US2672199A - Cement retainer and bridge plug - Google Patents

Description

March 16,1954 P. A, MCKENNA 2,672,199

K CEMENT RETAINER AND BRIDGE PLUG Filed March 12, 1948 Patented Mar. 16, 1954 PATENT oFFicE 2,672,199 itf'r'AIN/ER AND Buinen 'PLUG atrick' A. McKenna, Washington, D. c. Application Maren 12, 1948, 'serial No. 14,413

(o1. lesa-13) Claims;

This invention relates to cement retainers and bridge plugs used, primarily in .Oil andere .Walls to block oi or cement selected ystrata temporarily and in some instances permanently.

An object of the invention is toufacilitatel the operation of packing oir the selected strata at depths where the pressure may be exceedingly high. In the drilling operations, being carried on today depths of from two to three miles are not uncommon.A Such depths are frequently necessary in exploratory work before any sign of oilbearing strata is developed and the pressure in the well at such depths iswconsiderable. My improved arrangement vinsures that an eiective seal may be maintainedu under the` pressures l'developed at these depths.:` and consequently permits an effective cernenting or bridging job.

Another object of the inventions tosimplify the construction of a cjernent paclrer .without in any way detracting from the effectiveness of its operation in performingv its i-intended,function, thereby reducing the `cost qimproduction which is a considerable factorinasmuch as vsuch retainers may be used onlywonce,y and anum'ber of them may be necessary `during the completion of al single well..

Still a further object `Qf Vtheinvention istofso construct and arrange the` vconstituer,1t elements or the mechanismthat therecis nopossibilityI of jamming any of the parts whiletheureta-inervis being lowered and set in thewell. 4T-e, this end I provide aA tubular sleeve surrounding theentire retainer during the operation oi lowering -it into the well, thereby4 precluding anyy possibility of the slips whichY ultimatelytgrip the wall of the well casing expanding beforethe desired level is reached and interferingV with the lowering operation. Not only does the sleeve or tube perform the important function ,.justmentioned, but it is so arranged in conjunction with the elements of the retainer or vpacker per se aslto bring about an importantcooperative'function in obtaining the exceptionally eiec'tiye seal which constitutes one of the primary objects of the invention. Y y, w

In the drawings, whereiriliken'lim"'e'ralsl refer to like parts throughout the iigures;

Fig. 1 is ak longitudinal `sectional view of my improved'retainer; t Y l n l Fig. 2 is a smil-ar viewafter the packing elements and slips have ,been set; A

Fig. 3 is a section throught-:3 9i Fig. 1; Y Fig. 4 illustrates the form assu l"edwby the cups when restrained` byntheenelosing boot- Fig. 5 musuates traforo-assume. byjthsup when the restrain-t of the boot is released, and

` Fig. 6 illustrates the principle to which in large measure the effective seal may be attributed.

Referring now to Fig. 1, the numeral I indicates a well casing into which the retainer assembly is lowered until it reaches the desired depth.` The retainer assembly comprises a tubular mandrel I2l Iexteriorly threaded with a coarse left-hand thread at its upper end, as indicated at It. The threaded upper end is adapted for securernent to the lower end or" a string of pipe with which the retainer assembly is lowered down the casing to the desired level. The lower end of the mandrel l2 is belled outwardly as' indicated at l@ and a seat Il is provided at the base of the enlarged portion for a buoyant ball iii which is prevented from falling through the lower end of the tube by an apertured closure tu which is threaded into the lower end of the mandrel to form a cage within which the ball is free to iioat.

A lower expanding cone 22 is threaded over a shouldered portion 2Q of the mandrel and the threaded portion terminates at a cone shoulder 26 which engages Ia second Shoulder on the mandrel lying substantially in the transverse plane of the ball seat l1. The wall of the mandrel l2 at its lower end is flared to formi a shoulder 2t extending downwardly and outwardly from the lower end of the mandrel.

About this ange 28 a resilient molded sealing cup 30 is seated so `thatthe portion of the cup on the inside of iiange 28 seats against the lower edge of the wall 32 which constitutes the lower extremity of the mandrel and forms the side wall of the cage within which the ball iioats. The cup includes a cylindrical neck portion 38 which lies above the fiange 28 and circumferentially engages wall 32 throughout its length. The upper end of neck 38 seats against shoulder 2t of expanding cone 22 andk lies between the wall 32 of the cage and aperipheral lange St depending from the lower ymargin of the expanding cone 22,A and providing an annular pocket for the upper or free end of the neck.

