US3472070A - Apparatus for controlling and method of testing well fluid production rate - Google Patents

Description

Oct. 14, 1969 D v, CHENQWETH 3,472,070

APPARATUS FOR CONTROLLING AND METHOD OF TESTING WELL FLUID PRODUCTION RATE TToQA/Eu.

Oct, 14, 1969 D. v. cHENowr-:TH 3,472,070

APPARATUS FOR CONTROLLING AND METHOD OF TESTING WELL FLUID PRODUCTION HATE Filed July 14, 1967 2 sheets-sheet 2 United States Patent O APPARATUS FOR CONTROLLDIG AND METHOD OF TESTING WELL FLUID PRODUCTION RATE David V. Chenoweth, Houston, Tex., assigner to Baker Oil Tools, Inc., City of Commerce, Calif., a corporation of California Filed July 14, 1967, Ser. No. 653,537 Int. Cl. E21b 47/10 U.S. Cl. 73-155 22 Claims ABSTRACT OF THE DISCLOSURE A constant fluid ow regulator for maintaining production flow from a well zone at a constant rate, and the method of testing the rate of production from each Zone of a multiple zone well produced through a single tubing string.

The present invention relates to subsurface well bore apparatus and methods, and more particularly to apparatus and methods for controlling the production of well fluid from productive subsurface zones.

In the production of multiple zone wells, it is sometimes necessary that the respective zones be produced at different rates, in which case it is the custom to employ various well ow control devices. Moreover, from time to time, it becomes necessary to ascertain the rate of production from the respective zones. The present invention involves apparatus useful in controlling the flow rate of well uid from one or more earth formations, and the method of simply shutting oif the flow from individual productive zones of the multiple zone well as a means for determining each zones relative contribution to the total Well eiuent.

Heretofore, various methods and means have been ernployed for ascertaining the relative contribution of selected zones to the total volume of well liuids being produced from multiple zone wells, which prior means and methods have required the running of equipment from the surface of the earth to blank off a selected productive zone, so as to determine the productive rate of the unblanked zone or zones. The use of such equipment is costly and time consuming.

An object of the present invention is to provide apparatus for controlling the rate of production of well fluids from a well zone, which is useful in the production of multiple zone wells to control the production from each of the zones at a selected rate, the apparatus including a constant rate flow regulator which automatically reacts to the tendency of the tubing pressure to vary, on the one hand, or for the formation iluid pressure to vary, on the other hand.

Still another object is the provision of a method involving the use of apparatus for controlling the rate of ow of well uids from a plurality of zones so that there may be readily obtained an indication of the contribution of each of the selected Zones to the total well fluid production.

More particularly, an object of the invention is to provide an upstream iiow regulator device comprising an orice and a throttle valve combined with piston means for selectively positioning the throttle valve, so that a constant pressure differential will exist across the orice, and, therefore, a constant rate of flow of fluid will pass through the orice.

Another object is to provide a oW regulator in accordance with the object next above, including a regulator spring acting to adjust the throttle valve in response to tendency of the pressure to change, and wherein a shutoif valve is also normally bias closed by the spring to shut off back ow through the regulator if such back flow ICC tends to occur, either by happenstance or by virtue of the purposeful production of a back pressure on the regulator greater than the characteristic zonal production pressure of the regulator.

More specifically, an object of the invention is to provide such a ow control device with a back ow preventing valve which is so related to the differential pressure responsive piston of the regulator that when the production iiuid pressure at the formation is less than the minimum pressure required to establish the constant rate regulatory action of the ow regulator, the regulator is maintained inoperative, thus eliminating from the operation of the regulator device any tendency to allow the passage of formation fluid therethrough unless the formation fiuid pressure is suiiicient to establish and maintain operation of the regulator device, on the one hand,

and the tendency of the apparatus to require the existence l of formation pressure in excess of that required to establish and maintain production rate regulation, on the other hand.

Still another object is to provide a method of determining the contribution of individual well zones to the total production of a multiple zone well by the utilization at each of the respective zones of a flow regulator device having a back o'w preventing valve means, and by increasing the back pressure on the Well production conduit leading from the multiple zones so as to successively shut off the flow of production uid from the zone having the least formation pressure, so that the remaining volume of production uid flow will be indicative of the total production from the remaining zones, and, therefore, the reduction in total production will be indicative of the rate of production of the shutoff zone. In this connection, it will be understood that the method has application to the determination of the production derived from two or more zones.

