Note: Descriptions are shown in the official language in which they were submitted.
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1 Docket l~o. 84-012
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8CONTINUOUS FLOW PERFORATION WASEIING TOOL AND ~ETHOD
10BACKGROUND OF TXE INVENTION
11
12The present invention relates generally to well bore
13 equipment used in completion and workover of oil well
14 and/or gas wells. Specifically, the invention relates to
a continuous flow well washing tool and method for
16 circulating fluids through well conduits and into ~t~
17 surrounding formations for formation treatment. ~
18
lg Oil and gas wells are completed by installing a
20 production casing into the hole from the surface and
21 cementing the casing in place. After the production
22 casing is installed, the casing is perforated at the
23 producing depth and the oil and/or gas flows from the
24 surroundîng earthern formation through the casing
25 perforations and up the production casing to the surface~
26 usually through production tubing.
27
28 It is often necessary to treat the earthern
29 formation ~which surrounds the perforated casing to
30 enhance the flow of produce~ fluids. The treatment
31 technique employed generally involves circulating water f
32 or an acid solution through the casing perforations, illtO ~,
33 the formation, and back up~ the casing string. S~lch
34 washing of the formation allows loose sand to be flushed
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1 from the formation or consolidated, the creation of voids2 for improved qravel packin~, and other techniques whereby3 fluid flow is improved in tight formations.
Various well washing tools are known in the art for
6 packing of an area of the casing to allow fluid
7 circulation, Such tools are usually lowered into the
8 well bore on a tubing string at which point packers seal
9 off the casing above and below the formation
perforations, after which circulation of treating fluid
11 is commenced. The treating fluid is usually circulated
12 down the string supporting the wash tool, through the
13 tool and out between the packers, and out the casing
14 perforations into the formation. -Flow then continues
back into the casing ~hrough perforations above the
16 pac~kers allowing the returning fluid to flow upwaxdly
17 through the casing above the wash tool.
18
19 Certaln of the prior art wash tools were of th~ cup
type packer arrangement. Cup type packers have been
21 known to fail to ade~uately seal under conditions
22 encountered in the well bore. Also, since the cup type
23 packers engage the casing while the tool is being run
~4 into the well or pulled out of the well, they are
sometimes torn or damaged during use.
26
27 , One prior art wash tool included a tubular mandrel
28 with packer asser~lies carried on the mandrel at opposite
29 ends thereof and an outer tubular body surrounding the
mandrel between the pac~er- assemblies. An annular
31 chamber provided between the mandrel and the surrounding
32 tubular body was in ~luid communication with the mandrel
33 interior through ports in the walls of the mandrcl. Thc
3~ tubular body was provided with ports which permitted
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1 fluid communication between the annular chamber and the
2 exterior of the tool when a valve assembly carried in the
3 annular chamber was actuated in response to a
4 predetermined pressure increase. The packer assemblies
S were first set and then the valve assembly was actuated
6 to provide fluid communication necessary for circulating
7 fluids through the tool for washing the surrounding
8 formationO The valving arrangemcnt was not always
9 reliable due t.o the presence o sand and other
contaminants in the fluid being circulated through the
11 vàlve.
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1 SUM~RY OF T~IE I~VF.NTION ~,
3 The continuous flow perforation washing tool of the
4 invention has a tubular mandrel having exterior sidewalls
and an interior flow passage, an upper end adapted to be
6 connected in a pipe string extending to the well surface,
7 and a lower end with means adapted to b]ock the flow of
8 fluid from the pipe string through the man~rel flow
9 passage~ Upper and lower packer assemblies are carried
on the mandrel at vpposite ends thereof, each of the
11 packer assemblies including an elastomeric seal ring.
12
13 An outer setting sleeve surrounds the mandrel
14 between the packer assemblies and defines an annular -
cha~ber between the mandrel and the setting sleeve. The
16 annular chamber is in continuous fluid communciation with
17 the mandrel 10w passage through port means provided in
18 the sidewalls of the mandrel.
19
The outer setting sleeve is connected to a first
21 seal body at one end thereof which is slidably received
22 on the mandrel exterior. Preferably the seal body has an
23 outer recess for receiving one of the elastomeric seal
24 rings and includes a face re~ion abutting an end of the
~5 seal ring and ~a sleqve portion which contacts the
26 interior of the seal ring. A second seal body has an
27 annular seal portion slidably received between the
28 mandrel exterior and the end of the se~ting sleeve
29 opposite the first seal body. The second seal bvdy
preerably has an outer recess for receiving the other of
31 the elastomeric seal rings and includes a face region
32 abutting an end of the second seal ring and a sleeve
33 portion which contacts the interior of the second seal
34 ring.
