US3394763A - Free piston type paraffin scraper - Google Patents

Description

July 30, 1968 c. B. PAGE, JR 3,394,763

FREE PISTON TYPE PARAFFIN SCRAPER Filed Deo. 29, 1965 2 Sheets-Sheet 1 E nl.. mlllw.

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4 lA m Ma July 3o, 196s C. B. PAGE, JR 3,394,763

FREE PISTON TYPE PARAFFIN SCRAPER Filed Deo. 29, 1965 2 Sheets-Sheet 2 TEE' THE;

United States Patent O 3,394,763 FREE PISTON TYPE PARAFFIN SCRAIER Charles B. Page, Jr., Marrero, La., assignor to Texaco Inc., New York, NX., a corporation of Delaware Filed Dec. 29, 1965, Ser. No. 517,413 Claims. (Cl. 166-170) ABSTRACT 0F THE DISCLOSURE This invention concerns a so-called free piston type paraffiin scraper. More specifically, it relates to a paraffin scraper (of the free piston type) which has improved structure for more reliable and trouble-free operation.

Heretofore, while there have been several different structures for so-called free piston type paraffin scrapers (or plungers), none of the known structures have been entirely satisfactory in operation. The necessary internal by-pass structural arrangements have included those with structure that move a by-pass valve from open to closed position and which employs tripping pins extending from the ends of the structure. Furthermore, it has been the usual practice to provide a detent arrangement to hold the by-pass valve either open or closed as the case may be whichever position it is in. Such known structures have apparently not been satisfactory in operation. They have tended to stick and to cause the proper functioning of the free piston to cease.

Consequently, it is an object of this invention to provide improved structure for a free piston type parafin scraper, which is trouble-free and avoids any sticking of the by-pass valve structure. Furthermore, the structure according to this invention eliminates any upper tripping structure in the body of the plunger, and internal connections therefrom to the by-pass valve.

Another object `of the invention is to provide improved wiping rings for more effectively cleaning the walls of the tubing.

Briefly, the invention concerns a free piston type parain scraper adapted for moving vertically within well tubing. It comprises an elongated body having means for wiping the walls of said tubing, and having an internal passage extending longitudinally through the body from below said wiping means to provide passageway for fluid by-pass when the scraper is descending in said tubing. The scraper also comprises at least one port through the wall of said body connecting with said internal passage and located below said wiping means. It also comprises gravity type ball valve means for closing said internal passage above said port whereby said scraper will be forced upward through said tubing by fluid flowing therein.

The foregoing and other objects and benefits of the invention will be more fully set forth below in connection with the best mode contemplated by the inventor of carrying out the invention, and in connection with which there are illustrations provided in the drawings, wherein:

FIGURE 1 is a schematic longitudinal elevation partly in cross section and showing a tool according to the invention located within well tubing;

FIGURE 2 is a somewhat enlarged, longitudinal elevation partly broken away in cross section which shows the tool per se in addition to the tripping rod and a centralizer thereon, both located above the tool;

3,394,763 Patented July 30, 1968 ICC FIGURE 3 is an enlarged longitudinal elevation, partly in -cross section, showing the lower end only of the tool;

FIGU-RE 4 is a view similar to that of FIGURE 3 but showing only the valve structure, and illustrating the valve elements in the opposite position from that illustrated in FIGURE 3;

FIGURE 5 is a transverse cross section taken along the lines 5 5 of FIGURE 4, looking in the direction of the arrows;

FIGURE 6 is a side elevation, showing one of the wiper rings that `are located in pairs on the lower portion of the tool;

FIGURE 7 is also a side elevation, showing the other one of each of the pairs of rings;

FIGURE 8 is a top plan view of the ring illustrated in FIGURE 7;

FIGURE 9 is a side elevation of the tip portion of the tripping rod; and

FIGURE 10 is a bottom plan View of the tripping rod illustrated in FIGURE 9.

Referring to FIGURE 1, there is illustrated .a well 11 having tubing 12 therein. At the surface, there is a well head 13 with a chamber 16 attached thereto for receiving a free piston type tool 18 when at the top of its travel within the well.

The tool 18 is made up of a body section 19 that has attached at the top thereof a plurality of so-called sinker bars 20. These sinker bars 20 are substantially identical to yone another except for the top most one, and they are fastened together, in use, by a male threaded extension 21 on each for attachment of the next succeeding bar thereabove. The purpose of the sinker bars is merely to add weight to the free piston tool, and therefore the number of such bars employed depends upon the conditions of the particular well that is being scraped.

