GB2257185A - Frangible flapper means - Google Patents

Abstract

Flapper means in the form of a one piece frangible, ceramic flapper member (410) is used with an extrusion resistant resiliently faced valve seat. Said flapper member is biased to the closed position and rotatable within a flapper member chamber from an open position during run in to a closed position as a result of the withdrawal of a wash pipe and a protector tube from the valve bore. Said frangible flapper means cooperates with said extrusion resistant valve seat to provide a reliable pressure resistant seal. The flapper 410 has a sloping sealing surface, a thickened centre section 415 and an integrally moulded hinge 413. <IMAGE>

Description

FRANGIBLE FLAPPER MEANS The invention relates to a frangible flapper means for use, for example, in an isolation valve inserted in a casing or liner of a subterranean well for purposes of both pressure testing said casing or liner and preserving well completion fluids from loss to the producing formation.

In the course of completing and maintaining subterranean wells, a number of operations are performed which require the introduction of fluids, generally termed completion fluids, into the well bore and into the producing formation. One of the common completion techniques performed on a well prior to placing it into production is gravel packing in which a slurry containing gravel is injected into the well to provide an in situ filtration medium to remove sand fines from produced fluids.

Subsequent to the gravel packing operation, a fluid such as water is introduced into the well to flush out excess gravel from the work string which is suspended within the bore of the production tubing. After the excess gravel slurry is flushed from the production tubing and the work string, the production tubing and the work string are filled with more dense completion fluids to prevent loss of produced fluids when the work string is withdrawn from the well prior to commencing production. After the well has been flushed with water and then filled with completion fluids as aforesaid, the work string, typically consisting of a service seal unit (cross-over tool), a sleeve valve shifter, and a wash pipe are withdrawn from the well bore leaving production packers, the closed sleeve valve and sand screens in place as functional parts of the production equipment.

Typically, the removed work string and its associated components contain large quantities of completion fluids which drain from the component tools into the annul us between the well casing and the work string as they are withdrawn from the well.

Because completion fluids are expensive and also possibly damaging to the producing formation, it is desirable to prevent the loss of completion fluids into the producing formation. It is also desirable to pressure test the tubing string to insure against the presence of leaks in the production tubing string prior to commencing production.

Typically, the processes of prevention of loss of completion fluids and of pressure testing the tubing is accomplished by the inclusion of an isolation valve with a frangible flapper member which is run in the hole as part of the production tubing.

Conventional frangible isolation valves typically have frangible sealing elements made of glass or metal and are equipped either with an elastomeric hinge means which is bonded directly to said glass or metal sealing element such as in U.S. Patent No. 4,813,481, or with retaining rings, springs or clips such as is disclosed in U.S. Patent 4,216,830, into which said glass or metal sealing element is mounted said rings, springs or clips also functioning as hinge means.Such conventional frangible sealing elements are subject to abrasion, pitting and scarring which impairs sealing ability, and, after the sealing element has been broken, said hinge means remain down hole and frequently at least partially obstructs the well bore thereby increasing the difficulty with which subsequent down hole operations may be conducted.

In addition to the above difficulties which are associated with conventional frangible sealing elements, such valves also typically employ a resilient tapered sealing member in the valve seat such as that disclosed in U.S. Patent No. 4,813,481. However, such resilient tapered valve seats in combination with the frangible sealing element often do not provide a reliable seal at the high pressures which are applied to the tubing during a pressure test thereof because the resilient sealing member tends to extrude into the bore of said valve seat.

According to one aspect of the invention, there is provided a frangible, ceramic valve flapper means comprising: a. a radially inwardly sloping sealing surface on one side; b. a thickened centre section; and c. an integrally moulded hinge means having a hinge pin bore therethrough adjacent said thickened centre section.

The invention also comprises a combination of such a frangible flapping means and an extrusion resistant valve seat assembly for cooperating in sealing engagement.

Preferably the flapper means of the invention is employed with a resilient valve seat which cooperates to provide at once a reliable seal at low pressure and a pressure resistant seal at higher pressures.

