US2681706A - Inflatable well packer - Google Patents

Description

June POTTQRF INFLATABLE WELL PACKER 3 Sheets-Sheet Jl Filed Dec.- 30, 1949 *fiallhlllm June 22,1954 N. POTTORF 2,581,706

INFLATABLE WELL PACKER- Filed Dec. 30, 1949 a Shebts-Sheet a i iq HIHI'IIIH IIH INVENTOR.

Patented June 22, 1954 UNITED. STATES TENT OFFICE lind Oil and Gas Com poration of Delaware pany, Tulsa, Okla, a cor- Application December 30, 1949, Serial No. 135,937

17 Claims. 1

This invention relates to packers for use in wells and is directed particularly to a fluid-expansible packer suitable for use in spaces of varying diameter, such as in the open-hole portion of oil and gas wells.

Packers suitable for use in spaces of known or constant diameter such as well casing have been known and commercially available for many years. However, the problem of providing a suitable packer for use in spaces of varying diameter and with uneven boundary surfaces, such as may occur in the open-hole portion of oil and gas wells, is one which has not been completely and satisfactorily solved for all possible circumstances. The fluid-expansible packers so far proposed have either been seriously limited in the degree of possible expansion or n the diiferential pressures which they will withstand in attempting to seal off irregularities of the bore-hole wall. Heretofore the necessity of making fluid-expansible sleeve packers of small enough diameter to pass freely through a well casing or well bore has so limited the length of rubber included circumferentially around the sleeve as to restrict severely the ultimate diameter to which the packer can be extended.

There is one field of use for fluid-expansible packers in which the withstanding of large differential pressures or sealing against the borehole walls with a high pressure is not important.

In the determination of fluid entry into wells a baffle-type packer, which serves primarily to prevent flow of fluids along the well bore and makes no attempt to seal off against largepressure differentials at difierent levels of the well, is highly useful. However, such packers have not heretofore been used for the one reason, among others, that the expansion of the sleeve is often uneven or of too limited an extent to form an effective seal in a large diameter or irregularly shaped hole.

It is accordingly a primary object of my invention to provide an improved fluid-expansible, lowpressure, sleeve-type packer for use in wells of varying diameter and irregular Wall surface conditions. Another object of the invention is to provide a sleeve-type packer having both a reasonably small collapsed diameter and a large ultimate possible expansion. Still another object is to provide a sleeve-type packer which favors expansion in alateral rather than ina longitudinal direction, thereby increasing the ultimate diameter towhich it may be expanded without overstressing the material of the sleeve. A further objectistoprovide a resilient wellpacker sleeve which expands by an unfolding rather than a stretching of the sleeve rubber, over the major portion or" the sleeve extension. Another and still further object is to provide an expansible sleeve-type packer which will expand uniformly radially in a plane perpendicular to the longitudinal axis of the sleeve. Still another object is to provide a sleeve-packer inflation and deflation mechanism readily controllable from the ground surface at the top of a well. Other and further objects, uses, and advantages of the invention will become apparent as the description proceeds.

Stated in a brief form, the foregoing and other objects of my invention are accomplished by an inflatable packer having a relatively thin, resilient, cylindrical sleeve provided with longitudinal rows of spaced depressions, which leave parallel continuous ridges extending generally in the direction of the sleeve axis, to Contact the borehole walls. The folds or depressions being spaced or non-continuous, at least near the center of the sleeve, due to cross-ridges or intersections of the longitudinal ridges, prevent fluid leakage along the outside of the packer longitudinally between the ridges when the yarn in contact with the well wall.

The depressions of adjacent rows are longitudinally offset, however, in such a way as not to interfere appreciably with the expansibility of the packer sleeve in a lateral direction. Since the expansion of such a packer sleeve is in combination of both unfolding and stretching of the rubher of the sleeve, with the former eiTect predominating over a major portion of the expansion range, the size or diameter of the sleeve increases uniformly rather than irregularly as in the case of a sleeve of the conventional type. In order to insure expansion at the middle of the sleeve before it occurs at the ends, the thickness of the sleeve rubber may be tapered slightly from each end toward the middle. Expansion fluid is perferably provided by utilizing the fluids present in the well bore which are passed through a small pump driven by a reversible electric motor, with the pump pressure developed and the direction of pumping being controlled by the magnitude and direction of electric current flow from the ground surface.