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l A plurality of selectively sized ori~ices
2 communicate the annular chamber ~.~ith the well bore to
3 provide controlled flow of fluid to the well bore whereby
4 fluid pressure communicated by the port means in the
mandrel to the annular chamber acts on the first and
6 second seal bodies to seal the elastomeric seal rings in
7 the well bore.
9 The selectively sized orifices form a restriction in
a portion of the continuous flow passage through the
11 tool, mandrel portsJ annular chamber, and orifices. The
12 restriction causes a back pressure buildup in the annular
13 chan~er which sets the packer assemblies as fluid i5
14 continuously flowed through the continuous flow passage.
16 In the method for circulating fluid in a well having
17 a perforated casing, a wash tool is attached to the lower
18 end of a pipe string. The wash tool has ~n inrlcr mandr~l
19 with a flow passage there~hrough communicating with the
pipe string. Pressure responsive packer assemblies are
21 provided at opposite ends of the mandrel and a setting
22 sleeve surrounds the mandrel between the packer
23 assemblies to define an annular chamber. Ports
24 communicate the mandrel interior with the annular chamber
~5 and selectively sized orifices communicat~e the annular
26 chamber with the well bore. -
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28 The wash tool is lowered on the pipe string to the
29 desired circulation level wi~hin the perforated casing.
Closure means are then actuated to close the lower end of
31 the mandrel flow passage. Fluid is then pumped through
32 the pipe string to the closed mandrel flow passage,
33 through the ports in the mandrel to the annular chamber,
34 and continuously through the sized orifices in the
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1 setting sleeve to the well bore. The nu~er and size of
2 the orifices are selected to provide a controlled flow of
3 fluid through the orifices to create a back pressure in
4 the annular chamber and thereby hydraulically actuate the
packer assen~lies.
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7 The circulation of fluid is continued from the
8 sur~ace tllrough the pipe string, mandrel, annular chamber
9 and orifices, and through the perforations in the casing
between the packer assemblies into the zon~ surrounding
11 the casing. The fluid is circulated from the formation
12 through perforations in the casing above the packer
13 assemblies and back to the surface of the well through
14 the annulus between the pipe string and the casing.
16 Additional features, objects, and advantages will ~e
17 apparent in the written description which follows.
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BRIEF DESCRIPTION O_ THE DI7~,~INGS
3 Fig. 1. i.s a side partial cross-sectional view of
4 the wash tool of the invention showing the packer
S assemblies in the relaxed state.
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7 Fig. 2 is a side partial cross-sectional view of the
8 wash tool of the invention similar to Fig. 1 showing the
g packers in the set position in a well bore.
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1 DETAILED DESCRIPTION_OF TE~E -rNvE~3TIoN
3 Turning to Fig. l, there is sllown a continuous flow
4 perforation washing tool of the invention designated
generally as 11. The washing tool 11 includes a mandrel
6- 13 having an upper externally threaded end 15 adapted to
7 be connec~ed in a pipe string Inot shown) extending to
8 the well surface, and a lower externally threaded end 17.
9 ~andrel 13 has exterior sidewalls 18 and an internal bore
19 which communicates with the pipe string running to the
11 surface when the wash tool 11 is made up in the pipe
12 string. The lower end 17 of the wash tool 11 is
13 connected to a bottom sub 12 with means adapted to block
14 the flow of fluid from the pipe string through the
mandrel flow passage at the lower-end 17. Such means can
16 comprise, for example, a ball catching sub adapted to
17 receive a ball (20 in Fig. 2) dropped through the pipe
18 string and through the internal bore l9 of the wash tool
19 which seats in the catcher sub in the known manner to
block off the flow of fluid.
21
22 As shown in Fig. 1, a port means comprising at l~ast
23 one opening 21 is provided in the mandrel in the
2~ approximate mid region thereof. l'he mandrel c~:terior
also has a threaded surfaice 23 for thr~adedly engaging an
26 upper header ring 25. Header rin~ 25 has a threaded
27 ex~erior surface 27 or receiving a gage ring 29 on the
28 exterior thereof. The internal diameter of the upper
2~ header ring 25 increases from the upper end thereof
forming a clearance 33 between the headcr ring and
31 mandrel exterior 18 and defining a shoulder 31 in thc
32 ring intcrior. An upper slceve portiorl 35 of an upper
33 seal body 37 is slidably received within the clearance 33
34 of the upper header ring 25. The upper seal body 37 is
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1 of a greater diameter than upper sleeve portion 35 and
2 forms a fluid seal with the mandrel exterior 18 by means
3 of an O-ring 39. A shoulder 41 formed in the mandrel
~ exterior 18 provides a lower stop for the seal body 37.
