Unloading Injection Control Valve

1. Field of the Invention

The invention relates to a valve apparatus for use in a subterranean fluid transmission conduit or work string in which fluid pressure above the valving apparatus can be used to open the valve to permit fluid pressure to act at a location below the valve.

2. Description of the Prior Art

There are many downhole tools and operations which require the injection of fluid through a tubing conduit to the producing formation or some other location within the well or which require the use of fluid pressure applied through the tubing. For example, washing or acidizing operations require fluid injection through the tubing bore. Some tools also incorporate fluid pressure actuated expandable packing elements which are expanded into sealing engagement with the wall of the casing upon the application of fluid pressure within the tubing or the tool bore.

Such tubing pressure dependent operations or well tools generally not only require the injection of fluids through the tubing bore or the application of pressure within the tubing, but often require control over the relative fluid pressures in both the tubing and in the annulus between the tubing or fluid transmission conduit and the well bore or casing. For example, the pressure actuation of the downhole tool, such as a tool having expandable packing elements, may be dependent upon the force generated by the pressure differential existing between the tubing and the annulus. To set or expand the packing elements, the pressure in the tubing, in general, must exceed the pressure in the annulus. Conversely to permit the expanded packing elements to relax, the pressure in the tubing must generally be less than the pressure in the annulus. In low fluid level wells, the annulus fluid pressure may be continuously less than the hydrostatic pressure in the fluid transmission conduit or work string. Thus any operation dependent upon a greater pressure in the annulus than in the tubing would be difficult to perform. For example, a well tool having an expandable packing element actuated by excess fluid pressure in the tubing may be difficult to retract when tubing pressure is reduced because the hydrostatic pressure in the tubing will still exceed the pressure acting on the packing elements in the annulus. Similarly, the excess pressure differential in the tubing may prevent the movement of a tool having a cup type packing element because of the pressure difference between the tubing and the annulus. A simple reliable apparatus for controlling the pressure in the tubing and in the annulus of certain wells, such as wells having a low fluid level, and of equalizing the pressure between the tubing and the annulus is therefore highly desirable. In addition to controlling the relative pressures in the tubing and the annulus, it is highly desirable that such a tool also controls the fluid levels in the tubing and in the annulus during pressure changes. For example, when the pressure is reduced in the tubing, sudden fluid level surges within the tubing, possibly resulting in surface contamination, should be avoided. It is therefore an object of this invention to provide such a tool especially adapted for use in low fluid level wells.

A valve apparatus for use in a fluid transmission conduit, such as a tubing or work string, in a subterranean well, such as an oil or gas well, employs fluid pressure changes within the tubing to operate the valve. The valve employs a plug affixed within the bore of the valving apparatus to prevent the continuous flow of fluid through the bore of the valving apparatus in either direction. An annular fluid bypass communicable with the bore of the valving apparatus and of the well conduit above and below the plug provides a means of transmitting fluid through the conduit and valving apparatus when the valve is in the open position.

A shuttle valve shiftable relative to the centrally disposed plug opens and closes the fluid communication path between the fluid bypass and the bore of the valving apparatus on one side of the plug. For example, in the preferred embodiment of this invention, the shiftable shuttle valve opens and closes the fluid communication path below the plug. Fluid can then be injected through the upper fluid transmission conduit then through the annular fluid bypass and into the valve apparatus and fluid transmission conduit below the centrally disposed plug.

