Equalizing Means For Well Safety Valves

Abstract

Equalizing means are provided for reducing the pressure differential across the seat of a well safety valve when opening the valve to avoid damage to the valve element and seat. A passageway communicates with a point below the valve seat to a point above the valve seat and includes an equalizing valve which is closed when the valve is closed and opens prior to the opening of the safety valve. The pressure in the passageway downstream of the equalizing valve acting on the valve in a direction to keep the safety valve closed. A restriction in the passageway upstream of the equalizing valve dampens the speed of opening the well safety valve.

Description

BACKGROUND OF THE INVENTION

It is common to provide subsurface safety valves in wells in the oil and gas industry to close the well and prevent the flow of fluid to the surface in the event of problems or equipment failure, such as described in Bulletin S-105 of Camco, Incorporated dated January 1971, entitled Well Safety Systems.

However, when the well safety valve is actuated and closed, there may be a large pressure differential across the valve caused by a high shut in pressure below the valve and a low pressure above the valve. When the valve is later opened the high differential pressure across the valve may damage the valve element and seat. Of course, the pressure in the well tubing above the safety valve could be pressurized from the well surface to equalize the pressure across the safety valve prior to opening, but in many installations this is not feasible for various reasons. The present invention is directed to improvements in equalizing means for reducing the pressure differential across the valve element and valve seat of a well safety valve when opening the valve.

SUMMARY

The present invention is directed to providing an equalizing means for reducing the pressure differential in a well safety valve when opening the valve including a passageway in the safety valve in communication with a point below the valve seat to a point above the valve seat which includes an equalizing valve which is closed when the safety valve is closed and opens prior to the opening of the safety valve for admitting well tubing pressure into the safety valve.

Another feature of the present invention is the provision wherein the pressure in the passageway upstream of the equalizing valve provides a resultant force against the valve in a direction to keep the valve closed.

A still further object of the present invention is the provision of a restriction downstream of the equalizing valve for reducing the speed of opening of the safety valve for preventing damage to the safety valve.

Other and further objects, features and advantages will be apparent from the following description of a presently preferred embodiment of the invention, given for the purpose of disclosure, and taken in conjunction with the accompanying drawings where like character references designate like parts throughout the several views.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view, partly in cross section and partly schematic, illustrating the use of a well safety valve in a well tubing,

FIG. 2A is a fragmentary elevational view of the top portion of one type of well safety valve utilizing the present invention and shown in the closed position,

FIG. 2B is a continuation of FIG. 2A, and

FIG. 3 is a fragmentary elevational view, in cross section, of the lower portion of the safety valve of FIG. 2B, showing the valve in the open position.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The equalizing means of the present invention will be described, for purposes of illustration only, as used in a Camco Type B safety valve, although it is to be understood that the present invention can be used with various other types of well safety valves. which is adapted to be connected to a well lock 12 such as a conventional Camco M lock and locked in position in the tubing 14 of a well to permit production therethrough under normal operating conditions, but in which the valve 10 may close or be closed in response to abnormal conditions. A control line 16 may be provided leading from the surface to a position in the well tubing 14 between a seal 18 on the lock 12 and a seal 18 on the safety valve 10. Conventional control means 20 are provided for controlling the fluid in the line 16 to control the actuation of the safety valve 10.

Referring now to FIGS. 2A and 2B, the safety valve 10 generally includes a valve body 22 which has an annular valve seat 24 therein and a valve element such as flapper 26 connected to the body 22 by a pivot pin 28. Thus when the flapper 26 is in the upper position seated on the valve seat 24, the safety valve 10 is closed blocking flow upwardly therethrough. A movable member or sliding tube 30 is telescopically movable in the body 22 and through the valve seat 24.

As best seen in FIG. 3, when the sliding tube 30 is moved to a downward position, the tube 30 pushes against the flapper 26 and moves it away from the valve seat 24. Thus, the valve is held in the open position so long as the sliding tube 30 is in the downward position. When the sliding tube 30 is moved upwardly, as best seen in FIG. 2B, the flapper 26 is allowed to move upwardly closing the valve by action of a spring 32 and also by the action of fluid flow moving upwardly through the bore 13 of the body 12.