This will be better understood by reference to the accompanying drawings forming a part of this application, in which drawings the same reference numerals are applied to the same or corresponding parts in the different figures. In these drawingsz Figure l is an elevation view of a packer embodying the invention set in a well bore shown in cross section;

Figure 2 is a cross section of the packer and well bore of Figure 1, showing its adaptation to a well fluid-testing device;

Figure 3 shows in cross section a modification of the means for securing the end of the packer sleeve of Figure 2;

Figure 4 is an electrical circuit diagram of an inflation control mechanism for the packer of the invention;

Figure 5 shows a'iurther modification of the invention and its use in a two-packer wellformation tester;

Figures 6 and 7 are, respectively, detailed elevation and cross-sectional views along the line 7-7 of Figure 6 of a portion of a packer sleeve embodying the invention opened up and flattened out; Figures 8 and 9 are, respectively, detailed elevation and cross sectional views along the line 9-9 of Figure 8 of a modified design of packer sleeve;

Figures 10 .and 11 are, respectively, detailed elevation and cross-sectional views along the line ill| of Figure 10 of a further modification of the packer sleeve design;

Figure 12 is a cross-sectional view of the portion of the sleeve of Figure 11 in an extended position; and

Figure 13 shows graphs of the variations of pressure and volume within conventional packer sleeves during expansion, as compared with the packer sleeves of the invention.

Referring now to these drawings and particularly to Figures 1 and 2, a packer designated generally by the numeral is shown in set position in a well bore 21, thus subdividing the well into an upper portion 22 and a lower portion 23.

' contracted by taking well .or other liquid from within tubing 25 through a strainer 33 on the inlet of a sliding-vane or rotary-gear type positive displacement pump 34, driven through a re duction gear 35 by a small reversible electric motor 36, which is supplied with direct-current electric power through a choke coil 31 over an insulated conductor 38 extending to the ground surface. The outlet 39 of pump 34- opens into the enclosure between the outside of tubing 25 and the inside of sleeve 29.

In contrast with most inflatable packers, and substantially all of the compression-setting types, the rubber or this sleeve29 is thin in the sense that 'it is highly flexible and requires only a pounds of difierential fluid pressure, for example, less than ten, to expand it fully. The provision of the reversible-direction pump 34, whereby the difierential pressure inside the sleeve can be made either positive or negative relative to the sur rounding pressure, insures that both the setting and releasing of the sleeve 29.from contact with the well wall will occur as desired.

In a typical application of this packer, the. 7

tubular mandrel 25 is provided with inlet ports M and 42, respectively above and below the packer 2B, which ports allow free passage of fluids through the tubing and thus prevent large differential pressures existing between the spaces 22 and 23. If desired, the fluids entering both or one of the ports such as 42 are first passed through a testing device 43, for example, a fluid-conductivity cell, to measure a fluid characteristic before mixing with other fluids takes place inside the tubing 25. If alternating current is used for measurement purposes, the testing device %3 can be connected through an electrical condenser 44 to the insulated conductor 38.

The ends of the packer sleeve 29 may either be held immovable by fixing the end members 26 and'ZI solidly to tubing 25, or one of these end members may be allowed to slide freely on the tubing 25, as shown in Figure 3, in order to relieve further the longitudinal stretching of the sleeve 29 as it expands outwardly against a well wall. Figure 3 shows a sliding seal for the member 21, provided by a packing gland 46 against the outer surface of the tube 25. A compression spring 4'! inside the sleeve 29 presses against the end member 21 to move it outwardly when the sleeve 29 is to be collapsed.

