Title:
DUAL STRING AUTOMATIC GAS LIFT VALVE
United States Patent 3851997


Abstract:
An automatically operated, pressure responsive gas lift injection valve for use in a dual zone string utilizes a pressure operated switching valve for delivering injection gas to the tubing string having the highest column of fluid. The switching valve is responsive to the tubing pressure in each of the two production strings and, sensing the higher of the two tubing pressures, opens that string to lift gas injected through the casing annulus.



Inventors:
DOUGLAS B
Application Number:
05/447130
Publication Date:
12/03/1974
Filing Date:
03/01/1974
Assignee:
DRESSER IND INC,US
Primary Class:
Other Classes:
137/119.09, 417/116, 417/117
International Classes:
E21B43/12; E21B43/14; F04F1/18; (IPC1-7): F04F1/18; G05D11/00
Field of Search:
137/119 417
View Patent Images:
US Patent References:
3348503Bakery apparatus1967-10-24Sidles
2179226Well flowing valve1939-11-07Bryan



Primary Examiner:
Husar C. J.
Assistant Examiner:
Gluck, Richard E.
Attorney, Agent or Firm:
Caddell, Michael J.
Claims:
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows

1. A dual string, gas lift injection valve assembly comprising:

2. The gas lift injection valve assembly of claim 1 wherein said body means further comprises dual lower chambers separated by a centrally located wall portion and dual upper chambers communicating with said lower chambers and with said passage means.

3. The gas lift injection valve assembly of claim 2 wherein said passage means further comprises a generally centrally located upper passage extending from said pressurized gas delivery means into said body means; two branch passages extending from said upper passage each to one of said dual upper chambers; secondary passages extending from said dual upper chambers to said dual lower chambers; and, port means between said lower chambers and the conduit strings.

4. The gas lift injection valve assembly of claim 1 wherein said pressure responsive valve means further comprises a dual-element valve member sealingly and slidably mounted in said body means and having pressure responsive areas thereon; and, dual valve seats in said passage means arranged to receive in sealing engagement said valve member, each said valve seat circumscribing said passage means between said body means and the conduit strings.

5. The gas lift injection valve assembly of claim 1 wherein said means for delivering pressurized gas comprises a bellows-type, differential pressure operated valve assembly having ports therein communicating with the annulus of the wellbore and further having a valved flow passage between said ports and said passage means.

6. The gas lift injection valve assembly of claim 1 further comprising two tubular elongated conduit adapters attached one to each side of said valve assembly and arranged to align co-axially with the dual string production tubing in a dual-zone well; each of said conduit adapters having connection means at each end for connection to standard sections of oil well production tubing.

7. A dual string gas lift valve assembly for use in a wellbore, said assembly comprising:

8. The gas lift valve assembly of claim 7 further comprising checkvalve means in said passage means arranged to allow flow into the conduit strings, but prevent flow from the conduit strings.

9. The gas valve assembly of claim 8 further comprising elongated tubular conduit adapters attached to said valve assembly and arranged to be coaxially aligned with the conduit strings and further having connection means at each end for connection to standard tubing sections.

10. The gas lift valve assembly of claim 9 further comprising pressure responsive injection gas regulating means connected to said gas lift valve assembly and having fluid communication passages from the annulus of the well to said valve assembly, with pressure responsive valve means in said fluid communication passages in valving relationship therewith.

11. The gas lift valve assembly of claim 10 wherein said body member further comprises a generally solid body having dual upper chambers containing said checkvalve means and dual lower chambers divided by a generally centrally located wall section; with said valve means in said body member comprising an elongated valve body slidably and sealingly mounted in said wall section; with said gas passage means communicating from said regulating means through said dual upper chambers and said dual lower chambers to dual ports in the wall of said body at said lower chambers, with one said port in each lower chamber, said each port being coaxially aligned with said elongated valve body and arranged to be alternatively closed and opened by said valve body.

