US2781774A

US2781774A - Valve apparatus for automatically filling well conduits

Info

Publication number: US2781774A
Application number: US235072A
Authority: US
Inventors: Reuben C Baker; Martin B Conrad
Original assignee: Baker Oil Tools Inc
Current assignee: Baker Hughes Oilfield Operations LLC
Priority date: 1951-07-03
Filing date: 1951-07-03
Publication date: 1957-02-19
Anticipated expiration: 1974-02-19

Description

Feb. 19, 1957 R. c. BAKER ETAL 2,781,774

VALVE APPARATUS FOR AUTOMATICALLY FILLNG WELL CONDUITS IN VEN TORS.

REUBE'N C. BAKE/P8 MART/N 'B CONRA,

Mii Il A TTOR/VEKS Feb. 19, 1957 R. c. BAKER ETAL 2,781,774

VALVE vAPPARATUS FOR AUTOMATICALLY FILLING WELL coNnurTs `Fi1ed July 3, 1951 3 Sheets-Shea?l 2 'T9 7./ 29 af REI/BEN C. BAKER 8 MARTIN B. CONRAD' IN V EN TORJ.

i? 454545 f5 if MM'/uww Feb. 19, 1957 R. c. BAKER ETAL.

VALVE APPARATUS FOR AUTOMATICALLY FILLING WELL CONDUITS Filed July s, 1951 3 Sheets-Sheet 5 RE'UBEN C. BAKER 8 MART/N B. CONRAD. INVENTORS BY Y A TTORNEVS` United States Patenti` VALVE APPARATUS FOR AUTOMATICALLY FILLING WELL CONDUITS Reuben C. Baker, Coalinga, and Martin B. Conrad, Downey, Calif., assgnors to Baker Oil Tools, Inc., Vernon, Calif., a corporation of California Application July 3, 1951, Serial No. 235,072

12 Claims. (Cl. 137--493.2)

The present invention relates to subsurface well apparatus, and more particularly to apparatus for automatically filling a string of well casing, drill pipe, or a similar well conduit, as it is lowered through the liquid in a well bore.

Ordinarily, a string of well casing will have an upwardly seating check valve at its lower portion for preventing uid from entering the well casing, thereby causing the casing to float, to some extent, in the fluid, relieving the derrick and draw works of a large portion of the weight of the casing string. However, in running casing strings and similiar well conduits in deep wells, the hydrostatic head of fluid surrounding the casing may be so great as to tend to collapse the lower portion of the casing string. To prevent such undesirable occurrence, it has been proposed to allow some fluid to enter the casing string; so as to decrease the differential hydrostatic head of fluid between the exterior and interior of the conduit string. That is, thev conduit string is allowed to lill partially while being lowered through the liquid in the well bore, lessening the tendency of the hydrostatic head to collapse the lower portion of the casing string, while still maintaining the latter partially empty, to retain a large yextent of buoyancy in the casing string.

Devices heretofore used for automatically lilling the casing string, by allowing the well fluid to flow thereinto to a certain level, have not allowed fluid to be pumped down through the casing string, without removing the automatic lilling device from the casing string. At times, .sudden stopping and starting of the conduit string while it is being run in the well bore cause the liuid within the conduit string to release and eject the automatic lling device. Accordingly, it is no longer available for performing its function of allowing the casing to lill to a partial extent. Again, the prior devices did not allow liuids to be pumped in a downward direction through them, such as might be desirable in connection with Washing out bridges that might be encountered in the well bore.

Accordingly, an object of the present invention is to provide improved devices for automatically lling a well conduit string to a predetermined level that is substantially less than the fluid level externally of the conduit string.

Another object of the invention is to provide a device that automatically :allows the well lluid to llow into a conduit string, and which will also allow the uid in the conduit string to be pumped or to flow down through the device.

A further object of the invention is to provide a device for automatically allowing Huid to ow into a casing string, and which is also capable of functioning Ias a back pressure valve to prevent fluid from ilowing into the casing string when the latter is lilled substantially with uid.

Another object of the invention is to provide a device for automatically allowing the well iluid to llow into a casing string embodying an upwardly seating back pressure valve, in which sudden starts or stops incident to running the casing string in the well bore are incapable of ejecting the filling device from the casing string, or otherwise rendering it inoperative.