A metallic ring 36 encircles and holds the neck 38 of the sealing cup under substantial compression against the outside of cage wall 32, the ring 36 being of the same outside diameter as that of flange 34 ofcone 22 at its lower extremity and abutting against the under face of ilange 34.

An upper expanding cone 40 isthreadedly engaged with the lower end of a sleeve` member 42 which` is slidable along the lmandrel wall. A second resilient molded sealing cup 4G is seated about a flared flange i8r of sleeve yL32, which cor responds to ange 28 and is assembled to sleeve 42 in the manner described in conjunction with lower sealing cup 3i). An annular gasket 5t provides a seal between the sealing cup ll@ and the wall of mandrel l2. The upper sealing cup 46 is held in position against sleeve t2 by ring 52 in the manner described with reference to the lower sealing cup.

Segmental slips 54 having lower gripping surfaces 55 and upper gripping surfaces 5t are provided with inclined camming faces St which are held in engagement with the inclined faces E2 of the expanding cones by means of an elastic ring 64 encircling the central portion of the slip segments. The lower gripping surfaces 5t are held in positive engagement with expanding cone 22 by means of shear pins 6G.

I-Iere an important phase of the invention should be pointed out. The sealing cups 3@ and 46 are preferably made of synthetic rubber and molded. The cup material may be bonded or unbonded to the metallic supporting flanges 28 and 48, but it has been found that unbonded neoprene rubber gives eminently satisfactory results.

Exclusive of the neck 33 previously described, each cup 30 comprises a base 'i8 just outwardly of the neck 38 and a lip 'i9 outwardly of the base I8 and merging therewith on a transverse plane 80. As is apparent, each base 'i8 is thicker than its associated lip I9. In the form illustrated, the inner periphery of each base 'is tapers outwardly relatively sharply as compared with the taper of the inner surface of each lip i9, whereby the plane at is deilned by the merger of the inner surfaces of the lip and base of each cup. Obviously, the merger of the lip and base of each cup can be otherwise defined within the scope of the invention as claimed.

As illustrated graphically in Fig. 6, the outside diameter of each of the cups Sil from the free edge of its lip i9 inwardly to a point on its base 78 deilned by the transverse plane A-A of Figure 6 which is located Ysubstantially in the plane of the outer edge of a flange 28 or i3 is a constant diameter which, when unrestrained, as in Figure 6, is substantially greater than the inside diameter of the casing it. However, as best seen in Figure l, when the cups 30 are stretched and compressed for insertion into the boot 6.2, each isV elongated so that the inner terminus of the area of constant diameter extends yfrom the free edge of each lip 'it to a point on the base 18 defined by the transverse plane B-B, Figure l, which is located between the outer edge of one of the rings 36 or 52 and the root of one of the ilanges 28 or 48 but somewhat nearer the associated ring. Likewise, as seen in Figure 2, the inner terminus of the area of constant diameter moves axially outwardly a short distance to the plane of the line C-C, Figure 2, when the boot 68 is removed and the cups expand into engagement with the casing Ii). The line or plane C--C is located on the Ybase 'I8 substantially midway between the outer edge of a ring 36 or 52 and the root of the adjacent flange 23 or 48. Moreover, it is important to note that the major portion of the work in obtaining and maintaining the improved seal is carried on not by the lips 'F9 of the cups but by the bases 'I8 thereof. The thickness of the resilient cup material in this circumferential area is greater than the thickness requisite for what may be termed the outer free ends or lips of the cups which lie beyond said area. In the form illustrated the cups are tapered radially outwardly on the inside from the plane of the shoulders 28 and 48. The outer free ends serve to preclude any possibility ofthe cup walls folding back or buckling under severe pressures.

It is also important that the resiliency characteristic of the material of which the sealing cups are formed be such that it may be stressed without loss of resiliency to an extent where its outside diameter is less than the inside diameter of the casing. An example may be given, but not by way of limitation, to illustrate the oversize diameter of the sealing cup material, when unrestrained. In a casing having an inside diameter of 4.892 inches the outside diameter of the cups from the region of the flanges 23 and 48 throughout their length, when unrestrained, may be approximately 5.3125 inches and the material should be compressible without loss of its resilient characteristics to an outside diameter of approximately 4.4375 inches. Such an arrangement has been found eminently successful.