This invention possesses many other advantages and has other objects which may be made more clearly apparent from a consideration of a form and method embodying the invention. This form and method are shown and described in the present specification and in the drawings accompanying and constituting a part thereof. They will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best dened bythe appended claims.

Referring to the drawings:

FIGURE 1 is a View schematically illustrating well ow control apparatus useful in the practice of the present method installed in a well bore traversing multiple well zones;

FIGS. 2a and 2b are longitudinal sectional views, as taken on the line 2-2 of FIG. l, through the regulator apparatus at one of the zones, as illustrative of the apparatus at the respective Zones, FIG. 2b being a downward continuation of FIG. 2a;

FIG. 3 is a transverse sectional View as taken on the line 3 3 of FIG. 2a;

FIG. 4 is a transverse sectional view as taken on the line lll- 4 of FIG. 2a; and

FIG. 5 is a graphic illustration of the results of the practice of the method of the present invention.

Referring first to FIG. l, there is illustrated a well installation, including a well casing C set in a well bore, which traverses an upper well zone Z1 and a lower well zone Z2. At the Zone Z1, the casing has been perforated as by perforations P1, and at the zone Z2, the casing has been perforated as by perforations P2, so that well fluids from the respective zones may flow into the Well bore.`

The respective zones are isolated from one another within the casing by an upper well packer 1 above the zone Z1 and a lower well packer 2 between the zones Z1 and Z2. The packers 1 and 2 form no part of the present invention, but may be of any conventional type adapted to form a seal with the well casing, as well as to provide a seal with a length of production pipe or tubing T which extends into the well through the upper packer 1 so as to traverse that portion of the casing C communicating with the zone Z1, and through the packer 2 so as to be disposed effectively in communication with the zone Z2 within the casing C. Installed in the tubing string T within the isolated Zone defined between the packers 1 and 2 is a ilow regulator R, and a similar flow regulator R is installed in the tubing string in the isolated casing below the packer 2. It will be understood at this point that two subsurface well zones have been illustrated herein but the tubing T may extend through still additional zones, in each of which would be a similar regulator device, and each Zone would be isolated from the other by means of conventional packers in the casing C.

Each of the regulators R comprises a housing 3 having a production fluid inlet 4, whereby well fluids from the respective Zones may pass into the regulator, and thence through the tubing string to the earths surface, where the combined effluent will be conducted through suitable surface pipe 5 to a tank or other suitable reservoir for the well production fluids. At the surface, there is a control valve V whereby to maintain a variable and desired back pressure on the fluid in the tubing T flowing from the combined productive zones, so that, as will hereinafter more fully appear, the regulators R for the respective zones may be sequentially and individually cut out to prevent llow of production fluid from the respective zones. Such a procedure will enable a determination of the proportionate contribution of the respective zones to the total and combined well effluent flowing through the single tubing string T to the top of the well bore.

Illustratively, the regulator R may be combined with a valve device having means whereby the combined assembly may be run into and retrieved from the housing 3. Referring to FIGS. 2a and 2b, one of the combined valves and regulators is shown as illustrative of the assemblies which may be installed in the tubing string for control of the flow of well fluid from the respective zones. Such device includes an upper housing sub threadedly secured to a section of the tubing string T thereabove, this housing sub also being threadedly attached to the main housing 3 extending downwardly therefrom to a lower housing sub 17 to which it is threadedly attached, the lower housing sub, in turn, being threadedly attached to a lower section of the tubing string T. Within the housing 3 is a fixed sleeve 18 which cooperates with the housing 3 to form an annular space 19, this sleeve 18 being secured in spaced relation to the housing by a plurality of nipples 20 which are welded, or otherwise secured, to the housing and to the sleeve, these nipples providing a suitable number of the well fluid inlet ports 4 previously referred to, which ports establish communication between the annulus outside of the housing 3 and the interior of the fixed sleeve 18. A valve sleeve 21 is adapted to be disposed across the nipples, or, more particularly, across the inlets 4, to close the latter or to be shifted downwardly within the fixed sleeve so as to establish communication between the inlets 4 and ports 22 in the valve sleeve 21. The valve sleeve 21 comprises a lower imperforate portion 23 having suitable sealing engagement with the fixed sleeve on opposite sides of its ports 22.

