US3437137A - Conduit plug for separating fluids - Google Patents

Description

April 8, 1969 SCOTT 3,437,137

CONDUIT PLUG FOR SEPARATING FLUIDS Filed Oct. 15, 1967 INVENTOR V46 5. 560T) A TTOZ/Vy April 8, 1969 L. B. SCOTT Filed 001.- 13, 1967 CONDUIT PLUG FOR SEPARATING FLUIDS INVENTOR United States Patent O 3,437,137 CONDUIT PLUG FOR SEPARATING FLUIDS Lyle B. Scott, South Gate, Califi, assignor to Byron Jackson Inc, Long Beach, 'Calif., a corporation of Delaware Filed Oct. 13, 1967, Ser. No. 675,237 Int. Cl. EZlb 33/16 US. Cl. 166-453 9 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention This invention relates to pipe plugs which may be pumped through a pipe conduit for keeping pumped fluids separated. More specifically, the invention is related to oil well cementing plugs used when pumping a cement slurry down through a well casing to force it into the annular space between the casing and the well bore to cement the casing in place and seal off the formation strate.

Whenever an oil well is drilled, casing is lowered into the Well bore, which is generally filled with drilling mud. The casing must be cemented in place by pumping a predetermined amount of cement slurry down through the casing, out the bottom, and up into the annular space between the casing and the Well bore, displacing the drilling mud ahead of it. In order to completely pump out the cement slurry from the casing, additional fluid, which may be drilling mud, is pumped behind the slurry. To avoid contamination of the cement slurry, a forward or bottom cementing plug with a frangible diaphragm and made of rubber or other elastomeric material is inserted in the casing between the drilling mud and the slurry, and a following or top cementing plug, also of resilient material, may be inserted above the cement, ahead of the pumping fluid. When the bottom plug is pumped down against an annular seat or stop near the lower end of the casing, differential pressure then causes its diaphragm to rupture, allowing the cement slurry to flow out the bottom of the casing and into the annulus. When the top plug reaches the bottom plug, a seal is effected, allowing no more flow, and the cement is allowed to set. Depending on subsequent operations required in the well, the plugs and any residual cement in the casing may then be drilled out.

Description of the prior art Heretofore, cementing plugs as commonly used in oil well cementing operations have been of the type shown and described on page 2281 of the 1966-67 (27th revision) of the Composite Catalog of Oil Field Equipment and Services, published by World Oil, a Gulf Publishing Company Publication, Post Oflice BoX 2608, Houston, Tex. 77001.

The plugs have a generally cylindrical body portion, usually made of rubber or synthetic rubber, and substantially smaller in outside diameter than the inside of the casing, the body portion being reinforced by a generally cylindrical metal portion, usually of aluminum so that it is drillable, and around which the rubber body is molded. The plugs have a series of parallel, flexible lips, integral with the body portion, formed during the molding process, the lips being larger in outside diameter than the bore of the casing in order to provide a wiping and sealing action against the casing Wall; and the lips effect a limited amount of resilient centering of the plug in the casing. The bottom or leading lip merges into the body portion of the plug to form a leading or nose portion. In the intermediate portion is a series, generally three, of wiping lips, and at the top or rear end of the plug is a sealing or cup lip, the inside of which is adapted to form a conical cup above the body portion of the plug.

The generally cylindrical metal portion of the plug used as a bottom cementing plug has a continuous bore, but the bottom of the conical cup provides a diaphragm forming an obstruction at the upper end of the cylindrical reinforcing member. The generally cylindrical metal portion of the plug used as a top cementing plug has a closed rearward end, so that there is a substantial thickness of cushioning and sealing rubber in the body of the plug between the top or closed end of the metal and the cup portion of the plug.

Since the lips of the cementing plugs must necessarily be resilient in order to seal inside the casing and so that the plugs may be pumped through the casing, they do not provide adequate lateral support to preclude twisting of axial misalignment with the casing, either lateral or angular, or both, under the high pressures used in pumping. Thus with cementing plugs as commonly used, problems of leakage and contamination of the cement slurry arise when the plugs become axially misaligned with the casing as they are being pumped through it, or when they are seated because the rubber or elastomeric material in the plugs tends to become fluid under high pressure, or one side may tend to hang up or snag due to different friction characteristics in the casing surface or at the joints.

