US2718265A

US2718265A - Apparatus for automatically filling well casing

Info

Publication number: US2718265A
Authority: US
Inventors: Martin B Conrad
Original assignee: Baker Oil Tools Inc
Current assignee: Baker Hughes Oilfield Operations LLC
Priority date: 1950-11-25
Filing date: 1950-11-25
Publication date: 1955-09-20
Anticipated expiration: 1972-09-20

Description

Sept. 20, 1955 M. B. CONRAD APPARATUS FOR AUTOMATICALLY FILLING WELL CASING Filed Nov. 25, 1950 2 Sheets-Sheet l INVENTOR.

ArmeA/E Y5 MAET/N B- Come/10,

Sept. 20, 1955 B. CONRAD APPARATUS FOR AUTOMATICALLY FILLING WELL CASING Filed NOV. 25, 1950 2 Sheets-Sheet 2 INVENTOR. MAer/A/ B. Come/10,

4rroxe/vsys United I States Patent Martin. B. C nrad, Downey, Ca fi, assi o to ker Qi Tools, Inc., Vernon, 'Califl, a corporation of California Application November 25, 1950, Serial No. 197,542

.26 C aims (Gl- 16 -22 The present invention relates to subsurface well apparatus, and more particularly to apparatus for controllably filling a string of well casing, or the like, as it is lowered through the fluid in the well bore.

In running a string of well casing in a well bore, it has been usual practice to cause the well fluid to sustain a portion of the weight of the casing string by floating the string in the well fluid, through the expedient of maintaining its interior in a substantially empty state. The well fluid is ordinarily prevented from entering the casing string by an upwardly closing check valve, which later accomplishes the purpose of preventing cementitious material, such as cement slurry, pumped down and around the casing string, from reentering the latter.

in running comparatively long strings of casing in the well bore, the hydrostatic head of fluid acting on the lower portion of the casing may be very high andmay collapse the casing. To oft-set this p0ssibility, it is usual practice to place the same type of drilling fluid that may be present in the well bore inside the casing string up to a desired elevation, lower than the level of fluid in the well bore. This decreases the diflerential hydrostatic head on the casing, while still maintaining a large degree of buoyancy in the casing string, to continue its floating in the well bore during lowering to its final position,

An object of the present invention is to automatically fill the casing string to predetermined elevations below the level of the Well fluid surrounding the casing string as the latter is lowered in the well bore.

Another object of the invention, is to cause the well fluid itself to effect automatic filling of the casing string to predetermined levels as it is lowered in the well bore. -A further object of the invention is to provide a float shoe orfloat collar that can form part of a well casing string, which is effective to automatically fill the casing string to particularlevels as it is lowered in the well bore, andin which the back pressure valve of the shoe or collar .is still effective to. prevent return flow of cement slurry, .or other fluids, into the well casing after the latter has been landed 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 maybe 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 he understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure l is a longit dinal section thr u h an emb dime t o the n e t n. with t e pa s th pos on they o c py while l r ng the equipmen hrou th fluid the we l bo Fig. 2 is an enlarged longitudinal section illustrating the automatic ca n fi lp device n closed p si n; Fig, 3 is a view similar to Fig. 1, disclosing the auto- 2,718,265 Patented Sept, 20;, 1955 2 matic casing filling portion of the device ejected from the casing shoe;

Fig. 4 is a cross-section taken along the line 44 on Fig 2; i

Fig. 5 is a fragmentary longitudinal section illustrating the casing filling valve sealing arrangement;

Fig. 6 is a longitudinal section through a modified form of apparatus;

Fig. 7 is a longitudinal section through another embodiment of the invention;

Fig 8 is a fragmentary longitudinal section showing another mannerof attaching the valve body to the valve housing.

The apparatus disclosed in Figs. 1 to 5, inclusive, is a casing shoe A adapted to be threaded, or otherwise suitably attached, to a casing section B thereabove; so as to form the terminal end of a casing string to be lowered in a well bore C. If the apparatus A is placed in an intermediate portion of the casing string, it would operate inthe same manner, but would then be considered as a casing collar.

The device A includes an outer tubular member 10, usually made of steel, having an upper threaded box 11 for attachment to the adjacent casing section B. This tubular member is provided with a series of upper internal grooves 12 for securing an upper cementitious plug 13 to it, as a result of casting the plug directly in the tubular member. This plug has a central passage 14 in alignment with a passage 15 through a valve seat 16 disposed in the lower portion of the plug 13.

A back pressure valve element 17, that may be in the form of a ball buoyant in cement slurry, is disposed in the shoe below the seat 16, being movable upwardly into engagement with the latter to prevent upward flow of fluid into the well casing B. For the purpose of preventing leakage around the ball, when seated, it engages a suitable seal ring 18 clamped between the valve seat 16 and a spacer sleeve 19 extending from the upper plug 13 to a lower plug 20 of cementitious materiahwhich is anchored to the tubular member 10 by means of its external ribs 21 cast into internal grooves 22 in the tubular member.

The lower end ofthe spacer sleeve 19 engages a shoulder 23 on a stop member 24 seating in the lower cementitious plug 20, this member having a plurality of lugs or fingers 25 on which the ball valve element 17 can rest when fluid is being pumped downwardly through the casing string B and its casing shoe A. The valve seat 16, spacer sleeve 19 and stop member 24, in efi'ect, form a valve cage containing the ball valve element 17.

