US2486308A - Paraffin scraper - Google Patents

Description

V oct. 25, 1949.

Filed March 20, 1945 G. MCCRAY ET AL.

PARAFFIN scRAER 2 Sheets-Sheet 1 Paren Agem Patented Oct. 25, 1949 PARAFFIN SCRAPER George McCray and Ralph H.A Smith, Houston,

Tex., assignors to Stanolind Oil and Gas Company, Tulsa, Okla., a corporation of Delaware Application March 20, 1945, Serial No. 583,724

This invention relates generally to the removal of para'in from oil and gas wells, and in particular is directed to apparatus for paraffin removal from the casing of wells producing uids through the annular space between the tubing and the casing, such as wells producing separately from each of two or more zones.

Various methods and devices have been proposed and used for removing parain from the production tubing of wells equipped in the conventional way to produce from a single horizon. For example, solvents have been introduced into the tubing to dissolve and remove parain accumulations therein in solution. However, due to the low solubility of the wax in most of the available inexpensive solvents, comparatively large amounts of these are required, or more expensive and highly refined solvents must be used.

Other systems of paraffin removal have relied upon liquefying the solid deposits by the application of heat in some manner, such as by electrical heating, circulation of steam, hot water, hot oil, combustion gases, and the like. While these systems are often satisfactory, special equipment must 'ordinarily be provided for generating and transmitting this heat energy into the well tubing.

The most used methods of paranin removal have been those in which the parafn is simply scraped or cut loose from the interior of the tubing by a tool passed through it. A large number of such mechanical cutters lor scrapers have been designed and used with satisfactory results for a long time.

As long as the producing equipment of a well consists of a casing within which is inserted a tubing for carrying all the production to the surface, the Aparaffin deposits, if any, are confined chiefly to the interior of this tubing, and can be satisfactorily dealt with by the foregoing removal methods. However, an increasing proportion of the wells now being drilled penetrate two or more separated productive zones, and many of these wells are being equipped to produce separately and simultaneously from each `of the Zones by utilizing both the tubing and the annular space between `it and the casing to conveythe fluids separately to the surface. This arrangement is commonly known as a dual completion." Also in certain Wells produced by gas lifting all of the production is taken through the annular space,r

8 Claims. (Cl. 166-18) tubing, which remains relatively clear of accumulations, but is mostly on the inner surface of the casing in the upper part of the well; Apparently the cooling of the paraffin-laden oil by heat loss through the casing to the comparatively cool earth formations in contact with the casing near the surface, combined with possible cooling due to gas expansion, encourages this deposition to occur, the inner casing Wall laording the necessary cool surface.

Due to the comparatively large Volume within this casing and to its intimate contact with the surrounding earth, neither the solvent nor the heating methods of removal are as effective as when only a relatively small diameter tubing is to be cleaned. Excessively large volumes of solvent are required merely to fill this space, and when heating is attempted, large heat losses to the formations loutside the vcasing inevitably occur.

Since almost all wells deviate at least slightly from the vertical, the tubing is practically certain to lie close to or lcontact the casing at one or more points along its length. Due to this irregularity of the annular space the design |of a cutting or scraping tool that can be raised lor lowered through it presents apparent difliculties, with the result that no such tool has been available. Consequently the procedure adopted for eld use heretofore has required that the well tubing be completely removed from the Well before scraping tools are introduced. Ordinarily this means that heavy mud or other `control means must be ernployed to shut off or kill the well production while the operations are being perilormed. The interruption of the well production and the time and expense of cleaning out the casing are correspondingly greatly increased, and the possibility exists of temporarily or permanently impairing the well productivity if all of the heavy mud should not be removed.