Yet a further object of the invention is to prevent the plugging or fouling of an automatic conduit lill-up device, as by providing a screen through which the lluid must flow, and to automatically clean the screen, or its equivalent, during lowering of the conduit in the well bore.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of several forms in which it may be embodied. Such forms are shown in the drawings accompanying and forming part of the present specification. These forms will now be described in detail, illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in alimiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure l is a longitudinal section, with parts disclosed in side elevation, through an apparatus embodying the invention, with the valve mechanism in closed position;

Fig. 2 is an enlarged longitudinal section through the lower. portion of the mechanism illustrated in Fig. l, with the valve parts in closed position;

Fig. 3 is a cross-section taken along the line 3-3 on Fig. 2;

Fig. 4 is `a cross-section taken generally along the line 4-4 on Fig. 2;

Fig. 5 is a View similar to Fig. 2, illustrating the difierential valve portion of the device in open position, allowing fluid to iiow up into the well conduit;

Fig. 6 is a view similar to Fig. 2, illustrating the back pressure valve portion of the device in open position, to allow downward passage of lluid through the device;

Fig. 7 is a longitudinal section through yet another embodiment of' theinvention, with the valve parts disclosed in closed position;

Fig. 8 is a view similar to Fig. 7, disclosing the back pressure valve portion of the device shifted downwardly to open position;

Fig. 9 is a cross-section taken along the line 9-9 on Fig. 8.

ln the form of invention illustrated in Figs. l to 6, inelusive, a casing shoe A forms the lower end of a string of well casing B being lowered through the uid in a well bore C to the desired location. Such casing shoes may embody a back pressure valve for preventing return flow of tluids through the well casing while permitting downward passage of fluid through the well casing. In the present case, the back pressure valve is prevented from moving upwardly to closed position; so as to allow the well uid to enter the casing string to a predetermined height, which is substantially lower than the uid level externally of the casing string.

As specioally disclosed in the drawings, the casing shoe A includes an outer tubular member lil having an upper threaded box 11 screwed onto the lower end of a casing section B. An elongate cementitious plug 12 of generally tubular form is cast in the tubular member itl, being inseparably united therewith by means of spaced annular ribs 13 on the cementitious plug received within companion internal grooves 14 in the tubular member. The lower end of the plug may have a curved or rounded nose 15 for guiding the casing shoe past obstructions that might be present in the wel] bore.

An upper sleeve 16 is disposed centrally in the cementitious plug 12, providing a central passage 17 through which fluids may pass. The lower end of this sleeve is piloted into a valve seat 18 cast in the plug, having a rubber, or rubber-like seal ring 19 therein which is attached to the seat by a clamp ring 2@ that bears 'upon a valve housing or spacer sleeve 21 depending from the seat 18.

A back pressure valve element 22, in the form of a ball, which is preferably buoyant in cement slurry, is movable upwardly into engagement with the seal ring 19 to prevent upward passage of lluid into the casing string. However, as described below, this valve element 22 is pre vented from engaging its seat by a retainer arm 23 extending into the seat 18 and holding the valve element 22 in an eccentric position relative to the axis of the apparatus.

The lower end of the housing or spacer sleeve 21 rests upon a valve housing 24 which is inseparably united to the cementitious plug 12 by the ribs 25 on the latter being received within companion grooves 26 in the housing. It is to be noted that the upper sleeve 16, seat 13, seal ring 19, clamp ring 20, spacer sleeve 21 and valve housing 24 are all disposed centrally of the apparatus, providing a straight-through passage for the ow of fluid, except for the presence of an automatic casing ll-up device 27 now to be described.

As described above, the retainer arm 23 initially prevents engagement of the back pressure ball valve element 22 with its seat 19; so as to allow upward passage of well fluid into the well casing B. However, it is desired to allow the fluid in the well casing to rise to only a predetermined level, which bears a definite relationship to the level of the well lluid surrounding the casing, the fluid level internally of the casing being substantially less than that externally thereof. Accordingly, the diterential valve device 27 is provided in the valve housing 24 to accomplish this objective. This device includes an elongate valve body 28 disposed within the valve housing 24 and having an upper portion 29 which is spaced from the inner wall of the valve housing 24 by a plurality of centering pins 30, to provide an annular passage 31 for the flow of uid in both directions around the upper portion 29 of the body. Such upper portion of the body is integral with an intermediate portion 32 having an outwardly extending flange or head 33 adapted to be disposed within a cylindrical valve seat 34 in the housing. When so disposed, the valve head 33 is in closed position, fluids being prevented from passing between the annular passage 31 and around the valve head. To prevent leakage of such lluids in both directions around the periphery of the cylindrical valve head 33, a suitable seal, such as a round rubber ring 35, is disposed in a ring groove 36 in the housing, for slidable sealing engagement with the valve head 33.