Advantageously, the resilient sealing member is arranged to be resistant to extrusion into the well bore.

The flapper means of the invention can form part of an isolation valve assembly which operates independently of the need for a packer, and an associated wash pipe to be run into the hole concurrently with said isolation valve assembly.

In a preferred embodiment, the frangible flapper means, is biased to the closed position by a spring mounted about the hinge means thereof. and is restrained in the open position by a protector tube which is shearably mounted in the valve body. Said protector tube, which functions to protect said flapper means from damage during run in and during tubing manipulations, has a no-go shoulder located within its bore.Said protector tube is removed from said valve bore when a no-go locator, which is made up as a part of the work string which is positioned within the bore of said protector tube on run in is pulled into contacting engagement with said no-go shoulder so that upward tension exerted against said no-go shoulder separates the shearable mounting means thereby allowing said protector tube to be removed from said valve bore and said flapper means element to rotate to the closed position as aforesaid. The groove in said grooved valve seat assembly functions to prevent the resilient valve seat member from extruding into the valve bore as pressure is applied to the closed flapper thereby providing a reliable pressure resistant seal.

In an alternative embodiment, said flapper means is restrained in the open position when it is introduced into the well bore by a wash pipe which extends from a packer mounted within the production string above said valve body and through the bore of said valve body. The wash pipe also functions to protect said flapper means from damage while the valve is being run in the hole. The flapper means is rotated to the closed position by the force exerted by said hinge spring when the wash pipe is pulled from the bore of said valve body as the work string is withdrawn from the hole.

The frangible flapper means, when in the closed position, both prevents the back flow of completion fluids into the formation and acts in sealing engagement with the valve seat to provide a closed system for pressure testing the tubing string above the completion tools. Said flapper means is arranged to be shattered when in the closed position by striking it with a tooth-faced blind box hammer.

The present invention will be further described by way of example with reference to the accompanying drawings. This application is a divisional application of GB 2245913 which has the same drawings but which relates to the isolation valve and its valve seat assembly also illustrated in the drawings. In addition the drawings illustrate a gravel pack system which is the subject of a further divisional application,

and they appear in another divisional application,

relating to a method of completing and maintaining a subterranean well.

In the drawings: Figure 1 A through J is a view, partly in section and partially in elevation, showing a typical well installation using an isolation valve assembly constructed according to the present invention.

Figure 2 is a view, partly in section and partly in elevation, showing the isolation valve with the sealing element in the closed position after removal of the protector tube.

Figure 3 is a cross section of the isolation valve taken along lines 3-3 with the sealing element in the fully open position.

Figure 4A is a view, in perspective of the valve seat assembly.

Figure 4B is a view, in perspective of the resilient seal means which comprises in part the valve seat assembly.

Figure 4C is a view, in perspective of the valve seat which comprises in part the valve seat assembly.

Figure 5 is an exploded perspective view of the seal assembly.

Figure 6 is a cross sectional view of the frangible sealing element taken along lines 6-6.

Figure 7 is a cross sectional view of the frangible sealing element taken along lines 7-7.

Figure 8 is an elevational view of the Blind Box Hammer.

Figure 9 is an end view of the Blind Box Hammer.

Figure 10 A is a view partially in section and partially in elevation of the valve assembly and the upper portion of the shear sub with the protector tube in place.

Figure 11 is a view in cross section of the nogo locator.

In the description that follows, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate the details of the present invention.

Referring to Fig. 1 A through J, a packer 5 of the type disclosed in U.S. Patent No. 4,834,175, or any similar packer, a sleeve valve assembly having a plurality of flow ports 63 therethrough comprising closing sleeve 61, and shifting sleeve 62 with detent 641 cut into its inner wall, valve assembly 20 and shear sub 12 are threadably connected to each other as part of the production tubing string 1. Below said shear sub, said production tubing string may also have threadedly included therein such tools as well screens, tell-tale screens and the like, with the lowermost of said tools in the string being stabbed into a sump packer, not shown, which is positioned below the lowermost producing formation in the well bore, all of which are well known in the art.Made up within the bore 11 of said production tubing string and run in the hole concurrently therewith is a work string comprising wash pipe 550 which extends below said packer and is threadedly connected to a service seal unit 60, otherwise known as a crossover tool, of the type disclosed in U.S. Patent No.

