforations 24 and into the well W. As described briefly above, this flow of natural gas is generally driven by the natural formation pressures in the earth 12. As also described above, formation liquids present in the second geological formation 16 will also tend to flow through the perforations 24 and into the well W. These liquids will accumulate within the well W when the upwards velocity of the natural gas is below the critical velocity for the tubing or casing 22 that is used to bring the natural gas to the surface of the earth 12.

[0031] The apparatus 10 also includes a plurality of tubes located within the well W, including a working gas injection tube 28 (also called a recycle tube) and a liquid lift tube 30. As shown, the tubes 28, 30 may be concentric, for example with the liquid lift tube 30 provided coaxially within the working gas injection tube 28 (or vice versa). However, in other embodiments the tubes 28, 30 may have other arrangements. For example the tubes 28, 30 may be separate and spaced apart as shown in Figures 10 to 14.

[0032] The well casing 22 and tubes 28, 30 generally define a gas production chamber 26 therebetween (which may also be called an annulus). In particular, as shown the gas production chamber 26 may be defined as the annular region between the outermost of the concentric tubes (in this embodiment the working gas injection tube 28) and the walls of the casing 22. In other embodiments, the gas production chamber 26 may have other shapes (e.g. where tubes 28, 30 are not concentric, the gas production chamber 26 may have a non-annular shape).

[0033] As shown, the apparatus 10 also includes a sealing member (e.g. a packer 36, a downhole anchor, etc.) provided within the well W. The packer 36 or other sealing member seals against the sides of the casing 22 within the well W so as to define a reasonably fluid-tight region below the packer 36 called the liquid accumulation chamber 38. The packer 36 may also be coupled to and secure the working gas injection tube 28 and liquid lift tube 30 within the well W. [0034] In the embodiment illustrated in Figures 1 to 9, the packer 36 is positioned entirely below the perforations 24 in the casing 22. In other embodiments, the packer or other sealing member may be positioned entirely above the perforations (as described for example with reference to Figures 10 to 14 below). In yet other embodiments, the packer or other sealing member may be positioned intermediate the perforations (e.g. with some perforations above the packer and some perforations below the packer).

[0035] As shown, in some embodiments the packer 36 may be located near the bottom 20b of the well W, in some cases within the second geological formation 16. For example, in some embodiments the packer 36 may be located within a few hundred feet of the bottom 20b of the well W. In other embodiments, the packer 36 may be located within a few dozen feet of the bottom 20b of the well W.

[0036] As shown, at least one valve 37 (e.g. a one-way check valve) is provided in the packer 36. The valve 37 is generally configured to allow fluid communication between the gas production chamber 26 and the liquid accumulation chamber 38 when the liquid accumulation zone LAZ is being filled with liquid L, but inhibits fluid communication between the gas production chamber 26 and the liquid accumulation chamber 38 during the gas recycle phase when the liquid accumulation zone LAZ is being cleared of liquid L.

[0037] In particular, the check valve 37 is configured to open so that liquid in the gas production chamber 26 may flow through the packer 36 and into the liquid accumulation chamber 38. The check valve 37 is also configured to close and inhibit fluid flow when a liquid accumulation zone LAZ within the liquid accumulation chamber 38 is at least substantially full of liquid (as described below). This inhibits excess liquid from accumulating in the working gas injection tube 28 and liquid lift tube 30, which could otherwise result in a water-locked condition in which removing liquid from the well W may become very difficult.

[0038] In some embodiments, the check valve 37 may be coupled to a float (shown schematically as float 39) within the liquid accumulation chamber 38. The float 39 may be adapted to automatically closes the check valve 37 when the liquid accumulation zone LAZ is at least substantially full of liquid L.

[0039] In some embodiments, the check valve 37 may be adapted to allow fluid flow from the gas production chamber 26 into the liquid accumulation chamber 38 when the pressure in the liquid accumulation chamber 38 is low (e.g. below a particular threshold), but inhibit fluid flow when the pressure in the liquid accumulation chamber 38 is high (e.g. above a particular threshold, such as when working gas is being pumped into the liquid accumulation chamber 38).

