US3410217A

US3410217A - Liquid control for gas wells

Info

Publication number: US3410217A
Application number: US633437A
Authority: US
Inventors: Kelley Kork; Robert K Kelley
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-04-25
Filing date: 1967-04-25
Publication date: 1968-11-12
Anticipated expiration: 1985-11-12

Description

NOV. 12, 1968 KELLEY ET AL LIQUID CONTROL FOR GAS WELLS Filed April 25, 1967 2 Sheets-Sheet 1 INVENTORS K05? Kfllf Rig/P7 K (11157 5 a W ATTUK/VVS Nov. 12, 1968 KELLEY ETAL LIQUID CONTROL FOR GAS WELLS 2 Sheets-Sheet 2 Filed April 25, 1967 FIE| E- INVENTORS KOKK mm BY 20152787 /(f A y ATTOFA/EYS United States Patent LIQUID CONTROL FOR GAS WELLS Kork Kelley, 518 W. 7th St., and Robert K. Kelley, 619 N. Pershing St., both of Liberal, Kans. 67901 Confinuation-in-part of application Ser. No. 451,187, Apr. 27, 1965, now Patent No. 3,324,803, dated June 13, 1967. This application Apr. 25, 1967, Ser. No. 633,437

17 Claims. (Cl. 103-52) ABSTRACT OF THE DISCLOSURE A liquid removal system for gas wells, having a liquidgas separator at the bottom of the tubing string to admit only liquid to the string, a gas lift valve in the tubing string to expel the fluid from the string in slugs, using the gas in the casing as propellant, and a free piston member in the tubing string which assists in sweeping out the liquid slug. A catcher device is provided at the wellhead to assist in removing the free piston member for removal and inspection by optionally retaining the free piston member at the well head.

Cross-reference to related applications This application is a continuation-in-part of our copending application, Ser. No. 451,187, filed Apr. 27, 1965, and entitled Liquid Control for Gas Wells, now issued as Patent No. 3,324,803.

Background of the invention This invention relates to improvements in a Liquid Control for Gas Wells and more particularly to devices for limiting and removing accumulations of liquids which would otherwise interfere with gas production.

Liquids such as Water and/ or oil, etc. tend to accumulate in many producing gas wells. It is necessary to remove these liquids, particularly the water, because the filling up of the bore hole restricts the flow of the gas. If not removed, the water level will rise or build up in the bore hole and in time will kill the well or stop the flow of gas competely.

Various methods are presently being utilized to remove accumulations of water from gas wells. In some instances, it is pumped out by the conventional rod-type pump driven by a pumping unit at the surface. In other wells, a small tubing string is installed from the surface down into the Well bore, and the gas pressure in the well is used to flow the water out through the tubing string. The flow provided in this manner can be either constant or intermittent. However, constant flow is extremely wasteful because, once the Water is exhausted from the well, the gas under pressure contained therein is vented directly to the atmosphere.

Know systems for providing intermittent flow through the tubing string are controlled either manually or by cycle timer devices. Manual control is costly because it requires almost constant attendance at each well in order to open the valve in the tubing string when a certain quantity of water accumulates and to close the valve as soon as the accumulation of water is exhausted from the well. Cycle timers are inefficient, costly, and require fairly constant attendance. If the valve in the tubing string is left open for too short a period, not all of the water will be exhausted from the well during each cycle and a water buildup will occur. If the valve is left open for too long a period, all of the water will be exhausted and very considerable quantities of gas will be allowed to escape. These timing difficulties may be partly overcome by use of a piston lift with a sensing device for sensing arrival of 3,410,217 Patented Nov. 12, 1968 the piston at the surface, but such systems are costly and somewhat unreliable.

In quite deep or comparatively low pressure wells, the stored energy contained in the compressed gas in not sufiicient to lift the column of liquid contained in the tubing string and the described modes of operation are impossible. In such cases, devices known as gas lifts have been employed to inject gas from the well bore into the tubing string in such manner as to lift relatively short columns or slugs of liquid through the tubing string to the surface. However, the foregoing comments relating to manual and cycle timer intermittent flow control apply equally to these gas lift devices.