The valve sleeve in FIG. 2a is shown in the open position, but it is movable upwardly to a position at which the inlet ports 4 will be closed. In this connection, the valve sleeve 21 has a plurality of circumferentially spaced upwardly extended spring-like latch arms 29 thereon having latch dogs 30 at their upper ends adapted to be received within an enlarged bore or circumferential groove 31 in the upper sub 15, these latch fingers being adapted to releasably latch the valve sleeve 21 in its upper port closing position. It will be understood that when the valve sleeve 21 is in such an upper position, the imperforate section 23 of the latter will close the inlet ports 4, the seal 24 on the valve sleeve 21 being disposed at one side of the inlets, and the valve sleeve being provided with another seal ring means 24a which will seal within the fixed sleeve 18 at the other side of the inlets 4.

In the illustrative embodiment, the valve sleeve 21 is shifted between its port opening and port closing positions by a retrievable flow regulator assembly which is adapted to be disposed in the housing 3 and latched therein so as to be removable therefrom when desired. The regulator assembly includes a mandrel or body 37 composed of a plurality of interconnected sections. The body includes an upper tubular lock section 38 having a peripheral groove 39 into which inner fingers 32 on the dogs 30 are shiftable. The lock section carries a suitable number of downwardly facing lock dogs 40 disposed in longitudinal grooves 41 in the mandrel and pivotally mounted on hinge pins 42. Each lock dog 40 is adapted to engage an upwardly facing shoulder 43 on the upper portion of the valve sleeve 21, being urged outwardly for engagement with the shoulder 43 by a suitable spring 45.

The mandrel or body section 38 also carries a suitable number of upwardly holding lock dogs 48 mounted in longitudinal grooves 49 in the mandrel on hinge pins 50 and urged outwardly by a suitable spring 51. When the valve sleeve 21 is in its lower, port opening position, as seen in FIG. 2a, the spring y51 will shift the lock dog 48 into the groove 31 of the housing sub 15, so as to engage in the same and prevent upward movement of the valve sleeve 21 from the port opening position.

The lower end of the section 38 of the mandrel 37 is threadedly secured to a port section S3 having a solid head 54 provided with a suitable upper seal 55 sealingly engaged with the inside wall of the valve sleeve 21. Below the head 54, the port section has a plurality of ports 57 communicating with the valve sleeve inlets 22, so that fluid may flow into a central passage S8 in the solid head and downwardly through its tubular section 59 which carries a suitable lower seal 58a sealingly engaged within the valve sleeve 21. Sealingly disposed about the tubular section 59 of the mandrel, and threadedly connected to the same as at 60, is a downwardly extended tubular regulator housing section 61. Within this regulator housing section 61 is regulator and shutoff valve means made in accordance with the invention.

It would be understood that the above-described valve assembly, including the valve sleeve 21, is merely illustrative of the means for supporting the regulator and shutoff valve mechanism now to be described within the housing 3, so as to provide inlet ports 4 leading into the regulator assembly through the central passage 58 of the mandrel of the regulator assembly. Moreover, the regulator assembly in the illustrative embodiment, as shown in FIG. 2a, may be run into and retrieved from the housing 3 on the mandrel 37 by means of a running and recovery wireline tool, as is well known in the art, which is adapted to engage with an enlarged flange 38a at the upper extremity of the mandrel section 38.

Referring now more particularly to FIG. 2b, it will be seen that the regulator housing 61 has at its lower end a fitting 62 threadedly connected thereto, as at 63, and providing an outlet port 64 through which fluid flowing downwardly through the mandrel passage 58 will emerge from the regulator under the proper flow conditions. Within the housing 61 and its lower end piece 62 are throttle valve means, generally denoted TV, and shutoff valve means, generally denoted SV, the operation of each of which valve means is under the influence of a common spring 65.

