Subsurface safety valve

[57] ABSTRACT

A subsurface safety valve for use in a well production tubing. A tubular valve housing has a valve seat formed on one end ahd an interior tubular sliding member. A valve element is located on the sliding member for engagement with the valve seat for valve closure and contains openings above the valve element to permit flow through the valve housing when the valve is open. Spring means is provided between the sliding member and the valve housing and means cooperate with the spring means to cause snap action positive closure of the valve element on the valve seat. The spring means is arranged so that large flow areas are provided where the valve closure is made. The valve seat (or the valve element) is a resilient member and forms a resilient seal with the valve element (or valve seat) which resiliency permits the valve closure to be made on a surface which may be irregularly eroded.

Claims, 6 Drawing Figures

Primary Examiner—James A. Leppink Attorney, Agent, or Firm—John S. Schneider

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PATENTEDJUN 17 ws

3.889,751

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3,889,751

SUBSURFACE SAFETY VALVE

BACKGROUND OF THE INVENTION

The present invention concerns a subsurface safety valve for controlling the flow of well fluids, particularly oil and/or gas, produced from subsurface formations. The safety valve may be wireline retrievable or run as an integral part of the tubing string.

A conventional spring loaded valve as it closes continues biasing its spring to a maximum which occurs when the valve is closed. Near equilibrium conditions of opposing velocity force and spring force cause chatter and/or flutter between open and closed positions. Flow through a partially closed valve will greatly accelerate the erosion on the valve seat and seal.

The valve of the present invention overcomes those objectionable features in conventional valves by providing means to allow adequate initial loading (high velocity) yet assuring complete closure when design velocity has been reached.

The principal advantages of the safety valve of the invention over prior art valves are (1) large flow areas are provided where the valve closure is made, (2) resilient seals are used so that a full closure can be made on a surface which may be irregularly eroded and (3) high initial loading, snap action positive closure is provided.

The ball and spring arrangement illustrated herein with respect to a sliding tubular type valve is also applicable to ball, flapper, or any type velocity actuated valve.

SUMMARY OF THE INVENTION

Briefly, the apparatus of the invention comprises a subsurface safety valve for use in controlling flow of well fluids through well tubing or pipe and includes a valve housing connected to the well pipe. The valve housing has a valve seat formed on its lower end. An interior tubular sliding member is connected to the valve housing and a valve element is located on the sliding member for engagement with the valve seat for valve closure. The sliding member also contains openings above the valve element to permit flow through the valve housing when the valve is open. Spring means are arranged between the sliding member and the valve housing and means cooperate with the spring means to cause snap action positive closure of the valve element on the valve seat. The valve seat or valve element is preferably formed of resilient material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. I illustrates one embodiment of the safety valve of the invention in open position;

FIG. 2 illustrates the safety valve of FIG. 1 in closed position;

FIG. 3 illustrates another embodiment of the safety valve of the invention in open position;

FIG. 4 illustrates the safety valve of FIG. 3 in closed position;

FIG. 5 illustrates a modified valve seat-valve element arrangement for use with either of the embodiments of the invention shown in FIGS. 1 to 4; and

FIG. 6 shows a further modification of the closure elements which is usable with either of the embodiments of the invention shown in FIGS. 1 to 4.

DETAILED DESCRIPTION OF THE INVENTION

There is shown in FIGS. 1 and 2 a stationary tubular valve housing member 10 which is connected to a well pipe or tubing string, not shown. An interior tubular sliding member 11 provided with a valve element 12 on its lower end and a series of openings 13 above valve element 12 is arranged for movement within housing 10. A chamber 14 is formed between housing 10 and sliding member 11 in which are arranged spaced apart springs IS and 16. A shoulder 17 on the outer wall of sliding member 11 forms a lower stop for and confines spring 15 between it and an upper wall 18 of housing 10. Another outer shoulder 19 on the outer wall of sliding member 11 forms a lower stop for sliding member 11 on a lower shoulder 20 of housing 10 and also provides a lower stop for and confines spring 16 between it and a ball housing 21 positioned about sliding member 11. Ball housing 21 contains a series of slots 22 in each of which is arranged a ball 23. A groove 24 is formed on the inner wall of housing 10 and a groove 25 is formed on the outer wall of sliding member 11. The upper inner wall of sliding member 11 forms an orifice as at 26. A shoulder 27 is formed on the inner wall of housing 10 and functions as a stop for the upper end 28 of sliding member 11. A seal 29 is arranged on the upper outer wall of sliding member 11 to seal off the space between the inner wall of housing 10 and the outer wall of sliding member 11. The lower inner wall of housing 10 contains a seal 30 for sealing off the space between the lower inner wall of housing 10 and the lower outer wall of sliding member 11. The lower end of housing 10 contains a valve seat 31 formed of resilient material to effect a resilient seal with valve element 12.