4,832,129, or any similar device, said service seal unit having shifting collet 65 with raised finger portions 651, 651a, several lengths of blank pipe, P, and no-go locator 71 threadedly interconnected with each other. Other examples of typical assemblages of gravel pack equipment are described and illustrated in brochure number OEC - 5545 entitled "Otis Sand Control Multi-Position Gravel Pack System", copyright 1990, published by Otis Engineering Corporation, Carrollton, Texas. Additional tools which may be desired or necessary to place the well in condition for production all of which are well known in the art, can also be included in either said production tubing string or in said work string.

Referring now to Figure 2, isolation valve assembly 20 consists of an upper housing 201 and a lower housing 221. The lower end of said lower housing is fitted with a threaded pin connector 222 and has a first opening 223 and a second opening 224, said first opening and said second opening being connected by fluid bore 225. A portion of the outer circumference of said lower housing forms an externally threaded radially inwardly stepped shoulder 226 over which sleeve portion 202 of the upper housing is threadedly fitted in sealing engagement with said lower housing and secured against rotation with reference to said lower housing by multiple set screws 203 which pass through said sleeve portion of said upper housing into a corresponding groove milled into the exterior of said stepped shoulder portion of said lower housing.

Said lower housing has groove 227 machined into its outer surface said groove passing around its circumference and operating to confine sealing means 228.

The bore 225 of said lower housing is of smaller internal diameter than the internal diameter of pin connector 222 forming shoulder 229 at the upper end of said lower housing.

Upper shoulder 229 has a ring-form groove 230 in its surface which accommodates sealing means 231. Sealing means 231 cooperates with valve seat assembly 30 to prevent leakage of fluid around the surfaces of said valve seat assembly.

Upper housing 201 is fitted at its upper end with threaded box connector 204 and has an opening 205 in said box connector connected by fluid bore 206 to valve chamber 207. The inner end of said box connector has an upper radially inwardly stepped shoulder 208 which reduces the diameter of fluid bore 206 and increases the thickness of upper housing sidewall 209 functions to provide support for shear screws 210 which are located intermediate said upper radially stepped shoulder 208 and a lower outwardly radially stepped shoulder 211 to support protector tube 501 shown in Figure lH, the structure of said protector tube being discussed below. The reduced diameter of bore 206 in the upper housing is similar in diameter to that of bore 225 in the said lower housing.Lower outwardly radially stepped shoulder 211 located intermediate shear screws 210 and said upper shoulder 229 of said lower housing increases the diameter of bore 206 thus forming valve chamber 207.

The chamber 207 located intermediate said lower outwardly stepped shoulder 211 and valve seat number 301 is of sufficient internal radius and length to accommodate the length and thickness of flapper means 410 remotely from said valve bore when said sealing element is in its open position.

Valve seat assembly 30 comprises a nonelastomeric valve seat 301 which cooperates with resilient seal means 302 to form an extrusion resistant valve seat which receives frangible flapper means 410 in sealing engagement therewith.

Valve seat 301 is a cylindrical member having flow bore 303 extending therethrough to which is bonded resilient seal means 302 as described below.

Annular groove 306 is cut into said valve seat adjacent said flow bore thereby forming support shoulder 307 intermediate said annular groove and said flow bore.

Resilient seal means 302 is preferably formed from a reinforced polymer such as a glass-filled fluorocarbon, preferably a glass-filled teflon compound will remain flexible under downhole conditions. Said resilient elastomeric material may also comprise an elastomeric polymer such as nitrile rubber. Of course, one skilled in the art will readily recognize that any resilient material which will remain flexible under downhole conditions could be substituted for those specified.

