Well Tools

Abstract

A well tool in the form of a flapper-type safety valve for use in a well bore to provide flow control in the well bore operable from the surface. The valve is particularly characterized by a flow-cut protected equalizing valve assembly for reducing the pressure differential across the flapper valve preliminary to opening the valve. The safety valve includes a housing, a flapper-type valve at the lower end of the housing to control flow into the housing, a valve operator tube positioned for longitudinal movement in the housing for opening the flapper valve responsive to a controlled pressure from the surface, a piston on the valve tube, an annular chamber around the piston communicatable to the surface for applying a fluid pressure from the surface to the piston to bias the piston and valve tube downwardly, a spring between the valve tubing and the housing biasing the valve tubing upwardly, and an equalizing valve assembly for equalizing the pressure between the interior and exterior of the housing on opposite sides of the flapper valve preliminary to opening the flapper valve. The equalizing valve, which is shown in two forms, includes a first bubble tight valve having a resilient seal and a second valve using a metal-to-metal seal. The equalizing valve assembly is arranged to open and close in sequences which protect the resilient seal against flow cutting.

Description

This invention relates to well tools and more particularly relates to a downhole type safety valve for use in a well bore.

Downhole safety valves are common well tools used for the control of the flow of well fluids such as oil and gas so that hazardous conditions may be minimized at the surface by closing the valves to shut-in wells below the surface. Such valves may be operable responsive to flow conditions at the valve or may be remotely controlled from the surface responsive to various desired surface conditions, including such factors as temperature, pressure changes due to ruptured lines, and the like. The present invention is particularly concerned with valves which are remotely controlled from the surface. Where such valves are of the flapper type as in the present invention, the flapper valve element normally opens downwardly so that when closed a substantial pressure differential may exist across the valve element requiring a large downward force on the valve to open it unless some pressure equalization is effected. In equalizing the pressure between the interior and exterior of a valve under pressure differential conditions of large magnitude, fluid flow can occur which is damaging to the equalizing valve means used unless features are employed which minimize the abrasive effects of the fluid flow. At least one available type of flapper valve with equalizing means is known. It does not include a protective feature which reduces the effects of flow cutting on the valve member during the pressure equalization.

It is an object of the invention to provide a new and improved downhole safety valve for wells.

It is a particularly important object of the invention to provide a downhole safety valve of the flapper type which includes an equalization valve assembly having means for minimizing flow cutting of the resilient seal in the assembly.

It is another object of the invention to provide a downhole safety valve having pressure equalization means which includes a metal-to-metal seal and a separate resilient seal for effecting a bubble tight sealed relationship at the equalization valve means.

It is another object of the invention to provide one form of downhole safety valve which includes a first spring means biasing the valve closed and a second spring means biasing the flapper valve and one valve of the pressure equalizing valve assembly closed.

It is another object of the invention to provide a downhole safety valve of the flapper type which uses a valve operator tube provided with a piston portion exposed to the pressure of a control fluid variable from the surface for selectively operating the valve responsive to predetermined surface conditions.

It is another object of the invention to provide another form of flapper-type safety valve using a single spring to bias the flapper element closed and another spring which only biases one of the valves of the equalizing valve assembly closed.

In accordance with the invention, there is provided a downhole safety valve for use in a well bore having a housing connectible into a tubing string or with a locking mandrel for use in a landing nipple in a well bore, a flapper valve at the lower end of the housing for controlling fluid entry into the housing, a valve operating tube longitudinally movable in the housing and having a piston portion exposed to an annular space in the housing around the operator tube communicating with a fluid pressure source for supplying a fluid pressure to bias the operator tube downwardly for selectively opening and closing the flapper valve from the surface, and a pressure equalizing valve assembly associated with the housing and valve operator tube for equalizing the pressure across the flapper valve preliminary to opening the valve to prevent flapper valve operation against a full well pressure differential across the valve.

