Gas Lift Valve And System

Abstract

This patent discloses a system for gas lift of petroleum wells in which when the well is shut-in, the formation liquid will not rise above a selected level in the tubing. The patent also discloses a gas lift valve in which the bellows is protected against an excess pressure differential thereacross.

Parent Case Text

This application is a division of application Ser. No. 822,911, filed May 8, 1969, which is a continuation-in-part of my copending application Ser. No. 819,608, filed Apr. 28, 1969, entitled "Intermitter," both abandoned.

Description

This invention relates to a gas lift valve system and valves to be used therein.

When a well is shut-in for any reason, formation liquid will rise in the tubing to a level depending upon formation pressure. In gas lift systems, the liquid may rise to a level at which it is necessary to unload the well before normal gas lifting can commence. Desirably, the system is such that liquid is prevented from rising to a level requiring unloading.

Gas lift valves commonly employ pressure responsive members to control their operation such as bellows. If these bellows are subjected to a high differential thereacross in either direction, their characteristics are changed and they will not operate at the pressures at which they are set before they are run in the well. Desirably, the bellows are completely protected against a differential in either direction.

An object of this invention is to provide a gas lift system in which when gas lift operations are interrupted for any reason, the formation is shut-in and excess liquid is not permitted to rise in the tubing.

Another object is to provide a gas lift system in which liquid is prevented from rising in the tubing above a selected point.

Another object is to provide a pilot-operated valve for a gas lift system in which the bellows is protected against high dome pressure without the use of a lost motion connection between the bellows and valve member.

Another object is to provide a valve for gas lift system in which the bellows is protected against both dome pressure and external pressure without providing a lost motion connection between the bellows and valve member.

Other objects, features and advantages of the invention will be apparent from the drawings, the specification and the claims.

In the drawings wherein an illustrative embodiment of the invention is shown and wherein like numeral indicate like parts,

FIG. 1 is a view partially in elevation and partially in cross section of a well employing the gas lift system and valve of this invention; and,

FIGS. 2A, 2B and 2C are continuation views partially in vertical cross section and partially in quarter section, illustrating the system and valve of this invention.

Referring first to FIG. 1, a well is illustrated having a casing 10 and a tubing 11 therein with the casing tubing annulus closed just above the formation 12 by a packer 13. The valve assembly of this invention is shown in place in the tubing at 14.

Referring now to FIGS. 2A through 2C, a special mandrel is attached to tubing 11. The mandrel includes the nipple 15 at its upper end to which is connected the bypass section 16. Below the bypass section 16 a tube 17 is connected and another nipple 18 is provided below the tube 17. The tubing 11 may continue below the special mandrel or the packer (FIG. 1) may be secured directly to the lower end of the special mandrel.

The bypass section 16 is provided with a shoulder 19 (FIG. 2A) at its upper end which is engageable with the latch mechanism indicated generally at 21 on the wire line portion of the assembly to hold the wire line portion of the assembly in place in the mandrel. The wire line portion of the assembly is prevented from moving downwardly by shoulder 22 in the lower nipple 18.

At the lower end of the bypass member 16 a port 23 is provided for passing gas from the casing tubing annulus into the tubing. A plurality of bypass passageways 24 bypass the port 23 to conduct the liquids from the well formation up past the inlet port 23.

The wire line portion of the system comprises the latch 21, the gas lift valve indicated generally at 25 and the liquid control valve indicated generally at 26.

The latch for latching the valve assembly in the mandrel may take any desired form. As the latch 21 forms no part of this invention, its operation will not be explained.

THe two valves 25 and 26 are substantially identical in construction and operation.

Referring first to valve 26, a valve seat 27 and valve member 28 control flow of fluid through the valve. The valve 28 includes a resilient packing 29 which slidably seals with the seat surface 31 to provide a bubble-tight seal. A metal-to-metal seat is also provided between the upper extremity of the seat 27 and a surface 28a on the valve member.

Operation of the valve is controlled by a PRESSURE responsive member such as the piston 32. The piston 32 is carried on the stem 33 of the valve member, and O-rings 34 and 35 seal between the wall of cylinder 36 and the piston 32 and between the piston and valve stem 33, respectively.

