US2227538A

US2227538A - Apparatus for flowing wells

Info

Publication number: US2227538A
Application number: US272503A
Authority: US
Inventors: Harvey T Dorton
Original assignee: Individual
Current assignee: Individual
Priority date: 1939-05-08
Filing date: 1939-05-08
Publication date: 1941-01-07
Anticipated expiration: 1958-01-07

Description

Jan. 7,` 1941.

H. T. noRToN APPARATUS FOR FLOWING WELLS Filed May 8, 1939 2 sheets-sheet 1` ln/vendor,

43;. vlinnn/e311 arfom.

Jan. 7, 1941. H. T. DoRToN APPARATUS FOR FLOWING WELLS Filed May 8A, 1939 2 Sheets-Sheet 2 Hafvcy l' Dorfnia.

@ @mmMa/m Je@ atented Jan. 7., 1941 llllarvey "lll. Morton, li/fartha, y..

application li/liay d, ibid, serial ltTo. 2272503 i5 iUllaims. (mi ldd-2i 'llhis invention relates tothe control of fluid flow in gas and oil wells, and more particularly to methods and apparatus for controlling the injection of gas or other fluid into an oil producing sand for the purpose of artificially stimulating the recovery of oil therefrom, and for controlling the flow ot gas or oil from a producing well whenever it is desired to operate the well at less than its maximum capacity.

lin repressuring oil producing sands by the injection of gas from a pressure well, it has been found that the permeability of the sand varies greatly at different points in the same pool, as well as in different strata, and that a materially different pressure may be required for the injection of the desired volume of gas into one pressure well or stratum than is required for another. inasmuch as it would not be economical to maintain a series of gas compressors or reser-l voirs discharging at different pressures into a multitude oi' pipe lines connecting to all of the pressure wells in any one field, lt has heretofore been the practice to control the pressure of the gas injected by the use of pressure reducing restrictions in the pipe lines at each well.

it has been found, however, that when such restrictions are installed at the well heads, it is practically impossible to maintain a continuous flow of gas into a well when the atmospheric temperature is at or near freezing, without the application of heat in some form, because the expansion of the gas in passing through a flow restricting oriiice reduces its temperature to a point where any liquid entrained in the gas or otherwise present at the orifice quiclrly freezes and clogs the latter. To avoid this difficulty, it has been proposed to install such restrictions in the well tubing at points sufficiently far below the surface of the ground to insure that the temperature of the expanded gas remains above freezing. The difficulty with this arrangement, however, is that whenever it becomes necessary to change the size of a restricting orificeand this is a more or less frequent occurrence because of the continually changing conditions in the sand during Well operation-either the entire tubing string must be removed from the well to enable replacement of the orifice fitting, or the latter must be elevated inside the tubing and another fitting lowered into place by the use of suitable tools. Both of these proce-dures are time consuming and occasion the loss of substantial quantities of gas because of the necessity `for blowing down the Well each time that the orifice htting is changed.

ll/liuch the same situation as that described above has also existed in connection with edorts to restrictively control the 'flow of gas from a producing well, and substantially the same defects are inherent in the methods and means that have been previously employed for this purpose. Somewhat similar problems are involved in restricting the production of an oil well, be cause of the desirability from the standpoint of efficiency of locating the flow restricting means at or near the face of the producing sand.

lit is therefore one of the objects of the present invention to provide new and improved pro-l cedures and apparatus for controlling the flow of iiuids in gas and oil wells which will overcome the diiiiculties and remedy the detects heretofore encountered and existing in the methods and. means previously available to the art for attainlng the same ultimate results.

another object is to provide novel and simplii'led means for restricting the flow of fluid into or out of a gas or oil well at points located substantial distances below the surface of the ground, and for readily varying from the well head the restrictive elfect of such means.

d. further object is to provide a new method for varying the size of a flow restricting orihce lin the tubing string of a pressure or producing well which does not reduire either the use of tools for placing and removing the orince iitting or the removal of the 'tubing string from the well.

Still another object is to provide a device for controlling the flow of fluid upwardly or downwardly in the tubing of a gas or oil well which can be quickly and easily positioned at and removed from a point far below. the well head by gravity and fluid pressure alone. n

d still further object is to provide a novel method and apparatus of the character described which are capable oi effecting substantial savings iu the cost of oil and gas well operations wherein it is necessary to restrictively control the flow of fluid to or from the well.