SUMMARY OF THE INVENTION In order to overcome the shortcomings of plugs of the prior art, therefore, it is one of the objects of this invention to provide a cementing plug which is self-guiding and self-centering as it travels through the pipe.

Another object of the invention is to provide a cementing plug which remains centered and axially aligned with the pipe through which it is passing to assure uninterrupted wiping and sealing as it passes therethrough.

An additional object of the invention is to provide a cementing plug, the cup or sealing lip of which is increasingly backed up or supported as pressure against the plug is increased, thus providing added strength to the plug for more eifective sealing as needed when added pressure is applied.

Still another object of the invention is to provide a cementing plug with a positive pack-off and seal when seated to prevent any movement or flow of the cement during the setting period.

The invention is embodied in a plug of the type used for separating fluids in a conduit, the plug having a generally cylindrical body having a diameter less than the internal diameter of the conduit; a plurality of circumferential flexible lips of elastomeric material carried by the body coaxially therewith, axially spaced thereon and extending outwardly therefrom, the lips having outer diameters greater than the internal diameter of the conduit; the body and the lips defining a plug adapted to be inserted in the conduit with the lips slidably engaging the inner wall of the conduit for resiliently centering the body in the conduit and for sealing the body to the inner wall to separate fluids in the conduit at opposite ends of the plug; wherein the improvement comprises: guide means carried by the body, the guide means extending radially outward from the body and defining a generally cylindrical outer surface coaxial with the body, the surface having a diameter greater than the diameter of the body, less than the outer diameter of the lips, and substantially equal to the internal diameter of the conduit, the surface adapted, when the plug is in the conduit, to slidably contact the inner wall of the conduit for more positively centering the body in the conduit. Additionally, the improvement may comprise: the body having an elastomeric portion deformable in response to axially directed fluid force acting on an end of the plug to expand the elastomeric portion radially; and a radial flange of elastomeric material integral with the elastomeric portion, the flange having a cylindrical outer surface coaxial with the body, the surface having a diameter greater than the diameter of the body, less than the outer diameter of the lips, and substantially equal to the internal diameter of the conduit; the surface adapted, when the plug is in the conduit, to slidably contact the inner wall of the conduit for more positively centering the body in the conduit and, in response to radial expansion of the elastomeric portion, to be expanded into packing relation with the inner wall of the conduit.

The problems encountered with plugs of the prior art as generally used have been alleviated with the plugs of the present invention by incorporation of the generally cylindrical guide or flange means integral With the plug body and extending outwardly to adjacent the bore of the casing. Without the guide means, because of the resilience of the lips and the clearance between the body of the plug and the casing, the plug is not positively centered in the casing and the sealing lip is not adequately backed up, so that, with a high differential pressure on the two sides of the plug, leakage may occur. This is particularly undesirable when the plug is seated and supposed to pack off to preclude any leakage when the cement is being set or hardening. Plugs as previously made have not been able in many instances to prevent such leakage, but the cylindrical guide ring or back-up ring of this invention overcomes that deficiency by centering the plug and backing up the lip to prevent flow-by.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the accompanying drawings:

FIG. 1 is a longitudinal view, partly in section, of a top plug of the invention;

FIG. 2 is a longitudinal View, partly in section, of a bottom plug of the invention;

FIG. 3a is a longitudinal sectional view of a well bore with a casing therein, and the foregoing top plug and the foregoing bottom plug in place inside the casing with cement slurry between the plugs;

FIG. 3b is a longitudinal sectional view similar to FIG. 3a, but with the top plug having been pumped down against the bottom plug, and the slurry having passed through the ruptured diaphragm of the bottom plug;

FIG. 4 is a longitudinal view, partly in section, and on the same scale as FIGS. 1 and 2, of the top plug inside the casing; and