In Figure d is shown both a packer-control system and fluid-testing system which can be operated from the ground surface over the singleconductor cable 33. This is accomplished by using the earth for the return circuit and direct and alternating current, respectively, for packer control and for fluid testing purposes. Direct current from a battery 49, as adjusted by a rheostat 50 and indicated by an ammeter 5!, passes through a polarity-reversing switch 52 and isolating choke coil 53 over the insulated-conductor cable 38 and through the choke coil 37 to the motor 36. The direction of flow of current as determined by the position of reversing switch 52 determines the direction of rotation of motor 36 which may have a permanent-magnet field, and thus determines whether the sleeve 29 is being inflated or deflated. The torque of motor 36, and thus the differential-pressure developed by pump 34 and applied to the sleeve 2%, is regulated by adjustment of the rheostat 56 to produce a predetermined current flow, as indicated by the ammeter 5|.

Simultaneously indications can be obtained from the testing device 43 through the cable 38 over which alternating-current power or signal energy,-or both, are supplied from an alternatingcurrent generator 55 through an isolating condenser 56 to produce on an indicator 5'! an indication of the response of testing device 43. It will be understood that this control and measuring circuit is only representative of many which packers and communicating with each other through the tubing 25, prevent the occurrence of large pressure diiferentials which would produce leakage past the packer sleeves. It is desirable in this embodiment,as well asin that of Figure 1 utilizing a single packer, to provide the tubing 25 with one or more spring centralizing devices 65 and 66 to center tubing 25 in the well. Centralizers 65 and 66 make it more certain that the centers of sleeves 60 and BI will contact the well wall uniformly around their circumferences.

In Figures 6 and '7 is shown in more detail the design of the packer sleeve 29 illustrated in Figure 1. These figures show the sleeve material as it would appear if a section were cut out and laid flat. As is shown more clearly in Figure 6, the outer surface of the sleeve 29 consists of two sets of helical, substantially parallel ribs or ridges 6B and 69, the two sets intersecting at an acute angle 10 to form longitudinal rows of diamonds-haped depressions H extending generally parallel to the sleeve axis. In order to favor lateral rather than longitudinal expansion, the pitch of the oppositely-sensed helical ridges is at least equal to, and is preferably two to six times the sleeve circumference. This aligns the major dimension of the depressions H with the sleeve axis and gives them a length-to-width ratio of at least one and preferably between 2 and 6. Also the depressions H in adjacent rows are lngitudinally offset, Ha, for example, being exactly opposite the midpoint between depressions lib and 1 la in the adjacent row.

As is more clearly shown in Figure '7, the side walls '52 and 13 of each depression II are of about the same small thickness as the rest of the sleeve, leaving an open space M underneath each ridge or rib 68 or 69. Thus, when pressure is applied inside the sleeve 29, it expands primarily by straightening out the folds of rubber shown in Figure 7, and stretching of the rubber of the sleeve is minimized. Nevertheless, because the sets of ridges 6B and at intersect formin the spaced or closed-off depressions 1|, fluids are positively prevented from traveling longitudinally through the depressions H and thus leaking around the packer. In other words, there is a continuous line of contact, defined by the dotted line AB, shown best in Figure l, where the sleeve 29 initially makes contact completely around the wall of well 2|, as the sleeve expands. Increasing pressure inside the sleeve brings all of the ridges within the zone defined by the lines C and D in Figure 1 into contact with the well wall.

The conditions existing as the volume within the sleeve 29 increases durin its expansion will be better understood by reference to Figure 13. In this figure the graph or curve it shows the expansion conditions of a conventional flat-surfaced rubber sleeve in a manner that will be understood by anyone who has observed the expansion of a toy rubber balloon. Thus, from a volume of V0 at zero pressure, the pressure increases rapidly to a value P1, but the volume increases slowly to the volume V1 which may be, for example, from 30 to 70 per cent of V0. Thereafter a stretching of one portion of the sleeve occurs such as along one side or at one end, wherever the thinnest section of rubber happens to be, and the volume increase goes on at a reduced pressure P2 with successive areas of the sleeve stretching in turn, until the entire sleeve has reached a volume V2, after which further application of pressure increases the volume uniformly with increasing pressure. It is the exception rather than the rule, however, if thelshape of the sleeve remains uniform throughout the volume range from V1 to V2.

