US2854079A - Well cementing apparatus - Google Patents

Description

Sept. so, 1958 Original Filed- April 16,1949

s. B. SCHNITTER mam. CEMENTING APPARATUS 3 Sheds-Sheet 1 ig-0Z2 Sylvester B. Sc hhitter IN V EN TOR.

ATTORNEY Sept. 30, 1958 s. B. SCHNITTER WELL CEMENTI NG APPARATUS Original Filed April 16, 1949 3 Sheets-Sheet 2 will" 5 .llll 0111/ I I II Sy/ve star 5. Cl7f7ifff INVENTOR.

ATTORNEY Sept. 30, 1958 s. B. SCHNITTER WELL CEMENTING APPARATUS Originai Filed April 16, 1949 3 Sheets-Sheet 3 y/vesfr B. Schm'tter IN VENT 0R.

' ATTORNEY United States Patent M WELL CEMENTIN G APPARATUS Sylvester B. Schnitter, Dallas, Tex., assignor to L. L. Rector, Tarrant County, Tex.

Original application April 16, 1949, Serial No. 88,020, now Patent No. 2,664,163, dated December 29, 1953. Divided and this application July 27, 1953, Serial No. 370,577

2 Claims. (Cl. 16670) This application concerns improvements in apparatus for cementing casing to strata in a well bore; and particularly concerns improvements in the segregation of fluids in a well casing for the purpose of maintaining the homogeneity and uncontaminated state of such fluids used during a well cementing operation.

This application is a division of my co-pending application, Serial No. 88,020, filed on the 16th day of April, A. D. 1949, Patent No. 2,664,163, issued December 29, 1953.

Among the objects to be accomplished by my invention, may be found the following:

(1) The provision of a special cementing head especially adapted for use with elastic collapsible fluid spacer plugs such as are disclosed herein, which head isadapted to be attached to the upper end of a string of casing, and has an inner diameter at the place of joinder between the head and the casing of lesser diameter than the interior diameter of either the head or the casing, whereby when the plug is forced by pressure through the smaller opening it is deformed and elongated, so that upon passing the constricted opening it will elastically relax against the inner walls of the casing and provide a uniform and tight seal. Also such constriction causes the expulsion of the stopper member closing the interior hollow bore of the plug and allows for the expulsion of fluid from the said hollow bore so that when the plug passes the constriction fluid will be sucked back into the hollow portion by force of vacuum.

(2) The provision of such a special head to be used with the aforesaid plug, said head having a receptable thereon adapted to hold and release a trip ball into the head, and into the casing string, so that said ball may be pumped to a seat in a frangible float assembly and thus expel the float assembly by pressure.

(3) The provision of such a specialized cementing head with releaseable means therein for holding a fluid segregating plug until the desired time for releasing the plug into the well cementing circuit for the purpose of segregation of fluids.

(4) The provision in such a specialized cementing head of a cap thereon adapted to releasably hold a back pressure check valve, used in my method of cementing, until the desired time for releasing the check valve, and the plug carrying same, into the cementing circuit for the purpose of spacing fiuid therein, and to automatically stop the movement of fluid in the well circuit at the desired time and place.

(5) The provision in such a specialized head of a combination of means for releasably holding therein a trip ball, a primary spacer plug, and a top spacer plug, with back pressure check valve attached thereto, so that the said members may be released into the well circuit in sequenced order without removing the cementing head from the string of pipe.

(6) The provision of flow manifold communications with such a specialized cementing head whereby selected fluids may be admitted into the head, and therethrough 2,854,079 Patented Sept. 30, 1958 Other and further objects of my invention will become,

apparent by referring to the drawings and reading the detailed specification which follows hereinafter.

Preferred embodiments of my invention are shown in the drawings attached hereto, in which drawings:

Fig. I is a side elevational view of a string of well casing with my specialized head attached to the upper end thereof, and with a float shoe attached to the lower end thereof, and having a stall collar intermediate the upper and lower ends thereof.

Fig. II is a side elevational view, partially sectionalized, of the preferred form of my new type fluid spacer plug.

Fig. III is a side elevational 'view, partially sectionalized, of a modified form of my fluid spacer plug.

Fig. IV is a side elevational view, partially sectionalized, of my specialized cementing head used with my new type plug, and showing the trip ball, primary plug, top plug and back pressure check valve releasably positioned therein, ready to start a cementing operation.

