US2560901A - Cementing plug - Google Patents

Description

July 17, 1951 F. D. SMITH CEMENTING PLUG Filed Aug. le, 1945 R m WM/ sY vr/.t/// JJ d 7 C, 0 J J 2 4 vll). L //.\\\f/ n/u c bf/w 5 l 4 6 l I f .1 f d w J 7 k k KN 2.. 2 111x! II; I. c. l. w --.l 1 n a iii- 1| m N m n A Patented July 17, 1951 UNITED STATES PATENT A' OFFICE 2,56IQ9I1Mtl CEMEN-TING -'PLUGI f FrankD. Smith;` Whittiex, Cafi'fgffassignbr to I nternational Cementers, Inc'.','Long"Beacli, Calif.,` a corporation 'of Delaware` Application Augustl, 1945-,1'Ser-ial No; 6113-354 .Y

('Cll SBLI) 8` Claims.

1 This invention relates to a plug device adaptedtobe pumped down well tubing, casing-andsimilar conduits, and more particularly to a bottom or top-cementing plug capable y of preventing contamination` between la charge of cernentitious Certain types of cementing plugs have a-longi tudinalH-passage which is initially closed lby a member that is subsequently disrupted hydraulically-by the pressure of the fluid-in thewell casing'or tubing above the plug. There are'several limitations and disadvantages to prior devices .of this type. The disruption of theclosingmember may-produce only partial opening of the passage, resultngfn impeded fluid flow through theplug.- Moreover; since only a relatively small area is acted upon by the uid, the effects of minor errors in dimensions of the closure member and variations in its physical characteristics are magnified, producingv its shearing or Aother mode-v of removal from they passage at unit pressuresdiffering considerably from the supposed predeterminedpressure atwhich passage opening is to occur. closure member on which the iluid pressureacts also necessitates removal of such memberfrom the-passage by relativelysmall total hydraulic forcesfif abnormally high unit hydraulic pressures are to be avoided, to which the entire. casing or tubing string containing the plugv would be subjected.` The closure member must, therefore, be held` acrossthe passage by a retaining device-of relatively low strength.

It isv an object of the present invention to provide a` well plug having a passage initially closed by a member which is positively sheared and completely removed from the passage upon application of a predetermined degree of pressure.

The relatively small area of the to the -iluid in the well conduit above the plug.

Another object of the invention is to provide a` well -plug having a passage closed by a member which is removed hydraulically'by iiuid pressure .acting over an area which is substantially greater acting directly upon it.

A further object of the invention is to provide a Well plug` having a passage closed by a member which can be retained in passage closing positionY by, meansV having a greater strength. than .thel corresponding unit pressure required to effect'- removalfof the member from the passage.

Another object of the invention is to provide a Wellcementing plug whose initially'closed central passage can be opened hydraulically at a pre--V determined pressure with 'greater accuracy than. heretofore obtainable..

This invention has other objects that will become apparent from-a consideration of the embodiment shown in the drawings accompanying.

and forming part of the present specification. This formwill now be described in detail to illustrate the general principles of the invention, but itis to be understood that such detailed description is not to be taken in a limited sense, sincey the scope of theinvention is best defined by the claims appended hereto.

Referring to the drawings:

Figure l is a longitudinal section through al plug' device, disclosed as descending through a tubular string contained within a casing position ina well bore; and

Figure 2 is`` a longitudnalsectional View of the plug device at rest within the tubular string and its centralpassage open to the flow of Iiuids.

As disclosed in the drawings, a cementing plug A may be pumped down a conduit, such as a tubing-string B, extending within a well bore to the. desired depth. The tubing string may be used, as an agency for conveying cementitious material from the top ofthe Well bore, and for dis-y charging `such material behind well casing C through-.its side ports D. A casing engaging. packing in the form of a` swab cup E can be 'secured to the lower Aend of the tubing string tov preventY upward passage of the cementitious materialthrough the Acasing-tubing annulus, and to insure its outward flow throughthe ports D.

. The plug includes a tubular body or mandrel I0 telescoped over an inner tubular member I I havthe pressure of the fluid in the conduit acting overvsubstantially its entire cross-sectional area.