The throttle valve means TV includes a valve body 66 having an enlarged upper end section 67 fixed in the housing 61 by abutting engagement with a downwardly facing shoulder 68 in the housing 61, and by an upper abutment section 69 on the lower housing end piece 62. The valve body 66 includes a downwardly extended skirt 70 having side ports 71 therein, the lower end of the skirt 70 being closed by a suitable plug 72 sealed, as at 73, within the valve body and retained in place, as by means of a snap ring 74. In order to control the flow of fluid through the side ports 71, the throttle valve assembly also includes a valve sleeve 75, in the form of a tubular member, extended longitudinally in the regulator housing 61 and slidably disposed within the valve body 66, the lower end of the sleeve 75 being adapted to more or less open or close the side ports 71, depending upon the axial disposition of the sleeve 75 relative to the valve body. At its upper end in FIG. 2b, the valve sleeve 75 has an outwardly extended flange 76 against which one end of the spring 65 abuts, the other end of the spring 65 abutting with the upper end face 77 of the Valve body 66. Thus, there will be imposed on the Valve sleeve 75 a spring force normally tending to move the valve sleeve in a port opening direction.

Disposed within a central longitudinally extending flow passage 78 in the valve sleeve 75 is an orifice disc 79 having an orifice 80 therethrough, the orifice disc being retained in place by means of a snap ring 80a, and sealing means, such as seal ring 81, being provided to prevent the by-passing of fluid past the orifice disc 79. Above the flange 76, in the illustrative embodiment, the valve sleeve 75 is provided with ports 82 through which fluid may enter the central passage 78, as such fluid passes into the regulator housing 61 from the mandrel passage 58. At its upper extremity, the throttle valve sleeve 75 is provided `with a ball retainer 83 adapted to be engaged by a ball shutoff valve 84, the ball also being adapted to seat under the influence of spring 65 against a ball seat 85 at the lower extremity of the tubular mandrel section 59.

From the foregoing, it will be appreciated that the ball valve 84 is normally spring biased against the ball seat 85 so long as the effective force of the spring 65 and Iany hydraulic forces tending to cause back flow through the regulator assembly exceed the forces tending to move the ball valve off the seat 85, such latter force being derived from the production fluid pressure acting across the ball 84.

The structure as thus far described is more or less conventional, but in the present invention has been modified to accomplish particular novel results in the practice of the method hereinafter to be described.

More particularly, the shutoff ball valve 84 will be seen to have an effective seating area, designated A, engageable with the ball seat 85 at the lower extremity of the mandrel tubular member 59. In addition, the regulator mechanism may be seen to have a piston area, which is the effective annular end area of the valve sleeve 75 plus the annular area of the orifice member 79, which combined annular areas are designated B. In accordance with the present invention, the area of the ball valve S4 exposed to downward fluid pressure in passage 53 within the seat area of the seat 85, namely, the area A, is equal to the effective annular area of the valve sleeve '75 and the orifice disc 79, namely, area B. This equal area relationship has an advantage which will hereinafter be more fully apparent from a description of the mode of operation of the regulator mechanism.

In the operation of the regulator and assuming that the formation fluids are free to pass through the ports of the upper valve sleeve 21, such production fluid will pass downwardly through the mandrel passage 58, and, if pressure of the production fluid is of sufllcient magnitude, the ball valve 84 will be held olf its seat so that fluid will flow, as shown by the arrows, downwardly through the passage 78 in the valve sleeve 75, through the orifice 80, thence through the throttle valve ports 7l, and from the lower end piece 62 through port 64, upwardly through the annular space outside the regulator housing 61 and within the housing 3. Referring to FIG. 2a, it will be seen that fluid will then flow upwardly between the fixed sleeve 18 and the housing 3 through the annular space 19, and thence through a set of upper ports 22a in the valve sleeve 21 and through mandrel ports 37a into an axially extended passage 37b in the mandrel section 38, from which the fluid will pass into the upwardly extending tubing T.

The mode of operation of the regulator means is such that the rate of fluid flow through the assembly into the tubing T will be substantially constant, inasmuch as there will be maintained a constant pressure drop across the orifice 80. The maintenance of the constant pressure drop across the orifice is accomplished, inasmuch as any tendency of the formation pressure to increase will apply a greater force on the valve sleeve 75 by virtue of the action of the increased pressure across the effective area B tending to move the valve sleeve 75 downwardly, so as to shut off the throttle valve ports 71 to a greater extent, thereby increasing the back pressure on the orifice 80. The pressure difference across the orifice will be maintained as a function of the spring force derived from the spring 65, which may be adjusted to provide for the desired rate of production of well fluids from any given zone, such as the zone Z1 or the zone Z2, or some additional zone or zones. Conversely, should the formation pressure tend to decrease, then the spring 65, which normally tends to move the valve sleeve 75 in a port opening direction, will be effective to further open the throttle valve ports 71, allowing greater flow therethrough and a resultant reduction in back pressure on the orifice 80, so that the pressure difference through the orifice will be maintained constant.