The lower cementitious plug 20 may have a lower rounded nose 20a for guiding the casing string past any obstructions or restrictions in the well bore.

Apparatus of the general type so far described is known. During lowering of the casing string B in the well bore C, the drilling fluid, or other liquid, in the well bore would be prevented from entering the interior of the casing string, in view of the upward engagement of the valve element 17 against its companion seat 16 and seal 18. As a result, the interior of the casing string does not conta n a y fi id- As the ca i String i owere to grea er depths in the well bore, the hydrostatic head of liquid acting on the exterior of the shoe and the lower portions of he asin s ri B incr e .I e p Wells, hi drqst t c head ma e s ext n s to n t c lapse t e ca str h TO fo s h s i v th C sin string has heretofore been filled with fluid from the top o he ll o e, c tin a h dros bac p es re setting t he external hydrostatic head and reducing to a safe yalue the differential pressure tending to collapse the lo er PQ iOH 0 the casing string n y- By means of the devices disclosed in this application,

the well fluid itself is instrumental in allowing its entry into the well casing, to provide a column of liquid within the casing string that rises to a lesser elevation than the height of the liquid in the well bore surrounding the casing. In this manner, the differential hydrostatic head tending to collapse the casing is decreased, but the casing itself can be maintained empty to a large degree; to assist in floating it in the well bore while it is being low- I ered to its ultimate position.

As disclosed in the drawings, fluid can enter the well casing B through the casing shoe A whenever permitted to do so by a differential valve device D, which is opened or closed in dependence upon the proportionate hydro-- static heads of fluid within and outside of the casing string. This valve device includes a tubular valve housing 30 disposed in the lower cementing plug 20 coaxial of the central passage 14 through the upper plug, being secured to the plug 20 by inner ribs 31 in the latter cast within external grooves 32 in the housing. A valve body 33 is disposed in this housing, including a lower series of circumferentially spaced longitudinally extending ribs 34 engaging the inner wall of the sleeve 30, the spaces 35 between the ribs providing passages for fluid to flow from the exterior of the shoe A upwardly into its interior. From these passages 35, the fluid can flow to the interior of the body 33 through a plurality of body ports 36, the fluid then passing upwardly through a generally cylindrical valve seat 37 in the body, and into the upper cylindrical portion 33a of the body that may project within the stop member 24. Leakage between the housing and exterior of the upper body portion 33a is prevented by a suitable side seal 38 in the housing engaging the exterior of the upper body portion.

The ability of the external well fluid to flow upwardly into the shoe, in the manner just described, is dependent upon the open or closed position of a valve member 39, which open or closed position is governed automatically by the differential pressure existing between the hydro- 5 static head of fluid externally of the casing B and the hydrostatic head of fluid internally of the casing. The valve member 39 itself includes a valve head 40 having a cylindrical periphery adapted to be disposed within the cylindrical body seat 37, for the purpose of preventing upward passage of fluid into the casing shoe. When in this position, leakage around the valve head 40 is prevented by engagement of its periphery with a seal ring 41 disposed in a groove 42 in the valve seat 37. The ring is preferably of round cross-section, being received within the groove 42 having opposed side walls 43 that may be parallel to one another, or which may converge toward each other in a direction toward the axis of the device (Fig. 5); to insure retention of the seal ring 41 in the groove 42.

The valve head 40 is secured to, or is made integral with, a depending rod 44 attached to, or integral with, a lower piston 45 slidable within a cylinder 46 in the valve body having a closed lower end 47. Leakage around the periphery of the piston 45 is prevented by a suitable seal ring 48 disposed in a piston groove 49 and slidably engaging the wall of the cylinder 46. Between the piston 45 and the lower cylinder head 47 no fluid is present, this space originally being occupied by air at substantially atmospheric pressure. A stem depends from the piston 45, for the purpose of limiting downward move- 'ment of the valve member 39 to a position in which the fiuid can continue flowing through the upper portion 33a of the body, around the ball valve element 17 and through the upper plug passage 14 into the casing sections B above the shoe A. To allow such flow to occur around the ball valve element 17, the latter is initially prevented from moving upwardly into engagement with its seat 16 by a retainer arm 50 secured to the valve body 33, as by a screw 51, and holding the ball to one side of the valve seat axis, in the manner illustrated in Fig. 1. It is only when this retainer arm 50 is removed that the ball valve element 17 is allowed to move upwardly into engagement with its seat 16.

The valve body 33 and retainer arm 50 are held initially in an upward position by a shear screw 52 attaching the body 33 to the valve housing 30 (see Fig. 2). This screw may be inserted through a lateral hole 53 in the lower guiding portion of the lower plug 20 and threaded into a valve body rib 34. When in this position, the upper ends of the ribs 34 engage a shoulder 54 on the valve housing 30, and the retainer arm 50 holds the ball valve element 17 displaced to one side of a coaxial position with the seat 16.