Fig. V is a cross sectional view taken along the line V-V of Fig. IV.

Fig. VI is a cross sectional View taken along the line VIVI of Fig. IV.

Fig. VII is a fragmentary, cross sectional elevation of the upper part of the back flow check valve, cap for the cementing head, and the handle for holding, and releasing the back flow check valve in the head.

Fig. VIII is a fragmentary cross sectional elevation.

showing the channel on the outer side of the cementing head with the communications between same and the cementing head, provided to equalize the pressure in the cementing head above and below the top plug.

Fig. IX is a fragmentary, side elevational view, partially sectionalized, of a string of well casing with my float shoe attached to the lower end thereof and the stall collar spaced above same.

Fig. X is a fragmentary side elevational view, partially sectionalized, of a string of well pipe showing the frangible float assembly having been expelled from the casing and the primary plug and the top plug, with the back flow check valve attached thereto, spacing a quantity of cementing slurry in the well pipe.

Fig. XI is a fragmentary, side elevational view, partially sectionalized, of a string of easing showing the frangible float assembly having been expelled by the trip ball into the bore of the well, and the primary plug having been expelled into the bore of the well, and the back flow check valve having been guided and locked in place in the stall collar, and the cementing job having been completed by expelling the cement to the space between the well pipe and the outer walls of the well bore.

Fig. XII is a cross sectional plan view, taken on the line XII-Xll of Fig. XI, of the back pressure check valve showing the construction and mounting of the spring-urged split ring which expands to engage the lower edge of the stall collar 51.

In the drawings, numeral references are used to designate the various parts thereof, and like numerals are used to designate like parts, and in which numeral 1 indicates a string of conventional well casing used in a well. Attached to the lower end of the well casing is a float shoe 2 of a specialized type used in my method of cementing oil Wells as disclosed in my co-pending application for United States Letters Patent, Serial No.

757,452, filed on June 27, 1947, Patent No. 2,662,602, f

coupling in which the stall collar is screwed. At the upper end of the well pipe is positioned the cementing 3 head 5, which is; secured: to. the well casing by means of the collar 6.

The upper end of the cementing head 5 is closed by a cap 7 which is threaded intothe top of the cementing head. A handle 8; is. provided with, a shaft passing through the cap 7 for the purpose of releasing the back pressure check valvev into. the well flow circuit, in the manner which will be hereinafter describedin. detail, The shaft for the handle 8. passes through the housing 9: and through the cap 7; The housing 9 is secured to the top of, the cap 7 and has two oppositely disposed extensionsv thereof, which. are for the purpose of limiting the. rotation of the handle 8, for the purposes andin the manner which will be hereinafter described.

Positioned onv the outer peripheryof the cementing head 5 is a channel member 10, which. is provided with communication atthe upper. and lowerends thereof with the interior of the cementing head; 5 so that pressure may be equalized above and below the top cementing plug when positioned in the head 5'. This will also be described-in more detail. later.

The handle 11 may be seen on the outer side of the cementing head 51 in Fig. I, which handle is provided for the purpose of releasing the primary plug into the well flow circuit atthe proper time.

A trip ball receptacle 12 is provided on the outer periphery of the cementing head and has ahandle 13 passing therein for the purpose of releasing the trip ball into the cementing circuit. The detailed function and operation of this mechanism will be described hereinafter.

A flow line 14. communicates with the cement mixing unit (not shown): and causes communication between such unit and the cementing head through the valved inlets to such cementing head; and the flow line 15 communicates with the well pump and permits the pumping of well mud from surface storage facilities into the cementing head through the selected valved conduit leading into the head. These valved conduits 16, 17 and 18 communicate with each other through the connecting pipes 19 and 20. A selected flow of fluid may be admitted into the casing by mere manipulation of valves on these conduits 16, 17 and 18. The flow lines 14 and 15 are connected to the pipes 19 and 20 and communicate with the valved conduit 16, 17 and 18 through the cross connections 21.

Figs. IV, V, VI, VII, and VIII show the detailed construction of the specialized cementing head used with my new plug and intended for use with my full bore cementing method as disclosed in my co-pending application, referred to above. In these figures passage 22 connects with the valved inlet 18 by being threaded thereto through a suitable collar, and well fluid is admitted therethrough into the cementing head and pumped through the well flow circuit before the cement is admitted into the well flow circuit, for the purpose of determining whether or not there is a. free flow of fluids through the well flow circuit. This conduit may also be connected to facilities for admitting a dispersing fluid for the purpose of conditioning the well mud in the well flow circuit, before admitting the cementing slurry thereto.