A sleeve or boot 68 receives the entire retainer assembly as thus described, the inside diameter of the boot 68 being such as to clear the gripping surfaces of the slips when the latter are in the inoperative position and compress the sealing cups 30 and 4S in the manner heretofore explained. The outside diameter of the boot 58 is, as shown, substantially less than the inside diameter of the casing l0. The boot S8 is open at the top but closed at the bottom as indicated at ill. In positioning the retainer assembly in the boot, the resilient sealing cups, because of their form, substance and relative proportions as heretofore described in reference to the inside wall of the casing, are stretched during the relative sliding movement of the boot and the rest of the assembly. This stretching or longitudinal tensioning is accompanied by a substantial compression of the material. It is believedthat the effective seal provided by the cups, and particularly by the circumferential areas adjacent the flanges 28, 48, is largely attributable to the outward radial pressure set up by reaction of the resilient and elastic material when partially released from the combination of tension and compression stresses which had been set up in the material during the assembling of the boot and retainer assembly.

In operation the retainer assembly and boot are lowered into the casing at the end of string of pipe secured thereto at the upper threaded portion I4 to the desired position. During the lowering operation valves or jars in the pipe string above the retainer are opened and the well iluid enters the retainer from above to equalize the pressure inside and outside the boot, thereby preventing collapse. During the lowering operation the ball i8 floats in its cage. Openings or ports 55 in the wall of the boot adjacent the slips serve to equalize the pressure inside the boot between the cups.

When the retainer reaches the desired level in the well, the pumps at ground level are started and fluid under pressure passes down the pipe string to blow off the boot. The ball i8 cannot blow down with the boot because it is housed in a cage and after the boot has been displaced the ball floats up to seat at the upper end of its cage as soon as the pumps at ground level are cut oil. This prevents the well fluid from entering the retainer through the tubular mandrel l2.

When the boot is blown oil, the upper and lower sealing cups, released from restraint, expand radially outwardly at once to form a sealing contact with the well easing. By virtue of thev manner in which the sealing cups are associated with the mandrel and the force with which their outer walls grip the inside wall of the casing on release of the compressive and tensile strain due to the boot, an exceptionally strong seal is provided.

The pumps having been shut off after the boot was blown and the sealing cups having set, the pipe string by which the retainer was lowered into the well is pulled up slightly, during which operation the upper cup 46 is held against any possible upward slipping movement by reason of the pressure of the well iiuid above it. During this pull-up the upper ends of the, slips move over the upper expanding cone to force the upper gripping surface out against the restraining pressure of the elastic ring 64 to engage the wall of the casing, `Substantially simultaneously with this movement the shear pins 66 are broken and the upward movement of lower expanding cone 22 against the slips forces the lower gripping surfaces 56 outwardly into engagement with the casing wall. This operation is possible because of the fact that the tubular mandrel l2 and the lower expanding cone 22 threaded thereto, with its associated lower sealing cup, is free to slide upwardly with reference to the slips, upper cone and sealing cup assembly.

Subsequent downthrust of the pipe string by which the retainer was lowered assures the set of the upper gripping surfaces 58, the pull-up having been positively stopped when the lower gripping surfaces of the slips engaged the wall of the casing.

After the cementing operation a bridging ball i2 may be dropped down the pipe string to seat upon shoulder l@ adjacent the upper end of the tubular mandrel l2 to seal the retainer from above. The pipe string by which the retainer was lowered is then backed 01T the tubular mandrel l2. All the metal parts of the assembly are of drillable material.

As aforesaid, the pressures the plug must withstand are tremendous, However, the structure of each of thecups 30 and 4B is such as to withstand much more pressure than can previously known cups. In the first place, as the cups each have a normal outside diameter throughout substantially its entire length which is greater than the inside diameter oi the casing l0, each cup is always under compression and is not fully expanded even after the boot 68 has been removed and each cup is engaged with casing I0. This fact enables each cup to resist bursting pressures better than can a cup whose normal diameter is less than that of the casing throughout its length except for the region of the cup lip.

Then, too, the cups of the invention are strengthened in the danger areas by being provided with walls of increased thickness in the regions of the anges 28 and 4B. Also, the flanges 28 and 48 provide internal reinforcements for the cups in the areas where the cups are most vulnerable to bursting pressures.