Summary of the invention The present invention contemplates an apparatus for automatically controlling the removing of the accumulation of liquids from gas and oil wells by lifting slugs of liquid through the tubing string only so long as liquid is available at the entrance thereto. This is accomplished by mounting a liquid-gas separator at the lower end of the tubing string in such manner as to coact with a gas lift device or devices to expel the liquid from the Well. The tubing string is open to the well bore only when liquid is available, and the gas lift device is responsive to the static head of the liquid rising in the tubing string to inject the compressed gas from the well bore into the tubing string beneath a column or slug of liquid of the desired height. The gas lift device shuts off the flow of gas from the well bore to the tubing string in response to a pressure drop therein which occurs as soon as the liquid slug is discharged at the surface. Thus the present invention provides the desired fully automatic intermitten flowing of the water out of the well without depend ing on an arbitrary time cycle but rather in response to the actual physical conditions of the well for maximum efficiency.

A member is used in the tubing string to enhance the efficiency by preventing the propelling gas from breaking up the liquid-gas interface at the bottom of the liquid slug. This member functions by isolating the propelling gas from the major portion of the bottom surface of the liquid slug, preventing the gas from bubbling and channeling through to form a low-gradient gas-liquid mixture requiring more gas for explusion. The member may take the form of a free piston element. The need for a surface controller is eliminated, as the bottom-hole liquid-gas separator admits only liquid to the string and the gas lift valves close off the flow when the slug is expelled.

Accordingly, it is a principal object of the present invention to provide an apparatus for automatically controlling the removing of the accumulation of liquids from wells providing a substantial gas pressure in the well bore.

A further object of the invention is to provide an apparatus of the character described which will function automatically and in an efiicient manner to avoid wastage and loss of gas and pressure from the Well.

A still further object of the present invention is to provide apparatus for intermittently ejecting accumulations of liquid from a well bore through a tubing string and which functions automatically in response to a predetermined static head within the tubing string.

Yet another object of the present invention is to provide an apparatus of the character described which incorporates a positive action liquid-gas separator functioning automatically to permit entry of liquid from the Well bore into the tubing string and to close off communication between the tubing string and the well bore when the liquid supply is exhausted.

Still another object of the present invention is to provide a liquid control of the character described having a free piston member for improving the action of the lift which requires neither lubricating apparatus nor sensing apparatus at the well-head for automatic operation.

Yet another object of the present invention is to provide a free piston member of the character described which is adaptable to use with tubingof rough and uneven interior surface without requiring reaming of the tubing string.

A still further object of the present invention is to provide a free piston member of the character described which is of relatively light overall density to reduce the impact of the member at the top and bottom of the tubing string.

Another object of the present invention is to provide a liquid control of the character described having simple and reliable catcher apparatus for optionally catching and retaining the free piston member at the well head.

Another object of the present invention is to provide an apparatus of the character described which is inexpensive, compact, sturdy, foolproof, and maintenance-free so as to provide a long operating life at the bottom of a well.

Further objects and advantages of the invention will be apparent as the specification progresses, and the new and useful features of the LIQUID CONTROL FOR GAS WELLS will be fully defined in the claims attached hereto.

Brief description of the drawings The preferred form of the invention is shown in the accompanying drawing forming a part of this description, in which:

FIGURE 1 is a vertical cross-sectional view of an apparatus constructed in accordance with the present invention and mounted within a gas well, portions being broken away and shown in section for clarity of illustration;

FIGURE 2, an enlarged vertical cross-sectional view taken substantially on the plane of line 22 of FIGURE 1;

FIGURE 3, an enlarged vertical cross-sectional view of a gas lift device comprising part of the apparatus of the present invention and shown in operative position with respect to associated portions of a well bore and tubing string;

FIGURE 4, a cross-section on an enlarged scale of the tubing string taken substantially along the plane of lines 4-4 of FIGURE 3;

FIGURE 5, a cross-sectional view of the catcher apparatus at the well head in inoperative position; and

FIGURE 6, a cross-sectional view of the catcher apparatus at the well head in operative position.