The external surface of seal body 37 has threads 47 for
6~ threadedly engaging a gage ring 49 similar to ring 29.
7 The smaIler relative diameter of upper sleeve portion
8 35 of upper seal body 37 forms a recess 45 in seal body '~
9 37 for receiving an elastomeric seal ring 46. The recess s
10 45 in upper seal body 37 includes a face region 43 formed
11 by seal body 37 and gage ring 49 which abuts the lowcr
12 end of the elastomeric seal 46. The lower end 26 of
13 upper header ring 25 and gage ring 29 together comprise a
14 second face region 44 for abutting the upper ~nd of the
15 elastomeric seal 46. Upper sleeve portion 35 of seal
16 body 37 contacts the interior of the seal ring 46.
17 Elastomeric seal ring 46, upper header ring 25 and seal
18 body 37 comprise an upper packer assembly.
19
20 A setting sleeve 53 surrounds the mandrel 13 between ``
21 the upper packer assembly and a lower packer assembly
22 which will be presently described and includes an upper
23 portion 51 which is internally threaded to matingly
24 engage the externally threaded surface 47 of upper scal q
25 body 37. Outer setting sleeve 53 is supported between
26 the packer assembli~s to define an annular pressure
27 chan~er 57. ~s seen in Fig. 1, chamber 57 is in
28 continuous fluid communication with the mandrel flow
29 passage 19 through port means 21 provided in the
30 sidewalls of the mandrel. -The setting sleeve 53 is
31 provided with at least one sized orifice 55 which
32 communicates the annular chamber 57 with the surrounding
33 well bore.
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1 The mandrel interior flow passage 19, ports 21 in
2 the mandrel sidewalls, annular pressure chamber 57, and
3 selectively sized orifices 55 together comprise a
4 continuous flow passage from the pipe string through the
5: tool to the well bore.
7 A lower seal body 69 is slidably received on the
8 lower mandrel exterior 59 and sealingly engages the
g mandrel exterior by means of an O-ring 65. An annular
10 seal portion 61 of lower seal body 69 is received between
11 the mandrel exterior 59 and the lower end 54 of setting
12 sleeve 53 and sealingly engages the setting sleeve 53 by
13 means of an O-ring 63. A shoulder 67 formed in the
1~: mandrel exterior provides a stop at one end of the path
15 of travel for annular seal portion 61. Lower seal body
16 69 has an externally threaded surface 71 adapted to
17 receive a gage ring 73 similar to rings 29 and 49.
18 Lower seal body 69 also includes a lower sleeve
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19 portion 75 carried on the mandrel exterior which toge~her
20 with seal body 69 and gage ring 73 forms a recess 87 for
21 recelving a second elastomeric seal ring 85. The lowcr
22 end of the mandrel 13 is provided with external tllreads
23 77 adapted to threadedly engage a lower header ring 79
24 similar to ring 25. Header ring 79 has a region of
25 greater internal diameter which forms a clearance 76 with 3
26 respect to the mandrel exterior 18 for slidably receiving
27 the lower sleeve portion 75 of lower seal body 69. Lower
28 header ring 79 has a threaded exterior surface 81 adapted
29 to receive a gage xing 83. Lower seal body 69 and gage
30 ring 73 form a face region 83 which abuts the upper end
31 of elastomeric seal 85. The opposite end of elastomeric
32 seal 85 abuts a similar face region 91 formed by lower
33 header rings 7g and gage ring 83. Clearances 33 arld 76
34 are vented to the well bore as by opening 93, 95. Lower
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1 header ring 79 has a threaded exterior surface 81 adapted
2 to receive a gage ring 83.