By referring to Fig. 2 particularly, it is to be noted that the fluid externally of the Well casing B can pass upwardly through the longitudinal passages 35 and through the ports 36, entering the cylinder 46 and acting downwardly on the lower piston 45 across the annular .area B between the wall of the cylinder and the piston rod 44. This same fluid is acting upwardly on the valve head 40 over the annular area A between the valve rod 44 and the cylindrical seat 37. Any fluid in the interior of the well casing B acts downwardly on the valve head 40 over its entire cross-sectional area C.

The area A is greater than the area B, so that the hydrostatic head of fluid on the exterior of the casing string acts on a differential area of A minus B, and tends to lift the valve head 40 off its seat 37, to shift it to open position. As stated before, the hydrostatic head of fluid inside the casing acts downwardly over the valve head area C, and tends to shift the valve head 40 downwardly to closed position and maintain it in this closed position. Opening or closing of the valve, neglecting friction, is therefore dependent upon the following relationship:

P (AC B) in which P1 is the hydrostatic head externally of the easing string, and P2 is the hydrostatic head internally of the casing string B. When the hydrostatic head P externally of the casing string increases in a certain proportion above the hydrostatic head internally of the casing string, the .valve 39 will elevate to open position, allowing the well fluid to pass upwardly through the shoe A and into the casing string B, to increase the height of liquid inside the casing string, and thereby increase its head P2. When this latter head reaches a certain value, it will exert a total downward force on the valve member 39, overbalancing the force of the greater external hydrostatic head Pl. on the valve member 39, and the latter will be shifted downwardly to closed position within its cylindrical seat 37 As an example, let it be assumed that the area A is 2.3194 sq. in., the area B is 1.3990 sq. in., and the area C is 2.7612 sq. in. Substituting these constant values in the above equation, it is found that Pz equals /3 P1. In other words, under the assumed condition, when the pressure 'Pi externally of the casing string is three times the pressure P2 internally of the casing string, the valve 39 will open and allow the internal casing string pressure or hydrostatic head to increase. When this latter hydrostatic head P2 is more than one-third of the external hydrostatic head P1, it will reclose the valve automatically.

Accordingly, from the above relationship, and since for any particular design the several areas A, B, C are constant, the valve mechanism 39 will allow the well fluid to flow automatically into the casing string B and maintain a direct straight-line proportion between the internal pressure P2 and the external pressure P1. Under the assumed example, the hydrostatic head P2 inside of the well casing will be maintained at one-third the hydrostatic head P externally of the casing.

The apparatus A is secured to the lower end of the casing string B, as shown in Fig. l, with the ball valve 17 prevented from engaging its seat 16. As the casing String B is lowered through the fluid in the well bore C, the external hydrostatic head P1 elevates the valve 39 to open position, and allows the fluid to flow through the shoe A and into the casing string B. Assuming that descent of the casing string is stopped (as occurs when another section of casing is to be attached to the top of the well bore), the external hydrostatic head P1 will hold the valve 39 open until the fluid level inside the casing string reaches a predetermined point, which is preferably a fraction of the external level of fluid in the well casing; so that the well casing is kept substantially empty for the purpose of having the well fluid sustain a large portion of its weight. At this time, the internal pressure P; acting over the larger area C of the valve head 40 will shift the latter downwardly to closed position, such as disclosed in Fig. 2. Upon continuance in the descent of the string of casing in the well bore, a greater external hydro,- static head Pi will be imposed on the valve 39, causing it to again elevate to open position and allowing the hydrostatic head P2 in the interior of the casing string to increase.

After the casing string has been lowered in the well bore to the desired location and extent, the ball valve element 17 is L be freed; to permit its upward engagement with its valve seat 16. At this time, the casing string B can be filled with fluid, as from the surface of the well here, until it is completely full, whereupon pressure can be imposed on the fluid inside the casing. With the valve head 40 closed, such downward pressure cannot shift the valve 39 to any lower position, inasmuch as the stem 55 depending from the piston 45 engages the cylinder head 47. The pressure internally of the casing string is then operative over the entire area K across the upper portion 33a of the valve body, the hydraulic force acting on the frangible screw 52 to shear the latter and pump the entire automatic fill valve mechanism D downwardly out of the casing B, in the manner disclosed in Fig. 3. This ejection carries the retaining arm 50 downwardly with the valve body 3.3., and removes it from the casing shoe, freeing the ball valve element 17 for upward movement into engagement with its companion seat 16.

The well casing B may now, be cemented in place, as by pumping cement slurry down the casing string, the ball valve element 17 resting on the supporting lugs 25 while the cement slurry is passing around it and out through the lower end of the shoe A for upward passage around the exterior of the casing string B. When the pressure inside the casing is relieved, the tendency for the cement slurry to flow back into the casing is prevented by upward movement of the ball valve element 17 into engagement with its seat 16.

Accordingly, it is apparent that the device D allows the casing string B to fill automatically with fluid as it is lowered with the well bore, while maintaining a definite ratio between the hydrostatic head or pressure P exter nally of the casing string and the head P2 internally of the casing string, the latter head preferably being only a fraction of the external head P1. In this manner, the pressure differential on the lower portion of the casing string is prevented from becoming excessive, thereby precluding the possibility of collapsing of the casing. Despite the permitting of the fluid to flow upwardly into the casing string, the back pressure valve 17 is still later effective to prevent return flow of cement slurry, or other fiuent substances, into the casing string B'after having been ejected therefrom.

