CA1202557A - Continuous flow perforation washing tool and method - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A continuous flow well bore perforation washing tool is shown of the type having a tubular mandrel with sidewalls defining a flow passage, an upper end for connection in a pipe string and a lower end with means for blocking the flow of fluid from the pipe string through the mandrel. Upper and lower pressure responsive packer assemblies are carried on opposite ends of the mandrel. An outer setting sleeve surrounds the mandrel between the packer assemblies to define an annular chamber between the mandrel and setting sleeve. A
continuous flow passage communicates the mandrel interior, the annular chamber, and the well bore.
Selectively sized orifices in the setting sleeve form a restriction in a portion of the continuous flow passage.
By selectively sizing the orifices, a back pressure buildup can be created in the annular chamber which is used to set the packer assemblies as fluid is continuously flowed through the continuous flow passage.

Description

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~i 1 Docket l~o. 84-012 ,, !~

8CONTINUOUS FLOW PERFORATION WASEIING TOOL AND ~ETHOD

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. ~

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.

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 ~' ' ~ ~ j ~2~25~
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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.

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.

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 1~ S 5i 7 F
-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.

.~ 2~.it7 ' 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.

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.

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.

k ~ ;)2557 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. -~7 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 . ~ ~ 7 ~"` ````` .3L~S5~ ` ~

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.

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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1.

~ lD255 7 r 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.
- ;6 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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' ~k, S~'7 ,, , 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.

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.

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 .
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 120Z55'~ ~

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 ~Q~55~

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.
t 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.

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.

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 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. ';
2~
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 ~ llZ5S~

14 r 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.
~.
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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Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a well bore perforation wash tool of the type having a tubular mandrel with sidewalls defining a flow passage, an upper end for connection in a pipe string and a lower end with means for blocking the flow of fluid from the pipe string through the mandrel, upper and lower pressure responsive, solid, compressible packer assemblies carried on opposite ends of the mandrel, and an outer setting sleeve surrounding the mandrel between the packer assemblies to define an annular chamber between the mandrel and setting sleeve, the improvement comprising:
a continuous flow passage communicating said mandrel interior, said annular chamber and said well bore prior to and after setting said packer assemblies, said continuous flow passage comprising port means in said mandrel sidewalls communicating said mandrel flow passage and said annular chamber and orifice means in said outer setting sleeve for communicating said annular chamber and said well bore; and wherein said port means and said orifice means are selectively sized to cause a predetermined back pressure buildup in said annular chamber to set said packer assemblies as fluid is continuously flowed through said continuous flow passage.

2. The well bore perforation wash tool of claim 1, wherein said restriction means is defined by the size and number of said orifices in said setting sleeve relative to said port means in said mandrel.

3. A continuous flow perforation washing tool for use in a well bore comprising:
a tubular mandrel having exterior sidewalls and an interior flow passage, an upper end adapted to be connected in a pipe string exending to the well surface, and a lower end with means adapted to block the flow of fluids from said pipe string through said mandrel flow passage;
upper and lower packer assemblies carried on said mandrel at opposite ends thereof, each of said packer assemblies including a solid, compressible elastomeric seal ring;
an outer setting sleeve surrounding said mandrel between said packer assemblies defining an annular chamber between said mandrel and said setting sleeve, said annular chamber being in continuous fluid communication with said mandrel flow passage through port means provided in the sidewalls of said mandrel and with said well bore through orifice means provided in said setting sleeve, prior to and after setting said packer assemblies;
said outer setting sleeve being connected to a first seal body at one end thereof which is slidably received on said mandrel exterior, said seal body having an outer recess for receiving one of said elastomeric seal rings; and a second seal body having an annular seal portion slidably received between said mandrel exterior and the end of said setting sleeve opposite said first seal body, said second seal body having an outer recess for receiving said other of said elastomeric seal rings, each of said recesses including a face region abutting an end of its associated seal ring and a sleeve portion which contacts the interior of its associated seal ring whereby sliding movement of said setting sleeves compresses said seal rings to set said packer assemblies.

4. A continuous flow perforation washing tool for use in a well bore comprising:
a tubular mandrel having exterior sidewalls and an interior flow passage, an upper end adapted to be con-nected in a pipe string extending to the well surface, and a lower end with a ball catching sub adapted to catch a ball dropped from the surface to thereby block the flow of fluids from said pipe string through said mandrel flow passage;

upper and lower packer assemblies carried on said mandrel at opposite ends thereof, each of said packer assemblies including a solid, compressible elastomeric seal ring;
an outer setting sleeve surrounding said mandrel between said packer assemblies defining an annular chamber between said mandrel and said setting sleeve, said annular chamber being in continuous fluid communication with said mandrel flow passage through port means provided in the side-walls of said mandrel and with said well bore through orifice means provided in said setting sleeve, prior to and after setting said packer assemblies;
said outer setting sleeve being connected to a first seal body at one end thereof which is slidably received on said mandrel exterior, said seal body having an outer recess for receiving one of said elastomeric seal rings;
a second seal body having an annular seal portion slidably received between said mandrel exterior and the end of said setting sleeve opposite said first seal body, said second seal body having an outer recess for receiving said other of said elastomeric seal rings, each of said recesses including a face region abutting an end of its associated seal ring and a sleeve portion which contacts the interior of its associated seal ring whereby sliding movement of said setting sleeves compresses said seal rings to set said packer assemblies; and said orifice means being selectively sized to provide controlled flow to said well bore whereby fluid pressure communicated by said port means in said mandrel to said annular chamber acts on said first and second seal bodies to seal said elastomeric seal rings in said well bore.

5. A method for circulating fluid in a well having a perforated casing, comprising the steps of:
attaching a wash tool to the lower end of a pipe string, the wash tool having an inner mandrel with a flow passage therethrough communicating with said pipe string, pressure responsive, solid compressible packer assemblies at opposite ends thereof, a setting sleeve surrounding the mandrel between the packer assemblies to define an annular chamber between the mandrel and setting sleeve, port means communicating the mandrel interior with the annular chamber, and selectively sized orifices in said setting sleeve communicating the annular chamber with the well bore prior to and after setting said packer assemblies;
lowering the wash tool on the pipe string to the desired circulation level within said perforated casing;
actuating closure means to close the lower end of said mandrel flow passage;
pumping fluid through said pipe string to said closed mandrel flow passage, through said port means in said mandrel to said annular chamber, and continuously through said sized orifices in said setting sleeve to said well bore, the number and size of said orifices being selected to provide a controlled flow of fluid through said orifices to create a back pressure in said annular chamber and thereby hydrau-lically actuate said packer assemblies; and continuing to circulate fluid through said pipe string, mandrel, annular chamber and orifices, through perforations in said casing between said packer assemblies, through the zone surrounding said casing, through perforations in said casing above said packer assemblies and back to the surface of said well through the annulus between said pipe string and said casing.

6. The method of claim 5, wherein the diameters of said orifices provided in said setting sleeve are smaller than the diameters of said port means in said mandrel by a predetermined amount, the ratio of said diameters being selected to control the buildup of back pressure in said annular chamber.

7. The method of claim 5, wherein the number of orifices provided in said setting sleeve is greater than the number of port means in said inner mandrel by a pre-determined amount, the number of orifices to port means being selected to control the buildup of back pressure in said annular chamber.

8. The method of claim 5, further comprising the step of lowering the pressure of fluid being pumped through said pipe string to unseat said packer assemblies, said fluid being continually flowed through said orifices in said setting sleeve and into said well bore.