In view of this it is a primary object of our invention to provide an improved and practical apparatus for removing paraiiin deposits from the interior of a well casing without removing the well tubing. Another object is to provide equipment for mechanically cutting or scraping paraffin from the lcasing of a dually completed or other well Where production flows through the annular space, by the use of relatively light and easily portable well pulling tools. A further object is to provide such equipment in the form of a :permanent installation which may be left in the well, but whichdoes not impede Well production through the annular space. A still further object is to provide for paraffin' removal from a well casing apparatus which can be employed without killing or shutting in the well for an extended period :of time, the only interruption necessary being only minor and temporary. Other objects, uses, and advantages of the invention will become apparent as the description thereof proceeds.

In the drawings appended hereto and forming a part of this specification we have shlown an embodiment of our invention applied to a well producing from two separated zones. It is to be understood that this embodiment is ilor purposes of illustration only, and that the novelty of our invention is not to be considered as limited solely to the apparatus shlown. In these drawings, in which the same reference numeral in diiferent gures indicates the same or a corresponding part,

Figure 1 is a cross section of the upper end of an oil well showing ipartly in elevation and partly in section typical surface equipment and part of the apparatus of the invention;

Figure 2 is a cross section of the intermediate and lower parts of the Well with the remainder of the apparatus of the invention shown therein;

Figure 3 is an elevation with parts cut away showing the details of a telescoping or slip joint used in the invention; and

Figure 4 is an elevation, partially cut away, of a section of well tubing with a preferred type of cutting or scraping member attached thereto.

Essentially, this invention comprises a plurality of paraffin-cutting members attached to the tubing and spaced approximately uniformly throughout the zone of paraiin deposition on the casing. At some point in the tubing string below where the parafnn deposition starts is installed a telescoping or `slip joint which allows the upper part of the tubing string thereabove, carrying the cutting members, to be raised and lowered a distance equal to or greater than the spacing between cutting members. Thus by the simple operation of raising and lowering only a part of the tubing string for a limited distance, which can be done with easily portable and light weight pulling tools, the entire inner surface of the casing in that part of the well subject to paran deposition can be scraped and cleaned. Dislodged pieces of solid paraffin are carried out by producing the well atan appropriate rate during the operations.

Referring now to Figures 1 and 2, a well I0 is shown drilled from the earths surface Il, equipped with a surface casing I2, an oil string of casing I3 extending through producing zones I4 and I5, and a production tubing I6. Ordinarily a packer I1 is placed in the annular space between zones I4 and I5, and the casing I3 is perforated opposite both zones. With perforations in tubing I6 opposite only the lower Zone I5, it is apparent that production from each of the two zones is kept segregated. Production from zone I reaches the surface II via tubing I6 where it is discharged into a flow line I8 controlled by a valve I9, while that from zone I4 flows through the annular space between tubing I6 and casing I3, leaving the well through a iiow line 2!) controlled by a valve 2|. Master gate valve 22 may be provided to afford additional control -of well I0 As a safety measure a gate valve 23 and a blowout preventer 24 are preferably installed just prior to carrying out the parain removal operations. For lifting and lowering tubing string I6 a nipple 25 may be inserted through preventer 24 and valves v22 and 423, engaging threads at the upper end of the top joint or section 26 of tubing I6. The upper end of joint 28 may suitably be of larger diameter than the rest of the joint so as to provide a shoulder for supporting it and the rest of tubing string IS in tubinghead hanger 21. The outer surface of joint 26 is preferably ground smooth and polished so as to slide easily through a packing 28 in hanger 21 without causing excessive wear to the packing.

Spaced at approximately equal intervals throughout the entire zone of parailin deposition, such as at the couplings of tubing I6, are scraping or cutting devices 29, 30, 3l, and 32. At some depth below the lowermost of these cutters, which should be well below the lowest occurrence of parain deposits, .a telescoping or slip joint indicated generally at 34 is incorporated in tubing string I6. Below slip joint 34 is also inserted in tubing I6 a removable tubing plug 35 for cutting off flow through the tubing temporarily during the operations. This plug 35 may be any of the commercially available types, preferably one which may be inserted and withdrawn on a steel wire line, and should be equipped with an equalizing vave by which the pressure in the tubing therebelow can be released before the plug is withdrawn.