These and other objects will appear more fully upon a consideration of the detailedldescription of the embodiments of the invention which follows. although three specific forms of apparatus embodying the present invention are described and illustrated in the accompanying drawings, it is to be expressly understood that these drawings are for the purpose of illustration only and are not to be construed as defining the limits of the invention, reference being had for this latter purpose to the appended claims.

Referring now to the drawings, wherein like reference characters indicate like parts throughout the several views:

Fig. 1 is a vertical section, with certain elements shown in full and others broken away in the interest of clarity, of one arrangement of apparatus embodying the present invention adapted for controlling the flow of gas or other fluid into a pressure well for the purpose of artificially stimulating the recovery of oil from producing wells in the same field by injecting fluid under pressure into the oil producing sand;

Fig. 2 is a vertical sectional view, similar to Fig. 1, of a second embodiment of the invention especially adapted for use in an oil or gas producing well;

Fig. 3 is a vertical sectional view of a modification of the embodiment shown in Fig. 2; and

Figs. 4, 5 and 6 are fragmentary vertical sections, on an enlarged scale, of the flow restricting orifice fittings of Figs. l, 2 and 3, respectively.

In each of the three embodimei ts of the invention illustrated, the apparatus disclosed is adapted to restrictively control the flow of a fluid into or out of a string of tubing through an orifice located a sufficient distance below the surface of the ground to insure against the existence of freezing temperatures at the orifice, and includes an element, hereinafter referred to as an orifice Plug, which determines the size of the flow restricting orifice and is capable of being lowered to and raised from the point of control by means of gravity and fluid pressure alone. In each instance, the lower end of the tubing string in which the restriction is required is provided with a fitting forming a seat for the orifice plug and embodying an orifice of fixed maximum size, the effective size of which is varied by the orifice plug, while the upper end of the well tubing is provided with a suitable arrangement of valves, pipe connections and other means by which the orice plug may be raised from and lowered to its seat without the use of fishing or other tools.

Referring now more particularly to the embodiment illustrated in Figs. 1 and 4, there is 'indicated therein a pressure well containing a main string of tubing I2 which is adapted to extend downwardly to the stratum into which the repressuring fluid is to be injected, and a secondary pipe or tubing string I3, in this in stance located inside of main tubing string I2, by means of which the fluid is delivered to the main string I2 at a predetermined reduced pressure.

To this end, the lower end of secondary tubing string I3 has threaded thereto a fitting |4 having an orifice I5 in its bottom and a tapered seat I6 leading to said orifice. The orifice I5 is of such size that, when unrestricted, it will pass fluid from the interior of tubing string I3 to main.

string I2 at the maximum pressure which it might be desired to inject into the well. In order to insure against clogging due to freezing, the fitting I4 is preferably located at least one hundred feet below the ground level at the well head, although, of course, the exact location of this fitting in any particular well may be selected to suit operating conditions.

In order to suitably restrict the flow through orifice I5 of the gas or other fluid used for injection, an orifice plug I'I is removably associated with the tapered seat I6, the orifice plug of the embodiment illustrated being generally cylindrical in form and having its bottom end tapered as indicated at I8 to make a tight fit with tapered seat I6 and a vertical bore |9 of restricted diameter extending therethrough, the size of the bore I9 being properly proportioned to pass fluid at the desired rate and with the desired amount of expansion. It should also be noted that the bore I9 is of smaller diameter than orifice I5, a condition which ls essential t0 the operativeness of the method and apparatus of the present invention when apertured plugs are employed. 'I'he upper end of plug l1 is also preferably rounded or tapered as indicated at 20 so that the plug will pass freely upwardly through tubing string |3 without hanging when elevated in the manner later to be described. As will be seen best from Fig. 4, orifice plug is maintained in engagement with seat I6 by gravity and fluid pressure alone, the tapered surfaces of the plug and seat being accurately ground and formed of non-corrosive materials so as to insure at all times a tight, but non-sticking, joint between these two elements.