'Yet'a further object of the invention is to provid a' well plug vhaving a passage closedinitially by''diaphragm member wh's'ereinoval from th ing a stop or bumper flange I2 secured at its lower end and a circular knife or blade I-3 at its upper end.` A packingsleeve I4 is secured to the body by being clamped between its upper shoulder I5 and a nut I6 threaded on its lower end. The upper end ofthe packing sleeve has an outwardlyV ilaringlip I1 for -slidable sealing engagement4 againstlthewall of thewell conduit B 'throughY which it-ay be Dumped.`

I0 by frangible means, such as one or more shear pins 2|, which hold the two parts in such ldngi-V tudinal relationship with respect to one another as to position the shearing'knife I3 immediatelyv below the diaphragm I9. Assuming that downward movement of the tubular member I I is pre' vented, the subjecting of the fluid abovetheplug A to suflicient pressure causes such iluid toact on the packing I4, body I0 and diaphragm closure I9, exerting sufficient force thereon to shear the screws 2| and move the body and diaphragm downwardly with respect to the tubular' member II, pressing the diaphragm against the circular knife I3, which will pierce and shear it completely from the passage I8. The sheared diaphragm disc portion is forced hydraulically through the central passage in the tubular member completely out of the lower end of the plug. rIlhe extent of telescopic movement of the body I0 over the tubular member II is limited by a suitable stop, which, as shown in the drawings, may consist of a set screw 22 in the body I0 slidable within a longitudinal slot 23' in the member II. The extent of travel of the body, as determined by the length of the slot, need only be sufcient to insure complete cutting out or shearing ofthe plate I9 by the knife I3. In the actual use of the plug A within a well bore, it is pumped down through a well conduit, such as the tubing string B, with the shear screws 2| in place and the diaphragm I9 intact and clamped securely to the body III across the plug passageway I8. The plug proceeds downwardly until its tubular memberv II engages a shoulder 24 in the lower end of the tubing string B, which stops further movement of the plug. The operator is advised of the fact that the plug has been arrested by a pressure rise, as indicated on a suitable gage (not shown) at the top of the well bore. Thereupon, the pressure of the fluid in the tubing string above the plug A is increased until it reaches the predetermined amount required to act across the entire area of the plug and shear its screws 2|, forcing the `body I9 with its attached packing sleeve I4 and closure diaphragm I9 downwardly over the tubular member II. This movement presses the diaphragm I9 against the circular knife I3, which pierces and completely severs it from the body, allowing the fluid in the tubing string to blow it through the tubular member II and out of the passage I8. Any fluid in the tubing string B above the plug A may now be pumped through the plug or discharged through the lower end of .the tubing string.

The diaphragm I9 can be made of any suitable material and in any thickness or number of layers, to withstand the pressure imposed on the plug. The dimensions and characteristics of the diaphragm are such as to preclude its shearing and disengagement from the body Ill by thedirect application of hydraulic pressure alone to its upper surface. It is severed from the body by the cutting action of the knife I3, whichcan become effective only after the screws 2| have been sheared. The shear screws 2| are disrupta- 4 ble and the diaphragm I9 severed from the body IIJ by lower unit hydraulic pressures imposed on the plug than would be required to shear the diaphragm by direct action upon it. The shearing force on the pins 2| and on the cutting edge of the circular knife I3 is provided by the liuid under pressure acting over substantially the entire area. of the plug, allowing larger shear pins to be employed for the same unit hydraulic pressure, and a relatively rigid closure member to be secured across the passage I8. As a result, greater accuracy `in removing the diaphragm at a predetermined pressure is assured, since the ability to use greater dimensional shear screws and diaphragms for the same unit hydraulic shearing pressure minimizes the effect of minute variations in their dimensions and the characteristics of their materials.

The circular shearing blade I3 completely severs and allows removal of the diaphragm I9 from the passage I8, leaving no portions extending into it as obstructions to the free passage of fluids. The relatively small area available for the central passage I8 makes it highly desirable that it be completely open after its closure member has been pierced, to prevent restrictions to the flow of fluids through the plug. f-

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. A well plug including a tubular body having a passage therethrough, a packing surrounding said body and movable therewith, said packing being adapted for slidable sealing engagement with a well conduit, breakable means secured to said body across its passage to close the same, whereby the packing, the body and the breakable means are subjectable to the pressure of fluid in the well conduit thereabove, a member telescoped Within said body below said breakable means and having means at its upper end for disrupting said breakable means, said member being adapted to be held stationary to provide for relative movement between said body and member.

