CA1081614A - Packer cup assembly - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A packer cup assembly useful on tubing at high temperatures and includes a special sealing element having a frangible back up portion to provide pack off in a well.

Description

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The present invention relates to packer cups which are used on tubing positioned in a well to pack off the annular space between the tubing and a well casing or well lines to provide vertical isolation of a portion of such annular space to permit selective placement or removal of fluids lnto or out of formations penetrated by the well. More specifically the present invention relates to a packer cup which is particularly useful on tubing at high temperatures and which includes a special sealing element having a frangible back up portion to provide an adequate pack off for steam operations in a well and to facilitate removal of the tubing from the well should the tubing and packer cup be sanded in during such an operation in the well.
Temperature and radioactive surveys while injecting steam to heat up viscous oil reservoirs have indicated that the steam tends to go into those zones previously treated. Cyclic steam stimulation becomes uneconomic when this occurs repeatedly. Also, the placement of steam in a steam drive , in a thick productive section requires some sort of vertical zonal segregation to make the available thermal energy sufficiently concentrated to be effective.
The use of packer cup assemblies is one way to achieve vertical zonal segregation. However, field evidence indicates that commercially available packer cup assemblies are not holding up under actual well conditions. Tests were made on many commercially available packer cup assemblies. Sealing elements of available packer cup assemblies were found to be not satisfactory.
Further, available packer cup assemblies are not designed to permit easy washover as opposed to milling up if the assemblies become stuck in the hole.

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Initially, it was thought that only a few psi pressure differential would be required to inject steam into a particular zone but this assumption was proven to be in error. A packer cup assembly was wanted which could be easily washed over or could be broken up and left in the bottom of the well.
Most commercially available packer cups have a metal backup thimble which generally has an outside diameter 3/16" to 1/2" less than the inside diameter of the casing. Operators are reluctant to run multiple packer cup assemblies in a well where there is a history of sand production because the cups are often stuck by sand. The packer cup assemblies generally have to be cut and recovered singly or milled up because there is not wash-over clearance with the tight fitting metal backup thimbles. Therefore, there was need for a packer cup assembly which does not require metal backup thimbles or plates.
If backup material is required it has to be made out of something that is frangible. Further, there is need for a packer cup assembly which will withstand reasonable pressure differential encountered at elevated temper-atures and yet have the tubing string strong compared to the packer cup assembly so the tubing can be pulled from the well and the packer cup assembly dropped to the bottom of the well. Alternatively, it is desirable to be able to wash over the packer cup assembly with currently available wash pipe, Thus, this invention provides for a packer cup assembly comprising a mandrel section connectable into a tubing string, a sealing element having a central opening in snug engagement over said mandrel section, said sealing element having a base portion and a face portion including an annularly extending inner lip engaged against said mandrel section and an annularly extending outer lip engageable against a casing stringJ said inner lip and said outer lip being separated by an annularly extending groove portion, a frangible annularly extending backup ring having an outer diameter of less than the outer diameter of said sealing element and a central opening slidably engageable over said mandrel section, said backup ring having a face portion engaged against the base portion of said sealing element and having a relatively flat base portion and stop means on said mandrel section -10~

abutting against the flat base portion of said frangible backup ring to maintain said backup ring in a predetermined position on said mandrel section, said stop means having a maximum radial extension small enough to permit washover if the assembly becomes stuck in a well.
The present invention is directed to a packer cup assembly for use on a tubing string located in a well to seal off the annular space between the outside of the tubing string and the inside of a well liner or casing string. The packer cup assembly includes a mandrel section which is connectable into a tubing string by suitable means such as conventional couplings. A sealing element which has a central opening is snugly fitted - 3a -~, ~
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over the mandrel section. The sealing element has a base portion and a face portion including an annularly extending inner lip engaged against the mandrel section and an annularly extending outer lip engageable against the casing string or well liner. The inner lip and the outer lip are separated by an annularly extending groove portion. A frangible annularly extending backup ring is slidably engaged over the mandrel section. The backup ring has a face portion engaged against the base portion of the sealing element and a relatively flat base portion. The backup ring has a diameter slightly smaller than the diameter of the sealing element. Stop means on the mandrel section abuts against the flat base portion of the frangible backup ring to maintain the backup ring in a predetermined position on the mandrel section.
The stop means have maximum radial dimension of substantially less than the outer diameter of the backup ring to permit washing over. In preferred form the frangible backup ring is formed of furfuryl alcohol filled cordierite which has a compressive strength of about 14,000 to 18,000 psi. The backup ring should have an outer diameter of between l/4 to 3/4 of an inch less than the outer diameter of the sealing element. The stop means is preferably a metal ring having an outer diameter of at least one inch less than the outer diameter of the frangible backup ring and be formed of a material 20 having a compressive strength of at least 50,000 psi.
The present invention is directed to providing a packer cup assembly for use in sealing off the annular space between a tubing string and a well liner or casing which assembly will withstand a hot high pressure environment and which is also easily removed should it and the tubing string become sanded up in the well.