[0040] As shown in Figure 1 , the working gas injection tube 28 has a first opening 28b, and the liquid lift tube 30 has a second opening 30b, both located within the liquid accumulation chamber 38. The openings 28b, 30b are spaced apart by a liquid accumulation height H, with the second opening 30b of the liquid lift tube 30 located below the first opening 28b of the working gas injection tube 28. The liquid accumulation height H and casing 22 cooperate to define a liquid accumulation zone LAZ within the liquid accumulation chamber 38. Generally the liquid accumulation zone LAZ defines a fixed volume of liquid that may be extracted from the well W during a gas recycle phase.

[0041] Specifically, the well casing 22 may have a casing radius R C as shown in Figure 2. The volume VLAZ of the liquid accumulation zone LAZ may then generally be determined according to equation 1 :

V LAZ = TTHR c 2 (1)

[0042] In some embodiments, at least one of the tubes 28, 30 may be adapted to remain generally free of liquid L as the liquid accumulation zone LAZ fills with liquid L. For example, in some cases the liquid lift tube 30 may be sealed during gas production as the liquid accumulation zone LAZ is filled (e.g. by closing a lift valve 48). In such cases, the volume VLAZ of the liquid accumulation zone LAZ may generally be determined according to equation 2: LAZ V C asing Vtubing

= TTHRC 2 - TTHR T 2

where R T is the radius of the liquid lift tube 30.

[0043] As shown, the liquid lift tube 30 has a lower portion 30c that extends beyond a bottom surface 36b of the packer 36. In this embodiment, the length of the lower portion 30c helps provide the liquid accumulation height H.

[0044] The apparatus 10 also generally includes an assembly 11 adapted for selectively switching between a gas production phase and a gas recycle phase as will be described in greater detail below. As shown, the assembly 11 is normally located at or near the top of the well W.

[0045] The assembly 1 1 may include a plurality of fluid lines 29, 31 , and 32 and valves 48, 50 and 52 that are configured for extracting natural gas and liquid from the well W and for selectively injecting working gas into the well W. For example, a fluid line 32 and a collection valve 50 may fluidly couple the gas production chamber 26 to a liquid-gas separator 40 of the assembly 11. Similarly, fluid lines 29, 31 and a recycle valve 52 and lift valve 48 may fluidly couple the working gas injection tube 28 and the liquid lift tube 30 (respectively), to the liquid-gas separator 40.

[0046] The liquid-gas separator 40 is adapted to separate liquids (e.g. the formation liquids) from the natural gas extracted from the well W so that dry natural gas can be produced. This dry natural gas can then be stored, sold, used as a working gas for lifting liquid from the well W, turned into liquid natural gas (LNG) through cooling, and so on.

[0047] As shown, a compressor 42 may be used to draw the fluids (e.g. liquids and gas) from the well W and into the assembly 11.

[0048] In some embodiments, the gas production chamber 26 may be at relatively low pressures during gas extraction (e.g. between about 20 and 30 psi, or at higher or lower pressures depending on the operating characteristics of the well W). Accordingly, the compressor 42 may be used to decrease the pressure in the gas production chamber 26 as well as increase the pressure of the extracted natural gas to desired "sales line" levels.

[0049] In particular, in some embodiments, the compressor 42 may be also used to increase the pressure of the natural gas to form a working gas at a desired pressure (e.g. 100 psi, 250 psi, or more) for lifting the liquid from the well W.

[0050] As shown, the assembly 11 also includes a control valve 44. As will be described further below, the control valve 44 is adapted to selectively inject working gas into the well W, for example via a fluid line 46 that is in fluid communication with the working gas injection tube 28.

[0051] In some embodiments, the assembly 11 may include a controller for switching between a gas production phase and a gas recycle phase. For example, the assembly 11 may include a controller 45 configured to operate one or more of the control valve 44, the lift valve 48, the collection valve 50, and the recycle valve 52. In some embodiments, the electronic controller 45 may also control other elements of the assembly 11 , such as the compressor 42.

