VALVE FOR USE IN WELL BORES

Abstract: A dual purpose valve for use in well bore casings has a body (12) supporting a valve seat (18), a movable valve element (24) axially movable to a guide (22) and having a closure means (28) adapted in one position to sealingly contact the seat (18) to act as a back flow preventer. The valve defines a passage for fluid flow of sufficient cross section that it can serve as an automatic fill valve for permitting wall bore fluid to flow into a casing string. A releasable locking means (32) is inserted in or adapted for insertion in the valve body in a locking position, in which the locking means contacts the valve element (24) to prevent movement of the valve element towards the valve seat to convert the valve, on site, from a back flow preventer operation to an auto fill valve operation. The locking means is formed so that, when released, it falls away from or retracts to release the valve element. Preferably it comprises a plurality of segments (34).

Description: VALVE FOR USE IN WELL BORES This invention relates to valves for use in well bore operations and more particularly to a valve which can be used both as a float collar valve for automatic filling when running a casing string into a well and as a back flow preventer valve when cementing the casing. In running a casing string into a bore hole it is necessary to provide a valve for controlling the rate of flow of fluid from the bore hole into the casing. If the fluid is not controlled as it enters the bottom of the casing, the fluid pressure in the well may be sufficient to cause the fluid to blow out through the top of the casing. On the other hand, it is necessary to fill the casing gradually as it is lowered to compensate for the head of fluid on the outside of the casing to prevent implosion or collapse of the casing. Self fill float valves are known for limiting the rate of flow of fluid into the casing as it is being lowered into the bore hole. After the casing has reached the desired depth, it is cemented in place by conducting cement down the casing and out through the bottom of the casing, where it flows upwardly through the annular space between the casing and the bore hole wall. Accordingly, it is necessary to provide a valve which will resist the back pressure of the cement slurry in the annulus. Since the self fill float valve allows a restricted flow into the casing and the back pressure valve prevents flow of slurry back into the casing the requirements for valve operation during different portions of the casing process are different and it would be desirable to design a valve in a single unit which would function for both portions. U.S. Patent 3385372 attempts to provide such a single unit valve. In this valve there is a collar having a tubular body with a valve guide in the body. A valve seat is formed in the body above the valve guide. A movable valve element is mounted in the valve guide in position to move upwardly into engagement with the valve seat and is spring biased towards the valve seat. A fluid reaction surface is mounted on the valve stem below the valve element and is biased downwardly by a spring that applies a greater axial force to the valve stem than does the spring biasing the valve element. The fluid reaction surface is arranged to exert an upwardly directed force on the valve stem in response to the flow of fluid upwardly through the casing. Thus the reaction surface restricts or limits the rate of flow upwardly by displacing the valve element against the valve seat. There is a shear pin joining the reaction surface to the valve stem and, upon pumping fluid down the casing at a predetermined rate, the force of the fluid on the reaction surface breaks the shear pin and causes the reaction surface to be displaced downwards and thereby rendered ineffective. After the shear pin is broken, the valve element is released and its spring urges the valve element against the valve seat so that the valve is converted to a back pressure valve. The valve of U.S. Patent 3385372 has numerous disadvantages, particularly, once the shear pin is broken the valve cannot be converted back to a self fill flow valve. In addition, the surface reactive areas necessitated by the valve design block the flow path so much that fluid simply cannot enter at the bottom of the casing fast enough to provide adequate pressure equalisation between the casing and well bore fluid to allow self fill operation. Because of this limitation on flow rate the interior of the casing must be filled with well bore fluid by pumping the fluid down the casing rather than letting fluid enter the casing at the bottom of the casing string. Another primary disadvantage of a valve according to U.S. Patent 3385372 is the imprecision of and hence the unpredictability of the performance of the shearing mechanism and the valve closure mechanism. This imprecision is due to the numerous engineering design and manufacturing characteristics of these