12. A dual string gas injection assembly for use in gas-lift oil wells having dual production strings, said assembly comprising:

13. A pressurized gas injection assembly for use in gas-lift operation in a dual string well; said assembly comprising:

14. The gas injection assembly of claim 13 wherein said connecting means further comprises elongated tubular sections securedly attached to said body member and coaxially aligned with the production strings in the wellbore; said tubular sections having connection means at each end for connection with standard tubing sections.

15. The gas injection assembly of claim 14 wherein said gas injection valve comprises a tubular cylindrical housing having a central bore passage, port means through the wall thereof, an expandable bellows element securedly attached therein to define an expansion-contraction chamber, and a valve member on said bellows element arranged to open and close said central bore passage.

Description:
BACKGROUND OF THE INVENTION

In a dual zone completion well wherein the formation pressure is insufficient to force formation fluids to the top of the wellbore from either of the producing formations and the well is particularly suitable for gas lift operations, the method of producing such a well normally involves utilizing dual string production equipment with gas lift valving apparatus in each production string.

When both injection valves are supplied with gas through the casing annulus, a problem arises in controlling the gas lift operation since both valves may tend to open at the same time. Since the fluid levels in the two tubing strings are seldom at the same height, one string may be receiving too much gas and the other may be receiving too little gas. Alternatively, when such simultaneous opening occurs it is possible that neither string will receive sufficient gas to provide the gas lifting operation desired. This results in highly inefficient production and greatly increases the cost of the fluids recovered. This is due to the fact that a certain amount of gas is required to bring the well fluids to the surface and when the strings are opened to the annulus at the same time, they tend to "rob" each other and neither ends up with sufficient gas to lift the fluid column.

The present invention solves this problem by providing an alternating intermittent gas lift valve that is responsive to fluid pressure in the two strings to allow injection gas to go only into the production string having the highest column of fluid and therefore in greatest need for injection gas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a dual production string in a well having multiple producing formations.

FIG. 2 illustrates a cross-sectional schematic view of the apparatus of this invention.

FIG. 3 represents a top cross-sectional view looking down on the apparatus from section line 3--3 in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 a dual production string 10 is located in the borehole 11 and communicates with two producing formations, the upper formation 12 and a lower formation 13. The dual production tubing string 10 has a primary conduit 14 communicating with the upper formation 12 via opening 15 in the bottom end of the tubing, and a secondary string 16 communicating with the lower producing formation 13.

A packer 17 is located in the annulus between the production string 10 and the borehole 11 above the producing formation 12 to seal off the annulus above the packer from that below it. A second packer 18 is located in the annulus below the upper formation to isolate the formations from each other.

The automatic, intermittent gas lift valve 20 is located in the dual producing string 10 between the primary and secondary conduits 14 and 16, above packer 17.

A closer view of the gas lift valve is shown in the cross-sectional view of FIG. 2 in which the valve is shown as comprising two tubular adapter conduits 21 and 22 placed in parallel configuration and arranged to align coaxially with the dual production strings 14 and 16 respectively. The tubular adapters 21 and 22 may be threadedly joined to the production conduit or may be joined by use of connector collars 23 as shown in the figure.

The gas lift valve apparatus utilizes a substantially solid body portion 24 in which has been formed dual primary valving chambers 25a and 25b, dual backflow checkvalve chambers 26a and 26b, gas lift flow passages 27 and 28a and 28b, and gas injection ports 29a and 29b.

Gas lift passage 27 is substantially centrally located in the upper portion of body portion 24 and passes downward generally parallel with conduits 21 and 22 whereupon it intersects dual gas flow passages 28a and 28b which branch generally outward and then turn downward. Passages 28a and 28b pass downward generally parallel to conduits 21 and 22 and flow into backflow checkvalve chambers 26a and 26b.

Spring loaded checkvalves 30 and 31 are located movably up and down in chambers 26a and 26b respectively and are continuously urged upward into sealing engagement with the bore openings of passages 28a and 28b by coil springs 32 and 33 respectively.