Thus, it is now apparent that the regulator means has a constant rate mode of operation which is effective only when the formation pressure is sufllciently great as to cause a pressure difference across the combined shutoff Valve SV and throttle valve TV assembly as to cause a throttle Valve opening pressure acting on the annular area A productive of a force greater than the force of the spring 65 and tubing back pressure acting on area B. Therefore, inasmuch as the effective area A of the shutoff valve SV is the same as the effective annular area B, and when the shutoff valve is closed, the shutoff valve will remain closed until such time as there is a formation pressure in the passage 58 tending to unseat the ball 84 of sufficient magnitude as to cause the fixed rate mode of operation of the regulator means.

Referring again now to FIG. l and assuming that in each housing 3 of the respective regulator means R is an assembly, such as that shown in FIGS. 2a and 2b, there will now be described the method whereby a determination of the contribution of the respective zones to the total well eflluent may be determined without requiring, as heretofore, the running of equipment on wireline, whereby to remove regulator equipment and blank off production from selected Zones, so as to determine the productive rate of other zones.

In the present method, it will be understood that the combined well effluent from the several zones will be flowing to the earths surface through the tubing T, and that, while in the illustrative embodiment the regulator devices have been shown in a concentric tubing casing organization, the regulator means may also be disposed as is customary in tubing side pockets or in any other known installation, whereby the combined well effluent is flowing to the earths surface through a common conduit.

Each of the several productive zones under the control of a regulator means R, as previously described, will be producing fluid at a rate determined by the respective regulators, and each of the zones will be producing through the regulator at a characteristic regulated zonal pressure.

In order to determine the actual productive contribution of each zone with the present method, it is only necessaiy to build up a tubing back pressure which exceeds the characteristic pressure of the lowest pressure zone. The building up of tubing back pressure will, as previously indicated, create a force acting on the annular area B of the regulators in all of the zones, tending to move the respective regulator valve sleeves 75 upwardly, and when the upward force so derived exceeds the downward force of the formation pressure acting across the annular area B, then the shutoff valve SV will be closed, inasmuch as the upward movement of the valve sleeve 75 will cause movement of the ball valve 84 into engagement with the seat 85, thus shutting off further flow from that zone. By then determining the remainder of the total ow from the remaining zones, the contribution of the then shut off zone may be ascertained. If more than two zones are being produced through the common conduit or tubing T, as in the presently disclosed embodiment, then tubing back pressure may be progressively increased until the next lowest characteristic pressure zone will be shut off in the manner just described above, and the remainder of tlow from the remaining flowing zones will be indicative of the contribution of the zone which was last shut off, and so on through the entire plurality of zones being produced. The shutoff of each zone will, due to the equal areas A and B, be abrupt since the regulator will instantaneously cause closure of the shutoff valve when pressure acting on area A is exceeded by the back pressure on area B plus the force of spring 65.

The application of the method is graphically illustrated in FIG. 5, wherein the production rate is plotted against pressure. With reference to this graph, it will be noted that the greatest production rate is derived when all of the zones are producing into the common tubing string, but that when tubing pressure is increased to the point that the lowest pressure zone will cut out, then the production rate is the residual production from the highest pressure zone. This graph is representative of the two zones Z1 and Z2 of FIG. 1, but may be continued on through any number of productive zones until the highest pressure zone will cut out.

In addition, it will be understood that in the utilization of the present method, the regulator devices may be employed in wells in which artificial fluid lift is employed and that automatic equipment may be employed to peiiodically automatically effect zonal pressure shutoffs and record the result so as to maintain a log of the productive rate of the several zones of a multiple zone well installation, and then permit the respective zones to continue production.

I claim:

1. The method of producing well fluids from two or more well zones traversed by a well bore through a common production conduit having a flow regulator for each zone controlling the rate of production from said zone in accordance with the zonal pressure and the back pressure in said conduit, comprising increasing the back pressure in said conduit on all of said regulators to shut off a particular zone when the back pressure in the conduit has a characteristic relation to the zonal pressure of said particular zone, and measuring the production from the remaining one or more zones following shutoff of said particular zone to determine the production from said particular zone.

