CA1304626C

CA1304626C - Polish rod centralizer

Info

Publication number: CA1304626C
Application number: CA000533127A
Authority: CA
Inventors: Joseph Rezewski
Original assignee: RED WING TOOL CO. LTD.
Current assignee: RED WING TOOL CO Ltd
Priority date: 1987-03-27
Filing date: 1987-03-27
Publication date: 1992-07-07
Anticipated expiration: 2009-07-07

Abstract

ABSTRACT
A centralizer for guiding a pump rod through a well head consisting of a body, a roller guide within the body which can guide a pump rod along a path which is aligned with the axis of the well head, a cap screwed into the body to retain the roller-guide in place, a screw threaded aperture through the wall of the body, a lower stuffing box below the roller guide and a cylindrical retainer for retaining and compressing packing within the stuffing box.

Description

~ 3~
This invention rel~tes ~o ~n irnproved yoli~h rod centralizer whlch guides the polish rod or pump rod ln a well head mlnimizin~ wear on the pump rod and wear in a conventional oil well stuffing box.
In oil retrieval from deep wells, it i~ normal to pump the oil from the ~round by utilizing a reciprocating pump which i~ driven by n mechanlsm on the surface throu~h a pump rod which extends from the operatinK mechanism down into the well through a well caslng. The oil i6 lifted up through the casing by the reciprocating pump to be pumped to a gtorage facllity before bein~
further processed. A stuffing box or packing ~land is normally used between the upper end of the casing snd the pump rod to prevent the escape of oil.
Durin~ operation of the pump, there i8 a glightly transverge movemsnt of the pump rod during its reciprocation, which under normal clrcum~tances very quickly wears the packlng in the stuffin~ box. Furthermore, ~n pumpin~ from inclined well casings or crooked well casin~s, there i~ llabl~ to be uneven wear of the pump rod and the stuf~ing box during operation due to the pump rod lying on the lower side of the stuffing box. As leakage of oil throu~h the stuffing box cannot be tolerated, there is therefore, during normal pumpin~
operations, a requirement to replace the packing in the 5tuffin8 box st frequent intervals. This problem has been overcome by utilizing a roller guide as disclosed in the assignee~s Canadian patent number 1,154,307 which issued on September 27, 1983. In this patent there i8 discl~sed a gulde consisting of a housing which includes two sets of parallel rollers mounted upon axes which are at right anglefi to each other, each roller of a palr being spaced apart such that the pump rod can be guided between the rollers without any transverse movement of the pump rod occuring through the guid~. The ~uide is positioned in B normal well head apparatus between the well head tee and the normal stuffin~ box.
In order to reduce the number of components which are utillzed upon a well head, which are required when using the roller guide of Can~dian patent 1,154,307, it is now proposed to combine certain of the components and improve the known roller guide so that it becomes part of a pump rod centralizer which also includeg at least one stuffing box, an oiler, and preferably a flap valve for preventing oil leakage which could occur lf a pump rod breaks in the region of the centralizer. Provision is also made in the centralizer for monitoring the prer~ure within the unit so that operation of the pump can be ~3~J~