2. A well plug including a tubular bodyhaving a passage therethrough, a packing surrounding said body and movable therewith, said packing being adapted for slidable sealing engagement with a well conduit, breakable means secured t0 said body across its passage to close the same. whereby the packing, the body and the breakable means are subjectable to the pressure of fluid in the well conduit thereabove, a member telescoped within said body below said breakablemeans and having a circular knife at its upper end for cut:- ting said breakable means, saidmember being adapted to be held stationary to provide for relative movement between said body and member.'

3. A well plug including a tubular body having a passage therethrough, a packing surrounding said body and movable therewith, said packing being adapted for slidable sealing engagement with a well conduit, a diaphragm secured to 'said body across its passage to close the same, whereby the packing, the body and the diaphragm are subjectable to the pressure of fluid in the well conduit thereabove, a member telescoped within said body below said disphragm and having means at its upper end for piercing said diaphragm, said member being adapted to be held stationary to provide for relative movement between vsaid body and member.

` 4. A well plug including a tubular body having a passage therethrough, a packing surrounding said body and movable therewith, said kpacking being adapted for slidable sealing engagement with a well conduit, a diaphragm secured to said body across its passage to close the same, whereby the packing, the body and the diaphragm are subjectable to the pressure of fluid in the well conduit thereabove, a tubular member telescoped Within said body below said diaphragm and having a circular knife at its upper end for severing said diaphragm, said member being adapted to be held stationary to provide for relative movement between said body and member.

5. A well plug including a tubular body having a passage therethrough, a packing surrounding said body and movable therewith, said packing being adapted for slidable sealing engagement with a well conduit, breakable means secured to said body across its passage to close the same, whereby the packing, the body and the breakable means are subjectable to the pressure of fluid in the well conduit thereabove, a member telescoped within said body below said breakable means and having means at its upper end for disrupting said breakable means, said member being adapted to be held stationary to provide for relative movement between said body and member, and frangible means initially securing said member to said body.

6. In combination, a well conduit having a stop shoulder, a well plug including a tubular body having a passage therethrough, a packing on said body adapted for slidable sealing engagement with said conduit, a diaphragm secured to said body across its passage to close the same, a tubular member having a cutting edge at its upper end for cutting said diaphragm and telescoped within said body below said diaphragm, said tubular member being engageable with said stop shoulder, and stop means for limiting the extent of downward movement of said body along said tubular member.

7. In combination, a well conduit having a stop shoulder, a well plug including a tubular body having a passage therethrough, a packing surrounding said body and movable therewith, said packing being adapted for slidable sealing engagement with said well conduit, breakable means secured to said body across its passage to close the same, whereby the packing, the body and the breakable means are subjectable to the pressure of fluid in the well conduit thereabove, a member telescoped within said body below said breakable means and having means at its upper end for disrupting said breakable means, said member being held stationary by engagement with said stop shoulder to provide for relative movement between said body and member to effect disruption of said breakable means by said means at the upper end of said member.

8. In combination, a well conduit having a stop shoulder, a well plug including a tubular body having a passage therethrough, a packing on said body adapted for slidable sealing engagement with said conduit, a diaphragm secured to said body across its passage to close the same, a tubular member having a cutting edge at its upper end for cutting said diaphragm and telescoped within said body below said diaphragm, said tubular member being engageable with said stop shoulder, frangible means initially securing said member to said body to prevent downward movement of said body along said member and disruption of said diaphragm by said cutting edge, and stop means for limiting the extent of downward movement of said body along said tubular member.

FRANK D. SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 19,952 Crowell Apr. 28, 1936 1,569,293 Miller Jan. 12, 1926 1,884,165 Otis Oct. 25, 1932 1,994,072 Hardcastle Mar. 12, 1935 2,197,396 Mairies Apr. 16, 1940 2,232,688 Boynton Feb. 25, 1941 2,295,418 Mims Sept. 8, 1942 2,352,744 Stoddard July 4, 1944 2,382,578 Penick Aug. 14, 1945

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