US2695670A - Method for removing paraffin deposits - Google Patents

Description

Filed April 24, 1951 m 5321 3333 m /l I Z A F l WM 6 07 e 7 5 23 4 4 5 5 5 6 N n mm K. r. A m H s 5 \nven'l'or: Wiif'red S. Grake His Afiorneg United States Patent METHOD'FOR REMOVING DEPOSITS.

Wilfred S.-Crake,- Houston, Tex assignordo' shell'jDe 1 velopment Company, Em'eryvillepCirlifi, a corporation of Delaware Application April 24, 19.51,;Sefial N; 222,709 :1;

1 Claim. (Cl. 166-'-.-43)

This invention .relates :to theproduction of oil- .from-a well andpertains moreparticularlyto anv improvedmethodfor: removing .paraflinic andaasphaltic. deposits .from an.

the oil is pumped .or allowed .to iflow upztheproductiou.

tubing to the top of the well,.the temperatureof-theoil gradually. decreasesuntil a point-is reached .at whichlhe paraliin crystallizes out and accumulates: on theinside'.

walls of the tubing. In time, the. paraflin-accumulation continues to buildup until. thetvolumeof productionfrom the well is materially reduced or stopped..entirely.. The

operator of the well is then rfaced .With .thGlPIOblGIHLOf removing. the paraflin, the .removal .thereofwbeing, .generally both expensive and time+consuming.-,,

Heretofore, paraflin. deposits. could be cleaned from an oil well production tubing .by employing any oneof several. methods: .by introducing chemicalsinto. the. production tubing to :dissolve-theparaflin, by.lowering .an electric heater into the tubing to melt the deposits, by dropping a wire-line. go-devil into. thes tubing,.or by attaching scraper knives to thesucker rod string-in alpurnping well. With the exception of the last-mentioned method, the use. of auyrofi the methods tentailsconsiderable lost production time in that it is necessary to shut down the well while its produc-tiontubing -is being cleaned. In a like manner, it is necessary to shut awell down in order: to install 'or replace paraflin cutting-knives on a sucker rod string. Additionally, the installation of knives on several hundred feet of sucker rod string. is very expensive.

Accordingly, it is a general object of .this invention to providea method for removing paraffin. deposits froman oil well production tubing without. stopping theiflow of oil therethrough.

Another general object of this invention is to :providexa method for removing paraffin deposits from an oil well production tubing, Which"methodcombines mechanical and hydraulic features in order to clean the tubing etfecr;

tively.

A further object of the present invention is to provide a particularly effective and inexpensive method for cleaning the inner walls of a production tubing in a well while the well is being produced, thus utilizing the well flow to remove any paraffin particles from the well.

In accordance with this invention an elongated, flexible line, and particularly a flat ribbon steel wire is provided which is insertable into a well production tubing to be positioned against the inner wall thereof, whereby, upon relative rotational movement of the line and the tubing, the line is caused to move around the inner wall of the tubing and scrape the paraffin deposits therefrom through' out considerable vertical sections of the tubing as the well flow carries the scrapings to the surface. Hence, the scraping action of a weighted line suspended in the tubing and the hydraulic action of the pumped or flowing well fluid are both utilized to keep the inner surface of the production tubing free of paraffin deposits.

By combining in a single operation, mechanical and hydraulic action to remove material clogging a well production tubing, this invention makes possible more rapid and thorough removal of such material from the tubing.

By subjecting the paraflin clogging the tubing to a com bined mechanical and hydraulic action, the material broken up by the mechanical action is dislodged and "ice washedaway, quickly; rather than permitting-itto fall to.

thelbottom. of .the' weliagain. wheretit would :again be come dissolvedin high temperatureoilJ In'carrying out the present invention, a low cost parafiinscraper .of simple.

construction. may be used, which. permits the attainment of the resultsdesiredat agreat savingin operatingflcostand operatingtime. .1

The foregoingandother objects. andadvantages of this.

invention. will .be 'more readily understood by reference tothe'folIowing description of specific. apparatus. which 15 particularly well suited for. carrying out this invention.