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In drawings wilich illustrate embodiments of the invention;
Figure 1 is a schematic elevation view partially in section and illustrates apparatus assembled in accordance with the present invention position in a well adjacent a well liner.
Figure 2 is an elevation view with portions broken away for , clarity of presentation and illustrates the preferred form of apparatus assembled in accordance with the present invention.
Figure 3 is a sectional view taken at line 3-3 of Figure 2.
Figure 4 is an elevation view with portions broken away for clarity of presentation and illustrates the preferred form of apparatus position in a well and includes a wash pipe being moved into position to wash over the packer cup assembly.
Figure 5 is a partial elevation view and illustrates an alternative embodiment of apparatus assembled in accordance with the present invention.
Figure 6 to Figure 13 inclusive are schematic sectional views illustrating various forms of sealing elements and backup rings which were unsuccessful.
Figure 14 is a schematic sectional view illustrating the sealing element and backup ring of the present invention.
Figure 1 is an elevation view partially in section and illustrates packer cup assemblies generally indicated by the numerals 20 and 21 connected on a tubing string 23 located in a well in accordance with the present invention. The packer cup assemblies 20, 21 are positioned adjacent a portion of the slots in well liner 25. The upper packer cup assembly is looking down to prevent fluids in the tubing 23 - liner 25 annulus 27 from _ 5 --108~

1 going up the well ~hile th2 lower packer cup assembly 21 is 2 looking up to prevent fluids in the annulus 27 from going further

3 down the well. Thus, for example, in a steam injection operation

4 wbere it is desired to inject steam into a particular in~erval the packer cup assemblies 20, 21 are spaced apart on th2 tubing 6 string 23 to bridge the interval and the steam is injected do~n 7 the tubing string 23 and out port 28 into annulus 27 and then 8 forced out into the formation through the slots located in the 9 liner.25 between the packer cup assembles 20, 21. The packer cup assemblies of the present invention are particularly usaful in steam injection operations. However, they also find utility in ~ many other conventional oilfield injection or production 13 operations.
14 FIG. 2 is an elevation view with portions brGken away for clarity of presentation and FIG 3 is a sectional view taken 16 at line 3-3 of FIG. 2. These figures illustrate the preferred 17 pac~er cup assembly of the present invention. The pack~r cup 18 assembly 21 includes a mandrel section 30. The mandrel section 19 30 is connectecl into the tubing string 23 by suitable m~ans such as coupling 32 and coupling 34. A sealing element 36 h~ving a 21 central opening fits in snug engagement over the mandrel section 22 30. The sealing element has a flat base portion 37 and a face 23 portion including an annularly extending inner llp 39 engaged 24 against the ~andrel section 30 and an annularly extending outer lip 40 engaged against the liner or casing string. The inner lip 26 39 and the outer lip 40 are separated by an annularly eYtenaing 27 groove portion in the sealing element 36. The lip portions are 28 important to prevent fluid bypass of the sealing element.
29 A frangible annularly extending backup ring 42 is positioned behînd the sealing element 36. The backup ring has a 31 diameter slightly smaller than the sealing element to s~pport the .. .

