US3527299A

US3527299A - Float shoe apparatus

Info

Publication number: US3527299A
Application number: US778409A
Authority: US
Inventors: William R Lewis
Original assignee: Dow Chemical Co
Current assignee: Schlumberger Technology Corp
Priority date: 1968-11-25
Filing date: 1968-11-25
Publication date: 1970-09-08
Anticipated expiration: 1987-09-08

Description

p 8, 1970 w. R. LEWIS 3,527,299

FLOAT SHOE APPARATUS Filed NOV. 25, 1968 flEE:Z

United States Patent 3,527,299 FLOAT SHOE APPARATUS William R. Lewis, Wichita Falls, Tex., assignor, by mesne assignments, to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed Nov. 25, 1968, Ser. No. 778,409 Int. Cl. E21b 23/00 US. Cl. l66-l84 Claims ABSTRACT OF THE DISCLOSURE A float shoe apparatus for cementing well casings which includes an outer tubular member connectable to the lower end of a string of well casing, a nose plug secured to the lower end of the tubular member, an outer sleeve movably mounted on, and concentrically surrounding a medial portion of, the tubular member, an inner tubular member secured in, and opening concentrically through, the nose plug, and a valve internal piston assembly mounted concentrically within the outer tubular member and slidable axially therein. The outer tubular member is axially slotted at a medial portion which underlies an inflatable rubber packing sleeve forming a portion of the outer sleeve, and downward movement of the internal piston in the outer tubular member forces fluid into the packing sleeve to expand it into contact with the walls of a well bore. Piston type pressure relief valves are disposed in the nose plug and vent fluid from the interior of the apparatus when the pressure acting to expand the packing sleeve exceeds a predetermined value.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to well tools, and more particularly, to apparatus connectable to the lower end of a casing string and useful in closing the end of the casing string to impart buoyancy thereto, and for permitting a cementitious material to be pumped between the casing and well bore.

Brief description of the prior art In the procedure of completing oil wells, it is the practice to drill a well bore, then run a casing into the well bore. The hole is then often conditioned by pumping circulating fluid out through the lower end or shoe of the casing. Finally, the casing is cemented in place by positioning cement above the lower end of the casing in the annulus between the casing and the surrounding earth.

To accomplish the casing positioning and cementing operations, a fitting termed a float shoe is usually secured to the lower end of the casing string and functions to close the lower end of the casing during its descent in the well bore, and to selectively direct cementitious material to a location above the lower end of the casing and around the outside thereof when the casing is in position. Float shoes of the type previously employed usually include a check valve which closes to prevent drilling fluid from entering the interior of the casing and thus to maintain the casing in a relatively buoyant state as it is floated into position in the bore. The check valve will open, however, to permit fluids to be pumped through the casing from the surface in order to condition the well if desired. Many float shoes previously in use also 3,527,299 Patented Sept. 8, 1970 include mechanism by which an inflatable packing sleeve forming a part of the float shoe can be expanded with a suitable fluid to form a plug blocking or sealing olf the annulus between the casing and well bore, and that portion of the bore which is below the lower end of the casing. A float shoe of this type is described in Austin U.S. Pat. 2,845,130.

BRIEF DESCRIPTION OF THE PRESENT INVENTION The present invention comprises a tubular member connectable to the lower end of a string of well casing and having an upper end and a lower end; plug means secured to the lower end of the tubular member; and outer sleeve means movably mounted on, and concentrically surrounding a media portion of, the tubular member. A valved internal piston assembly is mounted within the tubular member and is movable axially therein. The tubular member is axially slotted, and the outer sleeve means includes an inflatable resilient packing sleeve which overlies a portion of the slots in the tubular member, and a rigid sleeve portion which is connected through the slots to the valved internal piston assembly.

The plug means is provided with at least one pressure relief valve which places the well bore in communication with an annulus between a portion of the internal piston and the tubular member. As the internal piston moves axially downwardly to reduce the volume of this annulus, the fluid occupying the annulus is forced through the slots in the tubular member against the inflatable packing sleeve to expand it into contact with the Walls of the Well bore. If an excessive pressure is developed on the packing sleeve tending to rupture it, the pressure relief valve in the plug means opens to relieve this pressure by venting the trapped fluid to the well bore. In this manner, the well can be quickly, safely and effectively packed 01? for cementing the casing in position while leaving the bottom of the hole uncased.