Referring now to Figure 4B, said resilient seal means has a lower mating surface 308 which is shaped to fit tightly in annular groove 306 and a hook-like inner support shoulder 309 which forms shoulder mating groove 310 intermediate said inner support shoulder and said lower mating surface.

As shown in Fig. 4A, a rectangular lower mating surface 308 is landed in groove 306 with hook-like inner support shoulder 309 mated to and cooperating with support shoulder 307 to prevent the resilient seal means from being extruded into flow bore 303 as pressure is exerted thereon by flapper means 410 and by fluids which exert pressure on said flapper when said flapper is in the closed position.

Said resilient seal is bonded in place in said valve seat using an appropriate cementing medium such as epoxy cement, which is well known in the art.

Prevention of such extrusion improves the quality of sealing engagement between said flapper and said valve seat. Laboratory tests of the valve seat assembly with the flapper means have indicated a positive seal with no leakage at an applied force of 10,000 psi.

The upper surface of resilient seal has a radially inwardly sloping shoulder 311 which forms a sealing surface in cooperation with corresponding sealing surface 411 of flapper means 410.

Valve seat member 301 also has a plurality of parallel bores 304 therethrough, each said bore being substantially parallel to valve bore 302 and being disposed to receive attaching means 315 to fixedly and sealingly attach said valve seat member to upper shoulder 229. Each of said plurality of parallel bores has an outwardly radially sloping shoulder 305 at its upper end to accommodate said attaching means in countersunk fashion to minimize intrusion of said attaching means into the chamber 207. When said valve seat member is securely attached to said upper shoulder, sealing means 231 is compressed between the lower side of said valve seat and said upper shoulder to form a fluid-tight seal therebetween.

Valve seat 301 has a stepped shoulder 312 cut into its upper surface to serve as a mounting plate for the horizontal portion 402 of hinge bracket 401, described below. Said mounting plate also has a plurality of hinge bracket mounting bores 313, 313a and spring stud retaining holes 314, 314a which restrain closing spring 430 in position as described below.

Flapping means 410 comprising a machinable, frangible ceramic material has sufficient strength to withstand required pressures and will shatter into small pieces when impacted by toothed faced blind box hammer 801, described below, to be circulated out of the well by fluid pressure. Sealing surface 411 which slopes radially inwardly from the outermost edge of said flapper means on its lower side forms a generally spherical seat arrangement when in contact with elastomeric valve face 311 of valve seat member 301. The upper side of said flapper means has two diametrically opposed radially upwardly sloping shoulders 412, 412a which cooperate with each other to form a thickened centre section 415 which is appreciably thicker than the outer edge and approximately the same thickness as hinge means 413.Hinge means 413, located adjacent said centre section 415 is an integrally molded part of said flapper means and has hinge pin bore 414 therethrough, said hinge pin bore being in substantially the same plane as the plane of seating surface 411. Flapper means 410 is fixedly attached to upper shoulder 229 by means of hinge bracket 401.

Hinge bracket 401 is preferably formed from a single piece of rigid material, such as steel or the like and has a substantially rectangular horizontal portion 402 and two vertical portions 403, 403a of approximately the same length rising in the same direction from opposite ends of said rectangular portion 402. Each vertical portion has a hinge pin bore 404, 404a therethrough, each bore being of sufficient diameter to accommodate insertion of hinge pin 420 and being positioned sufficiently remote from said horizontal portion to allow hinge portion 413 to rotate freely within the interior space bounded by the two said vertical portions and said horizontal portion.

Hinge bracket 401 is fixedly attached to valve seat 301 by a plurality of attachment means, each one of said plurality of attachment means passing through one of a plurality of bores through the horizontal portion of said hinge bracket and through a corresponding bore in valve seat 301 into upper shoulder 229. A plurality of fastener bores through said hinge bracket is necessary to fixedly align said flapper means over bore 225 of lower valve section 221 in such manner as to both maximize the sealing capabilities of the valve when said flapper means is in the closed position and align the valve seat assembly so the bore thereof is concentric with valve bore 225.