In Fig. 8, a modified form of release for securing the valve body 33 to the valve housing 3.0 is disclosed. In.-

stead of inserting the shear screw 52 through a hole 53 in the cementitious plug 20, the valve body 33 may have an arcuate lower sleeve like portion 33b engaging the .wall of the housing 30. This sleeve-like portion hasv a threaded hole 60 in alignment with a threaded bore, 61 in the lower end of the housing 30. A shear screw 52a can readily be inserted from the interior of the housing into these threaded

holes

60, 61 for the purpose, of detachably securing the body 33 to the housing 3.0. By virtue of this arrangement, assembly of; the body 33 to the boll ing 30 is facilitated.

In the form of invention illustrated in Fig. 6, a guide shoe H is attached to the lower end of the casing string B. This shoe does not have a float valve, but in all other respects the differential valve D is the. same as disclosed in the Fig. 1 to Fig. 5 device. The valve mechanism D is effective to. control the flow of the well fluid into the casing string B until the predetermined ratio between the internal and external hydrostatic heads of fluid exists. After the casing string has been landed in the well bore, it is only necessary to fill the casing string and impose internal pressure on the fluid therewithin, which will shear the screw 52 and eject the valve body 33 and the. movable valve element 39 itself from the shoe housing 30, opening the passage through the latter so that fluent substances can be pumped downwardly and out through the casing shoe.

In the form of invention shown in Fig. 7, a differential valve device is illustrated as forming part a float collar E threadedly secured to upper and lower casing sections F, G to hold them in spaced relation. The parts are essentially the same as in the other form of invention, except that the head of fluid externally of the casing can enter the collar through the lateral ports in the tubular collar member 10a. The valve body 33d is initially secured to .the valve housing 30d, that is anchored in the lower cementitious plug 20d, by one or more shears screws 71 extending between a depending portion of the housing and the valve body. The valve body 33d itself is provided with a cylinder portion 46d and with an upper tapered Valve seat 37d engageable by a tapered valve head AM. A stem 44d depends from this head, the lower ,end of which is secured to a piston 45d slidable in the cylinder 46d and carrying one or more seal rings 48d in ring grooves 49d. The cylinder space below the piston 45 1 i preferably occupi d by ai ginally at a m sph ri pressure.

An arm 50d is secured to the valve body 3341 and extends upwardly into engagement with the ball valve element 17 to hold it off its seat 16. As in the other form .of invention, the area R between the valve stem and the sealing point of the valve head 40d against the seat 37d is greater than the annular area S across the piston. The area T across the valve head 40d corresponds to the area .C in the other forms of the invention.

The same relationship exists as was specified in connection with the other form of the invention, and which may be expressed in the following equation:

Since R, S and T ar con ant here s a direct and straight-line proportion between the hydrostatic head internally of the casing string, P2, and the hydrostatic head of fluid externally of the casing string, P1.

A he casing s lowered thr g th flui in the wel bore, the fluid can enter the valve mechanism through the housing ports 73 and through the body ports 7 into the annular space 75 between the wall of the cylinder 46d and valve stem 44d. This pressure will elevate .thQValve head 40d from its seat and allow the fluid to flow upwardly into the casing string. When the fluid level inside the casing string rises to a point in which an equalized condition is obtained under the above equation, the valve 40d will be shifted downwardly by the internal pressure to closed position.

After the casing has been lowered to its final position in the well bore, it may be completely filled with fluid and pressure applied to the latter sufficient to overcome the shear strength of the screws 7|, releasing the valve body 33d and blowing the differential valve mechanism D and arm 50d downwardly out of the collar E, opening the central passage 80 through the valve housing 30d to allow downward flow of fluid therethrough. At the same time, the restraint on the ball valve element 17 is released, which will allow the latter to move upwardly into engagement with its seat 16, in the event back flow of fluid into the well casing tends to occur.

The inventor claims:

1. In well apparatus: a tubular member having a fluid passage therein and having means thereon for securing said member in a conduit string to be lowered in a well bore; said passage having an outlet adapted to communicate with the conduit string above said member and an'inlet below said outlet; a valve member between said inlet and outlet for closing said passage, said valve member having a first fluid pressure actuatable surface subject to the pressure of fluid above and on the outlet side of said valve member to urge said valve member downwardly to passage closing position, said valve member having a second resultant fluid pressure actuatable surface, when said valve member is in open position, which is subject to the pressure of fluid below and on the inlet side of said valve member to urge said valve member upwardly to passage opening position; the area of said first surface being substantially greater than the resultant area of said second surface.

2. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be lowered in a well bore; means securing a valve body in said member; a valve seat on said body; a valve member movable into and out of engagement with said seat; said valve member having a first fluid pressure actuatable surface subject to the pressure of fluid internally of said tubular member to urge said valve member into engagement with said seat, said valve member having a second fluid pressure actutatable surface subject to the pressure of fluid externally of said tubular member to urge said valve member out of engagement with said seat when said valve member is disengaged from said seat, the area of said first surface being substantially greater than the area of said second surface when said Valve member is disengaged from said seat.