While only the preferred form of the invention is shown, it should be understood that various changes or modifications may be made within the scope of the claims attached hereto without departing from the spirit of the invention.

Description of the preferred embodiment Referring to the drawings in detail, it will be seen that the apparatus for automatically controlling liquid depth in gas Wells and oil wells of the present invention consists essentially of a liquid-gas separator 11 operatively positioned within a well bore 12, a tubing string 13 within the well bore 12 connected to the liquid-gas separator 11 to receive liquid accumulations 14 therefrom, and communicating with the surface 16, together with a gas lift device 17 connected to the tubing string 13 and responsive to a predetermined pressure therein for supplying gas under pressure from the well bore to the tubing string so as to lift a column of liquid 18 through the tubing string to the surface, and a free piston member 20 in the tubing string 13 for movement between the gas lift valve 17 and the surface 16 below the column of liquid 18.

In accordance with the present invention, the liquid-gas separator 11 is of the positive action type which will supply liquid to the tubing string so long as liquid is present at the entrance thereof, and which will automatically close off the liquid. entrance to the tubing string when the liquid supply thereat is exhausted. Liquid-gas separators of this type are disclosed in my US. Patent No. 2,291,902 issued Aug. 4, 1942 and entitled Gas Anchor, and in my co pending application Ser. No. 433,909 filed Feb. 19, 1965, and entitled Method and Apparatus for Effecting Gas Control in Oil Wells.

The liquid-gas separator 11 includes a valve means 19 adapted for communicating the tubing string 13 with the lower portion of the interior of an open top cylindrical bucket 21 mounted for vertical reciprocation within the well bore 12. The bucket 21 has a weight sufiicient to pull the valve means 19 open against the gas pressure in the well when the bucket is partially filled with liquid and also has an effective displacement sufiicient to float the bucket in the surrounding liquid when the bucket is substantially empty, for urging the valve means 19 closed.

As here shown, the liquid-gas separator 11 has its valve means 19 and bucket 21 operatively carried within a capsule 22 secured to the lower end of the tubing string 13. Openings 23 are formed in the capsule 22 to permit entry of liquid and gas from the well bore 12, and a bull plug 24 is provided at the lower end of the capsule 22 for cleaning out any debris which may accumulate.

- The valve means 19 is here shown as being mounted on the lower end of a tube 26 secured in coaxial relation within the capsule 22 and connected to the tubing string 13 to form an operative extension thereof. Valve means 19 here includes a ball check 27 formed to permit liquid to enter the tubing string but to prevent liquid from leaving the tubing string through the valve means. Also included in valve means 19 is a valve member 28 connected by a rod 29 to the bottom of bucket 21 for vertical movement therewith toward and away from a valve seat 31.

A quantity of liquid is contained within the capsule 22 at all times, this quantity being sufficient to cause the bucket, when empty, to float upwardly and seat valve member 28. When the liquid accumulation in the well bore 12 rises to the lowermost of the openings 23, it will pour into the capsule 22 and into the bucket 21. As the bucket fills, the floatation effect is destroyed and the weight of the bucket is sufiicient to pull the valve member 28 downwardly away from seat 31 against the pressure in the well bore. The liquid contained within bucket 21 is then free to enter the tubing string 13. As the supply of liquid in the bucket 21 is depleted, the floatation effect again overcomes the weight of the bucket and urges the valve member 28 upwardly to closed position. Thus, it will be seen that the liquid gas separator functions automatically to supply liquid to the tubing string 13 as soon as the liquid accumulation in the well bore reaches a predetermined level as determined by the openings 23. The liquid gas separator also functions automatically to close off communication between the tubing string 13 and the well bore 12as soon as the supply of liquid in the bucket 21 is eX- hausted to a predetermined level.

In accordance with the present invention, the gas lift device 17 is formed to respond to a predetermined static head of liquid in the tubing string 13 above the liquid gas separator 11 to supply gas under pressure from the well bore 12 to the tubing string a spaced distance below the liquid level therein so as to lift a column or slug 18 of liquid through the tubing string 13 for discharge therefrom at the surface 16.