mechanisms. The shearing of the shear pin depends on the pressure differential across the fluid reactive member, the material and dimensions of the pin and the characteristics of the spring which biases the fluid reaction surface downwardly. A failure or inadequacy related to the design, selection or manufacture of any of these variables can result in a shear pin that shears too soon, too late, or never shears at all. The shear pin can be sheared by force of vibration when the valve is shipped or moved or the force of any impact on the valve and once the pin is broken the valve cannot be converted back to a self fill flow valve. A float collar shell is a cylindrical shell member used to contain the valve. In use it forms part of the casing string. The dimensions of a standard float collar shell are such that the valve of U.S. Patent 3385372 does not fit in the standard shell because of the added length necessary to accommodate the valves fluid reactive mechanism. An object of the present invention is to provide a valve which can be converted from a back flow preventer mode to an auto fill mode by insertion of a releasable locking means. Such conversion can be done after the valve has left the factory and on site. After the locking means has been released it can be re-inserted to re-convert the valve. Accordingly, the present invention provides a dual purpose valve for use in well bore casing comprising a body supporting a valve seat, a movable valve element having a closure means adapted in one position to sealingly contact the seat to act as a back flow preventer, and in which the valve is adapted to be converted by releasable locking means from a back flow preventer mode to an automatic fill mode. Preferably the valve defines a passage for fluid flow of sufficient cross section that it can serve as an automatic fill valve for permitting well bore fluid to flow into a casing string without requiring additional pumping equipment. Such a valve can be used as a dual purpose valve for back flow prevention and automatic fill and is easily converted from one to the other on site after it has left the factory. Preferably the valve has dimensions such that it can be used with a standard float collar. Preferably the valve includes a releasable locking means inserted in or adapted for insertion in the valve body in a locking position in which the locking means contacts the valve element and stop means to prevent movement of the valve element towards to the valve seat, the locking means being formed so that when released it falls away from or retracts to release the valve element. The locking means may engage in a groove in the valve element, in recesses in the valve element or may have teeth for gripping the valve element. Preferably the locking means comprises a plurality of separate members which fall away from the valve element when it is moved from the locking positio'n in a direction away from the valve seat. The locking members may be releasably adhered to each other, the valve element or a guide member to retain them in the locking position until released. Embodiments of valve, in accordance with the invention, will now be described by way of example only with reference to the accompanying drawings of which:- Figure 1 is a cross sectional view of one embodiment of valve with a releasable locking mechanism in place, Figure 2 is a perspective view of one segment of the locking means of Figure 1 on an enlarged scale, Figure 3 is a top view of the segment of Figure 2, Figure 4 is a top vi ew of the bottom cap of the v a l v e o f F i g u r e 1 o r t h e o t h e r embodiments of valve, Figure 5 is a cros s sect i onal view of the valve of Figure 1 after the locking mechanism has been released and the valve has closed, Figure 6 is a cross sectional view of another embodiment of valve with the releasable locking mechanism in place, Figure 7 is a perspective view of a segment of a locking ring, on an enlarged scale, which may be used with the valve of Figure 6, Figure 8 is a top view of the segment of Figure 7 , Figure 9 is a cross sectional view of the valve of Figure 1 modified to eliminate the spring, Figure 10 is a cross sectional view of the valve of Figure 6 modified to eliminate the spring,. Figure 11 is a cross sectional view of another embodiment of valve, Figure 12 shows a modified valve element and retaining means with a portion of the guide means of a valve, and Figure 13 shows a further modified valve element and retaining means with a portion of the guide means of a valve. It should be understood that the invention extends to embodiments in which any feature described with reference to one embodiment is combineddf appropriate)with features of another embodiment ,with obvious modifications if necessary. The valve 10 of Figures 1 to 4 has a tubular body 12 to which are connected a top cap 14 and a bottom cap 16, the top cap providing a valve seat 18. The bottom cap has inwardly and upwardly directed ribs 20 which support a valve