At the well head the two strings of tubing I2 and I3 are connected together for support, and t0 a control pipe 2| which communicates with the interior of secondary tubing string I3, by means of a special coupling 22. As shown in Fig. 1, this coupling comprises a flange 23 suitably secured to the upper endof main tubing string I2, a nipple 24 into which the upper end of secondary string I3 is threaded and which is provided with a flange 25 of smaller diameter than flange 23, another flange 26 complementary to flange 23 suitably secured to the lower end of control pipe 2|, and a pair of gaskets 2'I, the flange 25 of nipple 24 being clamped between

flanges

23 and 26, with the gaskets 21 intervening, by means of bolts 28. With this form of coupling, the secondary tubing string I3 does not have to be turned and can be run inside the mainI string I2 without the risk of lapping them together in setting up the pipe at the surface. Since the main tubing string I2 is sealed at the top by the coupling 22, it may be provided, if desired, with a take-off line 29 just below the coupling and a valve 30 of any suitable construction for controlling the flow in said line. When the apparatus shown in Fig. l is used for pressure well operation, it will be understood that valve 30 is normally closed so as to prevent the escape of the repressuring fluid at the top of the main tubing string.

In order to attain the desired objective of raising and lowering the orifice plug I'I from the well head without the use of tools, control pipe 2| is provided with a novel arrangement of valves and other connections which are capable of manipulation in such manner that the orifice plug can be dropped downwardly to its seat I6 through secondary tubing string I3 by gravity and elevated therefrom by the pressure of the fluid in the well.

In the embodiment illustrated, there is connected to control pipe 2| an inlet line 3| leading to any suitable source of relatively high pressure injection fluid, such as a compressor or reservoir (not shown), the flow of iiuid from said source into control pipe 2| being controlled lby a suitable valve 32. It will be understood thatthe pressure of the fluid in inlet line' 3| is the maximum that would ever be required for operation of the well, and that this pressure is reduced as required by passing the fluid through the restricted bore I9 of an orifice plug I1. In order that the desired pressure reduction may be obtained for any particular operating condition, a plurality of oriiice plugs are provided for use with each installation, these plugs being identical in construction except that the restricted bores thereof are made oi different diameters so as to provide different degrees of resistance to the flow of fluid fj therethrough.

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.through secondary tubing string reaches oriiice plug il'.

Control pipe ll is also provided with a pair of gate valves and it, valve 33 being located between coupling il and inlet line tl, while valve is positioned at the upper end of the control pipe and serves to open the latter to the atmosphere. The body oi upper or release valve ill is suitably constructed at its outlet side to receive the threaded open end oi a cushioning cage member it which is substantially cylindrical in iorm, closed at its upper end, and provided with a plurality ci periorations wlrich permit the escape oi gas or other fluid from the interior thereof tothe atmosphere. rlhe inner diameters oi cage member it and control pipe li are substantially the saine as that of secondary tubing string lin operating the apparatus just described for the purpose oi injecting gas or other fluid into a stratum oi" oil producing sand, and assuming that the parts are in the positions indicated in l'lig. l.

with upper control or release valve closed, inlet valve and lower control valve open, and taire-ofi valve lit closed, the repressuring iluid iiows iroin the compressor or reservoir at a relatively high pressure through inlet line into control pipe lli, and thence downwardly lll until it ,llt this point the resistance to iiow through oriiice lli oi htting iii offered by the restricted bore ii oi the oriiice plug reduces the pressure oi? the iluid as it passes into main tubing string il. to the proper amount desired ior the repressuring operation, the iluid leaving the htting iii continuing to liow downwardly through the main tubing string until it reaches the level where it passes into the sand. Due to the greater pressure exerted upon the euposeol area oi' the upper end of the orifice plug, a tight seal is maintained between the ground tapered surfaces oi the lower end it ol the plug and seat it which prevents leakage through oriiice lli around the outside of the plug, without the necessity for using latching or other mechanical means for positively holding the plug in position.