Preferably, the gas lift device. 17 includes a valve formed for communicating the well bore 12 with the interior of tubing string 13, means tending to hold the valve in closed position with a predetermined force, and pressure responsive means in the gas lift device formed for overcoming the last named means and urging the valve to open position in response to a predetermined pressure in the tubing string.

As here shown the gas lift device 17 includes a housing 32 providing areference chamber 33 filled with a predetermined quantity of gas to provide a predetermined pressure. A bellows 34 is connected to the reference chamher 33 and to a valve member 36 which is movable vertically toward and away from a valve seat 37 upon expansion and contraction of the bellows.

The bellows 34 hermetically separates the chamber 33 from a valve chamber 38 provided by housing 32 and in which valve member 36 and valve seat 37 are contained. Chamber 38 is in communication with the interior of tubing string 13. Bellows 34 has an effective actuating area exposed to the pressure in chamber 38 which is larger than the effective actuating area of the valve member 36, as defined by the area of the valve seat 37 which communicates through ball check valve 39 with the interior of the well bore 12.

The reference pressure contained within chamber 33 is related to the effective actuating area of bellows 34, the effective actuating area of valve member 36, and the gas pressure in the well bore 12 in such manner that the valve 36 is urged downwardly to closed position until sufficient pressure exists in tubing string 18 to join with the upward force exerted on valve member 36 by the gas pressure in the well bore to overcome the downward force exerted by the reference pressure in chamber 33 and cause the valve 36 to move upwardly away from seat 37.

The free piston member is here shown as a sphere of diameter slightly less than the inside diameter of the tubing string 13. The member 20 rests on a stop 42 located just above the passage from chamber 38 into the tubing string 13 when no column of liquid 18 is being ejected from the tubing string 13. As the liquid accumulations 14 rise in the tubing string 13 due to operation of the liquid-gas separator 11, the liquid flows past the free piston member 20 until the static head imposed by the rising liquid exerts sufficient pressure in the chamber 38 to trigger the gas lift device 17 to open. The opening of the gas lift device 17 admits gas under pressure from the well bore into the tubing string 13 to exert pressure on the member 20 and the column 18 of liquid ahead of it, lifting the liquid and the member to the surface, where the liquid is discharged. The gas vents and the member 20 falls back down the tubing string 13 to the stop 42. It should be noted that the pressure in chamber 38, when valve 36 is closed, is determined by the static head of the liquid contained in the tubing string. Accordingly, the reference pressure contained in chamber 33, taken in connection with the geometry of the bellows 34 and valve and

seat

36 and 37 will determine the height the liquid will reach in the tubing string at which the described triggering open of the gas lift device will occur.

It may be seen that the gas admitted from the well bore by the gas lift device 17 exerts direct pressure on the liquid slug 18 only along a thin annular area between the piston member 20 and the wall of the tubing string 13. Most of the gas pressure is exerted on the piston member 20 which in turn exerts upward pressure on the liquid slug 18, so that the gas is prevented from bubbling and channeling up through the slug 18. This tends to preserve the driving force of the gas and holds the slug of liquid 18 together for the most rapid expulsion. The thinness of the annular area also promotes a beneficial sweeping action of the gas along the walls of the tubing string 13 to reduce fallback of liquid around the sides of the piston member 20. The thin annular clearance provided between the free piston member 20 and the wall of the tubing string 13 cuts the lubrication requirements to the point where they may be met by the fluid being expelled or by the material of which the piston is made, or both. This clearance also allows the use of the member 20 in tubing strings having a rough interior contour without requiring reaming of the tubing string.

When the slug of liquid reaches the surface and is discharged, as from pipe 41, the back pressure caused by the weight of the liquid slug will be removed and the pressure in reference chamber 33 will act through bellows 34 to cause the valve 36 to snap downwardly against seat 37. The gas lift device 17 will remain in its closed operative position until such time as suflicient liquid accumulates in the well to pass through the gas-liquid separator 11 and rise in the tubing string 13 to the desired height, whereupon the static head of the liquid will again trigger the gas lift device 17.

