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(11) | EP 0 055 183 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Pressure responsive valve seat apparatus |
| (57) In accordance with an illustrative embodiment of the present invention, a pressure
responsive valve seat assembly that is cooperable with a ball valve element to hold
pressure in either direction when the ball valve is closed includes a retainer ring
that is spring biased toward the valve element and which carries a valve seat ring,
and a floating piston that is sealingly slidable with respect to the retainer ring
and the valve housing, the various diameters of sealing engagement between the piston
and the housing and the retainer ring, and between the valve seat ring and the ball
element being sized and arranged such that a predominate fluid pressure either upstream
or downstream of the ball valve force the retainer ring against the ball valve to
prevent fluid leakage. |
FIELD OF THE INVENTION
[0001] This invention relates generally to full-bore ball valves that are used, for,example, to control the flow of well fluids during a drill stem test, and particularly to a new and improved ball valve seat and seal assembly of the type described that is constructed and arranged such that when the valve is closed it will hold a predominant fluid pressure acting from either above or below the ball element.
BACKGROUND OF THE INVENTION
[0002] A drill stem test of an earth formation that has been intersected by a well bore may be considered as a temporary completion of the well. A packer and a test valve are run into the well on a pipe string and the packer is set to isolate the interval to be tested from the hydrostatic head of the well fluids thereabove. The test valve then is opened and closed to alternately flow and shut in the well; while a pressure recorder is used to record pressure data as a function of time. From the pressure record various highly useful parameters such as permeablity and initial reservoir pressure can be determined.
[0003] It is fairly typical for the test valve to include a ball-type closure element to control formation fluid flow. A ball valve has the advantage as opposed to other types of closure elements such as a sliding sleeve valve or the like, of providing when open an unobstructed vertical passage through the test tool to enable high flow rates of formation fluids as well as the capability for conducting other well services such as pressure surveys and perforating without withdrawing the equipment from the well.
[0004] There is a need for the tester valve to hold without leaking predominant pressures that may be imposed thereon from both above and below. The valve must hold the greater pressure from below as the test tools are run into the well in order to maintain the pipe string initially as a low pressure region into which the well fluids can produce when the valve is opened. The valve also should have the capability for holding a greater pressure from above to enable pressure testing of the pipe string as it is being assembled at the surface and lowered into the well. A greater pressure from above also will be imposed when a fluid recovery in the pipe string is being reverse circulated therefrom during the final shut-in period. Of course, the leakage of such pressure will disturb or spoil the shut-in pressure measurements that are being recorded. Moreover, a predominant pressure may be applied to the test valve from above when using a tubing pressure operated reverse circulating valve of the type disclosed and claimed in Upchurch application Serial No. 253,786, assigned to the assignee of the present invention.
[0005] However, a ball valve closure has not been as effective as other types of closures in holding pressure from both directions because it is designed to close upwardly against a valve seat that surrounds the flow passage. Although pressure from below may tend to force the valve element against the seat and thus tighten the closure against leakage, it will be realized that pressure form above may have the opposite effect and tend to cause the ball element to leak.
[0006] Although various attempts have been made to provide a ball valve closure that will hold pressure from either direction, Applicant does not believe that such previous designs have been particularly adequate to accomplish the desired objective.
SUMMARY OF THE INVENTION
[0007] It is a general object of the present invention to provide a new and improved ball valve closure apparatus useful in drill stem testing or the like.
[0008] This and other objects are attained, in accordance with one aspect of the invention by valve apparatus adapted for use in a well bore, comprising: tubular housing means defining a flow passage; valve means rotatable about an axis that is transverse to said flow passage between open and closed positions; seat means surrounding said flow passage and having a seat surface and seal means coacting with said valve means in said closed position to block fluid flow through said flow passage; and pressure responsive means for forcing said seat surface against said valve means in response to a predominate pressure either upstream or downstream of said valve means.