3. In well apparatus: a tubular member having means thereon for securing said member in a casing string, said member having a fluid passage; valve means coacting with said passage for determining the flow of fluid through said passage between the exterior and interior of said tubular member; said valve means having a first fluid pressure actuatable surface subject to the pressure of fluid in the casing string above said tubular member to urge said valve means to passage closing position, said valve means having a second fluid pressure actuatable surface subject to the pressure of fluid eX- ternally of the casing string to urge said valve means to passage opening position; the area of said first surface being substantially greater than the area of said second surface acted on by fluid externally of the casing string with the valve means in open position.

4. In well apparatus: a tubular member having means thereon for securing said member in a casing string, said member having a fluid passage; valve means coacting with said passage for determining the flow of fluid through said passage between the exterior and interior of said tubular member, said valve means being movable longitudinally of said tubular member between open and closed positions; said valve means having an upwardly facing fluid pressure actuatable surface subject to the pressure of fluid in the casing string above said tubular member to urge said valve means downwardly to passage closing position; said valve means having a downwardly facing fluid pressure actuatable surface subject to the pressure of fluid externally of said casing string to urge and maintain said valve means upwardly in passage opening position, the pressure actuatable area of said upwardly facing surface being substantially greater than the pressure actuatable area of said downwardly facing surface when said valve means is in passage opening position.

5. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be lowered in a well bore; a valve body in said member; a valve seat on said body; a valve member movable into and out of engagement with said seat; said valve member having a first fluid pressure actuatable surface subject to the pressure of fluid internally of said tubular member to urge said valve member into engagement with said seat, said valve member having a second fluid pressure actuatable surface subject to the pressure of fluid externally of said tubular member to urge said valve member out of engagement with said seat, the area of said first surface being substantially greater than the area of said second surface; and means, releasable by hydraulic pressure within said tubular member imposed upon said valve member and body when said valve member engages said seat, for securing said valve body to said tubular member, release of said means enabling said valve body and valve member to be shifted within said tubular member to a position in which said valve body and valve member are ineffective to control passage of fluid in said tubular member thereby allowing fluid to flow in both directions in said tubular member.

6. In well apparatus: a tubular member having means thereon for securing said member in a conduit string to be lowered in a well bore; a valve body in said member; a valve seat on said body; a valve member movable into and out of engagement with said seat; said valve member having a first fluid pressure actuatable surface subject to the pressure of fluid internally of said tubular member to urge said valve member into engagement with said seat, said valve member having a second fluid pressure actuatable surface subject to the pressure of fluid externally of said tubular member to urge said valve member out of engagement with said seat, the area of said first surface being substantially greater than the area of said second surface; and frangible means securing said valve body to said tubular member, disruption of said frangible means enabling said valve body to be shifted within said tubular member to a position in which said valve body and valve member are ineffective to control passage of fluid in said tubular member thereby allowing fluid to flow in both directions in said tubular member.

7. In well apparatus: a tubular member; a valve body in said member; a valve seat on said body; a valve member movable into and out of engagement with said seat; said valve member having a first fluid pressure actuatable surface subject to the pressure of fluid internally of said tubular member to urge said valve member into engagement with said seat, said valve member having a second fluid pressure actuatable surface subject to the pressure of fluid externally of said tubular member to urge said valve member out of engagement with said seat, the area of said first surface being substantially greater than the area of said second surface; means, releasable by hydraulic pressure within said tubular member imposed upon said valve member and body when said valve member engages said seat, for securing said valve body to said tubular member, release of said means enabling said valve body and valve member to be shifted within said tubular member to a position in which said valve body and valve member are ineflective to control passage of fluid in said tubular member; back pressure valve means in said tubular member; and means interconnecting said valve body and back pressure valve means to prevent closing of said back pressure valve means, said interconnecting means being rendered ineffective to prevent closing of said back pressure valve means upon release of said securing means and shifting of said valve body within said tubular member.

8. In well apparatus: a tubular member; a valve body in said member; a valve seat on said body; a valve member movable into and out of engagement with said seat; said valve member having a first fluid pressure actuatable surface subject to the pressure of fluid internally of said tubular member to urge said valve member into engagement with said seat, said valve member having a second fluid pressure actuatable surface subject to the pressure of fluid externally of said tubular member to urge said valve member out of engagement with said seat, the area of said first surface being substantially greater than the area of said second surface; means, releasable by hydraulic pressure within said tubular member imposed upon said valve member and body when said valve member engages said seat, for securing said valve body to said tubular member, release of said means enabling said valve body and valve member to be shifted within said tubular member to a position in which said valve body and valve member are ineffective to control passage of fluid in said tubular member; a second valve seat above said body; a valve element movable upwardly into engagement with said second seat; and means interconnecting said body and element'to prevent engagement of said element with said second valve seat, said interconnecting means being rendered ineffective to prevent engagement of said element with said second valve seat upon release of said securing means and shifting of said valve body within said tubular member.