At the wellhead, the tubing string 13 connects to a catcher device 43, as illustrated in FIGURES 5 and 6. The catcher device 43 includes a section of tubing 44 of greater diameter attached to the top end of the tubing string 13. The tubing section 44 is pierced by a number of perforations 46 which pass the liquid and gas but retain the free piston member 20. The perforate portion of the tubing section 44 is surrounded by a housing 47 having an outlet 48 which collects the expelled fluid for disposal. The housing may, if desired, be vented by a vent 49.

When the liquid slug 18 and the free piston member 20 reach the wellhead, the liquid will be drained away through the perforations 46 and the outlet 48, and the propelling gas will escape from behind the free piston member 20 and be briefly vented. The free piston member 20 will impact against a resilient cushion 51 attached to a blind sleeve 53 at the top of the tubing section 44 and fall back down the tubing string 13.

A retainer tube 52 for catching the free piston member 20 is attached to the blind sleeve 53 which is in turn threaded onto the top of the tubing section 44. When not in use, the retainer tube and the blind sleeve are threaded on in the position shown in FIGURE 5 and enclosed by a protective cover 54 which also threads into the blind sleeve.

To catch the free piston member 20, the retainer tube 52 is removed from the top of the tubing section 44, inverted, and threaded back onto the tubing section 44 with the threads which formerly engaged the cover 54 now engaging the top of tubing section 44 as shown in FIGURE 6. The retainer tube 52 is slightly larger in inside diameter than the free piston member 20 but smaller in outside diameter than the tubing section 44, so that it fits inside tubing section 44 with enough clearance to readily pass the fluid. Like the tubing section 44, the retainer tube 52 has perforations 56 to pass the liquid and gas, and it has an additional perforation 57 which is large enough to pass the piston member 20 once the retainer tube 52 is withdrawn from the tubing section 44. Until the retainer tube is withdrawn, the exit of the piston member through the opening 57 is blocked by insufficient clearance between the retainer tube and the tubing section 44.

A stop member 58 is formed of a wedge-shaped block of resilient material attached to the wall of the retainer tube 52, with the thin edge of the wedge facing down the well. When the free piston member 20 is driven upward, it possess enough force to compress the stop member 58 and squeeze past, but when the free piston member falls downward again of its own weight, its force is insufficient and the wedge shape of the stop traps it. Another resilient cushion 59 like cushion 51 absorbs the impact of the piston member when the retainer tube 52 is in this catching position. The free piston member is removed for inspection or replacement by withdrawing the retainer tube 52 and reinverting it to allow the piston member 20 to pass out through the opening 57.

As a specific example of the free piston member of the present invention, such a member of the following characteristics has been constructed and successfully operated:

Shape of piston 20 Spherical Diameter of piston 20 in 1.875 Inside diameter of tubing string 13 (mm) in 1.995 Material of piston 20 Teflon Specific gravity of piston 20 (ref. water) 2.01

As may be seen from this example, the annular area between the piston member 20 and the tubing string 13 is about inch wide on each side of the piston. Provision of such a clearance, as noted above, eliminates the need for a lubricator device at the surface and also reduces the need for reaming the tubing string 13. The width of the annular area should not be great enough to permit gas to bubble or channel past the piston 26 into the column of liquid 18 when the column of liquid is being ejected, or to permit the free piston member 20 to be driven up into the liquid slug, destroying the sweeping action of the gas on the walls of the tubing string 13. Differences between the outside diameter of the free piston member 20 and the inside diameter ofthe tubing string 13 of A; to A in. have been found to be workable. With this range of clearances, the piston member 20 will drop freely down the tubing string and through accumulated fluid to the stop 42 when not propelled by the gas.

The free piston member of the example was constructed of Teflon, but other durable and low density materials could be equally well employed. While some advantage in lubrication is derived from the use of Teflon and other fluorinated hydrocarbon plastics, the clearance between the piston member and the tubing string and the lubricating action of the expelled fluid itself permit the use of a wide range of materials for the piston. For instance, the piston member could be a hollow stainless steel sphere, or any other suitable geometric shape, such as cylindrical, ovoid or conical, the important feature being the retention of the clearance between the piston member and the walls of the tubing string 13. The spherical configuration, however, possesses some advantages in avoiding hanging up of the piston in the tubing string and in reducing the area subject to viscous drag and other frictional forces.