Normally, the shuttle valve in the preferred invention is spring biased to a closed position preventing the flow of fluids from the surface of the well to a subsurface location below the plug. In the preferred embodiment of this invention, the spring loaded shuttle valve includes a separate communication path or radial port permitting fluid communication between the annulus surrounding the valving apparatus and the tubing below the plug when the shuttle valve is in the closed position. Again in the peferred embodiment, actuation of the shuttle valve to move the valve to the open position also closes the radial path permitting pressure unloading or equalization between the lower tubing and the annulus. When pressure is reduced in the tubing string above the plug, the shuttle valve closes the fluid communication path through the tubing and again opens the radial port permitting communication between the annulus and the lower fluid transmission conduit. Not only will movement of the shuttle valve to the closed position permit fluid equalization between the annulus and tubing in a tool located below the valve, but any fluids tending to flow into the tubing below the valve are prevented from flowing up the tubing to the surface of the well. Such fluids can only pass into the annulus, where the pressure remains equalized, preventing any undesirable fluid loss and permitting the operator to maintain control and fluid and pressure integrity of the well. Such control is highly desirable for safe operation of the well.

FIG. 1 is a schematic elevational view of a valving apparatus involving this invention, shown in assembled relationship to a perforation washer and mounted within the casing of a well.

FIGS. 2A-2G collectively constitute an enlarged scale quarter sectional view of the apparatus shown in FIG. 1, with the elements thereof shown in their run-in positions.

FIGS. 3A-3G are views respectively similar to views 2A-2G but showing the elements of the apparatus in their operative positions when the packing elements of the perforation washer are expanded into engagement with the well casing.

The valving apparatus involving this invention may be employed for controlling the application of fluid pressure or the injection of fluids in a number of completions in a subterranean well. For example, fluid pressure may be applied to expandable packing elements disposed in an annulus defined between two concentric well conduits.

For simplicity, the invention will be described in connection with the control of fluid pressure to a conventional perforation washer 20 which is suspended on the end of the valving apparatus 10 and inserted within the well casing 1 by a tubular work string or fluid transmission conduit 3. These elements define an annulus 1a between the inner wall of the casing 1 and the outer wall of the interconnected apparatus including perforation washer 20, valving apparatus 10, and tubular work string 3.

Referring now to the enlarged scale drawings of FIGS. 2A-2G, the valving apparatus 10 will be seen to comprise a tubular body assemblage 100 formed by the threaded interconnection of an upper body element or mandrel 101, two intermediate body elements 111 and 121, and a lower body element 131. Mandrel 101 is provided with internal threads 102 for connection to the tubular work string 3 or any other suitable well conduit. Mandrel 101 is further provided on its medial portion with external threads 103 for threadably receiving the upper end of the intermediate body element 111. This threaded juncture is sealed by an O-ring seal 103a. Intermediate body member 111 is provided at its lower end with external threads 112 for threadable attachment to the top end of the lower intermediate body element 121. The bottom portion of the intermediate body element 121 is provided with external threads 122 for threadable connection to a lower body element 131. Body element 131 has threads 132 connecting to the top end of the perforation washer unit 20.

The medial portion of the mandrel 101 is further provided with a plurality of radial ports 104. At the extreme bottom end of the mandrel 101, a plug 106 is affixed to the mandrel. An upper annular elastomeric mass 107 of sealing material is mounted within a channel 106a adjacent plug 106. Both the plug 106 and the elastomeric mass 107 are secured to the bottom portion of the mandrel 101 by a retaining sleeve 108 which engages threads 101a provided on the upper tubular body portion 101. The upper elastomeric mass 107 will thus be seen to provide an annular, downwardly facing sealing surface 107a. An O-ring 106b seals the abutting end face connection between the plug 106 and the bottom end of the mandrel 101. Plug 106 prevents fluid from passing continuously through the bore of the mandrel 101 and the interconnected work string 3 in either axial direction. In the preferred embodiment of this invention, plug 106 is attached to mandrel 101. Of course the plug 106 could be secured within mandrel 101 by other means. For example, plug 106 could be secured by means of a conventional lock having dogs engaging cooperating nipple grooves on the interior of the mandrel bore. Conventional locks suitable for use in such an alternate embodiment would be capable of holding a suitable plug, such as a conventional tubing blanking plug against both upwardly and downwardly acting fluid pressure forces, just as plug 106.