The trip ball 23 is shown positioned in the ball receptacle 12 ready for releasing into the well flow circuit after or during the aforesaid circulation has been completed', for the purpose of pumping the same down to position in the frangible float assembly 95, to expel same from the well pipe to permit a free flow of fluids through the well circuit during the cementing operation. This trip ball is of conventional type and is made of a dr-illable material.

The trip ball receptacle 12 constitutes a cylindrical housing, which is welded to the outer periphery of the cementing head 5 and the outer end thereof is interiorly threaded to receive the threaded plug 24.

The plug 24 has a central bore or opening 25 passing' therethrough, which bore has a portion at the outer 4 end thereof which is interiorly threaded to receive the p us ordinar ly closes. he Passa e or. bo e. 25, but it may be removed for the purpose of mounting therein a pressure gauge, which is used to record the varying pressures during a well cementing operation.

The cylindrical housing 27 is. welded to the outer periphery of the ball receptacle 12 and is interiorly threaded at its outer end to receive the threaded stufiing box 28.

The stufling box 28 has a packing element 29 at the inner end thereof, around the shaft for the handle 13, which packing element is recessed from the interior wall of the ball receptacle 12- so that the head 32, on the inner end of the handle 13, will enter said recess and will not protrude into the interior of the ball receptacle 12, when the handle 13 is pulled outward. The ball 23 is thus allowed to freely fall into the cementing head 5 when it is released by withdrawing the handle 13.

Th pac ingelemen pr d to p v i and other foreign matterfgom escaping fromv the ball receptacle 12 into the bore. 30;.

T he, bore 30; passes centrally through the stuffing box 28 and is provided to admit the shaft of the handle 13 to pass through the stuffing; box 28 to the interior of the ball receptacle. Another packing element 31 is provided around the shaft for the handle 13 which packing element is spaced from, the packing element 29.

The head 32, on the inner end of the handle 13', is of cylindrical shape and, has a rounded outer surface which engages the ball 23 and, holdsv it in the receptacle 12; until the handle 13 is; pulled, outward to allow the; ball to fall into the cementinghead in the manner which will be hereinafter described. Thehead 32 is larger than the bore passing through the packing 29, and the bore 30, passing through the stuffing box 28 to prevent the-ham dle 1-3 from being pulled entirely from the ball recep tacle 12.

The handle 13 islocked' against withdrawal from. ball receptacle 12, after being pushed inward to hold the ball in the receptacle 12, by a J; slot arrangement which is exactly the same in construction as the J slot arrange-. ment used in connection with the handle 11, which will be described in detail hereinafter.

The opening 33 is provided in the outer shell of. the cementing head. 5, which opening communicates with,

and is connected to, the valved conduit 17, and is ordi-v narily used to admit the cementing slurry into the cementing head and therethrongh into the casing by opening the valved conduit 17, after the primary plug 34' has beenreleased in the manner hereinafter described.

The primary plug is hungin the cementing head by means of an eye 35, which eye is provided with female threads in the end of the shank thereof which receive the male threads on the connector member 74 of the plug 34.

The shaft 36 of the handle 11 passes through the eye 35 and the inner; tapered, enlarged end 37 thereof is inserted through the hole 38 in the side of the cementing head 5 and is-received in the cylindrical housing 39. The housing 39 is welded to the outer side of the cementing head 5 over the hole 38, thus receiving and supporting the head 37 on the shaft 36.

The end 37 of the shaft 36 is enlarged and tapered outwardly so that when shaft 36 is withdrawn in the manner hereinafter described the head 37 will easily pass through the eye 35 and allow the plug 34 to be released into the well flow circuit but the head 37 is; too large to permit the complete withdrawal of the shaft 36 from the head 5. The shaft 36 is free to rotate in the hole 33, so that the handle 11 may be rotated, in the manner which will hereinafter be described, to allow the withdrawal of the shaft 36 through the eye 35.

Cylindrical housing 40 is welded to the outer side of the cementing head 5 and forms a casing for the stuffing box 41. Housing 40 is interiorly threaded on its outerend to threadedly receive the stufiing box 41. A central bore 42 passes through the stufling box 41 andreceives the shaft 36 on the handle it. The packing 43, which is recessed from the inner wall of the cementing head 5 to admit the head 37 in such recess, is provided around the shaft 36 to prevent debris from leaving the cementing head through the bore 42. Another packing element 44 is provided around the shaft 36 to further prevent debris from leaving the cementing head through the bore 42.