2. The method of claim 1, wherein the zones are shut off by first shutting off the zone of lowest zontal pressure, and then shutting off the zone or zones of progressively greater zonal pressure.

3. The method of claim 1, wherein said respective zones are progressively instantaneously shut off upon the application of back pressure in said conduit substantially equal to the zonal pressure of the respective zones.

4. The method of producing well fluids from a plurality of well zones traversed by a well bore through a common production conduit having a flow regulator for each zone controlling the rate of production from said zone in accordance with the zonal pressure and the back cs pressure in said conduit, comprising increasing the back pressure in said conduit on all of said regulators to progressively shut off the respective Zones when the back pressure in said conduit has a characteristic relationship to the zonal pressure of the respective zones, and measuring the production from the remaining zones following shutoff of a zone to determine the production from the shutoff Zone or zones.

5. The method of claim 4, wherein the respective zones are shut off by first shutting off the zone of lowest zonal pressure, and then shutting off the zone or zones of progressively greater zonal pressure.

6. The method of claim 4, wherein said respective zones are progressively instantaneously shut off upon the application of back pressure in said conduit substantially equalling the zonal pressure of the respective zones.

7. The method of producing well fluids from a plurality of well zones traversed by a well bore through a common production conduit having a flow regulator for controlling the rate of production from said zone in accordance with the zonal pressure and the back pressure in said conduit, comprising periodically increasing the back pressure in said conduit to shut off the production of fluid from the respective zones progressively and at spaced intervals, measuring the remaining production following shutoff of each zone to determine the contribution of each of the zones to the total well effluent in said conduit, and then progressively reducing the back pressure in said conduit and allowing the respective zones to resume production.

8. In flow regulating apparatus adapted to be installed in a conduit: a body having an inlet and an outlet, a flow passage leading through said body from said inlet to said outlet, regulator means for controlling the ow of fluid through said flow passage including a restriction of fixed effective flow area in said iiow passage, throttle valve means including a member movable to increase and decrease the `back pressure on said restriction, means for moving said member in response to pressure changes upstream and downstream of said restriction to maintain a substantially constant pressure drop through said restriction, and shutoff valve means operable to close said ow passage when back pressure on said restriction prevents the maintenance of a constant pressure drop across said restriction.

9. In apparatus as defined in claim 8; wherein said throttle valve means is downstream of said restriction.

10. In flow regulating apparatus adapted to be installed in a conduit: a body having an inlet and an outlet, a flow passage leading through said body from said inlet to said outlet, regulator means for controlling the flow of fluid through said flow passage including a restriction in said flow passage, throttle valve means including a member movable to increase and decrease the back pressure on said restriction, means for moving said member in response to pressure changes upstream and downstream of said restriction to maintain a substantially constant pressure drop through said restriction, and shutoff valve means operable to close said flow passage when back pressure on said restriction prevents the maintenance of a constant pressure drop across said restriction, wherein said shutoff valve means comprises a shutoff valve movable by said throttle valve member, a shutoff valve seat in said flow passage, said means for moving said throttle valve member comprising a fluid pressure responsive area on said member downstream from said restriction, and said shutoff valve and said seat having a seating area exposed to pressure in said ow passage equal to said fluid pressure responsive area of said means for moving said throttle valve member.

11. Apparatus as defined in claim l0, and spring means acting on said throttle valve member and normally biasing said shutoff valve means against said seat.

12. In a. flow regulating apparatus adapted to be disposed in a conduit: a housing having an inlet and an outlet, a fiow passage leading through said housing from said inlet to said outlet, means in said fiow passage forming a restriction for reducing the pressure of fiuid owing through said fiow passage, throttle valve means in said fiow passage including a valve passage at one side of said restriction, a valve member movable relative to said valve passage to control the fiow therethrough, means for moving said valve member in opposite directions including `a spring biasing said member in one direction and an area on said member exposed to fiuid pressure for moving said member in the other direction, a shutoff valve seat on the other side of said restriction, and a shutoff valve movable by said Valve member into engagement with said seat and movable by fiuid in said flow passage off said seat, said shutoff valve seat and shutoff valve having a seating area equal to the pressure responsive area of said throttle valve member.

13. Apparatus as defined in claim 12, wherein said,

throttle valve member comprises a tubular member, said fiow passage extending through said tubular member, and said restriction comprises an orifice in said tubular member.