The foregoing objects and advantages together with the specific details of preferred embodiments of a safety valve constructed in accordance with the invention will be understood from the following detailed description taken in conjunction with the accompanying drawings wherein:

FIGS. 1A through 1D taken together form a longitudinal view in section and elevation of a preferred form of flapper-type safety valve including the features of the invention and showing the valve closed;

FIG. 2 is a fragmentary view in section and elevation of the valve of FIGS. 1A-1D showing particularly the pressure equalizing valve assembly at an intermediate stage in valve operation;

FIGS. 3A-3C taken together form a longitudinal view in section and elevation showing the flapper valve open;

FIG. 4 is a view in section taken along the lines 4--4 of FIG. 1C;

FIG. 5A is a fragmentary view in section and elevation of an alternate form of pressure equalizing valve assembly and showing the valve assembly closed;

FIG. 5B is a fragmentary view in section and elevation showing the equalizing valve assembly of FIG. 5A open.

Referring to the FIGS. 1A-1D, a flapper-type downhole safety valve 10 embodying the features of the invention includes a valve housing 11 having a central bore 12, a flapper valve 13 at the lower end of the housing, a valve operator tube 14 including an operator piston 15, and a pressure equalizing valve assembly 20. The flapper valve is opened and closed by the operator tube 14 which is movable longitudinally responsive to fluid pressure applied from the surface to the piston 15. The pressure equalizing valve assembly 20 relieves the pressure differential across the flapper valve preliminary to opening the valve.

The valve housing 11 includes a top sub 21 which is internally threaded at 22 for connection with a tubing string extending to the surface end of a well bore in which the valve is installed on a locking mandrel for supporting the valve in a landing nipple as represented by the reference numeral 23. The top sub is internally threaded along a lower portion 24 of reduced wall thickness which is secured on an upper external threaded end portion 25 of a packing mandrel section 30. The top sub 21 is further reduced in wall thickness along a lower end portion 32 which is provided with an internally threaded side port 33 located between the upper and lower internal ring seals 34 and 35 disposed within internal annular recesses above and below the side port. The seals 34 and 35 seal with the outer wall surface of the packing mandrel which is provided with a side port 40 located between the seals 34 and 35 communicating with the side port 33. The side port 33 may be connected with a control fluid line to the surface or may communicate directly to an annular space within a well bore such as within a landing nipple which is supplied with a control fluid for operating the safety valve. The packing mandrel section 30 has an internal flange 41 provided with an internal annular recess 42 in which a ring seal 43 is disposed to seal between the packing mandrel and the outer surface of the valve operator tube 14 defining the upper end of a control fluid annulus 44 between the packing mandrel and the valve operator tube below the seal 43. The packing mandrel section is enlarged at 45 providing an upwardly spacing stop shoulder 50 for supporting the lower end of an annular packing assembly 51 which is confined between the lower end face 52 of the top sub and the packing mandrel shoulder 50. In the particular form of the safety valve 10 illustrated, the packing assembly 51 seals with the inner wall surface of a landing nipple in which the safety valve is supported from a suitable standard locking device, not shown, which includes a similar annular packing assembly for sealing with the landing nipple wall above the side port 33. Control fluid communicated to the landing nipple will be confined within an annular space around the valve above the packing assembly 51 on the valve housing and below the packing assembly of the locking device so that the control fluid is directed to the side port 33 for operating the safety valve from the surface. As shown in FIG. 1B, the enlarged portion 45 of the packing mandrel section has an internally threaded lower end portion 53 which is secured on the upper threaded end portion 54 of a housing adapter sub 55.

The flapper valve operator tube 14 comprises an upper tubular section 60 which is enlarged and internally threaded along a lower end portion 61 defining the operator piston 15 provided with an external annular recess 62 carrying an external ring seal 63 to seal within the valve housing packing mandrel section 45 around the operator tube piston portion. The seal 63 is the lower end of the control fluid annulus 44. The valve operator tube section 60 is secured along the lower end portion 61 with a tubular shaped prong section 64 which comprises the major portion of the operator tube extending downwardly to open the flapper valve. The piston portion 15 has an internal recess 65 which holds a ring seal 66 to seal between the piston portion and the prong section 64. The valve housing packing mandrel section 45 and the prong section 64 are concentrically arranged in spaced relation defining a spring chamber 70 in which a biasing spring 71 is positioned confined between an upper end 72 of the sub 55 and a spring ring 73 on the upper end of the spring. The ring 73 bears against the lower end edge of the piston portion 15 of the valve operator tube so that the spring 71 biases the valve operator tube upwardly to the position of FIGS. 1A-1D at which the flapper valve is closed. A ring seal 74 in an external annular recess of the adapter sub 54 seals around the sub within the lower end portion of the packer mandrel 30 of the housing.