FIG. 5 is a longitudinal view, partly in section, and on the same scale as FIGS. 1 and 2, of the bottom plug inside the casing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the top cementing plug is shown with its elastomeric, generally cylindrical body portion 12, reinforced by being molded around a drillable metal insert 14, which has a peripherally flanged forward or lower end 14' and is open at its lower end to an inner bore 15. Molded integrally with the body 12 is a series of spaced, outwardly and rearwardly extending circumferential elastomeric lips 16, 18, 20, including a nose lip 16,

merging into a conical nose 17 at the lower or leading end of the plug 10, three wiping lips 18, and a sealing or cup lip 20, the inside of which forms a cup 21 at the rearward or top end of the plug 10. Between the bottom of the cup 21 and the closed or top end of the insert 14 is a mass of elastomeric or rubber material forming a packer portion 13 of the body 12. Guide means in the form of a cylindrical peripheral gauge ring 22 is provided between lips 18 and 20, the guide means 22 being in the form of an integral, circumferential flange extension of the periphery of the body 12 adjacent to and backed up by the packer portion 13, and merging integrally with the rearward or following lip 20.

FIG. 2 shows the bottom cementing plug 30 with its elastomeric, generally cylindrical body portion 32, reinforced by being molded around a generally cylindrical drillable metal insert sleeve 34, which has an inner bore and peripherally flanged ends 33, 33 at the rearward and forward ends, respectively. Molded integrally with the body 32 is a series of spaced, outwardly and rearwardly extending circumferential elastomeric lips 36, 38, 40, including a nose "lip 36, merging into a conical nose 37 at the lower or leading end of the plug 30, three wiping lips 38, and a sealing or cup lip 40, the inside of which forms a cup 41 at the rearward or top end of the plug 30. Extending over the bottom of the cup 41 at the top of the body portion 32 is a frangible diaphragm 44, which seals off the upper end of the opening 35 in the sleeve 34. Guide means in the form of a cylindrical peripheral gauge ring 42 is provided between lips 38 and 40, the guide means 42 being in the form of an integral, circumferential flange extension of the periphery of the body 32, adjacent to and supported or backed up by the flange 33 of the reinforcing sleeve 34, and merging integrally with the rearward or following lip 40.

As an example of typical plugs 10, 30 of this invention, for a typical size casing, with 5 /2 outside diameter and 4%" inside diameter, the dimensions of the plugs would be approximately as follows: overall length 8%, with a body length 7%, outer body diameter 3%, and outer diameter of the lips 5", diaphragm thickness and packer portion 13 thickness 3". The cylindrical guide means 22, 42 should be 4 3/ in diameter for a close fit with the casing bore 57, and approximately 1" long, in the form of a flanged portion of the rearward end of the body 12, 32 and merging into the sealing lip 20, The plugs 10, 30, exclusive of the reinforcing inserts 14, 34, are molded of an abrasive-resistant, drillable elastomeric material, such as rubber or synthetic rubber of Shore A 45-65 hardness; and the inserts 14, 34, around which they are molded, of a rigid, drillable material, such as cast aluminum.

In FIG. 3a is shown a well borehole drilled into an earth formation 52, with lengths of casing 56, joined by couplings 62, lowered into the drilling mud 66 contained in the hole 50 until the guide shoe 58 on the bottom of the casing is adjacent to the bottom 51 of the hole 50, the casing 56 being centered in the well 50 by means of centralizers 60, to form an annular space 54. Between the lengths of casing 56, at the coupling 62, is an annular seat 64 on which rests the nose 37 of the bottom plug 30. Alternatively, seat 64 may be omitted, the nose 37 of the plug 30 resting on the top of guide shoe 58. Higher up inside the casing is plug 10, with cement slurry 68 in the casing between the two plugs 10, 30. In the casing 56 above the top plug 10 is pumping fluid or mud 67 for pumping down the top plug 10 and the cement slurry 68.

In FIG. 3b, the top plug 10 is shown having been forced downward by the pressured mud 67, its conical nose 17 engaging the cup 41 of the bottom plug 30, the differential pressure having first broken the frangible diaphragm 44 of the bottom plug 30, allowing the cement slurry 68 between the two plugs 10, 30 to flow downward through the opening 35 of the insert sleeve 34 of the bottom plug 30, the annular seat 64, the casing 56, the guide shoe 58, and on out and upward into the annular space 54 between the casing 56 and the hole 50, where the cement 68 can set and harden.