stopped if l~aka~e occurs from the well through the lower stuffin~ box.
The centralizer ha~ algo been made with a Rmooth flowlng cylindrical outsr surface. The upper and lower threaded enda both utilize thread~d connections with preferably knurled cnd surfaces for gripping ~urlne ~nst~llation, ~n~
there are no extending flanges or bolts. The unlt there~ors pres~nt~ a relatively ~mooth outer ~urface which cannot catch a workman'~ clothe~ or cause injury.
The centralizer of this invention therefore con~lst~ in its most basic form of a housing having two sets of parallel rollers mounted on axes which are at riBht angles to each other, each roller of a pair being spaced apart such that a pump rod can be guided between the roller~ without any transverse movement of the pump rod. The hou~ing also has a lower stuf~ing box wlth a lower thresded bushin~ which screws into the well head tes and, in one embodiment, has an upper stuffing box which has a stuffin~ box cap thereover.
The housin~ preferably hag a lubricator so that the pump ro~ can be lubricatea to prevent scorchlng or burnlng of the packin~ within the stuffing box.
The invention will now be described with reference to the accompanying drawings in which:
Flgure 1 is a sectional view of one embodiment of the centralizer of this invention ta~en along its longitudinal axis, Figure 2 is a sectionsl vlew of a second embodiment of the centralizer taken along its lon~ltudinal axis, and Pigure 3 is a sectional view of a third embodiment of the centrali7er taken along its longitudinal axis.
Referring to the drawin~s and specieically to the embodiment shown in Fi~ure 1, the centralizer consists of a hollow cylindrical body 1 havine a cap 3 which is held to the body throu~h a scre~ threadsd joint 5. The lower ena of the body 1 has an outer screw threaded extension 7 and the upper end of the cap 3 has an outer screw threaded extension 9. Within the body 1 there is a cylindrical roller cage 11 having rollers 13 spaced vertically apart ln pairs, the upper pair beinB aligned lB0- from the lower pair. The roller cage and roller assembly is fully described in Canadian Patent 1,154,307.
A screw threaded aperture 15 is provided through the wall of the body 1 50 that lubricant, which is normally kerosene, can be fed in~ide the housin~ to provide lubrication for the pump rod 2 passlng throu~h the centralizer.

An upper stuf~ing box 17 is provided within the cap 3 and during operation includes a cylindrical spacer 19, a set o~ packing ring~ 21 and a further spacer 23. The packing is squeezed to~eth~r and s~ainst the pump rod 2 by a stuffing box cap 25 which is screwed onto threaded extension 9, A lower stuffing box 27 is provided within the extension 7 and during operation includes a spacer 29, a set of packing rings 31 and another ~pacer 33. A coupling is utilized to both compress the packin~ 31 and provlde a screw threaded extension for connection to the well head tee, the coupling consisting of a cylindrical packing retaining part 35 having a spigot 37, a collar 39 between the cylindrical part 35 and ~he gpigot 37, ana 8 screw threaded extension bl. SpiBot 37 slides within the inner bore of ~crew threaded extension 7 and has a set of 0 ring~ 43 to prov~de a ~eal between the spi~ot and the inner bore of 8crew threaded exten~ion 7. The coupling i~ hald in place by a cylindrical sleeve 45 which has a lip 47 which pU115 against the collar 39 to pull the spigot 37 into the bore within the screw threaded extension 7 so squeezing the packing 31 into contact with tha pump rod 2 and the inner bore of the stuffing box.
Referrin~ specifically to Figure 2, like ite~s to those shown in Pigure 1 have been identified by the same reference numerals. ~his ambodiment is th~
same as Fi~ure 1 except that the body 1 of the centralizer i9 of longer dimensions and includes therein a flap valve havin~ a flap 49 preferably m~da from a plastic material such as nylon or the like, the flsp baing pivoted by a pivot 51 secured to a cylindrical ca~e 53. A seat portlon 55 is formed on a short exte~sion from cap 3 so that if the pump rod falls into the well after breakin~ within the centralizer, the flap valve will pivot upwardly due to oil pressure and close off the well. The flap v~lve is detailed ln Cana~ian Patent 1,154,307.
Furthermore, an extra tapped hole 57 i8 formed through the bo~y 1 near its top end, this hole 57 being advanta~eously connected ~o a pressure operated electrical switch so that if oil leaks up from the well and through ths lower stuffin~ box, the rise in pressure within the centralizer will shut off the pumping mechanism and sound an alarm so that the fault in the lower stuffing box can be corrected before it reaches the proportions which woul~ cause leaXage of oil from the well head.
Referrin~ to Figure 3 there is shown a thir~ embodiment of the ~ - 3 -6~6 centrslizer, and agaln llke item9 to those shown in Figures 1 ana 2 havs the same reference numerals.
This embodiment o~ centrali~er has been de~i~ned as a short unit wherein a short well head apparatus is raquired. Thi~ unit is al80 espsclally usaful for wells using steam in~ectlon as there is provision for adequate lubrication, and also wells which are missligned as there i~ no gtuffing box at the upper end o~ the unit so that ~light transver8e movement of a pump rod is permitted to occur.
Referring first to the iower end of the unit, ~here i8 an inner screw threaded bore 59 which accommodates a cylindrical part 61 which ha~ an enlarged bore 63, part ~ay throu~h, within which i8 accommodated an upper spacer 65, packing rin~s 67 and a lower spacer 69. An upper ~crew threaded end 71 screws into the threaded bore 59 and a lowar screw thre~de~ extension 73 screws into a well head tee.
The upper end of the centralizer has an upper cup 75 of hollow cyllndrical form within which is an oiler media such as wadding 77, a ~asket 79 and a compression plate 81. Thc top o~ th~ cup 75 hag 8 cover 83 whlch pa~ses thereover and i~ held in place by hold down tap bolts 85. The lubricating liquid, such as kerogene, is therefore poured into the top of th~ CUp, tha cover 83 is then secured in place and this reservolr of oil ensures that thera is adequate lubrication on the pump rod 2 80 that burning of tha packing within the stuffin~ box does not occur even when the well i~ uslng a ~taam injection process. The lack of an uppsr stuffing box also permit~ ~reater flexibility of the pump rod through the csntralizer.
A plu~ 87 is shown within threaded bore 15 and, in this embodiment, this bore 15 can be used for instance for flushing out wax etc. from the inside of body 1 at intervals to ensure that an excessive build up floe~ not occur ~ithin the cantrallzer.
The materials from which the centralizer can be made are of co~rse numerous, however, preferAbly the housin~, stuffing boxes, roller an~ flap cages, to~ether with roller pins, are ~ads from a suitable corrosion resistant steel and the rollers and the flap valve are preferably made from eithsr nylon, ~E~RON , or TeFLO~ .
It is beliaved that a novel compact centralizer has been disclosed, this centralizer includlng stu~in~ boxes snd oilers ar well as ~uide rollers and * Trade Mark ~ - 4 -~3~
preferentially an anti-leakagc flap, and hencc u~e of thl~ centrallzer wlll reduce the nu~ber of units utili~ed on a well h~ad. The centrali~er i~ al~o resistant to wear and needs little maintenance, , - 5 -