The body 19 of tool 18 carries thereon a plurality of pairs of scrapings rings 23 and 24. These rings are both constructed of a resilient material and each have an outside diameter sufficient to create pressure against the walls of the tubing that is to be scraped. While any feasible number of these scraping ring pairs may be carried by the body 19 of the tool, it is preferable for a tool according to the invention to embody four pairs of these rings along the length thereof, eg. see FIGURE Z where the topmost pair is shown in cross section.

As will appear in greater detail below, the scraper rings are constructed in such a way that, in addition to the fact of their being made of resilient material and of a size for applying some pressure against the walls of the tubing, the rings 23 and 24 act cooperatively with one another and provide for a mutual spreading action as movement of the =body 19 takes place within the tubing 12.

As already indicated, the tool 18 is a free piston type and consequently it has a provision for by-passing fluid around the pairs of scraper rings 23, 24 as it descends downhole within the tubing 12. This by-pass arrangement includes internal valve structure that will be described in greater detail below. Briefly, the by-pass involves a plurality of ports 28 that are located through the side walls of the tool below the scraper rings and connect to an internal passageway 30 that accommodates ow of the well uid within the body 19. This passageway 30 connects with additional ports 29 that are located in the body 19 above all of the scraper rings 23 and 24.

When the by-pass is closed, well fluid flowing upward within tubing 12 will carry the tool along and cause paraffin scraping action by the scrubbing effect of the pairs of rings 23 and 24. Of course such action takes place throughout the length of the tubing and until the tool is forced up through the well head 13 and related equipment (not shown) and into the receiving chamber 16. Then the internal valve which is a gravity type ball valve 3 (see FIGURES 3 and 4), will be tripped by reason of interaction between the valve structure (within the body 19 of the tool) and a tripping rod 32 that is long enough to extend down through all of the sinker bars 20 and into the body 19 of the tool 1S for causing the valve tripping action desired.

In order to keep the tripping rod 32 centralized within the chamber 16 there is a weighted centralizer 33. This centralizer is constructed of heavy enough material to tend to slide downward along the rod 32 and rest against the shoulders of a star shaped flanged tip 34 that is integrally formed on the lower (free) end of the rod 32. The centralizer 33 has an internal passage 35 that is of a size to allow free sliding movement along the rod 32. The outside diameter of the centralizer is only somewhat less than the internal diameter of chamber 16 in `order that the rod 32 will always be held in substantially the center of the bore of the chamber.

It will be appreciated that as the scraping tool 18 rises up into chamber 16 above the well head, the uppermost sinker bar 20 will pass over the tip 34 of the rod 32 and will contact the lower surface of the centralizer 33. Then, as it continues to rise it will carry the `centralizer upward in a sliding movement along the rod 32 (within the chamber 16), until the tripping position for the scraping tool has been reached. At that time the by-pass will be opened and the tool will be free to descend once more down within the tubing 12.

The tripping rod 32 is supported centrally near the top of the chamber 16, in any feasible manner, eg., by having threads 36 at the upper end of the rod 32 as illustrated in FIGURE l. Thus, the rod is attached to the center of a top plate 37 of the chamber 16. This may be through a hole in the plate with internal threads (not shown) and a depending sleeve 39 to add lateral stiffness. The rod is clamped rmly by means of a nut 38 screwed onto the free end of the threaded portion 36 of the rod 32.

It will be appreciated that it might be desirable to spring mount the tripping rod 32 for cushioning the shock when the valve structure is contacted. This could be done in any feasible. manner, not shown.

Referring now to FIGURES 2 through 10 of the drawings, some of the more detailed aspects of the structure will be described. FIGURE 2 shows the complete tool 18 with the body 19 having four sinker bars 20 attached thereabove. The unit is shown in operative relationship with respect to the tripping bar or rod 32. The latter is illustrated by a fragmentary showing of the bottom of the rod in axial alignment with the tool 18 and with the centralizer 33 located in position on, but displaced upward a short distance above its normal resting place against the tip 34 thereof. It will` be observed that the uppermost sinker bar 20 has a smoothly flared mouth portion 41 in order to guide the top sinker bar over the tip 34 of tripping rod 32 when the tool rises and reaches the location of the tripping rod, near the surface.