Flapper means 410 is rotatably attached to hinge bracket 401 by hinge pin 420 which passes first through bore 404 in the first of said vertical portions of said hinge bracket, thence through hinge pin bore 414 in said flapper means and finally through the bore 404a of the second of said vertical portions of said hinge means. In this manner, said flapper means, which is biased to the closed position by spring 430, described below, is free to rotate about the axis formed by hinge pin 420 and hinge pin bores 404 and 404a within the boundary formed by the inner surface of said valve chamber and the upper surface of said valve seat assembly.

Spring 430 is formed from a wire which first passes over hinge means 413, is then formed into coils 432, 432a which are located intermediate the interior edge of said vertical portions of said hinge bracket and confined in place by said hinge pin passing therethrough, and terminating in wire studs 433, 433a which are inserted through drill holes 408, only one of which is shown, and into spring stud retaining holes 314, 314a in valve seat assembly 301.

In the preferred embodiment of this invention depicted in Figure 10 A, flapper means 410 is maintained in the open position by protector tube 501 which is shearably mounted in upper housing bore 206, and passes in turn through valve chamber 207, and lower housing bore 225 extending below the lower end of said valve body into bore 910 of shear sub 91. The valve body and the shear sub cooperate to enclose said protector tube within the combined bores thereof during run in.

Protector tube 501 has an outer wall 502, an inner wall 510, a first opening and a second opening, said first opening and said second opening being connected by a fluid bore therebetween thus forming a fluid conduit therethrough. Said inner wall has a radially inwardly sloping shoulder 515 in close proximity to said first opening and an outwardly radially sloping "no-go" shoulder 520 located intermediate said inwardly sloping shoulder and said second opening. Said radially sloping shoulders cooperate to form pulling neck 508.

Said protector tube is maintained in position in said valve bore and said seal assembly bore by a plurality of shear screws 210 which are threadedly inserted in shear screw bores 212, said shear screw bores passing through said thickened wall 209 of upper housing 201 into threaded shear screw holes 505 which are drilled into the outer wall 502 of said protector tube.

The wash pipe which is made up to a service seal unit and gravel packer, as hereinbefore described, is located within the bore of said protector tube and is of such diameter as to pass freely through said protector tube bore. No-go locator 71 is threadedly connected to the lower end of said wash pipe.

Referring now to Figure 11, no-go locator 71 is a tubular member having a first opening 701 and a second opening 702 with a fluid conduit 703 therebetween. Box thread 704 is milled into inner surface of fluid conduit 703 adjacent said first opening and pin thread 706 is milled into outer surface 707 adjacent said second opening.

Intermediate said pin thread and said box thread is top radially outwardly sloping shoulder 751 in close proximity to bottom radially inwardly sloping shoulder 752, said top shoulder cooperating with said bottom shoulder to form no-go ring 760.

In an alternative embodiment, valve 20 is not fitted with protector tube 501. Instead, wash pipe 550 is made up without no-go locator 71 and extends below packer 5 and through the flow bore of valve 20. In this configuration, said wash pipe both restrains flapper means 410 in the open position, and protects said sealing element from pitting, abrasion or other damage while the tool is being run into the well. In this configuration, the entire work string as well as the casing string, which includes said isolation valve is assembled on the surface and run in the hole as a unit.

In operation, the valve with said protector tube in place and said sealing element restrained in the open position is assembled as part of the production tubing string to be run into the hole. Then said work string is assembled within the bore of said production tubing string so that said no-go locator is positioned below said protector tube and both the production tubing and the work string are run in the hole as a unit. When the tools are at the desired depth, packer 5 is manipulated to cause camming surfaces 512, 512a to engage cam blocks 513, 513a thus forcing toothed slips 514, 514a into engagement with the well casing, not shown, to provide support for said work string suspended therebelow. Multiple sealing elements 517a, 517b, 517c are then expanded into sealing engagement with said well casing.