An important object of the invention is to provide a float shoe apparatus which can be utilized to float a well casing to a position near the lower end of the well bore, and then cement the casing in position without circulating cement into the bottom of the well.

Another and more specific object of the invention is to provide a float shoe for use in positioning oil well casing, which float shoe is adaptable to wider variations in well bore diameters without rupture or severance of an inflatable resilient packing sleeve forming a portion of the float shoe.

A further object of the invention is to provide a float shoe of the inflatable packing sleeve type in which the packing sleeve can be inflated by means of fluids located in the well bore when the float shoe and associated casing are lowered in the bore.

Yet another object of the invention is to provide a float shoe in which a preselected pressure applied to a. fluid directed down a casing string to which the shoe is attached can be depended upon to actuate the shoe and thereby to expand an inflatable packing sleeve forming part of the shoe.

An additional object of the invention is to provide an improved float shoe which is characterized in having a long and relatively trouble-free operating life.

Additional objects and advantages of the invention will become apparent as the following detailed description of the invention is read in conjunction with the accompanying drawings which illustrate the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of the float shoe of the invention as it appears when being lowered in the Well bore and prior to inflating the resilient packing sleeve. An alternate position of a check Valve employed in the float shoe is shown in dashed lines, as is an auto-fill bridge tube which may optionally be employed in combination with the float shoe.

FIG. 2 is a sectional view similar to FIG. 1, but showing the float shoe in its stationary, packed otf status.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The float shoe apparatus of the invention is depicted in the figures of the drawings as disposed in a well bore designated generally by reference numeral 10. The float shoe includes an elongated tubular member 12 having an internally threaded box portion 14 at the upper end thereof which threadedly engages the lower end of a casing string 15. Secured in the upper end of the elongated tubular member 12 is a back pressure valve assembly 16 having a bore 17 therethrough which is closed by a pivotally mounted valve member 18. The valve member 18 is spring biased to the closed position illustrated in solid lines in FIG. 1. The open position of the valve member 18 is shown in dashed lines.

Threaded into the lower end of the elongated tubular member 12 is a rounded nose plug 20 which has a bore 22 extended concentrically therethrough, and carrying threads 24 for threaded engagement with an internal elongated tubular member 26. The upper end of the internal tubular member 26 is beveled outwardl as indicated by reference numeral 27. The internal tubular member 26 has a plurality of contiguous annular serrations 28 formed in its internal wall intermediate its length. Each serration 28 has an upper surface 28a disposed in a plane passed at a right angle to the axis of the internal tubular member 26, and also has a lateral surface 28b which is inclined at an angle with respect to this axis, and thus each serration is generally V-shaped in crosssectional configuration. The purpose of this configuration of the serrations 28 will be hereinafter described.

Extending axially in the nose plug 20, and spaced radially outwardly from the inner tubular member 26 and circumferentially from each other, are a plurality of spring retainer bores 32. Radially extending pins 34 are secured across the upper ends of the spring retainer bores 32 to function as positive stops for pressure relief valve pistons 36 located in each of the bores. Each of the pressure relief valve pistons carries a suitable sealing ring 38, and is biased upwardly in the bore by an elongated helical spring 40. Communicating with the lower portion of each of the spring retainer bores 32 is a radial pressure relief orifice 42 which extends through the side of the nose plug 20 into communication with the surrounding well bore 10.

Secured by welding or other suitable means to the lower portion of the elongated tubular member 12 is a packing sleeve anchor ring 46. An inflatable, resilient, cylindrical packing sleeve 48, which may be suitably constructed of rubber, has its lower edge bonded to the packing sleeve anchor ring 46 and extends upwardly around the tubular member 12 in concentric relation thereto. It will be noted that in the status of the float shoe illustrated in FIG. 1, the inflatable resilient packing sleeve 48 extends partially over and partially covers a plurality of elongated, axially extending, circumferentially spaced slots 50 formed in the wall of the tubular member 12 intermediate the length thereof. At its upper end, the inflatable resilient packing sleeve 48 is bonded to a rigid outer sleeve 52 which slidingly surrounds an intermediate portion of the tubular member 12 and extends over a portion of the slots 50 therein. The outer sleeve 52 is provided near its upper end with one or more annular grooves which carry sealing rings 56 sealingly engaging the outer surface of the tubular member 12. It will further be noted that the elongated tubular member 12 also carries at least one externally located annular groove and sealing ring 60 at a location below the slots 50, and the sealing rings 60 serve to sealingly engage the rigid outer sleeve 52 during a cementing operation in Which the inflatable resilient packing sleeve 48 is expanded to a packed oft position as depicted in FIG. 2 of the drawings. The use of the apparatus in this respect will be hereinafter explained in greater detail.