The low overall density of the piston member 20 eliminates the necessity for complex and expensive shock absorbing apparatus at the bottom of the tubing string and at the wellhead to cushion the impact and absorb the momentum of the piston member when it is stopped. The light weight of the piston member also makes it possible to use the simple and inexpensive catcher apparatus provided herein. A savings in the propellant gas energy required to lift the piston member 20 to the surface is also realized with the light weight piston, allowing more fluid to be expelled with a given quantity of gas. With the light weight piston member, the piston lift may be used on Wells with tubing strings smaller than previously were feasible for adaptation to piston lift devices.

In a test installation, the piston member of the present invention was installed on a gas well formerly employing the dewatering system of the above cited Kelley application Ser. No. 451,187, now issued as US. Patent No. 3,324,803, resulting in a drop of 2/3 in propellant gas required as compared to the dewatering ssytem without the piston member.

The data given for the piston in the spezific example above are for a system for dewatering a gas well. With appropriate adjustments to the dimensions and density, the apparatus of the present invention is equally adaptable to the gas lifting of oil from oil wells. For this purpose, increased clearances between the free piston member 20 and the inside of the tubing string 13 are feasible due to the increased viscosity of the fluid. The overall density of the piston member should also be adjusted when the system is used for oil lifting, as the density should be sufficiently greater than the fluid to produce a rapid fall back through the fluid accumulations in the tubing string 13, without being so great as to waste the propulsive force of the gas.

In particularly deep wells, it may be necessary to install additional gas lift devices in order to lift the slug of liquid through the tubing string-to the surface. Each of these gas lift devices can be of a structure substantially the same as the gas lift device described and may function in a similar manner. Accordingly, detailed description of the structure and function of the additional gas lift devices should not be necessary.

The free piston member 29 coacts with the gas lift valve 17 to provide increased efiiciency of removal of fluid from the well and to allow use of the piston lift system in smaller tubing than heretofore feasible. The gas life valve and the free piston member in turn coast wi h the liquid-gas separator to produce a wholly automatic dewatering system which requires no surface controller or lubricator apparatus, and which minimizes waste of gas. The free piston member of the present invention permits the system to have greatly simplified shock-absorbing and catcher devices.

The surface controller is eliminated, as the separator 11 connects the tubing string 13 with the well bore 12 only when there is fluid in the bucket 21, and the gas lift admits only enough gas to the tubing string to eject the slug of liquid. No need then remains for any controller to open and close the tubing string 13 at the surface or to actua e any pumping device, and the upper end of the tubing string 13 may communicate with the atmosphere through the vent 49 at all times, if so desired.

While the free piston member and the gas lift device have been described here in combination with a positiveaction bottom-hole gas-liquid separator, it may be appreciated that the free piston member is of separate utility in combination with gas lift devices, and may be used to enhance their operation and improve their efiiciency in many other applications as well.

A great improvement in etficiency over previously known elongated Sliding contact members, or rabbits will accrue even if the bottom hole separator is not used. Thus, in wells which produce more liquid (oil or water) than can be flowed, or is allowed to be flowed, the bottom hole separator may be eliminated or some other type used. In such cases, the ball-piston of the present invention will still cooperate with the gas lift to afford a greatly improved result.

From the foregoing it will be seen that the liquid control for gas wells of the present invention operates automatically in a highly efiicient manner to intermittently eject unwanted accumulations of liquid within the well above a desired level, utilizing the gas pressure within the well. The apparatus includes a free piston member which improves lift action and conserves gas by preventing bubbling and channeling of the gas through the fluid slug being ejected, and requires neither lubrication nor sensing apparatus at the wellhead. The free piston member is usable with rough tubing without reaming and is lightweight to reduce its impact on the stops.

