Abstract:
The invention provides a high flow rate standing valve for oil wells of the type employing a plurality of check valve units disposed in parallel between inlet and outlet passages, the flow area of the inlet or outlet passage each being not in excess of the total flow areas of the individual check valves so that no significant pressure drop is produced by fluid flow through the check valves in their open position. Specifically, the invention provides an improved configuration for such standing valves permitting the convenient manufacture and assembly of the valve components. In a modification of the invention, the standing valve housing is constructed so that its lower end is mounted on and co-operates with a conventional well safety valve.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention: 
     The invention relates to standing valves of the type employed in the bottom of a submersible pumping apparatus for an oil well which prevents reverse fluid flow from the production casing back into the well whenever the pumping operation is interrupted or the pumping apparatus is removed from the well for servicing. 
     2. Description of the Prior Art: 
     This invention constitutes an improvement over the standing valve construction disclosed and claimed in co-pending application Ser. No. 50,921, filed June 21, 1979, entitled &#34;High Flow Check Valve Apparatus&#34; assigned to the same assignee as this application. Such co-pending application discloses a standing valve for oil wells wherein a plurality of check valve units are provided between two laterally spaced, parallel inlet and outlet passages. While the construction disclosed in said aforementioned co-pending application is completely functional to minimize the pressure drop involved in a standing valve when the check valves are in their open or flowing position, the disclosed construction required relatively complicated components which would only be produced by castings and complex machining operations. To reduce the manufacturing cost of this type of standing valve apparatus, and to simplify the assembly and servicing of the valve, it is desirable that the great majority of components of the standing valve be capable of being produced by simple machining operations. For example, it is desirable that all of the major fluid flow passages in the standing valve be defined by drilled holes in the main housing element, rather than by cast apertures. 
     Additionally, it is desirable that the standing valve be capable of being mounted directly adjacent to a tubing controlled sub-surface safety valve, which is now being required for installation in many wells, particularly oil wells drilled in the ocean floor. 
     SUMMARY OF THE INVENTION 
     This invention provides an improved construction of a standing valve for an oil well wherein the main housing element of the valve comprises a generally cylindrical housing and all of the plurality of check valve units of the valve are mounted in vertically stacked relationship within one of three longitudinally extending bores machined in such housing. The other two bores respectively define a fluid flow inlet passage and a fluid flow outlet passage of the check valve units of the standing valve. 
     In accordance with a modification of the invention, the lower end of the standing valve is constructed in such manner to be mounted immediately adjacent to a tubing controlled, subsurface safety valve to place the safety valve in an open condition whenever the standing valve is installed thereon, or may be installed in a casing installation where all of the production from the well passes through an extension which communicates with the production tubing. 
     Other objects and advantages of this invention will be apparent to those skilled in the art from the following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 comprises an end elevational view of a standing valve housing constructed in accordance with this invention. 
     FIG. 2 constitutes a composite multi-plane sectional view taken on the planes A--A and B--B of FIG. 1. 
     FIG. 3 is a view similar to FIG. 2, but showing a modification of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, it should be first explained that the scale of all figures of the drawing is the same, but the sectional views of FIGS. 2 and 3 are larger than the elevational end view of FIG. 1 due to the fact that these figures constitute a composite of two sectional views taken on two different planes. 
     A standing valve constructed in accordance with this invention comprises a cylindrically shaped housing 10 having a tapered bottom end portion 10a and a flat top end portion 10b. Three longitudinally extending bores are provided in housing 10, preferably by a drilling operation, comprising a large diameter primary bore 11, a smaller diameter inlet bore 12 and an outlet bore 13. These three bores are preferably disposed in generally triangular relationship in a horizontal plane in order to permit the diameter of the housing 10 to be maintained small enough to be readily insertable within the casing of an oil well. 
     Inlet bore 12 extends upwardly from the tapered bottom surface 10a partially through the length of housing 10, terminating in a reduced diameter end passage 12a which communicates with a radial port 12b which in turn communicates with an annular recess 11b provided in the wall of primary bore 11 for the purpose to be hereinafter described. Additional radial ports 12c and 12d communicate respectively between inlet bore 12 and annular recesses 11c and 11d in the wall of primary bore 11. 