The adapter sub 55 has a side port 75 for admitting pressure to an annular space 80 within the adapter sub around the valve operator tube section 64 to equalize the pressure across the flapper valve when the equalizing valve assembly 20 is open. The adapter sub is reduced and externally threaded along the lower end portion 81 which is engaged in the upper end portion of a lower housing section 82. A ring seal 83 in an external annular recess at the upper end of the lower threaded end portion of the adapter sub seals around the adapter sub within the housing section 82.

The adapter sub 55 has an internal annular flange 84 which supports an internal annular resilient seal 85 within an internal recess of the flange to effect a bubble tight seal with an external annular flange 90 on the valve operator tube section 64 when the operator tube is in the valve-closed position of FIGS. 1A-1D. The seal 85 and valve operator tube 90 comprise a first valve of the equalizing valve assembly 20. The lower end of the adapter sub has an internal downwardly and outwardly sloping valve seat surface 91 which is engageable by a similar downwardly and outwardly sloping valve seat 92 on a tubular valve member 93 forming the second valve of the equalizing valve assembly 20. The valve seats 91 and 92 are formed of a suitable metal alloy such as Colmonoy -5 providing a metal-to-metal seal. The valve member 93 includes an upwardly and inwardly tapered head portion 94 and a tubular skirt portion 95. The lower end of the head portion 94 defines an internal stop shoulder 100 which is engageable with the top surface of an external annular flange 101 on the valve operator tube section 64 spaced below the external flange 90 on the tube section. The flange 101 has an external annular recess provided with a ring seal 102 to seal around the flange with the internal wall surface of the skirt portion 95 of the valve member 93. The valve skirt 95 has an internal annular recess 103 in which three segments 104 of a split ring are retained by a stop ring 105 having a tubular body portion 110 and a lower flange portion 111. The stop ring 105 which fits into the lower end of the valve member skirt 95 to hold the three ring segments 104 in place within the recess 103 to provide an upwardly facing flange for the lower end of the valve operator tube flange 101 to engage so that when the valve operator tube moves downwardly the flange 101 contacts the ring segments 104 pulling the valve member 93 downwardly with the valve operator tube.

The concentric spaced relationship of the valve housing section 82 and the valve operator tube section 64 below the adapter sub 55 defines an annulus 112 for fluid flow to equalize the pressure across the flapper valve and to house the spring 113 confined between the stop ring flange 111 at the upper end of the spring and an internal upwardly facing annular shoulder 114 in the housing section 82 at the lower end of the spring. The spring 113 biases the valve member 93 upwardly to a sealed seated relationship against the seat 91 when the safety valve is fully closed as in FIG. 1C and provides an upwardly directed force against the valve operator tube and the valve member 93 when the flapper valve is open as represented by FIGS. 3B and 3C. The lower end portion of the valve operator tube probe section 64 has a side port 115 to provide communication from within the tube into the annulus 112 for pressure equalization. The valve housing section 82 has a lower end portion 120 provided with a first reduced bore portion 121 which is larger than the tube section 64 to permit communication into the operator tube side port 115 when the tube is at the position shown in FIG. 1D. The housing lower end portion 120 has a further reduced bore portion 122 which is sized to provide a slip fit relationship with the valve operator tube so that the tube may move down longitudinally for operating the flapper valve.