[0052] It should be noted that in the embodiment illustrated in Figures 1 to 9, gas production from the second geological formation 16 can actually continue during a liquid lift operation (e.g. during a gas recycle phase) and that such gas may only be temporarily diverted back down into the well W to effect liquid lift. In particular, after a liquid lift the diverted gas can then subsequently be released from the well W to the sales line. Hence, switching from a gas production phase to a gas recycle phase only refers to a partial (or complete) but temporary diversion of natural gas for lift operations, and does not imply a diminished rate of gas production or capture from the second geological formation 16 during the liquid lift. As such, the illustrated embodiment actually allows gas production during liquid lift with no significant loss of net gas production. [0053] In some embodiments, the controller 45 may be in communication with one of more sensors, for example a down-hole sensor within the well W, pressure sensors, and flow sensors in one or more fluid lines 29, 31 , 32, 46, the gas production chamber 26, and so on. The sensors may help the controller 45 determine when to switch between a gas production phase and a gas recycle phase, for example by monitoring the pressures within the well W, fluid lines 29, 31 , 32, 46, the gas production chamber 26, and so on.

[0054] Operation of the apparatus 10 will now be described with specific reference to Figures 3 to 9.

[0055] In particular, Figure 3 shows the apparatus 10 near the beginning of a gas production phase. As shown, natural gas (indicated generally by NG) is flowing from the second geological formation 16 through the perforations 24 and into the gas production chamber 26 in the well W. The natural gas NG then flows upwardly where it may be collected through the fluid line 32 when the collection valve 50 is open.

[0056] As this happens, formation liquids (indicated generally by L) are also flowing through the perforations 24 and into the well W. When the upward velocity of the natural gas NG is below the critical velocity, these liquids L will tend to collect in the bottom of the gas production chamber 26 on the upper surface 36a of the packer 36 (indicated generally as upper liquid U). At this stage of operation, the check valve 37 is generally open (e.g. the float 39 may open the check valve) so that these upper liquids U can flow through the packer 36 and down into the liquid accumulation chamber 38.

[0057] As shown, although some liquid L has accumulated within the liquid accumulation chamber 38, the liquid accumulation zone LAZ is at least partially free of liquid L. In particular, the free surface S of the liquid L in the liquid accumulation chamber 38 is at or near the opening 30b of the liquid lift tube 30. [0058] In some embodiments, during a gas production phase natural gas NG will also be extracted from one (or both) of the working gas injection tube 28 and liquid lift tube 30, for example by opening the recycle valve 52 and lift valve 48 and drawing suction on fluid lines 29, 31 using the compressor 42. This may allow natural gas NG to be collected at high production rates, since the entire cross-sectional area of the well W is being used to collect natural gas NG with minimal frictional losses.

[0059] Turning now to Figure 4, as the gas production phase continues, liquid L continues to flow through the perforations 24 and accumulate within the gas production chamber 26 as upper liquid U. The check valve 37 remains open (although the float 39 may have been moved closer to the closed position by the rising surface S of the liquid L), which allows the upper liquid U to continue flowing down into the liquid accumulation chamber 38 where the liquid accumulation zone LAZ is filling with liquid. In particular, as shown the surface S of the liquid L in the liquid accumulation chamber 38 is now within the liquid accumulation zone LAZ generally between the first and second openings 28b, 30b of the working gas injection tube 28 and the liquid lift tube 30.

[0060] In some embodiments, as shown the lower portion 30c of the lift tube 30 may begin to fill with liquid L as the liquid accumulation zone LAZ is filled, for example, when the lift valve 48 is open and natural gas NG is being extracted from the lift tube 30. In other embodiments, the lift tube 30 may be sealed (e.g. by closing the lift valve 48) so as to inhibit liquid L from flowing into the lift tube 30 as the liquid accumulation zone LAZ fills.

[0061] Turning now to Figure 5, the gas production phase has continued until now the liquid accumulation zone LAZ is substantially full of liquid L. In particular, as shown the surface S of the liquid L in the liquid accumulation chamber 38 is at or near the opening 28b of the working gas injection tube 28. [0062] In some embodiments, once the liquid accumulation zone LAZ is substantially full of liquid L, the gas production phase may be terminated and a gas recycle phase may begin.

[0063] However, in other embodiments, the gas production phase may continue (e.g. in a supplemental gas production phase) even after the liquid accumulation zone LAZ is substantially full of liquid L. In particular, as shown in Figure 5, once the liquid accumulation zone LAZ is substantially full of liquid L, the check valve 37 will close (e.g. by operation of the float 39) so that no further liquid (e.g. upper liquid U) can flow from the gas production chamber 26 into the liquid accumulation chamber 38. Since the check valve 37 is closed, the height of the liquid L within the liquid accumulation chamber 38, the working gas injection tube 28 and liquid lift tube 30 will be fixed and will not increase during subsequent gas production.