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1 sealing ele~ent during hiyh pressure operations. Preferably, the 2 outer diameter of the backup ring is between 1/4 to 3/4 of an 3 inch less than the outer diameter of the sealing element. The 4 central opening of the backup ring slidably engages over the mandrel section 30. The backup ring has a face portion eng~ged 6 against the base portion of the sealing element and has a 7 relatively flat base portion. The material forming said 8 frangible backup ring should have a compressive strength of more 9 than 5,000 psi and less than 20,000 psi. Tha preferred material for forming the frangible backup ring is furfuryl alcohol filled cordierite. Stop means are provided on the mar.drel section 12 abutting against the flat base portion of the frangible backup 13 ring to maintain the backup ring in a predetermined position on 14 the mandrel section. The stop means should have a maximum radial .dime~sion small enough to permit washover should *he assembly 16 become stuck in the well. Such a suitable dimension is usually 17 at least about one inch less than the outer diameter of the 18 backup ring. ~-ha stop means is preferably formed of a material 19 having a tensile strength in excess of 50,000 psi. Thus, a metal ring 44 abuts against the flat base portion of the frangible 21 backup ring 42. A jam nut collar 46 is threadably engaged on the 22 mandrel section 30 and follows the metal ring 44 to maintain the 23 sealing element 36 and the frangible backup ring 42 in -24 predeterminea position on the mandrel section.
PIG. 4 is an elevation viev with portio~s broken ~way 26 for clarity of presentation and illustrates the preferred packer 27 cup assembly positioned in a well and includes a wash pipe 50 28 being moved into position to wash over the packer cup assembly 29 if, for example, the tubing string should become stuck in the hole due to sanding up the packer cup assembly. Thus, washover 31 pipe 50 is forced dovn over the sealing element 36 and breaks the ~. .

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1 frangible backup ring 42. The wash pipe 50 is of suffi-ient 2 inside diameter to clear the metallic ring 44 and jam nut collar 3 46. Fluid such as foam is circulated do~n the washover pipe 50 4 and up ~he ~ash pipe S0 - liner 25 annulus to remove sa~d from the well to free the tubing s~ring.
6 FIG. 5 illustrates an alternative embodiment ~f 7 apparatus assembled in accordance with the present invention. In B some instances i~ has been found desirable to eliminate the 9 possibility of the sealing element 36 from slipping up over connector 53 as the tubing string is being run into the vell.
This is accomplished by means of a hold down clamp 51 which is 12 fixedly secured to the tubing string and engages into the 13 annularly extending groove in the sealing member between th~
14 inner lip 39 and the outer lip 40.
A number of sealing element and backup ring configura-16 tions were tested under various conditions of pressure and 17 temperature in a test facility. FIGS. 6-13 schematically 18 illustra'ce arrangements which were found not satisfactocy. Thus, 19 the configuration of FIG. 6 leaked at the casing with 1 psi pressure in the tubing-casing an~ulus. The FIG. 7 configur~tion, 21 without an inner lip, held no pressure and leaked ~ut the tubing.
22 The FIG. 8 configuration where the rubber sealing element was 65-23 70 shore hardness slipped over the backup ring at 200 psi. The 24 PIG. 9 arrangement where an upper rubb~r sealing element having a 65-70 shore hardness was backed up by a rubber element of 9S
26 shore hardness slipped over the backup ring at 475 psi. The 27 configuration of FIG. 10 leaked at the casing at 200 psi when a 28 65-70 shore hardness sealing element was used. A 95 shore 29 hardness element leaked at the casing at 245 psi. The FIG. 11 arrangement with an ele~ent having a shore hardness of 95 leaked 31 at the casing at 250 psi. The FIG. 12 arrangement hel~ 800 psi ~ f ~8~