The lower end portion 120 of the valve housing section 82 is externally threaded at 123 and connected into a bottom section 124 which supports and encloses the flapper valve 13. The flapper valve includes a valve plate 125 formed integral with a hinge arm 130 which is pivotally mounted on a lateral hinge pin 131 secured in a pair of aligned bores 132 through opposite wall portions of the valve housing section 124 near one side and aligned perpendicular to the longitudinal axis of the housing section. The outer opposite ends of the hinge pin are ground to the curvature of the outer cylindrical surface of the valve housing 124 to provide a smooth outer surface along the housing at the pin locations. The housing section 124 has a longitudinal slot 133 aligned between the two bores 132 to provide space for the hinge arm 130 and to allow the hinge arm to swing between the positions of FIG. 1D and FIG. 3C for opening and closing the flapper valve. A spring 134 is wound about the hinge pin with one end of the spring engaged with the flapper valve plate 125 and the other end extending along the inner face of the valve housing below the slot 133 as seen in FIG. 1D to bias the flapper valve plate to the closed position of FIG. 1D. The flapper valve plate has an upwardly and inwardly tapered annular seat surface 135 which is engageable with a downwardly and outwardly tapered annular valve seat 140 of a hardened metal alloy secured at the lower end of the housing section 82. The lower end portion 141 of the housing section 124 is increased in wall thickness providing a reduced downwardly flared bore 142 and an upwardly facing tapered stop shoulder 143 engageable by the lower end edge 64a of the valve operator tube section 64 to limit the downward movement of the operator tube after flapper valve is opened as shown in FIG. 3C.

The safety valve 10 in the particular form illustrated may be installed in a well bore in a landing nipple having a side port connected with a control line extending from the surface. The safety valve is supported from a suitable locking mandrel 23, not shown, which carries a packing assembly similar to the packing assembly 51 for cooperating with the packing assembly 51 to seal off an annular space in the landing nipple to direct the control fluid to side port 33 of the safety valve. Installations of this type are shown, for example, at Page 3501 of the Composite Catalog of Oil Field Equipment and Services, 1972-73 Edition, published by WORLD OIL, Houston, Texas. Locking mandrels of the type which may be used are shown at Page 3458 of the Composite Catalog of Oil Field Equipment and Services, supra. Additionally, a landing nipple arrangement which may be employed is illustrated in FIGS. 13 and 14 of U. S. Pat. No. 3,292,706 issued Dec. 20, 1966 to G. C. Grimmer, et al and assigned to Otis Engineering Corporation.

With the safety valve installed in a well bore and prior to the application of control fluid pressure through the side port 33 in the valve, the valve is closed with the various component parts of the valve being positioned as illustrated in FIGS. 1A-1D. The springs 71 and 113 are each expanded to the maximum length permitted by the relation of the various parts of the valve holding operator tube at an upper end position and the equalizing valve assembly closed. The lower end of the tube 14, as seen in FIG. 1D, is spaced above the flapper valve plate 125 of the valve assembly 13. Both valves of the equalizing valve assembly 20 are closed as seen in FIG. 1C. The valve seat 92 on the valve member 93 is engaged with the valve seat 91 within the lower end of the adapter sub 55. Since the valve member 93 is limited from any further upward movement and the top face of the flange 101 on the valve operating tube section 64 is engaging the downwardly facing shoulder 100 within the valve member 93, the valve operator tube 14 cannot move further upwardly. At this longitudinal position on the valve operator tube, the vale flange 90 is aligned with and engages the ring seal 85 of the adapter sub thereby closing the first valve of the pressure equalizing valve assembly 20. The spring 134 together with any pressure differential that may exist across the flapper valve plate 125 holds the flapper valve tightly closed as shown in FIG. 1D. It will be recognized that the spring 71 bearing against the spring ring 73 at the lower end of the piston 15 on the valve operator tube 14 holds the operator tube at an upper end position limited by the engagement of the flange 101 with the internal shoulder surface 100 of the valve member 93. The force of the spring 113 bearing against the ring 105 engaging the lower end of the valve member 93 holds the valve member upwardly against the seat 91.