It is. to be understoodthatthe preseutmethod is appli-, cable to other apparatus, such for example, as .the'yarb.

ousembodirnents disclosed anddescribed in my-copending. pateubapplication .entitlediP'araflin. Scraper for. Wells,.. Serial'..No.. 222,708, which. wasfiledApril 24,.

1.951, now Patent :No. 2,678,696. Various features and refinementsof the..present methodwill be understood from the. following. description in conjunction. with. the

accompanying drawing, wherein a Figure. l isa. diagrammaticview, partly. in cross .sec: tom, of .the upper-cportionofa cased well includingthe well head assembly.

Figure 2 is a diagrammatic view, partly in cross sec.- tion, of another; wellhead assembly includinglmeansfor rotating the production .tubing.

Referringto Figure l of the-drawing, the well bore 11' is shown to .contain-the'usual casing 12 having a. suitable. Well' head assembly I13 flanged to its upper. end. The.

well head assemblyf13may have any suitable. number andarrangement of-valves and fluid conduits, but for, purposes .of illustrating the. .present invention, the head- 131s 'shownas beingequipped with a single conduit. 14

for discharging. oil from the well casing.

Suspended from thewellhead 13, in any suitable man-. ner well knownto the art, is a production tubing 15 which .is normally positioned concentrically in the casing 12. The top plate 16 of the well head assembly 13 is provided withan. opening 17,.coaxialwith production tubing 15, saidopening. I'Tbeing closedinfa. fluidtight manner by a suitable stuffing box diagrammatically. represented.

at 18.. Mounted above .the stuffingboxlfi'on a pipesection 38 is a wire'linehanger head 19 in which .a wire line.

or scrapingcable .20 maybe fixedly secured inany suit: able .manner,.as.by riveting,v bolting orthe like. The hanger head.19 is closed at the top by a cap 21.

Alfixed .to theouter. walLof the hanger. head 19is a ring gear. 22 which. is adapted to mesh with adrive gear 23..

The-drive .gear23. in turn is fixedlylsecuredto a shaft 4.0

which is mountedin a bearing 24, and. driven by a handcrank .25. It is to .be.realized:that any suitablegearing arrangement,- prime. movermeans or drive mechanism may be employed to rotate the hanger head 19 and. the wire line.2'0. -The..wire line 2.0.may be of any. cross-sectional shape, for .example,.square, round, hexagonal, fiat rectangular or thelike, and .is of a. length sufiicient .to extend from. the top.of the welldownto .a. point .in, the production tubing 15where paraffin begins to deposit. For cleaning production tubing by the method of the present invention, it has been found that especially good results have been obtained by employing a wire line having sharp longitudinal edges, such as a line made of flat ribbon steel, e. g., steel baling or banding tape, having any desired width such as as, /2, inch, etc. In order to maintain a fixed tension on the line 20, a weight 26 of suitable dimension is secured to the lower end of the line.

In cleaning paraffin deposits from the inner wall of the production tubing 15, the drive gear 23 is turned by hand crank 25 to rotate ring gear 22, hanger head 19 and wire line 20. The wire line 20 may be moved around the inner wall of the production tubing at any desired speed, say, from one revolution a minute or one a day, depending on the amount of paraffin to be removed. As the paraflin particles are scraped from the production tubing 15 they are carried up the tubing 15 and out the discharge conduit 14 by the flowing stream of oil.

Instead of rotating the wire line 20 within the stationary production tubing 15, it may be readily seen that a tubing 27 may be rotated about a stationary wire line 23 as shown in the embodiment illustrated in Figure 2. In this embodiment, the well head assembly comprises a cylindrical housing 29 in which anannular thrust. bear-H,

ing 30 is mounted, as on support members 31. Rotatably mounted on the thrust bearing 30 is a slip bowl 32 and slips 33 for supporting the production tubing 27 in the well casing 34 in a manner in which it may be rotated. The top of the housing 29 is closed in any suitable fluidtight manner, as by rings of packing 35 between a junk ring 36 and a follower 37.

A swivel, diagrammatically shown at 39, is secured in the production tubing 27 above the well head assembly so that the tubing 27 below the swivel may be rotated while the portion of tubing above the swivel remains stationary. Above the swivel 27 the production tubing may comprise a short pipe section 41, a T 42 and a discharge conduit 43 leading to a storage tank or pipe line (not shown). A hanger head 44 closed at the top by a plug 45 is secured to the top of the T 42.