[0064] As the supplemental gas production phase then continues, upper liquid U will continue to accumulate within the gas production chamber 26. This supplemental gas production phase may continue so long as the production rate of natural gas NG from the gas production chamber 26 is at desired levels. In particular, the supplemental gas production phase may continue until the height of the upper liquid U above the packer 36 creates a sufficient hydrostatic pressure so as to interfere with gas production. For example, as shown in Figure 5, the upper surface U s of the upper liquid U has reached the perforations 24 in the casing 22, which may begin to slow the rate of natural gas production. Once the rate of natural gas production falls below a desired threshold, a gas recycle phase can be initiated.

[0065] For greater clarity, it will be appreciated that in some embodiments a gas recycle phase may be initiated before the liquid accumulation zone LAZ is entirely full. In particular, in some embodiments a gas recycle phase may be initiated at a point when the liquid accumulation zone LAZ is only partially full, or even contains only a minimal quantity of liquid. [0066] Figure 6 generally shows a gas recycle phase during which the apparatus 10 lifts liquid L from the well W by injecting a working gas therein (indicated generally as WG). However, as described above natural gas production may continue during the gas recycle phase. For instance, natural gas NG within the gas production chamber 26 may still be extracted via the fluid line 32. In particular, such natural gas NG may be used to provide the working gas WG down into the well W.

[0067] To initiate a gas recycle phase, the controller 45 may activate the control valve 44 to direct working gas WG into the fluid line 46. The working gas WG will then flow down through the working gas injection tube 28 and into the liquid accumulation chamber 38. The controller 45 may also close the recycle valve 52 to inhibit the working gas WG from flowing directly out of the working gas injection tube 28 and into the liquid-gas separator 40.

[0068] During the gas recycle phase, the check valve 37 remains closed so that the working gas WG is inhibited from flowing through the packer 36 and into the gas production chamber 26. The working gas WG therefore increases the pressure within the liquid accumulation chamber 38 generally without increasing the pressure within the gas production chamber 26.

[0069] The increased pressure in the liquid accumulation chamber 38 begins to drive the liquid L up the liquid lift tube 30 as shown in Figure 6. This reduces the volume of liquid L within the liquid accumulation zone LAZ. In particular, the surface S of the liquid L in the liquid accumulation chamber 38 in Figure 6 is between the first and second openings 28b, 30b of the working gas injection tube 28 and the liquid lift tube 30

[0070] Generally the working gas WG may be dry natural gas coming from the liquid-gas separator 40 and pressurized to an elevated pressure using the compressor 42. In some embodiments, the pressure of the working gas WG may be selected based on factors such as the depth of the well W, the radial size of the liquid lift tube 30 (e.g. R T ), and other factors such as frictional and two-phase flow resistance losses within the tubes 28, 30, and so on. In some embodiments the working gas WG may be provided at a pressure of more than 100 psi. In some embodiments the working gas WG may be provided at a pressure between 200 psi and 600 psi, or at even higher pressures.

[0071] In some embodiments, the control valve 44 may direct substantially all of the natural gas NG being produced during a gas recycle phase back down the well W as working gas WG. However, in some embodiments, less than all of the natural gas NG being produced may be required to produce a desired quantity of for working gas WG. In such cases, the control valve 44 may be configured to use some natural gas NG as working gas WG while the remaining natural gas NG is extracted as dry natural gas (e.g. for storage or sale).

[0072] As shown in Figure 7, as the gas recycle phase continues to operate and working gas WG is pumped down into the liquid accumulation chamber 38, more liquid L will be lifted up the liquid lift tube 30, lowering the surface S of the liquid L until the liquid accumulation zone LAZ is substantially clear of liquid.