The details of construction of the slip joint 54 may be varied within wide limits, that shown in Figure 3 possessing certain advantages for use in the present invention. This joint may suitably comprise an inner tubing 36 and an outer tubing 31 of somewhat larger inside diameter than the outer diameter of tubing 36, leaving a small annular space between them. Threaded to the lower end of outer tubing 31 is a sleeve 38 carrying a recess containing packing 39 compressed by a threaded nut 40. Packing 3S seals against the outer surface of inner tubing 36, which is preferably ground smooth and polished.

Threaded to the upper end of inner tubing 36 is,

a tip 4I having a beveled face 42 adapted to seat against a shoulder 43 at the upper end of outer tubing 31 when joint 34 is in closed position.

When seated, this prevents possible foreign matter from entering and clogging the space between tubes 36 and 31.

The outside of tip 4I is provided also with spurs or teeth 44, which engage corresponding teeth 45 on the inside of sleeve 38. It will be apparent that when joint 34 is extended so that teeth 44 and 45 are engaged, as in the manner of a spline joint or jaw clutch, torque may be transmitted through joint 34 to that part of tubing IS below it for any desired purpose, such as setting a packer, regulating a bottom hole choke, backing olf or unscrewing a left-hand threaded safety nipple, and the like. As indicated previously, the lengths of tubes 36 and 31 must be suicient to permit a vertical movement of the upper part of tubing I6 somewhat in excess of the spacing between the cutters xed to it.

A variety of types of paraffin scraping or cutting members may be devised, bearing in mind the limitation that flow through the annular space must not be unduly impeded. The scraper shown in Figure 4 has been tried and found practical. Secured to and projecting radially from a sleeve 46 are a large number of spring wire iingers 41, of a length sufficient to contact casing I3 simultaneously at points around its entire circumference. If desired, the ends of each of the wire fingers 41 may be flattened so as to present a sharp knife-like edge to the paraiin deposits.

In Figure 4 is shown also a preferred manner vof securing these scraping devices to the tubing I6. The inside diameter of sleeve `46 being slightly larger than the outside diameter of the'upset `portion 48 of tubing I6 near each tubing coupling, sleeve 46 is accordingly slipped over upset .48, thin metal shims being inserted between if .necessary to make a tight fit. Thereafter sleeve 46 is tack welded to upset 48 at two or more places, such as at 49 and 50.

In operation, after the insertion ofv plug 35 to shut off the flow through tubing I6 and the installation of valve 23 and blowout preventer 24, lifting nipple 25 is coupled to the upper. end of tubing joint 26. Then by means of a hoisting or pulling unit, of which only the tubing elevator 5I is shown, that part of the tubing I6 above slip joint 34 is slowly raised and lowered while the -well is being produced through the annular space .to sweep out the dislodged parain. By noting any decrease in tension required to raise the upper enclV of tubing I6 and by examining the oil flowing in line for the presence of paraffin cuttings, an estimate can be made of when the casinghas been suiiiciently cleaned. The cutting ac- .tion is improved if tubing I6 is rotated slowly yposition was occurring on the top 1500 feet of casing. The telescoping or slip joint assembly -34 in this well was installed at a depth of about 3000 feet, the total length of the tubing being labout 10,000 feet. This joint 34 allowed about a 28-foot vertical movement of the top 3000 feet of tubing, and the individual cutters were installed at approximately .Z5-foot intervals, beginning slightly more than feet below the tubing hanger and extending about 100 feet below the lowest known parain deposits. Using a light weight pulling unit, and adjusting the production through the annular space to about 12 or 15 barrels per hour, it was found that raising and lowering the apparatus about 1'7 times at 90-day intervals kept the casing satisfactorily free of eX- cessive parain. The total time to perform each entire cleaning operation averaged only about six hours, representing a very great saving in time. Naturally the time interval between successive cleanings will vary widely from well to well, and the details and dimensions of the various parts of the apparatus can be modified to suit particular well conditions. For example, if three or more formations are produced through concentric tubing strings, and deposition is found to be occurring on one of the outer strings, the next adjacent inner string can be equipped with Scrapers and a slip joint as taught herein, for the purpose of removing the deposits.