lWhen it is desired to vary the pressure of the iiuid issuing :trom ritting lll into the main tubing string, the oriiice plug il is@ raised to the surface and replaced by one having a bore of different diameter. To effect this replacement in accordance with the present invention, it is only necessary to close inlet valve ill and then open upper control or release valve lil, whereupon the pressure of the back flow oi gas from the well is exerted against the bottom end of orifice plug il and, in conjunction with the resistance to upward flow offered by the restricted bore ill, unseats the plug and forces it to the surface where it is caught in cushioning cage it. Release valve it is then closed so as to permit the removal oi cushioning cage lil and the trapped orihce plug. A plug having a, bore of proper diameter to eiect the desired change in pressure may be substituted for the one removed by first closing lower control valve 33, then opening release valve lill, and dropping the replacing plug into the upper end of the control pipe Where it comes to rest on the gate of lower control valve 33. Release possibility of injury to its tapered lower end it or the seat lli, this velocity may be reduced by manipulating release valve lll so as to produce a 'counterfiow upwardly through the secondary tubing string which will check the fall oi the oriiice plug and permit it to be seated as lightly as desired. When the plug reaches its seat, release valve lil is tightly closed and the repressurlng operation continued by opening inlet valve In Figs. 2 and 5 there is disclosed another ernbodirnent oi the method and apparatus oi" the present invention which is particularly adapted ior use in controlling the iiow oi gas or oil from a producing well, but which embodies the same fundamental structure and mode oi operation as the embodiment oi l'ligs. l and Il. For simplicity, the following description will be limited to the use of the invention in connection with a gas a producing well, although it will be obvious that the same method and apparatus is equally well adapted to oil well operation.

In the form illustrated, the main and secondary tubing strings lli and it and a control pipe ill are Fill connected together by a coupling in substan tially the saine manner as that heretofore described in connection with the nrst embodiment, and control pipe il is similarly provided with control valves and lili, inlet line iii and valve iii, and cushioning cage The upper end ot main tubing-string iii is also provided with a taire-oii line lill and valve this line in the present embodiment constituting the field line into which is delivered the gas recovered from the well.

is shown, both strings of tubing preferably er:- tend downwardly' in the well lll all the way into the shot hole in the producing stratum of the sand, the main tubing string il being provided with a suitable packer it sealing oil the upper portion oi the well from the space into which flows the gas which it is desired to remove from the well. The lower end of main tubing string il is closed oii :troni direct communication with the shot hole il by a cap llt, preferably detachably secured to the tubing as by a threaded connection. The lower end oi secondary tubing string it is similarly connected to a fitting iii having an orifice lli and tapered seat it of substantially the san/reconstruction as the iitting ill sho-wn in Figs. l and li, but differing from the latter in that it is also provided with an opening all in the side wall thereof located above the position occupied by the upper end of theoriiice plug il whenthe latter is in engagement with its seat it. The interior oi fitting lll is in direct communication with the shot hole iii through a nipple lli which passes through an opening lit in cap it and is threaded int-o the opening 1li' of fitting lll. The inside diameter of nipple lli is at least as great as that of orifice it.

Inl normal operation of this second embodiment of the invention for the recovery of gas from the well, all of control valves il, it and 3i are closed, while take-off valve til and any other valves located in the line it are open, the ground pressure forcing the gas from the shot hole 33 through the nipple t3, downwardly through the restricted bore l@ of oriiice plug ll and into ill iti

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be utilized for this purpose ln emergencies.

the cap 40 and the lower end of main tubing string I2, whence it flows upwardly through the latter into take-off line 29 which delivers it to storage or any other desired destination. In passing through the bore of the orifice plug, the flow of the gas is restricted to an extent depending upon the size of said bore, the latter being so selected as to result in the desired rate of production by the well. As in the case of the embodiment of Figs. 1 and 4, orifice I5 of fitting 4| is of such size as, in the absence of an orifice plug, will enable operation of the well at its maximum capacity.

When it is desired to change the size of orifice plug being used, it is normally necessary only to open

control valves

33 and 34, whereupon the pressure of the back flow of gas from main tubing string I2 is exerted against the bottom of the orifice plug and, because of the resistance to upward flow into the inner string of tubing offered by the restricted bore of the plug, unseats the latter and forces it to the surface where it is trapped in cushioning cage 35 in the manner previously described.