[0073] At some point the working gas WG will begin to enter the lift tube 28 (e.g. as shown in Figure 8). When this happens, the working gas WG will begin to flow upwards and back to the liquid-gas separator 40. If the pressure of the working gas WG was selected to be sufficiently high, the working gas WG flowing up the liquid lift tube 30 will have a gas velocity that is greater than the critical velocity. Therefore, the working gas WG flowing up the liquid lift tube 30 will have plugs or particles of liquid L entrained therein and will draw these liquid L particles up the liquid lift tube 30 to the top of the well W and into the liquid-gas separator 40. This process can continue until the liquid lift tube 30 and liquid accumulation zone LAZ have been substantially cleared of liquid L.

[0074] Once the liquid lift tube 30 and liquid accumulation zone LAZ have been substantially cleared of liquid L, the gas recycle phase can be terminated. In particular, the control valve 44 can close to stop the supply of working gas WG to the liquid accumulation chamber 38. The recycle valve 52 can also be opened to allow any remaining working gas WG in the working gas injection tube 28 to be extracted using the fluid line 29. Moreover, any remaining working gas WG in the liquid lift tube 30 can also be extracted via the fluid line 31.

[0075] In some embodiments, once the gas recycle phase is terminated, a gas production phase can be initiated immediately. For example, the apparatus 10 can in some embodiments repeatedly cycle between gas production phases where the liquid accumulation zone LAZ fills with liquid and gas recycle phases where the liquid accumulation zone LAZ is cleared using working gas WG.

[0076] However, in some embodiments, once a gas recycle phase is terminated, upper liquid U may still remain in the gas production chamber 26 (for example, due to a supplemental gas production phase or as a result of liquid accumulation during the gas recycle phase). Accordingly, the check valve 37 can then be opened after a gas recycle phase. In some cases, the check valve 37 may automatically open when pressures within the liquid accumulation chamber 38 drop below a particular threshold (e.g. are roughly equal with the pressure in the gas production chamber 26). The open check valve 37 then allows any remaining upper liquid U to drain into the liquid accumulation chamber 38, as shown in Figure 9.

[0077] If a sufficient quantity of upper liquid U was present in the gas production chamber 26, the liquid accumulation zone LAZ may quickly become filled once again. In some such embodiments, once the liquid accumulation zone LAZ has been filled, another gas recycle phase can be initiated. This can allow more of the upper liquid U to be removed from the gas production chamber 26.

[0078] In particular, in some instances, it may be advantageous to repeatedly run multiple gas recycle phases in sequence to lower the level of the upper liquid U to a desired level, particularly after a long supplemental gas production phase where a significant quantity of upper liquid U may have accumulated.

[0079] Generally, the use of the apparatus 10 may provide one or more benefits over previous natural gas production systems. In particular, as discussed above, in some instances the production of natural gas NG may be continued during one or more gas recycle phases in which liquid L is removed from the well. For example, even when a gas recycle phase is taking place, the low pressure within the gas production chamber 26 encourages continued and enhanced rates of gas in-flow into the well W through the perforations 24. This gas can be subsequently or simultaneously released to sales during or after a gas recycle phase used to reduce the quantities of accumulated liquids within the well W.

[0080] Furthermore, the volume of the working gas injection tube 28 is less than the volume of the gas production chamber 26, in some cases quite significantly lower. Accordingly, by using the working gas injection tube 28, a relatively smaller volume of working gas WG can be used to pressurize the liquid accumulation chamber 38 to effect liquid lift while sustaining a low pressure within the gas production chamber 26 (e.g. the annular region around the tubes 28, 30).

[0081] In particular, in some embodiments, the volume of the working gas injection tube 28 or the size of the liquid accumulation chamber 38 (or both) should be kept small so as to reduce the volume of working gas WG required to pressurize the liquid accumulation chamber 38 and lift the liquid L.

[0082] Moreover, as discussed above, the volume VLAZ of the liquid accumulation zone LAZ is fixed, which can prevent liquid lock from occurring and which might make it very difficult or even impossible to lift liquid L from the well W. Generally, the size of the liquid accumulation zone LAZ can be determined by selecting a suitable liquid accumulation height H depending on factors such as the radius R c of the casing 22, the depth of the well W, the pressure of the working gas WG that can be provided by the compressor 42, the size of the liquid lift tube 30 (e.g. R T ), frictional and other losses, and so on.