Referring to FIGS. 4 and 5, it is seen that when the cementing plugs 10, 30' are in operating positions inside the casing 56, their resilient lips 16, 18, 20 and 36, 38, 40,

being larger than the inside bore 57 of the casing 56, preferably on the order of /s to larger, are flexed inwardly in wiping and sealing contact with the casing bore 57, while the guide means or cylindrical gauge rings 22, 42 are substantially in contact with the casing bore 57, the diametral clearance being preferably on the order of ,4, or a little more. It may be seen also that the body portions 12, 32 of the plugs 10, 30 are of greater length than the diameter of the inner bore 57 of the casing 56, in order to avoid any tendency of the plugs to tumble when moving through the casing. In FIGS. 4 and 5 also, it is evident that cup lips 20, 40 of plugs 10, 30 are prevented from extruding between the body portions 12, 32 and the casing bore 57 When pressure is exerted against them because they are backed up by their respective cylindrical guide flange portions 22, 42.

In the use of the cementing plugs 10, 30 of this invention for cementing a string of casing 56 to a well bore 50, the latter containing drilling mud 66, the environmental conditions are generally as shown in FIG. 3a and as described aoove.

The forward or bottom cementing plug 30 is inserted in the casing 56 at the top end (not shown) of the casing, a slurry valve (not shown) opened to allow cement slurry 68 under pressure behind the plug 30 to pump the latter downward through the bore 57 of the casing 56 until the nose 37 of the plug 30 seats on the annular seating ring 64, as shown in FIG. 3a. When the plug 30 is inserted in the casing bore 57 and travels therethrough, it assumes the configuration as shown in FIG. 5, the nose 37 at the leading end being backed up by the lower flange 33 of the insert sleeve 34 and the cylindrical guide means or flange 42 being backed up by the upper sleeve flange 33, thus assuring axial alignment of the plug 30 with the casing 56. The lips 36, 38, 40 are in sealing contact with the casing wall 57 to provide effective wiping and cleaning of the wall as the plug travels through it and effective sealing to prevent channeling or leakage of either drilling mud 66 or cement slurry 68. This effective wiping and sealing is assured by the guide flange 42 which is substantially in contact with the casing bore 57 to keep the plug 30 axially aligned with the casing 56 even when passing through uneven spots in the casing bore 57 or when traveling past the casing joints at each coupling 62. Without the lateral support provided by the reinforced guide means 42 closely guiding the plug 30 through the casing bore 57, the lips 36, 38, 40 by themselves, being flexible for sealing and wiping action, would be unable to resist the tendency of the plug to twist axially in the casing. Lip 40 of cup 41 is backed up by ring 42 as pressure is exerted against it, thus reinforcing the seal 40 and preventing any extrusion of it, even at high pressures, around the body portion 32 of the plug 30.

When a suflicient, predetermined volume of cement slurry 68 has been pumped into the casing 56 behind the bottom plug 30 for adequately filling the annulus 54, the slurry valve (not shown) is closed, the following or top cementing plug is inserted in the casing 56 at the top end (not shown) of the casing behind the cement slurry 68, and a pumping fluid or mud valve (not shown) opened to allow fluid 67 under pressure behind the plug 10 to pump the latter downward through the bore 57 of the casing 56 until the nose 17 of the plug 10 engages the cup 41 of the plug 30. Prior to the convergence of the two plugs 10, 30, however, the initial pressure differential on either side of the diaphragm 44 of the bottom plug 30 has broken the diaphragm, allowing the cement slurry to flow downwardly through the ruptured diaphragm 44, the opening 35 of the reniforcing sleeve 34 of the plug 30, the annular seat 64, the casing 56 below the plugs, the guide shoe 58, and on out and upward into the annular space 54 between the casing 56 and the well 50, where the cement 68 may harden and set. See FIG. 3b. When the plug 10 is inserted in the casing bore 57 and travels therethrough, it assumes the shape as illlustrated in FIG. 4, the nose 17 at the leading end being backed up by the flange 14' of the reinforcing insert 14 and the cylindrical guide means or flange 22 being backed up by the mass of elastomeric material in the packer portion 13 of the top plug 10, thus assuring axial alignment of the plug 10 with the casing 56. The lips 16, 18, 20 are in sealing contact with the casing wall 57 to provide effective wiping of cement slurry 68 ahead of the plug and effective sealing to prevent channeling or leakage of either pumping fluid 67 or cement slurry 68. This effective wiping and scaling is assured by the guide flange 22, which is substantially in contact with the casing bore 57 to keep the plug 10 axially aligned with the casing 56 even when passing through casing joints at each coupling 62 or uneven spots in the casing bore 57. Without the lateral support provided by the reinforced guide means 22 closely guiding the plug 10 through the casing bore 57, the lips 16, 18, 20 by themselves, being flexible for sealing and wiping action, would be unable to resist the tendency of the plug to twist axially in the casing. The guide means in the form of the flanges 22, 42 of the plugs 10, 30, also assure their mutual alignment on convergence and complementary engagement of the nose 17 with the cup 41, providing a positive pressure against the latter to tightly force the lip 40 against the inner surface 57 of the casing 56. When thus engaged, as shown in FIG. 3b, pressure on the cup 21 from the fluid 67 tends to compress the packer portion 13 of the top plug 10, forcing the cup lip 20 in tight engagement with the casing bore 57, the compression of the packer portion 13 at the same time forcing outwardly the peripheral guide flange 22 into tight packing engagement with the bore 57 of the casing 56, and to back up the cup lip 20, thus precluding the further fluid flow which could adversely affect the setting of the cement 68.