     The outlet bore 13 extends from the top surface 10b of housing 10 downwardly through substantially the entire length of housing 10 but terminates short of the bottom of housing 10. The top end of outlet bore 13 is closed by a threaded plug 13a. The outlet bore 13 is provided with a plurality of vertically spaced, radial ports 13e, 13f and 13g communicating respectively with annular recesses 11e, 11f, and 11g provided in the walls of the primary bore 11 for purposes to be hereinafter described. 
     The bottom end of primary bore 11 is provided with threads 11h which receive the threaded end of a tubular extension 14 which extends into the production zone of the well casing to receive the incoming well fluid. A locking sleeve 14a effects the securement of extension 14 to the housing 10. 
     A valve unit mounting sleeve 15 is inserted within the primary bore 11 and rests upon the top end of the extension sleeve 14. The sleeve 15 extends almost to the top of the bore 11. Just below its top portion, the sleeve 15 defines an upwardly facing shoulder 15a which provides a vertical support and seal for a flange 16a provided on an annular support bushing 16. The top surface of the support bushing 16 is provided with an upward taper 16b which effects a sealed engagement with the correspondingly tapered end 5a of a pump inlet casing 5. The support bushing 16 has a threaded annular bottom portion 16c to which is threadably secured to a tubular spacer member 17. Spacer member 17 has an internally threaded bottom portion 17a to which is threadably secured the first of a series of axially stacked check valve units 8 comprising threadably connected, identical valve chamber housings 18 each of which is successively threaded to an adjacent housing by threaded end portions 18a and 18b. The lowermost valve housing 18 has a threaded bushing 19 secured to its lower threaded end portion 18b. 
     The other components of each check valve 8, such as the valve seat 20, a check valve member 21, in this case illustrated as being a ball, a ball guiding cage 22, and a ball holding magnet 23 are identically mounted in each of the valve chambers respectively defined by the housings 18 and hence only one of such check valve units will be described. 
     Each check valve unit 8 comprises an annular valve seat 20 which is supported by the top end 18a of the next adjacent valve chamber housing 18 (or by a bushing 19 for the bottom unit). The check valve member 21 normally rests on seat 20 and thereby prevents fluid flow downwardly through the valve chamber housing 18. When the upward fluid pressure on the ball valve member 21 is sufficient to lift it off its seat, it is guided in its upward movements by the articulated annular cage 22 mounted above the seat 20 until the ball contacts the restraining magnet 23 which is suitably mounted on a spider-shaped support 24 extending across the valve chamber and held between the cage 22 and an internal shoulder 18d on housing 18 (or shoulder 17b in the case of the top unit). The provision of magnet 23 effectively prevents chattering of the ball valve and insures that it will positively move between its open and closed positions when sufficient pressure differentials exist. 
     Employment of a ball as the check valve member is only illustrative and a poppet type valve could be substituted therefor. 
     The fluid flow through each of the valve chambers is therefore limited by the annular area that exists between the ball valve 21 and its annular cage 22 when the ball valve is in its open position. In accordance with this invention, the effective flow area of the inlet fluid bore 12 and the outlet fluid bore 13 is not in excess of the sum of the individual fluid flow areas of the various check valves 8 which interconnect such inlet and outlet bores. Thus, to achieve any desired pumping volume, it is only necessary to provide a sufficient number of check valve units 8 disposed in parallel between the inlet bore 12 and the outlet bore 13 to provide sufficient flow area to reduce the fluid pressure drop across such valves to a minimum. 
     The fluid connections of the inlet bore 12 and the outlet bore 13 will now be described. In the modification of FIG. 2, the bottom end of inlet bore 12 is exposed to fluids entering the well casing which are drawn upwardly into the valving apparatus by the suction action exerted by the pump (not shown). 