A horizontal slot 45 is provided in the stufiing box 40, which slot is formed by extending the bore 42. outward to the outer periphery of the stufling box 41.

Another slot 46 is cut at right angle to the slot 45 and connects therewith a slight distance inward from the extreme end of the stuffing box 41. This forms what is commonly known as a J slot.

When it is desired to pull the shaft 36 of the handle 11 outward, in order to release the plug 34 into the well flow circuit, the handle 11, which is shown in Fig. IV as being pushed inward and resting in slot 46, is turned counter-clockwise as is denoted by dotted lines in Fig. IV. The handle 11 will thus be made to register with the horizontal slot 45. Then the handle 11 may be pulled backward, and the shaft 36 thereon will slide outward through the bore 42. Thereby the end 37, of the shaft 3 6, is pulled outward through the eye 35, and the plug 34 is thus released into the head 5 and permitted to enter the well casing.

When hanging the plug 34 in the cementing head in the position shown in Fig. IV, the shaft 36 is inserted through the eye 35 and pushed inward, and the head 37 is inserted through the hole 38 and into the receptacle 39. The handle 11 is turned clockwise when it comes in register with the slot 46, thus locking it in place and preventing the outward movement thereof until the handle 11 is again turned counter-clockwise to cause it to match with the slot 45.

' This J slot arrangement, described in detail above, for locking the handle 11 against withdrawal is exactly the same in construction as the J slot arrangement provided for locking the handle 13 against withdrawal.

The passage 47 which is defined by a hollow cylindrical member welded to the exterior of the cementing head 5, leads into, and communicates with, the interior of the cementing head 5 and is connected with, and communicates with, valved conduit 16, through which well mud may be flowed into head 5 and therethrough into the casing, after releasing the top plug 48 with the back pressure check valve 49 attached thereto.

Back pressure check valve 49 is provided with a central bore in the bottom thereof with female threads therein (not shown) which are adapted to receive the male threaded connector member 74 provided on upper end of the plug 48. The plug 48 is connected with the back pressure check valve 49 so that they Will travel together through the casing string, and the back pressure check valve .49 will be conveyed by plug 48 to a seated position in the stall collar 3.

Back pressure checkvalve 49 is provided with a spring loaded split ring 50 which is adapted to be contracted into a recess on the body of the back pressure check valve 49 when force is applied to the outer periphery of the said ring. Such a force is applied to said ring when the lower end of valve 49 is forced through the inner tube 51 in the stall collar 3. When pressure is released from the said ring, upon passing below the inner tube 51, it will relax by spring action behind a shoulder on the lower side of the inner tube 51.

The split ring 50 is made in separate halves 50a and 50b which are movably disposed in annular recesses 103 and 104 formed in the body of back pressure check valve 49 and which are normally urged outwardly by the springs. 1 05 and 106. The halves 50a and 50b are limited in their outward movement by plates 107 and 6 108 which are attached to the by screws 109 and 110. The plates 107 and 108 have flanges 111 thereon which interlock with complementary flanges 112 on the segments a and 50b.

The back pressure check valve is also provided with resilient packing rings 52, extending around the body thereof, which seal against the inner sides of the inner tube 51 when the back pressure check valve is locked in position in the stall collar 3.

A taper 53 is provided on the upper end of the back pressure check valve 49 which mates with the inner taper or'valve seat 54 in the upper end of the inner tube 51, and stops the progress of the back pressure check valve in the casing when the said taper 53 is seated in the valve seat 54. Thus the pumps, which are circulating the fluid in the well circuit, are stalled, and the flow of fluids upwardly and downwardly in the casing string and behind the casing, is immediately stopped, since the back pressure check valve 53 may not move downwardly, and it may not move upwardly by virtue of the split ring 50 being locked behind the shoulder on the lower side of the inner tube 51.

The vvertical slots 64 are cut on the opposite sides of the top of the valve member 49; and a horizontal slot 55 is cut at right angles to and communicates with each slot 64. The slots 55 are cut in opposite directions.

