VALVE FOR USE IN A WELLBORE

Abstract: A valve for use in a wellbore, which valve comprises: a body through which fluid can flow; a valve seat (507; 82) connected to said body or integral therewith and through which fluid can flow; and a valve member (510; 60; 80) adjacent said valve seat and selectively movable to seat against the valve seat to close said valve to fluid flow and selectively movable away from the valve seat to open the valve to fluid flow, characterized by at least one recess (530; 520; 84) on at least one of said valve members and said valve seat for accommodating debris and thereby inhibiting said debris preventing closure of said valve.

Description: VALVE FOR USE IN A WELLBORE This invention relates to a valve for use in a wellbore and, more particularly, but not exclusively, is concerned with a float shoe incorporating such a valve, a float collar incorporating such a valve, and a mud saver assembly incorporating such a valve. During construction of oil and gas wells a borehole is drilled to a certain depth. The drill string is then removed and casing inserted. The annular space between the outside of the casing and the wall of the borehole is then conditioned for cementing by pumping conditioning fluid down the casing. The conditioning fluid flows radially outwardly from the bottom of the casing and passes upwardly through the annular space where in entrains debris and carries it to the surface. Finally, cement is pumped downwardly through the casing, squeezes radially outwardly from the bottom of the casing and passes upwardly into the annular space where it sets. Conventionally a float shoe is fitted on the bottom of the casing or a float collar close to the bottom. Both these devices incorporate a valve which inhibits fluid entering the casing from the borehole but permits fluid to flow from the casing into the borehole. One of the problems associated with known float shoes and float collars is ensuring that they close properly even though debris may be present. * * * Turning now to an analogous problem, the rate at which casing can be lowered into a wellbore is limited by the resistance of fluid in the bore. Various proposals have been made to increase the rate at which the casing can be lowered down the bore. One common solution is to pump mud into the casing as it is lowered. This solution is very effective and various devices have been designed to facilitate the introduction of mud into the top of the casing. One of the problems which can arise when lowering casing is that the casing may stick. This problem is particularly apparent when lowering casing down deviated bores. If the casing sticks the usual procedure is to "circulate" the mud. This involves pumping mud down the casing under pressure and allowing it to flow back to the surface in the annular space between the outside of the casing and the bore. Generally, circulating will free any minor obstruction and allow the running of the casing into the bore to be continued. It will be appreciated that for the purpose of running casing the mud is simply allowed to flow into the casing while, for circulation, the top of the casing is sealed so that the interior of the casing can be pressurized, typically from 100 to 300 bar. One device for use in running and circulating is the known prior art LaFleur Autoseal Circulating Head. In use, mud is introduced into the casing via a flexible mud supply hose generally referred to as a "fill tube" while casing is being run. It is necessary to remove the fill tube each time a stand of casing has to be added to the casing string. Conventionally the fill tube is pivoted to one side of the drill string while the new stand is moved into place. In order to inhibit mud dropping onto the working platform and making it very slippery and dangerous, a "mud saver assembly" including a valve is provided at the lower end of the fill tube. However, it is difficult to ensure that the valve closes properly because of the solids which are often present in the mud for a variety of reasons. Certain known mud valves have several disadvantages. In particular, several of them employ metal to metal seals which are rapidly eroded by the abrasive flow of mud rendering the valves non-sealing. In various prior art assembly grit or debris lodged between valve parts or in valve parts, e.g. between a valve member and a valve seat, prevents closing of the valve. The present invention aims to reduce this problem. According to the present invention there is provided a valve for use in a wellbore, which valve comprises a body through which fluid can flow, a valve seat connected to the body or integral therewith and through which fluid can flow, a valve member adjacent the valve seat and selectively movable to seat against the valve seat to close the valve to fluid flow and selectively movable away from the valve seat to open the valve to fluid flow, characterized by at least one recess on at least one of the valve member and the valve seat for accommodating debris and thereby inhibiting said debris from preventing closure of said valve. Further features are set out in Claims 2 et seq. For a better understanding of the present invention reference will now be made, by way of example, to the accompanying drawings, in which: - Fig. 1A is a side cross-section view of a first embodiment of a valve according to the present invention; Fig. IB is a side cross-section view of a second embodiment of a valve according to the present invention; Fig. 2 is a side cross-section view of a third embodiment of a valve according to the present invention; Fig. 3A is a vertical cross-section through a spring retainer which forms part of the valve shown in Fig. 2; Fig. 3B is an underneath plan view of the spring