US 3342203 A
Description (OCR text may contain errors)
Sept. 19, 1967 B. A. ABERCROMBIE 3,342,203
VALVE Filed June 14, 1965 izzr l NVENTOR.
BY Mm f lc United States Patent 3,342,203 VALVE Bolling A. Abercrombie, Houston, Tex., assignor, by mesne assignments, to McMurry Oil Tool Specialties,
Inc., Houston, Tex., a corporation of Texas Filed June 14, 1965, Scr. No. 463,550 r 12 Claims. (Cl. 137-155) ABSTRACT OF THE DISCLOSURE A gas lift valve apparatus having both a shutoff valve assembly and a throttling valve assembly, such throttling valve being connected to close prior to closure of the shutoff valve assembly and to open following the opening of the shutoff valve assembly.
This invention relates to a valve having a double seat. More particularly, the present invention relates to a valve which is constructed with a double seat, variable orifice, so that it will have a long life occasioned by the elimination of throttling across the main seat of the valve.
While the valves constructed in accordance with this invention are useful in many systems, they find particular utility in the oil and gas industry in the so-called gas-lift art.
In the gas-lift art, the gas may be a hydrocarbon gas, air or any other gas (though for safety reasons it is preferably one that will not support combustion in the context of its use). In all events, in this specification gas should be understood to mean gaseous type fluids generally, and not just hydrocarbon ticular gas.
In the operation of oil wells, and especially in wells wherein the pressure in the formation is insufficient for the economical operation of the well by formation pres sure alone, it is customary to make use of gas-lift mechanism by which gas under pressure may be introduced into the well from the surface to promote the outflow of oil.
The gas-lift method of well operation is usually carried out by connectinginto the well tubing a number of gaslift valves which are operable to permit the inflow of gas under pressure from the interior of a gas injection conduit, usually the annulus between well tubing and well easing, into a production conduit, usually the tubing, at longitudinally spaced intervals to cause an upfiow of oil and gas in the tubing. The gas-lift valves used in this method of operation are adjusted to be opened and closed upon the occurrence of approximately predetermined pressure conditions in the tubing and/ or casing, so that gas is permitted to enter the tubing only at a location and under pressure conditions to cause an outflow of oil.
In the operation of wells by this method one gas-lift valve in a string may be opened continuously for long periods of open flow, or a valve may be opened periodically to introduce gas under pressure from the annulus into the tubing intermittently.
Oil may be aerated by the gas injected into the production tubing, and thereby lightened for easier flowing; this is commonly known as the continuous flow technique. On the other hand, slugs of gas in a single bubble may be introduced into the well to act as a piston lifting a slug ofoil, much as a bubble of steam in a coffee percolator lifts water upward in the percolators tubing; this is the intermittent flow technique.
In one application of this general production method, gas-lift valves are provided with mechanism by which the valves are held in closed position by a predetermined force and are opened when the combination of pressure in the well annulus and well tubing exceeds a predetermined gas or any other par- 3,342,203 Patented Sept. 19, 1967 pressure value. Such valves are often constructed with closed bellows which are filled with gas under pressure and positioned to exert a closing force on the valve and to be acted upon by the pressure in the annulus to open the valve when this combination of pressures reaches a predetermined value. By the-use of a suitable timing mechanism for controlling the flow of gas from the surface source of gas under pressure into the well annulus, the opening of valves of this type may be regulated to introduce gas from the annulus into the well tubing at predetermined clock-determined intervals to cause the outflow of oil from the well through the tubing.
By the use of gas-lift valves of this type, the annulus pressure may be maintained at a predetermined value so that when the level of liquid in the tubing rises to a height to increase the pressure in the tubing on the valve by a predetermined amount, the valve will open.
In this and other systems, one of he biggest problems in the prior art structures is that the valves tend to throttle across the main valve seat. Such throttling, of course, results, in erosion of the valve stem and the adjacent valve seat. And the result of such erosion, of course, is that the useful life of the valve is greatly reduced, when compared with the projected life span of the same valve should such erosion be absent.
Since valves may be located at remote places in a system, for example, down-hole in the oil or gas well, it is often greatly expensive and inconvenient to replace a worn-out valve. A shut-down of a process may be necessary, but in any event, it is obvious that great savings in time, money, and efiiciency could result if a valve of longer life could be devised.
Accordingly, this invention seeks to provide an improved valve which eliminates throttling across the main seat of the valve at closure. The elimination of such throttling results in a valve which gives acceptable performance over periods of time much longer than that for valves presently on the market, due to the fact that the main seat of the valve constructed in accordance with the present invention is not cut awayby throttling gas. Valves constructed in accordance with this invention are thus efficient over relatively long periods of time, when compared with the prior art structures.