We claim:

1. An apparatus for controlling liquid depth in gas wells and oil wells, comprising a positive action liquid-gas separator operatively positioned within the well bore, a tubing string within the well bore connected to said liquidgas separator to receive liquid therefrom and communicating with the surface, a gas lift valve connected to said tubing string and responsive to a predetermined pressure therein for supplying gas under pressure from the well bore to said tubing string so as to lift a column of liquid through the tubing string to the surface, and a free piston member retained within said tubing string for movement between the gas lift valve and the surface below the column of liquid to assist the gas lift valve in driving the column of liquid from the well.

2. An apparatus for controlling liquid depth in gas wells and oil wells as describedin claim 1 and wherein said gas lift valve is positioned above said liquid-gas separator and said predetermined pressure is provided by the static head of liquid accumulated in said tubing string.

3. An apparatus for controlling liquid depth in gas Wells and oil wells as described in claim 1 and wherein said separator includes valve means controlled by emptying and filling of a bucket for allowing passage therethrough of a liquid while preventing passage of a gas, said tubing string being connected to the valve means of said separator to receive the liquid therefrom, said gas lift valve being positioned above and adjacent to said separator and responsive to the static head of liquid in said tubing string above said gas lift valve whereby when the liquid level in said tubing string reaches a predetermined height, said gas lift valve will open to inject gas below said free piston member to lift said free piston member and a column of liquid above it through said tubing string to the surface, said gas lift valve being responsive to the pressure drop in the tubing string occurring upon discharge of said column of liquid therefrom to shut ofl? the supply of gas under pressure from the well bore to said tubing string.

4. An apparatus for controlling liquid depth in gas wells and oil wells as described in claim 1 and wherein said liquid-gas separator is attached to the lower end of said tubing string at a desired location within the well and includes an open topped bucket formed for vertical reciprocation within the well bore, and valve means communicating said tubing string with the lower portion of the interior of said bucket, said bucket being connected to said valve means and having a weight sufficient to pull said valve means open against the gas pressure in the well when said bucket is partially filled with liquid and having an effective displacement suflicient to float said bucket in the surrounding liquid when said bucket is substantially empty for urging said valve means closed.

5. An apparatus as described in claim 4, and wherein said valve means is mounted in the lower portion of the interior of said bucket and includes a valve member movable vertically toward and away from a valve seat connected to the intake end of the tubing string, and a check valve providing one-way flow into the tubing string.

6. An apparatus for controlling liquid depth in gas wells and oil wells, as described in claim 1, and wherein said gas lift device includes a valve formed for communicating the interior of the well bore with the interior of said tubing string, means in said gas lift device tending to hold said valve in closed position with a predetermined force, and pressure responsive means in said gas lift device formed for overcoming said last-named means and urging the valve to open position in response to a predetermined pressure in said tubing string.

7. An apparatus as described in claim 6, and wherein said gas lift device provides a reference chamber filled with a predetermined quantity of gas to provide a pre-- determined pressure, a bellows connected to said reference chamber and said valve and formed to provide an effective actuating area larger than the effective actuating area of said valve whereby the pressure in said reference chamber acting through said bellows will hold said valve in closed position against gas pressure in said well bore until the pressure within said tubing string reaches a predetermined amount.

8. An apparatus for controlling liquid depth in gas wells and oil wells as described in claim 4, and wherein said gas lift device includes a valve formed for communicating the interior of the well bore with the interior of said tubing string, means in said gas lift device tending to hold said valve in closed position with a predetermined force, and pressure responsive means in said gas lift device formed for overcoming said last-named means and urging the valve to open position in response to a predetermined. pressure in said tubing string, and said free piston member is disposed in said tubing string and retained therein by a bottom stop and a catcher apparatus, said bottom stop being located to bring the member to rest immediately above the lowermost gas lift device in said tubing string, whereby said member will be lifted below said column of liquid to distribute the pressure of the gas admitted to said tubing string by said gas lift device across the bottom of said column of liquid, said catcher apparatus being located at the upper end of said tubing string and adapted to selectively retain and release said free piston member while passing liquid and gas through.