BRIEF DESCRIPTION OF THE DRAWING
[0009] The present invention has other features and advantages which will become more clearly apparent in connection with the following detailed description of a preferred embodiment taken in conjunction with the appended drawing in which:
FIGURE 1 is a view partly in c:oss-section and partly in elevation of a ball valve arrangement utilizing the unique pressure responsive seat assembly that is constructed in accordance with the present invention; and
FIGURE 2 is an enlarged fragmentary cross-sectional view of the pressure responsive seat assembly of Figure 1.
DESCRIPTION OF A PREFERRED EMBODIMENT
[0010] Referring intially to Figure 1, an apparatus in which the present invention may be embodied, includes inner and outer tubular housings 9 and 10 which together constitute a valve body 11 having a flow passage 12 extending longitudinally therethrough. A seat assembly indicated generally at 13 is mounted within the body 11 and surrounds the flow passage 12 for cooperation with a ball valve element 14. The ball element 14 has a bore 15 extending therethrough and is mounted for rotation about an axis that is transverse to the flow passage 12 between a closed position where the bore is disposed at right angles to the flow passage and an open position where the bore of the ball is aligned with the flow passage. The ball element 14 can be mounted for rotation on suitable means such as trunions 16 that extend for opposite side walls 17 of the ball into circular recesses 18 that are formed in the walls of the body 11.
[0011] The ball element 14 can be rotated between its open and closed positions by any suitable means such as an actuator sleeve 20 which can rotate about the longitudinal axis of the body and which carries a ring 21 that is appropriately fixed to its upper end. The ring 21 has an inclined pin 22 that projects inwardly toward the center of the ball element 14. The pin 22 can have a roller 23 mounted thereon which engages within a rectangular slot 24 extending circumferentially of the ball in the outer periphery thereof. Thus arranged it will be recognized that the ball element can be rotated to the open position in response to the rotation of the sleeve 20 in one direction and to the closed position by rotation of the sleeve in the opposite direction. Of course, this particular means for rotating the ball is only one of a number of different structures that might be used and is described herein for purposes of illustration and not in a limitive sense.
[0012] The seat assembly 13 includes a retainer ring 25 that is provided with a spherical annular lower surface 26 which engages the outer periphery of the ball 14. A composite seal assembly 30 that engages the the outer peripheral wall of ball valve 14 may be located in a groove 31 that opens through the lower surface 26. The seal assembly 30 may be any suitable elastomer device for preventing fluid leakage when the valve is in the closed position, but preferably is constructed as disclosed and claimed in Meek application Serial No. 214,473, assigned to the assignee of the present invention. The retainer ring 25 is biased toward the ball element 14 by helical coil spring 32 that reacts between an upper end surface of the retainer ring 25 and a downwardly facing shoulder 34 on the housing 9.
[0013] As shown in enlarged detail in Figure 2, the retainer ring 25 has a reduced diameter upper portion 35 that provides an annular seal surface 36 whose diameter is denoted as A. The parts are sized and arranged such that the diameter A is smaller than the diameter of sealing engagement of the seal assembly 30 against the ball element 14, which is denoted as B. A piston ring 38 that is mounted between the upper portion 35 and the housing 11 is movable relatively along the housing between an upper position where the upper end of the ring 38 abuts a downwardly facing shoulder 39-on the housing, and a lower position where the lower end surface 40 thereof abuts against an upwardly facing shoulder 41 on the retainer ring 25. A seal 42 engages the upper portion of the retainer ring 25 on the diameter A, whereas another seal 43 engages the inner wall surface 44 of the housing 9 on having a seal diameter denoted as C. The seal diameter C is greater than the diameter B.