Each of the intermediate sinker bars 20 has a female threaded socket portion 42 at the lower end thereof when in the position illustrated (see FIGURE 2). Each of these sockets 42 receives and is screwed onto the male threaded extension 21 located at the top of each of the sinker bars 20, or in the case of the bottom sinker bar to a similar extension 43 located at the top of the body 19 of the scraper portion of tool 18. Thus, a series of the sinker bars 20 are securely attached to one another and to the top of the body 19 in order to make additional weight for the tool, as required. Of course, each of the sinker bars 20 has an internal passage 46 that is sufciently large to permit the tip 34 and rod 32 to pass freely down through this passageway as the tool rises into the chamber 16.

The body 19 of the tool has a central passageway 30 that extends therethrough from the top (as viewed in the drawings) down near the bottom into communication with the ports 28. The passage has the same size diameter as the passageways 46 through the sinker bars 20. On the outside of the body 19, there is a collar 50 located near the top but having a short neck portion 51 extending thereabove. The above mentioned ports 29 extend through the neck 51 in order to connect the internal passageway 30 with the annular space around the tool (when located in the tubing 12). At the upper edge of the neck 51, there is a standard type fishing neck structure 52. This is for use in case the tool should come apart down hole. It will be observed that similar fishing neck structures are included at the top of each of the individual elements going to make up the tool.

Along the body 19 below the collar 50 (as viewed in FIGURE 2) there are a plurality of grooves 55, four in number, that have a reduced outside diameter compared to the collar These grooves, or reduced diameter seetions along body 19, are dimensioned to accommodate the pairs of split rings 23 and 24 thereon. Between each of the grooves 55, there is a group of three spacer seal rings 56 that are an integral part of the body 19 and have the same outside diameter as the collar 50. They are formed as rings separated by two seal grooves 57 to discourage straight ow between pairs of split rings and to provide some space for accumulation of parain particles. Below the lowermost set of scraper rings 23 and 24 there is another collar 59 that has the same outside diameter as the body spacer rings 56 and the upper collar 5t).

Below the lower collar 59, there are the lower ports 28. They are formed in two sets, longitudinally spaced apart for cooperation with internal structure of the bypass valve, as will be described in greater detail with respect to FIGURES 3, 4 and 5 of the drawings.

The details of the by-pass valve structure that are illustrated particularly in FIGURES 3, 4 and 5, comprise an important feature of the invention. It will be noted that there is attached at the bottom of the body 19 of the tool, i.e., below the collar 59 (when viewed as illustrated in the drawings) a tip or nose section 60. This nose section 66 is fastened securely onto a lower threaded extension 61 that depends from the collar 59. This is accomplished by having a tapped socket 63 for receiving the threaded extension 61. There is a slightly enlarged chamber 64 located mostly within the extension 61 and at the lower end of the passageway 30. This chamber 64 is coaxial with the passageway 30. The chamber has a beveled lower edge 65 which forms a valve seat in conjunction with a ball 68 that is located within the bore of a coaxial chamber 69 located in the nose section 60 below the tapped socket 63. The ball 68 is supported by a cage 67. This takes the form of a cup like hollow forming a sleeve on the upper edges of a piston 70` that is machined for a uid tight sliding t within the bore 69. The length of the piston 70 is such as to provide limited vertical movement within the chamber 69.

As indicated above, the piston 70 has a smooth cyclindrical upper portion on the exterior thereof formed over the hollow of the cage 67. This acts by reason of the slide fit to provide uid valving action in relation to both the upper and lower sets of ports 28 in the nose section 60 of the tool. The cage portion of the piston 70 is hollowed out and has a spherically rounded bottom 71 to form a cup that supports the ball 68 under certain conditions.

At the center of the bottom 71 of the cage 67 (within piston 70) there is a short axial passage 73 that connects with a plurality of radial passages 74. All of the radial passages 74 extend out of the surface of the piston 70 and are interconnected peripherally by a groove 75 that extends all the way around the external surface thereof. Extending from the bottom of the piston or sleeve 7) there is an integrally connected pin 78 that extends beneath the lower surface of the nose 60 or not depending upon the position of the piston 79, with which it moves at all times.

Located within the bore of chamber 69 and above the sleeve or piston 70 (when viewed as illustrated in FIG- URES 3 and 4), there is a relatively light coil spring 80 that is inserted with one end resting against a shoulder 81 and with the other end in contact with a slightly beveled edge 82 of the piston 70. The spring 80 acts to `apply a bias force on the piston or sleeve 70 tending to move it downward into its lowermost position, i.e. the position illustrated in FIGURE 3.