Disposed within the elongated tubular member 12 and between the nose plug 20 and the back pressure valve assembly 16 is a valved internal piston assembly designated generally by reference numeral 62. The valved internal piston assembly 62 includes an inner sleeve 64 positioned concentrically and slidingly within the tubular member 12, and an elongated tubular plunger 66 which is threadedly engaged at its upper end with the inner sleeve 64. The tubular plunger 66 in the illustrated embodiment of the invention is upwardly and outwardly flared at its upper end to provide a flange 68 which aids in guiding into the tubular plunger, a spherical valve member dropped down the casing as hereinafter described. The tubular plunger 66 further carries adjacent its upper end, an internal thread 67 which can be used to threadedly engage an optionally employed bridge pipe 70 illustrated in dashed lines. The bridge pipe 70, when utilized in combination with the float shoe apparatus of the invention, bridges across the space between the valved internal piston assembly 62 and the back pressure valve assembly 16 and projects into the bore 17 through the back pressure valve assembly so as to retain the valve member 18 in its open position. This permits the float shoe and the casing string attached thereabove to become filled with mud and well fluid as the float shoe is lowered in the well bore 10. This is an optional or alternative utilization of the float shoe apparatus of the invention which is sometimes desirable when certain other equipment or apparatus is located in the casing uphole from the float shoe. Nothing more will be said in the present application concerning this possible mode of utilizing the float shoe since, in most cases, the method of operation and use of the float shoe will entail closing the valve member 18 when the well casing is being lowered to the bottom of the well bore 10 for purposes of cementing it in position.

At the lower end of the tubular plunger 66, the plunger threadedly engages an internal valve seat 72. Surrounding the lower end portion of the tubular plunger 66 are two seal ring sets 74 and 76, and a locking ring 78 which is disposed between the two sets of seal rings. The locking ring 78 is of triangular cross-sectional configuration and is retained loosely in a V-shaped groove formed in the side of the tubular plunger 66, so that a portion of the locking ring projects radially outwardly from the outer surface of the plunger for a purpose more fully hereinafter described. It should be mentioned that the locking ring 78 is characterized by a resiliency which permits constriction of the ring to a smaller diameter in which it is substantially entirely confined within its associated V-shaped groove.

The outer sleeve 52 and inner sleeve 64 are interconnected for simultaneous movement with respect to the elongated tubular member 12 by a plurality of threaded bolts 80 which are extended through the slots 50 formed in the elongated tubular member 12. A shearing ring 82, which is preferably constructed of rubber, in located in an annular space which is defined by a pair of opposed communicating grooves 84 and 86 formed in the inner sleeve 64, and in the internal wall of the elongated tubular member 12, respectively. The nature of the shearing ring 82 is such that it will be sheared diametrically when the valved internal piston assembly 62 is forced downwardly in the elongated tubular member 12 for the purpose of expanding the inflatable packing sleeve 48 as hereinafter described. Adjacent its upper end the inner sleeve 64 carries a plurality of seal rings 88 which sealingly engage the tubular member 12.

OPERATION In the utilization of the float shoe apparatus of the invention, the float shoe is secured to the lower end of a string of casing 15 by threading the upper end portion 14 of the elongated tubular member 12 on the lower end of the casing string. As the casing string 15 having the float shoe apparatus attached to the lower end thereof is low ered in the well bore 10, the valve member 18 of the back pressure valve assembly 16 is retained in a closed position by the spring biased character of the valve structure, and in addition, by the pressure acting upwardly thereon by well fluids in the well bore 10 which enter the float shoe through the nose plug 20. Thus, these fluids are prevented from passing through the bore 17 in the back pressure valve assembly 16 to enter the casing string, and the string is therefore characterized in having suflicient buoyancy to permit it to float slowly downwardly in the well bore. It should be noted, however, that the check valve characteristic of the back pressure valve assembly 16 will permit well conditioning fluids to be pumped down the casing string 15, through the float shoe, and into the well bore 10 of this is desired.