The shaft 56, which has an upper enlarged portion 56a to fit the housing 9, is attached to the handle 8 and rotatively extends through the housing 9 and through the cap 7, and is provided with a tapered mating member 57 on the lower end thereof. Handle 8 is attached to the shaft 56 by passing the handle 8 through a passage in the shaft and afiixing it thereto, as by welding.

The top of the valve body 49 is provided centrally with a tapered bore 58, which is adapted to match, and.

rotatably receive the mating member 57. The mating member 57 has horizontally disposed pins 59 extending from the outer sides thereof; and the cap 7 has a pair of vertically disposed pins 60 disposed on the under side thereof and oppositely disposed to each other. Each of the pins 60 is adapted to fit into a slot 61 in the top of the back pressure check valve 49.

When mounting the spacer plugs and back pressure check valve in the cementing head 5 the back pressure check valve 49, with top plug 48 attached thereto, is attached in locked position to the cap 7 before the cap 7 is placed in the top of the head. This is done by inserting the member 57 into the female mating member 58 in position so that the pins 60 on the bottom of the cap 7 V will match with and be inserted in the slots 61 in the top of the back pressure check valve; and the horizontally disposed pins 59, on the mating member 57, are made to match with and are inserted in the vertical slots 64. The handle 8 is then rotated counter-clockwise so that the pins 59 will enter the horizontally disposed slots 55.

A hole 62 is provided through the upper enlarged portion of shaft 56, and a hole (not shown) is provided through the housing 9, which hole is adapted to match vwith the hole 62 when the handle 8 is rotated counterclockwise. When the holes are thus matched, the pin 63 may be inserted through the said holes, thus locking the shaft 56 and preventing it from rotation until the pin 63 is withdrawn to permit clockwise rotation. Thus the top cementing plug, attached to the back pressure check valve is.locked in a stationary position in the cementing head. The pins 60, in aligned position in the slots 61,

prevent the rotation of the back pressure check valve 49 1 about its verticalaxis. When the pin 63 is withdrawn and the handle 8 is rotated in a clockwise direction, the

body of check valve 49.

The housing 9, is provided with extensions 66 on the,

upper endthereof which are oppositely disposedandlirnit therotation of the handle 8. The maximumrotation of handle 8' in counter-clockwise direction supplies alignment to hole 62 through shaft 56 with the hole (not shown) in housing 9., and the maximum rotation. of handle 8 in clockwise direction supplies alignment of pins, 59, and the vertical slots 64' of the back pressure check valve 49.

The cap, 7 has a skirt or extension 67' thereon which is provided with exterior threads on the lower side thereof and, is secured in the cementing head by threading same into correspondingly matching female threads in the top of the cementing head 5. The skirt 67 is provided with a resilient packing 68 around the lower side thereof.

As, described above, the back pressure check valve is locked in position on. the under side of the cap 7 before the cap, is screwed into the top of the cementing head. Then, when it is desired to release the back pressure check valve, with the plug 48 attached thereto, into the well cementing circuit, at the proper interval, it is only necessary to withdraw the pin 63, turn the handle 8 in a clockwise direction, disengage the pin 59 from the slot 55', and allow the back pressure'check valve and the plug attached thereto. to freely fall, and be pressured into, the well'fiow circuit.

The housing or channel member 10 is welded to the outer, side of the cementing head 5 and provides a chamber therein. A hole 99 is provided through the cementing head near the upper end of said channel; and a hole 100 is provided through the outer wall of the cementing head Snear, the lower end of said channel. Thus communication is provided between the upper and lower ends of the top plug 48 through channel 10, when saidplug is positioned in the cementing head, for the purpose of equalizing whatever force is present inside the cementinghead above and below the top plug at all times, and allows the plug 48' to be held in equilibrium before being released into the well flow circuit. Such equalization of pressure above and below the plug 48 may be advantageous where the diameter or plug 48 is such that the outer surface thereof will be in sealing engagement with the wall of the head 5 when the plug is subjected to pressure.

The preferred form of my. new cementing plug, which maybe either the primary plug 34 or the top plug 48, is shown in detail in Fig. II.

The cementing plugs are made of elastic material such as natural or synthetic rubber compound.

