US3672397A

US3672397A - Well safety valve

Info

Publication number: US3672397A
Authority: US
Inventors: Fred E Watkins; Gilbert H Tausch
Original assignee: Camco Inc
Current assignee: Camco Inc
Priority date: 1971-01-11
Filing date: 1971-01-11
Publication date: 1972-06-27
Anticipated expiration: 1989-06-27
Also published as: GB1351365A

Abstract

A well safety valve for use in a well tubing for closing the flow of fluids through the tubing when the fluid pressure in the tubing decreases to a predetermined amount. A valve housing adapted to be positioned in the tubing and having a passageway therethrough for the flow of well fluid and a valve element below a valve seat with a piston positioned below and supporting the valve element. The piston being exposed to pressure in the passageway and extending into a closed cylinder which includes means acting in a direction to seat the valve element when the pressure in the tubing falls to a predetermined value. The crosssectional area of the valve element being greater than the crosssectional area of the piston to keep the valve closed after closure. Selective adjustment means on the piston and cylinder for selecting the pressure at which the valve will close.

Description

Unite States Patent Watkins et al.

[54] WELL SAFETY VALVE Filed:

Inventors:

Assignee:

Appl. No.:

Fred E. Watkins; Gilbert H. Tausch, both of Houston, Tex.

Cameo, incorporated, Houston, Tex.

Jan. 11, 1971 ..Fl6k 15/04 1 37/529, 509, 522, 523, 404, 137/528, 536, 494, 539.5

Relerences Cited UNITED STATES PATENTS Nelson ..137/522 X Gallagher... ...l37/522 X Hayes ....i37/523 Valentine 137/509 June 27, 1972 [57] ABSTRACT A well safety valve for use in a well tubing for closing the flow of fluids through the tubing when the fluid pressure in the tubing decreases to a predetermined amount. A valve housing adapted to be positioned in the tubing and having a passageway therethrough for the flow of well fluid and a valve element below a valve seat with a piston positioned below and supporting the valve element. The piston being exposed to pressure in the passageway and extending into a closed cylinder which includes means acting in a direction to seat the valve element when the pressure in the tubing falls to a predetermined value. The cross-sectional area of the valve element being greater than the cross-sectional area of the piston to keep the valve closed after closure. Selective adjustment means on the piston and cylinder for selecting the pressure at which the valve will close.

2 Claims, 3 Drawing Figures WELL SAFETY VALVE BACKGROUND OF THE INVENTION It is common practice in the production of petroleum products such as oil or gas from a well to provide a safety valve located within the production tubing in the well that will allow the passage upwardly of fluid through the tubing to the surface under normal operating conditions, but will close the flow of fluid under abnormal conditions. I

Some abnormal conditions, such as the loss of pressure controls at the wellhead, will cause a decrease in pressure in the well tubing. The present invention is directed to the provision of a safety valve for use in a well tubing for closing the tubing when the pressure in the tubing decreases to a predetermined value. I

SUMMARY The present invention is directed to a safety valve which is held opened by the force of the tubing pressure on the safety valve but which allows the safety valve to close when the tubing pressure decreases to a predetermined value.

A further object of the present invention is the provision of a safety valve-having a housing adapted'to be positioned in the tubing with a passageway therethrough for the flow of well fluid and a valve seat in the passageway. A valve element is adapted to seat on the valve seat and is positioned below the valve seat and a piston which supports the valve elementihas a first end exposed to the tubing pressure for holding the valve open and a second end slidably extending into a cylinder with means in the cylinder normally acting to close the valve against the tubing pressure.

A further object of the present invention is the provision of a safety valve which is normally held opened by the action of the tubing pressure workingon a'piston which has a second end extending into a sealed cylinder wherein various means such asfluid pressure or spring means may be provided in combination or individually to selectively close the safety valve at a desired tubing pressure.

Still a further object is the provision of a piston and cylinder actuated safety valve in which the piston and cylinder have coacting sections of different cross-sectional areas between which sealing means may be selectively positioned for selecting the tubing pressure at which the safety valve will close.

Yet a further object of the present invention is the provision of a piston and cylinder actuated safety valve for moving a valve element ontofa valve seat in which the cross-sectional area of the valve element is greater than the cross-sectional area of the piston thereby keeping the safety valve in the closed position afterclosure.

Yet a still further object of the present invention is the provision of a piston and closed cylinder actuated safety valve in which any failure in the sealing element between the piston and cylinder results in a fail safe operation.

BRIEF DESCRIPTION OF THE DRAWINGS In the attached drawing, like character references refer to like parts through the several views in which,

H6. 1 illustrates an elevational cross-sectional view of a production tubing in a well in which the safety valve of the present invention is located,

FIGS. 2A and 2B are enlarged elevational cross-sectional views in continuation of the safety valve of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and particularly to FIG. I, a conventional production tubing is shown in a well bore 12 for producing petroleum products such as oil and gas. As previously noted, it is conventional to provide a safety valve 18 set in the tubing string 10 by a conventional setting tool to shut off the flow of fluid through the production string 10 in the event of the occurrence of adverse operating conditions.