9. In well apparatus: a tubular member adapted to form part of a casing string positionable in a well bore; a valve body in said tubular member having a passage surrounded by a valve seat, said passage having an inlet below said seat; a valve head in said body movable T downwardly into engagement with said seat; said body providing a cylinder below said seat communicating with said passage inlet when said valve head engages said seat; a piston secured to said head and slidable in said cylinder; said cylinder being closed below said piston to prevent entry of fluid thereinto while said apparatus is in the well bore; said head having an upwardly facing fluid pressure actuatable surface subject to the pressure of the casing fluid above said head and said head and piston having a resultant downwardly facing fluid pressure actuatable surface subject to the pressure of the well fluid externally of said tubular member when said valve head engages said seat; said upwardly fac ing surface having a substantially greater area than said resultant downwardly facing surface; and means releasable by fluid pressure acting downwardlyon said head for securing said body to said tubular member.

10. In well apparatus: a tubular member adapted to form part of a casing string positionable in a well bore; a valve body in said tubular member having a passage surrounded by a valve seat, said passage having an inlet below said seat; a valve head in said body movable downwardly into engagement with said seat; said body providing a cylinder below said seat communicating with said passage inlet when said valve head engages said seat; a piston secured to said head and slidable in said cylinder; said cylinder being closed below said piston to prevententry of fluid thereinto while said apparatus is in the well bore; said head having an upwardly facing fluid pressure actuatable surface subject to the pressure of the casing fluid above said head and said head and piston having a resultant downwardly facing fluid; pressure actuatable surface subject to the pressure of th Well fluid externally of; said tubular member when said valve head engages said seat; said upwardly facing surface having a substantially greater area than said resultant downwardly facing surface.

11. In well apparatus: a tubular member adapted to form part of a casing string positionable in a well bore; a valve body in said tubular member having a passage surrounded by a valve seat and a cylinder to one side of said passage, said passage having an inlet between said seat and cylinder; a valve head in said body movable downwardly into engagement with said seat; a piston slidable in said cylinder; a rod interconnecting said head and piston and spaced from the wall of said cylinder to provide an annular space communicating with said passage; the cross-sectional area of said annular space being less than the cross-sectional area of the underside of said head between said rod and the point of engagement of said head with said seat; said cylinder having a confined space below said piston into which fluid in the well bore cannot enter.

12. In well apparatus: a tubular member adapted to form part of a casing string positionable in a Well bore; a valve body in said tubular member having a passage surrounded by a valve seat and a cylinder to one side of said passage, said passage having an inlet between said seat and cylinder; a valve head in said body movable downwardly into engagement with said seat; a piston slidable in said cylinder; a rod interconnecting said head and piston and spaced from the wall of said cylinder to provide an annular space communicating with said passage; the cross-sectional area of said annular space being less than the cross-sectional area of the underside of said head between said rod and the point of engagement of said head with said seat; said cylinder having a confined space below said piston into which fluid in the well bore cannot enter; and means releasable by fluid pressure acting downwardly on said head for securing said body to said tubular member.

13. In well apparatus: a tubular member adapted to form part of a casing string positionable in a well how; a valve body in said tubular member having a passage surrounded by a valve seat and a cylinder to one side of said passage; a valve head in said body movable downwardly into engagement with said seat; a piston slidable in said cylinder; a rod interconnecting said head and piston and spaced from the wall of said cylinder to provide an annular space communicating with said passage; the cross-sectional area of said annular space being less than the cross-sectional area of the underside of said head between said rod and the point of engagement of said head with said seat; said cylinder having a confined space below said piston into which fluid in the well bore cannot enter; means, releasable by hydraulic pressure within said tubular member imposed upon said valve member and body when said valve member engages said seat, for securing said valve body to said tubular memher, release of-said means enabling said valve body and .valve member to be shifted within said tubular member to a position in which said valve body and valve member are ineffective to control passage of fluid in said tubular member; a second valve seat above said body; a valve element movable upwardly into engagement with said second seat; and means interconnecting said body and element to prevent engagement of said element with said second valve seat, said interconnecting means being rendered ineffective to prevent engagement of said element with said second valve seat upon release of said securing means and shifting of said valve body within 'said tubular member.

14. In well apparatus: a tubular member having means at its upper end for attaching said member to an adjacent casing section forming part of a casing string;

a cementitious plug secured in said member; a housing secured in said plug; a valve body in said housing having a valve seat; a valve member in said body movable downwardly into engagement with said seat, said member having an upwardly facing surface subject to the pressure of fluid in the tubular member above said seat to urge said member into engagement with said seat, said valve member having a downwardly facing surface subject to the pressure of fluid in said tubular member below said valve member to urge said valve member upwardly out of engagement from said seat; and means releasably securing said body to said housing to enable said body and valve member to be ejected hydraulically downward from said housing.

15. In well apparatus: a tubular member having means at its upper end for attaching said member to an adjacent casing section forming part of a casing string; a cementitious plug secured in said member; a housing secured in said plug; a valve body in said housing having a valve seat; a valve member in said body movable downwardly into engagement with said seat, said member having an upwardly facing surface subject to the pressure of fluid in the tubular member above said seat to urge said member into engagement with said seat, said valve member having a downwardly facing surface subject to the pressure of fluid in said tubular member below said valve member to urge said valve member upwardly out of engagement from said seat; means releasably securing said body to said housing to enable said body and valve member to be ejected hydraulically downward from said housing; a second valve seat above said body; a valve element movable upwardly into engagement With said second seat; and means interconnecting said body and said element to prevent engagement of said element with said second valve seat, said interconnecting means being rendered ineffective to prevent engagement of said element with said second valve seat upon release of said securing means and shifting of said valve body within said tubular member.