[0083] In some embodiments, the liquid accumulation height H may be between about ten and twenty feet for a well W having a casing radius Rc of about 5 inches and a well depth of about 10,000 feet. In other embodiments, the liquid accumulation height H may be greater than twenty feet. In yet other embodiments, the liquid accumulation height H may be less than ten feet.

[0084] In some embodiments, the liquid accumulation zone LAZ may have a volume VLAZ of about twenty gallons or more, and a typical gas recycle phase may be capable of lifting that volume VLAZ from a well W in only a few minutes.

[0085] Turning now to Figure 10, illustrated therein is a schematic of an apparatus 110 for producing natural gas according to another embodiment. As shown, the apparatus 110 is adapted for use with a well W provided in the earth 12. The apparatus 110 is generally similar to apparatus 10, and where suitable, like elements have been given similar numbers incremented by 100.

[0086] Provided within the well W is a body 120 that generally includes a well casing 122. The well casing 122 includes one or more perforations 124 provided adjacent the second geological formation 16.

[0087] Also located within the casing 122 are tubes that extend down into the well W, including a liquid lift tube 130 and a working gas injection tube 128 (also called a recycle tube). In this embodiment and in contrast with the apparatus 10 described above, tubes 128, 130 are not concentric, but rather as shown in Figure 10 as separate, independent tubes. However, in other embodiments the tubes 128, 130 could be concentric.

[0088] It should be noted for clarity that Figure 10 is a schematic and is not necessarily drawn to scale. In particular, in some embodiments the casing 122 may have a diameter D between about 4.5 inches to 7 inches, while each tube 128, 130 may have a diameter between about 1.75 inches to 3.0 inches for example. [0089] The well casing 122 and tubes 128, 130 generally define a gas production chamber 126 therebetween, which in this embodiment may have a non-annular shape (although for convenience the gas production chamber 126 may still be referred to as the annulus).

[0090] The apparatus 110 also includes a packer 136 or other sealing member which seals against the sides of the casing 122 to define a liquid accumulation chamber 138 therebelow. In contrast with the apparatus 10 as described above, in this embodiment the packer 136 is located above the perforations 124. As such, the perforations 124 are located within the liquid accumulation chamber 138. This alternative layout and relative location of the packer 136 is possible when the perforated interval of the casing 122 is of modest height and where fluid accumulation in the perforated interval will not cause undue restriction of gas flow.

[0091] Similar to as described above, the working gas injection tube 128 has a first opening 128b located within the liquid accumulation chamber 138, and the liquid lift tube 130 also has a second opening 130b also located within the liquid accumulation chamber 138. The second opening 130b is below the first opening 128b of the working gas injection tube 128, and the openings 128b, 130b are spaced apart by a liquid accumulation height H (which may be at least partially defined by a lower portion 130c of the liquid lift tube 130).

[0092] As discussed above, in this embodiment, the perforations 124 are within the liquid accumulation chamber 138. Accordingly, natural gas NG flowing through the perforations will tend to accumulate in the liquid accumulation chamber 38. To allow this natural gas NG to be extracted from the well W, selective fluid communication between the gas production chamber 126 and the liquid accumulation chamber 138 should be provided.

[0093] For example, the working gas injection tube 128 may include a valve 134 (e.g. a swing valve), which as shown may be located above the packer 136. The valve 134 is generally movable between an open position when operating the well W in a gas production phase (as shown in Figures 10 and 12 which allows the liquid accumulation zone LAZ to be filed with liquid L), and a closed position when operating the well W in a recycle phase (as shown in Figures 13 and 14 which allows the liquid accumulation zone LAZ to be cleared of liquid L).

[0094] In particular, in the open position, the valve 134 permits fluid communication between the liquid accumulation chamber 138 and the gas production chamber 126, allowing natural gas NG coming through the perforations 124 to flow into the opening 128b of the working gas injection tube 128, through a lower portion 128c thereof and into the gas production chamber 126.

[0095] However, when in the closed position, the valve 134 inhibits fluid communication between the liquid accumulation chamber 138 and the gas production chamber 126. In particular, when in the closed position, the valve 134 closes the flow of natural gas NG into the gas production chamber 26, but allows working gas WG to be injected down the working gas injection tube 128 into the liquid accumulation chamber 138.

[0096] The operation of the apparatus 10 will now be described with particular reference to Figures 10 and 12 to 14.