This plug has a sealing face 69 thereon, which sealing face has a long continuing contact with the bore walls of the casing, by frictional engagement therewith, uponits movement through the casing bore. An outwardly diverging lip 70 is provided on the upper outer side of the plug and a lower outwardly diverging lip 71 is provided on the lower outer side of the plug. These lips 70 and71 are not in the same plane with the sealing face 69, but are brought into the same plane therewith when pressure is applied to the plug and it is contracted and elongated in frictional engagement with the borewalls of the casing. After the plug is so contracted and elongated by pressure, the outer periphery of the plug, including the outer side of the sealing face 69 and the outer sides of'the lips 70 and 71, form one continuous straight linein frictional engagement with the bore of the casing. These lips, 70 and 71, are provided to assure tight fricti onal engagement by the outer face of the plugwith the ner. bo e. ino

The plug has a hollow bore 72 therein which is open the opening tobore 72 by frictional engagement with the interior walls thereof.

The threaded ioinder member 74, which is made of metal ofa drillable nature, such as aluminum or the like, has a lower end portion 75 which is hour glass shaped, that is, the middle portion is less in diameter than the, upper and lower portion thereof, and is tapered from the center outward toward both ends, and the outer periphery thereof has steps or waves therein. This lower end portion is molded into the upper cylindrical extension. '76 of the rubber plug at the time the plug is made and the shape thereof; with the upper and lower ends of larger diameter than the middle thereof, and with the steps thereon, prevent the connector member 7 4 from being pulledjfrom, the plug.

A baffle 77 is. provided which extends continuously around the plug and the upper face thereof connects the inner surface 78.015 the sealing face 69 and the upper cylindricaljportion 76.

A series ofjspacedf upper webs 79 are provided around: the upper end of the plug. These upper webs connect the baffle 77, cylindrical extension 76 and the inner face 78. It will be noted that the upper ends of thewelitsv 79 do not come to the outer end of the cylindrical member 76 and the lower ends thereof do not extend to the top; of the inner side 78 of the outer face 69. There are. a plurality of these webs79, disposed at spaced intervals. around the top of the plug, and these webs, together with the cylindrical member 76, the upper side of. the; bafiie 77 and the inner face 78 of the sealing face; 69, definea series of, spaced interstices 80 around the HPPQF end of the plug.

The outer sides of the hollow interior 72 of the plug forms a lower cylindrical member 83. The, inner; side.

of the lower extension 82 of the sealing face 69. These webs 84, the baffle 77, the inner surface 82 of the sealing face and the outer surface of the lower cylindrical, member 83, define a, series of spaced interstices 85 around the lower endof the plug.

This. fluid, spacer plug has the attribute and capability of beingeasily deformed when pressure is exertedthereagainst. At the same time, it has the, attributes of; a solid when it is submerged in a non-compressible fluid, or nearly sonon-compressible fluid, and pressure is exerted thereagainst. This is so because the hollow in: terior of the plug is filled with fluid and the interstices- 80 and 85 are filled with fluid; and when the plug is, initially deformed and elongated by being forced through.

the restricted opening 101 the stopper 73 is expelled by force of suction. The plug ismaintained in a. rigid.

state at all times while under pressure and moving in the well flow circuit during a cementing operation.

Frictional engagement with the, borewalls of the cas; ing is provided by the outer sealing face of the plug, and by the sealing lips thereon, when the plug is deformed and elongated by pressured movement through a boreof smaller diameter than the plug. Thi s plug, is, made of larger diameter than the bore of the casing in which it is-usedand is thus elongated into frictionalene gagement with the bore walls of the casing as. it. moves in the bore.

Fluid isprevented from passing around the plug and none passes through it.- The hollow bore and the in- 9 I terstices of the' plug are filled with fluid while the plug is moving in a casing bore and separate and define two different columns of fluid therein.

The elongated, unbroken and continuous outer face of the plug provides stability and keeps it from wobbling while moving through the casing bore. This capability is not found in any plug presently used in cementing operations.

The interstices of the upper and lower ends of the plug allow the plug to be more easily deformed and elongated for passage through a casing bore of smaller diameter than the plug, or through a restricted area in the casing bore, while at the same time such interstices lend rigidity to the plug by confining within the plug the forces encountered by it.

A modified form of my cementing plug is shown in Fig. III wherein the outer sealing face 69. and the upper and lower lips 70 and 71 are the same in construction as in the preferred form hereinbefore described; and the upper cylindrical member 76 and connector member 74, with extension 75 thereon, and the hollow interior- 72 are the same in construction as that described above in reference to the preferred form of my plug.

In this modified form a series of upper interstices 86 are formed about the top of the plug.