After the cement 68 has hardened and set, and depending on subsequent operations to be performed in the well, the residual cement, plugs 10, 30, seat 64, and shoe 58 may be drilled out of the casing.

Above is described a typical cementing operation using a pair of plugs 10, 30; however, a cement job may also be performed using only a bottom plug 30. The procedure is the same as described above to the point where the cement slurry 68 is pumped into the casing 56 behind the plug 30. A suflicient, predetermined volume is used for adequately filling the annulus 54 with enough reserve so that the casing 56 still contains some cement 68 when the annulus 54 is filled. When the proper amount of cement slurry 68 has been pumped into the casing 56, the slurry valve (not shown) is closed and the pumping fluid or mud valve (not shown) is opened to allow the fluid 67 under pressure behind the cement slurry 68 to pump the latter downward through the bore 57 of the casing 56. During the pumping, when the differential of pressure in the zone of the drilling mud 66 to that in the zone of the cement slurry 68 is great enough, the frangible diaphragm 44 ruptures, allowing the slurry 68 to flow downwardly through the ruptured diaphragm 44, the opening 35 of the reinforcing sleeve 34 of the plug 30, the annular seat 64, the casing 56 below the plug 30, the guide shoe 58, and on out and upward into the annular space 54 between the casing 56 and the well 50. The cement 68 may then harden and set, following which the residual cement, plug 30, seat 34, and shoe 58 may be drilled out of the casing, if desired.

It is evident that the plugs of this invention possess many novel and advantageous features not found in plugs of the prior art. For example, the guide means 22, 42 provide positive centering and guiding of the plugs 10, 30 in the casing 56; and prevent misalignment or tumbling of the plugs, so that contact of the lips 16, 18, 36, 38, 40 is assured, resulting in more effective wiping and sealing against the casing bore '57. The guide rings or flanges 22, 42 are backed up positively by the packer portion 13 and the insert flange 33, respectively, of the plug bodies 10, In the top plug 10, the packer portion 13 reacts under axially applied pressure to become compressed longitudinally and expanded radially, resulting in expansion of the guide means 22 in tighter engagement with the inside 57 of the casing 56, for more effective centering and packing. Sealing of the lips 20, against the casing bore 57 is also enhanced by their being backed up by the guide means 22, 42 substantially in contact with the inside of the casing. These advantages are not present in prior art plugs, in which the latter are only resiliently centered by the flexible lips, and in which, under high differential pressures, the sealing lip may be extruded into the space between the plug body and the casing, resulting in leakage.

While two forms of the device have been illustrated and described, it should be understood that various modifications will occur to those skilled in the art. For example, although the reinforcing inserts 14, 34 have been described as being of drillable metal, other drillable materials might be used, such as plastics or hard rubber; and although the flanges or guide means 22, 42 are shown just below the cup lips 20, 40 near the top of the elastomeric body portion '12, 32 of the plugs 10, 30, respectively, or rearward from the direction of travel of the plugs, they could also be located nearer to the lower or leading ends of the plugs; and the rupturable diaphragm 44, rather than being of the same elastomeric material as the body 32, could be of other frangible materials, such as plastics.