In view of the fact that, under certain conditions of well operation, the pressure of the back flow from the main tubing string is ineffective t0 unseat the orifice plug and raise it tothe surface, additional means have been provided which may As shown, a suitable reservoir 45 is provided at the Well head connected by piping 46 and valve 41 to a cross connection 48 between take-ofi' or field line 29 and line 3| which connects to control pipe 2| at a point

intermediate valves

33 and 34. Lines 29 and 3| are also provided with

valves

49 and 50, respectively, on the field side ofcross connection 48. With this arrangement, the reservoir 45 may be filled with gas at substantially the same pressure as that existing at the bottom of the Well 31 either by opening

valves

41 and 30 with all other valves closed, in which event the gas from the shot hole 38 will follow the same path of flow as during normal production except that it will be diverted into the reservoir 45 instead of continuing past valve 49 in the field line 29, or by opening lower control valve 33 and

valves

32 and 41 with all other valves closed, whereupon the gas will flow directly from the shot hole through nipple 43 and upwardly through secondary tubing string I3 into the reservoir 45 via line 3|, cross connection 48 and piping 46. Reservoir 45 may also be supplied with gas under pressure from any other suitable source, as by a pipe 5| and valve 52.

I'he reservoir 45 being charged in any of the ways just described, if' the normal back flow from the main tubing string fails to unseat the orifice plug, the alternative or emergency procedure is to first blow down the well pressure until the latter is below that of the gas in the reservoir, and then release the reservoir pressure into the main tubing string by opening

valves

41 and 30, valve 49 being closed, permitting this pressure to blow into the atmosphere through tubing string I3 and control pipe 2| in the same way as when the unseating operation is performed in normal manner by the back fiow from the field line. In blowing the well down preparatory to the use of reservoir pressure for unseating the orifice plug and bringing it to the surface,l wastage of gas can be prevented by blowing either into the field line 29 through line 3| and cross connection 48,

or into the continuation of line `3| beyond the cross connection.

After the orifice plug has been unseated and raised to the surface by either the normal or emergency operation described, ,the replacing plugmay be dropped down onto its seat I6 in fitting 4| by gravity by the same manipulation of valves as that described in connection with the embodiment of Figs. l and 4, taking care.

only that field line valve 30 is closed.

When conditions are such that it is not practical to run the secondary tubing string I3 inside of main string I2 in a producing well, the arrangement illustrated in Figs. 2 and 5 may be modified in the manner indicated in Figs. 3 and 6, but without any change in the fundamental principles involved. As shown in the latter two figures, the arrangement of the elements is substantially the same as that of Figs. 2 and 5 except for the specific construction at the bottom of the well and the fact that the secondary tubing string I3 is located outside of main tubing string I2, a change Whichalso involves the replacement of the special coupling 22 by a blank sealing disk 53 closing the upper end of the main tubing string. In this connection, it should be noted that it is intended that the connections at the Well head to the emergency reservoir 45, shown to the right of the line A-A in Fig. 2, should be duplicated in Fig. 3, if desired.

As is best illustrated in Fig. 6, the lower ends of both tubing strings I2 and I3 are preferably threaded into a combined cap and orifice plug seat fitting 54, the portion of said fitting beneath the end of secondary tubing string- I3 being provided wth an orifice I5 and tapered seat I6 adapted to support an orifice plug I1, all as previously described, and the orifice I5 communicating with the interior of tubing string I2 through a suitable passageway 55. Just above its point of connection to the fitting 54, and at a position terior of tubing string I3 and shot hole 38.

Aside from these differences in structural detail, including the modification of packer 39 to adapt it for use with two strings of tubing instead of one, the embodiment of Figs. 3 and 6 is of substantially the same construction, and operates in accordance With the same method, as the form of the invention shown in Figs. 2 and 5, previously described in detail.

It will be apparent from the foregoing description that the present invention provides both a novel method and novel means for controlling the fiow of fiuids in gas and oil wells which greatly facilitate well operation and overcome the defects of the prior procedures and mechanisms heretofore used for varying the pressure or rate of flow of gas, oil and other iiuids in pressure and producing wells. By the present invention it has been made possible'to quickly and easily change the size of a flow restricting fitting normally positioned a substantial distance below the surface of the ground, merely by the manipulation of certain valves at the well head and Without the necessity for using fishing tools or like instrumentalities, or for withdrawing the tubing from the well in order to obtain access to the fitting. Not only do the new method and apparatus effect substantial savings in time and labor, but there is also very little wastage of fluid in lill fill