The upper intermediate tubular body element 111 is spaced outwardly relative to the lower portions of the upper tubular body element 101 to define an annular fluid bypass 111a therebetween. Near the bottom of the threads 112, the intermediate tubular body element 111 is provided with an internally projecting shoulder portion 113 defining a cylindrical bearing surface 113a. As will be later described, this bearing surface 113a slidably cooperates with an external cylindrical bearing surface 50a provided on a tubular shuttle valve 50. An O-ring seal 113b effects a seal with the bearing surface 50a of the shuttle valve 50 so that a fluid pressure chamber is defined by annular fluid bypass 111a.

The lower end of the lower intermediate tubular body element 121 defines an internal cylindrical bearing surface 123 which slidably cooperates with the external cylindrical surface 51a of a sleeve 51 which is secured to the bottom end of the shuttle valve 50 in a manner to be hereinafter described. Additionally, the lower tubular body 121 is provided with axially spaced, radial ports 125 and 126 to maintain the annulus 124 between the exterior of the shuttle valve 50 and the interior bore surface 123 of the intermediate body element 121 at the same fluid pressure as the casing annulus 1a.

A sealing sleeve 117 is slidably mounted within the lower portion of the lower intermediate tubular body element 121 and is maintained in an upper position by a spring 118 acting against the bottom of the sealing sleeve 117 and an internal shoulder 133 defined just below the threads 122 providing the connection to the lower tubular body element 131. An enlarged shoulder 117a on sealing sleeve 117 cooperates with internally projecting, downwardly facing shoulder 121c provided on the intermediate tubular body element 121. The top portion of the sealing sleeve 117 defines an upstanding beaded ridge 117b which functions as a sealing surface and cooperates with an annular elastomeric mass 55 provided on the bottom of the shuttle valve 50, in a manner to be hereinafter described.

A first seal support sleeve 51 (FIG. 2C) is mounted around the lower portions of the tubular body of the shuttle valve 50 and is secured in the desired axial position by a C-ring 52. The first seal support sleeve 51 is provided with a lower externally threaded portion 51b which cooperates with internal threads provided on a second seal retainer sleeve 53. A third seal support sleeve 54 is sealably mounted on the bottom of shuttle valve 50 and sealed thereto by an O-ring 54a. The lower portions of sleeve 53 and 54 are shaped to define a recess for receiving the annular elastomeric sealing mass 55 and retaining such mass in position to be engaged by the upstanding sealing ridge 117b whenever the shuttle valve 50 is moved downwardly.

The upper end of the tubular shuttle valve 50 is provided with an enlarged counterbored portion 50b (FIG. 2B) and a sealing sleeve 56 is secured thereto by a set screw 57 and sealed to the counterbore by an O-ring seal 58. The sealing sleeve 56 is provided at its upper end with an upstanding annular ridge sealing member 56a which cooperates with the annular elastomeric mass 107 to achieve a sealing engagement therewith whenever the shuttle valve 50 is in its uppermost position, as illustrated in FIG. 2B. The outer upwardly facing surfaces of valve 50 and sleeve 56 constitute piston surfaces disposed in the annular fluid bypass 111a.

Shuttle 50 is resiliently biased to remain in its uppermost position by a helical spring 60 which surrounds the medial portion of the tubular shuttle valve 50 and abuts at its upper end against a ring 61 which in turn abuts against a downwardly facing shoulder 50c provided on the tubular shuttle valve 50. At its lower end, spring 60 abuts a ring 62 which is supported by a plurality of spacer rings 63. The number of spacer rings employed and the axial height of each depends upon the amount of pressure that is selected to maintain the shuttle valve in its closed upper position with respect to the downwardly facing elastomeric seal 107. Spacer rings 63 are in turn supported on an upwardly facing shoulder 121d provided on the intermediate tubular body portion 121.