The upper set of ports 28a are located just beneath and tangent to the beveled edge 65 of chamber 64. These provide passage for liuid flow from the exterior of the tool to the inner passage 30, therethrough. Of course, such fluid flow path will be cut off whenever the ball 68 is up into valve closing position in relation to the valve seat surface formed by beveled edge 65, e.g. the position illustrated in FIGURE 4. The other set of ports 28b are spaced axially somewhat below ports 28a and are arranged for interconnecting with the groove 75 of piston 70 when the piston is in its uppermost position, e.g. the position illustrated in FIGURE 4.

FIGURE 6 illustrates the upper one (when the tool is in its working position) of a pair of the scraper rings, i.e., ring 23. It will be observed that this ring is formed with a split ring structure, having an opening 84 therein to permit a squeezing down in the outside diameter and to facilitate removal of the ring from the body 19 of the tool. IExternally the ring 23 has beveled edges 85 and 86, of about the same width and bevel angle, while internally there is a straight cylindrical opening 87 from the top down to a point near the bottom where it meets an internally tapered or conical surface 89. Surface 89 widens and intercepts the beveled edge 86 of the ring 23.

A typical one ofthe rings 24 is illustrated in FIGURE 7. In this case the internal opening 88 is a straight cylindrical shape from top to bottom. The exterior surface has v.

a beveled edge 90 at the lower edge thereof which is similar in width and angle to edges 85 and -86 of rings 23. However, at the upper edge of each of the rings 24 there is a much wider beveled edge 91 that has a slope substantially the same as (for cooperating with) the internal conical surface 89 of each of the other rings 23. Here again, rings 24 are made with split ring structures so that there is an opening 94 to provide for snapping the ring into place on the body of the tool 19 and to permit squeezing thereof.

It will be observed that when both rings 23 and 24 are in place on the tool and the tool is moved upward within the tubing, there will be a tendency for the cooperating tapered surfaces 91 and 89 to act upon one another so as to cause the upper ring 23 to be spread outward by the camming action of the tapered surface 91 acting axially against the corresponding internal taper of surface 89.

FIGURES 9 and 10 illustrate in more detail the structure of tip 34 of the rod 32. It will be observed that the tip is formed with four round-tapered flanges 95 that are spaced equally around the end of the rod 32 to form a star-shaped pointed end. The effect is to provide an enlargement that will support the centralizer 33 and keep it from falling off the bottom of the rod 32, while providing space for uid llow past the tip 34 when it enters passages 46 and 30 of the tool 18.

Operation The operation in general is standard for free piston type parain Scrapers. However, with respect to this invention it may be best understood with reference to FIGURE 1 and to FIGURES 3 and 4 which latter show the workings of the internal valve structure. Thus, while free piston type scraper tools are old and well known in the art, they have been relatively unsatisfactory in their operation and it is an attribute of this invention that the internal valve structure operates so as to avoid suc-h difficulties.

Commencing with the operation of the tool as it is allowed to fall freely down the tubing, it is to be noted that dur-ing such action, the scraper ring pairs are acting to scrub the tubing walls by reason of their dimensions as indicated above. It may also be noted once more that the size of the openings 84 and 94 in the rings 23 and 24 are such as to allow room -to squeeze Ydown and accomodate drift in the inside diameter of the tubing. The scrubbing action is enhanced by the improved dual ring structure according to this invention, which is described in considerable detail above.

During downward descent of the tool within lthe tubing, the well fluid is able to llow through the interior of the tool. In this manner the fluid flow bypasses the scraper rings by entering the upper set of ports 28a and flowing through the central passage 30 of the body 19 of the tool as well as on upward through passage 46 within the sinker bars as well as out through the upper ports 29 to join the well liuid above the scraper rings (plus the spacerseal rings 56) on the body 19.

When the tool reaches the bottom of the tubing, or a preset stop element therein, it will :be set for upward movement thereafter. The setting action is created when pin 78 strikes the stop, or the bottom of the tubing, and thus lifts the piston and cage 67 upward within the chamber 69. This action is illustrated in FIGURES 3 and 4 where the elements are shown in FIGURE 3 in the positions for descending. On the other hand, they have been shifted, or set to the other state, in FIGURE 4.