OPERATION
[0014] In operation the parts are assembled as shown in the drawings with the lower surface 26 of the retainer ring 13 and the composite seal assembly 30 engaging the outer surface of the ball element 14. In the case where the ball valve assembly as disclosed herein is to be used, for example, in a drill stem testing operation, the ball initially is in the closed position as the tools are being run into the well to test depth. The region of the flow passage 12 located above the ball element 14 is at atmospheric or other low pressure with respect to the region below the ball element, which normally will contain well fluids at hydrostatic pressure. The relatively high fluid pressure upstream or below the ball valve 14 will act via the annular clearance space 45 between the retainer ring 25 and the housing wall 39 on the lower face of the piston ring 38 and on the upwardly facing shoulder 41 of the retainer ring. The pressure causes the piston 25 to shift upwardly into engagement with the housing shoulder 39 to thereby transfer upward force cue to such pressure to the housing 11. The pressure also acts downwardly on the shoulder 41 over a transverse cross-sectional area that is defined by the difference in diameters of sealing engagement A and B as downward force on the retainer ring 25 to hold the same tightly seated against the outer periphery of the ball valve element 14. The downward force is aided by the bias force of the spring 32.
[0015] Conversely when the pressure of the well fluids in the flow passage 12 above the ball element 14 is greater than the pressure of well fluids in the flow passage therebelow, such pressure acts downwardly on the piston ring 38 over a transverse cross-sectional area defined by the difference in the diameters C and A to force the ring downwardly into engagement with the shoulder 41. The piston ring 38 transmits force due to such pressure to the retainer ring 45 to hold it in tight sealing engagement with the outer periphery of the ball element 14. Here again the downward force is assisted by the bias force of the spring 32. Thus it will be recognized that the pressure responsive valve seat assembly of the present invention is uniquely arranged to coact with the ball valve element 14 to prevent fluid leakage therepast, irregardless of whether the predominant fluid pressure is acting on the ball element from below or above.
1. Valve apparatus adapted for use in a well bore, characterized by: tubular housing
means defining a flow passage; valve means rotatable about an axis that is transverse
to said flow passage between open and closed positions; seat means surrounding said
flow passage and having a seat surface and seal means coacting with said valve means
in said closed position to block fluid flow through said flow passage; and pressure
responsive means for forcing said seat surface against said valve means in response
to a predominate pressure either upstream or downstream of said valve means.
2. The apparatus of claim 1 characterized in that said pressure responsive means includes
piston means movable relative to said housing and said seat means and being sealingly
slidable with respect thereto, said piston means having one side subject to the pressure
of fluids upstream of said valve means and the other side subject to the pressure
of fluids downstream of said valve means.
3. The apparatus of claim 2 characterized by first seal means between said piston
means and said seat means and defining a first seal diameter; second seal means between
said piston means and said housing means and defining a second seal diameter, the
engagement of said seal means on said seat means with said valve means defining a
third seal diameter, said first diameter being lesser than said third diameter.
4. The apparatus of claim 3 characterized in that said second diameter is greater
than said third diameter.
5. The apparatus of any one of claims 1-4 characterized by spring means reacting between
said seat means and said housing means for biasing said seat means toward said valve
means.
6. The apparatus of claim 1 characterized in that valve means comprises a ball valve;
in that said seat surface and seal means comprises a retainer ring surrounding said
flow passage and having a spherical annular seat surface and carry valve seal means
that coact with an outer peripheral surface of said ball valve means in said closed
position to block fluid flow through said flow passage; and in that said pressure
responsive means comprises floating piston means sealingly engaging said retainer
ring and said housing means and movable between limit positions where an upper surface
thereof abuts said housing means and a lower surface thereof abuts said retainer rings,
said lower surface being subject to the pressure or fluids upstream of said valve
means and said upper surface being subject to the pressure of fluids downstream of
said valve means.
7. The apparatus of claim 6 characterized by a first seal ring between said piston
means and said retainer ring and defining a first seal diameter; and second seal means
between said piston means and said housing means and defining a second seal diameter,
the engagement of said valve seal means with said outer peripheral surface of said
ball valve means definina a third seal diameter, said first diameter being lesser
than said third diameter.
8. The apparatus of claim 7 characterized in that said second diameter is greater
than said third diameter.
9. The apparatus of claim 8 characterized by spring means reacting between said retainer
ring and said housing for biasing said retainer ring toward said ball valve means.