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the operations involved. The importance of such savings will be readily appreciated when it is considered that in repressuring operations, in particular, it is necessary to vary the pressure of the iiuid which is injected into the oil producing sand at relatively frequent intervals in order to maintain the desired rate of recovery of the producing wells. rllhese and other features, all of which will be apparent from the disclosure herein, endow the present invention with substantial advantages over the methods and apparatus of the same generic character hitherto known to the art.

dlthoughl three specific forms of apparatus embodying the invention have been described and illustrated in the accompanying drawings, it will be obvious that the invention is not limited to the particular structures shown, but is capable of a variety of mechanical embodiments. For example, the fittings which are connected to the lower ends of the tubing strings may vary in their details of construction from those specifically illustrated in the drawings, and may be detachably connected to the tubing in other ways than by the threaded connections shown. It is also within the contemplation of the present invention that a plurality ofdiow restricting orifices may be employed at diderent levels in the same well, and that the orifice plugs may be made solid instead of with restricted bores, in which latter case the variation in control might be effected by varying the length ci the tapered lower ends of the plugs so as to expose more or less of the areas of orices formed in the sides of the fittings in which the plugs are seated. It should also be understood that the particular arrangement of valves and connections at the well head which` enable the orifice plug to be raised by fluid pressure alone may be varied somewhat fromthe embodiments illustrated. Various other changes, which will now suggest themselves to those skilled in the art, may be made in the procedural steps of the method, and in the form, details of construction and arrangements of the parts of the apparatus, without departing from the spirit of the invention. Reference is therefore to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

l. in gas or oil well apparatus of the character described, the combination of a string of tubing through which fluid may be injected into or removed from the well, means connected to said tubing at a point a substantial distance below the surface of the ground providing an oriflce through which fluid may pass from or to the interior of said tubing, means including an orifice plug associated with said orifice for restricting the flow of fluid through said orifice, said plug being maintained in flow restricting position solely by the force of gravity and the pressure of the fluid in said tubing thereabove, and means for producing a flow of fluid into and upwardly through said tubing of sufficient force to raise said plug 'from its flow restricting position to the upper end of said tubing by fluid pressure alone.

2. in gas or oil well apparatus of the character described, the combination of a string of tubing through which fluid may be injected into or. re-

moved from the well, means connected to said tubing at a point a substantial distance below the surface of the ground providing an orifice through which iiuid may pass from or tothe interior of said tubing. a tapered seat associated with said orifice, an oriflce plug having a tapered lower end adapted to engage said seat and a restricted bore therethrough of smaller diameter than said orice for controlling the flow 0f fluid through said orifice, said plug being malntained in ow restricting position on said seat solely by the force of gravity and the pressin'e of the fluid in said tubing thereabove, and means for producing a now of fluid into and upwardly through said tubing of sufficient force to unseat said plug and raise it to the upper end of said tubing by fluid pressure alone.

3. In gas or oil well apparatus of the character described, the combination of a string of tubing through which iiuid may be injected into or removed from the well, means connected to said tubing at a point a substantial distance below the surface of the ground providing an orifice through which iiuid may pass from or to the interior of said tubing, means including an orifice plug associated with said orifice for restricting the flow of huid through said orifice, said plug being maintained in iiow restricting position solely by the force of gravity and the pressure of the Huid in said tubing thereabove, means for producing a flow of fluid into and upwardly through said tubing of sumcient force to raise said plug from its flow restricting position to the upper end of said tubing by fluid pressure alone, and means for trapping said plug at the upper end of said tubing while permitting the escape of said fluid therefrom.

i. In gas or oil well apparatus of the character described, the combination of a string of tubing through which fluid may be injected into or removed from the well, means connected to said tubing at a point a substantial distance below the surface of the ground providing an oridce through which fluid may pass from or to the interior of said tubing, means including an orifice plug associated with said orifice for restricting the How of huid through said orifice, said plug being maintained in flow restricting position solely by the force of gravity and the pressure of the fluid 'in said tubing thereabove, means for producing a now of duid into and upwardly through said tubing of sumcient force to raise said plug from its how restricting position to the upper end of said tubing by huid pressure alone, and a perforated cage member detachably connected to the upper end of said tubing for trapping said plug while permitting the escape of said fluid therefrom.