To provide for admitting upstream pressure to the chamber provided by cylinder 36, the valve stem 33 has a bore 33a extending therethrough. To keep the bore clear of contamination, a stinger 37 extends completely through the bore. The annulus between the stem and probe provides a bleed passageway to admit upstream pressure into the chamber 36. It will be noted that the piston 32 is much larger in diameter than the seat 31, and thus when the pressures are equal above and below the valve member, it will be seated by this pressure differential. Also the spring 37 urges the valve toward seated position to positively close the valve in the event other forces on the valve member are equal.

Pressure fluid is maintained in chamber 36 and vented therefrom by a valve member 38 which slidably cooperates with a seat 39. Suitable O-rings 41 and 42 provide a sliding seal between the valve member 38 and seat 39. A vent passageway 43 establishes communication between the cylinder 36 and an outlet port 44 in seat 39. The valve member is ported at 45, and thus when the O-ring 41 is in the position shown in the lower figure, the cylinder 36 is vented and the fluid from the formation rising in the tubing will force the valve 28 from its seat and permit fluid to bypass this valve. When the O-rings 41 and 42 straddle the port 44, the pressure is trapped in the cylinder 32, and the equal upstream pressures across the valve and piston acting on the larger piston area will hold the valve member seated.

The slide valve 38 is shifted by a fluid motor which includes the bellows 46 and the pressure dome 47. Within the dome a valve member 48 is provided just above the bellows. The valve member cooperates with an upwardly looking seat 49 when the slide valve 38 is in its lower position and with a downwardly looking seat 51 when the slide valve is in its upper position.

As will appear below, the seating of valve 48 protects the bellows against an excess differential thereacross.

The free end of bellows 46 is secured to the valve 38. A valve stem 52 which controls seating of the ball 48 extends through bellows 46.

In operation the dome 47 will be charged to a pressure at which the lower valve will close only upon the liquid level rising in the tubing to a level higher than present during normal gas lift operations. Thus, when gas lifting is interrupted for any reason and formation pressure continues to force fluid into the tubing, this valve will close upon such liquid reaching a selected level in the tubing to prevent further entry of liquid into the tubing.

Upon the force of tubing pressure exceeding the force exerted by the dome pressure, the bellows begins to collapse to raise the slide valve 38. After the port 44 has been straddled by the O-rings 41 and 42 to effect closing of the valve member 28, continued upward movement of the valve will force the ball valve 48 within the dome on to its upper seat 51. As the bellows is entirely filled with an incompressible liquid, seating of the ball will prevent further travel of the bellows, and the pressure within the bellows will be substantially equal to the pressure outside of the bellows regardless of how high the external pressure might get. Thus, the bellows is completely protected against high external pressure.

When the gas lift operations are resumed to lift the excess fluid out of the tubing, the pressure on the bellows 46 will reduce, and it will begin to extend, and the ball 48 will, of course, be unseated. It will be held off of its seat 49 by stem 52 until after the valve member 38 has moved downwardly to a point where the port 44 is uncovered. At this time the valve 48 will be free of the stem 52 and will be permitted to seat on the lower seat 49. This will protect the bellows from dome pressure. Thereafter, if pressure in the tubing reduces even further, the slide valve is free to move downwardly so that the pressure on the liquid will be relieved by slightly increasing the area to substantially equalize pressure internally and externally of the bellows, thus protecting it against dome pressure when substantially lower pressures are present in the tubing. It will be appreciated that by using the simple slide valve illustrated, the need for a lost motion connection between the valve stem and valve such as in my U.S. Pat. No. 3,318,322 is eliminated as the slide valve performs its function as a valve and also permits movement of the valve after the slide valve has reached its lower position to vent the port 44 and relieve pressure within the bellows.

The upper valve 25 is identical to the lower valve, except that the piston 53 is integral with the metal seat portion of the valve member and the position of the vent port 54. The vent port 54 is positioned so that when the pressure conditions are reduced on the bellows and the bellows is extended, the vent port is closed to pressurize the cylinder 36 and close the upper valve member. Thus, gas is not permitted to flow through the valve until sufficient liquid has accumulated in the tubing to exert a pressure on the bellows of the upper valve member which will raise the slide valve 38 to uncover vent port 54 and thus open the upper valve member.