For example, the safety valve 18 may be connected through a conventional equalizing valve 17 to a Camco M lock 11 which is conventionally set in a Camco Magnaset nipple l4 and no further description is believed to be necessary.

Referring now to FIG. 2, a safety valve, generally indicated by the reference numeral 18, includes a housing 20 having a passageway 22 therethrough and a valve seat 24 in the passageway. The lower end of the passageway 22 includes a plurality of openings 26 for receiving fluid flow from the tubing 10 from below the valve seat 24 and the upper end of the passageway 22 above the valve seat 22 is in communication with the upper portion of the tubing 10 for conducting well fluids to the surface. A valve element such as ball 28 is provided which, when seated on'the valve seat 24, closes the passageway 22 and prevents the flow of well fluids upwardly through the passageway 22. As shown in FIGS. 2A, the ball 28 is in normal operation positioned off of the valve seat 24 thereby allowing the passage of well fluids through the tubing 10.

A piston 30 is provided positioned below the valve element 28 and has an upper end which supports the valve 28 such as by a pedestal 32. The lower end of the piston 30'is telescopi- 'cally and slidably positioned in a closed cylinder 34 through seal means such as seal 36. it is to be noted that the upper end of the piston 30 is exposed to the pressure of the well fluid in the tubing 10 below the valve seat 24. Thus the tubing pressure acting upon the cross-sectional area of the piston 30 enclosed by the seal 36, and having a radius, here shown as 38, provides a force acting to move the piston 30 into the cylinder 32 and away from the valve seat 24. Thus, the tubing pressure in the tubing 10 acts in a direction to hold the valve element 28 away from the valve seat 24 and thus holds the valve in the open position.

Suitable means are provided in the. closed cylinder 34 yieldably acting on the piston 30 in a direction to seat the valve element 28 on the valve seat 24 and close the safety valve 18. For example, the cylinder 34 may contain a pressurized fluid which acts against the lower end of the piston 30 to move the piston 30 out of the cylinder 34 and seat the ball 28 on the valve seat 24. The pressure in the cylinder 34 is selected at a value less than the normal operating pressure of the fluid in the tubing and thus under normal operating conditions the tubing pressure will move the piston 30 into the cylinder 34 keeping the valve in the open position. However, in the event that the tubing pressure should decrease, such as might occur in the event of a failure of the control equipment (not shown) at the top of the tubing 10 at the well surface, the then greater pressure in the cylinder 34 would move the piston 30 upwardly and close the valve. If the pressure in the cylinder 34 is low, for example atmospheric, a spring 40 may be provided in the cylinder 34 acting against the lower end of the piston 30 in a direction to seat the valve element 28 and the valve seat 24. Thus the movement of the piston 30 into and out of the cylinder 34 may be selected to cause the valve 18 to close when the tubing pressure decreases to a predetermined value.

By using the spring 40 and a substantially atmospheric pres- I sure in the cylinder 34, a safety valve is provided of a type which is essentially temperatureinsensitive. It is also to be noted that leakage into the cylinder 34 through the seal 36 will create an additional force in a direction to close the valve thereby resulting in a fail safe operation.

The valve 18 can be set to close at a desired predetermined value by changing the strength of the spring 40 or changing the area of the piston which is subjected to the tubing pressure. The effective cross-sectional area of the piston may be easily changed by providing the piston 30 with sections of different cross-sectional areas, here shown as two sections, 42 and 44, and providing the cylinder with coacting sections of difierent

cross-sectional areas

46 and 48, which coact respectively with

piston sections

42 and 44. Each different cross-sectional area includes an

O ring groove

50 and 52, respectively. Thus, by omitting the O ring seal 36 and placing an O ring seal in the groove 52 the effective cross-sectional area of the piston which is acted upon by the tubing pressure and the pressure in the cylinder 34 will be changed thereby changing the selected pressure at which the valve is closed.

Of course, the spring 40 may be omitted and the chamber 34 may be charged under pressure to a value to cause the valve to close at the selected reduced tubing pressure. A valve in which the spring 40 is omitted and which is actuated by a pressure charge in the cylinder 34 would be temperature sensitive. However, such a type of actuation would have the advantages over a spring actuated type of valve of (l) a lower differential pressure across the piston seal 36, which in nonnal service reduces the tendency of the seal 36 to leak, and (2) there will be reduced drag on the seal 36 as a result of the lower diflerential pressures thereby reducing the pressure change required for operation and thus providing a more accurate closing pressure.

While the ball 28 may be secured to the top of the piston 30, it is preferable that the ball be freely supported on the pedestal 32 whereby the ball 28 is self-sealing on the valve seat 24 thereby avoiding the precise alignment of the longitudinal axis of the piston 30 with the longitudinal axis of the valve seat 24. In addition, it is to be noted that the cross-sectional area of the valve element 28 and valve seat 24 is greater than the crosssectional area of the piston 30. Thus, when the valve element 28 is seated on the seat 24, the external tubing pressure will normally tend to increase. Therefore, the net forces will be acting in a direction to keep the ball 28 seated on the valve seat 24 and maintain a sealing relationship therewith with increased tubing pressure regardless of whether the ball 28 is secured to or freely supported from the top of the piston 30.