guide in the form of a tube 22. A valve element 24 having a stem and a valve closure member 28 is guided by the valve guide 22 for movement towards and away from the valve seat and is urged by a spring 26 mounted about the valve stem and abutting the top of the ribs 20 to sealingly contact the valve seat. The valve stem has a circumferential groove 30. The guide 22 defines a bore for receiving and guiding the valve stem its lower part forms a downwardly and outwardly tapered recess 33 opening in a direction away from the valve seat 18. A releasable locking means in the form of a segmented- ring 32 comprises a plurality of segments 34 which locate around the valve stem in the recess 33, each segment 34 having a tapering side 35 whose taper conforms to the taper of the conical section 33. Each segment has a lower bar portion 36 which is received in the groove 30 of the valve stem. In the locking position shown in Figure 1 the upward thrust of the spring 26 on the valve stem pulls up on the segments 34 holding them in place and thereby locking the valve stem itself against upwards movement towards the valve seat. With the locking means in position the valve can act as an automatic fill valve in a well bore casing, the body 12 containing the valve element and guide means defining a passage for fluid flow of sufficient cross section for this automatic fill mode without additional pumping. The locking means can be released by downward movement of the valve element away from the valve seat, caused for example by the force of fluids pumped down the casing, such downward movement causing the segments to fall away from the valve element and allowing it to then move upwardly in response to the action of the spring 26 to bring the closure member 28 into sealing contact with the valve seat and close off the valve 10 thus stopping the flow of fluids between the casing and well bore. The valve then acts as a back flow preventer but can be re-converted to an automatic fill mode by re¬ insertion of the releasable locking means. The valve of Figure 6 has a modified valve stem and locking means but is otherwise similar. In this arrangement the valve stem has no groove 30 and the segments 134 do not have the protruding bar portions 36 but grip the valve stem. If desired the surfaces of the segments 134 which contact the valve stem can be roughened or formed with small teeth 137 as shown in Figures 7 and 8. As shown in Figures 1 and 6, a holding member such as a gasket 38 can be employed to assist in maintaining the segments 34 or 134 in their positions in the recess 33. This gasket may, for example, be a water soluble material which is relatively weak such as thin cardboard which is glued to the bottom of the segments.lt need not be soluble. The valves of Figures 9 and 10 are similar to those of Figures 1 and 6 respectively with the elimination of the spring 26. The deletion of the spring 26 requires that the locking members 32 be firmly held within their respective valve guides. To facilitate this an amount of adhesive can be used to hold the segments of the locking means to the surface of the cylinder or to the surface of the valve stem. Figure 11 shows a modified valve in which the recess 33 has been omitted and the segments 434 simply engage the bottom of the guide 22 and the groove 30 in the valve stem (or an ungrooved stem). The upward force of the spring 36 keeps the locking ring engagement with the stem and guide. As described the spring could be eliminated and adhesive used to hold the segments in position. Figure 12 shows a further modified stem and locking means. In this case the stem 24 has a recess 530 which receives a locking means in the form of a stud 534. The stud abuts the bottom of the valve guide 22 to prevent movement of the valve stem until the stem is moved downwards from the locking position at which point the stud will be moved out of contact with the guide 22 and will fall out of the recess 530 converting the valve to a back flow preventer mode. If necessary adhesive can be used between the stud and bottom of the cylinder or stem. More than one stud and recess may be used if desired. Figure 13 shows a further embodiment in which the valve stem and locking means have been modified. In this arrangement a locking element in the form of an arm 634 has a lip 635 which in the locking position abuts the outer surface of the guide 22. The arm 634 is connected to a spring 633 which in turn is connected to the valve stem 24. The arm is retractable by the spring into a passage 641 in the valve stem upon movement of the stem from the locking position; the lip then releases from the guide and the valve element is free to move towards the valve seat. The arm could alternatively be mounted to retract into the valve guide on release. The valve element could be used in a conventional valve housing and guide. The segments should be non frangible under normal operating conditions. The preferred material is aluminium or other metal.