The lower portion of chambers 26a and 26b communicate with the primary valving chambers 25a and 25b via central openings 34b and 34a located therebetween. Primary chambers 25a and 25b are separated by an inwardly projecting wall 35 having an opening located substantially in the center thereof. A sliding valve member 37 is located slidably in the opening in wall 35 and a sleeve seal 36 is located in the wall opening abutting valve member 37 in sealing engagement to prevent fluid or gas communication between the primary valving chambers.

The opening in wall 35 is arranged so that it is substantially aligned with opposing ports 29a and 29b in body 24 so that valve member 37 can move laterally from closing one port to closing the opposite port. As illustrated in the figure, valve member 37 is in the position of opening port 29a and closing port 29b.

Ports 29a and 29b correspond with matching ports through the wall of conduits 21 and 22, respectively, thereby forming channels of communication from the inner bores of the conduits to the primary valve chambers.

Injection gas is supplied to the main flow passage 27 via a standard gas injection valve 38 having a tubular threaded connection adapter 39 which engages the upper portion of body 24 and communicates with passage 27. Valve mechanism 38 has a generally tubular body 40 and a gas bellows element 41 located concentrically therein. Bellows element 41 has a lower bellows head 42 to which is attached a valve member 43 arranged to be movable into and out of sealing engagement with the flow passage 39a of threaded adapter 39. Body 40 forms an injection chamber 44 which receives gas from the well annulus through ports 45 in the wall of body 40. Body 40 also forms a gas chamber 46 which contains an inert compressed gas which gas also fills the inner portion of bellows 41. An interconnecting cap 47 is sealingly attached to the top of body member 40 enclosing gas chamber 46 and is securedly attached by means such as welding at each end to conduits 21 and 22. Likewise, body 24 is similarly attached to conduits 21 and 22 at each side.

FIG. 3 illustrates a top view of the gas lift valve assembly as it is located substantially centralized in the wellbore casing 48. Gas passage down the annulus 49 easily flows around the apparatus and has access to ports 45 in the upper lift valve 38.

In typical operation, referring to FIGS. 1 and 2, pressurized injection gas is pumped into the well annulus through means such as piping 50. The gas enters the upper gas valve 38 through ports 45, thereby compressing bellows 41, moving valve element 43 upward out of bore 39a and allowing gas to flow down passages 27, 28a and 28b.

Meanwhile, prior to the opening of element 43, formation fluid has accumulated in the conduits 21 and 22 and the fluid in the conduit having the highest level (conduit 21 in the case illustrated) applies the greatest hydrostatic pressure force on the slidable valve member 37 through ports 29a or 29b thereby moving the member into blocking position over the opposite port. This allows the pressurized injected gas to move the spring loaded checkvalve 30 or 31 downward and moves the gas past the valve 37 and through whichever port is opened. The next pulse of pressurized gas may move out through the opposite port depending upon the rate of build-up of the two different fluid levels in the conduits and also depending upon the time required for the injection gas in the annulus to build-up sufficient pressure again to open the upper gas injection valve 38.

As an alternative, a pressure cycling device containing a timer may be used at the surface to apply intermittent pressure applications to the annulus gas should the rate of fluid build-up in the conduits be too slow to efficiently utilize a constant annulus gas pressure.

A distinct advantage of this apparatus is that it automatically injects gas into the column of fluid having the greatest need for the gas, i.e. the highest column, regardless of which column received the preceding gas charge. This provides the highest possible gas lifting efficiency, particularly when one of the formations is considerably higher flowing formation than the other.

Although a specific preferred embodiment of the present invention has been described in the detailed description above, the description is not intended to limit the invention to the particular forms or embodiments disclosed therein, since they are to be recognized as illustrative rather than restrictive and it will be obvious to these skilled in the art that the invention is not so limited. For example, the valving member is illustrated as elongated and may be cylindrical, polygonal or other configuration in cross-sectional shape. Also other type checkvalves than those shown could be utilized. The invention is declared to cover all changes and modifications of the specific example of the invention herein disclosed for purposes of illustration which do not constitute departures from the spirit and scope of the invention.