When the safety valve 10 is to be opened, the control fluid pressure as applied through side port 33 is increased so that the pressure within the annulus 44 between the seals 43 and 63 is raised. It is assumed for purposes of this discussion that a pressure differential exists across the flapper valve 13 so that effort to move the valve plate 125 downwardly is applied against well pressure. When the force of the control fluid pressure increase over the annular area on the piston and valve operator tube defined by the seals 62 and 43 exceeds upward forces of the spring 71 and the well pressure on the valve operator tube and piston as communicated into the safety valve housing through the side port 75, the valve operator tube 14 is moved downwardly. During the initial downward movement of the valve operator tube, the spring 71 is compressed and the flange 101 on the probe section moves downwardly away from the shoulder 100 within the valve member 93 leaving the valve member 93 in seated engagement with the valve seat 91. Because of the dual of the equalizing valve assembly and the proximity of valve function the seal 85 to the engaged valve seats 91 and 92, the fluid, if any, which may occur past the seal 85 when the flange 90 moves below the seal is considered negligible so that the seal is protected against flow cutting during equalization of pressures. FIG. 2 illustrates an intermediate stage in the opening of the valve showing the valve operator tube flange 90 disengaged from and below the seal 85 with the valve member 93, however, still closed. The valve operator tube continues downwardly with the lower end edge of the flange 101 engaging the split ring segments 104 to apply downward force to the valve member 93 which is thereafter carried downwardly by continued downward movement of the valve operator tube. When the flange 101 engages the split ring segments, the separation of the valve seats 91 and 92 begins.

As soon as the valve member 93 moves downwardly off the seat 92, the well pressure as applied to the safety valve housing through the port 75 is communicated downwardly between the seats 91 and 92, around the valve member 93, and through the annulus 112 to the side port 115 to initiate pressure equalization between the well pressure exterior of the safety valve housing and the bore through the safety valve above the flapper valve 13. The lag between the opening of the second valve of the equalization valve assembly 20 by downward movement of the valve member 93 and the time when the lower end 64a of the valve operator tube probe section 64 engages the flapper valve is scaled to provide adequate time for substantial pressure equalization across the flapper valve so that essentially the only resistence to opening the flapper valve is provided by the spring 134. As the valve operator tube continues downwardly, the lower end edge 64a of the operator tube probe section engages the top face of the flapper valve plate 125 to pivot the valve plate downwardly on the pin 131. The concave configuration of the top surface of the flapper valve plate is designed to cause the lower end edge 64a of the valve operating tube to first engage the flapper valve plate along the opposite side of the plate from the hinge pin 131 so that maximum leverage is obtained by the downward force of the tube on the valve plate to start the opening of the valve. The valve operator tube continues downward movement until the lower end edge 64a of the tube engages the stop shoulder 143 within the valve housing bottom section 124 at which time the flapper valve is fully open. FIGS. 3A, 3B, and 3C show the relative positions of the valve parts when the valve is open. It will be noted in FIG. 3C that the flapper valve plate 125 swings fully downwardly and outwardly to a vertical position into an annular space defined between the tube section 64 and the housing section wall. It will be noted in FIG. 3B that the flange 90 and the valve member 93 of the equalizing valve assembly are substantially below the seal 85 and the seat 91. It will also be noted that the seal 85 engages the valve operator tube along a wall portion which would appear to form a seal between the housing and the operator tube. In practice the operator tube at this location along the tube is only about 0.006 to 0.010 inches larger than the outside diameter of the flange 90, so some sealing may occur with the seal 85, though it will be recognized that sealing is not essential when the valve is fully open as there is no pressure differential across the seal 85 and thus no tendency toward a fluid flow along the seal which might cut it. Well pressure is applied laterally inwardly into the housing in the port 74, and also well pressure exists in the valve upwardly around the valve operator tube and the valve member 93 to below the seal 85. It will be recognized that from the time the flange 101 engaged the ring segments 104 to move the valve member 93 downwardly, the spring 113 was compressed until the valve operator tube reached the lower end of the stroke as represented in FIG. 3C. Thus, with the valve fully open, the control fluid pressure applied through the side port 33 into the annulus must supply sufficient force on the piston 15 to overcome the upward forces of the springs 71 and 113 and well pressure on the piston 15. The well pressure acts upwardly on the valve operator tube assembly over the annular area defined by the lines of sealing engagement of the seals 43 and 63. The safety valve remains open so long as the control fluid pressure is maintained at a sufficiently high level. The control fluid pressure will be maintained so long as well production is desired. The control fluid pressure may be reduced to close the safety valve at any time the well is to be shut in. Also the control fluid pressure may be supplied by surface means designed to respond to such conditions as fire, line rupture, and the like to shut in the well under emergency conditions.