Assuming that the valve head 33 has been shifted downwardly out of its companion cylindrical seat 34, lluids flowing down through the annular passage 31 can then pass through the seat 34 and around the valve head 33 and into a lower annular passage 37 formed between the enlarged lower portion 38 of the valve housing 24 and a lower valve body portion 39. The fluids can llow through this lower passage 37 and inwardly through a plurality of lateral circulation ports 40 into the interior or lower central passage 41 of the body 28, from where the fluids can flow down through a perforated screen 42 and out through the lower end of the shoe. This screen 42 may be of generally conical shape, its side portion 43 being disposed in a recess 44 in the lower body portion 39, being held therein by a split snap ring 45 fitting within a body groove 46 immediately below the screen, securing the latter between the snap ring and a body shoulder 47.

The valve body 28 is normally urged in an upward direction, to dispose its head 33 within the cylindrical seat 34 and in engagement with a stop shoulder 48 by a spring device. As illustrated, `such spring device includes an upper annular spring seat and guide 49 slidable along the lower inner wall of the housing portion 38 and bearing upon a shoulder 50 provided on the lower body portion 39 below the circulation ports 40. This spring seat 49 engages a rubber sleeve 51 whose lower end bears upon a lower spring seat and guide 52 that is initially carried by the lower housing member 38 by one or more shear screws 53 threaded into the lower seat 52 and received within an internal groove 54 in the housing 38. The lower end of the rubber spring element 51 surrounds an upwardly directed boss 55 of the lower spring seat 52 to maintain the rubber sleeve 51 adjacent the housing 3S. Such boss 55 also provides a longer guiding surface in the lower seat for the lower body portion 39 during its longitudinal movement with respect to the housing 24.

It is evident that the rubber spring 51, acting through the upper seat 49 and body 28, tends to maintain the valve head 33 against the stop shoulder 48. Fluid pressure from above the device of sucient extent can shift the valve body 28 downwardly against the action of the rubber sleeve 51, foreshorten'ing the latter and shifting the valve head 33 out of its seat 34, or to open position.

It is desired to allow fluids to llow upwardly through the valve body 28 to lill the casing B to a predetermined level, which is lower than the level of the fluid surrounding the well casing. To accomplish this purpose, a differential valve member 56 is slidably mounted in, and centrally of, the valve body 28. This valve member 56 includes a lower relatively small piston or head 57 slidable into a small cylindrical seat 58 in the body 28, leakage between the lower head 57 and body being prevented by a side seal 59, such as a rubber 0 ring, disposed in a body groove `60 and engaging the periphery of the Asmall diameter head 57. When the head 57 is elevated out of its spring seat 58, fluid can flow through the lower seat 58 and laterally out wardly through the body ports 61 and into the annular passage 31 surrounding the body 28, continuing in an upward direction into the casing string B. Such fluid is precluded from passing upwardly around the smaller diarneter head 57 above the body ports 61 by a suitable side seal 62, such as a rubber O ring, disposed in a ring groove 63 above the ports 61 and engaging the periphery of the small diameter head.

The small diameter valve head 57 is secured to, or is integral with, a large diameter upper head or piston 64 disposed within a large cylinder bore 65 having a substantially greater diameter than the lower cylinder bore 58. This head 64 is provided with a peripheral ring groove 66 containing a seal ring 67, such as a rubber O ring, slidably engaging the wall of the large cylinder bore 65. The valve member 56 itself is imperforate; so that fluids cannot pass therethrough, in view of the fact that its lower end 68 is solid.

The dilerential valve member 56 is movable downwardly to closed position over the ports 61 when the smaller head 57 is disposed in sealing engagement with the lower seal 59, as illustrated in Fig. 2. This position is determined by engagement of the upper head 64 with the lower end or shoulder 68a of the large cylinder 65. Fluids cannot pass in a downward direction around the upper head seal 67, or in an upward direction between the small diameter head 57 and the intermediate seal ring 62; so that the only fluid around the heads and between these seals Iis air at substantially atmospheric pressure.

When the valve member 56 is moved upwardly to open the body ports 61, such upward movement is limited by engagement of the upper head 64 with a stop ring 69, that may be in the form of a split snap ring disposed within a ring groove 70 in the body 28. A screw 71 may secure the ball retainer arm 23 to the valve body 2S in the region of this snap ring 69.

Parts of the valve device initially occupy the position illustrated in Figs. l and 2, in which the differential valve member 56 closes the body ports 61, the body valve head member 33 engaging the stop shoulder 48 under the influence of the rubber spring 51, and with the retainer arm 23 holding the back pressure ball valve element 22 off its seat 19. The shoe A is secured to the lower end of the casing string B, and this combination is lowered through the lluid in the well bore C. During such lowering action, the hydrostatic head of fluid surrounding the casing string can act upwardly over the body head 33 to hold it in closed position against the stop shoulder 48. However, such fluid is also acting against the vunderside 68 of the lower diierential valve head 57, urging it in an upward direction and to a position in which the upper end of the valve member 56 engages the stop ring 69, such as illustrated in Fig. 5, in which position the body ports 61 are open, fluid flowing through these ports and through the annular passage 31 around the body 28, continuing upwardly around the ball valve member 22, which is prevented from engaging its seat 19 by the arm 23, and on upwardly into the casing string B.