It will be apparent also that in wells where the lower end of the tubing is free to move, as where the well fluids are being gas lifted through the annular space and there is no packer, cleaning of the inner casing wall may be satisfactorily done by omitting the sliding joint and using only the plurality of Scrapers on the tubing. As in such an installation the entire tubing string must be lifted and lowered, heavier hoisting equipment 'may be required, but one of the principal advanvby the scope of the appended claims.

We claim:

1. In a cased dual-completion well structure, adapted for recovery of hydrocarbon products from a, plurality of spaced producing strata, a tubular producing conduit extending within and spaced from the well casing, thereby providing an inner producing conduit and an outer producing conduit within the well, the outer conduit having spaced fluid inlets, theinner conduit having a fluid inlet adjacent its lower end, a fluid-excluding seal between said conduits and between the spaced fluid inlets of the outer conduit and above the fluid inlet of the inner conduit, said seal preventing fluid flow between said conduits, a telescoping, fiuid-tight joint in said tubular conduit,

a plurality of spaced parain-cutting members fixed to the exterior wall of said tubular conduit above said joint, and means for reciprocating the portion of said tubular conduit above said joint.

2. In a cased dual-completion well structure, adapted for recovery of hydrocarbon products from a plurality of spaced producing strata, a tubular producing conduit extending within and spaced from the well casing, thereby providing an inner producing conduit and an outer producing conduit within the well, the outer conduit having vspaced fluid inlets, the inner conduit having a fluid inlet adjacent its lower end, a fluid-excluding seal between said conduits and between the spaced fluid` inlets of the outer conduit and above the fluid inlet of the inner conduit, said seal preventing fluid ow between said conduits, a telescoping, fluid-tight joint in said tubular conduit, a plurality of spaced paraffin-cutting members fixed to the exterior wall of said tubular conduit above said joint, the spacing between said members being less than the telescoping movement of said joint, and means for reciprocating the portion of said tubular conduit above said joint.

3. In a cased dual-completion well structure,

adapted for recovery of hydrocarbon products 50y from a plurality of spaced producing strata, a tubular producing conduit extending within and spaced from the well casing, thereby providing an inner producing conduit and an outer producing conduit within the well, the outer conduit having spaced fluid inlets, the inner conduit having a iiuid inlet adjacent its lower end, a uidexcluding seal between said conduits and between the spaced fluid inlets of the outer conduit and above the fluid inlet of the inner conduit, said seal preventing fluid flow between said conduits, a telescoping, fiuid-tight joint in said tubular conduit and a plurality of spaced paraffin-cutting members fixed to the exterior wall of said tubular conduit above said joint, 'said joint and the lowermost of said spaced members being disposed at points on said tubular conduit below the point at which paraffin deposits in the conduit formed between the outer surface of said tubular conduit and the inner surface of said casing.

4. In a cased dual-completion well structure, adapted for recovery of hydrocarbon products from a plurality of spaced producing strata, a tubular producing conduit extending within and spaced from the well casing, thereby providing an inner producing conduit and an outer producing 7 conduit within-the well, the cuter conduit having `spaced iiuid inlets, the inner conduit having a fluid inlet adjacent its lower end, a iluid-excluding sealbetween said -conduits and between the spaced uid inlets of the outer conduit and above the fluid inlet of the inner conduit, said seal preventing fluid flow between said conduits, a telescoping, fluid-tight joint in said tubular conduit and a plurality of spaced paraffin-cutting members xed to the exterior wall .of said tubular conduit above said joint, said paraffin-cutting members comprising a plurality `of flexible elements with interstices therebetween, and means for reciprocating the portion of said tubular conduit above said joint.