[0097] As generally described above, when the natural formation pressure in the well W is greater than the hydrostatic pressure due to liquid L in the well W, natural gas NG and liquid L will tend to flow through the perforations 124 and into the well W. With the apparatus 1 10 located in the well W, the liquid L will tend to collect in the bottom of the well W, while the natural gas NG tends to flow upwardly and (with the valve 134 in the open position) into the gas production chamber 126.

[0098] As shown in Figure 10, near the beginning of a gas production phase, the free surface S of the liquid L in the well W may be at or near the opening 130b of the liquid lift tube, and the liquid accumulation zone LAZ is substantially free of liquid L. However, as the gas production phase continues, the surface S of the liquid L will rise as liquid L accumulates and fills the liquid accumulation zone LAZ. For example, as shown in Figure 12 the surface S of the liquid L is at or near the opening 128b of working gas injection tube 128.

[0099] Turning now to Figures 13 and 14, when the liquid L substantially fills the liquid accumulation zone LAZ, the apparatus 0 can switched to a gas recycle phase to remove liquid L. As described above, some production of natural gas to the sales line may continue during the gas recycle phase.

[00100] In particular, in the gas recycle phase, the valve 134 is closed or closes in response to working gas WG being injected down through the working gas injection tube 28 and into the liquid accumulation chamber 38.

[00101] In some embodiments, sending the working gas WG down the working gas injection tube 128 can automatically move the valve 134 from the open position to the closed position. In other embodiments, the valve 134 may move into the closed position in response to electrical or mechanical actuation (e.g. using a float or other sensor that is triggered when the surface S of the liquid L reaches a particular height).

[00102] In some embodiments, the movement of the valve 134 into the closed position may be used as a signal to the controller 45 to initiate a recycle phase. In some other embodiments, the pressure of the natural gas NG from the gas production chamber 126 may be monitored (e.g. using one or more sensors) so the controller 45 can determine when to initiate a recycle phase.

[00103] Similar to as described above with respect to apparatus 10, the working gas WG increases the pressure in the liquid accumulation chamber 138, which tends to drive the liquid L up the liquid lift tube 130, clearing the liquid accumulation zone LAZ. Moreover, at some point the working gas WG will enter the lift tube 128 where it will begin to flow upwards with a gas velocity greater than the critical velocity, and will therefore lift the liquid L in the liquid lift tube 130 upwards to the top of the well W and into the liquid-gas separator 40. [00104] Generally, the pressure increase required to lift the liquid L may depend on the depth of the well W, friction losses within the liquid lift tube 130, and other factors. In some embodiments, for example with a well W approximately 6000 feet deep, a working gas WG pressure of 150 psi may be sufficient to lift the liquid L to the top of the well W. In deeper wells, higher working gas WG pressures (e.g. 250 to 300 psi, or more) may be used to lift the liquid L out of the well W.

[00105] Once the liquid lift is complete and the liquid accumulation zone LAZ has been sufficiently cleared of liquid L, the recycle phase may be stopped by ending the flow of working gas WG into the liquid accumulation chamber 138.

[00106] Another gas production phase can then be initiated. For instance, the valve 134 can be opened, allowing natural gas NG in the liquid accumulation chamber 138 to once again flow into the gas production chamber 26.

[00107] In some embodiments, the valve 134 can be biased to return to the open position (e.g. using a spring or other biasing mechanism) when the working gas WG pressure in the working gas injection tube 128 falls below a certain threshold pressure. As such, the valve 134 may be configured to detect when the supply of working gas WG has ended and automatically reopen.

[00108] In some embodiments, negative pressure (e.g. suction) may be applied to the working gas injection tube 128 (e.g. using the compressor 42) to help move the valve 134 from the closed position to the open position.

[00109] In some embodiments, the valve 134 may be coupled to a float (which may be similar to float 39 for example) and configured such that, depending on the height of the surface S of the liquid L, the valve 134 can be automatically moved between the open position and the closed position.

[00110] By cycling between gas production and recycling phases, the amount of liquid L within the well W can be controlled. This can be useful to increase the rate of natural gas NG production by reducing the hydrostatic pressure in the well W. This can also avoid killing the well W, which can significantly extend the well's W life span.