In operation the twin valve assembly is run and positioned in the well so that packers 55 and 56 straddle the inlet port 23 to force gas to flow through the upper valve member. Also, the lower packet 57 forces fluid rising from the well to flow through the lower valve 26. As the fluid from the well rises, it will pass the lower valve 26 which is normally in open position, flow through the bypass passageways 24 and rise in the annulus between the mandrel and the upper valve into the tubing thereabove. As soon as a selected level has been reached, the pressure exerted by the column of fluid is effective on the bellows of the upper valve to raise the slide valve 38 and uncovered port 54. This vents the upper surface of piston 53 and the upper valve will open. Gas from the tubing casing annulus will enter through port 53 past the back-check valve indicated generally at 58 and rise through bore 59 to the upper valve member. This valve being open the gas will pass through port 61 into the annulus between the upper valve and the tubing and lift the liquid in the tubing. As soon as the pressure in the tubing has reduced due to lifting of the slug of liquid thereabove, the bellows of the upper valve will extend to move valve 38 into a position to straddle port 54 to trap pressure in cylinder 36. As the gas pressure across the piston equalizes, the gas will effect closing of the main valve member of the upper valve 25. The valve will remain closed until sufficient liquid flows into the tubing from the formation to again cause operation of the upper valve 25.

In the event that gas lift operations are interrupted and liquid from the formation continues to rise in the tubing until it reaches a level at which the force exerted by the column of fluid will overcome the force exerted by the charge in the pressure dome 47 of the lower valve 26, then the bellows of the lower valve will collapse and the valve member 38 will move up to position the O-rings 41 and 42 to straddle the vent 44, thus trapping the formation liquid in the cylinder 36, which will effect closing of the lower valve.

The upper valve will, of course, be open, but as gas is not being injected into the casing tubing annulus, lifting will not occur. As soon as pressures have equalized between the tubing and casing, the check valve 58 will prevent backflow of any of the liquid in the tubing into the casing. When gas is again injected into the casing tubing annulus, it will flow through the open upper valve 25 to lift the fluid in the tubing. As soon as the column of fluid is lifted, the pressure conditions present at the lower valve 26 will reduce, and the lower valve will again open for normal operation.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made within the scope of the appended claims without departing from the spirit of the invention.

Claims

What is claimed is:

1. A pilot operated gas lift valve comprising,

a main valve,

a pressure responsive member opening and closing said main valve,

means for maintaining or venting pressure fluid from upstream of said main valve on a surface of said pressure responsive member for controlling movement thereof including a two-position slide valve for opening and closing a port,

a fluid motor for operating the slide valve including a pressure dome and a bellows filled with liquid,

a valve seat and valve member controlling communication between said dome and bellows,

a stem within the bellows preventing seating of said valve member until said bellows has extended to a selected position in which said slide valve is in one of its two positions,

said slide valve being free to move in response to additional extension of said bellows after said valve member has seated to reduce the pressure differential across the bellows.

2. The valve of claim 1 wherein a second valve seat is provided for cooperation with said valve member and said stem moves the valve member into engagement with the second valve seat to trap liquid in the bellows when the bellows is in collapsed position to protect the bellows against excess pressure.

3. A pilot-operated gas lift valve comprising,

a main valve member and seat controlling flow of gas,

a piston connected to the main valve member,

said piston reciprocal in a cylinder,

a bleed passageway through the main valve member and piston to conduct fluid to said cylinder,

a passageway for venting said cylinder,

a two-position slide valve controlling said passageway,

a fluid motor for operating the slide valve including a pressure dome and a bellows filled with liquid,

a valve seat and valve member in the dome controlling communication between said dome and bellows,

a stem within the bellows preventing seating of the valve member in the dome until said bellows has extended to a selected position in which said slide valve closes said vent passageway,

said slide valve being free to move in response to additional extension of said bellows after said valve member has closed said vent passageway to reduce the pressure differential across the bellows.

4. The valve of claim 3 wherein a second valve seat is provided in the dome for cooperation with the valve member therein and said stem moves the valve member into engagement with the second seat to trap liquid in the bellows when the bellows is in collapsed position to protect the bellows against excess pressure.