Various forces may be provided to act on the sliding tube 30 to control its movement so that under normal conditions the sliding tube 30 will be in the downward position (FIG. 3) holding the flapper 26 away of and off of the valve seat 24 and the valve 10 will be opened. When abnormal conditions occur, the sliding tube 30 will be moved upwardly allowing the flapper 26 to close shutting off flow through the well tubing 14. Thus, actuating means such as a spring 40 may be provided acting on the sliding tube 30 to move the sliding tube 30 upwardly to allow the flapper 26 to close. The spring 40 acts between a shoulder 42 on the body 22 and the bottom of a piston 44 on the sliding tube 30 having seal ring 45 sealing against body 22.

The safety valve 10 may be controlled by the application or removal of fluid pressure through the control line 16 and a port 46 in the valve body 22 which opens into a chamber 48 and acts against the top of the piston 44. Thus if fluid pressure is supplied to the port 46 of sufficient magnitude, the piston 44 and the sliding tube 30 will be moved downwardly, forcing the flapper 26 off of the seat 24 and into full open position. If the pressure applied through the control line 16 and port 46 above the piston 44 is reduced sufficiently relative to the force provided by the spring 40, the piston 44 and the sliding tube 30 will move upwardly carrying the tube 30 above the valve seat 24 allowing the flapper 26 to swing in and close.

The above description of one type of safety valve 10 is conventional. However, it is to be noted that when the valve 10 is closed, the shut-in pressure in the well tubing below the valve 10 acts on the bottom of the valve flapper 26 to keep the flapper closed. When the valve is closed, the pressure above the valve may be considerably less than the pressure below the valve thereby creating a high differential pressure across the valve. While the valve may be opened when desired by pressurizing through the line 16 and against the top of the piston 44 and moving the tube 30 downwardly, a large differential pressure across the seat 24 and flapper 26 may damage the flapper 26 and seat 24 when opened. Of course, the pressure can be equalized by pumping down fluid through the tubing 14 above the valve 10, but this operation is not feasible in many installations.

The present invention is directed to providing equalizing means in the valve 10 which reduces the differential pressure across the valve seat 24 prior to opening the valve element 26. Referring now to FIGS. 2A and 2B, a passageway 50 is provided in the safety valve 10 and generally includes a first port 52, and equalizing valve generally indicated by the reference numeral 54, and a second port 56. The port 52 opens exteriorily of the valve body 22 and is in communication with the pressure in the well tubing 14 below the valve seat 24 thereby admitting tubing pressure into the passageway 50.

The equalizing valve 54 includes a valve seat 58 connected to the valve body 22, a primary valve element including a soft resilient seal 60 connected to the sliding tube 30 and a secondary metallic valve element 62 which may provide a metal-to-metal seal with the seat 58. It is to be noted that the soft L-shaped seal 60 is replaceable and seals all around the tube 30 as well as on the seat 58. As noted in FIG. 2B, when the safety valve 10 is closed with the flapper 26 seated on the valve seat 24, the sliding tube 30 is in its upward position and the equalizing valve 54 is closed.

When the safety valve 10 is closed, it is noted that the lower end 31 of the sliding tube 30 is positioned a slight distance above the valve element 26. Therefore, when the sliding tube 30 is actuated to open the safety valve 10, the sliding tube 30 moves downwardly and first opens the equalizing valve 54 allowing the high pressure well pressure from the tubing 14 below the safety valve 10 to pass through the passageway 50 through port 52, through the equalizing valve 54, and through the port 56 and into the bore 13 of the safety valve 10 above the valve seat 24. The differential pressure across the valve seat 24 is thus reduced prior to actuation and opening of the valve element 26.

Referring to FIGS. 2A and 2B, it is to be noted that the high pressure in the well tubing 14 beneath the safety valve 10, while the safety valve and equalizing port 54 are closed, acts on the sliding tube 30 to keep the safety valve 10 in the closed position. That is, the pressure in the port 52 and passageway 50 acts upwardly on the bottom of the piston 44 and downwardly on the portion of the resilient valve element 60 that is exposed to the pressure in the passageway 50 above the equalizing valve 54. Since the area of the bottom of the piston 44 is greater than the area of the valve element 60 exposed to the tubing pressure, there is a greater force acting on the tube 30 to keep it in the upward position thereby keeping the equalizing valve 54 closed.

However, once the sliding tube 30 is moved downwardly by applying pressure in the control line 16, the equalizing valve 54 is opened allowing the high pressure in the port 52 to flow through the passageway 50 and past the equalizing valve 54. In order to prevent the sliding tube 30 from moving downwardly, after the equalizing valve 54 is opened, with a snap action and damaging the flapper 26, the port 56 is sized smaller than the port 52 thereby providing a restriction in the passageway 50 dampening the downward movement of the sliding tube 30.