OPERATION

Springs 15 and 16 urge slidable member 11 downwardly to maintain openings 13 below the lower end of valve seat 31 during normal flow upwardly through slidable member 11 and housing 10, as indicated by the arrowed lines. Upward movement of inner sliding member 11 against the resistance of springs 15 and 16 is produced by differential· pressure across orifice 26. When the design flow velocity has been reached sliding member 11 is retracted within housing 10 until the upper end 28 of sliding member 11 reaches stop shoulder 27 as shown in FIG. 2. Valve element 12 which engages resilient member 31 to form a seal, as shown, may be a tapered, erosion resistent material such as tungsten carbide and it enlarges valve seat 31 slightly to cause a seal when it is withdrawn into resilient valve seat 31. Snap action closure of valve element 12 into valve seat 31 occurs as follows. When sliding member 11 moves upward springs 15 and 16 are compressed simultaneously to provide a dual load on these two springs. When groove 25 on sliding member 11 passes balls 23 they retract from groove 24 and engage groove 25 and sliding member 11 together with ball housing 21 and balls 23 are then free to move upwardly. Such removal of the bias force of spring 16 against the member 11 causes spring 15 to be the only resistant force to the upward movement of the sliding member which allows the minimum resistance until the upper end 28 of sliding member 11 reaches stop 27. The entire section of the chamber containing springs 15 and 16 is kept free from sand by seals 29 and 30. The chamber 14 may be

3,889,751 filled with oil for free operation of the moving parts since there is no volume chahge in the chamber when the valve is opened or closed. To open the valve, pressure is applied from the surface until such pressure equalizes the pressure below the valve at which time spring 15 will displace sliding member 11 into the open position and return groove 25 and balls 23 to their original positions.

A modified subsurface safety valve is shown in FIGS. 3 and 4. A valve housing 50, connected to a well tubing string not shown, is provided with a resilient valve seat 51 and is formed with an inner extending shoulder 52 and upper and lower grooves 53 and 54, respectively. An inner sliding member 61 having a plurality of slots 62 adjacent the lower end of sliding member 61 above a valve element 63 is arranged for sliding movement within housing 50. The inner wall of sliding member 61 is formed with a flow orifice 64 and the uppermost end shoulder 65 of member 61 provides a stop for the upward movement of member 61 when it abuts stop shoulder 66 formed on the inner wall of valve housing 50. A space or chamber 67 is formed between the outer wall of sliding member 61 and the inner wall of valve housing. 50. A lower seal 55 on the inner wall of valve housing 50 seals off the lower end of chamber 67 and a seal 68 formed on the inner wall of member 61 seals off the upper end of chamber 67. An upper ball housing 69 is attached by groove 57 to member 61 above shoulder 52 in chamber 67 and a lower ball housing 70 is attached through groove 58 to sliding member 61 below shoulder 52 in chamber 67. An upper spring 71 is formed in chamber 67 above shoulder 52 and is confined between the upper side of ball housing 69 and a shoulder 73 formed on valve housing 50. A lower spring 72 is formed in chamber 67 and is confined between the upper side of ball housing 70 and shoulder 52.

As in the embodiment of FIGS. 1 and 2 upward movement of sliding mefhber 61 against the resistance of springs 71 and 72 is produced by differential pressure across flow orifice 64 when the design velocity has been reached. Fluid flow enters sliding member 61 and valve housing 50 through slots or openings 62, as indicated by the arrowed lines. When the design velocity has been reached sliding member 61 is retracted within valve housing 50 until the upper end 65 of sliding member 61 reaches stop shoulder 66 as shown in FIG. 4. Resilient valve seat 51 and valve element 63 are the same as in the embodiment of FIGS. 1 and 2. Snap action closure of the valve is provided as follows. Both springs 71 and 72 are initially compressed by upward movement of sliding member 61 together with the attached ball housings 69 and 70. The release recesses or grooves 53 and 54 are in the inner wall of housing 50. When the balls 75 and 76 are opposite recesses 53 and 54, respectively, sliding member 61 is released from spring compression and is free to move rapidly to the closed position of the valve shown in FIG. 4 to provide a snap action closure of the valve.

The closure may be modified as shown in FIG. 5. In the arrangement of FIG. 5 valve seat 80 is the metallic section which may be, as the valve element of the other embodiments, made of erosion resistant hard metal. The valve element 81 is formed of resilient material. A plug 82 holds resilient valve element seal 81 in place to prevent it from being washed out by the fluid stream passing by it as indicated by the arrowed line passing through slots 83 in sliding member 84. Metallic seat section 80 forms a seal to prevent flow through openings 83 when resilient valve element member 81 moves upwardly and seals against the lower edge 80 of valve housing 86;

A still further embodiment of the closure is shown in FIG. 6. A resilient valve seat 90 is connected to the lower end of a valve housing 91. An inner sliding member 92 contains a tapered valve element 93 at its lower end below slots or openings 94. A space or chamber 95 is formed between the lower end of housing 91 and sliding member 92. A sleeve 96 extends from chamber 95 to the lower end of resilient valve seat 90. A spring 97 in chamber 95 biases sleeve 96 downwardly.

A shoulder 98 formed on the lower end of sliding member 92 pushes sleeve 96 upwardly against the bias of spring 97 when sliding member 92 moves upwardly to closure position of the valve to permit valve element 93 to seal with the resilient surface of valve seat 90. Thus, as sliding member 92 is retracted within housing 91 shoulder 98 engages the lower end of sleeve 96 compressing it against spring 97 and uncovering the inner portion of resilient valve seat 90. The seal on erosion resistant material is provided in this manner.

The dual spring, single ball housing arrangement of the embodiment of FIGS. 1 and 2 and the dual spring, dual ball housing arrangement of the embodiment of FIGS. 3 and 4 are preferred arrangements. However, the invention contemplates using additional spring and ball housing arrangements in either of the embodiments.

Changes and modifications may be made in the illustrative embodiments of the invention shown and described herein without departing from the scope of the invention as defined in the appended claims.