retainer shown in Fig. 3A; Fig. 4A is a vertical cross-section through a nose guide which forms part of the valve shown in Fig. 2; Fig. 4B is an underneath plan view of the nose guide shown in Fig. 4A; Fig. 5 is a vertical cross-section through a wear housing which forms part of the valve shown in Fig. 2; Fig. 6A is a side elevation of a valve stem guide which forms part of the valve shown in Fig. 2; Fig. 6B is an underneath plan view of the valve stem guide shown in Fig. 6A; Fig. 7 is a vertical cross-section through a hollow body which forms part of the valve shown in Fig. 2; Fig. 8 is a side elevation of a piston which forms part of the valve shown in Fig. 2; Fig. 9 is a vertical cross-section through a valve member which forms part of the valve shown in Fig. 2; Fig. 10 is a cross-section through a valve seat which forms part of the valve shown in Fig. 2; Fig. 11 is a vertical side cross-section through an alternative valve member; Fig. 12 is a vertical cross-section through a valve seat designed to accommodate the valve member of Fig. 11; and Fig. 13 is a schematic view showing a valve in accordance with the present invention in use in a mud saver assembly. Referring to the drawings, Fig. 1A shows a float shoe 500 according to the present invention which is based on the float shoe shown in Figs. 10 and 11 of WO 95/25873. The float shoe 500 incorporates a valve 502 which is held in position by an annulus of high density cement 504. The valve 502 comprises a tubular housing 505 including a cylindrical portion 506 and a valve seat 507. A valve member 509 is slidably mounted in the tubular housing 505 and is biased to a closed position (as shown) by a light spring 512. The valve member 509 comprises a valve steam including a tubular portion 511A provided with windows 51IB and 511C and a head 510 which is shown seated on the valve seat 507 and biased there- against by the light spring 512 which acts between the valve seat 507 and a flange 516 on the valve member 509. The head 510 of the valve member 509 is provided with a threaded bore 524 into which is screwed an attachment 525. The attachment 525 comprises a spider having four legs 527 which radiate outwardly from a hub 528. A bolt 529 extends through the hub 528 and is screwed into the threaded bore 524. When lowering a string of casing into a wellbore it is sometimes desirable to be able to allow liquid from the wellbore to flow into the casing at a controlled rate. For this purpose a shear pin 531 is first inserted through a bore extending through the hub 528 and the bolt 529. The hub 528 is then rotated so that the bolt 529 enters the threaded bore 524. Rotation is continued until the attachment 525 bears against the valve seat 507 and the fill valve is opened by the desired amount. In use, the valve member 509 is opened by the desired amount and the casing lowered down the wellbore. When the pressure on the bottom of the head 510 of the valve member 509 reaches a predetermined level the shear pin 530 breaks and the fill valve closes. During a subsequent conditioning and/or cementing operation the valve member 509 is displaced downwardly to allow fluid to pass through the valve 502. When the flow through the valve 502 ceases the valve member 509 is biased towards its closed position by the light spring 512. One of the difficulties is that the ambient liquid frequently contains debris. This can arise from a number of sources, for example particles in the mud, particles in the well conditioning fluid and debris from the wellbore itself. This debris can become trapped between the valve seat 507 and the valve member 509 and prevent the valve 502 closing. In order to reduce this problem the fill valve 502 shown in Fig. 1A is provided with a recess 530 which opens adjacent the valve seat 507. The head 510 is preferably made of resilient material (e.g. somewhat flexible rubber, plastic, polyurethane, etc. that per- mits some flexing) so that a lower portion of the head 510 subjected to fluid pressure may flex due to the presence of the recess 530 to enhance the sealing effect of the head 510 against the valve seat 507. However, the head 510 could also be made of rigid material (e.g. rigid plastic, metal, e.g. stainless steel, e.g. SS316). In either case the recess or recesses 530 are used to accommodate debris that might otherwise inhibit proper and complete seating of the valve member against the valve seat. It is within the scope of this invention to use one or more recesses 530 on any valve member disclosed in PCT Patent Publication WO 95/25873 or on any known valve member of any valve used in any wellbore operations or of any known float shoe, float collar or valve used in wellbore operations. Fig. IB shows a float shoe 501 like the float shoe 500, Fig. 1A (and the same numerals denote the same parts), but without the recess 530. The valve seat 207 does have a recess 520 encircling it for holding debris and/or for facilitating sealing in a manner similar to that in which the recess 530 operates. Fluid pressure on the head 510 pushes it against the valve seat 207 and parts of the valve seat 207 flex in response to the pressure due to the presence of the recess 520. The valve seat 207, in one aspect, is preferably made of suitable material (e.g. but not limited to plastic or polyurethane) to allow flexing of its lower portion. * * * Fig. 2 shows a mud saver assembly 10 according to the present invention which has a hollow body 12 (made, e.g. of polyurethane or stainless steel or plastic or steel) to which a nose guide 14 is threadedly mated. A spring retainer 16 is held in place in the nose guide 14 by a spring 50. Lock screws 83 hold the nose guide 14 in place. A wear housing 18 is secured within the body 12 with an end 22 