The fluid that has thus partially filled the casing string is acting downwardly on the enlarged head portion 64 of the valve member', tending to shift the latter in a downward direction and back to the position illustrated in Fig. 2, in which the body ports 61 are closed. The ability of the iluid in the casing string to so shift the valve member 56 in a downward direction depends upon the relationship between the hydrostatic head of fluid in the well casing string B acting downwardly upon the valve member 56 and the hydrostatic head of fluid around the well casing acting upwardly on the valve member 56.

The pressure actuatable area S across the large piston or valve head member 64 is substantially greater than the pressure actuatable area R across the smal-l piston or valve head member 57. The hydrostatic head of fluid in the well casing is acting in a downward direction over this larger area S, whereas the hydrostatic head of iiuid externally of the well casing is acting upwardly over the smaller area R. Accordingly, it will take a substantially lesser proportionate hydrostatic head of fluid inside of the well casing to shift the valve member 56 downwardly to body port closing position, than the hydrostatic head of fluid around lthe well casing tending to shift the valve member S6 upwardly to body port opening position. A balanced valve condition will exist when the following equation is satisiied, neglecting friction:

in which P1 is the hydrostatic head externally of the casing string, and P2 is the hydrostatic head internally of the casing string.

The above equation readily demonstrates that, since the area S is substantially greater than the area R, the hydrostatic head Pz internally of the casing `str-ing can be much smaller than the hydrostatic head P1 externally of the casing string, to shift the valve member 56 downwardly to body port closing position. Thus, as the casing string B is lowered through the fluid in the well bore, the valve member 56 will shift upwardly to open position, to allow uid to enter the casing string t only a predetermined level. When such level is reached, the valve 56 is automatically shifted downwardly to closed position. Thus. the ratio between the hydrostatic head internally of the casing string and that externally of the casing string is equal to the ratio of the smaller area R with respect to the larger area S. v

The well casing E is, accordingly, automatically filled with fluid to a partial extent, to hold the pressure differential acting on the exterior of the lower portion of the casing to a `safe value, and to thereby prevent inward collapsing of the casing string. At the same time, the casing string is maintained in a partially empty state; so as to enable the well fluid to buoy or float the casing in the well bore, relieving the derrick and draw works of a large portion of the casing load.

ln running the casing string B in the well bore C, only relatively clean fluid is allowed to pass upwardly through the differential valve 56, 28, inasmuch as the fluid must pass through the relatively small perforations in the screen 42 at the lower end of the valve body 28. In the event that this screen tends to become plugged, it is automatically cleaned by the act of starting and stopping the casing string B during its descent in the well bore. The casing string is lowered through'the well bore as a result of connecting casing sections to one another at the top of the hole. A casing sectionv is connected to an uppermost casing section and the casing is then lowered through the well bore substantially the length of a casing section, whereupon the descent is arrested. However, despite the stopping of the descent of the casing string, the liquid therewithin tends to continue to move in a downward direction. Suc-h action is sufficient to shift the valve body 28 downwardly against the force exerted by therubber spring 51, to move its valve head 33 out of its cylindrical seat 34, allowing the liuid to pass down through the annular passage 31, around the valve head 33, and in through Ithe circulation ports 40 in the body, the uid then flowing downwardly through the conical screen 42. During such downward flowing, the fluid tends to clear the screen of any substances that might be adhering to its lower side. Similarly, when the casing string is picked up slightly, as usually occurs in lifting it out of the slips in the rotary table, there is a downward surge of the liquid in the well casing, .which will also open the valve 33, 34 and clean the screen 42.

The ability of the valve body member 28 to move downwardly to open position also allows the entire well casing to be filled with Huid, in the event it is necessary to circulate down through the casing string. The fluid pressure from above will insure the downward position of the valve member 56 across the body ports 61 and will also shift the valve body 28 downwardly until the head 33 is disposed below the cylindrical seat 34, whereupon iluid can be pumped around this head 33, through the circulation 'ports 40, and down through the screen 42, for the purpose of washing out any obstructions that might be disposed immediately below the casing shoe A, or to otherwise condition the well bore. For that matter, if desired, cement slurry, or other cementitious material, can be pumped down the casing string B, unseating the valve head 33 from the cylindrical seat 34, and passing through the ports 40 and screen 42, and out of the shoe A, whereupon the cement slurry will flow upwardly around the casing` string B. When the pressure internally of the casing string is relieved, after all of the required cement slurry has been deposited behind the casing, 4the tendency of the cement slurry to ow back will again shift the head 33 into its seat 34, preventing such back ow. Normally, the hydrostatic head attributable to the cement slurry will not be suiiiciently greater than the hydrostatic head of fluid internally of the casing string to elevate tte valve member 56 to a position opening the upper body ports.