9. An apparatus as described in claim 8, and wherein said valve means is mounted in the lower portion of the interior of said bucket and includes a valve member movable vertically toward and away from a valve seat connected to the intake end of the tubing string, and a check valve providing one-way flow into the tubing string, and wherein said gas lift device provides a reference chamber filled with a predetermined quantity of gas to provide a predetermined pressure, a bellows connected to said reference chamber and said valve and formed to provide an effective actuating area larger than the effective actuating area of said valve whereby the pressure in said reference chamber acting through said bellows will hold said valve in closed position against gas pressure in said well bore until the pressure within said tubing string reaches a predetermined amount, and said free piston member is a spherical ball having a diameter approaching but not equalling the inside diameter of said tubing string, and said catcher apparatus comprising an upright first perforate section of tubing communicating with the top of said tubing string, a housing surrounding said section of tubing for collecting fluid and gas exiting from said section through the perforations, said housing having an outlet for conducting said fluid away for disposal, and a second perforate tubing section of inside diameter greater than said free piston member and optionally disposable within said first tubing section, said second tubing section being closed at one end and having a wedge shaped latch member of resilient material adjacent the end opposite said closed end formed to resist entry of said free piston member into said second tubing section with less force than it resists exit of said free piston member therefrom, said second tubing section having a resilient cushion disposed at said closed end for absorbing the impact of said free piston member thereagainst.

10. An apparatus as described in claim 8 and wherein an annular clearance of between about inch and about /8 inch is provided between said free piston member and the inside surface of said tubing string.

11. An apparatus for removal of liquid from gas wells and oil wells, comprising;

a tubing string within the well bore communicating with the liquid and the surface,

a gas lift valve connected to said tubing string for supplying gas under pressure from the well bore to said tubing string so as to lift a column of liquid through the tubing string to the surface,

a spherical separator in said tubing string having a diameter substantially less than the inside diameter of the tubing string so as to leave a clearance gap between said tubing string and said sperical separator,

and means locating said separator above said gas lift valve.

12. An apparatus as described in claim 11, and wherein said spherical separator has a diameter from about l/s inch to about 4 inch less than the inside diameter of said tubing string.

13. An apparatus as described in claim 11, and wherein said means includes a stop member mounted in said tubing string to project into the path of said sperical separator in position to halt downward fall of the latter through the tubing string at a location immediately above an inlet of said gas lift valve into said tubing string.

14. An apparatus as described in claim 11, and wherein said gas lift valve is responsive to a predetermined liquid head in said tubing string.

15. An apparatus as described in claim 14, and wherein said gas lift valve includes a valve formed for communicating the interior of the well bore with the interior of said tubing string, a reference chamber filled with a predetermined quantity of gas to provide a predetermined pressure, and a bellows connected to said reference chamber and said valve and formed to provide an effective actuating area larger than the effective actuating area of said valve whereby the pressure in said reference chamber acting through said bellows will hold said valve in closed position against gas pressure in said well bore until the pressure within said tubing string reaches a predetermined amount.

16. An apparatus as described in claim 11, and wherein a catcher apparatus is located at the upper end of said tubing string and is formed for receiving said spherical separator and selectively retaining and releasing same.

17. The apparatus as described in claim 16, and wherein said catcher apparatus comprises an upright first perforate section of tubing communicating with the top of said tubing string, a housing surrounding said section of tubing for collecting fluid and gas exiting from said section through the performations, said housing having an outlet for conducting said fluid away for disposal, and a secondperforate tubing section of inside diameter greater than said free piston member and optionally disposable within said first tubing section, said second tubing section being closed at one end and having a Wedge shaped latch member of resilient material adjacent the end opposite said closed end formed to resist entry of said spherical separator into said second tubing section with less force than it resists exit of said spherical separator therfrom, said second tubing section having a resilent cushion disposed at said closed end for absorbing the impact of said spherical separator thereagainst. 7

References Cited UNITED STATES PATENTS 2,556,867 6/1951 Carlisle et al. 103232 XR 2,813,490 11/1959 O'Neal IDS-52 3,090,316 5/1963 Montgomery 103-52 ROBERT M. WALKER, Primary Examiner.