As previously mentioned, the valving apparatus 10 embodying this invention is series connected between the tubular work string 3 and a downhole tool, such as a perforation washing tool 20. This invention may be advantageously employed in other applications including with any type of downhole tool wherein a fluid pressure actuated expandable packing element is expanded into sealing engagement across the annulus 1a. The washing tool 20 illustrated in the drawings is entirely conventional, and may, for example, comprise a Model C Packing Element Circulating Washer sold by Baker Service Tools Divisions of Baker Oil Tools, Inc. Accordingly, no detailed description of the construction of such tool will be made beyond pointing out the major components thereof.

Thus, the tool 20 comprises an outer hollow housing 201 on which are mounted a plurality of expandable elastomeric sealing elements 202, 203, 204, and 205. These elastomeric elements are concurrently axially compressed through the expansion of two telescopically related piston elements 210 and 211. Pressurized fluid for axially separating the piston elements 210 and 211 is supplied to a fluid pressure chamber 212 defined between the two telescopically related piston elements, through a radial port 213 which communicates with the hollow bore 20a of the washing tool 20, hence with the bore of the tubular housing assemblage 100.

Ordinarily, the elastomeric elements 202-205 are expanded through the introduction of fluid pressure into the bore 20a of the washing tool 20 in excess of the hydrostatic pressure existing in the casing annulus 1a. A suitable valve (not shown) is provided in the bore 20a below port 213. If the annulus 1a is filled with fluid, the hydrostatic pressure existing in such annulus will generally be the same as the hydrostatic pressure existing within the bore 20a. As the pressure in the bore 20a is increased, the increased fluid pressure is applied through port 213 to the fluid pressure chamber 212, thus separating the telescopically related pistons 210 and 211 to exert a compressing force on the expandable elastomeric elements 202-205. Thus, the elastomeric elements 202-205 are compressed and displaced radially to move into sealing engagement with the inner wall of the casing 1, as illustrated in FIGS. 3E, 3F, and 3G.

A conventional pressure relief valve 215 is provided in the wall of the housing tool 20 at a position adjacent the telescopically related pistons 210 and 211. In fact, the piston 211 is provided with an axial slot 211a (FIG. 2F) to receive the outer end of the pressure relief valve 215. Valve 215 is provided with a bleed passage 215a and is spring biased to a normally closed position. Upon a sufficient increase in fluid pressure after the setting of the expandable elastomeric elements 202-205, the pressure relief valve 215 will open and permit a large volume flow outwardly from the washing tool and through the selected set of perforations 1c in the casing wall 1 which is located between the innermost elastomeric sealing elements 203 and 204. Thus, a washing fluid can be injected through the perforations 1c into the fractures of the producing zone.

In a well where the hydrostatic casing annulus fluid pressure is equal to the hydrostatic pressure existing in the bore of the inner conduit, the washing operation can be discontinued and the elastomeric packing elements 202-205 released simply by terminating the application of the fluid pressure to the work string. However, in those wells having a low fluid level, it often happens that the hydrostatic fluid pressure of the column of fluid contained in the interconnected work string and wash tool is substantially in excess of the ambient hydrostatic pressure existing in the casing annulus. In such event, it is not possible to effect the release of the expansible elastomeric packing elements 202-205 merely through reduction of the fluid pressure in the work string. The valving apparatus 10 involving this invention is specifically directed to resolving this problem, and it operates in the manner hereinafter described.

During run-in of the interconnected washing apparatus 20, valving apparatus 10 and work string 3, fluid communication is maintained between the annulus surrounding the fluid transmission conduit, or work string 3 and the bore 20a below plug 106 through the open annular port defined between sealing sleeve 117 and seal 55. Fluid can be injected into the bore of the fluid transmission conduit, or work string 3, above the plug 106 so that the fluid pressure in the bore is generally equal to the hydrostatic pressure in the annulus and the pressure below plug 106. Shuttle valve 50 remains in the position shown in FIGS. 2B and 2C because of the action of spring 60.