The safety valve 10 is closed by relieving the control fluid pressure applied through the side port 33. When the force upon the piston 15 from the control fluid pressure decreases below a value which exceeds the force of the springs 71 and 113 together with the well pressure, the valve operator tube 14 is lifted upwardly. The operator tube is raised by forces from both the springs and the well pressure until the tube and the associated parts of the valve including those forming the pressure equalizing valve means 20 are returned to the positions represented in FIGS. 1A-1D. At the lower end position of the operator tube, both the springs 71 and 113 bias the tube upwardly. Both springs lift the tube from the position of FIGS. 3A-3C until the valve member 93 is closed as in FIG. 2. Thereafter, the spring 71 only lifts the operator tube. As the operator tube moves upwardly, the valve seat 92 on the valve member 93 engages the seat 91 in the valve housing before the operator tube flange 90 contacts the seal 85. When the valve member 93 reaches the upper end position shown in FIG. 2, the valve operator tube then continues upward movement until the flange 101 engages the downwardly facing stop shoulder 100 within the valve member 93 at which time the flange 90 has moved into a seated relationship within the seal 85. From the time that the seats 91 and 92 of the second valve of the pressure equalization assembly engage shutting off flow through the valve assembly, there is no fluid flow to cut the seal 85 during the step of moving the sealing flange 90 on the valve tube into engagement with the seal 85. As soon as the lower end edge 64a of the valve operator tube probe section moves above the seat 140, FIG. 1D, the spring 134 swings the flapper valve plate 125 on the pin 131 upwardly toward the closed position at which the valve plate is engaged with the seat 140 and is fully closed. It will be evident that if there is any flow in the wall, as soon as the flapper valve begins to restrict fluid entry into the safety valve developing a pressure differential across the valve, the valve plate will be rapidly closed by the fluid flow into the valve bore. The valve will remain closed so long as the control fluid pressure is below the level sufficient to overcome the springs and the well pressure.

An alternate form 20A of the pressure equalizing valve assembly is illustrated in FIGS. 5A and 5B. The valve assembly 20A discharges the same pressure equalizing functions as the valve assembly 20 without the use of the large spring 113. With the exception of the modification and elimination of parts required for the specific structure of the valve assembly 20A, a safety valve using such valve assembly is otherwise identical to the valve 10. Thus, the reference numerals used in describing the structure of FIGS. 5A and 5B shall be the same as those used in conjunction with the other figures with the exception that modified valve parts shall be referred to with the suffix A. The valve operator tube used with the modified equalization valve assembly 20A includes a tube probe section 64A having an external annular elongated flange 101A. Formed on the tubular section at the upper end of the flange 101A is an enlarged tubular portion 150 which functions as a spring guide or centralizer. The upper end of the tubular portion 150 also serves as an upper end stop for the operator tube engaging the bottom face of the valve member head properly positioning the flange 90A aligned with the seal 85. A valve member 93A which is functionally identical to the valve member 93 is disposed around the flange 101A within the valve housing section 82 for movement between open and closed positions as shown in FIGS. 5A and 5B, respectively. The valve member 93A has a head portion 94A to which is secured the annular alloy seat 92 which is engageable with the seat 91 within the valve housing. The valve member has a skirt portion 95A to which are secured a plurality of circumferentially spaced dependent or downwardly extending L-shaped collet fingers 151 for retaining the valve member on the flange 101A and permitting the flange to pull the valve member downwardly. A spring 152 is confined between the internal downwardly facing shoulder 100A of the valve member head and the upper end face of the operator tube flange 101A for biasing the valve member 93A upwardly on the operator tube section thereby performing the same function relative to the valve member as the spring 113.