5. ln gas or oil well apparatus of the character described, the combination of a string of tubing through which fluid may be injected into or removed from the well, means connected to said tubing at a point a substantial distance below the surface of the ground providing an orifice through which fluid may pass from or to the interior of said tubing, means including an orifice plug associated with said orifice for restricting the iiow of fluid through said orifice, said plug being maintained in flow restricting position solely by the force of gravity and the pressure of the fluid in said tubing thereabove, means for producing a flow of iiuid into and upwardly through said tubing of sulicient force to raise said plug from its flow restricting position to the upper end of said tubing by uid pressure alone, including a release valve at the upper end of said tubing for opening the latter to the atmosphere, and means detachably connected to the discharge side of said valve for trapping said plug while permitting the escape of saidiiuid from said tubing.

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6. In gas or oil well apparatus` of the character described, the combination of a string of tubing through which fluid may be injected into or removed from the well, means connected to said tubing at a point a substantial distance below the surface of the ground providing an orifice through which fluid may pass from or to the interior of said tubing, means including an orifice plug associated with said orifice for restricting the flow of fluid through said orifice, said plug being maintained in flow restricting position solely by .the force of gravity and the pressure of the fluid in said tubing thereabove, and means for producing a flow of fluid into and upwardly through said tubing of sufficient force to raise said plug from its flow vrestricting position to the upper end of said tubing by fluid pressure alone, including a pair of valves in said tubing at the upper end thereof for opening the latter to the atmosphere, the section of .tubing intermediate said valves comprising a pressure equalizing chamber for reception of said plug preparatory to dropping the same through said tubing by gravity to flow restricting position.

7, In gas or oil well apparatus of the character described, the combination of-a string of tubing through which'fiuid may be injected into or removed from the well, a fitting connected to said tubing having an orifice through which fluid may pass from or to the 'interior of said tubing and a tapered seat leading toward said orifice, and a substantially cylindrical orifice plug having a tapered lower end adapted to engage said seat and a vertical axial bore therethrough of smaller diameter than said orifice for vrestrictively controlling the flow of fluid through the latter, said plug being maintained in flow restricting position on said seat solely by the force of gravity and the pressure of the fluid in said tubing thereabove.

8. In gas or oil well apparatus of the character described, the combination of a main string of tubing through which fluid may be injected into or removed from the well, a secondary tubing string associated with said main string, means connected to said secondary string at a point a substantial distance below the well head providing an orifice through which fluid may pass between the interiors of said main and secondary strings, means for restricting the flow of fluid through said orifice including an oriflce plug maintained in flow restricting position solely by the force of gravity and the pressure of the fluid in said secondary string, and means for producing a flow of fluid into and upwardly through said secondary string of sufficient force to raise said plug from its flow restricting position to the well head by fluid pressure alone.

9. In gas or oil well apparatus of the character described, the combination of a main string of string associated with said main string, means connected to said secondary string at a point a substantial distance below the well head providing an orifice through which fluid may pass between the interiors of said main and secondary strings, means for restricting the flow of fluid through said orifice including an orifice plug maintained in flow restricting position-so1ely by the force of gravity and the pressure of the fluid in said secondary string, means for producing a flow of fluid into and upwardly through said secondary string of suicient force to raise said plug from its flow restricting position to the well head by uid pressure alone, including valve means for opening said secondary string to the atmosphere, and means for trapping said plug at the upper end of said secondary string while permitting the escape therefrom of said fluid.

10. In a pressure well, the combination of a main string of tubing through which a repressuring fluid'may be injected into the well. a secondary tubing string associated with said main string, a connection to the upper end of said secondary string for supplying repressuring fluid thereto, a fitting connected to said secondary string at a point a substantial distance below the well head having an orifice through which the repressuring fluid may flow from said secondary string into said main string, means for restricting the flow of fluid through said orifice including a removable plug maintained in flow restricting position solely by the force of gravity and the pressure of the fluid in said secondary string, and means for producing a back flow of fluid from said main string into and upwardly through said secondary string of suiiicient force to raise said plug from its flow restricting position to the well head by fluid pressure alone, including 'valve means for disconnecting said secondary string from the source of repressuring fluid and for opening said string to the atmosphere.