In order that the manner in which the foregoing and other objects attained in accordance with the invention can be understood in detail, one advantageous embodiment 'of the invention will be described with reference to the accompanying drawings, which form a part of the specification, and wherein:
FIGURE 1 is a horizontal section view of a valve constructed in accordance with one embodiment of this invention, showing the valve in the closed position.
FIGURE 2 is a horizontal section of the valve of FIG- URE 1, wherein the main stem is in the open position and the throttling stem is in the closed position.
FIGURE 3 is a horizontal view of the valve of the FIGURE 1 embodiment, showing the valve in the throttling position.
FIGURE 4 is a horizontal section view of the valve illustrated in FIGURE 1, showing the valve in the full open position.
FIGURE 5 is an exploded section view of the throttling stem portion of the valve stem, illustrating in detail the scratches on the surface of this throttling stern portion.
The preferred embodiment of this invention, which is illustrated in the above figures, may be characterized as a valve 2 which comprises an outer casing or housing 4. This outer casing or housing includes, at one end thereof, a coupling element 6 which is in threaded engagement at 10 with the remainder of the housing. Also included in the housing are apertures 48 which are upstream from the valve seat. These apertures allow the pressure upstream of the valve seat to be the same as the pressure in the environment on the exterior of the housing. For instance, when the valve seat to be used in a gas-lift system, the valve stem will be exposed to the so-called casing pressure, while the pressure at the valve seat will be tubing pressure.
Coupling element 6 has a lower end counterbore 8 opening into the interior of the upper housing section 4 and within which counterbore an annular valve seat forming member 12 is positioned. The seat forming element may be retained in the counterbore by means of a snap ring 14 releasably fitted into an internal groove 22 provided for the same in the coupling element 6. Suitable seal forming means, such as the O-ring 16 is disposed in a groove provided for the same in the seat forming element to form a fluid tight seal between the seat forming element and the coupling element 6.
Valve member 24 is comprised of a main stem 26 and a throtting stem 28, the throttling stern and the seat forming element 12 being so constructed that the throttling stem will seat before the main stem of the valve.
Throttling stem 28 comprises a body portion 40 and a head portion 42. Body portion 40 is cylindrical in shape and extends axially into main stem 26, being sealed in sliding engagement therein by quad ring 44. Head portion 42 of throttling stem 28 projects beyond the seat end of the main valve stem, so that this head portion must necessarily seat before the main stem will seat.
Although the head portion 42 of throttling stem 28 may take various forms, the construction shown in the accompanying drawings is preferred; here the head portion is shown in the form of a frustro-conical section. Running along the surface of said section, between the small base and the large base, and parallel to the altitude of the section, are one or more scratches 30, which are shown particularly well in FIGURE 5.
Main stem 26 has therein apertures 34 which are in exact alignment on opposite sides of the main stem. Of considerably smaller diameter than these apertures is pin 36, which is engaged with the body portion of throttling stem 14 through said apertures. The throttling stem is thus free to move back and forth along the axis of the main valve stem within the limits controlled by the relative sizes of the pin 36 and the apertures 34. That is, the throttling stem is free to slide back and forth relative to the main stem as long as the pin 36 is within the aperture portion of the main stem; but when the pin comes into contact with the main stem itself, movement is of course stopped.
Main stem 26 has an externally threaded projection 38 at its end opposite the valve seat, at which point the main stem is in engagement with the valve carrier 32. It is understood that the carrier 32 may be actuated by any conventional urging means (not shown) which will urge the carrier to move the valve member to seat.
Reference may be made to McMurry Patent No. 3,175,- 514, issued Mar. 30, 1965, for a more complete understanding of such an actuating mechanism.
Valve seat-forming element 12 comprises a main seat 18, and is tapered inwardly from said main seat to a throttling seat 20. The tapered internal portion of the seatfor'ming' member will generally correspond to the construction of the head portion 42 of the throttling stem 28,
so as to mate with this head portion. Thus in the embodi- 6 ment illustrated, the hollow interior portion of the seatforming member between the main seat 18 and the throttling seat 20 is in the form of a frustro-conical section.
As is more clearly seen in FIGURE 5, the head portion 42 of the throttling stem and the tapered internal portion of the seat-forming member do not exactly mate. That is, there is a constriction or seat 56 at some point intermediate the ends of head portion 42 when the valve is in the FIGURE 1 position. And, of course, it is at point 56 that the valve is closed when in that position.
It is seen that when the valve is open, i.e., when neither the main stem 26 or the throttling stem 28 is seated, there is communication between the fluid in the area 52, and the area 54, through the volumes 60 and 62 and the port 50. On the other hand, when the valve is closed, there is no such communication.