Assuming that the casing B has been lowered to the proper depth in the well bore, and that it is partially iilled with the well bore liquid, the casing can then be completely filled with uid and the pumps statred, to exert pressure on this uid. Such pressure action will unseat the valve head 33 and dispose it below its seat 34. However, it' the fluid volume pumped down thecasing string is sufciently great, back pressure will be built up of sufficient value to overcome the shear strength of the screws 53 securing the lower seat 52 to the valve housing 24. These screws are thereby disrupted, which then allows the entire valve mechanism 27 inside the housing 2.4 to be ejected therefrom, as illustrated in broken lines in Fig. l. This ejecting action removes the retaining arm 23 from the shoe and frees the ball valve member 22 allowing it to move upwardly into engagement with the seal ring 19. The valve member 22 is now available to function in its normal manner, which is to prevent return ow of fluids back into the well casing. Accordingly, cement slurry now pumped down the casing will ilow around the valve member 22, which is shifted downwardly away from its companion seat 19, resting upon a transverse stop pin Si? disposed Itherebeiow, flowing out of the shoe A and up around the casing string B. When the desired quantity of cement slurry has been displaced, any tendency for its back ilow up through the shoe housing 24 and into the casing string i3 is precludedl by upward seating of the ball 22 against the seal ring 19.

In the form of apparatus disclosed in Figs. 7 to 9, the differential valve mechanism 27a is disposed within a sub or collar D threadedly secured to upper and lower pipe or casing sections E, F, to hold the latter in spaced relation. A housing or cage 24a is disposed in this collar, the cage having an upper portion 81 containing a pair of side seals 82 for engagement with the inner wall of the collar D, to prevent leakage therealong in both longitudinal directions. The cage 24a may be skeletonizcd, as by connecting its upper portion 81 with its lower portion 83 through a plurality of longitudinally extending ribs 84. These ribs may have a shoulder 85 thereon engageable with a companion shoulder 86 in the collar for supporting the housing 24a against downward movement therewithin. Upward movement of the housing 24a may be prevented by engagement of its upper end with the pin end 87 of the upper pipe section E.

A spider 8S is disposed in the lower portion 33 of the housing. lt includes a flange portion 89 resting upon a split snap ring 90 disposed in a housing groove 91, to prevent downward movement of the spider. This spider has radial ribs 92 interconnecting its central guide portion 93 and its rim portion 94, such ribs acting as a spring seat supporting a helical compression spring 95 surrounding the upper portion of the guide 95, and with its upper end bearing upon a valve body member 28a having an upper 'head 33a disposable within `the cylindrical seat 34a of the housing, and a depending stem portion 39a encompassed by the spring 95 and slidable Within the guide 93. The stem 39a and head portion 33a are interconnected by a plurality of ribs 96 providing passages or ports 97 therebetween for the ow of fluid.

The spring 95 urges the body head 33a in an upward direction and into the cylindrical housing seat 34a, such upward movement being limited by engagement of a head shoulder 98 with the underside 48a of the upper housing portion. Leakage around the exterior of the head in bot-h longitudinal directions is prevented by a seal ring 35a, such as a rubber O ring, in a housing groove 36a and slidably engaging the cylindrical periphery of the head 33a.

A differential valve member 56ar is slidably mounted in the valve body member 28a. This valve member 56a in cludes an upper head or piston 64a of cylindrical shape slidable within a cylindrical seat 99 in the valve body head 33a, leakage between the two in both longitudinal directions being prevented by one or more side seats 100 disposed in one or more ring grooves 101 in the body 'head and slidably engaging the periphery of the valve head 64a. A valve stem 57a is secured to, or is integral with, the head 64a and depends therefrom into a cylindrical bore 102 in the body stem 39a, which bore 102 is of a substantially smaller diameter than the diameter of the cylindrical seat 99 in the body head 33a. Leakage of fluid in a downward direction into the small cylinder portion below `the valve stem 57a is prevented by one or more seal or piston rings 103 disposed in one or more grooves 104 in the valve stem and slidably engaging the wall of the small cylinder 102. These rings 193 prevent any liquid from being disposed below the valve stem 57a, such region being occupied by air at substantially atmospheric pressure.