On the other hand, the conditions of pressure and volume inside the packer sleeve 29 of the invention are illustrated by the curve TI. Since the volume inside the sleeve can increase almost entirely by unfolding of the rubber rather than by stretching it, the pressure increase is slow and gradual until the pressure P1 is reached at the volume V3, which can be several times as large as V1, and even larger than V2 for a conventional sleeve. Since the slope of the pressurevolume curve ll is nowhere negative in the range from V0 to V3, the expansion and shape of the packer is uniform throughout this range rather than non-uniform as in the case of the conventional sleeve.

In order to be sure that the center portion of sleeve 29 will expand more rapidly than any other, particularly after passing the pressure P1 at volume V3, the sleeve material is preferably tapered slightly in thickness from the ends toward the center of the sleeve, being thinner in the center.

In Flames 8 and 9 is shown a modification of the sleeve design having similar properties to that of Figures 6 and 7. It is thus possible to have the longitudinal ridges 19 extend substantially parallel to the axis of the sleeve as long as the intervening folds between the ridges do not similarly extend continuously. Accordingly, the folds are interrupted by a second perpendicular set of intersecting and spaced cross ridges ill to form parallel rows of spaced rectangular clepressions 8!) whose long dimension is in the direction of the sleeve axis, but along which fluids cannot flow past the packer. By offsetting the cross ridges 8! in adjacent rows of depressions til, the continuous contact line AB is provided while the sleeve material can still preferentially expand in the direction AB rather than perpem dicular to it. Here again a length-to-width ratio for the rectangular depressions substantially greater than one, and preferably between 2 and 5, is desirable.

A still further modification of the longitudinal ridges and folds subdivided into spaced unconnected depressions is shown in Figures 10, 11, and 12. In this modification, the longitudinal. ribs 83 do not intersect as in Figure 6 nor extend straight as in Figure 8 but deviate in a zigzag fashion, as shown in Figure 10. In ross, these longitudinal ridges are parallel to the sleeve axis. Adjacent zigzag ridges preferably alternate in such a way as to make the intervening folds alternately wide and narrow, and the cross ridges 84 are placed at the locations where the fold width is greatest. Accordingly the depressions 85 are almost the op posits of diamond-shaped, being generally rectangular, but are narrower in the center than at the ends.

This construction permits the cross-ridges 34 to have a maximum length so that a maximum of unfolding action can occur before stretching of the rubber in the cross-ridges 84 is required. As can be seen by comparing Figures 11 and 12 where a given section EF of the sleeve material 29 is shown in contracted and expanded conditions, znore than a two-fold expansion can easily occur before any stretching whatsoever is required, with the ridges and depressions of about the relative. proportions shown in the drawing. After all of the unfolding action possible has occurred, it will be understood that a certain amount of stretching of the rubber of the sleeve can still occur before the negative-slope portion of the pressure-volume curve is reached. It is 7 thus not difficult to see that a ratio of V3 to V of 4 or more to 1 can be realized.

While I have described my invention in terms of the foregoing specific embodiments, it is to be understood that numerous modifications of the principle will occur to those skilled in the art. The invention therefore should not be construed as limited to the exact details of the embodiments described, but its scope is to be ascertained from the scope of the appended claims.

I claim:

1. A well packer comprising a mandrel, a resilient sleeve surrounding said mandrel, means for securing and sealing the ends of said sleeve to said mandrel, means for establishing a predetermined differential fluid pressure between the inside of said sleeve and said mandrel relative to the fluid pressure outside of said sleeve, said sleeve being formed with a plurality of hollow external ridges separated by spaced depressions arranged in rows generally parallel to the sleeve axis, with the major dimension of each depression being in the direction of said axis.