When the gravel pack operation is complete, the work string together with the no-go locator is pulled from the hole. No-go locator 71 travels freely upwardly within bore 510 of protector tube 501 until top shoulder 751 of locator ring 760 engages no-go shoulder 520 of pulling neck 508. Continued upward tension shears screws 210 and allows protector tube 501 to be pulled from the hole with the work string When the bottom of said protector tube clears the upper edge of flapper means 410, said sealing element rotates into sealing engagement with valve seat 301 thus preserving completion fluids which drain from said work string for later recovery.Of course, it is readily apparent that if said no-go locator is not incorporated into the work string, such as a component of said wash pipe, and said protector tube is in the alternative embodiment hereinbefore described said flapper means will be maintained in the open position by said wash pipe until it clears said flapper means.

As the work string is pulled from the well, raised finger portions 651, 651a of shifting collet 65 engage detent 641 to shift sleeve 62 into the closed position. Continued upward motion of the work string pulls shifting collet 65 from sleeve 62.

After said completion fluids have been recovered from the tubing string bore by conventional recovery means, production tubing including a production seal assembly is then installed in the well and connected to the packer.

Said production tubing may then be pressure tested for leakage.

After the pressure testing of the production tubing string is complete, a tooth-faced blind box hammer 801, described below, is lowered into the well bore on a wireline until it comes into contact with closed flapper means 410. The blind box hammer is then raised and allowed to strike said sealing means under the force of gravity.

The teeth of the blind box hammer cause the frangible flapper means to shatter into pieces small enough to be washed out of the well bore with completion fluid or the like. Once said sealing means is shattered, the well is in condition to begin production.

One skilled in the art will readily recognize that any striking means, such as a drop bar, a dart, the mule show guide on the bottom of a Production Seal Unit, or the like, will function to shatter said frangible flapper means.

Tooth-faced blind box hammer 801 is a striking tool of generally cylindrical shape having pin connector 802 at one end and a toothed striking face 805 at the other end thereof. The diameter of said blind box hammer is slightly less than that of valve bore 225 so that said blind box hammer can freely pass therethrough. In addition to said pin connector, intermediate said pin connector and said striking face said blind box hammer may be equipped with a fishing neck F of the type commonly employed in wireline operations to retrieve tools unintentionally left in the well bore.

As shown in Figure 9, striking face 805 has a first plurality of parallel grooves 806 milled in one direction thereon and a second plurality of parallel grooves 810 milled into said striking face at an angle to said first plurality of grooves thus forming a plurality of teeth 815 on the surface of said striking face.

Should it be desired to retrieve said valve from the hole, upward tension exerted on the production tubing after release of the packer will cause shearable means 121 which is a component of shear sub 12 to separate thus allowing the retrieval of the valve from the hole while permitting those tools and components located below said valve in the production string to remain down hole.

Although this invention has been described with reference to a preferred embodiment, the foregoing description is not intended to be construed in a limiting sense. Various modifications will be suggested to persons skilled in the art by the foregoing specification and illustrations.

Claims (7)

1. A frangible, ceramic valve flapper means comprising: a. a radially inwardly sloping sealing surface on one side; b. a thickened centre section; and c. an integrally moulded hinge means having a hinge pin bore therethrough adjacent said thickened centre section.

2. The frangible ceramic flapper means of claim 1 comprising machinable material.

3. The frangible ceramic flapper means of claim 1 or claim 2 having a hinge pin insertable through said hinge pin bore and a closing spring wound about said hinge pin and said hinge means.

4. The frangible ceramic flapper means of claim 3 being biased to the closed position by said closing spring.

5 The frangible machinable flapper means of any one of the preceding claims in combination with an extrusion-resistant valve seat assembly for cooperation in sealing engagement therewith.

6. A frangible, ceramic valve flapper means constructed and arranged for use and operation substantially as described herein with reference to Figs. 1 to 7 of the accompanying drawings.

7. A frangible flapper means in combination with an extrusion-resistant valve seat assembly constructed and arranged for use and operation substantially as described herein with reference to Figs. 1 to 7 and 10A of the accompanying drawings.