Claims

1. A centralizer for guiding a pump rod through a well head consisting of a body, a roller guide within the body which can guide a pump rod along a path which is aligned with the axis of the well head, a cap screwed into the body to retain the roller-guide in place, a screw threaded aperture through the wall of the body, a lower stuffing box below the roller guide and a cylindrical retainer for retaining and compressing packing within the stuffing box.

2. The centralizer of claim 1, wherein the lower stuffing box is formed within a coupling, the upper end of which is accommodated within a lower extension of the body, the coupling having a central cylindrical part, and a lower screw threaded end part.

3. The centralizer of claim 2, wherein the upper end of the coupling is screw threaded and mates with a screw threaded bore within the lower extension of the body.

4. The centralizer of claim 2, wherein the upper end of the coupling is a plane spigot having a groove therearound, and an "0"-ring within the groove, the lower extension of the body having a plain bore within which the spigot mates, a collar between the spigot and the cylindrical part and a cylindrical sleeve having a lip at one end which can co-operate with the collar and an inner screw threaded part which mates with an outer screw threaded part on the lower extension.

5. The centralizer of claim 1, wherein the cap includes an upper stuffing box, an upper extension having a screw threaded outer surface, and a stuffing box cap having a screw-threaded inner surface which mates with the upper extension threaded surface for retaining and compressing packing within the stuffing box.

6. The centralizer of claim 1, wherein the cap is hollow and cylindrical and includes lubricant retaining wadding and a cover at the upper end.

7. The centralizer of claim 6, wherein the cap includes a plate over the wadding, and a gasket between the plate and the cover.

8. The centralizer of claim 1, including a cylindrical cage between the roller guide and the cap, and a pivotted flap within the cage, which moves upwardly against a seat on the lower inner face of the cap if the pump rod breaks and slips down into the well.

9. The centralizer of claim 1, wherein lubrication can be introduced through the aperture in the body wall.