In operation the equalizing valve assembly 20A functions to equalize the pressure differential across the flapper valve 13 when the valve is closed preliminary to opening the flapper valve in the manner previously described. As the valve operator tube section 64A moves downwardly in the process of opening the flapper valve, the external flange 90A moves out of engagement with and below the seal 85 the distance permitted by the lag or spacing between the lower end edge of the flange 101A and the lower ends of the collet fingers 151. During the initial travel of the operator tube section 64A, prior to the engagement of the lower end edge of the flange 101A with the lower ends of the collet fingers 151, the spring 152 biases the valve member 93A upwardly holding the valve member seat 92 engaged with the valve housing seat 91. As soon as the downwardly moving operator tube engages the collet fingers 151 at the time of contact of the lower end edge of the flange 101A with the lower ends of the collet fingers, the downwardly moving tube pulls the valve member 93A downwardly with the tube to open the second valve of the valve equalizing assembly as the valve seat 92 moves downwardly from the valve seat 91. The valve member 93A is carried downwardly by the operator tube as the operator tube moves to the lower end position of FIG. 5B for fully opening the flapper valve.

The valve member 93A remains in the position of FIG. 5B until closure of the flapper valve. when the valve operator tube moves back upwardly to close the flapper valve, the spring 152 retains the valve member 93A at the upper end position of FIG. 5B until the seat 92 on the valve member engages the valve housing seat 91 which is substantially in advance of the movement of the valve tube flange 90A into engagement with the ring seal 85. With the valve member 93A closed, the valve operator tube continues moving upwardly compressing the spring 152 until the upper limit of travel of the operator tube is reached at which position the operator tube flange 90A is engaged with the ring seal 85 thereby fully reclosing both valve portions of the equalizing valve assembly. The engagement of the upper end of the flange portion 150 with the bottom face of the valve member head 94A stops the upward movement of the operator tube and correctly positions the flange 90A aligned with the seal 85.

While the safety valve 10 has been discussed in terms of use in a landing nipple in a well bore supported from a locking mandrel engaged with locking recesses of the landing nipple, it will be understood that the safety valve is also usuable as an integral part of a tubing string to which a control line is run from the surface. In this form, the safety valve may be referred to as a "tubing retrievable" type safety valve connected in the general arrangement illustrated at Page 3503 of the Composite Catalog of Well Field Equipment and Services, supra. In this arrangement the safety valve functions identically as previously described with the control line extending from the surface connecting into the side port 33 through a suitable fitting of the type illustrated at the reference.

It will be seen that a new and an improved form of flapper-type downhole safety valve has been described and illustrated. It will be further seen that the safety valve includes a pressure equalizing valve assembly to reduce the pressure differential across the flapper valve element preliminary to opening the valve so that the valve is not opened against a full well pressure. The equalizing valve assembly essentially comprises two valves, one of which uses a metal-to-metal seal arrangement while the other includes a resilient member providing a bubble tight seal. In both forms of the equalizing valve assembly illustrated and described, the closing and opening of the two valves of the assembly during both the closing and opening of the safety valve occur in an order which essentially eliminates fluid flow across the resilient valve seal. Thus, during the opening of the safety valve the resilient valve opens first followed by the opening of the metal-to-metal valve. During the closing of the safety valve, the metal-to-metal valve closes first followed by the closing of the resilient valve. With this arrangement, there is no metering of fluid past the resilient seal so that the seal is protected from flow cutting.

Claims

What is claimed is:

1. A well tool for controlling fluid flow in a tubing string in a well bore comprising: a housing having a longitudinal bore therethrough for flow of fluids; a valve secured at the lower end of said housing for movement between open and closed positions for controlling the flow of fluids into said bore of said housing; a valve operator tube supported for longitudinal movement in said housing, a lower end of said operator tube being engageable with said valve for moving said valve from a closed to an open position responsive to downward movement of said operator tube; means associated with said operator tube for biasing said tube upwardly to an upper position at which said valve is closed; means for selectively urging said operator tube downwardly to a lower position for opening and holding said valve open; and means associated with said operator tube in said housing for equalizing the pressure across said valve when said valve is closed to reduce the force required for opening said valve including first and second equalizing valve means, said first and second equalizing valve means being opened and closed in a sequence adapted to prevent flow cutting of said first equalizing valve means.

2. A well tool in accordance with claim 1 wherein said second equalizing valve means opens after the opening of said first equalizing valve means during the opening of said valve and said second equalizing valve means closes in advance of the closing of said first equalizing valve means during the closing of said valve.