In many types of well casing operations, it is desirable to extend the casing string to a point fairly low in the Well bore 10, but spaced vertically from the bottom of the well bore. In other words, the bottom portion of the well bore is permitted to remain uncased, and the operation which is carried out entails cementing the casing string in position in the well bore by locating cement between the casing and the wall of the well bore, but above the uncased bottom portion of the well bore. To this end, once the casing string 15 and the float shoe apparatus at the lower end thereof have been lowered in the well bore 10 to the desired location, the float shoe is utilized for packing oif the well bore to prevent cement from by-passing the float shoe and entering the uncased lower end portion of the well bore.

In order to pack oh? the well bore 10 in this manner for cementing purposes, a spherical valve member or ball 92 is dropped down the hollow casing string 15 and is forced through the back pressure valve assembly 16. The spherical valve member 92 then is guided by the flared flange 68 into the tubular plunger 66 of the valved internal piston assembly 62 and ultimately comes to rest upon the valve seat 72. The possibility of fluid being directed downwardly through the casing string and out through the tubular member 26 in the lower end of the float shoe assembly is thus eliminated at this time due to the closure of the opening through the valve seat 72 by the spherical valve member 92. At the time that the valve member 92 is dropped through the casing string to rest upon the valve seat 72, the annular space 94 between the tubular plunger 66 and the elongated tubular member 12, as well as between the latter member and the inner tubular member 26, has been filled with fluid from the well. During low ering of the casing string 15 and float shoe, this well fluid has been free to pass into this annulus through the space between the lower end of the tubular plunger 66 and the upper end of the inner tubular member 26. In other words, the space surrounding the tubular plunger 66 and the internal tubular member 26 will have been filled with mud and well fluid which is forced into this space during the descent of the casing string and attached float shoe.

When the spherical valve member 92 has been positioned on the seat 72 while the apparatus is in all other respects still in the status depicted in FIG. 1, the next step in expanding the inflatable packing sleeve 48 entails the pumping down the casing string 15 of cement which is to be utilized to cement the casing in position within the well bore 10. The cement passes through the back pressure valve assembly 16 by forcing open the valve member 18,

and then necessarily passes downwardly in the bore in the tubular plunger 66. Pressure is thus everted on the entire valved internal piston assembly 62 in a downward direction, since the cement cannot by-pass the valve seat 72 due to the location thereon of the spherical valve member 92. The pressure of the cement acting downwardly on the valved internal piston assembly 62 forces this assembly downwardly within the elongated tubular member 12. As the internal piston assembly 62 moves downwardly, the tubular plunger 66 enters the inner tubular member 26 and sealingly engages the internal wall of this tubular member through the sets of seal rings 74 and 76 carried on the outer periphery of the plunger. The locking ring 78 is able to resiliently yield inwardly slightly during the downward movement of the plunger 66 in the inner tubular member 26 so as to permit the plunger to continue its downward movement until the locking ring is opposite the V-shaped serrations 28 formed in the internal surface of the inner tubular member. At this point, the resiliency of the locking ring 78 snaps it outwardly so that an interlocking engagement between the locking ring 78 and one of the serrations 28 occurs to lock the plunger against vertical axial movement within the inner tubular member 26. The shapes of the locking ring '78 and each serration 28 are such, however, that downward movement of the plunger 66 within the inner tubular member 26 can be continued if desired.