4 - The operation of the perforation wash tool of the
invention will now be described in greater detail. The
6- wash tool is first attached to the lower end of a pipe
7 string and lowered on the pipe string to the desired iJ
8 circulation level within the perforated casing. In the
9 running-in condition, the elastomeric seal rings 45, 85
10 are in the relaxed condition shown in Fig. 1. Once the
11 tool has been run to the selected depth, the closure
12 means are actuated to close the lower end of the mandrel
13 flow passage, as by dropping â ball 20 to a ball catching
14 sub (see Fig. 2) located b~low the lower end 17 of the
15 tool 11. Fluid is then pumped through the pipe string
16 from the surface to the closed mandrel flow passage 19
17 and through the port means 21 in the m~ndrel to the
18 annular chamber S7. Fluid flows continuously through the
19 selectively sized orifices 5$ in the setting sleeve 53 to
20 the surrounding well bore 101.
21 ,
22 The number and sizes of the orifices 55 are selected
23 to provide a controlled flow of fluid through the
24 orifices 55 to create a back pressure in the annular
~5 chamber 57 to thereby hydraulically actuate the pressure 3
26 responsi~e packer assemblies. Back pressure in chamber
27 57 causes upper and lower seal bodies 37, 69 to move in
28 opposite directions in the manner of fluid pistons
29 ther~by causing the elastomeric seals 46, 85 to be
30 compressed outwardly between the face regions 43, 44 and G
31 89, 91, respectively. As long as fluid pressure is
32 provided through the pipe string to the tool, the packer
33 assemblies will remain in the sealed condition shown in
34 Fi~. 2. The selectively sized orifices 55 comprise
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1restriction means in a portion of the continuous flow
2passage of the tool which cause a back pressure buildup
3in the annular chamber 57 to set the packer assemblies as
4fluid continuously flows through the continuous flow
5passage.
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7The circulation of fluid is ccntinued from the
8surface through the pipe string, mandrel 13, a~nular
9chamber 57, and orifices 55, through the perforations 1~3
in the casing between the packer assemblies and through
11 the zone 97 surrounding the casing 39. Circulation is
12 continued through the perforations 105 in the casing
13 above the packer assemblies and back to the surface of
14 the well through the annulus 101 between the pipe string
and the casing 99.
16
17 The amount of pressure buildup inside chamber 57 is
18 determined by the size and number `of ports 21 in mandrel
19 13 and orifices 55 in setting sleeve 53. Thus, the
diameters of the orifices 55 provided in sleeve 53 can be
21 selectively smaller than the diameters of the ports ~1 in
22 the mandrel 13 by a predetermined amount, the ratios of
23 the diameters being selected to control the buildup of
24 back pressure in the annular chamber. Alternati.vely, the
number of orifices 55 provided in the setting sleeve 53
26 can be greater than the number of ports in the inner
27 mandrel by a predetermined amount, the ratio of the
28 number of orifices 55 to ports 21 being selected to
29 control the buildup of back pressure in the annular
chamber 57.
31
32 The following examples are exemplary of the
33 invention for a wash tool having a mandrel with 4 7/8
34 inch diameter ports therein:
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1 Diameter of
2 Casing Si7eNo. of Orifices Orifices
4 3~ 4 .~33~
6- 5~ 1/8 3
7 7 6 1/8
8 7 5/~ 4 1/8 ',
9 9 5/8 ~ 1/8 E
11 As a typical example, a tool designed for a 7 inch
12 casing is ~enerally run on a 2~ inch tubing pipe s~ring
13 to the desired location in the well bore. The packer
14 assemblies can be set at the desired location by
lS providing approximately 500-750 psi prescure ~rom the
16 surf2ce to provide approximately four barrels per minute
17 of treating fluid to wash the perforation.
18 e
19 Once the treatment is compiete, the pressure of
fluid being pumped through the pipe stream can be lowered
21 to unseat the packer assemblies and the tool can be
22 retrieved from the well bore or moved to a different
23 location therein. ';
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An invention has been provided with significant
26 advantages. The continuous flow perforation wash tool of
27 t~he invention can be set at the desired well bore
28 location by merely increasing pump pressure of f]uid
29 being pumped through the pipe stream from the surface.
The absence of valving within the annular chamber
31 simplifies the design and improves reliability. Because
32 there are no movable valve elements within the annular
33 chamber, the presence of sand or other contaminants in
34 the fluid being pumped does not pose a problem. The
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1 design of the upper and lower seal bodies provides l~.
2 greater surface area contact with the elastomeric seals
3 and provides a mechanical advantage in compressing the
4 s~al members during the sealing operation.
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G ~hile the invention has been shown in only one of
7 . its forms, it is not thus limited but is susceptible to
8 various changes and modifications without departing from
9 tho spirit thereof.
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