3. A well tool in accordance with claim 2 wherein said first equalizing valve means comprises an annular resilient ring seal disposed in an internal annular recess of said housing and an external annular flange on said operator tube engageable with said resilient seal when said tube is at a position at which said valve is closed and said second equalizing valve means includes an annular tapered valve seat within said housing around said operator tube between said first equalizing valve means and said valve and a sleeve member having an annular tapered seat engageable with said seat of said housing, means biasing said sleeve member toward said housing seat, and means on said operator tube for engaging and retracting said sleeve to open said second equalizing valve means by pulling said sleeve valve seat away from said housing valve seat after said first equalizing valve means is opened.

4. A well tool in accordance with claim 3 including a spring around said operator tube within said housing engaged at one end with a flange in said housing and at the other end with said sleeve member of said second equalizing valve means comprising said means for biasing said sleeve member toward said valve seat in said housing whereby said sleeve remains engaged with said seat until said flange on said valve operator tube is disengaged from said resilient seal during the opening of said valve and said sleeve member re-engages said valve seat in said housing in advance of the engagement of said valve operator tube flange with said resilient seal during the closing of said valve.

5. A well tool in accordance with claim 3 including a spring on said valve operator tube engaged between said sleeve member of said second equalizing valve means and said valve operator tube comprising said means for biasing said sleeve member toward said valve seat of said housing whereby said second equalizing valve means remains closed until said first equalizing valve means is opened and said second equalizing valve means closes in advance of the closing of said first equalizing valve means.

6. A well tool in accordance with claim 1 wherein: said means for urging said operator tube downwardly includes a piston on said valve operator tube, an annular control fluid chamber around said valve operator tube within said housing, said piston being movable in said control fluid chamber, and means for supplying a control fluid into said chamber for applying a control fluid pressure to said piston for moving said valve operator tube toward said valve to open said valve; and said means for equalizing the pressure across said valve when said valve is closed includes means defining a side port in said housing to communicate with a well bore around said well tool, means providing a port in said valve operator tube communicating with the bore of said well tool, means defining an annular flow space around said operator tube within said housing between said side port in said housing and said side port in said operator tube, said first and second equalizing valve means being positioned along said annular space between said side ports for controlling flow between said ports within said annular space to equalize the pressure between the bore of said well tool above said valve and a well bore around said well tool housing, said first and second equalizing valve means being operable responsive to longitudinal movement of said valve operator tube and including a resilient internal annular seal within an annular recess of said housing around said valve operator tube, an external annular tapered first flange on said valve operator tube engageable with said resilient seal when said flange is longitudinally aligned with said seal forming said first valve means, an internal annular tapered metal valve seat within said housing between said resilient seal and said valve, a valve sleeve member movably disposed on said operator tube within said annular space and having an annular tapered valve seat engageable with said housing valve seat forming said second equalizing valve means, a second external annular flange on said valve operator tube spaced from said first flange and movable within said valve sleeve member for actuating said valve sleeve member relative to said housing seat, said sleeve member having an internal annular operator shoulder facing said valve engageable by said second flange on said operator tube limiting movement of said operator tube away from said valve at a position to align said first flange within said resilient seal, said sleeve member having means providing internal operating surfaces facing away from said valve for engagement by said second flange on said operator tube to move said sleeve member toward said valve to open said second equalizing valve means, the distance between said operator shoulder of said member and said operator surfaces being greater than the length of said second flange on said second flange on said operator tube whereby said first equalizing valve means opens before said second flange engages said valve sleeve member to open said second equalizing valve means and a spring engaged with said valve sleeve member biasing said valve sleeve away from said valve toward said valve housing seat.

7. A well tool in accordance with claim 6 wherein said spring is confined between a shoulder in said housing facing away from said valve and the end of said valve sleeve member facing said valve.

8. A well tool in accordance with claim 6 wherein said valve sleeve member is provided with resilient collet fingers projecting toward the valve, said collet fingers having inwardly turned collet heads defining said internal operating shoulder in said valve sleeve member and a spring confined within said valve sleeve member around said valve operator tube between said flange on said operator tube and said operator shoulder in said valve sleeve member facing said valve providing means biasing said valve sleeve toward said housing seat on said valve operator tube.