A plurality of upper peripheral skirts 87 extend outwardly from the baffle 88. A series of spaced upper webs 89 are positioned diagonally across the peripheral skirts 87 and connect them together. An upper interstice 86 is defined by the innermost peripheral skirt 87, two webs 89, baffle 88, and the cylindrical member 76, and there are a series of these interstices around the periphery of the upper side of the plug adjacent to-the cylindrical member 76. There are also a series of these interstices 86, extending around the upper end of the plug, each of which interstices is defined by oppositely disposed walls of two peripheral skirts, a web member 89 on each side thereof and the baflie 88 forming the bottom thereof. The outer series of spaced interstices 86 around the upper end of the plug, are defined by a peripheral skirt 87, the inner side of the sealing face 69, two web members 89, and the baflie 88.

A plurality of lower cylindrical skirts 91 are positioned around the lower end of the plug which, with the web connecting members 92 and the bafile 88, form a plurality of lower interstices 90 around the lower end of the plug. These interstices are formed in the same manner as was described above in reference to the upper interstices.

This modified form of plug has the same function and advantages as the preferred form described above, in that it has a hollow bore, an elongated sealing face, and spaced interstices around the upper and lower ends thereof, with an expellable stopper member 73 to close the bore 72 therein. It is easily deformed and reformed and has the attributes of a solid when submerged under pressure.

The operation and function of my new type of fluid segregating plug with the special head designed therefor may be stated as follows:

Ordinarily the cementing head with the trip ball, primary plug and secondary plug with the back flow check valve attached thereto, is assembled on the derrick floor before the head is attached to the string of casing which has already been run into the hole.

Of course, before running the string of easing into the hole, prior to the cementing operation, the frangible float assembly 95 has been placed in the float shoe 2 and is held therein by the shear screws 96. This float assembly allows for the floating of the string of casing progressively into the hole.

The stall collar 3 is also placed at the desired point in the string of casing.

The ball 23 may be placed within the receptacle 12 by removing the cap 24 and placing the ball in the recep- 1Q tacle against the rounded it may be placed in the receptacle by pushing it upward through the bottom of the cementing head before it is positioned on the casing and engaging it by the head 32 to hold it therein.

A primary plug 34 is hung in the cementing head 5 by threading the shaft 36 through eye 35 and inserting the head 37 in the receptacle 39 in the manner hereinbefore described; and the plug 48 with the back flow check valve 49 attached thereto is engaged to the cap 7 and the cap screwed into the top of the cementing head in the manner hereinbefore described.

Before positioning the primary and top plugs in the cementing head, the bores 72 therein are filled with fluid and stoppers 73 are inserted to close the bores to retain the fluid therein.

The cementing head is then placed on the upper end of the string of casing and held thereto by the collar 6.

It will be noted that the interior portion of the cementing head is smaller in diameter than the interior bore of the casing string 1 at the place where the cementing head 5 is joined onto the casing.

After the head 5 has been thus positioned on the casing, with the accessories therein, the valved inlet 18 is opened to allow the well mud to be pumped through the casing and up behind the casing to return to the surface storage facilities. After the well has been thus circulated satisfactorily to assure that there is an open well flow circuit, the trip ball 23 is released into the casing by disengaging the handle 13 and pulling it outward and thus allowing the trip ball to fall by gravity into the casing bore. The trip ball is then pumped downward until it comes to rest in the valve seat 102 in the float assembly 95. Sufficient pressure is then applied thereto by the surface pumps to shear the screws 96 and eject the float assembly from the casing. A substantially free flowing casing bore is then provided for the pumping of fluids into the well flow circuit.

Further circulation is usually carried on through the.

At the desired time the plug 34 is disengaged in the v head 5 by turning the handle 11 counterclockwise and pulling it outward to release the'eye 35 from the shaft 36 in the manner hereinbefore described.

After plug 34 has been thus released, the valved inlet 18, through which the well fluid has been pumped, is closed and another valved inlet 17 is opened to allow cementing slurry to be admitted into the cementing head and therethrough into the casing behindthe primary plug 34.

The primary plug 34, being larger in outside diameter than the restricted opening 101, will be deformed and elongated in its pressured passage through such restricted opening, and in such process the stopper 73 is ejected from the lower end of the plug and the fluid in the interior 72 thereof is partially expelled. The plug, while passing through the restricted opening 101 is made smaller in diameter than the interior diameter of the casing, and upon entering the casing will relax to the contours of the interior of the casing and the outer walls and lips of said plug will form tight frictional engagement with the inner walls of the casing.