Cage 67 carries ball 68 therewith and closes the upper set of ports 28a by reason of the upper (sleeve) edge of the piston 70 sliding across the inner openings of these ports. In addition to closing the upper sets of ports 28a, the lower set of ports ZSb will be in alignment with the circumferential groove in the piston 70. Therefore uid from the well is able to flow inward through the radial passages 74 and up through the short axial passage 73 to lift the ball 68 within the cage 67 and force it into valve closing contact with the beveled valve seat surface 65.

When the ball valve is thus closed, the fluid is no longer able to flow through the by-pass around the scraper rings (on the body 19 of the tool) and consequently the fluid flow pressure will cause the tool to be lifted and carr-ied upward therewith. This then reverses the movement of the tool within the tubing and causes scraping action once more during its upward movement.

The upward movement of the scraper will continue until the tool reaches the surface. As the tool 18 reaches the top of the tubing, the tip 34 of the tripping rod 32 will enter the internal passage 46. It is guided into the passage centrally thereof by being maintained in a coaxial position (centralizer 33) and by the widened mouth 41 at the top of uppermost sinker bar 20.

As the tool 18 continues to rise, the tripping rod 32 will extend on into passage 3() of the body section 19 until the tip 34 of the tripping rod 32 strikes the ball 68. In this manner the ball 68 is moved downward olf its valve seat 65 which opens the Aby-pass passageway around the tool once more.

When the by-pass valve has thus been tripped, it will assume its other position, i.e. that illustrated in FIGURE 3, by having the ball 68 fall by gravity into the cage so as to rest against the rounded bottom 71. Then the tool is enabled to descend once more, with the well fluid owing through the tool in by-pass of the scraper rings, as before.

It will be noted that this operation continues automatically so long as there is suliicient well fluid flowing to carry the tool upward therewith. Consequently an automatic tube scraping action is continuously carried out without any attention except for any periodic checks that may be desired.

It will be noted that the construction of the by-pass valve in this tool is relatively simple in structure and sure in action. Thus a common defect in prior by-pass structures, namely premature closing of the by-pass due to shock or lluid, is avoided.

While a particular embodiment of the invention has been described above in considerable detail, in accordance with the applicable statutes, this is not to be taken as in any way limiting the invention but merely as being descriptive thereof.

I claim:

1. A free piston type parafiin scraper adapted for moving vertically within well tubing comprising an elongated body having means for wiping the walls of said tubing,

said wiping means comprising at least one pair of split rings having cooperatively tapering end walls for causing one of said rings to tend to open the other,

an internal passage extending longitudinally through said body from a point below said wiping means to provide passageway for lluid by-pass when the scraper is descending in said tubing,

at least one port through the wall of said body connecting with said internal passage and located below said wiping means, and

gravity type ball valve means for closing said internal passage above said port whereby said scraper will be forced upward through said tubing by uid Howing upward therein.

2. A free piston type parain scraper adapted for moving vertically within well tubing comprising an elongated body having means for wiping the walls of said tubing,

an internal passage extending longitudinally through said body from a point below said wiping means to provide passageway for uid by-pass when the scraper is descending in said tubing,

a plurality of longitudinally spaced ports through the walls of said body and located below said wiping7 means,

gravity type ball valve means for closing said internal passage above said ports whereby said scraper will be forced upward through said tubing by uid owing upward therein,

a sleeve valve element including an internal cage structure for said ball,

said sleeve structure cooperating with said plurality of ports and having two positions whereby in one position said ball is contained in said cage with the upper ports open for providing fluid by-pass through said internal passage, and in the other position said sleeve closing said upper ports and opening the lower ports into a fluid connection below said ball for lifting same and closing said ball valve to seal off the by-pass passageway.

3. A free piston type parain scraper according to claim 2 additionally including means attached near the top of the tubing including a centrally located reset rod for contacting said ball and opening the ball valve in addition to moving said sleeve and ball-cage to its lower position whereby the by-pass passage for fluid flow is reopened and the scraper may fall downward within the tubing.

4. A free piston type paraflin scraper according to claim 2 wherein said wiping means comprises at least one pair of split rings having complementary tapering end walls for causing one of said rings to tend to open the other.

5. A free piston type parafln scraper according to claim 3 wherein said wiping means comprises at least one pair of split rings having complementary tapering end walls for causing one of said rings to tend to open the other.

References Cited UNITED STATES PATENTS 2,257,080 9/1941 Turner 166-170 2,661,024 12/1953 Knox 166-17() 2,785,757 3/1957 Middleton 166-170 3,329,211 7/1967 Roach 166-170 JAMES A. LEPPINK, Primary Examiner.

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