[00111] Turning now to Figure 15, illustrated therein is a flowchart of a method 200 for producing natural gas according to another embodiment.

[00112] At step 202, a gas production phase is initiated in a natural gas well. This may include opening one or more suitable valves (e.g. using a controller or automatically opening the valves) to allow fluid communication between a liquid accumulation chamber and a gas production chamber in the well.

[00113] At step 204, natural gas is extracted from the well. This may include opening a collection valve and collecting natural gas from the gas production chamber. In some embodiments, the gas production chamber could be the outer annular region in a well (e.g. the region between the tubing and the casing), and extracting the natural gas may include using a compressor to apply suction to the well.

[00114] In some cases, natural gas may also be collected from a liquid lift tube and a working gas injection tube.

[00115] In some embodiments, the extracted natural gas may be passed through a liquid gas separator to remove liquids from the gas (thus forming a "dry" natural gas).

[00116] As described above, as natural gas is extracted, formation liquids will tend to collect in a liquid accumulation zone within the liquid accumulation chamber. At step 206, a determination is made as to whether a liquid accumulation zone is full. In some embodiments this may include the liquid accumulation zone being substantially full or at least partially full of liquid. In particular, in some embodiments a gas recycle phase may be initiated before the liquid accumulation zone is entirely full.

[00117] If the liquid accumulation zone is not full, then the method 200 can continue at step 204 and natural gas can continue to be extracted from the well. However, if the liquid accumulation zone is full, the method 200 can then proceed to step 208.

[00118] At step 208, a valve is closed to inhibit fluid communication between the liquid accumulation chamber and the gas production. In some embodiments, this may occur automatically.

[00119] Optionally, at step 209, in some embodiments supplemental gas production may continue after the liquid accumulation zone is full (for example using the apparatus 10 as described above).

[00120] At step 210, a recycle phase is initiated. This may include adjusting certain valves to control the movement of working gas for example. In some embodiments, natural gas may continue to be extracted from the well during the recycle phase (and in some embodiments at least some of that natural gas may be used as working gas).

[00121] At step 212, working gas is injected down into the well using a working gas injection tube. The working gas is used to drive liquid in the well up the liquid lift tube and clear the liquid accumulation zone.

[00122] At step 214, a determination is made as to whether the liquid accumulation zone is substantially clear of liquid. If the liquid accumulation zone is not clear, then the method 200 can return to step 212 and more working gas can be pumped into the well. However, if the liquid accumulation zone is substantially clear of liquid, the method 214 may then proceed to step 216.

[00123] At step 216, the supply of working gas to the well is stopped. In some embodiments, the method 200 then returns to step 202, where another gas production phase is initiated. In other embodiments, one or more subsequent gas recycle phases may be initiated (for example after a supplemental gas production phase, a check valve in a packer may be opened to allow accumulated upper liquid to drain and fill the liquid accumulation zone with liquid). [00124] The teachings described herein may provide for one or more benefits. For example, cycling between a gas production phase and a recycle phase as described may allow liquid to be selectively removed from the well, reducing the hydrostatic pressure and increasing the natural gas production of a well. Moreover this can be accomplished without pressurizing the entire gas production chamber, thus decreasing the energy consumed to lift the liquid and allowing continued in-flow of natural gas into the well while liquid is being lifted from the well.

[00125] Moreover, the apparatus and methods as described herein may be used to selectively lift a fixed volume of liquid from the well and thus can avoid liquid lock problems that may occur in other natural gas production systems.

[00126] In general, the teachings herein can be described as allowing for annular compression (e.g. extraction of natural gas from the annular chamber within a casing at reduced pressure and compressing this low-pressure gas to a higher sales line pressure) without requiring annular re-compression (e.g. the entire annular region or gas production chamber need not be pressurized) to lift liquid.

[00127] In particular, a working gas can be provided directly to the liquid accumulation chamber of the well using a working gas injection tube with a volume smaller than the volume of the gas production chamber to force the liquid out of the liquid accumulation zone. Accordingly, it may take significantly less energy (e.g. in some cases up to 50% less energy) to lift the liquid out of the well.

[00128] While the above description provides examples of one or more apparatus, systems, and methods, it will be appreciated that other apparatus, systems, and methods may be within the scope of the present description as interpreted by one of skill in the art.