The parts initially occupy the position illustrated in Fig. 7, in which the body head 33a is disposed within the housing seat 34a, the valve head 64a. being disposed within its companion seat 99. The device is lowered through the Fluid in the well bore, the hydrostatic head of Huid externally of the string of conduit or pipe flowing upwardly through the lower pipe section F, through the spider 8S, and in through the passages 97 between the body ribs 96 for upward action over the annular area T on the underside of the valve head 64a between the cylindrical seat 99 and the valve stem 57a. Such fluid under pressure can shift the valve head 64a upwardly to a position limited by its engagement with a stop pin 105 ex tending across the housing 28a, in which the head 64a is completely removed from its companion cylindrical seat 99, allowing uid to tiow through the seat 99 and up into the upper pipe sections E (see broken line position, Fig. 7). The uid thus flowing into the pipe or conduit E above the valve device acts downwardly over the upper head across its cross-sectional area U, urging the valve head in a downward direction. When `the internal hydrostatic head of fluid reaches a particular value with respect to the hydrostatic head externally of the well conduit, it will shift the valve member 56a downwardly back into the cylindrical seat 99, precluding further passage of uid upwardly through the differential valve device and into the upper pipe sections E.

A balanced valve arrangement is obtained when the hydrostatic head of liuid internally of the pipe sections E acting over the larger area U equals the hydrostatic head ol liuid externally of the pipe acting over the lower and smaller annular area T. This balanced valve arrangement may be expressed in the following equation:

in which Pi is the hydrostatic head externally of the string ot pipe acting over the area T and P2 is ythe hydrostatic head of fluid internally of the pipe acting downwardly over the area U. It is apparent from the above equation that the valve member 56a will be shifted downwardly to close the differential valve when the hydrostatic head Pz is substantially less than the hydrostatic head Pi. Accordingly, the fluid in the well bore can rise through the dilerential valve device only to a predetermined level, which will be substantially lower than the fluid level externally of the pipe.

In the event it is desired to pump downwardly through the pipe, the latter is lled with fluid and the pumps at the top of the well bore started, which forces the body head 33a downwardly from its seat 34a against the action of the spring 95, as illustrated in Fig. 8, the fluid tiowing around the body head 33a, down through the spider 8S and into the lower pipe sections F. When such fluid pressure is relieved, the spring will re-seat the body head 33ar within its companion cylindrical seat 34a, preventing upward passage of fluids around the body head. So long as the hydrostatic lhead of fluid within the string of pipe E is suiciently great, any greater pressure in the string of pipe F below the valve device will be incapable of shifting the valve member 56a upwardly to open position.

The inventors claim:

l. In well apparatus: a tubular member having a iluid passage therein; said tubular member having connecting means thereon for attaching said tubular member to the lower end of a conduit section forming part of a conduit string to be disposed in a well bore; a first valve member for closing said passage; a second valve member in said first. valve member for closing said passage; means providing a confined space between said first valve member and second valve member into which linid cannot enter when said tubular member is in a fluid medium, whereby said second valve member has a total first fluid pressure actuatable surface subject to the pressure of tiuid above said valve member lonly to urge said second valve member' downwardly to passage closing position, and said second valve member has a total second tiuid pressure actuatable surface subject to the pressure of iiuid below said valve members only, when said second valve member is in both closed and open positions, to urge said second valve member upwardly to passage opening position; the area of said first surface being substantially greater than the area of said second surface when said second valve member is in both open and closed positions.

2. In well apparatus: a tubular tmember having connecting means thereon for attaching said tubular member to the lower end of a conduit section forming part of a conduit string to be disposed in a well bore; said tubular member having a tirst valve seat; a first valve member engageable with said seat and having a, second valve seat; a second valve member movable yinto and out of engagement with said second seat; means providing a confined space between said first valve member and second valve member into which fluid cannot enter when said tubular member is in a fluid medium, whereby said second valve member has a total first fluid pressure actuatable lsurface subject to the pressure of-lluid at one side of said second valve member only to urge said second valve member into engagement with said second seat, and said second valve member has a total second fluid pressure actu-stable surface subject to the pressure of fluid on the other side of said second valve member only, when said second valve member is both engagedwith and disengaged from said second seat, 'to `urge said second valve member out of engagement with said second seat; the area of ysaid first surface being substantially greater than the area of said second surface when said second valve member is both engaged with and disengaged from said second seat.