`5. In a cased dual-completion well structure, adapted for recovery of hydrocarbon products from a plurality of spaced producing strata, a tubular producing conduit extending within and spaced from the well casing, thereby providing an inner producing conduit and an outer producing conduit within the well, the outer conduit having spaced iiuid inlets, the inner conduit having a fluid inlet adjacent its lower end, a fluidexcluding seal between said conduits and between the spaced fluid inlets of the outer conduit and above the fluid inlet of the inner conduit, said seal preventing fluid flow between said conduits, a telescoping, fluid-tight joint in said tubular conduit and a plurality -of spaced paraffin-cutting members fixed tothe exterior wall of said tubular conduit above said joint, said paraffin-cutting members comprising a plurality of radially disposed wires the .outer ends of which contact the inner surface of said casing, and means for reciprocating the portion of said tubular conduit above said joint- 6. In a cased vdual-completion well structure, adapted for recovery of hydrocarbon products from a plurality of spaced producing strata, a tubular producing conduit extending within and spaced from the well casing, thereby providing an inner producing conduit and an outer producing conduit within the well, the outer conduit having spaced iuid inlets, the inner conduit having a fluid inlet adjacent its lower end, a fluidexcluding seal between said conduits and between the spaced fluid inlets of the outer conduit and above the fluid inlet of the inner conduit, said seal preventing fluid flow between said conduits, a telescoping, fluid-tight joint in said tubular conduit and a plurality of spaced parailln-cutting members fixed to the exterior wall of said tubular conduit above said joint, stops at either end of `said telescoping joint to limit the vertical movement of said tubular conduit above said joint while permitting vertical movement for a distance greater than the spacing between said parain-removing members, and means for reciprocating the portion of said tubular conduit above said joint.

7. In a cased dual-completion well structure, adapted .for recovery of hydrocarbon products from a plurality of spaced producing strata, a tubular producing conduit extending within and spaced from the well casing, thereby 'providing an inner producing conduit and an outer producing conduit within the well, the Aouter conduit having spaced fluid inlets, `the inner conduit having a fluid inlet adjacent its lower end, a fluid-excluding seal -between said conduits and between the spaced Iluid inlets of the outer conduit and above the fluid inlet of the inner conduit, said seal 'preventing fluid flow between said conduits, a telescoping, fluid-tight joint in said tubular conduit anda plurality of spaced paraffin-cutting membersxed to the exterior wall of said tubular conduit above said joint, a clutch built into said telescoping joint whereby the portion of said tubular conduit below said joint 'may be rotated ,around its major axis responsive to similar rotation of the portion of said tubular conduit above said joint, and m-eans for reciprocating the portion fof said tubular conduit above said joint.

8. In a cased :dual-completion well structure, adapted for .recovery of hydrocarbon products from a plurality of spaced Aproducing strata, an outer casing in said well, said outer casing hav ing spaced fluid inlets, :an inner producing tubular conduit within said casing and spaced therefrom, said inner tubular conduit comprising a tubular upper section, a tubular lower section and a telescopin-g, fluid-'tight `joint connecting said upper and lower sections, said lower section having a fluid inlet adjacent its lower end, a fluid-excluding seal between said casing and said lower section and ybetween the spaced uid inlets of said casing and the fluid inlet of said lower section, said lseal preventing fluid .ow between the channels formed by said casing and said inner conduit respectively, za plurality of .spaced paraiiin-cutting members ailixed vto said upper section, means for vertically reciprocating and rotating said upper section independently of said lower section to remove paraln from ythe inner surface of said casing, above said joint, without shutting oif well production.

y'GEORGE MCCRAY. RALPH H. SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,342,618 Bashara June 8, 1920 1,806,073 MacGregor et al. May 19, 1931 1,919,350 Wickersham July '25, 1933 2,074,608 Gosline Mar. 23, 1937 2,304,303 Ferguson Dec. 8, 1942 2,315,931 Burt et al. Apr. 6, 1943 2,341,832 Verheul et al Feb. 15, 1944 2,374,317 Wright Apr. 24, 1945

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