The annular area at the end of main valve stem 26 which is exposed to the volume 60 when the valve is in the position shown in FIGURE 1 is noted as the area 58. This area corresponds, of course, to the difference in the circumference defined by the seat 18 and the circumference of the body portion 40 of throttling valve stem 28. The area of the top of head portion 42 of throttling valve 28 is noted as the area 46.
Operation The operation of valves constructed in accordance with this invention can be best understood by reference to the illustrated embodiment and the accompanying drawings, FIGURES 1-4. In order to fully describe one particularly useful embodiment, the operation of the valve will be described as used in a gas-lift system.
In FIGURE 1, the illustrated valve is shown in the closed position, i.e., there is no communication between the fluid in the area 52 and the area 54 through the port 50. In normal operations in the gas-lift system, the area 52 represents the area occupied by the gas in the annulus between the tubing and the borehole; the pressure exerted by this gas will be termed the casing pressure. The area 54 represents the area occupied by the fluid inside the tubing of the well; the pressure in this area will be termed the tubing pressure.
When the relative pressures of the gas in the casing, the gas in the tubing, and the pressure exerted by the urging means become such (see, for example the afore mentioned patent to McMurry) that the valve tends to open, it will do so in the order illustrated in FIGURES 2, 3, and 4. First, the valve will assume the position illustrated in FIGURE 2. In this position, the main stem 26 has moved away from the main seat 18 allowing casing pressure to enter volume 60 to replace the tubing pressure which had occupied this volume 60 when the valve was in the FIGURE 1 position. Since the casing pressure must be greater than the tubing pressure, this change exerts an additional opening force on the main stem 26 equal to the pressure differential between casing and tubing pressure times the annular area 58 of the valve stem which is exposed to volume 60 when the valve is in the FIGURE 1 position. Thus the main stem 26 is urged away from the main seat until the apertures 34 come in contact with the pin 36. At this time, an additional force urging the valve to remain closed is added to the system. This additional force is equal to the pressure differential between the casing pressure and the tubing pressure times the area of the end portion 46 of the head 42 of throttling stem 28. In the preferred embodiment of this invention, the annular area 58 is slightly greater than the area of the top 46 of head portion 42 of throttling stem 28, so that when the main stem 26 opens, the valve immediately assumes the position shown in FIGURE 2. In the FIG- URE 2 position, fluid passage is only across the scratches 30 with tubing pressure being maintained in area 54 and easing pressure being maintained in area 52 and volume 60.
Additional force urging the valve open, either an increase in tubing pressure or casing pressure, will cause the valve to assume the position shown in FIGURE 3. The additional movement of the head portion 42 of the throttling stem 28 allows an increased area 62 for fluid flow between casing and tubing. correspondingly a decrease in either casing pressure or tubing pressure will cause the valve member 24 to move toward the closed position, thus decreasing the area 62 and further restricting the passage of fluid between casing and tubing, or even a return to the FIGURE 2 position. Thus it can be seen that with the valve positioned as shown in FIGURE 3, exact control of fluid passage can be achieved and all tendency for erosion is located downstream of the main valve seat 18 and stem 26.
Since the opening force exerted by the casing pressure is normally much greater than that exerted by the tubing pressure, it can be seen that by a small variation in casing pressure the flow passage and thus the flow volume can be increased greatly without a considerable increase in casing pressure, as required where a fixed area choke or throttling device is used.
Where the opening forceis increased considerably, thus urging the valve member 24 to the position shown in FIGURE 4, the flow area 62 no longer remains the primary restriction to flow, this restriction being transferred to port 50. In this position, an additional force urging the valve to remain open is added to the system, this force being equal to the differential pressure between casing and tubing times the area defined by seat 56. In the FIGURE 4 position, since port 50 is the primary restriction, it can be seen that the entire force exerted to hold the valve open is exerted by the casing pressure, changing the characteristics of the system to such that a decrease in casing pressure is necessary for the valve to close. In other words, the system is no longer responsive to tubing pressure. This is the type of operation normally used for socalled intermitting lif whereas the throttling type of operation is usually used for continuous flow. Thus it can be seen that the system embodied by this invention can accomplish both types of gas lift, i.e., continuous flow where the lift fluid is injected continuously into the annulus between the tubing and casing; or intermittent lift where gas is injected intermittently at very rapid rates into the annulus, thus causing a rapid pressure increase therein.
A decrease in the casing pressure which urged the valve to assume the position shown in FIGURE 4 will cause the valve member 24 to reassume the position shown in FIGURE 3, thus allowing the flow restriction to revert to the throttling head 42 and the throttling seat 20, preventing throttling across the main seat 18 and stem 26 and causing tubing pressure to again become an effective force urging the valve to remain open. From the position shown in FIGURE 3, a further decreaase in either casing or tubing pressure will cause the valve to assume the position shown in FIGURE 2 whereby the only flow passage is through the scratches 30. In this position, casing pressure only urges the main stem 26 to remain in the open position, so only a decrease in casing pressure will cause the main stem 26 to move to the main seat 18. When the main stem 26 moves toward the main seat 18 sufliciently to cause a restriction smaller than that of the scratches 30, the pressure in volume 60 changes from casing pressure to tubing pressure, thus removing a portion of the force urging the main stem 26 open and causing the main stem to snap closed. This snap action prevents any possibility of throttling across the main stem 26 and main seat 18.