I claim:

1. A plug for separating fluids in a conduit, said plug having:

(a) a generally cylindrical body having a diameter less than the internal diameter of the conduit;

(b) a plurality of circumferential flexible lips of elastomeric material carried by said body coaxially therewith, axially spaced thereon and extending outwardly therefrom, said lips having outer diameters greater than the internal diameter of the conduit;

(c) said body and said lips defining a plug adapted to be inserted in the conduit with said lips slidably engaging the inner wall of the conduit for resiliently centering said body in the conduit and for sealing said body to said inner wall to separate fluids in the conduit at opposite ends of the plug; wherein the improvement comprises:

guide means carried by said body, said guide means extending radially outward from said body and defining a generally cylindrical outer surface coaxial with said body, said surface having a diameter greater than the diameter of said body, less than the outer diameter of said lips, and substantially equal to the internal diameter of the conduit, said surface adapted, when said plug is in the conduit, to slidably contact the inner wall of the conduit for more positively centering said body in the conduit.

2. A plug as defined in claim 1 wherein said guide means comprises a peripheral flange portion of said body.

3. A plug as defined in claim 1 wherein said guide means is positioned adjacent to one end of said body.

4. A plug for separating fluids in a conduit, said plug having:

(a) a generally cylindrical body having a diameter less than the internal diameter of the conduit;

(b) a plurality of circumferential flexible lips of elastomeric material carried by said body coaxially therewith, axially spaced thereon and extending outwardly therefrom, said lips having outer diameters greater than the internal diameter of the conduit;

(0) said body and said lips defining a plug adapted to be inserted in the conduit with said lips slidably engaging the inner wall of the conduit for resiliently centering said body in the conduit and for sealing said body to said inner wall to separate fluids in the conduit at opposite ends of the plug;

wherein the improvement comprises:

(A) said body having an elastomeric portion deformable in response to axially directed fluid force acting on an end of said plug to expand said elastomeric portion radially; and

(B) a radial flange of elastomeric material integral with said elastomeric portion, said flange having a cylindrical outer surface coaxial with said body, said surface having a diameter greater than the diameter of said body, less than the outer diameter of said lips, and substantially equal to the internal diameter of the conduit;

(C) said surface adapted, when said plug is in the conduit, to slidably contact the inner wall of the conduit for more positively centering said body in the conduit and, in response to radial expansion of said elastomeric portion, to be expanded into packing relation with the inner wall of the conduit.

5. A plug as defined in claim 4 wherein said radial flange is positioned adjacent to one end of said body.

6. A plug for separating fluids in a conduit, said plug having:

(a) a generally cylindrical body having a diameter less than the internal diameter of the conduit;

(b) a plurality of circumferential flexible lips of elastomeric material carried by said body coaxially therewith, axially spaced thereon and extending outwardly therefrom, said lips having outer diameters greater than the internal diameter of the conduit;

(0) said body and said lips defining a plug adapted to be inserted in the conduit with said lips slidably engaging the inner wall of the conduit for resiliently centering said body in the conduit and for sealing said body to said inner wall to separate fluids in the conduit at opposite ends of the plug;

wherein the improvement comprises:

(A) said body having an elastomeric portion deformable in response to axially directed fluid force acting on an end of said plug to expand said elastomeric portion radially; and

(B) a radial flange of elastomeric material integral with said elastomeric portion, said flange having a cylindrical outer surface coaxial with said body, said surface having a diameter greater than the diameter of said body, less than the outer diameter of said lips, and substantially equal to the internal diameter of the conduit;

(C) a portion of said flange also being integral with a portion of one of said lips for reinforcing the latter against axial displacement;

(D) said surface adapted, when said plug is in the conduit, to slidably contact the inner wall of the conduit for more positively centering said body in the conduit and, in response to radial expansion of said elastomeric portion, to be expanded into packing relation with the inner wall of the conduit.