1 in the lab test, howeYer, failed at 175 psi in a field test. It 2 is believed that the aluminum backup ring failed. The FIG. 13 3 embodiment lea~ed at the casing at 50 psi.
4 The FI5. 14 embodiment in accordance with the preseni invention operated successfully during a six-day test at 800 psi 6 and 520F. Thus the physical configuration of the sealing 7 element and the frangible backup ring of FIG. 14 showed superior 8 results. A number of demonstrations were conducted with 9 diffeEent sealing elements made from different mater~al to select a suitable material for high temperature operations. A small 11- pressure vessel was i~stalled on a steam injection well, where 12 material samples could be placed and steam flowed ~ver them under 13 actual ~ell conditions. The following rubber materials were 14 tested at 345 to 500 psi pressure and 440 to 475F t~mperatura:
15 . Viton *
16 Polyacr~lic 17 Ethylene propylene (E~DM~
18 Butyl 19 Neoprene Nitrile 21 Hycar*rubber 22 Styrene ~utadiene rubber (SBR) 23 Buna S*
24 Ethylene propylene ~las the only rubber material to hold its resiliency under over an 18 month test period after whi-h the 26 test was terminated. All other materials failed in a steam 27 environment within 48 hours.
28 Three samples of Hycar*rubber, neoprene and ethylene 29 propylene were tested in hot and cold crude oil and in hot and cold solvent. ~he samples placed in ambient temperature crude 31 oil showed no apparent change. After 50 hours of hot (1~5F) and 32 64 hours of ambient temperature (114 hours total), the ethylene 33 propylene showed 10~ swelling with good stretch return. The 34 Neoprene showed slight swelling and softening but excellent stretch return. The Hycar*rubber showed no effects whatsoever.
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1 However, after 72 hours (8 hours hot ~165F3 and 64 hours ambient 2 temperature), in the solvent the ethylene propylene sample showed 3 25% swelling with complete loss in stretch return. The Nsoprene 4 sample also showed 25~ swelling but did not lose as much stretch return or strength. The Hycar rubber sample was only slightly 6 softened with ~o swelling or serious loss or strength.
7 The demo~strations and physical configurations test 8 indicated that e~hylene propylene is the only rubber material 9 teste~ that does not get hard and brittle in a steam environment.
Its performance in cold crude oil is acceptable. It should 11- probably not be based in hot crude oil and definitely no. in high 12 aromatic solvents. It will not bond to metal. Hycar r~bber and 13 Neoprene have good to excellent resistance to hydrocarbons but 14 perform very poorly in steam. These materials easily bond to .metal. The rubber sealing element in a packer cup assembly tends 16 to "cold-flow" when its backup plate outside diameter is 1/2"
17 smaller than the inside diameter of the casing. The se~ling 18 element of a packer cup assembly that is unsupported tends to 19 fail on its internal seal or bond. All commercially available packer cup assemblies failed to hold pressure at elevated 21 temperatures. ~he sealing element of pac~er cup of the present 22 invention held pressure at elevated temperatures. The large mass 23 of rubber in the present sealing element allows a certain amount 24 of cold and hot flow with sufficient rubber material left to still form a seal. The packer cup assembly of the pres2nt 26 invention with the frangible backup ring is the only packer 27 assembly that is effective in steam service and can be "washed 28 over".
29 Various materials were tested in a search to discover a suitable material for use as the frangible backup riny of the 31 present invention. A small pressure vessel was installed on a - ~ \

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1 steam injection ~ell, where material samples were placed and 2 steam f~o~ed over them under actual well conditions.
3 The following materials were tested at 450F to 475F
4 temperature and 575 to 650 psi pressure:
Cordierite 6 Pyrex *
7 Furfuryl alcohol 8 Various fiberglass compounds 9 Various polylite compounds Various polyester compounds 11 Polyethylene molding material 12 Casting resins 13 Styrene and asbestos mixtures 14 Cordierite, pyre~*and furfuryl alcohol resins ~ere the 15- only materials that ~ere competent after being in this 16 ~nvironment for seven days. The cordierite surface ten~ed to 17 soften up ~hen i~ wet steam which resulted in poor wear 18 characteristics. Ho~ever, when the cordierite was filled with 19 .polymerized furfuryl alcohol, the wear characteristics ~nd compressive strength were improved. Subsequent tests with pyrex 21 indicated that it fractured easily and was very expensive to get 22 in specialty sizes. It has not been possible to cast pure 23 furfuryl alcohol resins without gas bubbles which lowered the 24 compressivs strengt:h to an unacceptable level.
A typica]. chemical analysis of cordierite after being 26 fired is:
27 SiO2 51.4%
23 Al2O3 13.1 29 MgO 34.0 Others 1.5 31 100.0%
32 The ~ollo~ing are the strength and thermal properties 33 of cordierite and other mat~rials:
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1 Compressive Stren~th 2 Unfilled cordierite2,575 to 7,830 psi 3 Purfuryl filled cordierite 14,000 to 18,300 psi 4 Concrete 2,500 psi Structural steel60,000 psi 6 Thermal Condu_tivlty 7 (BTU-in/hour, ft/F~
8 Unfilled cordierite6.4 9 Furfuryl filled cordierite 6.0 Air 0.163 11 Cork board 0.3 12 Steel 300.0 13 Copper, pure 2,616.0 14 The frangible backup rings are formed from polymerized furfuryl alcohol impregnated cordierite. Cordierite is a mixture 16 of dry clays mixed to a dough-liXe consistency with 20~ to 30~ by 17 volume water, extruded or molded to the proper shape, room dried 18 to remove excessive water and fired in a kiln at 2400F for 24 19 hours. Ths lugs are then put into a pan containing furfuryl alcohol containing a suitable catalyst in vacuum to remove air 21 from the lugs to insure complete impregnation of the furfuryl 22 into the lug. The lugs are removed from the pan to drain excess 23 furfuryl. The lugs are put into an oven and the temperature is 24 maintained at 160F to polymerize the furfuryl alcohol in about 40 minutes. A suitable furfuryl alcohol-catalyst system is 26 described in U.S. Patent 3,850,249, issued November 26, 1974, to --27 Patrick H. Hess and assigned to Chevron Research Company, S~n 28 Francisco, California.
29 Although certain specific embodiments have bee~
described in detail herein, the invention is not limited only to 31 those embodiments but rather by the scope of the appended claims.

Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A packer cup assembly comprising a mandrel section connectable into a tubing string, a sealing element having a central opening in snug engagement over said mandrel section, said sealing element having a base portion and a face portion including an annularly extending inner lip engaged against said mandrel section and an annularly extending outer lip engageable against a casing string, said inner lip and said outer lip being separated by an annularly extending groove portion, a frangible annularly extending backup ring having an outer diameter of less than the outer diameter of said sealing element and a central opening slidably engageable over said mandrel section, said backup ring having a face portion engaged against the base portion of said sealing element and having a relatively flat base portion and stop means on said mandrel section abutting against the flat base portion of said frangible backup ring to maintain said backup ring in a predetermined position on said mandrel section, said stop means having a maximum radial extension small enough to permit washover if the assembly becomes stuck in a well.

2. A packer cup assembly comprising a mandrel section connectable into a tubing string, a sealing element having a central opening in snug engagement over said mandrel section, said sealing element having â base portion and a face portion including an annularly extending inner lip engaged against said mandrel section and an annularly extending outer lip engageable against a casing string, said inner lip and said outer lip being separated by an annularly extending groove portion, a frangible annularly extending backup ring having an outer diameter of less than the outer diameter of said sealing element and a central opening slidably engageable over said mandrel section, said backup ring having a face portion engaged against the base portion of said sealing element and having a relatively flat base portion and stop means on said mandrel section abutting against the flat base portion of said frangible backup ring to maintain said backup ring in a predetermined position on said mandrel section, said stop means having maximum radial extension of at least about one inch less than the outer diameter of said backup ring.

3. A packer cup assembly comprising a mandrel section connectable into a tubing string; a resilient sealing element having a central opening in snug engagement over said mandrel section, said sealing element having a base portion and a face portion including an annularly extending inner lip engaged against said mandrel section and an annularly extending outer lip engageable against a casing string, said inner lip and said outer lip being separated by an annularly extending groove portion; a frangible annularly extending backup ring having an outer diameter of between 1/4 to 3/4 of an inch less than the outer diameter of said sealing element and a central opening slidably engageable over said mandrel section, said backup ring having a face portion engaged against the base portion of said sealing element and having a relatively flat base portion, the material forming said frangible backup ring having a compressive strength of between 5,000 and 20,000 psi; and stop means on said mandrel section abutting against the flat base portion of said frangible backup ring to maintain said backup ring in a predetermined position on said mandrel section, said stop means having maximum radial extension of at least about one inch less than the outer diameter of said backup ring and said stop means being formed of a material having a compressive strength in excess of 50,000 psi.

4. The packer cup assembly of Claim 3 further characterized in that said resilient sealing element is formed of ethylene propylene.

5. The packer cup assembly of Claim 3 further characterized in that a hold down clamp is fixedly secured to said tubing string and engages against the face portion of said sealing element to prevent said sealing element from sliding on said mandrel section.

6. The apparatus of Claim 3 where said stop means is a metal ring.