3. In well apparatus: va 'tubular member having connecting means thereon for `attaching said tubular member to the lower end of a conduit section forming part of a conduit string to be disposed in a well bore; said tubular member having-a first valve seat; la valve body movable longitudinally of said member into and out of engagement with said seat; a second valve seat in said body; a valve member movable into and out of engagement with said second seat in the opposite directions to the respective directions in which said v-alve body moves into and out of engagement with said rst seat; means providing a confined space between said bodyvand valve member into which fluid cannot enter when said tubular member is in a fluid medium, whereby said valve member has a total first fluid pressure :actuatable surface subject to the pressure of fluid at one side of said valve member only to urge said valve member into engagement with said second seat, vand said valve member has a total second fluid pressurc actuatable surface .subject to the pressure of luid on the other side of said valve memberonly, when said second valve member is both engaged with .and disengaged from said second seat, to urge said valve Vmember out of engagement with said second seat; the area of said first surface being substantially gneater than the area of said second surface when Isaid valve member is both engaged with and disengaged from said second seat.

4. ln well apparatus: a 4tubular member having a lluid passage therein and an inlet disposed centrally of said member and communicating with said passage; said tubular member having connecting means thereon for =attaching said tubular member to the lower end of a conduit section forming part of a conduit string to be disposed in 'a well bore; a valve member movable in said inlet to open and close said passage; means providing a conlined space between said tubular membervand valve member into which fluid cannot enter when said tubular member l. is in a fluid medium, whereby said valve member has a total first fluid pressure actuatable surface subject to the pressure of fluid onthe downstream side of said valve member only to urge said valve member into said inlet to close said passage, and said valve member has a total second central fluid pressure actuatable surface subject to the pressure of iluid' on theupstream side of said valve member only, when said valve member is in both open and closed positions, to urge said valve member out or said inlet to allow flow of lluid through said inlet and into said passage; the area of said first surface being substantially gneater than the area of said second surface when said valve member is in both open and closed positions.

5. In well apparatus: a tubular member having a iluid passage therein and an inlet disposed centrally of said member and communicating with said passage; said tubular member having connecting means thereon for attaching said tubular member to the lower end of a conduit section forming part of a conduit string to be disposed 10 in a well bore; a valve member having a lower relatively small diameter piston portion movable downwardly into said inlet to close the same; means providing a confined space between said tubular member and valve member into which fluid cannot enter when said tubular member is in a iluid medium, whereby said piston portion has `a downwardly facing fluid pressure actuatable surface subject to the pressure of fluid below said valve member only, when said piston portion is both in and out of said inlet, to urge said valve member upwardly out of said'inlet to open said passage, and said valve member has an upper piston portion of substantially greater diameter than said lower portion and subject to the pressure of fluid above the valve member only to urge vthe valve member downwardly into said inlet to close said inlet.

6. ln well :apparatus: a tubular member having a lluid passage therein and a cylindrical inlet communicating with said passage; said tubular member having connecting means thereon for attaching said tubular member to the lower end of a conduit section forming part of a conduit string to be disposed in a well bore; said tubular member having a cylinder of greater diameter than said cylindrical inlet opening to the downstream side of said tubular member; a valve member in lsaid tubular member having a lower piston portion slidable into and out of said cylindrical inlet to close and open the same; means providing a confined space between said tubular member and said valve member into which fluid cannot enter when said tubular member is in a lluid medium, whereby said lower piston portion is exposed to the pressure of fluid on the upstream side of said valve member only, when said piston member is both in and out of said inlet, to urge said valve member in a downstream direction to open said inlet, and said v-alve .member has a piston portion slidable in said cylinder and subject vto the pressure of lluid on the downstream side of said tubular member only to urge said lower piston portion into said inlet.

7. In well apparatus: a tubular member having a lluid passage therein land an inlet communicating with said passage; said tubular member having connecting means thereon for attaching said tubular member to the lower end of a conduit section forming part of a conduit string to be disposed in a well bore; said tubular member having a cylinder of greater diameter than said inlet opening to the downstream side of said tubular member; a Valve member in said tubular member having a head movable to and from said inlet to close and open the same; means providing a confined space between said tubular member and valve member into which fluid cannot enterfwhen said tubular member is in a fluid medium, whereby said head is exposed to the pressure of fluid on the upstream side of said tubular member only to urge said valve member in a downstream direction to open said inlet, and said valve member has a piston portion shiftable in said cylinder subject to the pressure of fluid on the downstream side of said tubular member only to urge said head in an upstream direction to close said inlet.

8. In well apparatus: a tubular member having a tluid passage therein, a cylindrical inlet communicating with said passage and a side port above said inlet providing an outlet from said passage; said tubular member having connecting means thereon for attaching said tubular member to the lower end of a conduit section forming part of a conduit string to be disposed in a well bore; said tubular member having a cylinder above said port of greater diameter than said inlet and having an upper opening; a valve member in said tubular member having a lower head portion movable into and out of engagement with said inlet to close and open ythe Same; means providing a confined space between said tubular member and valve member through which lluid cannot enter when said tubular member is in a lluid medium, whereby said head is exposed to the pressure of fluid below said valve member only to urge l1` said valve member upwardly out of engagement with said inlet to open the same, and said valve member has a piston portion slidable in said cylinder and subject to the pressure of fluid thereabove only to urge said valve member downwardly to place said head in closed position with respect to said port.