14. Apparatus as defined in claim 12, wherein said throttle valve member comprises a tubular member, said fiow passage extending through said tubular member, said restriction comprising an orifice in said tubular member, and said shutoff valve comprising a ball valve engaged by said tubular member.

15. Apparatus as defined in claim 12, wherein said throttle valve member comprises a tubular member, said fiow passage extending through said tubular member, said restriction comprising an orifice in said tubular member, and said shutoff valve comprising a ball valve engaged by said tubular member, said spring being a coiled spring disposed about said tubular member, said tubular member having a seat engaged by said spring.

16. Apparatus as defined in claim 12, wherein said throttle valve means comprises a valve body having a side port, and a valve sleeve in said body movable by said valve member in port opening and port closing directions.

17. Apparatus as defined in claim 12, wherein said throttle valve means comprises a valve body having a side port, a valve sleeve in said body movable by said valve member in port opening and port closing directions, and said means forming a restriction comprises an orifice disc in said sleeve upstream from said side port.

18. Apparatus as defined in claim 12, wherein said throttle valve means comprises a valve body having a side port, a valve sleeve in said body movable by said valve member in port opening and port closing directions, and said means forming a restriction comprises an orifice disc in said sleeve upstream from said side port, said pressure responsive area of said movable valve member comprising the annular area of said sleeve and said orifice disc.

19. In apparatus for conducting fiuid between a plurality of longitudinally spaced production zones and the top of a well bore: a tubing string in the Well bore, packing means set in the well bore in sealed relation to said tubing string to isolate the production Zones from one another, regulator means in said tubing string and communicating with each zone for controlling the fiow of fluid from each zone including a housing having an inlet communicating with its zone and an outlet communicating with said tubing, a fiow passage extended through said housing between said inlet and said outlet, a restriction in said fiow passage, throttle valve means including a member movable to increase and decrease the back pressure on said restriction, means for moving said member in response to pressure changes upstream and downstream of said restriction to maintain a substantially constant pressure drop through said restriction, and shutoff valve means upstream from said restriction operable to close said fiow passage when back pressure on said restriction prevents the maintenance of a constant pressure drop across said restriction.

20. Apparatus as defined in claim 19, wherein said shutoff valve means comprises a shutoff valve movable by said throttle valve member, a shutoff valve seat in said fiow passage, said means for moving said throttle valve member comprising a fiuid pressure responsive area on said member downstream from said restriction, and said shuto valve and said seat having a seating area exposed to pressure in said fiow passage equal to said fiuid pressure responsive area of said means for moving s-aid throttle valve member.

2l. Apparatus as defined in claim 19, wherein said shutoff valve means comprises a shutoff valve movable by said throttle valve member, a shutoff valve seat in said fiow passage, said means for moving said throttle valve member comprising a fiuid pressure responsive area on said member downstream from said restriction, said shutoff valve and said seat having a seating area exposed to pressure in said fiow passage equal to said fiuid pressure responsive area of said means for moving said throttle valve member, and spring means acting on said throttle valve member and normally biasing said shutoff valve means against said seat.

22. In fiow regulating apparatus adapted to be disposed in a conduit: a housing having an inlet and an outv let, a fiow passage leading through said housing from said inlet to said outlet, means in said fiow passage forming a restriction for reducing the pressure of fluid fiowing through said fiow passage, throttle valve means in said fiow passage includinga valve passage at one side of said restriction, a valve member movable relative to said valve passage to control the fiow therethrough, means for moving said valve member in opposite directions including a spring biasing said member in one direction and an area on said member exposed to fluid pressure for moving said member in the other direction, a shutoff valve seat on the other side of said restriction, and a shutoff valve movable by said valve member into engagement With said seat and movable by fiuid in said flow passage off said seat, said shutoff valve seat and shutoff valve having a seating area equal to the pressure responsive area of said throttle valve member.

References Cited UNITED STATES PATENTS 2,668,555 2/1954 Bartolat 137-498 2,839,144 6/1958 Ault 166-224 X 3,045,759 7/1962 Garrett et al. 166-224 3,122,162 2/1964 Sands 13'7-498 RICHARD C. QUEISSER, Primary Examiner I. W. MYRACLE, Assistant Examiner U.S. Cl. X.R. 166-224; 137-498

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