Finally, the rings 52 and 36 cooperate with the flanges is and 2B, respectively to prevent the cups 3Q and Al from being stripped from the bases 42 and 32 when the cups are stretched and compressed sufficiently to permit the boot 68 to be applied to the plug. This is an important feature as considerable stress must be imposed on the cups at this time and known bonds between the cup necks and the metal parts lof the mandrel consistently failed until the coopresilient sealing cup flxedly engaged with said mandrel, said. cup comprising a relatively thick vbase and a relatively thinner lip. depending therefrom, said lip and at least an adjacent portion of said base providing an elongated cylindrical cup wall having an unrestrained outside diameter throughout its length which is greater than the inside diameter of the casing, a downwardly removable sleeve of lesser diameter than said casing surrounding said cupand holding the same under compression to permit the insertion of said sleeve and cup into said casing, said entire cup wall upon removal of said sleeve being adapted to expand by its own resiliency suiciently to engage the casing throughout the entire length of said cup wall, and said cup expanding progressively from said base to said lip as said sleeve is removed, whereby said base engages said casing at least slightly before said lip.

2. In a cement retainer and bridge plug for sealing off the casing of a well at a desired depth, the combination with a central tubular run-in mandrel, of at least a lower downwardly directed resilient sealing cup xedly engaged with said mandrel adjacent the lower end thereof, said cup comprising a relatively thick base and a relatively thinner lip depending therefrom, said lip and at least an adjacent portion of said base providing an elongated cylindrical cup wall having an unrestrained outside diameter throughout its length which is greater than the inside diameter of said casing, removable means normally compressing said cup to a diameter less than the inside diameter of said casing to permit the insertion of said cup and mandrel into said casing, said entire cup wall upon removal of said removable means expanding by its own resiliency into sealing engagement with said casing, and said removable means being removable so that said cup wall expands progressively from said base to said lip, whereby said base engages said casing at least'slightly before said lip.

3. In a cement retainer and bridge plug for sealing ofi the casing of a well at a desired depth, the combination with a central tubular run-in mandrel having upper and lower ends, of upwardly and downwardly directed resilient cups iixedly engaged with said mandrel in the region of said upper and lower ends respectively, each cup comprising a relatively thick inwardly disposed base and a relatively thinner lip extending axially outwardly therefrom, the lip and at least an adjacent portion of the base of each cup together providing an elongated cylindrical cup wall having an unrestrained outside diameter throughout its length which is greater than the inside diameter of said casing, a downwardly removable sleeve of lesser diameter than said casing surrounding both of said cups and holding the same under compression to permit the insertion of said mandrel and cups into said casing, said cup walls upon removal of said sleeve expanding by their own resiliency into sealing engagement with said casing throughout the entire 7 lengths of said cup walls, and said downwardly directed cup expanding progressively from said base to said lip as said sleeve is removed, whereby its base engages said casing at least slightly before its lip.

4. In a cement retainer and bridge plug for sealing oil the casing of a well at a desired depth, the combination with a central tubular run-in mandrel, of deformable and resilient means surrounding said mandrel and xed thereto, said sealing means having an upper and lower end, said sealing means having an elongated cylindrical outer surface engageable throughout its length with said casing to seal the latter, said sealing means when unrestrained having an outside diameter throughout the length of said cylindrical outer surface which is substantially greater than the inside diameter of said casing, removable means compressing said sealing means to an outside diameter less than the inside diameter of said casing to permit the insertion of said mandrel and sealing means into said casing, and said removable means being so removable that said sealing means expands progressively from said upper to said lower end, whereby said upper end engages said casing at least slightly before said lower end.

5. The structure of claim 4, wherein said sealing means is fixed to said mandrel adjacent the lower end thereof, a second and similar resilient and deformable sealing means surrounding said mandrel and xed thereto adjacent the upper end thereof, said second sealing means being operative in the same manner as said irst named sealing means, and said removable means comprising a single, downwardly removable sleeve surrounding both of said sealing means.

PATRICK A. MCKENNA.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,150,310 Baker Mar. 14, 1939 2,187,482 Baker et al. Jan. 16, 1940 2,189,697 Baker Feb. 6, 1940 2,225,143 Baker et al Dec. 17, 1940 2,325,556 Taylor, Jr. et al. July 27, 1943 2,330,259 Baker Sept. 28, 1943 2,331,532 Bassinger Oct. 12, 1943 2,343,076 Otis et al Feb. 29, 1944 2,427,311 Tarkington Sept. 9, 1947

Images