16. In well apparatus: a tubular member having means at its upper end for attaching said member to an adjacent casing section forming part of a casing string; a cementitious plug secured in said member; a housing secured in said plug; a valve body in said housing having a passage surrounded by a valve seat and a cylinder to one side of said passage; a valve head in said body movable downwardly into engagement with said seat; a piston slidable in said cylinder; a rod interconnecting said head and piston and spaced from the wall of said cylinder to provide an annular space communicating with said passage; the cross-sectional area of said annular space being less than the cross-sectional area of the underside of said head between said rod and the point of engagement of said head with said seat; said cylinder having a confined space below said piston into which fluid in the well bore cannot enter; and means releasably securing said body to said housing to enable said body and valve member to be ejected hydraulically downward from said housing.

17. In well apparatus: a tubular member having means at its upper end for attaching said member to an adjacent casing section forming part of a casing string; a cementitious plug secured in said member; a housing secured in said plug; a valve body in said housing having a passage surrounded by a valve seat and a cyl- 1 inder to one side of said passage; a valve head in said body movable downwardly into engagement with said seat; a piston slidable in said cylinder; a rod interconnecting said head and piston and spaced from the wall of said cylinder to provide an annular space communicating with said passage; the cross-sectional area of said annular space being less than the cross-sectional area of the underside of said head between said rod and the point of engagement of said head with said seat; said cylinder having a confined space below said piston into which fluid in the well bore cannot enter; and frangible means securing said valve body to said housing to enable said body and valve member to be ejected hydraulically downward from said housing.

18. In well apparatus: a tubular member having means at its upper end for attaching said member to an adjacent casing section forming part of a casing string; a cementitious plug secured in said member; a housing secured in said plug; a valve body in said housing having a passage surrounded by a valve seat and a cylinder to one side of said passage; a valve head in said body movable downwardly into engagement with said seat; a piston slidable in said cylinder; a rod interconnecting said head and piston and spaced from the wall of said cylinder to provide an annular space communicating with said passage; the cross-sectional area of said annular space being less than the cross-sectional area of the underside of said head between said rod and the point of engagement of said head with said seat; said cylinder having a confined space below said piston into which fluid in the well bore cannot enter; frangible means securing said valve body to said housing to enable said body and valve member to be ejected hydraulically downward from said housing; a second valve seat above said body; a valve element movable upwardly into engagement with said second seat; and means interconnecting said body and said element to prevent engagement of said element with said second valve seat, said interconnecting means being rendered ineffective to prevent engagement of said element with said second valve seat upon release of said securing means and shifting of said valve body within said tubular member.

19. In well apparatus: a tubular member having a fluid passage therein and having means thereon for securing said member in a conduit string to be lowered in a well bore; said passage having an outlet and an inlet below said outlet; a valve member between said inlet and outlet for closing said passage and movable longitudinally of said tubular member between open and closed positions, said valve member having a first fluid pressure actuatable surface subject to the pressure of fluid above said valve member to urge said valve member downwardly to passage closing position, said valve member having a second resultant fluid pressure actuatable surface, when said valve member is in open position, which is subject to the pressure of fluid below said valve member to urge said valve member upwardly to passage opening position; the projected area of said first surface normal to the axis of said valve member being substantially greater than the projected area of said second resultant surface normal to the axis of said valve member.

20. In well apparatus: tubular means having a fluid passage and having means thereon for securing said tubular means in a conduit string to be lowered in a well bore; means providing a valve seat in said passage; a valve member slidable along said tubular means into and out of engagement with said seat to close and open said passage; said tubular means having a cylinder along which said valve member is slidable; said valve member and cylinder defining a cylinder space therebetween; means providing a slidable seal between said valve member and cylinder to prevent passage of well fluid on both sides of said valve member into said cylinder space; said valve member having a first fluid pressure actuatable surface subject to the pressure of fluid internally of said tubular means to urge said valve member into engagement with said seat, said valve member having a second resultant fluid pressure actuatable surface subject to the pressure of the fluid externally of said tubular means to urge said valve member out of engagement from said seat; the projected area of said first surface normal to the axis of said valve member being substantially greater than the projected area of said second surface normal to the axis of said valve member.

21L In welkapparatusz tubular means:having .a..fluid passage and Ihavin g means thereon for isecuring said -Itubular imeans'inlaconduit string to be lowered in awelli boreymeans :providinga valve seat in said passage; .a va'lve'tm'ember slidable downwardly, along saidltubu'lar means into engagement with. said-seat and upwardly alon'g saidtubular means out of engagement from said seat; said tubular means having a cylinder portion along which said valve member is slidable; said valve member and cylinder portion defining a cylinder space therebetween; means providing a slidable seal between said valve member and cylinder portion to prevent passage of well fluid on both sides of said valve member into said cylinder space; said valve member having an upwardly facing pressure actuatable resultant surface subject to the pressure of fluid above said valve member to urge said valve member downwardly into engagement with said seat, said valve member having a downwardly facing pressure actuatable resultant surface subject to the pressure of fluid below said valve member to urge said valve member upwardly out of engagement from said seat; the projected area of said upwardly facing surface normal to the axis of said valve member being substantially greater than the projected area of said downwardly facing surface normal to the axis of said valve member.