7. A plug as defined in claim 6 wherein said radial flange is positioned adjacent to one end of said body. 8. A plug for separating fluids in a conduit, said plug having:

(a) a cylindrical body of elastomeric material having a diameter less than the internal diameter of the conduit and a length greater than the internal diameter of the conduit, and having a forward end and a rearward end; (b) a cylindrical reinforcing member of aluminum carried by said body and having a forward end and a rearward end, said member having an outwardly extending circumferential flange at either end, and an axial opening therethrough;

(c) a frangible diaphragm of elastomeric material, integral with said body at the rearward end thereof, and obstructing said opening at one end of said member;

(d) a nose lip of elastomeric material, integral with said body, coaxial therewith and extending outwardly and rearwardly therefrom adjacent its forward end, with an outer diameter greater than the internal diameter of the conduit;

(e) a cup lip of elastomeric material, integral with said body, coaxial therewith and extending outwardly and rearwardly therefrom adjacent to its rearward end, with an outer diameter greater than the internal diameter of the conduit, the internal portion of said cup lip and the rearward portion of said diaphragm defining a cup rearward of said dy;

(f) a plurality of wiping lips of elastomeric material, integral with said ody, coaxial therewith, extending outwardly and rearwardly therefrom and axially spaced between said nose lip and said cup lip, with an outer diameter greater than the internal diameter of the conduit;

(g) a nose cone of elastomeric material, integral with said body, coaxial therewith and extending radially outwardly from said forward flange of said reinforcing member, and merging conically with said nose lip and said forward end of said body;

wherein the improvement comprises:

a flange portion of elastomeric material integral and coaxial with said body, extending radially outwardly from said rearward flange of said reinforcing member, and merging with said cup lip, and with an outer peripheral surface having a diameter greater than the diameter of said body, less than the outer diameter of said lips, and substantially equal to the internal diameter of the conduit, whereby said flange is adapted to reinforce said cup lip and to slidably contact the inner wall of the conduit for more positively centering said body when said plug is in the conduit.

9. A plug for separating fluids in a conduit, said plug having:

(a) a cylindrical body of elastomeric material having a diameter less than the internal diameter of the conduit and a length greater than the internal diameter of the conduit, and having a forward end and a rearward end;

(b) a generally cylindrical reinforcing member carried by said body and having a forward end and a rearward end, said member having an outwardly extending circumferential flange at its forward end, and an axial opening at its forward end extending to a closure at its rearward end;

(c) a packer portion of elastomeric material, integral with said body, extending from the rearward end of said closure of said reinforcing member to said rearward end of said body, and deformable in response to axially directed fluid force acting on an end of said plug to expand said packer portion radially;

(d) a nose lip of elastomeric material, integral with said body, coaxial therewith and extending outwardly and rearwardly therefrom adjacent to its forward end, with an outer diameter greater than the internal diameter of the conduit;

(e) a cup lip of elastomeric material, integral with said body, coaxial therewith and extending outwardly and rearwardly therefrom adjacent to its rearward end, with an outer diameter greater than the internal diameter of the conduit, the internal portion of said cup lip and the rearward end of said packer portion defining a cup rearward of said body;

(f) a plurality of wiping lips of elastomeric material, integral with said body, coaxial therewith, extending outwardly and rearwardly therefrom and axially spaced between said nose lip and said cup lip, with an outer diameter greater than the internal diameter of the conduit;

(g) a nose cone of elastomeric material, integral with said body, coaxial therewith, and extending radially outwardly from said circumferential flange of said reinforcing member, and merging conically with said nose lip and said forward end of said body;

wherein the improvement comprises:

a flange portion of elastomeric material, integral and coaxial with said body, extending radially outwardly from said packer portion and merging with said cup lip, and with an outer peripheral surface having a diameter greater than the diameter of said body, less than the outer diameter of said lips, and substantially equal to the internal diameter of the conduit, said surface adapted, when said plug is in the conduit, to slidably contact the inner wall of the conduit for more positively centering said body in the conduit and, in response to said radial expansion of said packer portion, to be expanded into packing relation with the inner wall of the conduit.

References Cited UNITED STATES PATENTS 2,124,710 7/1938 Pipes 166-153 2,257,784 10/1941 Brown 166-153 3,100,534 8/1963 Herndon et al 166-153 3,102,595 9/1963 Fisher et al. 166-156 3,191,678 6/1965 Hinson 166-153 OTHER REFERENCES Composite Catalog of Oil Field Equipment and Services, 1966-67 (27th revision), published by World Oil, Gulf Publishing Company, Houston, Tex., (page 2281).

STEPHEN J. NOVOSAD, Primary Examiner.

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