During the downward movement of the internal piston assembly 62, the outer sleeve 5-2 is carried with the piston assembly due to its securement to the inner sleeve 64 by the threaded bolts 80. The downward movement of the outer sleeve 52 exerts a compressive force on the inflatable packing sleeve 48 so that this packing sleeve is buckled outwardly toward the walls of the well bore 10. Simultaneously with this forced outward movement of the inflatable resilient packing sleeve 48, the downward movement of the inner sleeve 64 reduces the total volume of the space existing between the tubular plunger 66 and the inner tubular member 26 on the one hand, and the inflatable packing sleeve and the outer sleeve 52 on the other. Thus, the fluid which occupied the total original volume of the annulus between the valved internal piston assembly 62 and the tubular member 12 is forced outwardly through the slots 50 against the inflatable packing sleeve 48 so that the bulge inside this packing sleeve is filled with fluid which supports the packing sleeve in its inflated condition. Continued downward movement of the valved internal piston assembly 62 along with the outer sleeve 52 eventually brings the lower end of the outer sleeve 52 past the lower end of the axially extending slots 50 in the tubular member 12.

At this time, fluid from the annulus between the internal piston assembly 62 and the tubular member 12 can no longer enter the space between the inflatable packing sleeve 48 and the tubular member 12. By this time, in many instances, the inflatable packing sleeve will have been inflated outwardly until it engages the internal walls of the well bore 10 in the manner depicted in FIG. 2. When the packing sleeve 48 attains this status, the well bore is packed off so that cement which may be positioned in the annulus between the tubular member 12 and the walls of the well bore cannot by-pass the inflatable packing sleeve 48 to enter the lower end portion of the well bore.

Two of the important features of the present invention are the adaptability of the float shoe apparatus to employment in well bores of differing diameters, and the lengthened opearting life without malfunction which characterizes the float shoe apparatus. Both of these advantages are in large part attributable to the pressure relief valve construction which characterizes the apparatus. Thus, for a relatively small diameter well bore 10, the inflatable packing sleeve 48 cannot be expanded a very great distance with respect to the tubular member 12 before it is prevented from further expanding due to contact with the surrounding wall of the well bore. At this time, additional fluid can be forced into the inflatable packing sleeve 48 by the descending internal piston assembly 62 only at the risk of rupturing the packing sleeve or severing its bonded connection with the anchor ring 46 or the outer sleeve 52 so as to lose fluid from the inside of the sleeve and fail to properly pack off the well bore. This danger is alleviated with the present invention, however, by the inclusion in the nose plug 20 of the pressure relief valves constituted by the pistons 36 and the associated helical springs 40. The springs 40 are preselected so that, at the predetermined pressure, the springs will yield sufliciently to permit the pistons 36 to move down in the spring retainer bores 32 to a point where fluid can escape through the pressure relief orifices 42. Thus, when the pressure acting outwardly on the inflatable packing sleeve 48 becomes excessive, and the yield point or rupture point of the packing sleeve is approached, the pressure relief valves constituted by the pistons 36 and springs 40 will be actuated to vent fluid from the annulus between the inner tubular member 26 and the tubular member 12 to the well bore through the side of the nose plug 20.

Once the internal piston assembly 62 is moved downwardly within the tubular member 12 to the point where the threaded bolts 80 have contacted the bottom of the slots 50 to limit further movement of the internal piston assembly and outer sleeve 52, the locking ring 78 will snap into interlocking engagement with one of the serrations 28 formed in ther inner wall of the internal tubular member 26. It will further be noted that at this time, the upper end of the outer sleeve 52 has moved downwardly, along with the inner sleeve -64, to a point where the upper end of each of the slots 50 is uncovered, and the slots therefore place the inside of the tubular member 12 in communication with the well bore. It is therefore possible at this time to pump cement down the casing string 14, through the back pressure valve assembly 1'6 and into the tubular member 12. The cement cannot pass down through the lower end of the float shoe apparatus and out of the nose plug 20, since this flow channel is obstructed or blocked by the spherical valve member 92. The cement will therefore pass outwardly through the upper end of the slots 50 into the annulus surrounding the float shoe apparatus, and will fill this annulus above the inflatable packing sleeve 48. By continued pumping of the cement in this fashion, the casing can be cemented in position without introducing any of the cement to the lower end portion of the well bore.

Upon completion of the cementing of the casing in the manner described, a drill is then extended through the casing into the float shoe apparatus, and the cement which may have set up therein, along with the spherical valve member 82 and the valve seat 72, are drilled out by the drill to permit fluids to be produced from the well.