2. A well packer comprising a mandrel, a resilient sleeve surrounding said mandrel, means for securing and sealing the ends of said sleeve to said mandrel, means for establishing a predetermined differential fiuid pressure between the inside of said sleeve and said mandrel relative to the fluid pressure outside of said sleeve, said sleeve being formed with hollow external ridges between spaced depressions arranged in longitudinal rows generally parallel to the sleeve axis, with each depression having a length-to- Width ratio substantially greater than one and having its length dimension in the direction of said sleeve axis.

3. A well packer as in claim 2 in which said ratio is between 2 and 6.

4. A well packer comprising a mandrel, a thin resilient cylindrical sleeve surrounding said mandrel, means for securing and sealing the ends of said sleeve to said mandrel, means for establishspaced depressions generally parallel to the sleeve axis, the depressions of each row being longitudinally offset relative to the depressions in the adjacent rows.

11. A resilient well-packer sleeve having two sets of hollow external helical ridges of opposite sense intersecting at an angle to form longitudinal rows of diamond-shaped depressions having a length-to-width ratio substantially greater than one, with the length dimension extending generally in the direction of the sleeve axis.

12. A resilient well-packer sleeve having a first set of hollow external helical ridges extending around said sleeve in a right-hand sense, a second set of hollow external helical ridges intersecting said first set and extending around said sleeve in a left-hand sense, the pitch of the helices being substantially equal and at least as great as the circumference of said sleeve.

13. A resilient well-packer sleeve having a first set of hollow external longitudinal ridges extending generally parallel to the sleeve axis, and a second set of hollow external ridges at right angles to and intersecting said first set at spaced points such that the folds between the ridges of said first set are subdivided into spaced depressicns having a length-to-width ratio substantially greater than one, the ridges of said second set in ing a predetermined difierential fluid pressure between the inside of said sleeve and said mandrel relative to the fluid pressure outside of said sleeve, said sleeve being formed with hollow external ridges between spaced depressions arranged in longitudinal rows generally parallel to the sleeve axis, each depression having a length-to- Width ratio substantially greater than one, with the length dimension being in the direction of said axis, and the depressions in each row being longitudinally offset relative to the depressions in the adjacent rows. V

5. A well packer as in claim 4' in which said depressions are diamond-shaped.

6. A well packer as in claim 4 in which said depressions are rectangular.

' the center.

9. A well packer according to claim 4 in which at least one of said means for securing and sealing ends of said sleeve to said mandrel is slidab le'longitudinally along said mandrel.

10. A resilient well-packer sleeve having hollow external ridges between longitudinal rows of adjacent folds being longitudinally offset by about one-half of the spacing of said second set of ridges.

14. A resilient well-packer sleeve having a plurality of hollow external longitudinal alternating zigzag ridges extending generally in the direction of the sleeve axis, and leaving folds of varying width between adjacent ridges, and a plurality of hollow external cross ridges extending across each of said folds between said longitudinal ridges at the locations where said folds are widest.

15. A resilient well-packer sleeve having hollow external longitudinal zigzag ridges and cross ridges between said longitudinal ridges forming longitudinal rows of spaced depressions, each depression being of generally rectangular form but being narrower in the center than at the ends, and the depressions of adjacent rows being longitudinally offset. 7

16. A resilient well-packer sleeve having a plurality of generally longitudinal folds forming internally hollow, externally projecting ridges, with depressions between and spaced apart by said ridges, the length-to-width ratio ofsaid de pressions being substantially greater than one.

17. A well-packer sleeve as in claim 16 in which said ratio is between 2 and 6.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 171,589 Stewart Dec. 28, 1875 250,929 Lewis Dec. 13, 1881 666,541 'Moser Jan. 22, 1981 1,476,554 Swanson Dec. 4, 1923 1,934,547 Little Nov. 7, 1933 2,027,290 Reach Jan. 7, 1936 2,222,846 Johnston Nov. 26, 1940 2,248,169 Granger July 8, 1941 2,313,762 Midgett Mar. 16,1943 2,441,894 Mennecier May 18, 1948 2,452,466 Jaswell Oct. 26, 1948 2,552,433 Kirby May 8, 1951. 2,589,332 Brown Mar. 18, 1952

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