Therefore, the equalizing means of the present invention is closed when the safety valve 10 is closed and opens prior to the opening of the safety valve to equalize the pressure across the valve seat 24. The equalizing means also acts on the movable sliding tube 30 to maintain tube 30 in its upward position and helps to hold the equalizing valve 54 in the closed position. The equalizing means also provides a dampening effect as the tube 30 is actuated downwardly to open the valve seat 24 to prevent damage to the valve element 26.

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. While a presently preferred embodiment of the invention is given for the purpose of disclosure, numerous changes in the details of construction and arrangement of parts may be made which will readily suggest themselves to those skilled in the art and which are encompassed within the spirit of the invention and the scope of the appended claims.

Claims

What is claimed is:

1. In a well safety valve for controlling fluid flow through a well tubing and having a housing, a first valve being movable between an open and closed position for controlling flow through the housing and tubing, a flow tube telescopically movable in the housing, said tube when in the downward position holds the valve in the open position and when in the upward position allows the valve to close, first actuation means acting on the tube for closing of said valve, second actuating means acting on the tube in a direction to open said valve, the improvement of equalizing means for reducing the pressure differential across said first valve while opening said first valve comprising,

an equalizing valve between the housing and the tube, said equalizing valve being closed when the tube moves to the upward position and opens as the tube moves to the downward position, said equalizing valve opening prior to the opening of the first valve,

a passageway in said safety valve through the equalizing valve for communicating pressure from below the first valve to a point inside said tubing above the first valve, said passageway including a first port in the housing upstream of the equalizing valve and in fluid communication with the tube whereby pressure in the passageway passes through the first port and acts on the tube in a direction to keep the tube upward when the equalizing valve is closed, said passageway including a second port in the tube downstream of the equalizing valve, said second port being smaller than the first port thereby dampening the movement of the tube as it moves downwardly to the open position.

2. In a well safety valve for controlling fluid flow through a well tubing and having a housing, a first valve being movable between an open and closed position for controlling flow through the housing and tubing, a flow tube telescopically movable in the housing, said tube when in the downward position holds the valve in the open position and when in the upward position allows the valve to close, first actuation means acting on the tube for closing said valve, second actuation means including a piston acting on the tube in a direction to open said valve, the improvement of equalizing means for reducing the pressure differential across said first valve while opening said first valve comprising,

a passageway in said safety valve in communication between a point upstream of said first valve and a point interiorly of the tube and downstream of said first valve,

an equalizing valve between the housing and the tube in said passageway, said equalizing valve being closed when the tube moves to an upward position and opens as the tube moves to the downward position, said equalizing valve opening prior to the opening of the first valve, and

said passageway upstream of the equalizing valve being in communication at all times with the piston whereby pressure in the passageway acts on the piston in a direction for moving and holding the equalizing valve in a closed position.

3. The apparatus of claim 2 including, a restriction in the passageway downstream of said piston for dampening the movement of the tube as the tube moves in a direction to open the first valve.

4. The apparatus of claim 3 wherein the restriction is positioned downstream of the equalizing valve.

5. In a well safety valve for controlling fluid flow through a well tubing and having a housing, a flapper valve being movable between an open and closed position for controlling flow through the housing and tubing, a flow tube telescopically movable in the housing, said tube when in the downward position holds the flapper valve in the open position and when in the upward position allows the flapper valve to closed, first actuation means acting on the tube for closing said valve, second action means including a piston on the tube exposed to fluid pressure in a conduit extending from the well surface and acting on the piston in a direction to open said valve, the improvement of equalizing means for reducing the pressure differential across said first valve while opening said first valve comprising,

a passageway in said safety valve in communication between a point upstream of said flapper valve and a point interiorly of the tube and downstream of the flapper valve,

an equalizing valve between the housing and the tube in said passageway, said equalizing valve being closed when the tube moves to an upward position and opens as the tube moves to a downward position, said equalizing valve opening prior to the opening of the flapper valve,

said passageway upstream of the equalizing valve being in communication at all times with the piston whereby pressure in the passageway acts on the piston in a direction for moving and holding the equalizing valve in a closed position, and

a restriction in the passageway downstream of said piston for dampening the movement of the tube as the tube moves in a direction to open the flapper valve.