Claims: CLAIMS 1. A dual purpose valve for use in well bore casings comprising a body (12) supporting a valve seat (18), a movable valve element (24) having a closure means (28) adapted in one position to sealingly contact the seat (18) to act as a back flow preventer, the valve defining a passage for fluid flow of sufficient cross section that it can serve as an automatic fill valve for permitting well bore fluid to flow into a casing string, characterised in that the valve is adapted to be converted by releasable locking means (32) from a back flow preventer operation to an auto fill valve operation. 2. A valve according to Claim 1 including a guide member (22) mounted in the valve body and arranged to guide the valve element for movement into and out of contact with the valve seat, characterised by a releasable locking means (32) inserted in or adapted for insertion in the valve body in a locking position, in which the locking means contacts. the valve element ( 24) to prevent movement of the valve element towards the valve seat, the locking means being formed so that, when released, it falls away from or retracts to release the valve element. 3. A valve according to Claim 2 characterised in that the locking means comprises one or more segments (34) which substantially surround and engage a stem (24) of the valve element and are arranged to fall away from the stem on release. 4. A valve according to Claim 2 characterised in that the locking means comprises one or more separate locking members (534) which engage in the valve element in the locking position and which fall away from the valve element on release. 5. A valve according to Claim 2 chararacterised in that the locking means comprises one or more retaining members (634) urged to a position in which when released they retract into the valve element or guide member. 6. A valve according to any of Claims 2 to 4 in which the valve element has a stem (24) defining a groove (30) and the locking means locates in the groove in the locking position. 7. A valve according to any of Claims 2 to 4 characterised in that the locking means includes teeth (137) arranged to grip the valve element in the locking postion. 8. A valve according to any of Claims 2 to 5 characterised in that the locking means is formed to be released by movement of the valve element (24) from the locking position in a direction away from the valve seat (18) . 9. A valve according to any of Claims 2 to 5 characterised by a holding means arranged to hold the locking means in the locking position. 10. A valve according to any of Claims 2 to 5 characterised by a holding means which includes breakable means for adhering the locking means to the guide means or the valve element. 11. A valve according to any of Claims 2 to 4 characterised by holding means which includes breakable means (38) for adhering at least two parts of the locking means to each other to facilitate maintenance of the locking means in the locking position prior to release. 12. A valve according to any of Claims 2 to 5 characterised by holding means including a biasing means (26) urging the valve element towards the valve seat. 13. A valve according to any of Claims 2 to 5 in which the guide means defines a bore for receiving and guiding a stem of the valve element characterised in that the bore includes a recess (33) opening in the direction away from the valve seat and designed to receive the locking means. 14. A valve according to any of Claims 2 to 4 characterised in that the guide means defines a recess (33) conically tapered downwardly and outwardly and opening in a direction away from the valve seat and the locking means has a side (35) with a taper corresponding to the taper of the recess . 15. A valve according to any of Claims 1 to 5 having dimensions such that it can be used with a standard float collar of a well bore casing. 16. A valve substantially as described herein with reference to or as illustrated in the accompanying drawings. 17. A locking means for use in a valve according to any of Claims 1 to 5, the locking means (32) comprising a plurality of parts (34) each adapted in a locking position , to inter-engage with a valve guide (22) and the valve element (24) to retain the valve element against movement in one direction and each being adapted to fall away from or retract to release the valve element on movement from the locking position in the opposite direction.

Inventors: HASSANZADEH HEDAYAT H, MCCLUNG GUY L, HASSANZADEH, HEDAYAT, H., MCCLUNG, GUY, L.
Applicants: WEATHERFORD US INC, WEATHERFORD U.S. INC.
Application year: 1986
Main classification: E21B21
IPC codes: E21B21