When the washing apparatus 20 or other apparatus incorporating a fluid pressure expansible packing element is positioned at its desired downhole location, the elements of the apparatus will be in their positions shown in FIGS. 2A-2G. Fluid pressure above the plug 106 can then be increased at the well head and such increased fluid pressure flows outwardly through the radial port 104 into annular fluid bypass 111a. Such fluid pressure acts on the upwardly facing outer surfaces of the shuttle valve 50 and sleeve 56. There is a greater area of upwardly facing surfaces on such elements than downwardly facing surfaces exposed to the higher fluid pressure flowing into fluid bylass 111a. When fluid pressure in bypass 111a is increased sufficiently, the sleeve 56 and shuttle valve 50 are forced downwardly. Such downward movement against the action of spring 60 effects the opening of the sealing engagement between the upstanding annular sealing ridge 56a on shuttle valve 50 and the annular elastomeric mass 107, thus permitting the pressure fluid to flow within the bore of the tubular shuttle valve 50 below plug 106. Concurrently, the annular elastomeric mass 55 mounted on the bottom end of the shuttle valve 50 is moved into sealing engagement with the upstanding sealing ridge 117b provided in the lower portions of the lower intermediate body element 121. Thus the increased fluid pressure is applied through the bore of tubular shuttle valve 50 into the bore of the intermediate body element 121, thence, into the bore of the lower tubular body element 131 and into the bore 20a of the washing tool 20 to effect the expansion of the elastomeric packing elements 202-205 carried by the washing tool 20. The washing operation then proceeds in normal manner with an appropriate fluid.

At the conclusion of the washing operation, the fluid pressure is removed at the surface from the bore of the work string 3 and the fluid pressure in the valve apparatus 10 acting to maintain shuttle valve 50 in the position of FIGS. 3B and 3C, returns to the normal hydrostatic pressure represented by the column of fluid contained in the work string 3 and the interconnected valving apparatus 10. The effective downward force on sleeve element 56 and shuttle valve 50 is thus removed and hence the shuttle valve 50 returns to its uppermost position, as illustrated in FIG. 2B, wherein the annular sealing ridge 56a is in sealing engagement with the annular elastomeric mass 107. More importantly, an annular gap is concurrently opened between the lower annular elastomeric sealing element 55 and the upstanding sealing ridge 117b. This gap permits a ready flow of fluid contained within the interconnected bore of the valving apparatus 10 and the work string 3 below plug 106 through such gap, through the radial ports 126, and into the casing annulus 1a, thus equalizing the fluid pressure in the casing annulus with that existing in the bore of the interconnected washing apparatus below the plug 106. The pressure in the annulus acting on elastomeric packing elements 202-205 is thus equal to the pressure acting on pistons 210 and 211 acting to maintain the elements in their expanded configuration. This equalization of pressure permits the annular elastomeric packing elements 202-205 to contract through their normal resilience and return to their run-in positions illustrated in FIGS. 2E, 2F, and 2G. Plug 106 and shuttle valve 50 act as a back check valve to prevent any fluid surges through the bore of the fluid transmission conduit or work string which could cause problems at the surface. Fluid is instead diverted into the annulus.

It is therefore apparent that a valving apparatus embodying this invention provides a reliable supply of pressured fluid to any pressure actuated downhole tool disposed below the valving apparatus or for use in any downhole operation. At the same time, equalization of casing annulus pressure with the pressure contained in the bore below the plug and closed shuttle valve can be effected at any time that the fluid pressure in the interconnected work string, above the plug and shuttle valve, is sufficiently reduced.

Although the invention has been described in terms of specified embodiments which are set forth in detail, it should be understood that this is by illustration only and that the invention is not necessarily limited thereto, since alternative embodiments and operating techniques will become apparent to those skilled in the art in view of the disclosure. Accordingly, modifications are contemplated which can be made without departing from the spirit of the described invention.