9. In well apparatus: a tubular member having connecting means thereon for attaching said tubular member to the lower end of a conduit sectionforming part of a conduit string to be disposed in a well bore; said tubular member having a first valve seat; a valve body movable longitudinally of said member into and out of engagement with said seat; spring means engageable with said body to urge said body into engagement with said seat; frangible means releasably securing said spring means to said tubular member; a second valve seat in said body; a valve member movable into and out of engagement with said second seat in the opposite directions to the respective directions in which said valve body moves into and out of engagement with said first seat; means providing a 4confined space between said body and valve member into which lluid cannot enter while said tubular member is in a fluid medium, whereby said valve member -has a total first uid pressure actuatable surface subject to the pressure of fluid at one side of said valve member only, when said valve member is both engaged with and disengaged from said seat, to urge said valve member into engagement with said second seat, and said valve member has` a total second fluid pressure actuatable surface subject to the pressure of fluid on the other side of said valve member only to urge said valve member out of engagement with said second seat; the area of said first surface being substantially greater than the area of said second surface when said valve member is both engaged with and disengaged from said second seat.

10. In well apparatus: a tubular member having connecting means thereon for attaching said tubular member to the lower end of a conduit section forming part of a conduit string to be disposed in a well bore; said tubular member having a valve seat; a valve body movable upwardly into engagement with said seat, said body having a fluid passage therein and an inlet communicating with said passage; said body having a cylinder above said inlet of greater diameter than said inlet and having an upper opening; a valve member in said body having a lower head portion movable into and out of engagement with said inlet to close and open the same; means providing a confined space between said body and valve member through which fluid cannot enter when said tubular member is in a fluid medium, whereby said head is exposed to the pressure of fluid below said valve member only to urge said valve member upwardly out of engagement with said inlet to open the same, and said valve member has a piston portion slidable in said cylinder and subject to the pressure of fluid thereabove only to urge said valve member downwardly to place said head in closed position with respect to said inlet; and spring means bearing between said tubular member and body for urging said body upwardly into engagement with said seat.

11. In well apparatus: a tubular member having a fluid passage therein; a first valve member for closing said passage; a second valve member in said first valve member for closing said passage, said second valve member 'having a first fluid pressure actuatable surface subject to the pressure of uid above said valve members to urge said second valve member downwardly to passage closing position, said second valve member having a second fluid pressure actuatable surface subject to the pressure of fluid below said valve members to urge said second valve member upwardly to passage opening position; the area of said first surface being substantially greater than the area of said second surface; back pressure valve means in said tubular member for preventing upward ow of fluid in said tubular member; holding means secured to said first valve member and engageable with said back pressure valve means to prevent said back pressure valve means from closing; and means operatively associated with said first valve member and releasable by fluid pressure in said tubular member above said valve members to shift said first valve member and holding means to a position allowing said back pressure valve means to close.

12. In well apparatus: a tubular member having a fluid passage therein and an inlet disposed centrally of said member and communicating with said passage; a valve member movable in said inlet to open and close said passage, said valve member having a first fluid pressure aetuatable surface subject to the pressure of fluid on the downstream side of said valve member to urge said valve member into said inlet to close said passage, said valve member having a second central fluid pressure actuatable surface subject to the pressure of fluid on the upstream side of said valve member to urge said valve member out of said inlet to allow flow of fluid through said inlet and into said passage; the area of said first surface being substantially greater than the area of said second surface; back pressure valve means in said tubular member for preventing ow of fluid in a downstream direction in said tubular member; and holding means engageable with said back pressure valve means to prevent said back pressure valve means from closing and operatively associated with said valve member to be shifted to a position allowing said back pressure valve means to close in response to fluid pressure downstream of said valve member imposed on said valve member.

References Cited in the tile of this patent UNITED STATES PATENTS 21,535 Hardy Sept. 13, 1858 1,361,581 Hibner Dec. 7, 1920 1,719,028 Standlee July 2, 1929 1,779,065 Grant Oct. 21, 1930 2,270,838 Langdon Jan. 20, 1942 2,343,901 Groves Mar. 14, 1944 2,393,589 Compton Jan. 29, 1946 2,630,178 Brown Mar. 3, 1953 FOREIGN PATENTS 808,769 France of 1930