     The radial ports 12c and 12d respectively permit the fluid to flow from the inlet bore 12 into the primary bore annular recesses 11c and 11d respectively, thence through a plurality of ports 15c and 15d in mounting sleeve 15, thence into the adjacent valve chamber of a check valve unit 8 through a series of radial ports 18e provided in the wall of the valve chamber housing 18. Immediately above the magnet supporting spider 24, the valve chamber housing 18 is provided with a plurality of spaced radial ports 18f which communicate with an annular recess 18g, thence through ports 15e and 15f of the mounting sleeve 15 respectively which communicate with the annular recesses 11e and 11f provided in the wall of the primary bore 11, and thence through radial ports 13e and 13f respectively to the outlet bore 13. 
     The fluid flowing up through outlet bore 13 passes through the radial port 13g at the top end of bore 13 into the annular recess 11g in the primary bore 11, through a plurality of ports 15g in the mounting sleeve 15, and then through radial ports 17g provided in the spacer sleeve 17 to the interior bore 16d of the support bushing 16 and then into the pump inlet 5. 
     In accordance with this invention, the fluid flow through the check valve units at the top and bottom of the stack of units 8 may be simplified. For example, the bottom check valve unit 8 has a direct fluid inlet to its chamber from the bore of the extension 14 and then discharges as described above through ports 18f in the valve chamber housing 18, the annular recess 18g, a plurality of ports 15e in mounting sleeve 15, annular recess 11e  and a radial port 13e communicating with the outlet bore 13. At the top of the stack of check valve units 8, the inlet to the top check valve unit 8 from inlet bore 12 is the same as previously described; however, the outlet passage is provided by a direct connection of openings 24a in the magnet support spider 24 with the bore of the spacer member 17. 
     Referring now to FIG. 3 there is shown a modified end configuration of the standing valve apparatus of FIGS. 1 and 2 to permit the standing valve to be mounted directly upon a tubing controlled sub-surface safety valve unit 30 which is customarily provided with an upstanding annular nipple 31 within which a slidable actuator sleeve 32 is mounted. Such safety valves are well known and are commercially available from a number of sources. Typical of such safety valves are those as disclosed in: U.S. Pat. No. 3,797,573, issued Mar. 19, 1974, entitled &#34;Full Opening Safety Valve&#34;, Talmadge L. Crowe, Inventor; U.S. Pat. No. 3,896,876, issued July 29, 1975, entitled &#34;Subsurface Tubing Safety Valve with Auxiliary Operating Means&#34;, Talmadge L. Crowe, Inventor; and U.S. Pat. No. 3,868,995, issued Mar. 4, 1975, entitled &#34;Sub-Surface Safety Valve&#34;, Talmadge L. Crowe, Inventor. In this configuration, the housing 10&#39; is elongated to extend below the axial inlet of the lowermost check valve unit 8. Instead of the axial inlet bore 12&#39; extending downwardly through the tapered lower surface of housing 10&#39;, it is provided with a plug 10e&#39;. Fluid communication is then provided to the inlet bore 12&#39; by a radial port 11a&#39; formed in the wall of the primary bore 11 and port 14c&#39; provided in extension 14&#39;. The bottom end of extension 14&#39; is threaded within the nipple 31 when mounting the standing valve unit on the safety valve 30 and depresses the actuator 32 to shift the safety valve to its open position. 
     It occasionally becomes necessary to remove a standing valve from a well for servicing, or to remove any accumulation of sand from the valve components. This may be accomplished in conventional fashion through the provision of knock-out plugs 33 which are threaded into the walls of the spacer sleeve 17 and lie inwardly thereof in a position to be engaged by a wire line tool and knocked loose, thus providing radial openings to permit the fluid contained in the interconnected production tubing and pump above the standing valve to drain through such openings into an annular space 16e provided between the spacer sleeve 16 and the interior wall of the mounting sleeve 15. A plurality of radial ports 15h in mounting sleeve 15 provide communication with the annular recess 11b provided in primary bore 11 and such recess is connected by radial port 12b to the end passage 12a of the inlet bore 12 to drain into the well casing. 
     Conventional seals, such as O-rings, are provided wherever required to prevent fluid leakage from the described paths through the standing valve apparatus, and such seals will not be described in detail. 
     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.