The wire line 28'is fixedly secured, as by rivets, to the inner wall of the hanger head 44 and preferably is af fixed to the head 44 to one side of its vertical axis in a manner such that at least one and preferably both edges of the steel ribbon-tape wire line scrape along the wall of the production tubing as the latter is rotated. Since as a practical matter, an oil well is never perfectly straight, the production tubing 27 will generally be at some small angle to the vertical which will cause the wire line 28 to scrape along the inner wall of the tubing 27 even when the wire line is atiixed to the center of the hanger head 44. As the tubing 27 is rotated about the wire line 28, the drag exerted by the tubing wall on the wire line causes the latter to be formed in a series of long spirals which efiectively scrape the entire inner surface of the production tubing 27 free of paratfin or other deposits.

In order to rotate the production tubing 27 extending below the swivel 39, a drive wheel 46 is provided which is fixedly secured to said tubing 27 between the swivel 39 and the well head assembly 29. Any suitable mechanical, electrical, pneumatic or hydraulic prime mover means 47 may be connected through suitable transmission means, as through a worm gear 48 to drive wheel 46 and rotate the production tubing 27. In operation, the production tubing 27 is rotated very slowly, for example, one or more revolutions a day depending upon Well conditions while the Wire line 28 remains substantially stationary.

From the above described embodiments it may be seen that the present method of removing parafiin from an oil well production tubing may be employed in a well when either the wire line or the production tubing are rotated. Thus, a method is provided for simultaneously removing parafiin deposits from the bore of a production tubing throughout its entire length or any desired portion thereof. Hence, if the well temperature at the 2000 ft. level is sufficiently low enough to cause paraffin deposition within the bore of the production tubing over the to 2000 ft. interval, the present steel scraping tape may be run into the tubing to the 2000 ft. level whereby the paraffin may be removed upon rotation of the production tubing and scraping tape with regard to each other. Thus, a method is provided for cleaning production tubing without the. necessity of reciprocating either the tubing or the From the apparatus described in my copendingapplication Serial No. 222,708 entitled: Paraflin Scraper for Wells, filed April 24, 1951, it may be seen that the present paraflin removal method may be employed in both. naturally flowing or pumping wells, as well as wells produced by the gas lift method. Pumping wells include those using pumps activated by either a reciprocating production tubing or a sucker rod string. Where a string of sucker rods is employed, the diameter or width of the wire line is of a size suflicient to pass through the annular space between the sucker rods and the inner Wall of the production tubing. While the present paraffin removal method may be employed to remove paraflin deposits when a well is not being produced, it is preferred that a flow of oil be maintained through the production tubing as its inner wall is scraped whereby the oil flow carries the paraifin particles out of the well. From the above description it may be seen that the above method of removing parafiin is especially advantageous when it is desired to clean the production tubing without interrupting production from the Well. Removal of parafiin deposits permits a well to be produced at a rate equal to the maximum throughput of the production tubing, i. e., at maximum efiiciency.

I claim as my invention:

A method of removing deposits of paraffin or asphaltic ,bodies from the inner surface of a production tubing positioned within a well, said method comprising the steps of introducing into said production tubing from the top thereof to a point at least level with said deposits an elongated metallic flexible line weighted at its lower end, scrapping all deposits from the inner wall of said tubing by producing relative movement between said flexible line and said tubing bymoving said line in an orbital path along the inner wall of said tubing, and simultaneously flowing the well fluid upwardly through said production tubing to remove the loosened deposits from the tubing.

References' Cited in the file of this patent UNITED STATES PATENTS Number Name Date 982,652 Wiechmann Jan. 24, 1911 1,662,984 Scott et al. Mar. 20, 1928 2,179,814 Conaghan Nov. 14, 1939 2,182,680 Rugg et al. Dec. 5, 1939 2,278,067 Emery Mar. 31, 1942 2,294,061 Williamson Aug. 25, 1942 2,471,198 Cormany May 24, 1949 2,552,939 Condra May 15, 1951 FOREIGN PATENTS Number Country Date 703,369 France Feb. 3, 1931

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