held between the interior wall of the body 12 and portion 24 of a valve seat 20. The valve seat 20 has a top 26 that abuts a shoulder 28 of the body 12. A valve stem guide 30 is secured to or formed integrally with an end 32 of a piston 40. The valve stem guide 30 has a plurality of stabilizing vanes 33 that guide the piston's movement within the wear housing 18. A spring 50 biased against an inner shoulder 52 of the spring retainer 16 and against the bottom 54 of the piston guide 30 initially holds the piston 40 and a polyurethane valve member 60 against a seat surface 62 of the valve seat 20. When fluid pressure on the top of the valve member 60 exceeds the force of the spring 50, the valve member 60 moves away from the valve seat 20 (downwardly in Fig. 2) to open the valve assembly 10. The spring 50 is positioned round a shaft 76 which moves within the spring 50. In one aspect the valve member 60 is formed on the piston 40 by molding thereon. The valve member, piston, valve seat, valve stem guide, wear housing, nose guide, spring retainer, and body may be made of polyurethane, aluminum, aluminum alloy, zinc, zinc alloy, stainless steel (e.g. SS316), plastic, composite, fiberglass, or metal. A set screw 84 ' may be used to attach the valve stem guide 30 to the valve stem 76. Alternatively, one assembly may include the piston guide 30, piston 40, and shaft 76 and may be made of stainless steel. Such an assembly may also include the valve member 60. The piston 40 may be replaced with a solid valve member. Figs. 3A-10 show various parts of the mud saver assembly 10. As shown in Fig. 2 and Fig. 9, the valve member 60 has three recesses 70 which encircle the valve member 60 (which itself is generally circular when viewed from above and below). In embodiments in which the valve member is made of flexible material, the three recesses 70 define fins 72 which encircle the circular valve member 60 and which flex when pushed against the valve seat surface 62 of the valve seat 20. The lower recess 70 or the two lower recesses 70 or the upper and lower recess may be omitted. In another embodiment the valve member 60 is made of rigid material and the recesses 70 capture debris. In another embodiment the valve member 60 is made of flexible material and the recesses 70 capture debris. One, two, three or more such recesses may be used and they may be wider or narrower depending on the size recess and/or fin(s) desired. One, two, three or more fins may be employed and such a fin or fins may be disposed anywhere on the valve member. In certain embodiments a single recess is used positioned at the top, at the bottom, or anywhere on the valve member body. The valve seat surface 62 is tapered so that the hollow interior is wider at the bottom and narrower at the top. The valve member 62 is correspondingly tapered exteriorly to mate with the taper of the seat surface 62 to enhance the sealing effect of the valve member 62 against the valve seat 20. Fig. 11 shows an alternative valve member 80 which has no recesses or fins. Fig. 12 shows an alternative valve seat 82 which has three recesses 84 that define two middle fins 86 and a top portion 88. The valve seat 82 is intended to accommodate the valve member 80. It is within the scope of this invention to have a valve seat with one, two, three or more recesses and with one, two, three or more fins. It is also within the scope of this invention to have a valve assembly with a valve member 60 and a valve seat 82 with recess on the one aligned with recesses on the other or offset and/or with fins on one aligned or offset from fins on the other. The valve seat 82 may be made of flexible or rigid material. 0-rings 90 seal the various interfaces between parts at which they are located. The mud valve assembly 10 may be used with a circulating head 100 (see e.g. Fig. 13) (e.g. but not limited to a LaFleur Autoseal Circulating Head) with the head interconnected above the mud saver assembly with or without an interconnected top drive 102.

Claims: CLAIMS 1. A valve for use in a wellbore, which valve comprises a body through which fluid can flow, a valve seat (507; 82) connected to said body or integral therewith and through which fluid can flow, and a valve member (510; 60; 80) adjacent said valve seat and selectively movable to seat against the valve seat to close said valve to fluid flow and selectively movable away from the valve seat to open the valve to fluid flow, characterized by at least one recess (530; 520; 84) on at least one of said valve member and said valve seat for accommodating debris and thereby inhibiting said debris prevent- ing closure of said valve. 2. A valve as claimed in Claim 1, wherein said at least one recess is positioned near an end of said valve member thereby defining a fin between said at least one recess and said end, and said valve member is made of flexible material so that the fin is flexible to enhance sealing of said valve member against said valve seat. 3. A valve as claimed in Claim 1 or 2, further comprising a plurality of spaced apart recesses (70; 84). 4. A valve as claimed in Claim 3, wherein at least one fin is defined between two adjacent recesses and the valve member is made of flexible material so that said at least one fin is flexible to enhance sealing of said valve member against said valve seat. 5. A float shoe including a valve as claimed in any preceding claim. 6. A float collar including a valve as claimed in any of Claims 1 to 4. 7. A mud saver assembly including a valve as claimed in any of Claims 1 to 4.

Inventors: BUDDE PETER, BUDDE, PETER
Applicants: LUCAS BRIAN RONALD, WEATHERFORD LAMB, LUCAS, BRIAN, RONALD, WEATHERFORD/LAMB, INC.
Application year: 1998
Main classification: E21B21
IPC codes: E21B21