Since the plug forms a tight frictional engagement with the inner walls of the casing and since it has the attributes of a solid, no fluid can by-pass it or pass through it, and thus the cementing slurry admitted behind it is perfectly segregated from the mud column ahead of it.

After the cementing slurry has been admitted into the casing, the plug 48, with the back flow check valve 49 attached thereto is released into the cementing head in the manner hereinbefore described.

The plug 48 is forced through the constricted opening 101 and reacts exactly the same way that the plug head 32 on the handle 13; or

34 reacted when forced therethrough, and is admitted into the casing carrying therewith the back pressure check valve 49.

The plug 48 acts both as a spacer plug to space the column of mud which follows it from the column of cementing slurry which precedes it, and as a conveyor to carry the back flow check valve 49 to the place of seating in the stall collar.

After the plug 48 and back flow check valve 49' have been released from their locked position in the cementing head the cementing slurry conduit 17 is closed and another of the valved conduits, entering the head, is opened to allow Well mud' to enter the head and therethroughto enter the casing.

The slurry, which is indicated by the numeral 97; and the well mud, indicated by 98, are then pumped downward in the casing and upward outside of the casing until the backfiow check valve 49 comes to rest in the stall collar 3. The pumps are then stalled and the operator then knows that the cementing job has been completed. He then releases the pressure from the surface pumps and the backflow check valve 49 is prevented from moving upward in the casing by virtue of'the split ring 50 being engaged under the shoulder on the lower side of; the inner tube 51, and is prevented from moving downward because the upper side thereof is seated in the taper 54 provided on the upper end of the inner'tube 51.

During this procedure the plug 34 has been ejected into the bottom of the well bore 94.

The plug 34, the ball 23, the float assembly 95 and the stopper, 73 are, all made of material which may be penetrated and broken up by the drill bit should such ensuing procedure be required for bore hole. deepening.

Any one of my plugs may be made and operated; with perfectly straight side walls, having no lips, flanges, corrugations or other breaks.

It is to be understood that other and further modifications and forms of my invention may be devised and arranged externally of said cementing head and'compris ing a cylindrical housing ofjsufficient diameter to receive a trip ball and a removable cap positioned on the outer end of said housing, the cap having a bore therethrough adapted to receive a pressure gauge; a second housing positioned on said firstmentioned housing, adapted. to receive a stufli'ng box; a stufiing box' positioned in said second mentioned housing, said stuffing box having a central bore therethrough; a rotatable handle arranged through said'bore, said handle having an enlarged inner endithereon positioned.inside said first mentioned housing and adapted to engage and retain a, trip ball in said first mentioned housing untilsaid' handle is withdrawn therefrom; and means to lock said handle against withdrawal from said housing, when inserted therein.

2'. In a well cementing head adapted to be attached to the upper end of a wellcasing, means for releasably holding a back flow check valve with a top cementing plug attached thereto in the upper end of said cementing head, said means comprising, a removable cap member positioned in thetop of said cementing head; a rotatable shaft passing through said cap; a handle attached to the outer endof the shaft; a male mating member on the lower end of said. shaft, said' member being insertedinto a female socket in the top of said back flow check valve; a pair of oppositely disposed J slots positioned in the top of the said back fiow check valve, a pair of oppositely disposed and horizontally aligned pins positioned on said male mating member and adapted toengage with the said J' slots to releasably hold the said male mating member to said back flow check valve; a pair of vertically disposed pins on the lower end'of said cementing head cap, said pins beinginserted into corresponding'sl'ots in the top of said back flow check' valve when the back flow check valve is positioned to said cap, to thus prevent the rotation of the back flow check valve whenthe male mating member is disengaged; from the said J slots by the rotation of said. handle; and means to lock the said handle against rotation.

References Cited in, the file of this patent UNITED STATES PATENTS 1,490,143- Taber Apr. 15, 1924 1,662,311 Hamer Mar. 13,1928 1,721,234 Russel July 16, 1929 1,786,848 Johnson Dec. 30, 1930 2,058,069 Dyer Oct. 20, 1936 2,196,652 Baker Apr. 9, 1940 2,481,422 Haynes et a1. Sept. 6, 1949 2,615,519 Carr Oct. 28, 1952 2,618,345 Tucker Nov. 18; 1952 2,662,602 Schnitter Dec. 15, 1953,

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