22. In well apparatus: a tubular member having a fluid passage therein and having means thereon for securing said member in a conduit string to be lowered in a well bore; a valve member for closing said passage and movable longitudinally of said tubular member between open and closed positions; said passage having an inlet within said tubular member disposed below said valve member when said valve member is in passage closing position and an outlet above said valve member; said valve member having a first fluid pressure actuatable surface subject to the pressure of fluid above and on the outlet side of said valve member to urge said valve member downwardly to passage closing position, said valve member having a second resultant fluid pressure actuatable surface, when said valve member is in open position, which is subject to the pressure of fluid below and on the outlet side of said valve member to urge said valve member upwardly to passage opening position; the area of said first surface being substantially greater than the resultant area of said second surface.

23. In well apparatus: a tubular structure having a means thereon for securing said structure in a conduit string to be lowered in a well bore; said structure having a fluid inlet and outlet; means securing a first valve member in said structure; a valve seat on said first valve member between said inlet and outlet; a second valve member movable into and out of engagement with said seat; said second valve member having a first fluid pressure actuatable surface subject to the pressure of fluid on the outlet side of said seat to urge said second valve member into engagement with said seat, said second valve member having a second fluid pressure actuatable surface subject to the pressure of fluid on the inlet side of said seat to urge said second valve member out of engagement from said seat, the area of said first surface being substantially greater than the area of said second surface; means releasably securing said first valve member to said tubular structure; back pressure valve means in said tubular structure; and means interconnecting one of said valve members and back pressure valve means to prevent closing of said back pressure valve means, said interconnecting means being rendered ineffective to prevent closing of said back pressure valve means upon release of said securing means and shifting of said first valve member within said tubular structure.

24. In well apparatus: tubular means having a fluid passage and having means thereon for securing said tubular means in a conduit string to be lowered in a well bore; a first valve member providing a valve seat in said passage; a second valve member slidable along said tubular :means into and: out of-engagenrentzwithcsaidzi seat nto' close ::andopen said. passage; izsaidertubular :mea'nsr.

member into said cylinder space; said second valve member having a first'fluid .pressurec-actuatabler surface subject.to the pressure of fluid internally of said-tubular means to urge sai'dsecondvalve member into engagement with said seat, said second valve member having a second resultant fluid pressure actuatable surface subject to the pressure of fluid externally of said tubular means to urge said second valve member out of engagement from said seat; the projected area of said first surface normal to the axis of said second valve member being substantially greater than the projected area of said second surface normal to the axis of said second valve member; means releasably securing said first valve member to said tubular means; back pressure valve means in said tubular means; and means interconnecting one of said valve members and back pressure valve means to prevent closing of said back pressure valve means, said interconnecting means being rendered ineffective to prevent closing of said back pressure valve means upon release of said securing means and shifting of said first valve member within said tubular means.

25. In well apparatus: a cylindrical tubular member having a fluid passage therein and having means thereon for securing said member in a conduit string to be lowered in a well bore; said passage having a central outlet coaxial of said member adapted to communicate with the conduit string above said member and an inlet below said outlet; means providing a valve seat in said passage above said inlet and between said inlet and outlet and coaxial of said tubular member; a valve member coaxial of said tubular member movable downwardly into engagement with said seat and upwardly out of engagement therefrom; said valve member having a resultant upwardly facing fluid pressure actuatable surface subject to the pressure of fluid in the outlet and conduit string thereabove to urge said valve member downwardly into engagement with said seat; said valve member having a resultant downwardly facing fluid pressure actuatable surface subject to the pressure of fluid in said inlet to urge said valve member upwardly out of engagement from said seat; the pressure actuatable area of said upwardly facing surface being substantially greater than the pressure actuatable area of said downwardly facing surface when said valve member is disengaged from said seat.v

26. In well apparatus: a cylindrical tubular member having a fluid passage therein and having means thereon for securing said member in a conduit string to be lowered in a well bore; said passage having a central outlet coaxial of said member adapted to communicate with the conduit string above said member and an inlet below said outlet; means providing a valve seat in said passage above said inlet and between said inlet and outlet and coaxial of said tubular member; a valve member coaxial of said tubular member movable downwardly into engagement with said seat and upwardly out of engagement therefrom; said tubular member having a cylinder coaxial therewith and along which said valve member is slidable; said valve member and cylinder defining a cylinder space therebetween; means providing a slidable seal between said valve member and cylinder to prevent passage of well fluid on both sides of said valve member into said cylinder space; said valve member having a resultant upwardly facing fluid pressure actuatable surface subject to the pressure of fluid in the outlet and conduit string thereabove to urge said valve member downwardly into engagement with said seat; said valve member having a resultant downwardly facing fluid pressure actuatable sur- References Cited in the fileof this patent UNITED STATES PATENTS 1,153,373 Deemer Sept. 14, 1915 16 Sowden Feb. 20, 1917 Bryan Nov. 7, 1939 Burt June 18, 1940 Brown Aug. 20, 1940 Johnson Aug. 10, 1943 Burt et al Sept. 28, 1943 Baker July 7, 1953