It is thus seen that a distinctly advantageous valve has been developed which will solve the aforementioned problems with simplicity and efficiency. Though the valve of this invention has been described in terms of one embodiment which has been found to be particularly advantageous, it is apparent that numerous changes might 'be made in the valve or in the system in which it is used without departing from the scope of this invention.
What is claimed is:
1. A combination throttling and shutoff valve assembly comprising a hollow valve body having a first inlet and a second inlet and having a fluid passageway therebetween encompassed by a shutoff seat at a first location and a throttling seat at a second location spaced between said first location and said second inlet,
a throttling member disposed in said passageway to be 6 urged againstsaid throttling seat for throttling fluid flow through said passageway, and
a shutoff member trailingly disposed in said passageway relative to said throttling member to be urged into fluid-tight engagement with said shutoff seat following engagement of said throttling member'with said throttling seat.
2. The valve assembly as described in claim 1, wherein said throttling member is urged against said throttling seat in response to a pressure differential across said throttling and shutoff seats.
3. The valve assembly as described in claim 2, wherein said throttling member is movable into throttling engagement with said throttling seat independently of said shutoff member.
4. The valve assembly as described in claim 3, wherein said shutoff member is slidably disposed about said throttling member for disengaging from said shutoff seat and after moving independently of said throttling member a limited distance from said shutoff seat engaging with and moving said throttling member out of throttling engagement with said throttling seat.
5. The valve assembly as described in claim 4, wherein said shutoff member and said throttling member are cooperatively movable toward said throttling seat until said throttling member engages said throttling seat, and
wherein said shutoff member is thereafter movable into engagement with said shutoff seat independently of said throttling member.
6. The valve assembly as described in claim 5, wherein said shutoff seat encompasses a larger cross sectional area than said throttling seat.
7. The valve assembly as described in claim 6, wherein said throttling member is provided with at least one groove to permit a limited fluid flow across said throttling seat when in throttling engagement therewith.
8. The valve assembly as described in claim 6, wherein said assembly includes a hollow valve insert removably disposed in said valve body across said passageway, and
wherein said shutoff and throttling seats are located in said valve insert.
9. A combination throttling and shutoff valve assembly comprising a hollow valve body having a first inlet for communication with a first pressure and a second inlet for communication with a second pressure and having a fluid passageway therebetween with a shutoff seat portion encompassing said passageway at a first location and a throttling seat portion encompassing said passageway at a second location spaced between said first location and said second inlet,
a throttling member disposed between said throttling seat and said first inlet to be moved by said first pressure into throttling engagement with said throttling seat in response to a differential between said first and second pressures, and
a shutoff member for sealing engagement with said shutoff seat and further adapted. after disengaging and moving a limited distance from said shutoff seat to engage and move said throttling member out of throttling engagement with said throttling seat.
10. A combination throttling and shutoff valve assembly comprising a hollow valve body having a high pressure inlet and a low pressure inlet with a passageway therebetween and having a shutoff seat encompassing a first area and a throttling seat spaced from said shutoff seat generally towards said low pressure inlet and encompassing a second area smaller than said first area,
a throttling valve member movably disposed in said valve body between said throttling seat and said high pressure inlet and having a throttling head adapted to be urged into throttling engagement with said throttling seat by fluid pressure through said high pressure inlet and a shank member extending through said shutoff seat generally towards said high pressure inlet, 4 I
a shutoff valve member movable to and from said shutofl? seat in response to variations in fluid pressure adjacent said high pressure inlet and having a shutoif head slidably disposed about said shank member and adapted for fluid-tight engagement with said shutofl seat, and
linking member connected with said shank member for engagement with said shutoff valve member to draw said throttling head out of throttling engagement with said throttling seat after said shutofi valve member moves out of engagement with and away from said shutoff seat a preselected distance.
11. The valve assemblydesc-ribed in claim 10, including sealing means disposed about said shank member to provide a fluid seal between said shank member and said shutofi head.
References Cited UNITED STATES PATENTS Knauf 137-629 Rose 137630.14 Hurlbu'rt 137-63014 Lilly 103232 McMurry 103232 Garrett 137155 Carializo 2 103232 DONLEY J. STOCKING, Primary Examiner.
W. I. KRAUSS, Assistant Examiner.