Although a specific embodiment of the present invention has been herein described in order to provide an example of the manner in which the invention is to be practiced, it will be understood that various changes and innovations can be made in the depicted and described structure without departure from the basic principles of the invention. All changes and modifications of this type there therefore deemed to be within the spirit and scope of the present invention except as the same may be necessarily excluded by the appended claims or reasonable equivalents thereof.

What is claimed is:

1. Float shoe apparatus comprising:

a first tubular member having an upper end adapted for connection to a well casing and having a lower end, said first tubular member further having at least one axially extending slot formed therethrough intermediate its length;

outer sleeve means surrounding said first tubular member and the slots therein and including 8 a rigid outer sleeve slidably surrounding said first tubular member, and an inflatable packing sleeve around said first tubular member and having an upper end secured to said outer sleeve and a lower end connected to said first tubular member below said slots; plug means secured to the lower end of said first tubular member and including at least one pressure relief valve placing the interior of the first tubular member in communication with the exterior thereof when said relief valve is open; and

a valved internal piston assembly above said plug means in said first tubular member and movable axially therein toward said plug means to force a fluid from the interior of said first tubular member through said slots into said inflatable packing sleeve, said valved internal piston assembly being secured through said slots to said rigid outer sleeve for movement therewith.

2. Float shoe apparatus as defined in claim 1 wherein said internal piston assembly comprises:

an inner sleeve slidingly and sealingly engaging the interior of said first tubular member and secured through said slots to said rigid outer sleeve;

a tubular plunger secured to said inner sleeve and movable therewith to a position sealingly engaging said plug means to prevent fluid flow through said plug means to a space between said tubular plunger and said first tubular member.

3. Float shoe apparatus as defined in either claims 1 or 2 wherein said plug means comprises:

a nose plug secured in the lower end of said first tubular member and having said pressure relief valves therein; and

an inner tubular member secured in, and opening through, said nose plug, said inner tubular member being spaced downwardly from said valved internal piston assembly in one position of the piston assembly, and sealingly engaging a portion of the piston assembly in a second position of the piston assembly to form therewith an isolated, continuous fluid passageway through the nose plug and valve piston assembly which communicates the interior of the first tubular member above the piston assembly with the outside of the nose plug.

4. Float shoe apparatus as defined in either of claims 1 or 2 and further characterized as including a back pressure valve assembly positioned in said first tubular member above said valved internal piston assembly for preventing fluid flow upwardly in said first tubular memher.

5. Float shoe apparatus as defined in claim 2 wherein said inner sleeve and outer sleeve each have a lower portion extending over and obstructing an upper portion of said axially extending slots when said internal piston assembly is in a first position in said first tubular member, and each have an upper portion extending over and obstructing only the lower portion of said axially extending slots when said internal piston assembly is moved downwardly to a second position.

6. Float shoe apparatus as defined in claim 5 and further characterized as including rigid connecting means extending through at least one of said slots and interconnecting said inner sleeve and said outer sleeve, said rigid connecting means limiting movement of said internal piston assembly and outer sleeve to movement between said first and second positions.

7. Float shoe apparatus as defined in any one of claims 2, 5 or 6 and further characterized as including valve means for preventing downward flow of fluid through said tubular plunger.

8. Float shoe apparatus as defined in any one of claims 1, 2, 5 or 6 and further characterized as including a resilient shear ring positioned between, and engaging, said internal piston assembly and said rigid outer sleeve for releasably retaining said internal piston assembly spaced upwardly from said plug means in one operative position of said float shoe apparatus.

9. Float shoe apparatus as defined in any one of claims 2, 5 or 6 and further characterized to include a locking ring around said tubular plunger and adapted for snap-in engagement with said plug means when said plunger and inner sleeve are moved to said sealingly engaging position.

10. Floating shoe apparatus as defined in claim 3 wherein each of said pressure relief valves comprises:

a spring retaining bore in said nose plug and extend ing parallel to the bore through said inner tubular member, and having an upper end and a lower end;

a spring in said bore;

bore.

References Cited UNITED STATES PATENTS Lehnhard 166-484 X Bradley 166-184 X Litchfield 166-225 Alexander 166225 Nelson 166-225 15 NILE C. BYERS, 111., Primary Examiner