11. In a pressure well, the combination of a main string of tubing through which a repressuring fluid may be injected into the well, a secondary tubing string asssociated with said main string, a connection to the upper end of said secondary string for supplying repressuring fluid thereto, a fitting connected to said secondary string at a point a substantial distance below the well head having an orifice through which `the repressuring fluid may flow from said secincluding a removable plug maintained in flow restricting position solely by the force of gravity and the pressure of the fluid in said secondary string, and means for producing a back flow of fluid from said main string into and upwardly through said secondary string of sufficient force to raise said plug from 'its flow restricting position to the well head by fluid pressure alone, including a valve for disconnecting said secondary string from the source of repressuring fluid, a second valve in said secondary string above said connection for opening said string to the atmosphere, and a third valve in said secondary string below said connection, the section of said secondary string intermediate said second and third valves comprising a pressure equalizing chamber for reception of said plug preparatory to dropping the same through said secondary string by gravity to flow restricting position.

12. In a pressure well, the combination of a main string of tubing through which a repressuring fluid may be injected into the well, a secondary tubing string associated with said main string, a connection to the upper end of said secondary string for supplying repressuring fluid thereto, a fitting connected to said secondary string at a point a substantial distance below the well head having an orifice through which the repressuring fluid may flow from said secondary string into said main string, a tapered seat leading toward said orifice, an orifice plug having a tapered lower end adapted to engage said seat and a restricted bore therethrough of a diameter less than that of said orifice for controlling the flow of fluid through the latter, said plug being assauts 7 maintained in flow restricting position on said seat solely by the force o! gravity and the pressure or the fluid in said secondary string, and ineens tor producing a back iiow oi.' iiuid from the main string into and upwardly through said seeondary string of sumcient force to unseat said plug and raise it to the well head by iluid pressure alone. v 13. In a. producing well, the combination oi a id main string of tubing through which the iluid to he recovered from the well may be raised to the welt head, said string being sealed against direct communication with the well, a secondary tubing string associated with said main string and havw ing an opening in the wali thereof through which nuid may ilow from the weli, means providing communication between the interiors oi said main and secondary strings, including an orifice located below the level of said opening 2d in the secondary string. means including a removable orifice plug associated with said oriiice for restricting the flow of huid through the lat ter. and means for producing a back ilow of fluid downwardly through said main string, through 25 said oriiice and upwardly into and through said secondary string of sufdcient torce to raise said plug irom'its flow restricting position to the top oi said secondary string by fluid pressure alone. 14. In a producing well. the combination of a 3d main string of tubing through which the tiuid to be recovered from the well may be raised to the well head, said string being sealed against direct communication with the well. a secondary tubing string associated with said main string and 35 having an opening in the wall thereof through which fluid may tlow from the well, means providing communication between the inferiores! said main and secondary strings, includingan oriiice located below the level oi said opening in' M the secondary string, means including'a remov able` oridce plug' associated with said orice for restricting the i'low of iluid through the latter. and means for producing a back flow of iluld downwardly through said main string, through said oriiice and upwardly into and through said u secondary string of sufilcient force t raise said plug from its now restricting position to the top oi said secondary string by iluid pressure alone. said last named means including a reservoir, means for charging said reservoir with uid from l0 said well. means for connecting said reservoir to said main string, and valve means for opening said secondary string to the atmosphere.,

15. In a producing well, the combination oi a main string of tubing through which the iiuid to 18 be recovered from the well may be raised to the well head. said string being sealed against direct communication with the well. a secondary tubing string associated with said main string and hav- 4 ing an opening in the wall thereof through which 20 fluid may iiow from the well, means providing communication between the interiors oi.' said main and secondary strings. including an oriiice located below the level o! said opening in the secondary string and a tapered seat leading toward said orifice, a removable orifice plug having a tapered lower end adapted to engage said seat and a restricted bore therethrough of a diameter less than that or said orifice for controlling the now of iiuid through the latter. said plug being maintained in iiow restricting position on said seat solely by the force o! gravity and the pressure of the iiuid in said secondary string, and' means for producing a back iiow of iiuid downwardly through said main string, through said oriilce and upwardly into and through said secondary string of suicient force to unseat said plug and raise it to the top of said secondary string by huid pressure alone..

HARVEY T. DORTON. 40