Another advantage of the present invention is that since the valve 18 is relatively insensitive to differential pressures resulting from flow and is set to close by fluid pressure and not fluid flow, it is not necessary to build in restrictions in the valve 18 to generate differential flow pressures. Thereby large flow passages may exist for all valve settings. Furthermore, pulsating action of fluid flow through the tubing does not adversely affect the operation of this pressure actuated valve as could be the case in a differential flow type valve.

To protect the valve seat 24 from the cutting action of solid particles in the fluid flow from the production formation, a tubular shield 56 may be provided, such as shown in US. Pat. No. 3,474,861, which slidably extends through the valve seat 24 so that its lower end 58 extends below the valve seat causing the impingement of flow and solid particles to be absorbed by the lower end 58 of the shield 56 instead of the valve seat 24. A spring 60 may be provided to maintain the shield member 56 in the lower position, but allows the shield 56 to move upwardly and away from the valve seat 24 when the ball 28 seats on the seat 24.

In use, the safety valve 18 of the present invention is preset at the surface by adjusting such factors as the strength of spring 40, the pressure in the cylinder 34 and the area of the piston 30 whereby the valve will close when the tubing pressure decreases to a predetermined value. The safety valve is then inserted into the tubing and set as is conventional. In the event that the pressure in the well tubing 10 below the valve seat 24 decreases to the set predetermined value, valve 18 will close blocking all flow through the until reopened.

The present invention, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein.

What is claimed is:

1. A safety valve for use in a well tubing for closing said tubing when the pressure in the tubing decreases to a predetermined value comprising,

a housing adapted to be positioned in said tubing and having a passageway therethrough for the flow of well fluid,

a valve seat in said passageway,

a valve element adapted to seat on the valve seat and close said passageway and positioned in said passageway below said valve seat,

a piston positioned below and supporting said valve element, said piston exposed to the pressure in the passageway,

a closed cylinder sealingly receiving the lower end of the piston,

means in the cylinder yieldably acting on the piston in a direction to seat said valve element on the valve seat,

said piston including sections of different cross-sectional areas and the cylinder includes coacting differential cross-sectional areas whereby sealing means can be inserted between the desired sized areas of the piston and cylinder for determining the tubing pressure at which the valve will close.

2. A safety valve for use in a well tubing for closing said tubing when the pressure in the tubing decreases to a predetermined value comprising,

an elongate housing adapted to be concentrically positioned in said tubing and having a passageway therethrough for the flow of well fluid upwardly through the housing,

a valve seat in said passageway,

said housing including radially positioned inlet openings below and adjacent said valve seat for admitting well fluid into the passageway and seat and above said valve element,

a piston positioned below and supporting said valve element, said piston exposed to the tubing pressure in the passageway,

a closed cylinder having a seal for sealingly receiving the lower end of the piston,

fluid in said cylinder under a fixed pressure less than the normal tubing pressure but greater than atmospheric pressure whereby the valve is held open under normal tubing pressure but closes when the tubing pressure decreases to a predetermined value, and

the cross-sectional area of the valve element is being greater than the cross-sectional area of the piston whereby the valve remains closed when seated until opened from above.

the safety tubing 10 F i l

Claims

1. A safety valve for use in a well tubing for closing said tubing when the pressure in the tubing decreases to a predetermined value comprising, a housing adapted to be positioned in said tubing and having a passageway therethrough for the flow of well fluid, a valve seat in said passageway, a valve element adapted to seat on the valve seat and close said passageway and positioned in said passageway below said valve seat, a piston positioned below and supporting said valve element, said piston exposed to the pressure in the passageway, a closed cylinder sealingly receiving the lower end of the piston, means in the cylinder yieldably acting on the piston in a direction to seat said valve element on the valve seat, said piston including sections of different cross-sectional areas and the cylinder includes coacting differential crosssectional areas whereby sealing means can be inserted between the desired sized areas of the piston and cylinder for determining the tubing pressure at which the valve will close.

2. A safety valve for use in a well tubing for closing said tubing when the pressure in the tubing decreases to a predetermined value comprising, an elongate housing adapted to be concentrically positioned in said tubing and having a passageway therethrough for the flow of well fluid upwardly through the housing, a valve seat in said passageway, a valve element adapted to seat on the valve seat and close said passageway and positioned in said passageway below said valve seat, said housing including radially positioned inlet openings below and adjacent said valve seat for admitting well fluid into the passageway and seat and above said valve element, a piston positioned below and supporting said valve element, said piston exposed to the tubing pressure in the passageway, a closed cylinder having a seal for sealingly receiving the lower end of the piston, fluid in said cylinder under a fixed pressure less than the normal tubing pressure but greater than atmospheric pressure whereby the valve is held open under normal tubing pressure but closes when the tubing pressure decreases to a predetermined value, and the cross-sectional area of the valve element is being greater than the cross-sectional area of the piston whereby the valve remains closed when seated until opened from above.